XF45061 ____________________________________________________________________________________________________________________________ xysemi inc - 1 - www.xysemi.com rev0.1 600ma 4mhz synchronous step-down dc/dc converter general description the XF45061 is a current mode synchronous step-down converter with fixed operating frequency. the supply current is only 130ua at operating and less than 1ua at shutdown. this device is the ideally solution for li-ion battery powered system applications and small size board applications. this device has internal switch, no external diode. it has internal fixed 4mhz frequency and makes application circuit smaller. the XF45061 is available in an adjustable output voltage version. the adjustable version has wide output range from 0.6v to vin. the XF45061 is available in a low profile (1mm) tiny sot23-5 package. features ? 600ma output current ? high efficiency up to 92% ? 2.5v to 5.5 v input range ? adjustable output voltage from 0.6v to vin ? low quiescent current 130ua ? no schottky diode required ? 4mhz constant frequency operation ? low dropout operation: 100% duty cycle ? current mode operation for excellent line and load transient response ? operating temperature: -40 o c to +85 c ? available in tiny sot23-5 package applications ? cell phones smart phones ? 3g rf pa ? wlan gps and bluetooth applications ? dtv tuner applications ? note books,ultra-mobile pcs figure 1. typical application circuit
XF45061 ____________________________________________________________________________________________________________________________ xysemi inc - 2 - www.xysemi.com rev0.1 ordering information part number temp range swiching frequency output voltage (v) output current (a) package pins XF45061_adj -40c to 85c 4mhz adjustable 0.6 sot23-5 5 pin configuration figure 2. pin configuration pin description pin number pin name pin description 1 vin power supply 2 gnd ground. 3 en enable input. when higher than 1.5v, this pin turns the ic on. when lower than 0.3v, this pin turns the ic off. 4 fb feedback input. the voltage at this pin is regulated to 0.6v. connect to the resistor divider between output and ground to set output voltage 5 sw switch output. connect this pin to the inductor. absolute maximum ratings (note: do not exceed these limits to prevent damage to the device. exposure to absolute maximum rating conditions for long periods may affect device reliability.) parameter value unit supply voltage vin -0.3 to 6.5 v fb, en voltage -0.3 to vin+0.3 v sw voltage -0.3 to vin+0.3 v operating ambient temperature -40 to 85 c maximum junction temperature 125 c storage temperature -55 to 150 c lead temperature (soldering, 10 sec) 300 c
XF45061 ____________________________________________________________________________________________________________________________ xysemi inc - 3 - www.xysemi.com rev0.1 electrical characteristics (v in = 3.6v, t a = 25 c unless otherwise specified) parameter symbol test conditions min typ max unit input voltage range v in 2.0 6.0 v uvlo threshold v uvlo v hysteresis =100mv 1.0 1.4 1.8 v operating supply current v fb =0.5v or v out =90%, i load =0 130 170 shutdown supply current i supply v en =0v, v in =4.2v 0.1 1 a t a =25c 0.588 0.6 0.612 0< t a <85c 0.5865 0.6 0.6135 regulated feedback voltage v fb -40c < t a <85c 0.585 0.6 0.615 v reference voltage line regulation v in =2.7v to 5.5v 0.04 0.4 % regulated output voltage v out v out =1.8v; i out =100ma 1.746 1.8 1.854 v output voltage load regulation 0.5 % peak inductor current i peak v in =3v, v fb =0.5v or v out =90%,duty cycle<35% 1 a v fb =0.6v or v out =100% 3.2 4 4.8 mhz oscillator frequency f osc v fb =0 or v out =0 300 khz rds(on) of p-channel fet i sw =100ma 0.3 0.4 ohm rds(on) of n-channel fet i sw =-100ma 0.2 0.3 ohm enable threshold v in = 2.5v to 5.5v 0.3 1 1.5 v enable leakage current -0.1 0.1 a sw leakage current v en = 0v, v sw = 0v or 5v, v in = 5v -1 1 ua
XF45061 ____________________________________________________________________________________________________________________________ xysemi inc - 4 - www.xysemi.com rev0.1 figure 3. functional block diagram functional description normal operation in normal operation the high-side mosfet turns on each cycle and remains on until the current comparator turns it off. at this point the low-side mosfet turns on and remains on until either the end of the switching cycle or until the inductor current approaches zero. the error amplifier adjusts the current comparator?s threshold as necessary in order to ensure that the output remains in regulation. over current operation the part has internal current limit function, which is detected cycle by cycle. when its maximum inductor current limit is reached the charging cycle is terminated, and the low-side mosfet is turned on to allow the inductor current to decrease. under extreme overloads, such as short-circuit conditions, it reduces the oscillator frequency to 300khz to allow further inductor current reduction and to minimize power dissipation. application information inductor selection in normal operation, the inductor maintains continuous current to the output. the inductor current has a ripple that is dependent on the inductance value. the high inductance reduces the ripple current. in general, select the inductance by the following equation: () ? = ?? v out in out in vvv l vfi where out v is the output voltage, in v is the input voltage, f is the switch frequency, and v i is the peak-to-peak inductor ripple current. typically, choose v i as the 30% of the maximum output current.
XF45061 ____________________________________________________________________________________________________________________________ xysemi inc - 5 - www.xysemi.com rev0.1 manuf acture r part number induct ance(u h) drc max (ohms ) dimensions l*w*h(mm3) 1 0.06 2.2 0.09 murata lqh32pn 4.7 0.15 3.2*2.5*1.7 1.5 0.04 2.2 0.07 3.3 0.11 sumid a cdrh3d 16 4.7 0.16 4*4*1.8 table 1. recommend surface mount inductors input capacitor selection the input capacitor reduces input voltage ripple to the converter, low esr ceramic capacitor is highly recommended. for most applications, a 4.7uf capacitor is used. the input capacitor should be placed as close as possible to vin and gnd. output capacitor selection a low esr output capacitor is required in order to maintain low output voltage ripple. in the case of ceramic output capacitors, capacitor esr is very small and does not contribute to the ripple, so a lower capacitance value is acceptable when ceramic capacitors are used. a 10uf ceramic output capacitor is suitable for most applications. output voltage programming in the adjustable version, the output voltage is set by a resistive divider according to the following equation: ?? = ? ?? ?? 21 1 0.6 out v rr typically choose r1=100k and determine r2 from the following equation: connect a small capacitor across r1 feed forward capacitance at the fb pin for better performance. figure 4. typical application circuit for adjustable version
XF45061 ____________________________________________________________________________________________________________________________ xysemi inc - 6 - www.xysemi.com rev0.1 typical performance characteristics (vin=ven=3.6v, l=1.0uh, cin=4.7uf, cout=10uf) efficiency vs. output current vin=2.7v vout=1.8v vout=1.8v vin=3.6v vin=5v oscillator frequency vs. temperature reference voltage vs. temperature steady state waveform iout=0ma vout=1.8v vout 10mv/div 10ms/div vin=3.6v steady state waveform steady state waveform
XF45061 ____________________________________________________________________________________________________________________________ xysemi inc - 7 - www.xysemi.com rev0.1 load transient waveform load transient waveform startup through enable waveform iout=600ma vout=1.8v vout 1v/div 40us/div en 5v/div vin=3.6v load transient waveform
XF45061 ____________________________________________________________________________________________________________________________ xysemi inc - 8 - www.xysemi.com rev0.1 package outline sot23-5 package outline and dimensions dimension in milimeters dimension in inches symb ol min max min max a 1.050 1.250 0.041 0.049 a1 0.000 0.100 0.000 0.004 a2 1.050 1.150 0.041 0.045 b 0.300 0.400 0.012 0.016 c 0.100 0.200 0.004 0.008 d 2.820 3.020 0.111 0.119 e 1.500 1.700 0.059 0.067 e1 2.650 2.950 0.104 0.116 e 0.950 typ 0.037 typ e1 1.800 2.000 0.071 0.079 l 0.700 ref 0.028 ref l1 0.300 0.600 0.012 0.024 0 8 0 8
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