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ap1534 pwm control 2a step-down converter ap1534 rev. 4 1 of 11 september 2008 www.diodes.com ? diodes incorporated features general description ap1534 consists of step-down switching regulator with pwm control. these devices incl ude a reference voltage source, oscillation circuit, error amplifier, internal pmos. ? input voltage: 3.6v to 18v ? output voltage: 0.8v to v cc . ? duty ratio: 0% to 99% pwm control ? oscillation frequency: 300khz typical ap1534 provides low-ripple power, high efficiency, and excellent transient characteristics. the pwm control circuit is able to vary the duty ratio linearly from 0 up to 99%. this converter also contains an error amplifier circuit as well as a soft-start circuit that prevents overshoot at startup. an enable function, an over current protect function and a short circuit protect function are built inside, and when ocp or scp happens, the operation frequency will be reduced from 300khz to 50khz. also, an internal compensation block is built in to minimize external component count. ? current limit, enable function ? thermal shutdown function ? built-in internal sw p-channel mos ? sop-8l: available in ?green? molding compound (no br, sb) ? lead free finish/rohs compliant (note 1) with the addition of an internal p-channel power mos, a coil, capacitors, and a diode connected externally, these ics can function as step-down switching r egulators. they serve as ideal power supply units for portable devices when coupled with the sop-8l mini-packages, providing such outstanding features as low current consumption. since this converter can accommodate an input voltage up to 18v, it is also suitable for the operation via an ac adapter. applications ? pc motherboard ? lcd monitor ? graphic card ? dvd-video player ? telecom equipment ? adsl modem ? printer and other peripheral equipment ? microprocessor core supply ordering information ap 1534 s g - x package packing s : sop-8l lead free u : tube 13 : tape & reel g : green tube 13? tape and reel device package code packaging (note 2) quantity part number suffix quantity part number suffix AP1534SG-U s sop-8l 100 -u na na ap1534sg-13 s sop-8l na na 2500/tape & reel -13 notes: 1. eu directive 2002/95/ec (rohs). all applicable rohs exemptions applied, see eu directive 2002/95/ec annex notes . 2. pad layout as shown on diodes inc. suggested pad la yout document ap02001, which can be found on our website at http://www.diodes.com/d atasheets/ap02001.pdf .
ap1534 pwm control 2a step-down converter ap1534 rev. 4 2 of 11 september 2008 www.diodes.com ? diodes incorporated pin assignments 1 2 3 4 8 7 6 5 fb output ocset output en vss vss v cc sop-8l ap1534 pin descriptions pin name pin no. desc ription fb 1 feedback pin en 2 power-off pin h: normal operation (step-down operation) l: step-down operation stopped (all circuits deactivated) ocset 3 add an external resistor to set max output current v cc 4 ic power supply pin output 5, 6 switch pin. connect external inductor/d iode here. minimize trace area at this pin to reduce emi v ss 7, 8 gnd pin
ap1534 pwm control 2a step-down converter ap1534 rev. 4 3 of 11 september 2008 www.diodes.com ? diodes incorporated block diagram oscillation circuit reference voltage source pwm-switched control circuit + - vss v en en 100ua ocset fb vcc thermal shutdown output absolute maximum ratings symbol parameter rating unit esd hbm human body model esd protection 4.5 kv esd mm machine model esd protection 150 v v cc v cc pin voltage v ss - 0.3 to v ss + 20 v v fb feedback pin voltage v ss - 0.3 to v cc v v en en pin voltage v ss - 0.3 to v in v v out switch pin voltage v ss - 0.3 to v in v p d power dissipation internally limited mw t j operating junction temperature range -40 to +125 o c t st storage temperature range -65 to +150 o c caution: the absolute maximum ratings are rated values exceeding which the product could suffer physical damage. these values must theref ore not be exceeded under any conditions. recommended operating conditions symbol parameter min max unit v in input voltage 3.6 18 v i out output current 0 2 a t a operating ambient temperature -20 85 o c
ap1534 pwm control 2a step-down converter ap1534 rev. 4 4 of 11 september 2008 www.diodes.com ? diodes incorporated electrical characteristics ( v in = 12v, t a = 25c, unless otherwise specified ) symbol parameter conditions min typ. max unit v fb feedback voltage i out = 0.1a 0.784 0.8 0.816 v i fb feedback bias current i out = 0.1a - 0.1 0.5 a i sw switch current -- 2.0 - - a i shdn current consumption during power off v en = 0v - 10 - a ? v out / v in line regulation v in = 5v~18v - 1 2 % ? v out /v out load regulation i out = 0.1 to 2a - 0.2 0.5 % f osc oscillation frequency measure waveform at sw pin 240 300 400 khz f osc1 frequency of current limit or short circuit protect measure waveform at sw pin - 50 - khz v ih evaluate oscillation at sw pin 2.0 - - v il en pin input voltage evaluate oscillation stop at sw pin - - 0.8 v i sh -- - 20 - a i sl en pin input leakage current -- - -10 - a i ocset ocset pin bias current -- 75 90 105 a v in = 5v, v fb = 0v - 160 - r ds(on) internal mosfet r ds(on) v in = 12v, v fb = 0v - 100 - m ? effi efficiency v in = 12v, v out = 5v i out = 2a - 91 - % t shdn thermal shutdown threshold - 150 - c t hys thermal shutdown hysteresis - 55 - c ja thermal resistance junction-to-ambient sop-8l (note 3) - 127 - o c/w jc thermal resistance junction-to-case sop-8l (note 3) - 28 - o c/w notes: 3. test condition for sop-8l: device mounted on fr-4 substrate pc board, 2oz copper, with minimum recommended pad layo ut. for better thermal performance, larger copper pad for heatsink is needed. typical application circuit ap1534 + - v ss en c c r a r b b240a fb vcc output cvcc v out =5v/2a v in r ocset ocset c out c in optional c ocset c en r en option 100k note: v out = v fb x (1+r a /r b ) r b =0.7k~5k ohm l1 22uh 6.8k 1.3k 5.6k 0.1uf + - c 0.1uf 470uf 470uf 0.1uf (note 4) d1 notes: 4. suggested diodes powe r schottky p/n: b240/b340 series.
ap1534 pwm control 2a step-down converter ap1534 rev. 4 5 of 11 september 2008 www.diodes.com ? diodes incorporated typical performance characteristics v in vs frequency (v out =3.3v, i out =0.2a) 306 308 310 312 314 316 318 320 322 324 326 0 2 4 6 8 1012141618 v in (v) f osc (khz) v in vs v fb (v out =3.3v, i out =0.2a) 0.780 0.785 0.790 0.795 0.800 0.805 0.810 0.815 0.820 0 2 4 6 8 1012141618 v in (v) v fb (v) line regulation (v out =3.3v, i out =0.2a) -3.0% -2.0% -1.0% 0.0% 1.0% 2.0% 3.0% 024681012141618 v in (v) v out change (%) load regulation (v in =5v, v out =3.3v) -1.0% -0.8% -0.6% -0.4% -0.2% 0.0% 0.2% 0.4% 0.6% 0.8% 1.0% 0.0 0.5 1.0 1.5 2.0 i out (a) v out change (%) efficiency 0 10 20 30 40 50 60 70 80 90 100 0.0 0.5 1.0 1.5 2.0 i out (a) efficiency (%) vout=3.3v vout=5v
ap1534 pwm control 2a step-down converter ap1534 rev. 4 6 of 11 september 2008 www.diodes.com ? diodes incorporated typical performance characteristics (continued) vout ripple (vin=5v, vout=3.3v, iout=0.1a) vout ripple (vin=5v, vout=3.3v, iout=2a) test circuit a fb v cc v ss en open open fb en + - oscillation output output a fb en + - + - v output ocset ocset ocset enable function test feedback function test operation function test v cc v cc v ss v ss
ap1534 pwm control 2a step-down converter ap1534 rev. 4 7 of 11 september 2008 www.diodes.com ? diodes incorporated functional description pwm control the ap1534 is a dc/dc converter that employs pulse width modulation (pwm) scheme. its pulse width varies in the range of 0% to 99%, based on the output current loading. the output ripple voltage caused by the pwm high frequency switching can easily be reduced through an output filter. therefore, this converter provides a low rippl e output supply over a broad range of input voltage & output current loading under voltage lockout the under voltage lockout circuit of the ap1534 assures that the high-side mosfet driver remains in the off state whenever the supply voltage drops below 3.3v. normal operation resumes once v cc rises above 3.5v. current limit protection the current limit threshold is set by external resistor r ocset connected from v cc supply to ocset pin. the internal sink current i ocset (90ua typical) across this resistor sets the voltage at ocset pin. when the pwm voltage is less than the voltage at ocset, an over-current condition is triggered. the current limit threshold is given by the following equation: riri ocset ocset ds(on) peak = 2 i)( ii (max) out peak + > where, in out s out in v v lf vv i ? = i peak is the output peak current; r ds (on) is the mosfet on resistance; f s is the pwm frequency (300khz typical). also, the inductor value will affect the ripple current ? i. the above equation is recommended for input voltage range of 5v to 18v. for input voltage lower than 5v or ambient temperature over 100c, higher r ocset is recommended. the recommended minimum r ocset value is summarized below: v in (v) v out (v) r ocset ( ) 4 1 6.8k 5 3.3 5.6k 12 5 3.9k 18 12 4.7k inductor selection for most designs, the operates with inductors of 22h to 33h. the inductor value can be derived from the following equation: in out s out in v v if vv l ? ? = where i l is inductor ripple current. lar ge value inductors lower ripple current and small value i nductors result in high ripple current. choose inductor ripple current approximately 15% of the maximum load current 2a, i l =0.3a. 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 (2a+0.15a). input capacitor selection this capacitor should be located cl ose to the ic using short leads and the voltage rating should be approximately 1.5 times the maximum input voltage. the rms current rating requirement for the input capacitor of a buck regulator is approximately 1 2 the dc load current. a low esr input capacitor sized for maximum rms current must be used. a 470f low esr capacitor for most applications is sufficient. output capacitor selection the output capacitor is required to filter the output voltage and provides regulator loop stabili ty. the important capacitor parameters are the 100khz equivalent series resistance (esr), the rms ripples current rating, voltage rating and capacitance value. for the output capacitor, the esr value is the most important parameter. the output ripple can be calculated from the following formula. es r iv l ripple = the bulk capacitor?s esr will determine the output ripple voltage and the initial voltage drop after a high slew-rate transient. an aluminum electrolytic capacitor 's esr value is related to the capacitance and its voltage rating. in most case, higher voltage electrolytic capacitors have lower esr values. most of the time, capacitors with much higher voltage ratings may be needed to provide the low esr values requir ed for low output ripple voltage. pcb layout guide if you need low t c & t j or large p d (power dissipation), the dual sw pins(5& 6) and vss pins(7& 8)on the sop-8l package are internally connected to die pad, the evaluation board should be allowed for maximum copper area at output (sw) pins. 1. connect fb circuits (r a , r b , c c ) as closely as possible and keep away from inductor flux for pure v fb . 2. connect c vcc to vcc and vss pin as closely as possible to get good power filter effect. 3. connect r ocset to vcc and ocset pin as closely as possible. 4. connect ground side of the c in & d1 & c out as closely as possible and use ground plane for best performance.
ap1534 pwm control 2a step-down converter ap1534 rev. 4 8 of 11 september 2008 www.diodes.com ? diodes incorporated top side layout guide bottom side layout guide functional description (continued) connect fb circuits closer and keep away from l1. use vias to conduct the heat into the backside of pcb layer. the heat sink at output (sw) pins should be allowed for maximum solder-painted area.
ap1534 pwm control 2a step-down converter ap1534 rev. 4 9 of 11 september 2008 www.diodes.com ? diodes incorporated ap1534 + - v ss en c1 r1 r2 fb vcc output c3 v out v in r4 ocset c4 c2 option c7 c6 r5 option l1 + - c8 d1 + + - - figure: layout numbering comparison. ( top view ) sop-8l ap1534 yy ww x x logo part no. internal code year : "07" = 2007 "08" = 2008 xth week: 01~52 ~ 5 8 4 1 g : green functional description (continued) marking information
ap1534 pwm control 2a step-down converter ap1534 rev. 4 10 of 11 september 2008 www.diodes.com ? diodes incorporated package information (all dimensions in mm) 1.27typ 0.3/0.5 7~9 4.80/5.30 3.70/4.10 5.79/6.20 0.20typ 7~9 3.70/4.10 0.38/1.27 0.08/0.25 gauge plane 0.254 seating plane 0.35max. 45 detail "a" detail "a" 1.30/1.50 1.75max. land pattern recommendation 0.78 (unit: mm) 6x-1.27 8x-1.55 8x-0.60 5.4
ap1534 pwm control 2a step-down converter ap1534 rev. 4 11 of 11 september 2008 www.diodes.com ? diodes incorporated important notice life support diodes incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or ot her changes without further notice to any product herein. diodes incorporated does not assume any liability arising out of the application or use of any pr oduct described herein; neither does it convey any license under its patent rights, nor the rights of others. the user of products in such applications shall a ssume all risks of such use and will agree to hold diodes incorporated and all the companies whose products are represented on our website, harmless against all dam ages. diodes incorporated products are not authorized for use as critical components in life support devices or systems without the e xpressed written approval of the president of diodes incorporated.

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