View RC5037MT_7160430.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

www.fairchildsemi.com rev. 1.0.1 features ? high power switch-mode dc-dc controller can provide in excess of 13a ? output voltage adjustable from 1.5v to 3.6v ? 85% ef?ciency ? cumulative accuracy < 3% over line, load, and temperature variations ? overvoltage and short circuit protection ? built-in soft start applications ? i/o and agp power for desktop computers ? high ef?ciency power for asics ? high ef?ciency power for dsps ? adjustable step-down power supplies description the rc5037 is a high power, switch-mode dc-dc controller that provides ef?cient power for all low-voltage applications. this controller has a built-in soft start feature which offers system protection during power-up by reducing both inrush current and output overshoot. when combined with the appropriate external circuitry, the rc5037 can deliver load currents as high as 13a at ef?ciencies as high as 88%. the rc5037 can generate output voltages from 1.5v up to 3.6v using external resistors. the rc5037 is designed to operate in a constant on-time control mode under all load conditions. its accurate low tc reference eliminates the need for precision external compo- nents in order to achieve the tight tolerance voltage regula- tion required by many applications. short circuit current protection is provided through the use of a current sense resistor, while overvoltage protection is provided internally. block diagram feedback control oscillator digital logic rc5037 1.5v reference vout +12v 5v +5v 1 2 4 3 8 7 6 5 rc5037 adjustable switching regulator controller
rc5037 product specification 2 pin assignments absolute maximum ratings note: 1. functional operation under any of these conditions is not implied. performance is guaranteed only if operating conditions are not exceeded. operating conditions pin descriptions pin name pin number pin function description cext 1 external capacitor. a 180pf capacitor is connected to this pin as part of the constant on- time pulse width circuit. careful layout of this pin is critical to system performance. see applications information for details. vcca 2 analog v cc . power supply for regulator control circuitry and voltage reference. connect to system 5v supply and decouple to ground with 0.1f ceramic capacitor. ifbh 3 high side current feedback. pins 3 and 4 are used as the inputs for the current feedback control loop and as the short circuit current sense points. careful layout of the traces from these pins to the current sense resistor is critical for optimal performance of the short circuit protection scheme. see applications information for details. ifbl 4 low side current feedback. see applications information for details. vfb 5 voltage feedback. using two external resistors, this pin sets the output voltage level for the switching regulator. gndp 6 power ground. connect to a low impedance ground. see application information for details. drv 7 mosfet driver output. connect this pin to the gate of the n-channel mosfet q1 as shown in figure 12. the trace from this pin to the mosfet gate should be kept as short as possible (less than 0.5"). see applications information for details. vccp 8 power v cc . power supply for drv output driver. connect to system 12v supply with r-c filter shown in figure 12. see applications information for details. supply voltages, vcca 7v supply voltages, vccp 13v junction temperature, t j +150c storage temperature, t s -65 to +150c lead soldering temperature, 10 seconds 300c thermal resistance junction-to-ambient, q ja 163c/w parameter conditions min. typ. max. units switching regulator supply, vcca 4.75 5 5.25 v ambient operating temperature, t a 070c gate drive supply, vccp 9.5 12 12.6 v cext vcca ifbh vccp drv gndp 1 2 3 8 7 6 ifbl vfb rc5037 45
product specification rc5037 3 electrical characteristics (vcca = 5v, vccp = 12v, t a = 25 c using circuit of figure 1, unless otherwise noted) the ? denotes speci?cations which apply over the full ambient operating temperature range. notes: 1. total dc accuracy includes setpoint accuracy, temperature drift, line and load regulation. 2. the on-time pulse width of the oscillator is set via external capacitor c ext . parameter conditions min. typ. max. units output voltage 1.5 3.6 v output temperature drift t a = 0?cC70?c 40 ppm/?c line regulation vcca = 4.75 to 5.25v, i load = 13a 3 5 mv load regulation i load = 0 to 5a or 5a to 13a 30 43 mv v out psrr vcca = 4.75 to 5.25v 60 db output ripple, peak-peak 20mhz bw, i load = 13a 15 mv total dc accuracy 1 55 100 mv efficiency i load = 5a 80 85 % output driver current open loop 0.5 a short circuit threshold voltage 70 90 100 mv on time pulse width 2 c ext = 180pf 3.5 s vcca supply current independent of load 515ma vccp supply current i load = 13a 20 25 ma
rc5037 product specification 4 typical operating characteristics (vcca = 5v, and t a = +25 c using circuit in figure 1, unless otherwise noted) output current (a) output voltage vs. load v out (%) 02468 output voltage vs. temperature, i out = 10a nom. +0.25 +0.50 -0.25 -0.50 0255075 output voltage (%) 10 +1.0 +0.5 nom -0.5 -1.0 -1.5 +1.5 100 125 transient response, 0.5 to 5.5a i sw (2a/div) v out (50mv/div) time (100 s/division) output ripple, i out = 10a) v out (10mv/division) time (2 s/division) efficiency vs. output current 95 94 93 92 91 90 89 88 87 86 85 efficiency (%) 12 3 4 5 output current 678910
product specification rc5037 5 typical operating characteristics (continued) application circuit figure 1. 13a at 3.3v application schematic pin 7 (drv), 10a load pin 7 (drv), 0.1a load time (1s/division) time (1s/division) output startup, system power-up time (5ms/division) +12v c6 180pf q1 fdb6030l + d1 mbrb1545ct l2 2.5 h l1 4.7 h r3 5.2m r1 r2 47 4.7 c1 0.1 f u1 rc5037 2 3 4 1 7 6 5 8 c3 1200 f d2 mmbd4148 d3 1n4735a +5v 1 f c5 0.1uf c7 0.1 f c8 + c4 1200 f + c2 1200 f v core + + 1500 f c14 ... r5 2k r4 2.43k optional
rc5037 product specification 6 table1. bill of materials for a rc5037 3.3v, 13a application qty. reference manufacturer part order # description requirements and comments 3 c1, c7-8 any 100nf, 25v capacitor 3 c2-4 sanyo 10mv1200gx 1200f, 10v aluminum capacitor i rms = 2a , see equation (2) in applications 1 c5 any 1f, 25v capacitor 1 c6 any 180pf, 50v capacitor c0g 6 c9-14 sanyo 6mv1500gx 1500f, 6.3v aluminum capacitor esr = 44m w 1 r1 any 47.5 w 1 r2 any 4.75 w 1 r3 n/a 5.2m w , 1w resistor pcb trace resistor, see eauation (3) applications 1 r4 any 2.43k w 1 r5 any 2k w 1 d1 motorola mbrb1545ct 15a, 45v schottky 1 d2 fairchild mmbd4148 signal diode 1 d3 motorola 1n4735a 6.2v zener 1 q1 fairchild fdb6030l 30v, 14m w logic level mosfet optional l1 any 2.5h inductor i sat > 8a 1 l2 any 4.7h inductor i sat > 13a 1 u1 fairchild rc5037m pwm controller application information the rc5037 contains a precision trimmed zero tc voltage reference, a constant-on-time architecture controller, a high current output driver, and a low offset error amp. the detailed block diagram in figure 1 shows how the rc5037 works together with external components to achieve a high- performance switching power supply. switch-mode control loop the main control loop for the switch-mode converter consists of a current conditioning ampli?er and a voltage conditioning ampli?er. the voltage ampli?er compares the voltage from the internal reference with the converters output voltage divided by an external resistor divider. the current ampli?er senses the current by comparing the voltages at the ifbh and ifbl pins, which are attached to either side of the current sense resistor. the signals from the voltage and current ampli?ers are summed together, the result being used to control the off-time of the oscillator. the current feedback signal is also used as part of the rc5037 short-circuit protection. high current output drivers the rc5037 high current output driver (drv) contains high speed bipolar power transistors con?gured in a push-pull con?guration. the output driver is capable of supplying 0.5a of current in less than 100ns. the drivers power and ground are separated from the overall chip power and ground for added switching noise immunity. internal reference the reference in the rc5037 is a precision band-gap type reference. its temperature coef?cient is trimmed to provide a near zero tc. constant-on-time oscillator the rc5037 switch-mode oscillator is designed as a ?xed on-time, variable off-time oscillator. the constant-on-time oscillator consists of a comparator, an external capacitor, a ?xed current source, a variable current source, and an analog switch that selects between two threshold voltages for the comparator. the external timing capacitor is alternately
product specification rc5037 7 charged and discharged through the enabling and disabling of the ?xed current source. the variable current source is controlled from the error inputs that are received from the current and voltage feedback signals. the oscillator off-time is controlled by the amount of current that is available from the variable current source to charge the external capacitor up to the high threshold level of the comparator. the on-time is set by the constant current source that discharges the external capacitor voltage down to the lower comparator threshold. figure 2. rc5037 detailed block diagram i o i on constant on-time oscillator g m g m v h v l v out +5v vcca ifbl ifbh vccp fbsw sdrv gndp cext 65-5037-07 +12v ref 6 5 1 2 4 3 8 7 output voltage selection the rc5037 precision reference is trimmed to be 1.5v nom- inally. when using the rc5037, the system designer has complete ?exibility in choosing the output voltage for one regulator from 1.5v to 3.6v. this is done by appropriately selecting the feedback resistors. these could be 0.1% resis- tors to realize optimum output accuracy. the following equations determines the output voltage of the regulator: for example, for 3.3v: input capacitors the number of input capacitors required for the rc5037 is dependent on their ripple current rating, which assures their rated life. the number required may be determined by where the duty cycle dc = v out /v in . for example, with a 1.5v output at 10a, 5v input, and using the sanyo capaci- tors speci?ed in table 1 which have a 2a ripple current rat- ing, we have dc = 1.5/5 = 0.3, and so that we need 3 input capacitors. short circuit considerations the rc5037 uses a current sensing scheme to limit the load current if an output fault condition occurs. the current sense resistor carries the peak current of the inductor, which is greater than the maximum load current due to ripple current ?owing in the inductor. the rc5037 will begin to limit the output current to the load by reducing the duty cycle of the top-side mosfet driver when the voltage across the cur- rent-sense resistor exceeds the short circuit comparator threshold voltage (v th ). when this happens the output volt- age will temporarily go out of regulation. as the voltage across the sense resistor becomes larger, the duty cycle of the top-side mosfet will continue to be reduced until the cur- rent limit value is reached. at this point, the rc5037 will continuously deliver the limit current at a reduced output voltage level. the short circuit comparator threshold voltage is typically 90mv, with a tolerance of 10mv. the ripple current ?owing through the inductor in figure 1 is 0.6a. refer to application note am-53 for detailed discussions. the sense resistor value can be approximated as follows: v out 1.5 r4 r5 + r5 -------------------- - ? ?? = (1) v out 1.5 r4 r5 + r5 -------------------- - ? ?? 1.5 2.43k 2.0k + 2.0k ------------------------------ - ? ?? 3.3v == = no. caps i out dc dc 2 C * i rating --------------------------------------- - = (2) no. caps 0.03 0.3 2 C 10* 2 ----------------------------------- - 2.29 == r sense v th,min i pk ---------------- 1tf C () v th,min 0.6a i load,max + --------------------------------------------- 1tf C () == (3)
rc5037 product specification 8 where tf = tolerance factor for the sense resistor and 0.6a accounts for the inductor ripple current. since the value of the sense resistor is often less than 10m w , care should be taken in the layout of the pcb. trace resis- tance can contribute signi?cant errors. the traces to the ifbh and ifbl pins of the rc5037 should be kelvin con- nected to the pads of the current-sense resistor. to minimize the in?uence of noise, the two traces should be run next to each other. schottky diode in figure 1, mosfet q1 and ?yback diode d1 are used as complementary switches in order to maintain a constant cur- rent through the output inductor l2. as a result, d1 will have to carry the full current of the output load when the power mosfet is turned off. the power in the diode is a direct function of the forward voltage at the rated load current dur- ing the off time of the fet. the following equation can be used to estimate the diode power: where i d is the forward current of the diode, v d is the for- ward voltage of the diode, and dutycycle is de?ned the same as for the motorola mbrb1545ct recti?er in figure 1, it is recommended that the diode t0-220 package be attached to a heatsink. board design considerations mosfet placement placement of the power mosfet is critical in the design of the switch-mode regulator. the mosfet should be placed in such a way as to minimize the length of the gate drive path from the rc5037 sdrv pin. this trace should be kept under 0.5" for optimal performance. excessive lead length on this trace will cause high frequency noise resulting from the par- asitic inductance and capacitance of the trace. since this voltage can transition nearly 12v in around 100nsec, the resultant ringing and noise would be very dif?cult to sup- press. this trace should be routed on one layer only and kept well away from the quiet analog pins of the device: cext, ifbh, ifbl, and gnd. refer to figure 2. a 4.7 w resistor in series with the mosfet gate can decrease this layout criti- cality. refer to figure 1. inductor and schottky diode placement the inductor and ?y-back schottky diode need to be placed close to the source of the power mosfet for the same rea- sons stated above. the node connecting the inductor and schottky diode will swing between the drain voltage of the fet and the forward voltage of the schottky diode. it is rec- ommended that this node be converted to a plane if possible. this node will be part of the high current path in the design, and as such it is best treated as a plane in order to minimize the parasitic resistance and inductance on that node. since most pc board manufacturers utilize 1/2 oz copper on the top and bottom signal layers of the pcb, it is not recom- mended to use these layers to route the high current portions of the regulator design. since it is more common to use 1 oz. copper on the pcb inner layers, it is recommended to use those layers to route the high current paths in the design. p diode i d v d 1 dutycycle C () = duty cycle vout vin ------------ - = p diode 10a 0.65 1 73.1% C () 1.75w == figure 3. examples of good and poor layouts 5 6 7 8 5 = "quiet" pins 6 7 4 3 2 81 4 3 2 1 example of a good layout example of a problem layout noisy signal radiates onto quiet pins and the trace is too long. gate resistor is far away from the mosfet. noisy signal is routed away from quiet pins and the trace length is kept under 0.5in. the gate resistor is as close as possible to the mosfet.
product specification rc5037 9 power and ground connections the connection of vcca to the 5v power supply plane should be short and bypassed with a 0.1f directly at the vcca pin of the rc5037. the ideal connection would be a via down to the 5v power plane. a similar arrangement should be made for the vccp pin that connects to +12v. each ground should have a separate via connection to the ground plane below. a 12v power supply is used to bias the vccp. a 47 w resis- tor is used to limit the transient current into vccp. a 1uf capacitor ?lter is used to ?lter the vccp supply and source the transient current required to charge the mosfet gate capacitance. this method provides suf?ciently high gate bias voltage to the mosfet (v gs ), and therefore reduces r ds(on) of the mosfet and its power loss. figure 4 provides about 5v of gate bias which works well when using typical logic-level mosfets. non-logic-level mosfets should not be used because of their higher r ds(on) . mosfet gate bias figure 4. 12v gate bias configuration v out +5v vccp 47 q1 l2 r sense c bulk d1 1 f gndp +12v
product specification rc5037 10 mechanical dimensions 8 lead soic package 85 14 d a a1 ?c ccc c lead coplanarity seating plane e b l h x 45 c a eh a .053 .069 1.35 1.75 symbol inches min. max. min. max. millimeters notes a1 .004 .010 0.10 0.25 .020 0.51 b .013 0.33 c .008 .010 0.20 0.25 e .150 .158 3.81 4.01 e .228 .244 5.79 6.20 .010 .020 0.25 0.50 h .050 bsc 1.27 bsc h l .016 .050 0.40 1.27 0 8 0 8 3 6 5 2 2 n8 8 a ccc .004 0.10 d .189 .197 4.80 5.00 notes: 1. 2. 3. 4. 5. 6. dimensioning and tolerancing per ansi y14.5m-1982. "d" and "e" do not include mold flash. mold flash or protrusions shall not exceed .010 inch (0.25mm). "l" is the length of terminal for soldering to a substrate. terminal numbers are shown for reference only. "c" dimension does not include solder finish thickness. symbol "n" is the maximum number of terminals.
rc5037 product specification 1/26/00 0.0m 001 stock#ds30005037 1998 fairchild semiconductor corporation life support policy fairchilds products are not authorized for use as critical components in life support devices or systems without the express written approval of the president of fairchild semiconductor corporation. as used herein: 1. life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury of the user. 2. a critical component in any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. www.fairchildsemi.com ordering information product number package rc5037m 8 pin soic
trademarks acex? coolfet? crossvolt? e 2 cmos tm fact? fact quiet series? fast ? fastr? gto? hisec? the following are registered and unregistered trademarks fairchild semiconductor owns or is authorized to use and is not intended to be an exhaustive list of all such trademarks. life support policy fairchild?s products are not authorized for use as critical components in life support devices or systems without the express written approval of fairchild semiconductor corporation. as used herein: 1. life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, or (c) whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in significant injury to the user. 2. a critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. product status definitions definition of terms datasheet identification product status definition advance information preliminary no identification needed obsolete this datasheet contains the design specifications for product development. specifications may change in any manner without notice. this datasheet contains preliminary data, and supplementary data will be published at a later date. fairchild semiconductor reserves the right to make changes at any time without notice in order to improve design. this datasheet contains final specifications. fairchild semiconductor reserves the right to make changes at any time without notice in order to improve design. this datasheet contains specifications on a product that has been discontinued by fairchild semiconductor. the datasheet is printed for reference information only. formative or in design first production full production not in production disclaimer fairchild semiconductor reserves the right to make changes without further notice to any products herein to improve reliability, function or design. fairchild does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights, nor the rights of others. syncfet? tinylogic? uhc? vcx? isoplanar? microwire? pop? powertrench qfet? qs? quiet series? supersot?-3 supersot?-6 supersot?-8 ? rev. d
product folder - fairchild p/n rc5037 - adjustable switching regulator controller fairchild semiconductor space space space search | parametric | cross reference space product folders and datasheets application notes space space space find products home >> find products >> space space space space products groups space analog and mixed signal discrete interface logic microcontrollers non-volatile memory optoelectronics markets and applications new products product selection and parametric search cross-reference search technical information buy products technical support my fairchild company rc5037 adjustable switching regulator controller related links request samples dotted line how to order products dotted line product change notices (pcns) dotted line support dotted line distributor and field sales representatives dotted line quality and reliability dotted line design tools contents general description | features | applications | product status/pricing/packaging | application notes general description the rc5037 is a high power, switch-mode dc- dc controller that provides efficient power for all low-voltage applications. this controller has a built-in soft start feature which offers system protection during power- up by reducing both inrush current and output overshoot. when combined with the appropriate external circuitry, the rc5037 can deliver load currents as high as 13a at efficiencies as high as 88%. the rc5037 can generate output voltages from 1.5v up to 3.6v using external resistors. the rc5037 is designed to operate in a constant on-time control mode under all load conditions. its accurate low tc reference eliminates the need for precision external compo-nents in order to achieve the tight tolerance voltage regula-tion required by many applications. short circuit current protection is provided through the use of a current sense resistor, while overvoltage protection is provided internally. back to top features space datasheet download this datasheet pdf e-mail this datasheet [e- mail] this page print version file:///c|/pdf/rc5037.html (1 of 2) [27-jul-02 11:35:49 am]
product folder - fairchild p/n rc5037 - adjustable switching regulator controller l high power switch-mode dc-dc controller can provide in excess of 13a l output voltage adjustable from 1.5v to 3.6v l 85% efficiency l cumulative accuracy < 3% over line, load, and temperature variations l overvoltage and short circuit protection l precision trimmed low tc voltage reference l built-in soft start back to top applications l i/o and agp power for desktop computers l high efficiency power for asics l high efficiency power for dsps l adjustable step-down power supplies back to top product status/pricing/packaging product product status pricing* package type leads package marking packing method RC5037MT full production $0.77 soic 8 $y&z&2&t rc5037m tape reel rc5037m full production $0.77 soic 8 $y&z&2&t rc5037m rail * 1,000 piece budgetary pricing back to top application notes ab-23: ab-23 a 1a, 3.3v converter with high efficiency and small footprint (22 k) jul 19, 2002 back to top space space home | find products | technical information | buy products | support | company | contact us | site index | privacy policy ? copyright 2002 fairchild semiconductor space space file:///c|/pdf/rc5037.html (2 of 2) [27-jul-02 11:35:49 am]

▲Up To Search▲

Price & Availability of RC5037MT

	To Download RC5037MT Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .