e u p 2410 ds2 410 ver 1.1 mar. 2012 1 1.6a, 500khz synchronous step-up converter description the eup2410 is a highly efficient, synchronous, fixed frequency, current-mode step-up converter with output to input disconnect. when eup2410 is disabled, the internal conduction path from sw to out is fully blocked and the out pin is isolated from the battery. this output disconnect feature reduces the shutdown current to typically only 50na. the 500khz switching frequency allows for smaller external components producing a compact solution for a wide range of load currents. highly integration and internal compensation network minimizes as 5 external components, n-channel switch and p-channel synchronous switch integration will greatly improve converter efficiency. internal soft-start function also reduce inrush current. the eup2410 regulates the output voltage up to 6v from either a 2-cell nimh/nicd or a single-cell li-ion battery. the eup2410 is offered in a thin sot23-5 package. typical application circuit features over 90% efficiency 1.6a typical switch current limit 500khz fixed switching frequency output to input disconnect at shutdown mode internal synchronous rectifier internal soft-start internal compensation 50na shutdown current thermal shutdown 5-pin tsot-23 package rohs compliant and 100% lead(pb)-free halogen-free applications gps pnd handheld digital audio digital still and video cameras white led flash figure1. 5v typical application circuit v?mw`r?y?b? w w w . g o f o t e c h . c o m
eup2410 ds2410 ver 1.1 mar. 2012 2 pin configurations package type pin configurations tsot23-5 pin description pin name desc ription 1 fb regulation feedback input. connect to an external resistive voltage divider from the output to fb to set the output voltage. 2 gnd ground. 3 out supply input for the eup2410. connect to the output of the converter. 4 sw output switching node. sw is the drain of the internal low-side n-channel mosfet and high-side p-channel mosfet. connect the inductor to sw to complete the step-up converter. 5 en regulator on/off control input. a logic high input (ven > 1.4v) turns on the regulator. a logic low input (ven < 0.4v) puts the eup2410 into low current shutdown mode. block diagram figure 2. n ~n?t?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com v?mw`r?y?b? w w w . g o f o t e c h . c o m
eup2410 ds2410 ver 1.1 mar. 2012 3 ordering information order number package type mark ing operating temperature range EUP2410OIR1 tsot23-5 n0xxxx -40 c to +85c eup2410 l ead free code 1: lead free, halogen free packing r: tape & reel operating temperature range i: industry standard package type o: tsot n ~n?t?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com v?mw`r?y?b? w w w . g o f o t e c h . c o m
eup2410 ds2410 ver 1.1 mar. 2012 4 absolute maximum ratings fb, out, en to gnd --------------------------------------------------------------------------------------- -0.3v to 6v sw current (note 1) ------------------------------------------------------------------------------------- -1.6a to +1.6a supply voltage v in -------------------------------------------------------------------------------------------- 2.2v to 6v output voltage v out ------------------------------------------------------------------------------------------ 2.5v to 6v operating temperature rang --------------------------------------------------------------------------- -40c to +85c storage temperature rang, t stg ----------------------------------------------------------------------- -65c to +150c thermal resistance ja (tsot) ------------------------------------------------------------------------------------------------ --- 200c/w note1: sw has internal clamp diodes between gnd-sw and sw-out. applications that forward bias these diodes shou l d take care not to exceed the ic's package power dissipation limits. elec trical characteristics v in = 2.4v, v out = 3.5v, c in =10uf, c out = 10f, l1=4.7h, r1 =178k , r2 =100k , t a = -40c to +85c, unless othe rwise noted. typical values are at t a = +25c.) eup2410 parameter conditions min. typ. max. unit supply voltage 2.2 5 v output voltage range 2.5 6 v supply current (shutdown) v en =v out =0v, v sw =5v 0.0 5 1 a supply current v fb =1.3v 0.3 9 ma feedback voltage 1.2 1.25 1.3 v feedback input current v fb =1.2v 50 na switching frequency 310 500 690 khz maximum duty cycle 80 85 90 % en input low voltage 0.4 v en input high voltage 1.4 v en pull down resistor 1 m low-side on resistance v out =3.3v by design 450 m low-side current limit 1 1.6 2 a high-side on resistance v out =3.3v by design 650 m thermal shutdown note 2 160 c thermal shutdown hysteresis note 2 30 c note 2: guaranted by design . n ~n?t?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com v?mw`r?y?b? w w w . g o f o t e c h . c o m
eup2410 ds2410 ver 1.1 mar. 2012 5 2.4 2.6 2.8 3 3.2 3.4 3.6 0 500 1000 1500 load current (ma) output voltage (v) 3.48 3.485 3.49 3.495 3.5 1.8 2.3 2.8 3.3 vin(v) vout(v) iload=0ma iload=400ma typical operating characteristics operating conditions ? v in = 2.4v, v out = 3.5v, c in =10uf, c out = 10 f, l1=4.7h, r1 =178k , r 2 =100k efficiency vs load current line regulation continuous mode operation i load =400ma load regulation continuous mode operation i load =20ma t r ansient response i load =40ma to 400ma step vsw vout iinuctor vsw vout iinuctor iload vout 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1 10 100 1000 load current(ma) efficiency vin=2.4v vin=3.0v n ~n?t?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com v?mw`r?y?b? w w w . g o f o t e c h . c o m
eup2410 ds2410 ver 1.1 mar. 2012 6 1.234 1.236 1.238 1.24 1.242 1.244 1.246 1.248 -40 -20 0 20 40 60 80 100 120 temperature ( ) fb voltage (v) typical operating characteristics (continued) operating conditions ? v in = 2.4v, v out = 3.5v, c in =10uf, c out = 10 f, l1=4.7h, r1 =178k , r2 =100k start up r load =16 maximum duty cycle vs temperature feedback voltage vs temperature 85 85.5 86 86.5 87 87.5 88 -40 -20 0 20 40 60 80 100 120 temperature ( ) max duty cycle (%) ven vsw vout n ~n?t?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com v?mw`r?y?b? w w w . g o f o t e c h . c o m
eup2410 ds2410 ver 1.1 mar. 2012 7 operation the eup2410 uses a 500khz fixed-frequency, curr ent-mode regulation architecture to regulate the output voltage. the eup2410 measures the output voltage through an external resistive voltage divider and compares that to the internal 1.25v reference to generate the error voltage. the current-mode regulator compares the error voltage to the inductor current to regulate the output voltage. the use of current-mode regulation improves transient response and control loop stability. when the eup2410 is disabled (en = low), both power switches are off. there is no current path from sw to out. therefore, the output voltage discharges to ground. when the eup2410 is enabled (en = high), a limited start-current charges the output capacitor through the p-channel mosfet until the output voltage rising to sw, then the part operates in force pwm mode for regulating the output voltage to the target value. at the beginning of each cycle, the n-channel mosfet switch is turned on, forcing the inductor current to rise. the current at the source of the switch is internally measured and converted to a voltage by the current sense amplifier. that voltage is compared to the error voltage. when the inductor current rises sufficiently, the pwm comparator turns off the switch, forcing the inductor current to the output capacitor through the internal p-channel mosfet rectifier, which forces the inductor current to decrease. the peak inductor current is controlled by the error voltage, which in turn is controlled by the output voltage. thus the output voltage controls the inductor current to satisfy the load . soft-start the eup2410 includes a soft-start timer that limits the voltage at the error amplifier output during startup to prevent excessive current at the input. this prevents premature termination of the source voltage at startup due to inrush current. this also limits the inductor current at startup, forcing the input current to rise slowly to the amount required to regulate the output voltage during soft-start. application information component selection setting the output voltage set the output voltage by selecting the resistive voltage divider ratio. the voltage divider drops the output voltage to the 1.25v feedback voltage. use a 100k resistor for r2 of the voltage divider. determine the high-side resistor r1 by the equation: where v out is the output voltage, v fb is the 1.25v fee d back voltage and r2=100k . selecting the input capacitor an input capacitor is required to supply the ac ripple current to the inductor, while limiting noise at the input source. multi-layer ceramic capacitors are the best choice as they have extremely low esr and are available in small footprints. use an input capacitor value of 4.7f or greater. this capacitor must be placed physically close to the device. selecting the output capacitor a single 4.7f to 10f ceramic capacitor usually provides sufficient output capacitance for most applications. larger values up to 22f may be used to obtain extremely low output voltage ripple and improve transient response. the impedance of the ceramic capacitor at the switching frequency is dominated by the capacitance, and so the output voltage ripple is mostly independent of the esr. the output voltage ripple v ripple is c a lculated as: where v in is the input voltage, i load is the load current, c2 i s the capacitance of the output capacitor and f sw is the 500k hz switching frequency. selecting the inductor the inductor is required to force the output voltage higher while being driven by the lower input voltage. a good rule for determining the inductance is to allow the peak-to-peak ripple current to be approximately 30%-50% of the maximum input current. make sure that the peak inductor current is below the minimum current limit at the duty cycle used (to prevent loss of regulation due to the current limit variations). calculate the required inductance value l using the equations: ? ? ? ? ? ? ? ? - = 2r v vv 1r fb fb ou t ( ) sw out in out load ripple f2cv vvi v - = ( ) ifv vvv l sw out in ou t in d - = h = in )max (load out )max(in v iv i )ma x(in i%)50%30(i - = d n ~n?t?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com v?mw`r?y?b? w w w . g o f o t e c h . c o m
eup2410 ds2410 ver 1.1 mar. 2012 8 where i load(max) is the maximum load current, ? i i s the peak-to-peak inductor ripple current and is efficiency. for the eup2410, typically, 4.7h is recommended for most applications. choose an inductor that does not saturate at the peak switch current as calculated above with additional margin to cover heavy load transients and extreme startup conditions. layout considerations high frequency switching regulators require very careful layout for stable operation and low noise. all components must be placed as close to the ic as possible. all feedback components must be kept close to the fb pin to prevent noise injection on the fb pin trace. the ground return of c1 and c2 should be tied close to the gnd pin. see the eup2410 demo board layout for reference. figure 3. 3.3v typical application circuit n ~n?t?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com v?mw`r?y?b? w w w . g o f o t e c h . c o m
eup2410 ds2410 ver 1.1 mar. 2012 9 package information tsot 23-5 millimeters inc h es symbols min. max. min. max. a - 1.00 - 0.039 a1 0.00 0.15 0.000 0.006 d 2.90 0.114 e1 1.60 0.063 e 2.60 3.00 0.102 0.118 l 0.30 0.60 0.012 0.024 b 0.30 0.50 0.012 0.020 e 0.95 0.037 n ~n?t?m?w3^v?mw`r?y?b?g ?pqls? tel: 0755-8398 3377 / 135 9011 2223 http://www.gofotech.com v?mw`r?y?b? w w w . g o f o t e c h . c o m
|
