ACE705 High efficiency, Low supply current, step-up DC/DC Controller Description The ACE705 series are CMOS-based PFM step-up DC-DC Controller with low supply current and high output voltage accuracy. Quiescent current drawn from power source is as low as 6uA. It is capable of delivering 500mA output current at 4.0V output with 2V input Voltage. Only four external components are necessary: An inductor, a Schottky diode, an output filter capacitor and a NMOSFET or a NPN transistor All of these features make ACE705 series be suitable for the portable devices, which are supplied by a single battery to four-cell batteries. ACE705 has a drive pin (EXT) for external transistor. So it is possible to load a large output current with a power transistor which has a low saturation voltage. ACE705 integrates stable reference circuits and trimming technology, so it can afford high precision and low temperature-drift coefficient of the output voltage. ACE705 is available in SOT-23-3 and SOT-23-5 packages which are PB free. And in SOT-23-5 the device can be switch on or off easily by CE pin, to minimize the standby supply current. Features Deliver 500mA at 4.0V Output voltage with 2.0V input Voltage The converter output voltage can be adjusted from 2.5V～6.0V(In 0.1V step) Output voltage accuracy 2％ Low temperature-drift coefficient of the output voltage 100ppm/℃ Only four external components are necessary: An inductor, a Schottky diode an output filter capacitor and a NMOSFET or a NPN transistor High power conversion efficiency 90％ Low quiescent current drawn from power source 6uA Application Power source for PDA. DSC. MP3 Player. electronic toy and wireless mouse Power source for a single or dual-cell battery-powered equipments Power source for LED Absolute Maximum Ratings Parameter Input voltage range Input voltage CE pin voltage Symbol Max Unit -0.3~12 V V(EXT) -0.3~Vout+0.3 V -0.3~Vout+0.3 V EXT pin output current Maximum power dissipation, Pd T=25℃ SOT-23-5 SOT-23-3 Operating junction temperature 0.7 A 250 250 125 mW Ambient Temperature -40~85 ℃ Storage temperature range -40~150 ℃ ℃ VER 1.4 1 ACE705 High efficiency, Low supply current, step-up DC/DC Controller Packaging Type SOT-23-3 SOT-23-5 3 1 5 2 1 4 2 3 SOT-23-3 SOT-23-5 Description Function 1 4 VSS(GND) Ground pin 2 2 VOUT Output pin, power supply for internal circuits 3 5 Ext Switching pin 3 NC No connection 1 CE Chip enable pin (active high) Ordering information ACE705 X XX XX + H Halogen - free Pb - free BN : SOT-23-5 BM : SOT-23-3 Output Voltage : 2.5V / 3.0V ….. 6.0V Function Description : 1 : Without Enable circuit 2 : With Enable circuit VER 1.4 2 ACE705 High efficiency, Low supply current, step-up DC/DC Controller Block Diagram ACE705 Recommended Work Conditions Item Min Nom Max Unit Input voltage range 0.8 Vout V Inductor 10 100 μH Input capacitor Output capacitor μF 0 ≧10 47 Ambient Temperature (TA) -40 220 μF 85 O C *Suggestion: Use tantalum type capacitor to reduce the ripple of the output voltage. Use 1nF filter ceramic type capacitor to connect Vout pin and GND pin. The filter capacitor is recommended as close as possible to Vout pin and GND pin. VER 1.4 3 ACE705 High efficiency, Low supply current, step-up DC/DC Controller Electrical Characteristics Default condition (unless otherwise provided): Vin=0.6xVout, Iout=10mA.Temperature=25℃. Use external circuit in test circuit list. Parameter Output Voltage Symbol Test Conditions Vout Input Voltage Input Current * (no load) Vin Lin Iout=0mA, Vin=Vout*0.6 Quiescent current * IDD No external component, Vout=Voutx1.05 Chip leakage current CE “H: threshold voltage CE “L” threshold voltage Istandby VCE=0V VCEH VCE:02V VCEL VCE:20V Oscillator frequency FOSC CE ”H” CE “L” EXT “H” output current EXT “H” output current Oscillator duty cycle Min Typ Max 2.45 2.5 2.55 2.646 2.7 2.754 2.94 3.0 3.06 3.234 3.3 3.366 3.528 3.6 3.672 3.92 4.0 4.08 4.9 5.0 5.1 5.88 6.0 6.12 Unit V 12 V 20 25 uA 6 15 uA 1 uA 0.8 V 0.3 V ICEH Vout=Vout*0.96 Test EXT pin frequency Vout=VCE=6V -0.5 0 0.5 uA ICEL Vout=VCE=6V -0.5 0 0.5 uA -21 IEXTH 3.0V<=Vout<=3.9V 4.0V<=Vout<=4.9V 5.0V<=Vout<=6.9V -41 3.0V<=Vout<=3.9V 23 4.0V<=Vout<=4.9V 25 5.0V<=Vout<=6.9V 31 IEXTL Duty On(Vlx “L”) side 350 Khz -35 70 75 mA mA 80 % Note : 1. Diode: Schottky type, such as: 1N5817, 1N5819, 1N5822 2. Inductor: 27uH(R<0.5Ω) 3. Output Capacitor: 100uF (Tantalum type) 4. Vout pin filter capacitor: 1nF (Ceramic type) 5. Input capacitor: 47uF VER 1.4 4 ACE705 High efficiency, Low supply current, step-up DC/DC Controller Typical Application (1) Application with external NMOSFET Vin D 1N5817 Vout L 27uH EXT Cin 47uF OUT ACE705 CE OFF GND ON Cp 1nF Cout 100uF Tan Rload Figure 1 (2) Application with external NPN transistor ACE705 Figure 2 Note: R1=330Ω, C1=10nF. (R1 can be calculated by load. If load is light R1’s value can be added. If load is heavy R1’s value can be smaller. ) Detailed Description The ACE705 series are boost structure, voltage-type pulse-frequency modulation(PFM) step-up DC-DC controller. Only four external components are necessary: an inductor, a schottky diode, an output filter capacitor and a NMOSFET or a NPN transistor. The step-up DC-DC converter, constructed by ACE705, can be adjusted from 2.5V to 6.0V, 0.1V step. By using the depletion technics, the quiescent current drawn from power source is lower than 8uA. The high efficiency device consists of resistors for output voltage detection and trimming, a start-up voltage circuit, an oscillator, a reference circuit, a PFM control circuit, a switch protection circuit and a driver transistor. ACE705 integrates PFM control system. This system controls fixed power switch on duty cycle frequency to stabilize output voltage by calculating results of other blocks which sense input voltage, output voltage, output current and load conditions. In PFM modulation system, the frequency and pulse width is fixed. The duty cycle is adjusted by skipping pulses, so that switch on-time is changed based on the conditions such as input voltage, output current and load. The oscillate block inside ACE705 provides fixed frequency and pulse width wave. VER 1.4 5 ACE705 High efficiency, Low supply current, step-up DC/DC Controller The reference circuit provides stable reference voltage to output stable output voltage. Because internal trimming technology is used, the chip output change less than ±2%. At the same time，the problem of temperature-drift coefficient of output voltage is considered in design, so temperature-drift coefficient of output voltage is less than 100ppm/℃。 High-gain differential error amplifier guarantees stable output voltage at difference input voltage and load. In order to reduce ripple and noise, the error amplifier is designed with high band-with. ACE705 has a drive pin (EXT) for external transistor. So it is possible to load a large output current with a power transistor and a low saturation voltage. At very light load condition, the switch current and quiescent current of chip will effect efficiency certainly. So in very light load condition, the efficiency will drop. Therefore, it is recommended that user use ACE705 in the condition of load current as large as several tens of mA to several hundreds of mA Selection of the External Components Thus it can be seen, the inductor, schottky diode and external NMOSFET or NPN transistor. affect the conversion efficiency greatly. The inductor and the capacitor also have great influence on the output voltage ripple of the converter. So it is necessary to choose a suitable inductor, a capacitor, an external NMOSFET or NPN transistor and a right schottky diode, to obtain high efficiency and low ripple. Before discussion，we define D≡Vout-Vin / Vout (1)Inductor Selection Above all, we should define the minimum value of the inductor that can ensure the boost DC-DC to operate in the continuous current-mode condition. Lmin≧D(1-D)2RL / 2f The above expression is got under conditions of continuous current mode, neglect Schottky diode’s voltage, ESR of both inductor and capacitor. The actual value is greater that it. If inductor’s value is less than Lmin，the efficiency of DC-DC converter will drop greatly, and the DC-DC circuit will not be stable. Secondly, consider the ripple of the output voltage, ΔI=D•Vin / Lf Im ax=Vin / (1-D)2RL + DVin / 2Lf If inductor value is too small, the current ripple through it will be great. Then the current through diode and power switch will be great. Because the power switch on chip is not ideal switch, the energy of switch will improve. The efficiency will fall. Thirdly，in general, smaller inductor values supply more output current while larger values start up with lower input voltage and acquire high efficiency. VER 1.4 6 ACE705 High efficiency, Low supply current, step-up DC/DC Controller An inductor value of 3uH to 1mH works well in most applications. If DC-DC converter delivers large output current (for example: output current is great than 50mA), large inductor value is recommended in order to improve efficiency. If DC-DC must output very large current at low input supply voltage, small inductor value is recommended. The ESR of inductor will effect efficiency greatly. Suppose ESR value of inductor is r L，Rload is load resistor，then the energy can be calculated by following expression: Δη≈ RL / Rload (1-D)2 For example: input 1.5V, output is 3.0V, Rload=20Ω, rL=0.5Ω, The energy loss is 10%. Consider all above，inductor value of 47uH、ESR<0.5Ω is recommended in most applications. Large value is recommended in high efficiency applications and smaller value is recommended (2)Output Capacitor Selection Ignore ESR of capacitor，the ripple of output voltage is: R=ΔVout / Vout=D / Rload Cf So large value capacitor is needed to reduce ripple. But too large capacitor value will slow down system reaction and cost will improve. So 100uF capacitor is recommended. Larger capacitor value will be used in large output current system. If output current is small (<10mA), small value is needed. Consider ESR of capacitor，ripple will increase： r'=r+Imax•RESR / Vout When current is large, ripple caused by ESR will be main factor. It may be greater than 100mV。The ESR will affects efficiency and increase energy loss. So low-ESR capacitor (for example: tantalum capacitor) is recommend or connect two or more filter capacitors in parallel. (3)Diode Selection Rectifier diode will affects efficiency greatly，Though a common diode (such as 1N4148) will work well for light load，it will reduce about 5%~10% efficiency for heavy load，For optimum performance, a Schottky diode (such as 1N5817、1N5819、1N5822) is recommended. (4)Input Capacitor If supply voltage is stable, the DC-DC circuit can output low ripple, low noise and stable voltage without input capacitor. If voltage source is far away from DC-DC circuit, input capacitor value greater than 10uF is recommended. VER 1.4 7 ACE705 High efficiency, Low supply current, step-up DC/DC Controller (5)Vout~GND filter Capacitor Because the chip’s switch current flows from Vout pin, then through the chip into GND pin. Therefore if the output capacitor’s two pins were not very near the chip’s Vout pin and GND pin, Vout ‘s stable would be affected. User will found that the output voltage will drop when load grows up if the output capacitor’s two pin is not very near the chip’s Vout pin and GND pin. In this condition, 1nF ceramic capacitor is recommended at very near the chip’s Vout pin and GND pin. So in all ACE705 application, two capacitors are needed to obtain stable output voltage. The 100μF tantalum output capacitor is recommended to stable output voltage nearby load. The 1nF Vout pin to GND pin ceramic filter capacitor is recommended to stable chip’s sense voltage. Test Circuits (1) Output voltage test circuit ACE705 Figure 3 (2) Quiescent current test circuit ACE705 Figure 4 (3) Input Current (no load) test circuit ACE705 Figure 5 VER 1.4 8 ACE705 High efficiency, Low supply current, step-up DC/DC Controller (4) Oscillator frequency and duty cycle test circuit ACE705 Figure 6 Extend Applications (1) 12V step-up application ACE705 Figure 7 Note: ACE705’s output voltage is 6V. When the output current is small or no load, the output voltage will be unstable, use the RZD for flowing the bias current through the zener diode. For step-up application, a diode(for example: 1N4148) is needed as starter circuit. VER 1.4 9 ACE705 High efficiency, Low supply current, step-up DC/DC Controller (2) Step-down application ACE705 Figure 8 Note: In step-down application, use starter circuit as above. 2.5V≤Vzener≤Vout. RST is needed for bias current of zener diode. This starter circuit also can be used in high voltage step-up application. (3) Flyback step-up/step-down application ACE705 Figure 9 Note: In step-down and step-up/step-down application, starter circuit in fig 8 is need. In step-up application, simpler starter circuit in fig 9 can be used. VER 1.4 10 ACE705 High efficiency, Low supply current, step-up DC/DC Controller Typical Characteristic (Recommended operating conditions: L=10uH, Cin=47uF, Cout=100uF, Cp=1nF, Topt=25℃, unless otherwise noted) 1.Output Voltage VS. Output Current ACE705230BN+ Output Voltage VS. Output Current Iout (mA) 3. Efficiency VS. Output Current ACE705230BN+ Efficiency VS. Output Current Iout (mA) 7. Ripple VS. Output Current ACE705230BN+ Ripple VS. Output Current Iout (mA) 2.Output Voltage VS. Output Current ACE705260BN+ Output Voltage VS. Output Current Iout (mA) 4.Efficiency VS. Output Current ACE705260BN+ Efficiency VS. Output Current Iout (mA) 8.Ripple VS. Output Current ACE705260BN+ Ripple VS. Output Current Iout (mA) VER 1.4 11 ACE705 High efficiency, Low supply current, step-up DC/DC Controller Packing Information SOT-23-3 VER 1.4 12 ACE705 High efficiency, Low supply current, step-up DC/DC Controller Packing Information SOT-23-5 VER 1.4 13 ACE705 High efficiency, Low supply current, step-up DC/DC Controller Notes 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 systems 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 expected 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 safety or effectiveness. ACE Technology Co., LTD. http://www.ace-ele.com/ VER 1.4 14