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ap65552 document number: ds37306 rev. 2 - 2 1 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 5a, 18v, 650khz adaptive ccm/cot step - down converter description the ap65 552 is an adaptive constant on - time mode synchronous buck converter providing high efficiency, excellent transient response and high dc output accuracy for low - voltage regulation in digital tv and monitor. the constant - on - time control scheme handles wide input/output voltage r atios and provides low external component count. the internal proprietary circuit enables the device to adopt both low equivalent series resistance (esr) output capacitors, such as sp - cap or poscap and ultra - low esr ceramic capacitors. the ap65 552 features programmable soft - start, uvlo, otp and ocp to protect the circuit. this ic is available in so - 8 ep package. features ? fixed frequency emulated constant on - time control ? good stability independent of the output capacitor esr ? fast load transient response ? synchronous rectification: 65m internal high - side switch and 36m internal low - side switch ? wide input voltage range: 4.5v to 1 8 v ? output voltage range: 0.76v to 6v ? 5a continuous output current ? 650khz switching frequency ? built - in over current limit ? built - in thermal shutdown protection ? programmable soft - start ? pre - biased start - up ? totally lead - free & fully rohs compliant (notes 1 & 2) ? halogen and antimony free. green device (note 3) pin assignments applications ? gaming consoles ? flat screen tv s ets and monitors ? set top boxes ? distributed p ower s ystems ? home audio ? consumer e lectronics ? network systems ? fpga, dsp and asic supplies ? green electronics note s: 1 . no purposely added lead. fully eu directive 2002/95/ec (rohs) & 2011/65/eu (rohs 2) compliant. 2. see http://www.diodes.com/quality/lead_free.html for more information about diodes incorporateds definitions of hal ogen - and antimony - free, "green" and lead - f ree . 3. halogen - and antimony - free "green products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total br + cl) and <1000ppm antimony compounds. typical applications circuit figure 1 typical application circuit a p 6 5 5 5 2 l 1 1 . 5 h r 1 8 . 2 5 k r 2 2 2 . 1 k c 5 0 . 1 f c 2 4 4 f c 1 2 0 f c 4 8 . 2 n f o n o f f 8 i n 4 s s 1 e n 3 v r e g 5 6 s w 7 b s t 2 f b c 3 1 f 5 g n d i n p u t o u t p u t v o u t 1 . 0 5 v v i n 1 2 v s w v r e g 5 s s e n b s g n d v i n ( t o p v i e w ) 1 2 3 4 8 7 6 5 f b s o - 8 e p
ap65552 document number: ds37306 rev. 2 - 2 2 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 pin description s pin name pin number function so - 8 ep en 1 enable input. en is a digital input that turns the regulator on or off. drive en high to turn on the regulator, drive it low to turn off. pull up with 100k resistor for automatic startup. 1f (typical) capacitor 1f (typical) capacitor is functional block diagram figure 2 functional block diagram
ap65552 document number: ds37306 rev. 2 - 2 3 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 absolute maximum ratings ( note 4) ( @ t a = +25c, unless otherwise specified.) symbol parameter rating unit v in supply voltage - 0.3 to + 20 v v reg5 vreg5 pin voltage - 0.3v to +6 .0 v v sw switch node voltage - 1.0 to v in +0.3 v v bs bootstrap voltage - 0.3 to v sw +6 .0 v v fb feedback voltage - 0.3v to +6 .0 v v en enable/uvlo voltage - 0.3v to +6 .0 v v ss softstart pin - 0.3v to +6 .0 v v gnd gnd pin voltage - 0.3 to + 0.3 v t st storage temperature - 65 to +150 c t j junction temperature +160 c t l lead temperature +260 c esd susceptibility (note 5 ) hbm human body model 2 kv mm machine model 200 v notes: 4 . stresses greater than the 'absolute maximum ratings' specified above may cause permanent damage to the device. these are stress ratings o nly; functional operation of the device at these or any other conditions exceeding those indicated in this specification is not im plied. device reliability may be a ffected by exposure to absolute maximum rating conditions for extended periods of time. 5 . semiconductor devices are esd sensitive and may be damaged by exposure to esd events. suitable esd precautions should be take n when handling and transporting these dev ices. thermal resistance (note 6 ) symbol parameter rating unit ja junction to ambient so - 8ep 70 c/w jc junction to case so - 8ep 30 c/w recommended operating conditions ( note 7) ( @ t a = +25c, unless otherwise specified.) symbol parameter min max unit v in supply voltage 4. 5 1 8 .0 v t j operating junction temperature range - 40 + 12 5 c t a operating ambient temperature range - 40 +85 c note: 6 . test condition: so - 8: device mounted on 1"x1" fr - 4 substrate pcb, 2oz copper, with minimum recommended pad layout. 7 . the device function is not guaranteed outside of the recommended operating conditions.
ap65552 document number: ds37306 rev. 2 - 2 4 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 electrical characteristics (@ t a = +25c, v in = 12v, unless otherwise specified.) parameter symbol conditions min typ max unit supply voltage (vin pin) input voltage v in 4.5 18 v quiescent current i q v fb = 0.85v 0.9 ma shutdown supply current i shdn v en = 0v 3.6 10 a under voltage lockout uvlo threshold v uvlo v in rising test vreg5 voltage 3.45 3.75 4.05 v uvlo hysteresis v hys v in falling test vreg5 voltage 0.19 0.32 0.45 v enable (en pin) en high - level input voltage v enh 1.9 v en low - level input voltage v enl 0.6 v voltage reference (fb pin) feedback voltage v fb v out = 1.05v 0.753 0.765 0.777 v feedback bias current i fb v fb = 0.8v - 0.1 0 0.1 a vreg5 output vreg5 output voltage v vreg5 6.0v ap65552 document number: ds37306 rev. 2 - 2 5 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 typical performance characteristics (@ t a = +25c, v in = 12v, v out = 1.05 v, unless otherwise specified.) 85?c - 40?c 25?c 85?c 25?c - 40?c v in =18v i o = 0 a i o = 1 a v in =12v v in =4.5v
ap65552 document number: ds37306 rev. 2 - 2 6 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 typical performance characteristics ( cont.) ( @ t a = +25c, v in = 12v, v out = 1.05 v, unless otherwise specified.) v o =3.3v v o =2.5v v o =1.8v v o = 3.3v vo=5v vo=3.3v vo=2.5v vo=1.8v vo=1.5v vo=1.05v vo=1.2v v o = 1.8v v o = 1.05v
ap65552 document number: ds37306 rev. 2 - 2 7 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 typical performance characteristics ( cont.) ( @ t a = +25c, v in = 12v, v out = 1.05v, l = 1.5h, c1 = 20f, c2 = 44 f, unless otherwise specified.) steady state test 5 a time - 1 s/div startup through v in no load time - 5 00 s/div startup through v in 5a load time - 5 00 s/div st artup with vreg5 no load time - 1 m s /div shutdown through v in n o load time - 5 0ms/div shutdown through v in 5a load time - 200 s/div startup through v e n no load time - 500 s /div startup through v en 5a load time - 500 s/div short circuit test time - 10 0s/div shutdown through v e n n o load time - 20m s/div shutdown through v e n 5a load time - 2 0 m s/div short circuit recovery time - 50 0s /div 1.05v load transient response time - 1 0 0s/div voltage ripple at output (i o =2a) time - 400n s/div voltage ripple at input (i o =2a) time - 400n s/div vin (12v/div ) v out (1v/div ) iout ( 500ma /div ) sw (1 0v /div ) vin (12v/div ) v out (1v/div ) iout ( 5a /div ) sw (1 0v /div ) vin (12v/div ) v out (1v/div ) iout ( 5a /div ) sw (1 0v /div ) vin (12v/div ) v out (1v/div ) iout ( 500ma /div ) sw (1 0v /div ) v e n (3 v/div ) v out (1v/div ) iout ( 500ma /div ) sw (1 0v /div ) v e n (3 v/div ) v out (1v/div ) iout ( 5a /div ) sw (1 0v /div ) v e n (3 v/div ) v out (1v/div ) iout ( 5a /div ) sw (1 0v /div ) v e n (3 v/div ) v out (1v/div ) iout ( 500ma /div ) sw (1 0v /div ) v out ( 500m v/div ) iout ( 2a /div ) v out ( 500m v/div ) iout ( 2a /div ) vin _ac (500m v/div ) v out_ac (50m v/div ) iout ( 5a /div ) sw ( 5v /div ) en (3 v/div ) v reg5 (5 v/div ) vout ( 500mv /div ) v out_ac ( 50m v/div ) iout ( 2.5a /div ) vout_ac ( 20m v/div ) sw ( 5v /div ) sw ( 5v /div ) vin_ac ( 100m v/div )
ap65552 document number: ds37306 rev. 2 - 2 8 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 application information figure 3 . typical application of ap65 552 pwm operation and adaptive on - time control the ap65 552 is synchronous step - down converters with internal power mosfets. adaptive constant on time (cot) control is employed to provide fast transient response and easy loop stabilization. at the beginning of each cycle, the high - side mosfet is turned on. this mo sfet is turned off after internal one shot timer expires. this one shot is set by the converter input voltage (v in ), and the output voltage (v out ) to maintain a pseudo - fixed frequency over the input voltage range, hence it is called adaptive on - time contro l. the output voltage variation is sensed by fb voltage. the one - shot timer is reset and the high - side mosfet is turned on again when fb voltage falls below the 0.76v. ap65 552 uses an adaptive on - time control scheme and does not have a dedicated in board oscillator. it runs with a pseudo - constant frequency of 650khz by using the input voltage and output voltage to set the on - time one - shot timer. the on - time is inversely proportional to the input voltage and proportional to the output voltage. it can be cal culated using the following equation: v out is the output voltage v in is the input voltage f is the switching frequency after an on - time period, the ap65 552 goes into the off - time period. the off - time period length depends on vfb in most case. it will end when the fb voltage decreases and below 0.76v then the on - time periods is triggered. if the off - time period is less than the minimum off time, the minimum o ff time will be applied, which is about 260ns typical. enable above the en high - level input voltage, the internal regulator is turned on and the quiescent current can be measured above this threshold. the enable (en) input allows the user to control t urning on or off the regulator. to enable the ap65 552 , en must be pulled above the en high - level input voltage and to disable the ap65 552 , en must be pulled below en low - level input voltage. in figure 3, en has a positive voltage through a 100k ? pull - up to vin . no supply input is required for en. soft - start the soft - start time of the ap65 552 is programmable by selecting different c ss value. when the en pin becomes high, the c ss is charged by a 6a current source, generating a ramp signal fed into non - inverting input of the error comparator. reference voltage v ref or the internal soft - start voltage ss whichever is smaller dominates the behavior of the non - inverting inputs of the error amplifier. accordingly, the output voltage will follow the s s signal and ramp up smoothly to its target level. the capacitor value required for a given soft - start ramp time can be expressed as: where c ss is the required capacitor between ss pin and gnd, t ss is the desired soft - start time and v fb is the feedback voltage. ss fb ss c ss t i v ? ? f v ? ? in v out on t e n f b v r e g 5 s s e p g n d s w v i n b s 8 . 2 5 k ? 2 2 . 1 k ? 1 . 5 h e n v o u t v i n v o u t a p 6 5 5 5 2 1 2 3 4 5 6 7 8 8 . 2 n f 1 f 1 0 f 2 2 f 0 . 1 f r 2 r 1 c 5 c 4 l 1 c 6 1 0 f c 1 c 2 2 2 f c 8 c 9 c 7 1 0 0 k ? r 3
ap65552 document number: ds37306 rev. 2 - 2 9 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 application information (cont.) over current protection (ocp) figure 4 shows the over current protection (ocp) scheme of ap65 552 . in each switching cycle, the inductor current is sensed by monitoring the low - side mosfet in the off period. when the voltage between gnd pin and sw pin is smaller than the over current trip level, the ocp will be triggered and the controller keeps the off state. a new switching cycle will begging when the measured voltage is larger than limit voltage. the internal counter is incremented when ocp is triggered. after 16 sequential cycles, the internal ocl (over current logic) thre shold is set to a lower level, reducing the available output current. when a switching cycle occurs where the switch c urrent is below the lower ocl threshold, the counter is reset and ocl limit is returned to higher value. because the r ds(on) of mosfet increases with temperature, v limit has xppm/ o c temperature coefficient to compensate this temperature dependency of r ds( on) . figure 4 over current protection scheme under voltage lockout the ap65 552 provides an under voltage lockout circuit to prevent it from undefined status when startup. the uvlo circuit shuts down the d evice when v in drops below 3.45v. the uvlo circuit has 320mv hysteresis, which means the device starts up again when v reg rise to 3.75v. (non - latch) thermal s hutdown if the junction temperature of the device reaches the thermal shutdown limit of 160c, the ap65 552 shuts itself off, and both hmos and lmos will be turned off. the output is discharge with the internal transistor. when the junction cools to the required level (130c nom inal), the device initiates soft - start as during a normal power - up cycle. setting the output voltage the output voltage can be adjusted from 1.000 to 5v using an external resistor divider. table 1 shows a list of resistor selection for common output voltages. resistor r1 is selected based on a design tradeoff between efficiency and outp ut voltage accuracy. for high values of r1 there is less current consumption in the feedback network. however the trade off is output voltage accuracy due to the bias current in the error amplifier. r1 can be determined by the following equation: figure 5 feedback divider network output voltage (v) r1 (k) r2 (k) 1 6.81 22.1 1.05 8.25 22.1 1.2 12.7 22.1 1.5 21.5 22.1 1.8 30.1 22.1 2.5 49.9 22.1 3.3 73.2 22.1 5 124 22.1 table 1 resistor selection for common output voltages o c c o m p a r a t o r - 2 6 6 m v q 1 q 2 s q r ? ? ? ? ? ? ? ? ? ? ? 1 0.765 out v 2 r 1 r
ap65552 document number: ds37306 rev. 2 - 2 10 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 application information (cont.) inductor calculating the inductor value is a critical factor in designing a buck converter. for most designs, the following equation c an be used to calculate the inductor value; where is the inductor ripple current. and is the buck converter switching frequency. choose the inductor ripple current to be 30% of the maximum load current. the maximum inductor peak current is calculated from: peak current determines the required saturation current rating, which influences the size of the inductor. saturating the ind uctor decreases the converter efficiency while increasing the temperatures of the inductor and the internal mosfets. hence choosing an inductor with appropriate saturation current rating is important. a 1h to 3.3 h inductor with a dc current rating of at least 25% percent higher than the maxim um load current is recommended for most applications. for highest efficiency, the inductors dc resistance should be less than 100m. use a larger inductance for im proved efficiency under light load conditions. the p hase boost can be achieved by adding a n a dditional feed forward capacitor ( c 7 ) in parallel with r1. output voltage (v) c 7 (pf) l1(h) c 8 +c9(f) 1 table 2 recommended component selection input capacitor the input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. the input capacitor has to sustain the ripple current produced during the on time on the upper mosfet. it must hence have a low esr to minimize the losses. the rms current rating of the input capacitor is a critical parameter that must be higher than the rms input current. as a ru le of thumb, select an input capacitor which has rms rating that is greater than half of the maximum load current. due to large di/dt through the input capacitors, electrolytic or ceramics should be used. if a tantalum must be used, it must be surge protected. otherwise, capacitor failure could occ ur. for most applications, greater than 10 f ceramic capacitor is sufficient. output capacitor the output capacitor keeps the output voltage ripple small, ensures feedback loop stability and reduces the overshoot of the output voltage. the output capacitor is a basic component for the fast response of the power supply. in fact, during load transient, for the first few m icroseconds it supplies the current to the load. the converter recognizes the load transient and sets the duty cycle to maximum, bu t the current slope is limited by the inductor value. 2 i i i l load l(max) ? ? l i sw l in out in out f i v ) v (v v l ? ? ? ? ? sw f
ap65552 document number: ds37306 rev. 2 - 2 11 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 application information (cont.) output capacitor (cont.) maximum capacitance required can be calculated from the following equation: esr of the output capacitor dominates the output voltage ripple. the amount of ripple can be calculated from the equation below: an output capacitor with ample capacitance and low esr is the best option. for most applications, a 22 f to 68 f ceramic capacitor will be sufficient. where is the maximum output voltage overshoot. bootstrap capacitor to ensure the proper operation, a ceramic capacitor must be connected between the vbst and sw pin. a 0.1f ceramic capacitor is sufficient. vreg5 capacitor to ensure the proper operation, a ceramic capacitor must be connected between the vreg5 and gnd pin. a 1f ceramic capacitor is sufficient. pc board layout 1. the ap65 552 works at 5a load current, heat dissipation is a major concern in layout the pcb. a 2oz copper in both top and bottom layer is recommended. 2. provide sufficient vias in the thermal exposed pad for heat dissipate to the bottom layer. 3. provide sufficient vias i n the output capacitor gnd side to dissipate heat to the bottom layer. 4. make the bottom layer under the device as gnd layer for heat dissipation. the gnd layer should be as large as possible to provide better thermal effect. 5. make the vin capacitor s as close to the device as possible. 6. make the vreg5 capacitor as close to the device as possible. 7. the thermal pad of the device should be soldered directly to the pcb exposed copper plane to work as a heatsink . the thermal vias in the exposed copper plane increase the heat transfer to the bottom layer. figure 6 pc board layout 2 out 2 out 2 inductor out o v ) v v ( ) 2 i l(i c ? ? ? ? v esr * i vout inductor capacitor ?
ap65552 document number: ds37306 rev. 2 - 2 12 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 ordering information part number package code part marking identification code tape and reel quantity part number suffix ap65 552 s p - 13 s p so - 8 ep marking information (1) so - 8 ep package outline dimensions (all d imensions in mm . ) please see ap02002 at http://www.diodes.com/datasheets/ap02002.pdf for latest version. so - 8ep ( sop - 8l - ep) dim min max typ a 1.40 1.50 1.45 a1 0.00 0.13 - b 0.30 0.50 0.40 c 0.15 0.25 0.20 d 4.85 4.95 4.90 e 3.80 3.90 3.85 e0 3.85 3.95 3.90 e1 5.90 6.10 6.00 e - - 1.27 f 2.75 3.35 3.05 h 2.11 2.71 2.41 l 0.62 0.82 0.72 n - - 0.35 q 0.60 0.70 0.65 all dimensions in mm a p 6 5 5 5 2 x x - 1 3 p a c k i n g p a c k a g e s p : s o - 8 e p 1 3 : t a p e & r e e l gauge plane seating plane e1 e n e b a 45 e0 h f exposed pad bottom view l q c 7 4 3 9 (all sides) a1 d 1 4 8 5 ( t o p v i e w ) a p 6 5 5 5 2 y y w w x l o g o p a r t n o 5 8 4 1 e w w : w e e k : 0 1 ~ 5 2 ; 5 2 y y : y e a r : 0 8 , 0 9 , 1 0 ~ g : g r e e n r e p r e s e n t s 5 2 a n d 5 3 w e e k e : s o - 8 e p b l a n k s o - 8 x x : i n t e r n a l c o d e
ap65552 document number: ds37306 rev. 2 - 2 13 of 13 www.diodes.com november 2014 ? diodes incorporated ap65552 suggested pad layout please see ap02001 at http://www.diodes.com/datasheets/ap02001.pdf for the latest version. important notice diodes incorporated makes no warranty of any kind, express or implied, with regards to this document, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose (and their equivalents under the laws of any jurisdiction). diodes incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or other changes without further notice to this document and any product described herein. diodes incorporated does not assume any liability arising out of the application or use of this document or any product described herein; neither does diodes incorporated convey any license unde r its patent or trademark rights, nor the rights of others. any customer or user of t his document or products described herein in such applications shall assume all risks of such use and will agree to hold diodes incorporated and all the companies whose products are represented on diod es incorporated website, harmless against all damages. diodes incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthor ized sales channel. should customers purchase or use diodes incorporated products for any unintended or unauthorized application , customers shall indemnify and hold diodes incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising ou t of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application. products described herein may be covered by one or more united states, international or foreign patents pending. product nam es and markings noted herein may also be covered by one or more united states, international or fore ign trademarks. this document is written in english but may be translated into multiple languages for reference. only the english version of this document is the final and determinative format released by diodes incorporated. life support diodes incorp orated products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the chief executive officer of diodes incorporated. as used herein: a. life support devices or syst ems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided i n the labeling can be reasonably expected to result in significant injury to the user. b. a critical component is any component in a life support device or system whose failure to perform can be reasonably expe cted to cause the failure of the life support device or to affect its safety or effectiveness. customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support d evices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safe ty - related requirements concerning their products and any use of diodes incorporated products in such safety - critical, life support devices or systems, notwithstanding any devices - or systems - related information or support that may be provided by diodes in corporated. further, customers must fully indemnify diodes incorporated and its representatives against any damages arising out of the use of diodes incorporated products in such safety - critical, life support devices or systems. copyright ? 2014 , diodes incorporated www.diodes.com dimensions value (in mm) c 1.270 x 0.802 x1 3.502 x2 4.612 y 1.505 y1 2.613 y2 6.500 c y1 x1 x y y2 x2

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