View EC3293BNT3R_9036416.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

e c 3293b 3a, 18v, 500khz, synchronous step down dc/dc converter e - cmos corp. (ww w .e c mo s . c om.tw) 5 g01 n - r ev. f00 2 1 / 11 general description the ec3293b is a high - frequency, synchronous, rectified, step - down, switch - mode converter with internal power mosfets. it offers a very compact solution to achieve a 3a continuous output current over a wide input supply range, with excellent load and line regulation. the ec3293b has synchronous - mode operation for higher efficiency over the output current - load range. current - mode operation provides fast transient response and eases loop stabilization.protection features include over - c urrent protection and thermal shutdown. the ec3293b requires a minimal number of readily available, standard external components and is available in a space - saving tsot23 - 6l package. features 4.5 v to 18v input voltage output adjustable from 0.6 v to 15v output current up to 3a integrated 85 m /45 m power mosfet switches shutdown current 3 a typical efficiency up to 95% fixed frequency 500khz internal soft start over current protection and hiccup over temperature protection ro hs compliant and 100% lead (pb) free applications distributed power systems networking systems fpga, dsp, asic power supplies notebook computers green electronics or appliance pin assignments 1 2 3 6 4 e n g n d b o o t i n f b t o p v i e w t s o t 2 3 - 6 l 5 s w
e c 3293b 3a, 18v, 500khz, synchronous step down dc/dc converter e - cmos corp. (ww w .e c mo s . c om.tw) 5 g01 n - r ev. f00 2 2 / 11 pin description tsot23 - 6l symbo l description 1 boot high - side gate drive boost input. 2 gnd ground. 3 fb feedback input. 4 en enable input. 5 in power input. 6 sw power switching output. application information note: r5 and c7 are optional. ordering information
e c 3293b 3a, 18v, 500khz, synchronous step down dc/dc converter e - cmos corp. (ww w .e c mo s . c om.tw) 5 g01 n - r ev. f00 2 3 / 11 functional block diagram absolute maximum ratings supply voltage v in C 0.3v to +20v switch node v sw C 0.3v to v in +0.3v boost v boot v sw C 0.3v to v sw +6v all other pins C 0.3v to +6v juncti on temperature +150c lead temperature +260c storage temperature range C 65c to +150c power diss ipation@25 c ..1.2w caution: stresses above those listed in absolute maximum ratings may cause permanent damag e to the device. this is a stress only rating and operation of the device at these or any other conditions above those indicated in the operational sections of this specification is not implied. recommended operating conditions supply voltage v in ... ....4. 5 v to 18v output voltage v out ...... 0. 6 v to v in C 3v operating temperature range ... C 40c to +125c package thermal characteristics tsot23 - 6l: thermal resistance, ja 100c/w thermal resistance, jc 55c/w
e c 3293b 3a, 18v, 500khz, synchronous step down dc/dc converter e - cmos corp. (ww w .e c mo s . c om.tw) 5 g01 n - r ev. f00 2 4 / 11 electrical characteristics (t a = +25c, v in = +12v, unless otherwise noted.) * guaranteed by design, not tested. parameter symbol test conditions min typ max unit supply voltage v in 4. 5 18 v output voltage v out 0 . 6 15 v shutdown supply current v en = 0v 3 6 a supply current v en = 2.0v, v fb = 0.66 v 0. 7 ma feedback voltage v fb 4. 5 v in ea 1000 v/v high - side switch - on resistance * r ds(on)1 85 m ds(on)2 45 m en = 0v, v sw = 0v, t a = +125c 10 a upper switch current limit minimum duty cycle 3 .7 4.3 a lower switch current limit from drain to source 0 a oscillation frequency f osc1 400 500 600 khz short circuit oscillation frequency f osc2 v fb = 0 v 200 250 300 khz maximum duty cycle d max v fb = 0.5v 90 % minimum on time * 90 ns en falling threshold voltage v en falling 1. 1 2 v en rising threshold voltage v en rising 1. 2 2 v input under voltage lockout threshold v in rising 3. 5 v inpu t under voltage lockout threshold hysteresis 200 mv soft - start period 1 ms thermal shutdown * 150 c
e c 3293b 3a, 18v, 500khz, synchronous step down dc/dc converter e - cmos corp. (ww w .e c mo s . c om.tw) 5 g01 n - r ev. f00 2 5 / 11 typical characteristics v in = 12v, v o = 3.3v, l1 = 4.7h, c1 = 10f, c2 = 22 f x 2, t a = +25c, unless otherwise noted. start up & inrush current (load 1a) shut down (i load 1 a ) output ripple ( i load=2a) output ripple ( i load=1a) output ripple ( i load=0a) dynamic load (iload=0.2a_ 1.2 a)
e c 3293b 3a, 18v, 500khz, synchronous step down dc/dc converter e - cmos corp. (ww w .e c mo s . c om.tw) 5 g01 n - r ev. f00 2 6 / 11 short circuit protection efficiency
e c 3293b 3a, 18v, 500khz, synchronous step down dc/dc converter e - cmos corp. (ww w .e c mo s . c om.tw) 5 g01 n - r ev. f00 2 7 / 11 application information overview the ec3293b is a synchronous rectif ied, current - mode, step - down regulator. it regulates input voltages from 4.5v to 18v down to an output voltage as low as 0.6v, and supplies up to 3a of load current. the ec3293b uses current - mode control to regulate the output voltage. the output voltage i s measured at fb through a resistive voltage divider and amplified through the internal trans - conductance error amplifier. the converter uses internal n - channel mosfet switches to step - down the input voltage to the regulated output voltage. since the high side mosfet requires a gate voltage greater than the input voltage, a boost capacitor connected between sw and boot is needed to drive the high side gate. the boost capacitor is charged from the internal 5v rail when sw is low. when the ec3293b fb pin exce eds 20% of the nominal regulation voltage of 0.6v, the over voltage comparator is tripped, forcing the high - side switch off. pins description boot: high - side gate drive boost input. boot supplies the drive for the high - side n - channel mosfet switch. connect a 0.1f or greater capacitor from sw to boot to power the high side switch. in: power input. in supplies the power to the ic, as well as the step - down converter switches. drive in with a 4. 5 v to 18v power source. bypass in to gnd with a suitably large capacitor to eliminate noise on the input to the ic. sw: 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. note that a c apacitor is required from sw to boot to power the high - side switch. gnd: ground. fb: feedback input. fb senses the output voltage to regulate that voltage. drive fb with a resistive voltage divider from the output voltage. the fe edback t hreshold is 0. 6 v. en: enable input. en is a d igital input that turns the regulator on or off. drive en high to turn on the regulator, drive it low to turn it off. pull up with 100k resistor for automatic startup. se tting the output voltage the external resist or divider sets output voltage. the feedback resistor r1 also sets the feedback loop bandwidth through the internal compensation capacitor. (see the typical application circuit). choose the r1 around 10k , and r2 by r2= r1/(vout/0.6 v - 1) u se a network for when vout is low. figure 1 n etwork f b r 1 r 2 v o u t
e c 3293b 3a, 18v, 500khz, synchronous step down dc/dc converter e - cmos corp. (ww w .e c mo s . c om.tw) 5 g01 n - r ev. f00 2 8 / 11 table 1 lists the recommended t - type resistors value for common output voltages. v out (v) r1 (k) (k) out (h) out (f) inductor the inductor is required to supply constant current to the output load while being drive n by the switched input voltage. a larger value inductor will result in less ripple current that will result in lower output ripple voltage. however, the larger value inductor will have a larger physical size, higher series resistance, and/or lower saturat ion current. a good rule for determining the inductance to use is to allow the peak - to - peak ripple current in the inductor to be approximately 30% of the maximum switch current limit. also, make sure that the peak inductor current is below the maximum swit ch current limit. the inductance value can be calculated by: l = [ v out / (f s i l ) ] (1 ? v out /v in ) where v out is the output voltage, v in is the input voltage, f s is the switching frequency, and i l is the peak - to - peak inductor ripple current. choose an inductor that will not saturate under the maximum inductor peak current. the peak inductor current can be calculated by: i lp = i load + [ v out / (2 f s l) ] (1 ? v out /v in ) where i load is the load current. the choice of which style inductor to use mainly depends on the price vs. size require ments and any emi requirements. optional schottky diode during the transition between high - side switch and low - side switch, the body diode of the low - side power mosfet conducts the inductor current. the forward voltage of this bo dy diode is high. an optional schottky diode may be paralleled between the sw pin and gnd pin to improve overall efficiency. table 2 lists example schottky diodes and their manufacturers. table 2: diode selection guide. part number voltage and current rating vendor b130 30v, 1a di odes inc. sk13 30v, 1a diodes inc. mbrs130 30v, 1a international rectifier
e c 3293b 3a, 18v, 500khz, synchronous step down dc/dc converter e - cmos corp. (ww w .e c mo s . c om.tw) 5 g01 n - r ev. f00 2 9 / 11 input capacitor the input current to the step - down converter is discontinuous, therefore a capacitor is required to supply the ac current to the step - down converter while maintaining the dc input voltage. use low esr capacitors for the best performance. ceramic capacitors are preferred, but tantalum or low - esr electrolytic capacitors may also suffice. choose x5r or x7r dielectrics when using ceramic capacitors. since the input capacitor (c1) absorbs the input switching current it requires an adequate ripple current rating. the rms current in the input capacitor can be estimated by: i c1 = i load [ (v out /v in ) (1 ? v out /v in ) ] 1/2 the worst - case condition occurs at v in = 2v out , where i c1 = i load /2. for simplification, choose the input capacitor whose rms current rating greater than half of the maximum load current. the input capacitor can be electrolytic, tantalum or ceramic. when using electrolytic or tantalum capacitors, a small, high quality ceramic capacitor, i.e. 0.1f, should be placed as close to the ic as possible. when using ceramic capacitors, make sure t hat they have enough capacitance to provide sufficient charge to prevent excessive voltage ripple at input. the input voltage ripple for low esr capacitors can be estimated by: v in = [ i load /(c1 f s ) ] (v out /v in ) (1 ? v ou t /v in ) where c1 is the input capacitance value. output capacitor the output capacitor is required to maintain the dc output voltage. ceramic, tantalum, or low esr electrolytic capacitors are recommended. low esr capacitors are pre ferred to keep the output voltage ripple low. the output voltage ripple can be estimated by: v out = [ v out /(f s l) ] (1 ? v out /v in ) [ r esr + 1 / (8 f s c2) ] where c2 is the output capacitance value and r esr is the equivalent series resistance (esr) value of the output capacitor. in the case of ceramic capacitors, the impedance at t he switching frequency is dominated by the capacitance. the output voltage ripple is mainly caused by the capacitance. for simplification, the output voltage ripple can be estimated by: v out = [ v out /(8xf s 2 xlxc2) ] (1 ? v out /v in ) in the case of tantalum or electrolytic capacitors, the esr dominates the impedance at the switching frequency. for simplification, the output ripple can be approximated to: v out = [ v out /(f s l) ] (1 ? v out /v in ) r esr the charact eristics of the output capacitor also affect the stability of the regulation system. the ec3293b can be optimized for a wide range of capacitance and esr values. external bootstrap diode an external bootstrap diode may enhance the efficienc y of the regulator, the applicable conditions of external boot diode are: v out = 5v or 3.3v; and duty cycle is high: d = v out /v in > 65% figure 2: add optio nal external bootstrap diode to enhance efficiency.
e c 3293b 3a, 18v, 500khz, synchronous step down dc/dc converter e - cmos corp. (ww w .e c mo s . c om.tw) 5 g01 n - r ev. f00 2 10 / 11 in these cases, an external boot diode is recommended from the output of the voltage regulator to b oot pin, as shown in figure 2. the recommended ext ernal boot diode is in4148, and the boot capacitor is 0.1 ~ 1f. when vin 6v, for the purpose of promote the efficiency ,it can add an external schottky diode between in and boot pins, a s shown in figure 3. figure 3: add a schot tky diode to promote efficiency when vin 6v. pcb layout guide pcb layout is very important to achieve stable operation. please follow the guidelines below. 1) keep the path of switc hing curre nt short and minimize the loop area formed by input capacitor, high - side mosfet and low - side mosfet. 2) bypass ceramic capacitors are suggested to be put close to the v in pin. 3) ensure all feedback connections are short and direct. place the feedback resistors and compensation components as close to the chip as possible. 4) rout sw away from sensitive analog areas such as fb. 5) connect in, sw, and especially gnd respectively to a large copper area to cool the chip to improve thermal performance and long - term reliability. bom of ec3293b please refer to the typical application circuit. table 3: bom selection table i. l1 r 1 r 2 c 2 vout = 5.0v 6.8 h 23.7 k 3.2k 22 f 2 vout = 3.3v 4.7 h 29.0k 6.4k 22 f 2 vout = 2.5v 4.7h 49.0k 15.5k 22 f 2 vout = 1.8v 3.3h 66.5k 33.3k 22 f 2 vout = 1.2v 2.2 h 81.5k 81.5k 22 f 2 vout = 1. 05 v 2.2 h 85.3k 113.7k 22 f 2 table 4: bom selection table ii. item reference part 1 c1 10f 0.1f
e c 3293b 3a, 18v, 500khz, synchronous step down dc/dc converter e - cmos corp. (ww w .e c mo s . c om.tw) 5 g01 n - r ev. f00 2 11 / 11 package i nformation tsot23 - 6l symbol dimensions in mm dimensions in inch min max min max a 0.700 0.900 0.028 0.035 a1 0.000 0.100 0.000 0.004 b 1.600 1.700 0.063 0.067 b 0.350 0.500 0.014 0.020 c 2.650 2.950 0.104 0.116 d 2.820 3.020 0.111 0.119 e 0.950 bsc 0.037 bsc h 0.080 0.200 0.003 0.008 l 0.300 0.600 0.012 0.024

▲Up To Search▲

Price & Availability of EC3293BNT3R

	To Download EC3293BNT3R Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .