ACE728E 42v input standoff voltage, step- down led driver ver 1. 1 1 d escription the ACE728E is a wide input range, high - efficiency, and high frequency dc - to - dc step - down led driver, capable of delivering up to 1.5a of output current. ACE728E provide 0.15v feedback voltage, which minimize the power loss on the sense resistor in a led driver system. with a fixed switching frequenc y of 600khz, this current mode pwm controlled led driver allows the use of small external components, such as ceramic input and output caps, as wel as small inductors. ace728 e also employs a proprietary control scheme that switches the device into a power save mode during light load, thereby extending the range of high efficiency operation. an ovp function protects the ic itself and its downstream system against input voltage surges. with the hysteresis, en can be controlled by the ambient light - sensitive resistor. ACE728E is available in a space - saving sot23 - 6 package. features ? wide input operating range from 4.5v to 38v ? standoff input voltage: 42v ? high efficiency pfm mode at light load ? capable of delivering 1.5a ? no external compensation needed ? current mode control ? logic control shutdown ? en can be controlled by ambient light ? thermal shutdown and uvlo ? available in sot23 - 6 package application ? ir led driver for surveillance came ra ? led lighting ? constant current source absolute maximum rating p arameter value in voltage ? 0.3v to 42v sw ,en voltage ? 0.3v to vin+0.3 bst voltage ? 0.3v to sw+6 v fb voltage ? 0.3v to 6 v sw to ground current internally limited operating temperature r ange ? 40c to 85 storage temperature range . ? 55c to 150c thermal resistance sot23 - 6 ja jc 220 110 c /w ( n o t e : e x c ee d i n g t h e s e l i m i t s m a y da m age t h e d e v ic e . e x p o s u r e t o a b s o l u t e m a x i m um r a t i n g c o n d i t i o ns f o r l o ng pe r i o ds m a y a ff e c t dev ice r e l i a b i l i t y . )
ACE728E 42v input standoff voltage, step- down led driver ver 1.1 2 typical application packaging type sot - 23- 6 sot - 23 - 6 description function 1 bst bootstr ap pin. connect a 10nf capacitor from this pin to sw. 2 gnd ground pin 3 fb feedback input. connect the led string between output node and this fb pin, and a resistor which is used to define the led current from this fb pin to gnd. the led current is set by 0.155v divided by this resistor. 4 en enable pin for the ic. drive this pin high to enable the part, low to disable. 5 in supply voltage. bypass with a 10f ceramic capacitor to gnd. 6 sw inductor connection. connect an inductor between sw and the regulator output.
ACE728E 42v input standoff voltage, step- down led driver ver 1.1 3 ordering information ace72 8 e xx + h block diagram electrical characteristics v in =v en = 5 , t a =25 parameter conditions min typ max unit input standoff voltage 42 v input voltage rang e 4 38 v input uvlo rising, hysteresis=140mv 3.80 v input ovp rising, hysteresis=1.3v 38 v input supply current v fb =0.85v 0.6 ma input shutdown current 6 ua fb feedback voltage 0.14 0.155 0.170 v fb input current 0.01 ua switching fre quency khz halogen - free gm : sot - 23 - 6 pb - free
ACE728E 42v input standoff voltage, step- down led driver ver 1.1 4 parameter conditions min typ max unit maximum duty cycle 90 % fold - back frequency 170 khz high side switch on resistance i sw =200ma 300 m? high side switch current limit 1.5 a sw leakage current v in =12v, v sw =0, en=gnd 10 ua en input current v in =12v, v en =5v 1 5 ua en input low voltage rising, hysteresis=100mv 0.8 1.1 1.4 v thermal shutdown hysteresis=40 150 typical charac teristics (typical values are at ta=25 c unless otherwise specified) 1led,efficiency vs,lout 6leds,efficiency vs,lout switching waveform switching waveform v in =12v, 6 leds,l out =1a v in =12v, 6 leds,output shortcircuit recovery dso - x - 3014a,my5216141 8:thu nov 13 11:20:46 2014 dso - x - 3 014a,my52161418:thu nov 13 13:57:16 2014
ACE728E 42v input standoff voltage, step- down led driver ver 1.1 5 application information setting led current the current sense resistor is inserted between the anode of led and gnd. the current sense resi stor value is calculated as: r1=0.155v l led f o r 1a led current, choose r1=155 m indu ctor selection the peak - to - peak ripple is limited to 30% of the maximum output current.this places the peak current far enough from the minimum overcurrent trip level to ensure reliable operation while providing enough current ripples for the current mode converter to operate stably. in this case, for 1a maximum output current, the maximum inductor ripple current is 300 ma.the inductor size is estimated as following equation: l ideal =(v in(max) - v out )/i ripple *d min *(1/f osc ). therefore, for v out =5v, the inductor values is calculated to be l = 15h. chose 10h or 15h for v out =3.3v, the inductor values is calculated to be l = 4.9h. chose 4.7h output capacitor selection for most applications a nominal 22f or larger capacitor is suitable. the ACE728E internal compensation is designed for a fixed corner frequency that is equal to = 10khz. for example, for v out =5v, l=15h, c out =22f. the output capacitor keeps output ripple small and ensures control - loop stability. the output capacitor must also have lo w impedance at the switching frequency. ceramic, polymer, and tantalum capacitors are suitable, with ceramic exhibiting the lowest esr and high - frequency impedance. output ripple with a ceramic output capacitor is approximately as follows:vripple = il (peak ) [1 / (2 x f osc x c out )]. if the capacitor has significant esr, the output ripple component due to capacitor esr is as follows: v ripple(esr) = il (peak) x esr input capacitor selection the input capacitor in a dc - to - dc led driver reduces current peaks draw n from the battery or other input power source and reduces switching noise in the controller. the impedance of the input capacitor at the switching frequency should be less than that of the input source so high - frequency switching currents do not pass thro ugh the input source.the output capacitor keeps output ripple small and ensures control - loop stability dimming control a typical application of ACE728E with pwm dimming control is shown at right - hand, please contact ace engineers? technical support for de fining the peripheral r, c values.
ACE728E 42v input standoff voltage, step- down led driver ver 1.1 6 pcb guidelines a typical pcb layout is shown below, which includes pwm dimming function. please do place the input capacitor as close to the chip as possible, and take this as the first priority when drawing the layout. the ground wire can goes underneath the chip and directly get close to the in pin, so that the input capacitor can have shortest wire to both in and gnd pin.
ACE728E 42v input standoff voltage, step- down led driver ver 1.1 7 packing information sot - 23- 6
ACE728E 42v input standoff voltage, step- down led driver ver 1.1 8 not es ace does not assume any responsibility for use as critical components in life support devices or systems without the express written approval of the president and general counsel of ace electronics co., ltd. as sued herein: 1. life support devices or syste ms are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and shoes failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expect ed to result in a significant injury to the user. 2. a critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safet y or effectiveness. ace technology co., ltd. http://www.ace - ele.com/
|
