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| very high efficiency simplesync tm converter. features ? > 95% efficiency ? fixed frequency (adjustable) pwm ? voltage mode to ensure excellent stability & transient response ? low quiescent current in shutdown mode,15 a ? low battery flag ? output down to 2.0v ? overload protection ? demonstration boards available ? synchronous or non-synchronous operation ? cost effective solution ? n or p channel mosfets ? qsop16 package ? fixed 3.3, 5v and adjustable outputs ? programmable soft start applications ? high efficiency 5 to 3.3v converters up to 4a ? sub-notebook computers ? embedded processor power supply ? distributed power supply ? portable instruments ? local on card conversion ? gps systems description the zxrd1000 series provides complete control and protection functions for a high efficiency (> 95%) dc-dc converter solution. the choice of external mosfets allow the designer to size devices according to application. the zxrd1000 series uses advanced dc-dc converter techniques to provide synchronous drive capability, using innovative circuits that allow easy and cost effective implementation of shoot through protection. the zxrd1000 series can be used with an all n channel topology or a combination n & p channel topology. additional functionality includes shutdown control, a user adjustable low battery flag and simple adjustment of the fixed pwm switching frequency. the controller is available with fixed outputs of 5v or 3.3v and an adjustable (2.0 to 12v) output. 4.5-10v n1 zxm64n02x l1 15h c6 1f d1 zhcs1000 c3 330pf r3 3k r1 100k fx c1 1f 0.01r c7 22f d3 bat54 c10 1f r4 10k c8 2.2f 68f c4 1f c5 1f x2 680f r6 10k r5 6k cx2 0.01f cx1 0.022f rx 2k7 n2 zxm64n02x r2 680r d2 bat54 c11 1f c2 1f 3.3v 4a c9 1f 120f v cc c out v out r sense 13 bootstrap v in g nd g nd pwr lb set decoup r sense+ r sense - v fb c t lbf shdn v int delay comp v drive 2 1 7 8 16 15 3 4 6 5 10 14 11 9 c in low input flag shut down ic1 high efficiency simplesync ? ? ? ? pwm dc-dc controllers 1 zxrd1000 series issue 4 - october 2000
absolute maximum ratings input without bootstrap (p suffix) 20v input with bootstrap(n suffix) 10v bootstrap voltage 20v shutdown pin v in lb set pin v in r sense +, r sense - v in power dissipation 610mw (note 4) operating temperature -40 to +85c storage temperature -55 to +125c 2 electrical characteristics test conditions (unless otherwise stated) t amb =25c symbol parameter conditions min typ max unit v in(min) min. operating voltage no output device 4.5 v v fb (note 1) feedback voltage v in =5v,i fb =1ma 1.215 1.24 1.265 v 4.5 4 4 6 8 10 1214 1618 v in (v) 10 15 20 25 30 supply current (ma) 20 4681012141618 v in (v) 10 15 20 25 30 supply current v v in n phase device supply current (ma) 20 1nf 10nf timing capacitance 200 300 f osc v capacitance f osc (khz) 100 0 100pf vin=5v 10 20 30 40 50 r sense (m ) 2 3 4 current limit v r sense current limit (a) 5 1 0 0 v in =5v v out =3.3v -40 -20 0 20 40 60 80 100 temperature ( c) 5 10 15 20 v in (v) v in derating v temperature c g =2200pf supply current v v in p phase device typical characteristics issue 4 - october 2000 zxrd1000 series detailed description the zxrd1000 series can be configured to use either n or p channel mosfets to suit most applications. the most popular format, an all n channel synchronous solution gives the optimum efficiency. a feature of the zxrd1000 series solution is the unique method of generating the synchronous drive, called simplesync ? . most solutions use an additional output from the controller, inverted and delayed from the main switch drive. the zxrd1000 series solution uses a simple overwinding on the main choke (wound on the same core at no real cost penalty) plus a small ferrite bead . this means that the synchronous fet is only enhanced when the main fet is turned off. this reduces the ? blanking period ? required for shoot- through protection, increasing efficiency and allowing smaller catch diodes to be used, making the controller simpler and less costly by avoiding complex timing circuitry. included on chip are numerous functions that allow flexibility to suit most applications. the nominal switching frequency (200khz) can be adjusted by a simple timing capacitor, c3. a low battery detect circuit is also provided. off the shelf components are available from major manufacturers such as sumida to provide either a single winding inductor for non-synchronous applications or a coil with an over-winding for synchronous applications. the combination of these switching characteristics, innovative circuit design and excellent user flexibility, make the zxrd1000 series dc-dc solutions some of the smallest and most cost effective and electrically efficient currently available. using zetex ? s hdmos low r ds(on) devices, zxm64n02x for the main and synchronous switch, efficiency can peak at upto 95% and remains high over a wide range of operating currents. programmable soft start can also be adjusted via the capacitor, c7, in the compensation loop. what is simplesync tm ? conventional methods in the conventional approach to the synchronous dc-dc solution, much care has to be taken with the timing constraints between the main and synchronous switching devices. not only is this dependent upon individual mosfet gate thresholds (which vary from device to device within data sheet limits and over temperature), but it is also somewhat dependent upon magnetics, layout and other parasitics. this normally means that significant ? dead time ? has to be factored in to the design between the main and synchronous devices being turned off and on respectively. incorrect application of dead time constraints can potentially lead to catastrophic short circuit conditions between v in and g nd . for some battery operated systems this can not only damage mosfets, but also the battery itself. to realise correct ? dead time ? implementation takes complex circuitry and hence implies additional cost. the zetex method zetex has taken a different approach to solving these problems. by looking at the basic architecture of a synchronous converter, a novel approach using the main circuit inductor was developed. by taking the inverse waveform found at the input to the main inductor of a non-synchronous solution, a synchronous drive waveform can be generated that is always relative to the main drive waveform and inverted with a small delay. this waveform can be used to drive the synchronous switch which means no complex circuitry in the ic need be used to allow for shoot-through protection. implementation implementation was very easy and low cost. it simply meant peeling off a strand of the main i nductor winding and isolating it to form a coupled secondary winding. these are available as standard items referred to in the applications circuits parts list.the use of a small, surface mount, inexpensive ? square loop ? ferrite bead provides an excellent method of eliminating shoot-through due to variation in gate thresholds. the bead essentially acts as a high impedance for the few nano seconds that shoot-through would normally occur. it saturates very quickly as the mosfets attain steady state operation, reducing the bead impedance to virtually zero. benefits the net result is an innovative solution that gives additional benefits whilst lowering overall implementation costs. it is also a technique that can be simply omitted to make a non-synchronous controller, saving further cost, at the expense of a few efficiency points. 5 zxrd1000 series issue 4 - october 2000 functional block diagram pin descriptions ? see relevant applications section pin no. name description 1 bootstrap bootstrap circuit for generating gate drive 2v drive output to the gate drive circuit for main n/p channel switches 3pwrg nd power ground 4g nd signal ground 5c t timing capacitor sets oscillator frequency. ? 6v int internal bias circuit. decouple with 1 f ceramic capacitor 7r sense+ higher potential input to the current sense for current limit circuit 8r sense- lower potential input to the current sense for current limit circuit 9 shdn shutdown control. active low. 10 decoup optional short circuit and overload decoupling capacitor for increased accuracy 11 lbf low battery flag output. active low, open collector output 12 lb set low battery flag set. can be connected to v in if unused, or threshold set via potential divider. ? 13 v in input voltage 14 delay external r and c to set the desired cycle time for hiccup circuit. ? 15 comp compensation pin to allow for stability components and soft start. ? 16 v fb feedback voltage. this pin has a different function between fixed and adjustable controller options. the appropriate controller must be used for the fixed or adjustable solution. connect to v out for fixed output, or to potential divider for adjustable output. ? 6 issue 4 - october 2000 zxrd1000 series applications note: component names refer to designators shown in the application circuit diagrams. output capacitors output capacitors are a critical choice in the overall performance of the solution. they are required to filter the output and supply load transient current. they are also affected by the switching frequency, ripple current, di/dt and magnitude of transient load current. esr plays a key role in determining the value of capacitor to be used. combination of both high frequency, low value ceramic capacitors and low esr bulk storage capacitors optimised for switching applications provide the best response to load transients and ripple requirements. electrolytic capacitors with low esr are larger and more expensive so the ultimate choice is always a compromise between size, cost and performance. care must also be taken to ensure that for large capacitors, the esl of the leads does not become an issue. excellent low esr tantalum or electrolytic capacitors are available from sanyo os-con, avx, sprague and nichicon. the output capacitor will also affect loop stability, transient performance. the capacitor esr should preferably be of a similar value to the sense resistor. parallel devices may be required. i ripple ( rms ) = 0.29 v out ( v in ? v out ) l f v in where l= output filter inductance f= switching frequency for output voltage ripple it is necessary to know the peak ripple current which is given by: i pk ? pk = v out ( v in ? v out ) l f v in voltage ripple is then:- v ripple = i pk ? pk ? esr input capacitors the input capacitor is chosen for its rms current and voltage rating. the use of low esr electrolytic or tantalum capacitors is recommended. tantalum capacitors should have their voltage rating at 2v in (max), electrolytic at 1.4v in (max). i rms can be approximated by: i rms = i out ???????????? ? ( v out ( v in ? v out )) v in underspecification of this parameter can affect long term reliability. an additonal ceramic capacitor should be used to provide high frequency decoupling at v in. also note that the input capacitance esr is effectively in series with the input and hence contributes to efficiency losses related to i rms 2 * esr of the input capacitor. mosfet selection the zxrd1000 family can be configured in circuits where either n or p channel mosfets are employed as the main switch. if an n channel device is used, the corresponding n phase controller must be chosen. similarly, for p channel main switch a p phase controller must be used. the ordering information has a clear identifier to distinguish between n and p phase controllers. the mosfet selection is subject to thermal and gate drive considerations. care also has to be taken to allow for transition losses at high input voltages as well as r ds(on) losses for the main mosfet. it is recommended that a device with a drain source breakdown of at least 1.2 times the maximum v in should be used. for optimum efficiency , two n channel low r ds(on) devices are required. mosfets should be selected with the lowest r ds(on) consistent with the output current required. as a guide, for 3-4a output, <50m ? devices would be optimum, provided the devices are low gate threshold and low gate charge. typically look for devices that will be fully enhanced with 2.7v v gs for 4-5a capability. zetex offers a range of low r ds(on) logic level mosfets which are specifically designed with dc-dc power conversion in mind. packaging includes sot23, sot23-6 and msop8 options. ideal examples of optimum devices would be zetex zxm64n03x and zxm64n02x (n channel). contact your local zetex office or zetex web page for further information. 7 zxrd1000 series issue 4 - october 2000 applications (continued) inductor selection the inductor is one of the most critical components in the dc-dc circuit.there are numerous types of devices available from many suppliers. zetex has opted to specify off the shelf encapsulated surface mount components, as these represent the best compromise in terms of cost, size, performance and shielding. the simplesync tm technique uses a main inductor with an overwinding for the gate drive which is available as a standard part. however, for engineers who wish to design their own custom magnetics, this is a relatively simple and low cost construction technique. it is simply formed by terminating one of the multiple strands of litz type wire separately. it is still wound on the same core as the main winding and only has to handle enough current to charge the gate of the synchronous mosfet. the major benefit is circuit simplification and hence lower cost of the control ic. for non-synchronous operation, the overwinding is not required. the choice of core type also plays a key role. for optimum performance, a ? swinging choke ? is often preferred. this is one which exhibits an increase in inductance as load current decreases. this has the net effect of reducing circulating current at lighter load improving efficiency. there is normally a cost premium for this added benefit. for this reason the chokes specified are the more usual constant inductance type. peak current of the inductor should be rated to minimum 1.2i out (max) . to maximise efficiency, the winding resistance of the main inductor should be less than the main switch output on resistance. schottky diode selection depends on whether a synchronous or non-synchronous approach is taken. for the zxrd1000, the unique approach to the synchronous drive means minimal dead time and hence a small sot23 1a dc rated device will suffice, such as the zhcs1000 from zetex. the device is only designed to prevent the body diode of the synchronous mosfet from conducting during the initial switching transient until the mosfet takes over. the device should be connected as close as possible to the source terminals of the main mosfet. for non-synchronous applications , the schottky diode must be selected to allow for the worst case conditions, when v in is at its highest and v out is lowest (short circuit conditions for example). under these conditions the device must handle peak current at close to 100% duty cycle. frequency adjustment the nominal running frequency of the controller is set to 200khz in the applications shown. this can be adjusted over the range 50khz to 300khz by changing the value of capacitor on the c t pin. a low cost ceramic capacitor can be used. frequency = 60000/c3 (pf) frequency v temperature is given in the typical characteristics. output voltage adjustment the zxrd1000 is available as either a fixed 5v, 3.3v or adjustable output. on fixed output versions, the v fb pin should be connected to the output. adjustable operation requires a resistive divider connected as follows: the value of the output voltage is determined by the equation v out = v fb ( 1 + r a r b ) v fb = 1.24v note: the adjustable circuit is shown in the following transient optimisation section. it is also used in the evaluation pcb. in both these circuits r a is assigned the label r6 and r b the label r5. values of resistor should be between 1k and 20k to guarantee operation. output voltage can be adjusted in the range 2v to 12v for non-synchronous applications. for synchronous applications, the minimum v out is set by the v gs threshold required for the synchronous mosfet, as the swing in the gate using the simplesync tm technique is approximately v out . 8 issue 4 - october 2000 zxrd1000 series applications (continued) low battery flag the low battery flag threshold can be set by the user to trip at a level determined by the equation: v lbset = 1.25 ( 1 + r c r d ) r d is recommended to be 10k where r c and r d are connected as follows: hysteresis is typically 20mv at the lb set pin. current limit a current limit is set by the low value resistor in the output path, r sense . since the resistor is only used for overload current limit, it does not need to be accurate and can hence be a low cost device. the value of the current limit is set by using the equation: i lim ( a ) = 50 ( mv ) r sense ( m ? ) a graph of current limit v r sense is shown in the typical characteristics. this should assist in the selection of r sense appropriate to application. if desired, r sense can also be on the input supply side. when used on the input side r sense should be in series with the upper output device (i.e. in series with the drain or source in n and p channel solutions respectively).typically in this configuration r sense will be 20m . hiccup time constant the hiccup circuit (at the ? delay ? pin) provides overload protection for the solution. the threshold of the hiccup mode is determined by the value of r sense, when >50mv is developed across the sense resistor, the hiccup circuit is triggered, inhibiting the device. it will stay in this state depending upon the time constant of the resistor and capacitor connected at the ? delay ? pin. in order to keep the dissipation down under overload conditions it is recommended the circuit be off for approximately 100ms. if for other application reasons this is too long an off period, this can be reduced at least by 10:1, care needs to be taken that any increased dissipation in the external mosfet is still acceptable. the resistor capacitor combination r1,c1 recommended in the applications circuits provides a delay of 100ms. soft start & loop stability soft start is determined by the time constant of the capacitor and resistor c7 and r3. typically a good starting point is c7 = 22 f and r3 = 24k for fixed voltage variants. for fully adjustable variants see optimising for transient response later in the applications section. this network also helps provide good loop stability. low quiescent shutdown shutdown control is provided via the shdn pin, putting the device in to a low quiescent sleep mode. in some circumstances where rapid sequencing of v cc can occur (when v cc is turned off and back on) and v cc has a very rapid rise time (100-200ms) timing conflicts can occur. 9 zxrd1000 series issue 4 - october 2000 10 optimising for transient response. transient response is important in applications where the load current increases and decreases rapidly. to optimise the system for good transient response certain criteria have to be observed. the optimum solution using the zxrd series uses the adjustable n phase controller in synchronous mode as represented in the diagram opposite. the external networks for this solution require the use of the adjustable controller option. by using standard ? bulk ? capacitors in parallel with a single os-con capacitor significant performance versus cost advantage can be given in this application. the low esr of the os-con capacitor provides competitive output voltage ripple at low capacitance values. the ? bulk ? capacitors aid transient response. however, the low esr of the os-con capacitor can cause instability within the system. to maintain stability an rc network (r x , c x 1) has to be implemented. furthermore, a capacitor in parallel with r6 (c x 2) is required to optimise transient response. to do this the appropriate adjustable zxrd must be used because the input to the internal error amplifier (pin 16) has to be accessed. the adjustable device differs from fixed controller versions in this respect. this combined with a frequency compensation adjustment gives an optimised solution for excellent transient response. layout issues layout is critical for the circuit to function in the most efficient manner in terms of electrical efficiency, thermal considerations and noise. the following guidelines should be observed: a 2.2 f (c8) decoupling capacitor should be as close as possible to the drive mosfets and d1 anode. this capacitor is effectively connected across v in and g nd but should be as close as possible to the appropriate components in either n or p, synchronous or non-synchronous configurations. furthermore the g nd connection of the synchronous mosfet/d1 and output capacitors should be close together and use either a ground plane or at the very least a low inductance pcb track. for the standard application circuits, a gerber file can be made available for the layout which uses the materials as listed in the bill of materials table for the reference designs. reference designs. in the following section reference circuits are shown for the zxrd series in both synchronous and non-synchronous modes. these are shown for each of the n and p phase controllers. in each case efficiency graphs are shown for the appropriate configuration using 3.3v and 5v zxrd devices. the bom is then shown for the design. additional and alternative components are shown with a ? * ? . these refer to modifications to the design to optimise for transient response. optimisation is reached using the adjustable version of either n or p phase controller device. issue 4 - october 2000 zxrd1000 series 4.5-10v n1 zxm64n02x l1 15h c6 1f d1 zhcs1000 c3 330pf r3 3k r1 100k fx c1 1f 0.01r c7 22f d3 bat54 c10 1f r4 10k c8 2.2f 68f c4 1f c5 1f x2 680f r6 10k r5 6k cx2 0.01f cx1 0.022f rx 2k7 n2 zxm64n02x r2 680r d2 bat54 c11 1f c2 1f 3.3v 4a c9 1f 120f v cc c out v out r sense 13 bootstrap v in g nd g nd pwr lb set decoup r sense+ r sense - v fb c t lbf shdn v int delay comp v drive 2 1 7 8 16 15 3 4 6 5 10 14 11 9 c in low input flag shut down ic1 11 optimised transient response, 4.5v-10v input, 3v/4a output, n phase adjustable, simplesync tm converter 200khz. zxrd1000 series issue 4 - october 2000 n2 4.5-10v n1 l1 d2 c6 c11 d1 c3 c2 r3 r1 r2 fx 3.3v 4a c1 c9 c7 d3 c10 r4 c8 c4 c5 ic1 c in v cc low input flag shut down c out v out r sense 13 bootstrap v in g nd g nd pwr lb set decoup r sense+ r sense - v f b c t lbf shdn v int delay comp v drive 2 1 7 8 16 15 3 4 6 5 10 14 11 9 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 efficiency v i v =5.0v. out out i (a) out v =7v in v =10v in efficiency (%) 12 4.5v -10vinput, 3.3v/4a output, n phase, high efficiency simplesync tm converter 200khz zxrd1033nq16 zxrd1050nq16 issue 4 - october 2000 zxrd1000 series 13 ref value part number manufacturer comments ic1 zxrd1033nq16 zetex qsop16 controller ic n1 v in >7v v in <7v n2 zxm64n03x zxm64n02x zxm64n02x zetex msop8 low r ds(on) n mosfet 30v v ds 20v v ds 20v v ds d1 1a 0.5v v f zhcs1000 zetex sot23 schottky diode 1a d2 10ma 0.4v v f bat54 zetex sot23 schottky diode d3 10ma 0.4v v f bat54 zetex sot23 schottky diode r1 100k wcr0805-100k welwyn/irc 0805 size r2 680 wcr0805-680 welwyn/irc 0805 size r3 24k wcr0805-24k welwyn/irc 0805 size *r3 3k wcr0805-3k welwyn/irc 0805 size r4 10k wcr0805-10k welwyn/irc 0805 size *rx 2.7k wcr0805-2.7k welwyn/irc 0805 size r sense 0.01 lr1206r010 welwyn/irc current limit sense resistor c in or or 68 f 68 f 68 f tpsd68m016r0150 20sa68m 20sv68m avx sanyo os-con sanyo os-con 68 f 16v ? e ? low esr 68 f 20v pth low esr 68 f 20v smt low esr c out or or 470 f *150 f *120 f tpse477m010r0200 6sa150m 6sv120m avx sanyo os-con sanyo os-con 470 f 10v ? e ? low esr 150 f 6v pth low esr 120 f 6v smt low esr c out 680 f x 2 6cv680gx sanyo 680 f 6v smt bulk capacitor c1 1 fgeneric 1 f,10v.x7r dielectric c2 1 fgeneric 1 f,4v.x7r dielectric c3 330pf generic 330pf,4v.x7r dielectric c4 1 fgeneric 1 f,10v.x7r dielectric c5 1 fgeneric 1 f,10v.x7r dielectric c6 1 fgeneric 1 f,4v.x7r dielectric c7 22 fgeneric 22 f,4v.x7r dielectric c8 2.2 fgeneric 2.2 f,10v.x7r dielectric c9 1 fgeneric 1 f,10v.x7r dielectric c10 1 fgeneric 1 f,10v.x7r dielectric c11 1 fgeneric 1 f,10v.x7r dielectric *cx1 0.022 fgeneric 0.022 f,4v.x7r dielectric *cx2 10nf generic 10nf,10v.x7r dielectric l1 or 15 h 10 h cdrh127b-owz9 6001 sumida smt c&d technologies (ncl) low profile smt low profile smt fx 2785044447 fairrite smt ferrite bead * see optimising for transient response section zxrd1000 series issue 4 - october 2000 14 low input flag 4.5-10.0v shut down n1 c6 c11 d1 bootstrap v in g nd g nd pwr lb set decoup r sense+ r sense - v f b c t lbf shdn v int delay comp v drive c3 c2 r3 r1 r2 3.3v 4a c1 13 2 1 7 8 16 15 3 4 6 5 10 14 11 9 r sense c9 c7 c5 l1 ic1 c10 d3 r4 d2 c out v out c in c8 c4 v cc c out 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 efficiency v i v =3.3v. out out i (a) out v =5v in v =10v in efficiency (%) 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 efficiency v i v=5v. out out i(a) out v =7v in v =10v in efficiency (%) 4.5v -10vinput, 3.3v/4a output, n phase, high efficiency non-synchronous step down converter 200khz zxrd1033nq16 zxrd1050nq16 issue 4 - october 2000 zxrd1000 series 15 ref value part number manufacturer comments ic1 zxrd1033nq16 zetex qsop16 controller ic n1 v in >7v v in <7v zxm64n03x zxm64n02x zetex msop8 low r ds(on) n mosfet 30v v ds 20v v ds d1 5a 0.5v v f 50wq04fn zetex schottky diode 5a d2 10ma 0.4v v f bat54 zetex sot23 schottky diode d3 10ma 0.4v v f bat54 zetex sot23 schottky diode r1 100k wcr0805-100k welwyn/irc 0805 size r2 680 wcr0805-680 welwyn/irc 0805 size r3 24k wcr0805-24k welwyn/irc 0805 size *r3 3k wcr0805-3k welwyn/irc 0805 size r4 10k wcr0805-10k welwyn/irc 0805 size *rx 2.7k wcr0805-2.7k welwyn/irc 0805 size r sense 0.01 lr1206r010 welwyn/irc current limit sense resistor c in or or 68 f 68 f 68 f tpsc68m02r0150 20sa68m 20sv68m avx sanyo os-con sanyo os-con 68 f 25v ? e ? low esr 68 f 20v pth low esr 68 f 20v smt low esr c out or or 470 f *150 f *120 f tpse477m010r0200 6sa150m 6sv120m avx sanyo os-con sanyo os-con 470 f 10v ? e ? low esr 150 f 6v pth low esr 120 f 6v smt low esr c out 680 f x 2 6cv680gx sanyo 680 f 6v smt bulk capacitor c1 1 fgeneric 1 f,10v.x7r dielectric c2 1 fgeneric 1 f,4v.x7r dielectric c3 330pf generic 330pf,4v.x7r dielectric c4 1 fgeneric 1 f,10v.x7r dielectric c5 1 fgeneric 1 f,10v.x7r dielectric c6 1 fgeneric 1 f,4v.x7r dielectric c7 22 fgeneric 22 f,4v.x7r dielectric c8 2.2 fgeneric 2.2 f,10v.x7r dielectric c9 1 fgeneric 1 f,10v.x7r dielectric c10 1 fgeneric 1 f,10v.x7r dielectric c11 1 fgeneric 1 f,10v.x7r dielectric *cx1 0.022 fgeneric 0.022 f,4v.x7r dielectric *cx2 10nf generic 10nf,10v.x7r dielectric l1 or 15 h 15 h cdrh127-150mc dp5022p-153 sumida coilcraft low profile smt low profile smt * see optimising for transient response section zxrd1000 series issue 4 - october 2000 16 5v-18v c6 d1 c3 c2 r3 r1 r2 5.0v 3a c1 c9 c7 c5 l1 p1 n1 c8 fx c4 13 bootstrap v in g nd g nd pwr lb set decoup r sense+ r sense - v f b c t lbf shdn v int delay comp v drive 2 1 7 8 16 15 3 4 6 5 10 14 11 9 c in v cc low input flag shut down c out v out r sense ic1 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 efficiency v i v=5v. out out i(a) out v =7v in v =12v in efficiency (%) 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 efficiency v i v =3.3v. out out i (a) out v =5v in v =12v in efficiency (%) 5v -18v input, 5v/3a output, p phase, high efficiency simplesync tm converter 200khz zxrd1033pq16 ZXRD1050PQ16 issue 4 - october 2000 zxrd1000 series 17 ref value part number manufacturer comments ic1 ZXRD1050PQ16 zetex qsop16 controller ic p1 v in >12v v in <12v zxm64p03x zxm64p02x zetex msop8 low r ds(on) p mosfet 30v v ds 20v v ds n1 zxm64no3x zetex msop8 low r ds(on) mosfet d1 1a 0.5v v f zhcs1000 zetex schottky diode 1a r1 100k wcr0805-100k welwyn/irc 0805 size r2 680 wcr0805-680 welwyn/irc 0805 size r3 24k wcr0805-24k welwyn/irc 0805 size *r3 3k wcr0805-3k welwyn/irc 0805 size *rx 2.7k wcr0805-2.7k welwyn/irc 0805 size r sense 0.015 lr1206r015 welwyn/irc current limit sense resistor c in or or 68 f 68 f 68 f tpsv686m025r0150 20sa68m 20sv68m avx sanyo os-con sanyo os-con 68 f 25v ? e ? low esr 68 f 20v pth low esr 68 f 20v smt low esr c out or or 470 f *150 f *120 f tpse477m010r0200 6sa150m 6sv120m avx sanyo os-con sanyo os-con 470 f 10v ? e ? low esr 150 f 6v pth low esr 120 f 6v smt low esr c out 680 f x 2 6cv680gx sanyo 680 f 6v smt bulk capacitor c1 1 fgeneric 1 f,20v.x7r dielectric c2 1 fgeneric 1 f,4v.x7r dielectric c3 330pf generic 330pf,4v.x7r dielectric c4 1 fgeneric 1 f,20v.x7r dielectric c5 1 fgeneric 1 f,20v.x7r dielectric c6 1 fgeneric 1 f,4v.x7r dielectric c7 22 fgeneric 22 f,4v.x7r dielectric c8 2.2 fgeneric 2.2 f,20v.x7r dielectric c9 1 fgeneric 1 f,20v.x7r dielectric *cx1 0.022 fgeneric 0.022 f,4v.x7r dielectric *cx2 10nf generic 10nf,20v.x7r dielectric l1 or 15 h 10 h cdrh127b-owz9 6001 sumida c&d technologies (ncl) low profile smt low profile smt fx 2785044447 fairrite smt ferrite bead * see optimising for transient response section zxrd1000 series issue 4 - october 2000 c in v cc low input flag 5.0-18v shut down c6 d1 c3 c2 r3 r1 r2 5.0v 3a c1 c9 c7 c5 l1 p1 c8 c4 13 bootstrap v in g nd g nd pwr lb set decoup r sense+ r sense - v f b c t lbf shdn v int delay comp v drive 2 1 7 8 16 15 3 4 6 5 10 14 11 9 c out v out r sense ic1 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 efficiency v i v =3.3v. out out i (a) out v =5v in v =12v in efficiency (%) 5v -18v input, 5v/3a output, p phase, high efficiency non-synchronous step down converter 200khz 18 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 efficiency v i v =5v. out out i (a) out v =7v in v =12v in efficiency (%) zxrd1033pq16 ZXRD1050PQ16 issue 4 - october 2000 zxrd1000 series 19 ref value part number manufacturer comments ic1 ZXRD1050PQ16 zetex qsop16 controller ic p1 v in >12v v in <12v zxm64p03x zxm64p02x zetex msop8 low r ds(on) p mosfet 30v v ds 20v v ds d1 5a 0.5v v f 50wq04fn ir schottky diode 5a r1 100k wcr0805-100k welwyn/irc 0805 size r2 680 wcr0805-680 welwyn/irc 0805 size r3 24k wcr0805-24k welwyn/irc 0805 size *r3 3k wcr0805-3k welwyn/irc 0805 size *rx 2.7k wcr0805-2.7k welwyn/irc 0805 size r sense 0.015 lr1206r015 welwyn/irc current limit sense resistor c in or or 68 f 68 f 68 f tpsv686m025r0150 20sa68m 20sv68m avx sanyo os-con sanyo os-con 68 f 25v ? e ? low esr 68 f 20v pth low esr 68 f 20v smt low esr c out or or 470 f *150 f *120 f tpse477m010r0200 6sa150m 6sv120m avx sanyo os-con sanyo os-con 470 f 10v ? e ? low esr 150 f 6v pth low esr 120 f 6v smt low esr c out 680 f x 2 6cv680gx sanyo 680 f 6v smt bulk capacitor c1 1 fgeneric 1 f,20v.x7r dielectric c2 1 fgeneric 1 f,4v.x7r dielectric c3 330pf generic 330pf,4v.x7r dielectric c4 1 fgeneric 1 f,20v.x7r dielectric c5 1 fgeneric 1 f,20v.x7r dielectric c6 1 fgeneric 1 f,4v.x7r dielectric c7 22 fgeneric 22 f,4v.x7r dielectric c8 2.2 fgeneric 2.2 f,20v.x7r dielectric c9 1 fgeneric 1 f,20v.x7r dielectric *cx1 0.022 fgeneric 0.022 f,4v.x7r dielectric *cx2 10nf generic 10nf,20v.x7r dielectric l1 15 h 15 h cdrh127-150mc d05022p-153 sumida smt coilcraft low profile smt low profile smt * see optimising for transient response section zxrd1000 series issue 4 - october 2000 20 designing with the zxrd and dynamic performance this section refers to the reference design for the 3.3v, 4a output n channel synchronous converter. this is as shown previously in the optimising for transient response section of the applications information (page 10). this circuit is also representative of the zxrd evaluation board (see ordering information). the zxrd series has been designed to give the best in terms of all round flexibility allowing engineers to either use the reference design as is, or to tailor the design to the individual requirements. this section demonstrates the performance features of the zxrd series and its associated components. efficiency efficiency is often quoted as one of the key parameters of a dc-dc converter. not only does it give an instantaneous idea of heat dissipation, but also an idea as to the extent battery life can be extended in say portable applications. fig.1 shows the efficiency of the standard application circuit. efficiency vs output current is shown for the 5 to 3.3v configuration. startup startup is always important in dc-dc converter applications. magnetics have large inrush current requirements. for higher current applications using large input and output capacitors the startup current can be quite significant. this can cause several problems. in many applications the power supply to the dc-dc converter can be affected. particularly in battery powered applications, trying to take large steps in load current out of the supply can result in either current limitation (by the internal impedance of the battery), or it can actually damage the battery. for the converter itself, large changes in load current can result in false triggering of the rsense circuit. this could result in device hiccup (see applications section). the zxrd programmable soft start function eliminates both these problems. this is very clear to see in operation if the main switching waveforms are examined. the soft start is programmed by the combination of resistor and capacitor r3 and c7. as a recommendation, r3 and c7 are set to 3k and 22 f respectively, which limits the peak startup current appropriately in the reference circuit. fig.2 shows the startup waveforms. v in and v out are plotted against time efficiency v i v =3.3v. out out 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 i (a) out v =5v in efficiency (%) fig.1. 5-3.3v efficiency to 4a issue 4 - october 2000 zxrd1000 series simplesync tm and shoot-through steady state operation under constant load gives an excellent indication of the zxrd series performance and also demonstrates how well simplesync tm works. the simplesync tm technique drives the synchronous mosfet gate using the overwinding on the main inductor. it also uses the high speed suppression characteristics of the ferrite bead to prevent shoot through currents. fig.3 shows the gate waveforms for the main and synchronous mosfet devices (zetex zxm64n02x). fig3. main & synchronous gate waveform s output voltage ripple output voltage ripple is shown in fig.4 and fig. 5 for load currents of 0.5a and 4a respectively. output voltage ripple will be dependant, to a very large extent, on the output capacitor esr. (see applications section for ripple calculation). fig.4 0.5a main & v out waveforms fig.5 4a main & v out waveforms fig.2. startup waveform for 3.3v output . 21 zxrd1000 series issue 4 - october 2000 line regulation variation in input voltage for both these conditions (0.5a and 4a output) shows the excellent line regulation the zxrd. fig.6 shows that with 0.5a and 4a output currents, applying an increase in input voltage from 5v to 10v , results in only small changes in output regulation. fig.6a line regulation 0.5a load fig.6b line regulation 4a load transient response transient response to changes in load is becoming an increasingly critical feature of many converter circuits. many high speed processors make very large step changes in their load requirements, at the same time as having more stringent specifications in terms of overshoot and undershoot. fig.7 demonstrates the excellent load transient performance of the zxrd series. a step change using an electronic load from 1a to 3a is shown with corresponding output transient performance. fig.7 output transient response non-synchronous applications one of the key features of the zxrd series, when combined with the simplesync tm technique, is the flexibility in allowing engineers to choose either a synchronous or non-synchronous architecture. making the design non-synchronous by removing mosfet n2 (the synchronous device), replacing the zhcs1000 with a high current diode (50wq04fn) and using a 2 terminal inductor, such as the sumida cdrh127-150mc, decreases cost slightly at the expense of a few efficiency points. fig.8 shows the effect on the efficiency of the 5 to 3.3v 4a application when the design is made non-synchronous. 22 issue 4 - october 2000 zxrd1000 series using ? p ? channel devices (no bootstrap) all the preceeding examples utilise n channel mosfet devices and a bootstrap circuit to provide full enhancement to the high side device. these circuits have a maximum input voltage of 10v. for applications requiring a higher input voltage, using p channel devices for the main mosfet will allow up to 18v operation. typically this may be in a 12v to 5v converter circuit. if the same package size mosfet devices are used, it is likely a higher on resistance will be encountered, with the result that efficiency will decline slightly. fig 9 shows the efficiency plot for a p phase synchronous 5v converter based on the ZXRD1050PQ16. the figure charts efficiency v output current at 12v input and 7v input. 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 efficiency v i v =3.3v. out out i(a) out v =5v in efficiency (%) fig.9 ? p ? channel device efficiency (synchronous) 50 55 60 65 70 75 80 85 90 95 100 0.1 1 10 efficiency v i v =5v. out out i (a) out v =7v in v =12v in efficiency (%) 23 fig.8 efficiency for non-synchronous 5-3.3v conversion zxrd1000 series issue 4 - october 2000 24 issue 4 - october 2000 n channel devices offer high efficiency performance for switching applications. this family of mosfets from zetex offers a combination of low on-resistance and low gate charge, providing optimum performance and high efficiency for switching applications such as dc - dc conversion. on resistance is low across the family, from only 40m ? (max) for the zxm64n02x part up to 180m ? (max) for the zxm61n02f. this means that on-state losses are minimised, improving efficiency in low frequency drive applications. threshold voltages of 0.7v and 1v minimum allow the mosfets to be driven from low voltage sources. to minimise switching losses, and hence increase the efficiency of high frequency operation, gate charge (qg) is small. the maximum qg varies from 3.4nc to 16nc depending on which device is chosen. c rss (miller capacitance) is also low, e.g. typically 30pf for the zxm6203e6 device. this results in better efficiency in high frequency applications. p channel mosfets excel in load switching applications. the p-channel mosfets offer highly efficient performance for low voltage load switching applications. this helps increase battery life in portable equipment. minimum threshold voltage is low, only 0.7v or 1v, enabling the mosfets to provide optimum performance from a low voltage source. to ensure the device suitability for low voltage applications, drain to source voltage is specified at 20v or 30v. to minimise on-state losses, and improve efficiency in in low frequency drive applications, the on-resistance (r ds(on) ) is low across the range. for example, the zxm64p03x has an r ds(on) of only 100m ? at a gate to source voltage of 4.5v. gate source charge is also low, easing requirements for the gate driver. maximum values range from 0.62nc for the zxm61p03f, up to 9nc for the zxm64p03x. small outline surface mount packaging the products have been designed to optimise the performance of a range of packages. the parts are offered in sot23, sot23-6 and msop8 packages. the msop8 enables single or dual devices to be offered. the msop8 is also half the size of competitive so8 devices and 20% smaller than tssop8 alternatives. product performance the following performance characteristics show the capabilities of the zxm64n02x. this device is recommended for use with certain configurations of the zxrd dcdc controller circuit. zxcm6 series low voltage mosfets unique structure gives optimum performance for switching applications. zxrd1000 series 25 electrical characteristics (at t amb = 25 c unless otherwise stated). parameter symbol min. typ. max. unit conditions. static drain-source breakdown voltage v (br)dss 20 v i d =250 a, v gs =0v zero gate voltage drain current i dss 1 a v ds =20v, v gs =0v gate-body leakage i gss 100 na v gs = 12v, v ds =0v gate-source threshold voltage v gs(th) 0.7 v i d =250 a, v ds = v gs static drain-source on-state resistance (1) r ds(on) 0.040 0.050 ? ? v gs =4.5v, i d =3.8a v gs =2.7v, i d =1.9a forward transconductance (3) g fs 6.1 s v ds =10v,i d =1.9a dynamic (3) input capacitance c iss 1100 pf v ds =15 v, v gs =0v, f=1mhz output capacitance c oss 350 pf reverse transfer capacitance c rss 100 pf switching(2) (3) turn-on delay time t d(on) 5.7 ns v dd =10v, i d =3.8a r g =6.2 ? , r d =2.6 ? (refer to test circuit) rise time t r 9.6 ns turn-off delay time t d(off) 28.3 ns fall time t f 11.6 ns total gate charge q g 16 nc v ds =16v,v gs =4.5v , i d =3.8a (refer to test circuit) gate-source charge q gs 3.5 nc gate drain charge q gd 5.4 nc source-drain diode diode forward voltage (1) v sd 0.95 v t j =25 c, i s =3.8a, v gs =0v reverse recovery time (3) t rr 23.7 ns t j =25 c, i f =3.8a, di/dt= 100a/ s reverse recovery charge(3) q rr 13.3 nc (1) measured under pulsed conditions. width=300 s. duty cycle 2% . (2) switching characteristics are independent of operating junction temperature. (3) for design aid only, not subject to production testing. performance characterisation of zxm64n02x zxrd1000 series issue 4 - october 2000 208221 b8066 germany asia usa uk zetex zetex gmbh munich zetex asia hong kong zetex inc long island ny zetex plc chadderton, oldham (49) 894549490 (852) 2610 0611 (1) 631 543 7100 (44) 161 622 4444 http://www.zetex.com sumida sumida electric hk (852) 2880 6688 sumida electric usa (chicago head office) ole wolf electronics ltd. taiwan sumida electric (886) 2762 2177 (1) 847 956-0666 (44) 1525 290755 http://www.japanlink.com/sumida/ fairrite schaffner electronik gmbh (49) 72156910 fair rite asia pte ltd singapore (65) 281 1969 japan/korea (81) 332255055 fairrite products corp (1) 914 895 2055 schaffner emc ltd (44) 118 977 0070 avx avx asia singapore (65) 258 2833 avx usa (1) 843 448 9411 avx uk (44) 1252 770000 http://www.avxcorp.com welwyn, irc welwyn electronics gmbh (49)871 973760 ttc group plc singapore (65) 536 51667 irc inc (1) 512 992 7900 welwyn components ltd (44) 1670 822181 http://welwyn-tt.co.uk coilcraft coilcraft inc (1) 847 639 6400 coilcraft europe (44) 1236 730595 http://www.coilcraft.com sanyo electronic comp. (os-con) sanyo europe munich (49) 89 457693 16 sanyo electronics ltd. hong kong (852) 21936888 singapore (65) 281 3226 japan (81) 720 70 6306 sanyo electronics ltd. forrest city, ar 870 633 5030 san diego, ca 619 661 6835 rochelle pk, nj 201 843 8100 semicon uk ltd (44) 1279 422224 http://www.sanyovideo.com c & d technologies (ncl) contact c & d technologies (ncl) uk c & d technologies guangzhou, guangdong, prc (86) 208221 8066 c & d technologies (ncl) 5816 creedmoor road, raleigh north carolina 27612 (1) 919 571 9405 c & d technologies (ncl) tanners drive blakelands north milton keynes mk14 5bu (44) 1908 615232 http://www.dc-dc.com 26 issue 4 - october 2000 zxrd1000 series 5 6 7 8 4 3 2 1 bootstrap v drive pwrg nd g nd c t v int r sense + r sense - shdn v fb delay v in comp decoup lbf lb set 9 10 11 12 13 14 15 16 pin no.1 identification recess for pin 1 a b d j e f g c k dim millimetres inches min max min max a 4.80 4.98 0.189 0.196 b 0.635 0.025 nom c 0.177 0.267 0.007 0.011 d 0.20 0.30 0.008 0.012 e 3.81 3.99 0.15 0.157 f 1.35 1.75 0.053 0.069 g 0.10 0.25 0.004 0.01 j 5.79 6.20 0.228 0.244 k0 8 0 8 connection diagram package dimensions 27 note: connection diagram is the same for n and p phase, adjustable and fixed controllers. the v fb pin has a different function between adjustable and fixed versions. zxrd1000 series issue 4 - october 2000 28 zetex plc. fields new road, chadderton, oldham, ol9-8np, united kingdom. telephone: (44)161 622 4422 (sales), (44)161 622 4444 (general enquiries) fax: (44)161 622 4420 zetex gmbh zetex inc. zetex (asia) ltd. these are supported by streitfeldstra?e 19 47 mall drive, unit 4 3701-04 metroplaza, tower 1 agents and distributors in d-81673 mnchen commack ny 11725 hing fong road, major countries world-wide germany usa kwai fong, hong kong ? zetex plc 2001 telefon: (49) 89 45 49 49 0 telephone: (631) 543-7100 telephone:(852) 26100 611 fax: (49) 89 45 49 49 49 fax: (631) 864-7630 fax: (852) 24250 494 http://www.zetex.com this publication is issued to provide outline information only which (unless agreed by the company in writing) may not be used, applied or reproduced for any purpose or form part of any order or contract or be regarded as a representation relating to the products or services concerned . the company reserves the right to alter without notice the specification, design, price or conditions of supply of any product or service. ordering information device description t&r suffix partmarking zxrd1033nq16 3.3v fixed controller n main switch ta, tc zxrd1033n zxrd1050nq16 5.0v fixed controller n main switch ta, tc zxrd1050n zxrd100anq16 adjustable controller n main switch ta, tc zxrd100an zxrd1033pq16 3.3v fixed controller p main switch ta, tc zxrd1033p ZXRD1050PQ16 5.0v fixed controller p main switch ta, tc zxrd1050p zxrd100apq16 adjustable controller p main switch ta, tc zxrd100ap ? n main switch ? indicates controller for use with n channel main switch element. ? p main switch ? indicates controller for use with p channel main switch element. ta= tape and reel quantity of 500 tc= tape and reel quantity of 2500 demonstration boards these can be requested through your local zetex office or representative. these boards can be tailored to your specific needs. if you would like to obtain a demo board then a request form is available to help determine your exact requirement. issue 4 - october 2000 zxrd1000 series |
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