application note: an_SY8003/SY8003a high efficiency 5.5v, 3a continuous, 1mhz synchronous step down regulator general description the SY8003 and SY8003a are high-efficiency, high frequency synchronous step-down dc-dc regulator ic capable of delivering up to 3a output current. the SY8003 and SY8003a operate over a wide input voltage range from 2.7v to 5.5v and integrate main switch and synchronous switch with very low r ds(on) to minimize the conduction loss. low output voltage ripple and small external inductor and capacitor sizes are achieved with 1mhz switching frequency. SY8003 and SY8003a integrate reliable short circuit and over-voltage protection. ordering information SY8003 ( ) temperature code package code optional spec code ordering number package type note SY8003dfc dfn2x2-8 SY8003adfc dfn2x2-8 features ? low r ds(on) for internal switches (top/bottom):110m ? /80m ? ? 3a continuous load current capability ? 2.7-5.5v input voltage range ? high switching frequency minimizes the external components: 1mhz ? internal softstart limits the inrush curre t ? reliable short circuit protection: SY8003: latch off pro ec ion SY8003a: hic-cup m de protection ? reliable over-voltage protection: SY8003: latch off protection SY8003a: no latch off protection ? 100% dropout operation ? rohs compliant and halogen free ? compact package: dfn2x2-8. applications ? lcd tv ? set top box ? net pc ? mini-notebook pc ? access point router typical applications 2 v in : 2.7-5.5v pg 6 l 1 :2.2h v out : 1.8v 3 in lx c in r 1 c 1 c out 22f 200k 22pf 22f 2 fb 1 7 on/ off en r 2 pgnd sgnd 100k 4 8 e f fic ie n c y ( % ) figure 1.schematic diagram figure 2. efficiency vs load current an_SY8003/a rev. 0.9silergy corp. confidential- prepared for customer use only 1
SY8003/SY8003a pinout (top view) fb 1 8 sgnd pg 2 7 en pgnd in 3 6 lx pgnd 4 5 nc part number package type top mark SY8003dfc dfn2x2-8 jd xyz SY8003adfc dfn2x2-8 kw xyz note x=year code, y=week code, z= lot number code. pin name pin number pin description en 7 enable control. pull high to turn on. do not float. pgnd 4/exposed power ground pin. paddle sgnd 8 signal ground pin. lx 6 inductor pin. connect this pin to the switching node of inductor. in 3 power input pin. decouple this pin to gnd pin with at least 10f ceramic cap. pg 2 power good indicator(open drain output). low if the output < 90% of regulation voltage or >120% regulation voltage; high otherwise. connect a pull-up resistor to the input. fb 1 output feedback pin. connect this pin to the center point of the output resistor divider (as shown in figure 1) to progr m the output voltage: vout=0.6*(1+r 1 /r 2 ). nc 5 no connection. absolute maximum ratings (note 1) supply input voltage --------------------------------- ---------------------------------------- ---------------------- -0.3v to 6.0v enable, fb voltage--------------------------------------------- --------------------------------------------- - 0.3v to v in + 0.6v lx voltage----------------------------------------------------------------------------------------------------- - 0.3v *1 to 6v *2 power dissipation, pd @ ta = 25c dfn2x2-8 , ------ -------------------------------------------------------------------1w package thermal resistance (note 2) ja ----------------------------------------------------------------------------------------------------------------- 120c/w jc ------------------------------------------------------------------------------------------------------------------ 8.2c/w junction temperature range ----------------------------------------------------------------------------------------------- 150c lead temperature (s ldering, 10 sec.) ------------------------------------------------------------------------------------ 260c storage temperature range -------------------------------------------------------------------------------------- 65c to 150c (*1) lx voltage tested down to -5v<10ns (*2) lx volta e tested up to +7v<50ns recommended operating conditions (note 3) supply input voltage ------------------------------------------------------------------------------------------------ 2.7v to 5 .5v junction temperature range ------------------------------------------------------------------------------------ - 40c to 125c ambient temperature range ------------------------------------------------------------------------------------- - 40c to 85c an_SY8003/a rev. 0.9silergy corp. confidential- prepared for customer use only 2
SY8003/SY8003a block diagram (SY8003) (SY8003a) an_SY8003/a rev. 0.9silergy corp. confidential- prepared for customer use only 3
SY8003/SY8003a electrical characteristics (v in = 5v, v out = 2.5v, l = 2.2h, c out = 22f, t a = 25c, unless otherwise specified) parameter symbol test conditions min typ max unit input voltage range v in 2.7 5.5 v quiescent current i q i out= 0 , v fb =v ref ? ? nfet ron r ds(on) , n 80 m ? pfet current limit i lim 3.5 a en rising threshol d v enh 1.5 v en falling threshold v enl 0.4 v en leakage curren t i en -1 1 a input uvlo threshold v uvlo 2.5 v uvlo hysteresis v hys 0.2 v oscillator frequency f osc i out =500ma 0.8 1 1.2 mhz pg hi g h dela y time 0.1 1 us pg rising threshold v fb,hv 0.54 v pg under-voltage threshold v fb,lv 0.54 v pg unde r -volta g e dela y time 20 us pg over-voltage threshold v fb,ov 0.69 0.72 0.75 v over-voltage protection threshold v ovp 0.69 0.72 0.75 v over-voltage deglitch timeout t ov 10 20 30 s short circuit protection latch off v scp SY8003dfc 0.24 v threshold short circuit protection delay time t delay-sc 20 s min on time 75 ns max duty cycle 100 % soft start time t ss 0.84 1.2 1.56 ms output discharge switch on r disch 50 ? resistance thermal shutdown temperature t sd 160 c note 1 : stresses beyond the ?absolute maximum ratings? ma y cause permanent damage to the device. these are stress ratings only. functional operation of the device at th ese or any other conditions beyond those indicated in the operational sections of the specification is not implied. exposure to absolute maximum rating conditions for extended pe iods may affect device reliability. note 2 : test condition: device mounted on 2? x 2? fr-4 s ubs trate pcb, 2oz copper, with minimum recommended pad on top layer and thermal vias to bottom layer ground plane. note 3 : the device is not guaranteed to function outside its operating conditions. an_SY8003/a rev. 0.9silergy corp. confidential- prepared for customer use only 4
SY8003/SY8003a typical performance characteristics efficiency (%) ef fic ie nc y ( % ) ef fic ie nc y ( % ) an_SY8003/a rev. 0.9silergy corp. confidential- prepared for customer use only 5
SY8003/SY8003a an_SY8003/a rev. 0.9silergy corp. confidential- prepared for customer use only 6
SY8003/SY8003a operation principle i cin_rms =i out d(1-d) SY8003 is a synchronous buck regulator ic that integrates the pwm control, top and bottom switches on the same die to minimize the switching transition loss and conduction loss. with ultra low r ds(on) power switches and proprietary pwm control, this regulator ic can achieve the highest efficiency and the highest switch frequency simultaneously to minimize the external inductor and capacitor size, and thus achieving the minimum solution footprint. short circuit protection SY8003 after the soft start is over, if the output voltage falls below 40% of the regulation level, ic will turn off both power switches, entering short circuit protection. it will remain in this state until the in or en voltage is recycled. (SY8003a) the frequency is folded back to about 30% of the nominal frequency and the current limit is folded back to 3.0a to prevent the inductor current from runaway and to reduce the power dissipation of the ic under short circuit conditions. over-voltage protection(SY8003 only) if the output voltage exceeds 120% of the regulation level for more than 20s, ic will turn off both power switches and turn on the discharge switch, entering over- voltage protection. it will remain in this state un il in or en voltage is recycled. feedback resistor dividers r1 and r2 : choose r 1 and r 2 to program the proper output voltage. to minimize the power consumption u der light loads, it is desirable to choose large resistance values for both r 1 and r 2 . a value of between 10k and 1m is highly recommended for both resistors if v out is 1.8v, r 1 =100k is chosen, then r 2 can be calculated to be 50k. r 2 0.6v r 1 ( ) . = v out -0.6v v out r 1 fb gnd r 2 input capacitor c in : this ripple current through input capacitor is calculated as: this formula has a maximum at v in =2v out condition, where i cin_rms =i out /2. this simple worst-case condition is commonly used for dc/dc design. with the maximum load current at 3.0a. a typical x5r or better grade ceramic capacitor with 6.3v rating and more than 1 pcs 22 f capacitor can handle this ripple current well. to minimize the potential noise problem, ceramic capacitor should really be placed close to the in and gnd pins. care should be taken to minimize the loop area formed by cin, and in/gnd pins output capacitor c out : the output capacitor is selected to handle the output ripple noise requirements. both steady state ripple and transient requirements must be taken into consideration when selecting this capacitor. for the best performance, it is recommend d to use x5r or better grade ceramic capacitor with 6.3v rating and greater than 22f capacitance. output inductor l: there are several considerations in choosing this inductor. 1) choose the inductance to provide the desired ripple current. it is suggested to choose the ripple current to be about 40% of the maximum output current. the inductance is calculated as: l = v out (1 ? v out /v in, max ) f sw i out, max 40% where fsw is the switching frequency and i out , max is the maximum load current. the SY8003 regulator ic is quite tolerant of different ripple current amplitude. consequently, the final choice of inductance can be slightly off the calculation value without significantly impacting the performance. 2) the saturation current rating of the inductor must be selected to be greater than the peak inductor current under full load conditions. i sat , min > i out , max + v out (1-v out /v in , max ) 2 ? f sw ? l 3) the dcr of the inductor and the core loss at the switching frequency must be low enough to achieve the desired efficiency requirement. it is an_SY8003/a rev. 0.9silergy corp. confidential- prepared for customer use only 7
SY8003/SY8003a desirable to choose an inductor with dcr<50m ? to achieve a good overall efficiency. enable operation pulling the en pin low (<0.4v) will shut down the device. during shut down mode, the SY8003 shutdown current drops to lower than 0.1ua. driving the en pin high (>1.5v) will turn on the ic again. load transient considerations: the SY8003 regulator ic integrates the compensation components to achieve good stability and fast transient responses. in some applications, adding a 22pf ceramic cap in parallel with r 1 may further speed up the load transient responses and is thus recommended for applications with large load transient step requirements. layout design: the layout design of SY8003 regulator is relatively simple. for the best efficiency and minimum noise problems, we should place the following components close to the ic: c in , l, r 1 and r 2 . 1) it is desirable to maximize the pcb copper area connecting to gnd pin to achieve the best thermal and noise performance. if the board space allowed, a ground plane is highly desirable. 2) c in must be close to pins in and gnd. the loop area formed by c in and gnd must be minimized. 3) the pcb copper area associated with lx pin must be minimized to avoid the potential noise problem. 4) the components r 1 , r 2 , and the trace connecting to the fb pin must not be adjacent to the lx net on the pcb layout to avoid the noise problem. 4) if the system chip interfacing with the en pin has a high impedance state at shutdown mode and the in pin is connected directly to a power source such as a liion battery, it is desirable to add a pull down 1m ? resistor between the en a d gnd pins to prevent the noise from falsely turning on the regulator at shutdown mode. an_SY8003/a rev. 0.9silergy corp. confidential- prepared for customer use only 8
SY8003/SY8003a dfn2x2-8 package outline top view si e view bottom view pcb layout (reference only) notes: all dimension in mm all dimension don?t not include mold flash & metal burr an_SY8003/a rev. 0.9silergy corp. confidential- prepared for customer use only 9
SY8003/SY8003a taping & reel specification 1. dfn2x2 3.9/4.1 1.45/1.55 7.7/8.3 feeding direction 2. carrier tape & reel specification for packages reel width reel size package tape width pocket reel size reel trailer leader length qty per types (mm) pitch(mm) (inch) width(mm) length(mm) (mm) reel dfn2x2 8 4 7" 8.4 400 160 3000 3. others: na an_SY8003/a rev. 0.9silergy corp. confidential- prepared for customer use only 10
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