ppmic bu www.belling.com.cn BL9328 rev 0.3 belling proprietary informatio n. unauthorized photocopy and duplication prohibited 6/2010 ?2010 belling all rights reserved 1 BL9328 1.5 mhz, dual 800ma sync hronous buck converter features ? high efficiency: up to 96% ? 1.5mhz constant switching frequency ? current mode operation for excellent line and load transient response ? no schottky diode required ? 2.5v to 5.5v input voltage range ? adjustable output voltage ? 100% duty cycle in dropout mode ? output current:up to 800ma per channel ? low quiescent current: 180 a each ? over temperature protection ? short circuit protection ? shutdown quiescent current < 1 a ? compact and thermally enhanced package:esop-8 applications ? cellular and smart phones ? wireless handsets and dsl modems ? microprocessors and dsp core supplies ? pdas ? digital still and video cameras ? mp3/mp4/mp5 players ? portable instruments ? gps receivers description the BL9328 is a dual constant frequency, 1.5mhz, slope compensated current mode pwm step-down converter working under an input voltage range of 2.5v to 5.5v. this feature makes the BL9328 suitable for single cell li-ion battery-powered applications. the internal synchronous rectifier is desired to increase efficiency without an external schottky diode. 100% duty cycle capability extends battery life in portable devices, while the quiescent current is 180 a at no load, and drops to < 1 a in shutdown. pulse skipping mode operation increases efficiency at light loads, further extending battery life. low output voltage ripple and small external inductor and capacitor sizes are achieved with 1.5mhz switching frequency. the BL9328 is offered in a compact and thermally enhanced esop-8 package, and is available in an adjustable version. ordering information typical application BL9328 ? x xxxx figure 1. BL9328-adj typical application circuit package espa: esop-8-a espb: esop-8-b features: p: standard (default, lead free) c: customized
ppmic bu www.belling.com.cn BL9328 rev 0.3 belling proprietary information. unauthor ized photocopy and du plication prohibited 6/2010 ?2010 belling all rights reserved 2 BL9328 1.5 mhz, dual 800ma sy nchronous buck converter absolute maximum rating (note1) input supply voltage(in1,in2)???-0.3v to +6v en1,en2,v fb1 ,v fb2 voltages???-0.3v to +v in sw1,sw2 voltages?????-0.3v to (v in +0.3v) p-channel switch source current (dc) ???1a n-channel switch sink current (dc) ????1a peak sw sink and source current?????1.4a operating temperature range??-40c to +85c junction temperature (note2) ??????+125c storage temperature range???-65c to +150c lead temperature (soldering, 10s) ???+300c package information y 9 a b c d year 2009 2010 2011 2012 2013 w w 01 ? 09 10 11 ? 51 52 week 1 ? 9 10 11 ? 51 52 thermal resistance (note 4) package ? ja ? jc esop-8 50 c/w 10c/w note 1: absolute maximum ratings are those values bey ond which the life of a device may be impaired. note 2: t j is calculated from the ambient temperature t a and power dissipation p d according to the following formula: t j = t a + (p d ) x (50c/w). note 3: a b: package type (a: esop-8-a, b: esop-8-b) y: year of wafer manufacturing w w: week of wafer manufacturing note 4: thermal resistance is specified with approximately 1 square of 1 oz copper. 1 2 3 8 esop-8-a in1 sw1 in2 fb1 9 gnd 4 sw2 7 en1 6 fb2 5 en2 part number top mark temp range BL9328 BL9328 a y w w (note3) -40c to +85c 1 2 3 8 esop-8-b in1 sw1 in2 en1 9 gnd 4 sw2 7 fb1 6 en2 5 fb2 part number top mark temp range BL9328 BL9328 b y w w (note3) -40c to +85c
ppmic bu www.belling.com.cn BL9328 rev 0.3 belling proprietary information. unauthor ized photocopy and du plication prohibited 6/2010 ?2010 belling all rights reserved 3 BL9328 1.5 mhz, dual 800ma sy nchronous buck converter pin description name function in1,in2 supply input pin. must be closely deco upled to gnd with a 2.2f or greater ceramic capacitor. sw1,sw2 power switch output. it is the switch node connection to external inductor. this pin connects to the drains of the internal p-channel and n-channel mosfet switches. en1,en2 regulator enable control input. drive en above 1.5v to turn on the part. drive en below 0.3v to turn it off. in s hutdown, all functions are disabled drawing <1a supply current. do not leave en floating. fb1,fb2 feedback input pin. connect fb to the c enter point of the external resistor divider. the regulated voltage on this pin is 0.6v. gnd power ground pin. block diagram esop-8-a esop-8-b
ppmic bu www.belling.com.cn BL9328 rev 0.3 belling proprietary informatio n. unauthorized photocopy and duplication prohibited 6/2010 ?2010 belling all rights reserved 4 BL9328 1.5 mhz, dual 800ma sync hronous buck converter electrical characteristics (note5) (v in1 = v in2 =v en1 = v en2 = 3.6v, t a = 25c, unless otherwise noted.) parameter conditions min typ max unit input voltage range 2.5 5.5 v input dc supply current active mode shutdown mode v fb =0.5v or v out =90% v fb =0v, v in =4.2v 180 0.1 300 1.0 a t a = +25c 0.5880 0.6000 0.6120 t a = 0c t a 85c 0.5865 0.6000 0.6135 regulated feedback voltage t a = -40c t a 85c 0.5850 0.6000 0.6150 v v fb input bias current v fb = 0.65v 30 na reference voltage line regulation v in = 2.5v to 5.5v 0.04 0.4 %/v output overvoltage lockout ? v ovl = v ovl ? v fb , adjustable version 20 50 80 mv output voltage line regulation v in = 2.5v to 5.5v 0.04 0.40 % output voltage load regulation 0.5 % peak inductor current v in =3v, v fb =0.5v or v out =90% duty cycle <35% 1.2 a oscillator frequency v fb =0.6v or v out =100% 1.2 1.5 1.8 mhz r ds(on) of p-ch mosfet i sw = 300ma 0.40 0.50 ? r ds(on) of n-ch mosfet i sw = -300ma 0.35 0.45 ? sw leakage current v run = 0v, v sw = 0v or 5v, v in = 5v 0.01 1 a en threshold -40c t a 85c 0.3 1.1 1.30 v en leakage current 0.01 1 a note 5: 100% production test at +25c. s pecifications over the temperature range are guaranteed by design and characterization.
ppmic bu www.belling.com.cn BL9328 rev 0.3 belling proprietary informatio n. unauthorized photocopy and duplication prohibited 6/2010 ?2010 belling all rights reserved 5 BL9328 1.5 mhz, dual 800ma sync hronous buck converter typical performance characteristics (test figure 1 above unless otherwise specified) 0.1 1 10 100 1000 20 30 40 50 60 70 80 90 efficiency(%) output current(ma) vin=2.7v vin=3.6v vin=4.2v v out =1.8v l=2.2uh efficiency vs. output current 0 200 400 600 800 1000 1200 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 2.1 2.2 output voltage(v) load current(ma) output voltage vs. load current v in =3.6v t a =25 c -50 -25 0 25 50 75 100 125 0.602 0.603 0.604 0.605 0.606 reference voltage(v) temperature ( c ) v in =3.6v reference voltage vs. temperature 2.7 3.0 3.3 3.6 3.9 4.2 4.5 4.8 5.1 5.4 5.7 1.780 1.785 1.790 1.795 1.800 1.805 1.810 1.815 1.820 v out (v) v in (v) i load =10ma i load =100ma i load =600ma output voltage vs. input voltage supply current vs. supply voltage start_up from shutdown 23456 195 200 205 210 215 220 225 230 235 240 245 dynamic supply current(ua) supply voltage(v) v out =1.8v i load =0a t a =25 c
ppmic bu www.belling.com.cn BL9328 rev 0.3 belling proprietary informatio n. unauthorized photocopy and duplication prohibited 6/2010 ?2010 belling all rights reserved 6 BL9328 1.5 mhz, dual 800ma sync hronous buck converter load step load step load step load step pulse skipping mode output short
ppmic bu www.belling.com.cn BL9328 rev 0.3 belling proprietary information. unauthor ized photocopy and du plication prohibited 6/2010 ?2010 belling all rights reserved 7 BL9328 1.5 mhz, dual 800ma sy nchronous buck converter operation the BL9328 uses a constant frequency, current mode step-down architecture. both the main switch (p-channel mosfet) and the synchronous rectifier (n-channel mosfet) are integrated internally. this step-down dc-dc converter can supply 800ma output current over a wide input voltage range from 2.5v to 5.5v. the over voltage comparator ovdet guards against transient overshoots >7.8% by turning the main switch off and keeping it off until the fault is removed. current mode pwm control slope compensated current mode pwm control provides stable switching and cycle- by-cycle current limit for excellent load and line responses. during normal operation, the internal main switch is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and turned off when the peak inductor current reaches the controlled value. when the main switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current starts to reverse, as indicated by the current reversal comparator, i rcmp , or the beginning of the next clock cycle. pulse skipping mode operation at very light loads, the BL9328 will automatically enter pulse skipping mode to increase efficiency, further extending battery life. in this mode, the control loop skips pwm pulses while maintaining output in regulation, and the switching frequency depends on the load condition. this is a kind of pfm mode operation. dropout operation when the input voltage decreases toward the value of the output voltage, the BL9328 will keep the main switch on for more than one switching cycle and increases the duty cycle (note 6) until it reaches 100%. the output voltage then is the input voltage minus the voltage drop across the main switch and the inductor. at low input supply voltage, the r ds(on) of the p-channel mosfet increases, and the efficiency of the converter decreases. caution must be exercised to ensure the heat dissipated not to exceed the maximum junction temperature of the ic. note 6 : the duty cycle d of a step-down converter is defined as: % 100 % 100 = in out osc on v v f t d where t on is the main switch on time, and f osc is the oscillator frequency (1.5mhz). short circuit protection the BL9328 has short circuit protection. when output is shorted to ground, the oscillator frequency is reduced to prevent the inductor current from increasing beyond the pfet current limit. the pfet current limit is also reduced to lower the short circuit current. the frequency and current limit will return to the normal values once the short circuit condition is removed and the feedback voltage reaches 0.6v. maximum load current the BL9328 will operate with input supply voltage as low as 2.5v, however the maximum load current decreases at lower input voltage due to large ir drop on the main switch and synchronous rectifier.
ppmic bu www.belling.com.cn BL9328 rev 0.3 belling proprietary informatio n. unauthorized photocopy and duplication prohibited 6/2010 ?2010 belling all rights reserved 8 BL9328 1.5 mhz, dual 800ma sync hronous buck converter application information setting the output voltage figure 1 above shows the basic application circuit with BL9328 adjustable output version. the external resistor sets the output voltage according to the following equation: ) 1 2 1 ( 6 . 0 r r v v out + = table 1 ? resistor selection vs. output voltage setting vout r1 r2 1.0v 180 k ? (1%) 120 k ? (1%) 1.2v 180 k ? (1%) 180 k ? (1%) 1.5v 180 k ? (1%) 270 k ? (1%) 1.8v 180 k ? (1%) 360 k ? (1%) 2.5v 158 k ? (1%) 499 k ? (1%) 3.3v 180 k ? (1%) 810 k ? (1%) inductor selection the output inductor is selected to limit the ripple current to some predetermined value, typically 20%~40% of the full load current at the maximum input voltage. in continuous mode, the ripple current is determined by: ) 1 ( 1 in out out l v v v l f i ? = a reasonable starting point for setting ripple current is ? i l =320ma (40% of 800ma). for output voltages above 2.0v, when efficiency at light load condition is important, the minimum recommended inductor is 2.2h. for optimum voltage-positioning load transients, choose an inductor with dc series resistance below 150m ? . for higher efficiency at heavy loads (above 200ma), or minimal load regulation (but some transient overshoot), the resistance should be kept below 100m ? . the dc current rating of the inductor should be at least equal to the maximum load current plus half the ripple current to prevent core saturation. thus, a 960ma rated inductor should be enough for most applications (800ma+160ma). input capacitor selection the input capacitor reduces the surge current drawn from the input and switching noise from the device. the input capacitor impedance at the switching frequency shall be less than input source impedance to prevent high frequency switching current passing to the input. in continuous mode, the source current of the main switch is a square wave of duty cycle v out /v in . to prevent large voltage transients, a low esr input capacitor sized for the maximum rms current must be used. the maximum rms capacitor current is given by: in out in out omax rms v v v v i i 5 . 0 )] ( [ ? this formula has a maximum at v in =2v out , where i rms = i out /2. this simple worst-case condition is commonly used for design because even significant deviations do not offer much relief. ceramic capacitors with x5r or x7r dielectrics are recommended due to their low esr and high ripple current. output capacitor selection the output capacitor is required to keep the output voltage ripple small and to ensure regulation loop stability. the output capacitor must have low impedance at the switching frequency. ceramic capacitors with x5r or x7r dielectrics are recommended due to their low esr and high ripple current. the output ripple v out is determined by: ? ? ? ? ? ? ? ? + ? 2 8 1 ) ( c f esr l f v v v v v osc osc in out in out out layout considerations when laying out the printed circuit board, the following checklist should be used to ensure proper operation of the BL9328. check the following in your layout: 1. the power traces, consisting of the gnd trace, the sw trace and the v in trace should be kept short, direct and wide.
ppmic bu www.belling.com.cn BL9328 rev 0.3 belling proprietary informatio n. unauthorized photocopy and duplication prohibited 6/2010 ?2010 belling all rights reserved 9 BL9328 1.5 mhz, dual 800ma sync hronous buck converter 2. does the v fb pin connect directly to the feedback resistors? the resistive divider r1/r2 must be connected between the (+) plate of c out and ground. 3. does the (+) plate of c in connect to v in as closely as possible? this capacitor provides the ac current to the internal power mosfets. 4. keep the switching node, sw, away from the sensitive v fb node. 5. keep the (-) plates of c in and c out as close as possible.
ppmic bu www.belling.com.cn BL9328 rev 0.3 belling proprietary information. unauthor ized photocopy and du plication prohibited 6/2010 ?2010 belling all rights reserved 10 BL9328 1.5 mhz, dual 800ma sy nchronous buck converter package description dimensions in millimeters symbol min nom max a 1.77 a1 0.08 0.18 0.28 a2 1.2 1.4 1.6 a3 0.55 0.65 0.75 b 0.39 0.48 b 1 0.38 0.41 0.43 c 0.21 0.26 c 1 0.19 0.2 0.21 d 4.7 4.9 5.1 e 5.8 6 6.2 e1 3.7 3.9 4.1 e 1.27bsc l 0.5 0.65 0.8 l1 1.05bsc 0 8 d1 3.30ref e2 2.40ref esop-8 surface mount package
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