data sheet 1.2a, 1.4mhz, dual synchronous dc-dc buck converter ap3423 oct. 2011 rev. 1. 1 bcd semiconductor manufacturing limited 1 general description the ap3423 is a dual high-efficiency, 1.4mhz fixed frequency, current mode, pwm synchronous buck (step-down) dc-dc converter, capable of driving a 1.2a load with high effi ciency, excellent line and load regulation. the ap3423 integrates synchronous p-channel and n-channel power mosfet switches with low on-resistance. it is ideal for portable applications powered from a single li-ion battery. 100% duty cycle and low on-resistance p-channel internal power mosfet can maximize the battery life. the switching frequency of ap3423 is 1.4mhz, which allows small-sized components, such as capacitors and inductors . a standard series of inductors from several di fferent manufacturers are available. this feature greatly simplifies the design of switch-mode power supplies. the ap3423 is available in dfn-33-12 package. features ? dual channel dc-dc converter ? independent enable control ? input voltage range: 2.5 to 5.5v ? adjustable output from 0.6 to v in ? 0.6v reference voltage with 2% precision ? output current: 1.2a ? high efficiency: up to 95% ? low r dson internal switches ? operation frequency: 1.4mhz ? current mode control ? 100% duty cycle ? built-in soft-start ? built-in uvlo function ? built-in short circuit protection ? built-in current limit function ? built-in thermal shutdown protection ? dfn-33-12 package applications ? portable media player ? digital still and video cameras ? notebook figure 1. package type of ap3423 dfn-33-12
data sheet 1.2a, 1.4mhz, dual synchronous dc-dc buck converter ap3423 oct. 2011 rev. 1. 1 bcd semiconductor manufacturing limited 2 pin configuration dn package (dfn-33-12) figure 2. pin configuration of ap3423 (top view) pin description pin number pin name description 1 vin2 power input supply of channel 2. decouple this pin to gnd with a capacitor 2 sw2 internal power switch output of channel 2. connect this pin with one terminal of the inductor 3, 9 gnd power ground. connect this pin as close as possible to c in and c out 4 fb1 feedback voltage of channel 1. this pin is the inverting input of internal error amplifier. it senses the converte r output voltage through an external resistor divider. the internal reference voltage is 0.6v, which determines the output voltage through the resistor divider 5, 11 nc no connection 6 en1 chip enable of channel 1 (active high) 7 vin1 power input supply of channel 1. decouple this pin to gnd with a capacitor 8 sw1 internal power switch output of channel 1. connect this pin with one terminal of the inductor 10 fb2 feedback voltage of channel 2. this pin is the inverting input of internal error amplifier. it senses the converte r output voltage through an external resistor divider. the internal reference voltage is 0.6v, which determines the output voltage through the resistor divider 12 en2 chip enable of channel 2 (active high)
data sheet 1.2a, 1.4mhz, dual synchronous dc-dc buck converter ap3423 oct. 2011 rev. 1. 1 bcd semiconductor manufacturing limited 3 functional block diagram voltage reference oscillator current sense error amplifier pwm comparator max current limit 0.6v 0.4v short circuit protection reverse comparator logic clk driver gnd en1, en2 fb1, fb2 gnd sw1, sw2 vin1, vin2 3, 9 6, 12 4, 10 3, 9 8, 2 7, 1 figure 3. functional block diagram of ap3423 ordering information ap3423 - circuit type package dn: dfn-3 3-12 package temperature range part number marking id packing type dfn-33-12 -40 to 85oc AP3423DNTR-G1 pa tape & reel bcd semiconductor's pb-free products, as designated with "g1" suffix in the part number, are rohs compliant and green. g1: green tr: tape & reel
data sheet 1.2a, 1.4mhz, dual synchronous dc-dc buck converter ap3423 oct. 2011 rev. 1. 1 bcd semiconductor manufacturing limited 4 absolute maximum ratings (note 1) parameter symbol value unit vin1,vin2 pin voltage v in -0.3 to 6 v fb1, fb2 pin voltage v fb -0.3 to v in +0.3 v en1, en2 pin voltage v en -0.3 to v in +0.3 v sw1, sw2 pin voltage v sw -0.3 to v in +0.3 v thermal resistance ja 60 oc/w operating junction temperature t j 150 oc storage temperature t stg -65 to 150 oc lead temperature (soldering, 10sec) t lead 260 oc esd (machine model) 200 v esd (human body model) 2000 v note 1: stresses greater than those listed under ?absolute maximum ratings? may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated under ?recommended operating co nditions? is not implied. exposure to ?absolute maximum ratings? for extended periods may affect device reliability. recommended operating conditions parameter symbol min max unit input voltage v in 2.5 5.5 v maximum output current i out(max) 1.2 a operating ambient temperature t a -40 85 oc
data sheet 1.2a, 1.4mhz, dual synchronous dc-dc buck converter ap3423 oct. 2011 rev. 1. 1 bcd semiconductor manufacturing limited 5 electrical characteristics v in =3.3v, v out =2.5v, t a =25oc, unless otherwise specified. parameters symbol conditions min typ max unit channel 1 and channel 2 input voltage v in 2.5 5.5 v quiescent current i q v fb =0.65v 62 100 a shutdown supply current i stby v en =gnd 0.1 1 a reference voltage v ref for adjustable output voltage 0.588 0.6 0.612 v feedback bias current i fb v fb =v in -0.1 +0.1 a output voltage accuracy ? v out -2 +2 % pmosfet r on r ds(on)_p i sw =200ma 0.28 ? nmosfet r on r ds(on)_n i sw =-200ma 0.25 ? switch current limit i lim v fb =0.55v 1.5 2.0 a v h 1.5 en pin threshold v l 0.4 v uvlo threshold v uvlo v in rising 2.3 uvlo hysteresis v hys 0.2 v oscillator frequency f osc 1.12 1.4 1.68 mhz max. duty cycle d max v fb =0v 100 min. duty cycle d min v fb =6.5v 0 % sw leakage current , n-mos v in =v sw =3.3v 0.1 a soft-start time t 1 ms thermal shutdown t otsd 160 oc thermal shutdown hysteresis t hys 20 oc
data sheet 1.2a, 1.4mhz, dual synchronous dc-dc buck converter ap3423 oct. 2011 rev. 1. 1 bcd semiconductor manufacturing limited 6 typical performance characteristics v in =3.3v, v out =2.5v, t a =25oc, unless otherwise specified. figure 4. v out1 efficiency vs. i out1 figure 5. v out2 efficiency vs. i out2 figure 6. efficiency vs. output current figure 7. v out1 vs. i out1 -200 0 200 400 600 800 1000 1200 1400 2.46 2.47 2.48 2.49 2.50 2.51 2.52 v en2 =0v, v out1 =2.5v v in =3.3v v in =5v v out1 (v) i out1 (ma) 200 400 600 800 1000 1200 45 50 55 60 65 70 75 80 85 90 95 100 v out1 efficiency (%) i out1 (ma) v out1 =2.5v,v en2 =0v v in =3.3v v in =5v 200 400 600 800 1000 1200 45 50 55 60 65 70 75 80 85 90 95 100 v out2 =2.5v,v en1 =0v v in =3.3v v in =5v v out2 efficiency (%) i out2 (ma) 200 400 600 800 1000 1200 45 50 55 60 65 70 75 80 85 90 95 100 v out1 =v out2 =2.5v v en1 =v en2 =v in v in =3.3v v in =5v efficiency (%) output current (ma)
data sheet 1.2a, 1.4mhz, dual synchronous dc-dc buck converter ap3423 oct. 2011 rev. 1. 1 bcd semiconductor manufacturing limited 7 typical performance characteristics (continued) v in =3.3v, v out =2.5v, t a =25 , unless otherwise specified. figure 8. v out2 vs. i out2 figure 9. output voltage vs. input voltage figure 10. output voltage vs. input voltage -200 0 200 400 600 800 1000 1200 1400 2.46 2.47 2.48 2.49 2.50 2.51 2.52 v en1 =0v,v out2 =2.5v v in =3.3v v in =5v v out2 (v) i out2 (ma) 2.53.03.54.04.55.05.56.0 2.480 2.485 2.490 2.495 2.500 2.505 2.510 output voltage (v) input voltage (v) i out1 =1ma, i out2 =1ma, v out1 =2.5v i out1 =1ma, i out2 =1ma, v out2 =2.5v i out1 =1ma, i out2 =1a, v out1 =2.5v i out1 =1a, i out2 =1ma, v out2 =2.5v 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 2.42 2.43 2.44 2.45 2.46 2.47 2.48 2.49 2.50 2.51 2.52 i out1 =1a, i out2 =1ma, v out1 =2.5v i out1 =1ma, i out2 =1a, v out2 =2.5v i out1 =1a, i out2 =1a, v out1 =2.5v i out1 =1a, i out2 =1a, v out2 =2.5v output voltage (v) input voltage (v)
data sheet 1.2a, 1.4mhz, dual synchronous dc-dc buck converter ap3423 oct. 2011 rev. 1. 1 bcd semiconductor manufacturing limited 8 typical application vin2 sw2 gnd fb1 nc en1 vin1 sw1 gnd fb2 nc en2 v in2 c in2 4.7 f r2 r1 v out1 c out1 22 f l1 2.2 h c in1 4.7 f v in1 r3 r4 v out2 c out2 22 f l2 2.2 h 22pf 22pf figure 11. typical application of ap3423
data sheet 1.2a, 1.4mhz, dual synchronous dc-dc buck converter ap3423 oct. 2011 rev. 1. 1 bcd semiconductor manufacturing limited 9 mechanical dimensions dfn-33-12 unit:mm(inch) 2.450(0.096) 2.650(0.104) 0.700(0.028) 0.800(0.031) 2.900(0.114) 3.100(0.122) n6 n1 n12 n7 1.500(0.059) 1.700(0.067) 0.324(0.013) 0.476(0.019) 0.150(0.006) 0.250(0.010) 0.450(0.018)typ 0.200(0.008)min 0.000(0.000) 0.050(0.002) 0.203(0.008)ref 3.100(0.122) 2.900(0.114) pin #1 identification pin 1 mark
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