View AME5286_8374742.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

ame 1 AME5286 rev. a.02 3a, 300khz ~ 2mhz synchronous rectified step-down converter n typical application the AME5286 is a synchronous rectified step-down converter with internal power mosfets. it achieves 3a continuous output current over a wide switching frequency range with excellent load and line regulation. current mode operation provides fast transient response and eases of loop stabilization. the circuit protection includes cycle-by-cycle current limiting, output short cir- cuit frequency protection and thermal shutdown. in shut- down mode, the regulator reduces the current less than 1 m a of supply current. this device is available in sop-8/pp and dfn-8c pack- age with exposed pad for low thermal resistance. n general description n features n applications l 3a output current l external soft start l stable with low esr output ceramic capacitors l up to 95% efficiency l less than 1 m a shutdown current l wide switching frequency range from 300khz~2mhz l thermal shutdown l cycle by cycle over current protection l output adjustable from 0.8v to v in l short circuit protection l available in sop-8, dfn-8c package l rohs compliant and halogen free l tv l distributed power systems l pre-regulator for linear regulators figure 2 . 1 v at 3 a step - down regulators figure 1 . 3 . 3 v at 3 a step - down regulators sw r freq 18 k w on off v in 5 v c in 10 m f c 2 optional c 1 680 pf r 3 25 k w in en comp gnd freq r 1 75 k w r 2 24 k w c out 22 m f fb v out 3 . 3 v l 2 . 2 m h pgood ame 5286 p . g r 4 100 k w ss c 3 0 . 1 m f sw r freq 18 k w on off v in 5 v c in 10 m f c 2 optional c 1 680 pf r 3 8 . 2 k w in en comp gnd freq r 1 6 k w r 2 24 k w c out 22 m f fb v out 1 v l 1 . 5 m h pgood ame 5286 p . g r 4 100 k w ss c 3 0 . 1 m f
ame 2 3a, 300khz ~ 2mhz synchronous rectified step-down converter AME5286 rev. a.02 n pin configuration sop-8/pp top view n functional block diagram AME5286-azaadj 1. comp 2. ss 3. en 4. in 5. sw 6. freq 7. fb 8. pg 9. gnd (exposed pad) * die attach: conductive epoxy note. connect exposed pad (heat sink on the back) to gnd. dfn-8c (3mmx3mmx0.75mm) top view AME5286-avaadj 1. comp 2. ss 3. en 4. in 5. sw 6. freq 7. fb 8. pg 9. gnd (exposed pad) * die attach: conductive epoxy otp + + - slope osc enable uvlo pwm in sw pgnd en comp gnd fb - + ea current sense ircmp - + logic driver current limit 0 . 8 v hiccup ss 10 u a + pg pgood uv 0 . 7 v 0 . 4 v freq 8 7 6 1 2 3 4 ame 5286 5 9 1 3 2 4 ame 5286 5 6 7 8 9
ame 3 AME5286 rev. a.02 3a, 300khz ~ 2mhz synchronous rectified step-down converter n pin description pin no. pin name pin description 1 c omp compensation node. comp is used to compensate the regulation control loop. connect a series rc network from comp to gnd to compensate the regulation control loop. in some cases, an additional capacitor from comp to gnd is required. 2 s s soft-start function. connect a capacitor from ss to gnd to set the soft-start period. 3 e n enable. pull en below 0.6v to shut down the regulator. 4 i n power input. in supplies the power to the ic, as well as the step-down converter switches. bypass in to gnd with a suitable large capacitor to eliminate noise on the input to the ic. 5 s w power switching output. sw is the switching node that supplies power to the output. connect the output lc filter from sw to the output load. 6 freq frequency adjust pin. add a resistor from this pin to ground determines the switching frequency. 7 f b feedback input. fb senses the output voltage to regulate that voltage. drive fb with a resistive voltage divider from the output voltage. the feedback reference voltage is 0.8v. 8 p g power-good output. this open-drain output is low when output is out of regulation. 9 g nd ground. connect the exposed pad to gnd.
ame 4 3a, 300khz ~ 2mhz synchronous rectified step-down converter AME5286 rev. a.02 n ordering information AME5286 - x x x xxx pin configuration package type number of pins output voltage a 1. comp v: dfn a: 8 adj: adjustable (sop-8/pp) 2. ss z: sop/pp 3. en 4. in 5. sw 6. freq 7. fb 8. pg 9. gnd a 1. comp (dfn-8c) 2. ss 3. en 4. in 5. sw 6. freq 7. fb 8. pg 9. gnd pin configuration package type number of pins output voltage
ame 5 AME5286 rev. a.02 3a, 300khz ~ 2mhz synchronous rectified step-down converter n absolute maximum ratings n recommended operating conditions n thermal information * measure q jc on backside center of molding compound if ic has no tab. ** mil-std-202g 210f parameter symbol rating unit ambient temperature range t a -40 to +85 junction temperature range t j -40 to +125 storage temperature range t stg -65 to +150 o c parameter package die attach symbol maximum unit sop-8/pp 15 dfn-8c 8.2 sop-8/pp 75 dfn-8c 70 sop-8/pp 1.333 dfn-8c 1.429 maximum junction temperature 150 o c 260 o c o c / w mw lead temperature (soldering 10sec)** thermal resistance* (junction to case) thermal resistance (junction to ambient) internal power dissipation conductive epoxy q j c q ja p d parameter symbol maximum unit supply voltage v in -0.3v to +6v v s witch voltage v sw -1.5v to v in +0.7v v -0.3v to v in +0.3v v hbm 2 kv m m 200 v esd classification en, fb, comp, freq to gnd
ame 6 3a, 300khz ~ 2mhz synchronous rectified step-down converter AME5286 rev. a.02 n electrical specifications v in =5v, t a =25 o c, unless otherwise noted. parameter symbol test condition min typ max units input voltage range v in 3 5.5 v input uvlo v uvlo 2.3 v quiescent current i q v en =5v , v fb =0.7v (no switching) 600 ua shutdown current i shdn v en =0v 1 ua feedback voltage v fb 0.784 0.8 0.816 v feedback current i fb -50 50 na load regulation reg load 0a ame 7 AME5286 rev. a.02 3a, 300khz ~ 2mhz synchronous rectified step-down converter normal operation the AME5286 uses a user adjustable frequency, cur- rent mode step-down architecture with internal mosfet switch. during normal operation, the internal high-side (pmos) switch is turned on each cycle when the oscilla for sets the sr latch, and turned off when the comparator resets the sr latch. the peak inductor current at which comparator resets the sr latch is controlled by the out- put of error amplifier ea. while the high-side switch is off, the low-side switch turns on until either the inductor current starts to reverse or the beginning of the next switching cycle. dropout operation the output voltage is dropped from the input supply for the voltage which across the high-side switch. as the input supply voltage decreases to a value approaching the output voltage, the duty cycle increases toward the maximum on-time. further reduction of the supply volt- age forces the high-side switch to remain on for more than one cycle until it reaches 100% duty cycle. power good output the AME5286 power good output is an open-drain out- put and requires a pull up resistor. when the output volt- age is 12.5% above or 12.5% below its set voltage, pgood will be pulled low. it is held low until the output voltage returns to within the allowed tolerances once more. during soft-start, pgood is actively held low and is only allowed to transition high when soft-start is over and the output voltage reaches 87.5% of its set voltage. soft-start the AME5286 contains an external soft-start clamp that gradually raises the output voltage. the soft-start timing is programmed by the external capacitor between ss pin and gnd. the chip provides an internal charge current for the external capacitor. if 10nf capacitor is used to set the soft-start, the period will be 800us(typ.). n detailed description hiccup mode during hiccup mode, the AME5286 disables the high- side mosfet and begins a cool down period of 8000us . at the conclusion of this cool down period, the regula- tor performs an external 800us identical to the soft start at turn-on. ( if 10nf capacitor is used to set the soft-start) under voltage protection under voltage protection will activate once the feed- back voltage falls below 0.4v, the operating frequency is switched to 1/10 of normal switching frequency and after four-times hiccup mode counted, the internal high-side power switch will be turned off, and latched, unless re- start the power supply. over current protection the AME5286 cycle-by-cycle limits the peak inductor current to protect embedded switch from damage. hence the maximum output current (the average of inductor cur- rent) is also limited. in case the load increases, the in- ductor current is also increase. whenever the current limit level is reached, the output voltage can not be regu- lated and starting to drop. over temperature protectiion the in most applications the AME5286 does not dissi- pate much heat due to high efficiency. but, in applica- tions where the AME5286 is running at high ambient tem- perature with low supply voltage and high duty cycles, such as in dropout, the heat dissipated may exceed the maximum junction temperature of the part. if the junc- tion temperature reaches approximately 160 o c, the inter- nal high-side power switch will be turned off and the sw switch will become high impedance.
ame 8 3a, 300khz ~ 2mhz synchronous rectified step-down converter AME5286 rev. a.02 inductor selection for most applications, the value of the inductor will fall in the range of 2.2 m h to 4.7 m h. its value is chosen based on the desired ripple current. large value inductors lower ripple current and small value inductors result in higher ripple currents. higher v in or v out also increase the ripple current d i l : a reasonable inductor current ripple is usually set as 1/ 3 to 1/5 of maximum out current. 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. for better efficiency, choose a low dcr in- ductor. capacitor selection in continuous mode, the source current of the top mosfet is a square wave of duty cycle v out /v in . to prevent large voltage transients, a low esr input capaci- tor sized for maximum rms current must be used. the maximum rms capacitor current is given by: c in requires i rms this formula has a maximum at v in =2v out , where i rms =i out /2. for simplification, use an input capacitor with a rms current rating greater than half of the maximum load current. the selection of c out is driven by the required effective series resistance (esr). typically, once the esr re- quirement for c out has been met, the rms current rating generally far exceeds the i ripple(p-p) requirement. the output ripple v out is determined by: ? ? ? ? ? - = d in out out l v v v l f i 1 1 ( ) in out in out omax v v v v i - @ ? ? ? ? ? + d @ d out l out fc esr i v 8 1 for a fixed output voltage, the output ripple is highest at maximum input voltage since d i l increases with input voltage. when choosing the input and output ceramic capaci- tors, choose the x5r or x7r dielectric formulations. these dielectrics have the best temperature and voltage char- acteristics of all the ceramics for given value and size output voltage programming the AME5286 output voltage of the AME5286 is set by a resistive divider according to the following formula: some standard value of r1, r2 for most commonly used output voltage values are listed in table 1. . 2 1 1 8 . 0 volt r r v out ? ? + = v out (v) r1(k w ) r2(k w ) 1.1 7.5 20 1.2 10 20 1.5 17.4 20 1.8 30 24 2.5 51 24 3.3 75 24
ame 9 AME5286 rev. a.02 3a, 300khz ~ 2mhz synchronous rectified step-down converter loop compensation the AME5286 employs peak current mode control for easy use and fast transient response. peak current mode control eliminates the double pole effect of the output lc filter. it greatly simplifies the compensation loop design. with peak current mode control, the buck power stage can be simplified to be a one-pole and one-zero system in frequency domain. the pole can be calculated by: the zero is a esr zero due to output capacitor and its esr. it can be calculated by: where c out is the output capacitor, r l is load resis- tance; esr cout is the equivalent series resistance of output capacitor. the compensation design is to shape the converter close loop transfer function to get desired gain and phase. for most cases, a series capacitor and resistor network con- nected to the comp pin sets the pole-zero and is ad- equate for a stable high-bandwidth control loop. in the AME5286, fb pin and comp pin are the invert- ing input and the output of internal transconductance er- ror amplifier (ea). a series rc and cc compensation network connected to comp pin provides one pole and one zero: for r c << a ea /g ea l out p r c f = p 2 1 1 cout out z esr c f = p 2 1 1 c c z ea c ea ea ea c c p r c f a c g g a r c f = ? ? ? ? ? ? + = p p p 2 1 2 2 1 2 2 where g ea is the error amplifier transconductance a ea is the error amplifier voltage gain r c is the compensation resistor c c is the compensation capacitor the desired crossover frequency f c of the system is defined to be the frequency where the control loop has unity gain. it is also called the bandwidth of the con- verter. in general, a higher bandwidth means faster re- sponse to load transient. however, the bandwidth should not be too high because of system stability concern. when designing the compensation loop, converter stability un- der all line and load condition must be considered. usu- ally, it is recommended to set the bandwidth to be less than 1/10 of switching frequency. using selected cross- over frequency, f c , to calculate r c : where g cs is the current sense circuit transconductance. the compensation capacitor c c and resistor r c together make zero. this zero is put some- where close to the pole f p1 of selected frequency. c c is selected by: checking transient response the regulator loop response can be checked by look- ing at the load transient response. switching regulators take several cycles to respond to a step in load current. when a load step occurs, v out immediately shifts by an amount equal to ( d i load x esr), where esr is the effec- tive series resistance of c out . d i load also begins to charge or discharge c out , which generates a feedback error sig- nal. the regulator loop then acts to return v out to its steady state value. during this recovery time v out can be moni- tored for overshoot or ringing that would indicate a stabil- ity problem. cs ea out fb out c c g g c v v f r = p 2 c l out c r r c c =
ame 10 3a, 300khz ~ 2mhz synchronous rectified step-down converter AME5286 rev. a.02 efficiecny considerations although all dissipative elements in the circuit produce losses, one major source usually account for most of the losses in AME5286 circuits: i 2 r losses. the i 2 r loss dominates the efficiency loss at medium to high load currents. the i 2 r losses are calculated from the resistances of the internal switches, r sw , and external inductor r l . in continuous mode, the average output current flowing through inductor l is "chopped" between the main switch and the synchronous switch. thus the series resistance looking into the sw pin is a function of both top and bottom mosfet r ds(on) and the duty cycle (d) as fol- lows: r sw = (r ds(on)top )(d) + (r ds(on)bottom )(1-d) the r ds(on) for both the top and bottom mosfets can be obtained from electrical characteristics table. thus, to obtained i 2 r losses, simply add r sw to r l and multiply the result by the square of the average output current. other losses including c in and c out esr dissipative losses and inductor core losses generally account for less than 2% total additional loss. thermal considerations in most application the AME5286 does not dissipate much heat due to its high efficiency. but, in applications where the AME5286 is running at high ambient tempera- ture with low supply voltage and high duty cycles, such as in dropout, the heat dissipated may exceed the maxi- mum junction temperature of the part. if the junction temperature reaches approximately 160 o c, both power switches will be turned off and the sw switch will be- come high impedance.
ame 11 AME5286 rev. a.02 3a, 300khz ~ 2mhz synchronous rectified step-down converter n typical operating circuit table 1. recommended components selectin for fsw = 2mhz figure 3. AME5286 regulators layout diagram v out (v) c in ( m f) r1(k w ) r2(k w ) r3(k w ) c1 ( pf ) l( m h) c out ( m f ) 3.3 10 75 24 25 680 2.2 22 2.5 10 51 24 20 680 2.2 22 1.8 10 30 24 15 680 1.5 22 1.5 10 21 24 13 680 1.5 22 1.2 10 12 24 11 680 1.5 22 1 10 6 24 8.2 680 1.5 22 ame 5286 sw r freq v in 2 . 5 v to 5 v c in 10 m f c 2 optional c 1 r 3 in en comp freq r 1 r 2 c out fb v out l 4 8 1 5 7 6 gnd 9 ( exposed pad ) pgood r 4 100 k w 3 chip enable ss 2 css ss comp en v in pg fb freq sw l 1 r 2 r 1 v out r 3 r freq c out c 1 1 2 3 4 8 7 6 5 gnd 9 gnd gnd v out gnd place the feedback resistors as close to the ic as possible place the input and output capacitors as close to the ic as possible sw should be connected to inductor by wide and short trace , and keep sensitive components away from this trace css the ground area must provide adequate heat dissipating area to the thermal pad and using multiple vias to help thermal dissipation . c in gnd c in must be placed between v in and gnd as close as possible
ame 12 3a, 300khz ~ 2mhz synchronous rectified step-down converter AME5286 rev. a.02 n characterization curve efficiency vs. output current efficiency vs. output current efficiency vs. output current efficiency vs. output current output current ( ma ) e f f i c i e n c y ( % ) 0 10 20 30 40 50 60 70 80 90 100 0 500 1000 1500 2000 v out = 1 . 0 v v out = 1 . 2 v v out = 1 . 8 v v out = 2 . 5 v v out = 3 . 3 v v in = 5 v r freq = nc 100 output current ( ma ) e f f i c i e n c y ( % ) 0 10 20 30 40 50 60 70 80 90 0 500 1000 1500 2000 v out = 1 . 0 v v out = 1 . 2 v v out = 1 . 8 v v out = 2 . 5 v v out = 3 . 3 v v in = 5 v r freq = 47 k 0 10 20 30 40 50 60 70 80 90 100 0 500 1000 1500 2000 output current ( ma ) e f f i c i e n c y ( % ) v out = 3 . 3 v v out = 2 . 5 v v out = 1 . 8 v v out = 1 . 2 v v out = 1 . 0 v v in = 5 v r freq = 30 k 0 10 20 30 40 50 60 70 80 90 100 0 500 1000 1500 2000 output current ( ma ) e f f i c i e n c y ( % ) v out = 3 . 3 v v out = 2 . 5 v v out = 1 . 8 v v out = 1 . 2 v v out = 1 v v in = 5 v r freq = 18 k
ame 13 AME5286 rev. a.02 3a, 300khz ~ 2mhz synchronous rectified step-down converter n characterization curve (contd.) load step load step load step load step 1) v out = 200mv/div 2) i l = 2a/div 1) v out = 200mv/div 2) i l = 2a/div 1) v out = 200mv/div 2) i l = 2a/div 1) v out = 200mv/div 2) i l = 2a/div time ( 200 m sec / div ) 2 1 v in = 3 . 3 v v out = 1 . 0 v i out = 1 a to 3 a time ( 200 m sec / div ) 2 1 v in = 3 . 3 v v out = 1 . 8 v i out = 1 a to 3 a time ( 200 m sec / div ) 2 1 v in = 5 . 0 v v out = 1 . 0 v i out = 1 a to 3 a time ( 200 m sec / div ) 2 1 v in = 5 . 0 v v out = 3 . 3 v i out = 1 a to 3 a
ame 14 3a, 300khz ~ 2mhz synchronous rectified step-down converter AME5286 rev. a.02 n characterization curve (contd.) power on from en power off from en power on from v in power off from v in 1 2 3 4 time ( 400 us / div ) time ( 2 . 0 ms / div ) 2 1 3 4 2 1 3 4 time ( 2 . 0 ms / div ) 1) en= 5v/div 2) v sw = 5v/div 3) v out = 1v/div 4) i l = 1a/div 1) en= 5v/div 2) v sw = 5v/div 3) v out = 1v/div 4) i l = 1a/div 1) v in = 5v/div 2) v sw = 5v/div 3) v out = 1v/div 4) i l = 1a/div 1) v in = 5v/div 2) v sw = 5v/div 3) v out = 1v/div 4) i l = 1a/div 1 2 3 4 time ( 400 us / div )
ame 15 AME5286 rev. a.02 3a, 300khz ~ 2mhz synchronous rectified step-down converter n characterization curve (contd.) frequency vs. supply voltage frequency vs. output current v fb vs. temperature frequency vs. temperature 0 . 77 0 . 78 0 . 79 0 . 80 0 . 81 0 . 82 40 25 10 5 20 35 50 65 80 95 110 125 temperature ( c ) v f b ( v ) 150 200 250 300 350 400 450 3 . 5 4 4 . 5 5 5 . 5 input voltage ( v ) f r e q u e n c y ( k h z ) v out = 3 . 3 v 200 210 220 230 240 250 260 270 280 290 300 100 300 500 700 900 1100 1300 1500 1700 1900 i out ( ma ) f r e q u e n c y ( k h z ) v in = 5 . 0 v v out = 3 . 3 v 150 200 250 300 350 400 450 40 25 10 5 20 35 50 65 80 95 110 125 temperature ( c ) f r e q u e n c y ( k h z ) v in = 5 v
ame 16 3a, 300khz ~ 2mhz synchronous rectified step-down converter AME5286 rev. a.02 power good short circuit test i out 2 a / div v out 2 v / div time ( 100 ms / div ) v in = 5 . 0 v v out = 3 . 3 v steady state test steady state test n characterization curve (contd.) 1 2 3 4 time ( 2 ms / div ) 1) en= 5v/div 2) pg= 5v/div 3) v out = 1v/div 4) i l = 2a/div 1) v out = 10mv/div 2) v sw = 2v/div 1) v out = 10mv/div 2) v sw = 2v/div 2 1 v in = 5 v v out = 1 . 1 v i out = 3 a time ( 400 ns / div ) 2 1 time ( 400 ns / div ) v in = 5 v v out = 3 . 3 v i out = 3 a
ame 17 AME5286 rev. a.02 3a, 300khz ~ 2mhz synchronous rectified step-down converter n tape and reel dimension dfn-8c (3mmx3mmx0.75mm) w p pin 1 a m e a m e carrier tape, number of components per reel and reel size sop-8/pp carrier tape, number of components per reel and reel size pin 1 w p a m e a m e package carrier width (w) pitch (p) part per full reel reel size dfn-8c (3x3x0.75mm) 12.00.1 mm 4.00.1 mm 3000pcs 3301 mm package carrier width (w) pitch (p) part per full reel reel size sop-8/pp 12.00.1 mm 4.00.1 mm 2500pcs 3301 mm
ame 18 3a, 300khz ~ 2mhz synchronous rectified step-down converter AME5286 rev. a.02 n package dimension sop-8/pp b e e e 2 c front view side view top view d 1 e 1 l 1 d a 1 a a 2 ? pin 1 min max min max a 1.350 1.750 0.053 0.069 a1 0.000 0.150 0.000 0.006 a2 1.350 1.600 0.053 0.063 c 0.100 0.250 0.004 0.010 e 3.750 4.150 0.148 0.163 e1 5.700 6.300 0.224 0.248 l1 0.300 1.270 0.012 0.050 b 0.310 0.510 0.012 0.020 d 4.720 5.120 0.186 0.202 e q 0 o 8 o 0 o 8 o e2 2.150 2.513 0.085 0.099 d1 2.150 3.402 0.085 0.134 1.270 bsc 0.050 bsc symbols millimeters inches
ame 19 AME5286 rev. a.02 3a, 300khz ~ 2mhz synchronous rectified step-down converter n package dimension (contd.) dfn-8c (3mmx3mmx0.75mm) min max min max a 0.700 0.800 0.028 0.031 d 2.900 3.100 0.114 0.122 e 2.900 3.100 0.114 0.122 e 0.600 0.700 0.024 0.028 d1 2.200 2.400 0.087 0.094 e1 1.400 1.600 0.055 0.063 b 0.180 0.320 0.007 0.013 l 0.375 0.575 0.015 0.023 g 0.153 0.253 0.006 0.010 g1 0.000 0.050 0.000 0.002 symbols millimeters inches top view bottom view rear view e d e a g g 1 b l e 1 d 1 pin 1 identification
life support policy: these products of ame, inc. are not authorized for use as critical components in life-support devices or systems, without the express written approval of the president of ame, inc. ame, inc. reserves the right to make changes in the circuitry and specifications of its devices and advises its customers to obtain the latest version of relevant information. ? ame, inc. , december 2012 document: tu003-ds5286-a.02 corporate headquarter ame, inc. 8f, 12 wenhu st., nei-hu taipei 114, taiwan . tel: 886 2 2627-8687 fax: 886 2 2659-2989 www.ame.com.tw e-mail: sales@ame.com.tw

▲Up To Search▲

Price & Availability of AME5286

	To Download AME5286 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .