AIC2300 400ma synchronous pwm step-down dc/dc converter analog integrations corporation si-soft research center ds-2300g-01 20120531 3a1, no.1, li-hsin rd. i , science park , hsinchu 300, taiwan , r.o.c. tel: 886-3-5772500 f ax: 886-3- 5772510 www. analog.com.tw 1 ? features ? 2.5v to 5.5v input voltage range ? 400ma guaranteed output current ? up to 95% efficiency ? low r ds(on) internal switche: 280m ? ? no schottky diode required ? 100% duty cycle in low dropout operation ? operating frequency: 1.5mhz ? accurate reference 0.6v provides low output voltages ? applications ? lcd tv ? multi-function peripheral ? cellular phones ? cpu i/o supplies ? cordless phones ? pdas and handy-terminals ? battery-operated devices (1 li-ion or 3 nimh/ nicd) ? description the AIC2300 is a low-noise, pulse-width- modulated (pwm) , dc-dc step-down converter. the device is available in an adjustable version and fixed output voltages of 1.0v, 1.2v, 1.8v, and 3.3v. the device features an internal synchronous rectifier for high efficiency; it requires no external schottky diode. shutdown mode places the device in standby, reducing supply current to under 1a. other features of the AIC2300 include high efficiency, low dropout voltage,short circuit protection, over temperature protection, and over voltage protection. it is available in a small 5 pins sot- 23 package. ? applications circuit fig. 1 fixed step-down dc/dc converter
AIC2300 2 fig. 2 adjustable step-down dc/dc converter ? ordering information exam ple: AIC2300-33gv5tr ? 3.3v output version, in sot-23-5 green package & tape & reel packing type AIC2300gv5tr ? ad ju sta ble ve rsio n, in sot-23-5 green package & tape & reel packing type pin configuration top view vou t gn d en 3 21 4 5 lx pac king t ype tr: tape & reel bg: bag pac kage type v5: sot-23-5 g: green package out put v oltage defaul t: ad j. - 10: 1.0v -1 2: 1.2v -1 8: 1.8v -3 3: 3.3v fixed version top view fb gnd en 3 21 4 5 lx a djusta ble ve rsion vin vin sot-23-5 sot-23-5 ai c2300 -xx x xx xx
AIC2300 3 ? ordering information (continuous) ? marking (fixed version) part no. marking AIC2300-10gv5 hp10g AIC2300-12gv5 hp12g AIC2300-18gv5 hp18g AIC2300-33gv5 hp33g ? marking (adjustable version) part no. marking AIC2300gv5 2300g ? absolute maximum ratins vin, lx voltage 6v en, fb pin voltage -0.3 v to v in operating ambient temperature range t a -40? c to 85 ? c operating maximum junction temperature t j 150 ? c storage temperature range t stg -65? c to 150 ? c lead temperature (soldering 10 sec.) 260 ? c thermal resistance junction to case sot-23-5 115 ? c/w thermal resistance junction to ambient sot-23-5 250 ? c/w (assume no ambient airflow, no heatsink) absolute maximum ratings are those values beyond which the life of a device may be impaired.
AIC2300 4 ? electrical characteristics (t a =25 ? c, v in =3.6v unless otherwise specified.) (note 1) parameter conditions symbol min typ max units input voltage range v in 2.5 5.5 v output adjustment range v out 0.6v v in -0.3v v reference voltage v ref 0.588 0.6 0.612 v fb input current v fb = v in i fb -50 50 na p-channel on-resistance i out = 0.2a p rds(on) 280 390 m ? n-channel on-resistance i out = 0.2a n rds(on) 250 390 m ? lx leakage current v lx =0v or v lx =3.6v -1 1 ua peak inductor current v in = 5v i pk 0.5 0.6 a quiescent current i out = 0ma, v fb =0.78v i q 65 85 ? a shutdown supply current en = gnd i shdn 0.1 1 ? a en high-level input voltage v in =2.5v to 5.5v v en_h 1.5 v en low-level input voltage v in =2.5v to 5.5v v en_l 0.4 v oscillator frequency f osc 1.2 1.5 1.8 mhz maximum duty cycle d max 100 % thermal shutdown temperature 150 c thermal shutdown hysteresis 25 c note 1: specifications are production tested at t a =25 ? c. specifications over the -40? c to 85 ? c operating tem- perature range are assured by design, characteriza tion and correlation with statistical quality con- trols (sqc).
AIC2300 5 ? typical performance characteristics fig. 3 efficiency vs. output current fig. 4 efficiency vs. output current fig. 5 oscillator frequency vs. temperature fig. 6 oscillator frequency vs. input voltage fig. 7 r ds(on) vs. input voltage fig. 8 supply current vs. input voltage vout=1.8v vin=2.5v vin=3.3v vin=5v vout=3.3v vin=5v
AIC2300 6 ? typical performance characteristics (continuous) fig. 9 current limit vs. input voltage fig. 10 output voltage vs. temperature fig. 11 load transient response fig. 12 load transient response fig. 13 load transient res ponse fig. 14 load transient response
AIC2300 7 ? block diagram functional block diagram of AIC2300 ? pin descriptions pin name pin function nc no internal connect (floating or connecting to gnd). en chip enable (active high). vin power input. lx pin for switching. gnd ground. fb/vout feedback/output voltage pin.
AIC2300 8 ? application information operation the AIC2300 is a low-noise step-down dc/dc converter with current-mode pwm control architecture. it features an internal synchronous rectifier, which eliminates the external schottky diode and increases efficiency. during normal operation, the AIC2300 can regulate its output voltage through a feedback control circuit, which is composed of an error amplifier; a current comparator and several control signal generators. by comparing the feedback voltage to the reference voltage of 0.6v, the error amplifier varies its output voltage. the output volt age of the error amplifier is compared with the summing signal of current sensing signal and slope compensation signal to determine the duty cycle of internal main power switch (p-channel mosfet). while the main power switch is turned on, the synchronous power switch (n-channel mosfet) will be turned off through anti-short-through block. similarly, when the main power switch is turned off, the synchronous power switch will be turned on until the inductor current starts to reverse or the beginning of the next switching cycle. in order to achieve better efficiency and prevent overcharging the output capacitor. current limitation the AIC2300 provides current limit function by using an internal sensing resistor. when the main power switch turns on, current follows through the internal sensing resistor. and current amplifier senses the voltage, which crosses the resistor, and amplifies it. while the sensed voltage gets higher than reference voltage, the current limitation function is activated. while the current limitation function is activated, the duty cycle will be reduced to limit the output power to protect the internal power switches. short circuit protection while the output is short ed to ground, the switching frequency of AIC2300 will be reduced to one third of the normal switching frequency. this lower switching frequency ensures the inductor current has more time to discharge, thereby pr eventing inductor current runaway. the switching frequency will automatically return to its designed value while short circuit condition is released. shutdown by connecting the en pin to gnd, the AIC2300 can be shut down to reduce the supply current to 0.1 ? a (typical). at this operati on mode, the output voltage of step-down converter is equal to 0v. 100% duty cycle operation when the input voltage approac hes the output voltage, the AIC2300 smoothly transits to 100% duty cycle operation. this allows AIC2300 to regulate the output voltage until AIC2300 completely enters 100% duty cycle operation. in 100% dut y cycle mode, the output voltage is equal to the input voltage minus the voltage, which is the drop across the main power switch. the AIC2300 achieves 100% duty cycle operation by extending the turn-on time of the main power switch. if the summing signal of curr ent sensing signal and slope compensation signal does not reach the output voltage level of the error amplifier at the end of 90% switching period, the main power switch is continuously turned on and the oscillator remains off until the summing signal of current sensing signal and slope compensation signal reaches the output voltage level of the error amplifier. after the summing signal of current sensing signal and slope compensation signal reaches the output voltage leve l of the error amplifier, the main power switch is turned off and the synchronous power switch is turned on for a constant off time. at the end of the constant off time, the next switching cycle is begun. while the input voltage approaches the output voltage, the switching
AIC2300 9 frequency decreases gradually to smoothly transit to 100% duty cycle operation. if input voltage is very close to output voltage, the switching mode goes from pure pwm mode to 100% duty cycle operation. duri ng this transient state mentioned above, large output ripple voltage may appear on output terminal. components selection inductor the inductor selection depends on the current ripple of inductor, the input voltage and the output voltage. ? ? ? ? ? ? ? ? ? ?? ? in out losc out v v 1 if v l accepting a large current ripple of inductor allows the use of a smaller inductance. however, higher current ripple of inductor can cause higher output ripple voltage and large core loss. by setting an acceptable current ripple of inductor, a suitable inductance can be obtained from above equation. in addition, it is important to ensure the inductor saturation current exceeds the peak value of inductor current in application to prevent core saturation. the peak value of inductor current can be calculated according to the following equation. ?? ? ? ? ? ? ? ? ? ? ?? ? ? in out osc out maxout peak v v 1 lf2 v ii input capacitor and output capacitor to prevent the high input voltage ripple and noise resulted from high frequency switching, the use of low esr ceramic capacitor for the maximum rms current is recommended. the approximated rms current of the input capacitor can be calculated according to the following equation . ?? 12 i v vvv i i 2 l 2 in out inout 2 )max(out cinrms ? ? ? ? ? the selection of output capacitor depends on the required output voltage ripple. the output voltage ripple can be expressed as: l out osc l out iesr cf8 i v ??? ?? ? ?? for lower output voltage ripple, the use of low esr ceramic capacitor is recommended. the tantalum capacitor can also be used well, but its ers is larger than that of ceramic capacitor. when choosing the input and output ceramic capacitors, x5r and x7r types are recommended because they retain their capacitance over wider ranges of voltage and temperature than other types. output voltage programming (AIC2300 adjustable version only) by connecting a resistive divider r 1 and r 2, the output voltage of AIC2300 step-down converter can be set. v out can be calculated as: ? ? ? ? ? ? ? ? ??? 2 1 out r r 16.0v the resistive divider should sit as close to vfb pin as possible. layout consideration in order to ensure a proper operation of AIC2300, the following points should be managed comprehensively. 1. the input capacitor and v in should be placed as close as possible to each other to reduce the input voltage ripple and noise. 2. the output loop, which is consisted of the inductor, the internal main power switch, the internal syn- chronous power switch and the output capacitor, should be kept as small as possible. 3. the routes with large current should be kept short and wide. 4. logically the large current on the converter should flow at the same direction. 5. the vfb pin should be connected to the feedback resistors directly and the route should be away from the noise sources.
AIC2300 10 ? physical dimensions ? sot-23-5 note: information provided by aic is believed to be accurate and reliabl e. however, we cannot assume responsibility for use of any ci rcuitry other than circuitry entirely embodied in an aic product; nor for any infringement of patents or other rights of third parties that may re sult from its use. we reserve the right to change the circuitr y and specifications without notice. life support policy: aic does not authorize any aic product for us e in life support devices and/or systems. life support device s or systems are devices or systems which, (i) are intended for surgical implant into the body or (ii) support or sustain life, and whose failur e to perform, when properly used in accordance with instructi ons for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. c a a2 b with plating view b l1 l seating plane gauge plane 0.25 a1 section a-a base metal e1 d e aa e1 see view b e note : 1. refer to jedec mo-178aa. 2. dimension "d" does not include mold flash, protru sions or gate burrs. mold flash, protrusion or gate bu rrs shall not exceed 10 mil per side. 3. dimension "e1" does not include inter-lead flash or protrusions. 4. controlling dimens ion is millimeter, converted in ch dimensions are not necessarily exact. 0 0.90 0.30 1.50 2.60 2.80 0.08 0.30 0.00 e l1 l e1 c e e1 d b a2 a1 0.95 bsc 8 0.60 1.90 bsc 0.60 ref 1.30 1.70 3.00 3.00 0.22 0.50 0.15 0.95 min. s y m b o l a 1.45 max. sot-23-5 millimeters
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