4 Channel DC/DC Converters IC with High-Efficiency Step-up and Step-down General Description The is a complete power-supply solution for digital still cameras and other hand-held devices. It integrates a high-efficiency main step-up DC-DC converter, two highefficiency step-down converters, a charge pump, and voltage detector. The is targeted for applications that use either two or three AA cells or a single lithiumion battery. The main step-up DC-DC converter accepts inputs from 1.5V to 5.5V and build in 2.6A Internal switch. The two step-down DC-DC converters (CH2, CH3) accept inputs from 1.5V to 5.5V and regulate a resistor-adjustable output from 0.8V to 5.5V. Each DC-DC converters have independent shutdown inputs. The feature of the charge pump is to deliver few current to micro-controller when the system operates in the standby mode. include a low battery detector with 0.8V detection voltage. An adjustable operating frequency (up to 1.4MHZ) is utilized to get optimum size, cost, and efficiency. is available in VQFN-32L 5x5 package. Features 1.5V to 5.5V Battery Input Voltage Range Main step-up DC-DC Converter 1.5V to 5.5V Adjustable Up to 90% Efficiency 2.6A, 0.3Ω Internal Power Switch Two Step-Down DC-DC Converters 0.8V to 5.5V Adjustable 94% Efficiency 100% Duty Cycle Step-up Charge Pump for Micro-Controller Build-in 0.8V Voltage Detector Up to 1.4MHz Switching Frequency 1μA Supply Current in Shutdown Mode Programmable Soft Start Function Independent Enable Pin (CH1, CH2, CH3) External Compensation Network (CH1, CH2, CH3) Short Circuit Protection (CH1, CH2, CH3) Over Voltage Protection (CH2) 32-Lead VQFN Package RoHS Compliant and 100% Lead (Pb)-Free Applications Ordering Information Package Type QV : VQFN-32L 5x5 (V-Type) Operating Temperature Range P : Pb Free with Commercial Standard Note : RichTek Pb-free products are : RoHS compliant and compatible with the current requirements of IPC/JEDEC J-STD-020. Suitable for use in SnPb or Pb-free soldering processes. 100% matte tin (Sn) plating. Digital Still Camera PDAs Portable Device Pin Configurations (TOP VIEW) COMP3 VDD3 P3 SS RT LBO 1 2 3 4 5 6 7 8 VDDM FB3 LBI FB1 EN3 COMP1 EN2 CPFB FB2 VDDC COMP2 CX EN1 P1 ENM 32 31 30 29 9 10 11 12 13 14 28 27 26 25 15 16 24 23 22 21 20 19 18 17 VDD2 VDD2 P2 VDD1 VQFN-32L 5x5 1
Preliminary Typical Application Circuit 1-cell Li+ Battery 3.4V to 4.2V V BAT C13 C14 10μF 10μF L2 4.7μH V BAT 1.5V/500mA IGBT Driver 5V/50mA C17 to C20 10μF x 4 C7 to C8 10μF x 2 R3 680k C9 4.7nF C1 to C2 10μF x 2 R1 200k R2 220k 1nF R4 130k C3 100pF C5 C10 V BAT 1nF C4 10μF 1nF L1 4.7μH D2 SS0520 Chip Enable C11 D1 SS0520 R5 R6 R7 20k 30k C12 1nF 2 3 32 14 C6 15 22nF 13 30k 25 26 29 30 12 27 1 5 VDD3 FB3 VDDC CX CPFB ENM EN1 EN2 EN3 COMP1 COMP2 COMP3 SS R8 RT P3 VDDM 9 P2 VDD1 VDD2 P1 6 4 20 16 7 31 FB1 LBO LBI FB2 18 19 17 11 8 10 23 24 21 22 28 C15 0.1μF D3 SS0520 R9 680k R10 130k L3 4.7μH R12 C23 100pF C16 100pF R11 C25 to C26 10μF x 2 R13 470k R14 150k 5V/500mA 3 RT9701CB VIN VOUT 5 4 EN VOUT 1 Chip Enable 2 10uF C21 to C24 10μF x 4 C27 to C30 10μF x 4 Low Battery Warning Output (Open Drain) V BAT 3.3V/500mA Figure 1. Typical Application Circuit from 1-cell Li+ Battery 2
2-AA Battery 2.0V to 3.4V 3.3V C12 10μF V BAT 1.5V/300mA C27 to C30 10μF x 4 μc standby 3.3V/1mA C7 10μF 2 C1 to C2 10μF x 2 L1 4.7μH 3 R1 C3 200k 100pF 32 R2 D1 V 14 220k BAT SS0520 C4 10μF C6 15 R3 47k C5 1nF D2 SS0520 10nF 13 R4 15k 25 Chip Enable 26 29 30 R5 R6 20k 30k 12 27 R7 30k 1 C8 C9 4.7nF 1nF C10 5 1nF C11 1nF SS VDDM 9 VDD3 FB3 VDDC CX CPFB ENM EN1 EN2 EN3 COMP1 COMP2 COMP3 RT VDD1 FB1 LBO LBI VDD2 FB2 P3 P2 P1 6 4 20 16 7 31 18 19 17 11 8 10 23 24 21 22 28 R9 470k R10 150k L3 4.7μH C14 100pF L2 4.7μH D3 SS0520 R12 C13 100pF R11 C21 to C22 10μF x 2 R13 470k R14 220k V BAT C15 to C16 10μF x 2 I/O 3.3V/500mA C17 to C20 10μF x 4 Low Battery Warning Output (Open Drain) V BAT 3.3V 2.5V/300mA C23 to C26 10μF x 4 R8 Figure 2. Typical Application Circuit from 2-AA Battery Supply 3
Preliminary Function Block Diagram VDDM ENM VDDC CX CPFB LBO LBI SS CH4 Charge Pump EN Voltage Dector Soft-Start OSC EN CH1 Current-MODE Asynchronous Step-Up PWM Boost CH2 Current-MODE Synchronous Step-Down PWM EN1 VDD1 P1 COMP1 FB1 EN2 VDD2 P2 RT PWM OSC Buck2 COMP2 FB2 Thermal Shutdown CH3 Current-MODE Synchronous Step-Down PWM Buck3 EN3 VDD3 P3 COMP3 FB3 ENM EN1 EN2 EN3 Charge CH1+Voltage CH2 CH3 Pump Detector 0 X X X Off Off Off Off 1 0 0 0 On Off Off Off 1 1 0 0 On On Off Off 1 1 1 0 On On On Off 1 1 1 1 On On On On 4
Functional Pin Description Pin Number Pin Name Pin Function 1 COMP3 CH3 feedback compensation pin. 2 VDD3 CH3 power input pin. 3 CH3 switch node. Drains of the internal P-channel and N-Channel MOSFET switches. Connect an inductor to pins together as close as possible. 4 P3 Power ground for CH3. 5 SS Sets the soft start interval of the converter. Connect a capacitor from this pin to ground. 6 RT Frequency setting resistor connection pin. Frequency is 500KHz if RT pin not connected 7 Analog Ground 8 LBO Voltage detector output. 9 VDDM Device input power pin. 10 LBI Voltage detector feedback input. 11 FB1 CH1 feedback input pin. 12 COMP1 CH1 feedback compensation pin. 13 CPFB Charge pump feedback pin. 14 VDDC Charge pump power input pin. 15 CX Charge pump external driver pin. 16 P1 Power ground for CH1 17 VDD1 CH1 power input pin. Connect output of Boost to this pin. 18, 19 CH1 switch node. Connect an inductor to pins together as close as possible. 20 P2 Power ground for CH2. 21, 22 CH2 switch node. Drains of the internal P-channel and N-Channel MOSFET switches. Connect an inductor to pins together as close as possible. 23, 24 VDD2 CH2 power input pin. 25 ENM Whole device control pin. Tie this pin higher than 1.3V to enable the device. Tie below 0.4V to turn off the device. 26 EN1 CH1 enable input. Tie this pin higher than 1.3V to enable CH1. Tie below 0.4V to turn off the CH1. 27 COMP2 CH2 feedback compensation pin. 28 FB2 CH2 feedback input. 29 EN2 CH2 enable input. Tie this pin higher than 1.3V to enable CH2. Tie below 0.4V to turn off the CH2. 30 EN3 CH3 enable input. Tie this pin higher than 1.3V to enable CH3. Tie below 0.4V to turn off the CH3. 31 Analog ground. 32 FB3 CH3 feedback input. Exposed Pad Exposed pad should be soldered to PCB board and connected to. 5
Preliminary Absolute Maximum Ratings Supply Input Voltage (V DDM, V DD1, V DD2,V DD3,V DDC ) ----------------------------------------------------- 0.3 to 7V Pin Switch Voltage ----------------------------------------------------------------------------------------- 0.3V to 7V Pin Switch Voltage ----------------------------------------------------------------------------------------- 0.3V to (V DD2 + 0.3V) Pin Switch Voltage ----------------------------------------------------------------------------------------- 0.3V to (V DD3 + 0.3V) CX Pin Switch Voltage ------------------------------------------------------------------------------------------ 0.3V to (V DDC + 0.3V) Other I/O Pin Voltage ------------------------------------------------------------------------------------------- 0.3V to (V DDM + 0.3V) Package Thermal Resistance VQFN-32L 5x5, θ JA ----------------------------------------------------------------------------------------------- 34 C/W Lead Temperature (Soldering, 10 sec.) -------------------------------------------------------------------- 260 C Operation Temperature Range ------------------------------------------------------------------------------- 40 C to 85 C Junction Temperature Range --------------------------------------------------------------------------------- 0 C to 125 C Storage Temperature Range ---------------------------------------------------------------------------------- 65 C to 150 C ESD Susceptibility HBM (Human Body Mode) ------------------------------------------------------------------------------------ 2kV MM (Machine Mode) -------------------------------------------------------------------------------------------- 200V Electrical Characteristics (V DDM =3.3V, T A = 25 C, Unless Otherwise specification) Supply Voltage Parameter Symbol Test Condition Min Typ Max Units Minimum Startup Voltage (Boost) V ST Boost loading < 1mA -- 1.5 -- V VDDM Operating Voltage V VDDM VDDM Pin Voltage 2.4 -- 5.5 V VDD1, VDD2, VDD3 Operating Voltage V VDD1 V VDD2, V VDD3 VDD1, VDD2, VDD3 Pin Voltage 1.5 5.5 V VDDM Over Voltage Protection -- 6.5 -- V Supply Current Shutdown Supply Current I OFF V ENM pin=0v -- 0.01 1 μa Charge Pump Current CH1 DC/DC Converter + Voltage Detector Supply Current CH2 DC/DC Converter Supply Current CH3 DC/DC Converter Supply Current I VDDM I VDDM I VDDM I VDDM V VDDM = 3.3V, V ENM = 3.3V, V EN1 = 0V, V EN2 = 0V, V EN3 = 0V V VDDM = 3.3V, V FB1 = 0.9V V ENM = 3.3V, V EN1 = 3.3V, V EN2 = 0V, V EN3 = 0V V VDDM = 3.3V, V FB2 = 0.9V V ENM = 3.3V, V EN1 = 0V, V EN2 = 3.3V, V EN3 = 0V V VDDM = 3.3V, V FB3 = 0.9V V ENM = 3.3V, V EN1 = 0V, V EN2 = 0V, V EN3 = 3.3V -- 30 42 μa -- 250 350 μa -- 250 350 μa -- 250 350 μa To be continued 6
Oscillator Parameter Symbol Test Condition Min Typ Max Units Operation Frequency Range F OSC RT Open 475 550 625 khz CH1 Maximum Duty Cycle D MAX1 -- 85 90 % CH2 Maximum Duty Cycle D MAX2 -- -- 100 % CH3 Maximum Duty Cycle D MAX3 -- -- 100 % Feedback Voltage (CH1, CH2, CH3, CH4) Feedback Voltage V FB CH1, CH2, CH3 0.788 0.8 0.812 V Feedback Voltage (Charge Pump) V CPFB CH4 0.78 0.8 0.82 V Feedback Voltage Error Amplifier CH1, CH2, CH3, CH4 ΔV FB 3.0V < V DDM < 5.5V -- -- 12 mv GM -- 0.2 -- ms Compensation Source Current -- 22 -- μa Compensation Sink Current -- 22 -- μa Power Switch CH1 On Resistance of MOSFET R DS(ON) N-MOSFET -- 300 400 mω CH1 Current Limitation V VDD1 = 3.3V 2 2.6 3 A CH2 On Resistance of MOSFET R DS(ON) N-MOSFET, V VDD2 = 3.3V -- 350 450 mω P-MOSFET, V VDD2 = 3.3V -- 350 450 mω CH2 Current Limitation V VDD2 = 3.3V 1.3 1.5 1.9 A CH3 On Resistance of MOSFET R DS(ON) N-MOSFET, V VDD3 = 3.3V -- 350 450 mω P-MOSFET, V VDD3 = 3.3V -- 350 450 mω CH3 Current Limitation V VDD3 = 3.3V 1.3 1.5 1.9 A Voltage Detector Feedback Voltage for Voltage detector Feedback Voltage for Voltage detector V LBI (Falling) 0.75 0.77 0.79 V V LBI (Rising) 0.79 0.81 0.83 V LBO pin Sink Current V LBO = 1V 3 5 -- ma UVP (CH2, CH3) & Over Voltage Protection (CH2) UVP Threshold Voltage @FB2, FB3 0.3 0.4 0.5 V Over Voltage Protection @FB2 0.95 1 -- V Control ENM, EN1, EN2, EN3 Input High Level Threshold ENM, EN1, EN2, EN3 Input Low Level Threshold Thermal Protection V VDDM = 3.3V -- 0.8 1.3 V V VDDM = 3.3V 0.4 0.8 -- V Thermal Shutdown T SD 140 180 -- C Thermal Shutdown Hysteresis ΔT SD -- 10 -- C 7
Preliminary Typical Operating Characteristics 0.808 Reference Voltage vs. Temperature 1800 Oscillator Ferquency vs. R RT Reference Voltage (V) 0.806 0.804 0.802 0.8 0.798 0.796 0.794 Oscillator Frequecny (khz) 1600 1400 1200 1000 800 600 400 200 0.792-50 -30-10 10 30 50 70 90 Temperature ( C) 0 0 100 200 300 400 500 600 R RT (kω) Efficiency (%) 100 90 80 70 60 50 Boost Efficiency vs. Output Current VOUT = 3.3V VIN 3V 2.5V 1 10 100 1000 Output Current (ma) 2V 1.8V Boost (V) Boost vs. V DD1 Voltage 3.345 VBAT = 2.5V, VDDM = 3.3V, IOUT = 250mA 3.34 3.335 3.33 3.325 3.32 3.315 3.31 3.305 1.5 2 2.5 3 3.5 4 4.5 5 5.5 V DD1 Voltage (V) (V) Boost vs. V DDM Voltage 3.332 VBAT = 2.5V, VDD1 = 3.3V, IOUT = 250mA 3.33 3.328 3.326 3.324 3.322 3.32 3.318 3.316 2.4 2.8 3.2 3.6 4 4.4 4.8 5.2 5.6 V DDM Voltage (V) Boost Load Transient Response VIN = 1.8V, VOUT = 3.3V, @IOUT = 100mA to 400mA 8
Boost Load Transient Response Boost Load Transient Response VIN = 2V, VOUT = 3.3V, @IOUT = 100mA to 400mA VIN = 2.5V, VOUT = 3.3V, @IOUT = 100mA to 400mA Boost Load Transient Response Boost LX & VIN = 1.8V, VOUT = 3.3V, @IOUT = 100mA Time (1us/Div) Boost LX & Boost LX & VIN = 1.8V, VOUT = 3.3V, @IOUT = 300mA VIN = 2.5V, VOUT = 3.3V, @IOUT = 100mA VIN = 3V, VOUT = 3.3V, @IOUT = 100mA to 400mA Time (1us/Div) Time (1us/Div) 9
Preliminary Boost LX & VIN = 2.5V, VOUT = 3.3V, @IOUT = 400mA Boost LX & VIN = 3V, VOUT = 3.3V, @IOUT = 100mA Time (1us/Div) Time (1us/Div) Boost LX & VIN = 3V, VOUT = 3.3V, @IOUT = 400mA 100 Buck2 Efficiency vs. Output Current VOUT = 1.5V VIN = 2.2V 90 Efficiency (%) 80 70 60 50 VIN = 4.5V VIN = 3.8V VIN = 2.5V VIN = 3V Time (1us/Div) 1 10 100 1000 Output Current (ma) 100 90 Buck2 Efficiency vs. Output Current VOUT = 1.8V VIN = 2.5V 100 90 80 Buck2 Efficiency vs. Output Current VOUT = 2.5V VIN = 4.5 Efficiency (%) 80 70 VIN = 4.5 VIN = 3.8V VIN = 3V Efficiency (%) 70 60 50 VIN = 3.8V 60 40 VIN = 3V 50 30 1 10 100 1000 1 10 100 1000 Output Current (ma) Output Current (ma) 10
1.82 1.818 Buck2 vs. V DD2 Voltage VBAT = VDDM = 3.3V, IOUT = 250mA 1.82 1.818 Buck2 vs. V DDM Voltage VDD2 = 3.3V, IOUT = 250mA (V) 1.816 1.814 1.812 1.81 1.808 (V) 1.816 1.814 1.812 1.81 1.808 1.806 1.806 1.804 1.804 2 2.5 3 3.5 4 4.5 2 2.5 3 3.5 4 4.5 5 5.5 6 V DD2 Voltage (V) V DDM Voltage (V) Buck2 Load Transient Response Buck2 Load Transient Response @IOUT = 100mA to 400mA @IOUT = 100mA to 400mA VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V Buck2 Load Transient Response Buck2 Load Transient Response @IOUT = 100mA to 400mA @IOUT = 100mA to 400mA VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V 11
Preliminary Buck2 LX & @IOUT = 500mA Buck2 LX & @IOUT = 250mA VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V Buck2 LX & Buck2 LX & @IOUT = 250mA VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V @IOUT = 500mA VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V Buck2 LX & Buck2 LX & @IOUT = 250mA VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V @IOUT = 500mA VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V 12
Buck2 LX & Buck2 LX & @IOUT = 250mA VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V @IOUT = 500mA VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V 100 Buck3 Efficiency vs. Output Current VOUT = 1.5V VIN = 2.2V 100 Buck3 Efficiency vs. Output Current VOUT = 1.8V VIN = 2.5V 90 90 Efficiency (%) 80 70 VIN = 4.5V VIN = 2.5V VIN = 3V VIN = 3.8V Efficiency (%) 80 70 VIN = 4.5V VIN = 3.8V VIN = 3V 60 60 50 1 10 100 1000 Output Current (ma) 50 1 10 100 1000 Output Current (ma) Efficiency (%) 100 90 80 70 60 50 Buck3 Efficiency vs. Output Current VOUT = 2.5V VIN = 3V VIN = 3.8V VIN = 4.5V (V) 1.806 1.804 1.802 1.8 1.798 1.796 1.794 Buck3 vs. V DD3 Voltage VBAT = VDDM = 3.3V, IOUT = 250mA 40 1.792 30 1 10 100 1000 Output Current (ma) 1.79 2 2.5 3 3.5 4 4.5 V DD3 Voltage (V) 13
Preliminary (V) 1.806 1.804 1.802 1.8 1.798 1.796 1.794 1.792 1.79 Buck3 vs. V DDM Voltage VDD3 = 3.3V, IOUT = 250mA Buck3 Load Transient Response @IOUT = 100mA to 400mA VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V 2 2.5 3 3.5 4 4.5 5 5.5 6 V DDM Voltage (V) Buck3 Load Transient Response Buck3 Load Transient Response @IOUT = 100mA to 400mA @IOUT = 100mA to 400mA VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V Buck3 Load Transient Response Buck3 LX & @IOUT = 100mA to 400mA @IOUT = 250mA VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V VDD3 = 4.5V, VDDM = 3.3V, VOUT = 1.8V VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V 14
Buck3 LX & @IOUT = 500mA Buck3 LX & @IOUT = 250mA VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V Buck3 LX & Buck3 LX & @IOUT = 500mA VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V Buck3 LX & Buck3 LX & @IOUT = 500mA VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V @IOUT = 250mA VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V @IOUT = 250mA VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V 15
Preliminary Buck3 LX & @IOUT = 500mA Charge Pump CX & @IOUT = 1mA VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V (5mV/Div) Charge Pump CX & @IOUT = 1mA Charge Pump Charge Pump VIN = 2V, VDDM = 3.3V, VOUT = 3.3V Time (5us/Div) (5mV/Div) VIN = 2.5V, VDDM = 3.3V, VOUT = 3.3V Time (25us/Div) 16
Application Information The is a four-channel DC/DC converter with one voltage detector for digital still cameras and other handheld device. The four channels DC/DC converters are as follows: CH1: Step-up, asynchronous current mode DC/DC converter with an internal power MOSFET, current limit protection and high efficiency control for wide loading range CH2: Step-down, synchronous current mode DC/DC converter with internal power MOSFETs, current limit, short-circuit, over voltage protection and high efficiency control for wide loading range. CH3: Step-down, synchronous current mode DC/DC converter with internal power MOSFETs, current limit, short-circuit protection and high efficiency control for wide loading range. CH4: Charge pump DC/DC converter. Soft-Start CH1, CH2 and CH3 can be soft-started individually every time when the channel is enabled. Soft-start is achieved by ramping up the voltage reference of each channel's input of error amplifier. Adding a capacitor on SS pin to ground sets the ramping up speed of each voltage reference. Triangle wave will be appeared on SS pin, which provides a clock base for soft-start. The soft-start timing would be setted by following formular. T SS = CSS 10 x (ms) 1nF Oscillator The internal oscillator synchronizes CH1, CH2 and CH3 PWM operation frequency. The operation frequency is set by a resistor between RT pin to ground, ranging from 550kHz to 1.4MHz. Step-up (Boost) DC/DC Converter (CH1) The step-up channel (CH1) is designed as current-mode DC/DC PWM converters with built-in internal power MOS and external Schottky diode. Output voltage is regulated and adjustable up to 5.5V. This channel typically supplies 3.3V for main system power. At light load, efficiency is enhanced by pulse-skipping mode. In this mode, the NMOS turns on by a constant pulse width. As loading increased, the converter operates at constant frequency PWM mode. The max. duty of the constant frequency is 80% for the boost to prevent high input current drawn from input. Protection Current limit The current of NMOS is sensed cycle by cycle to prevent over current. If the current is higher than 2.6A (typical), then the NMOS is off. This state is latched and then reset automatically at next clock cycle. Under Voltage The status of under voltage is decided by comparing FB1 voltage with 0.4V. This function is enabled after soft start finishes. If the FB1 voltage is less than 0.4V, then the NMOS will be turned off immediately. And this state is latched. After a dummy count period, the controller begins a re-soft-start procedure. If the status of under voltage remains after 4 successive times of soft-start, then CH1 is latched. Over Voltage The over voltage protection is used when the output of CH1 supplies the power of the main chip. If the output voltage of CH1 is over 6.5V, the main chip is shutdown and the NMOS is kept off. Step-Down (Buck) DC/DC Converter (CH2, CH3) The step-down channels (CH2, CH3) are designed as synchronous current-mode DC/DC PWM converters. Output voltage is regulated and adjustable down to 0.8V. The internal synchronous power switches eliminate the typical Schottky free wheeling diode and improve efficiency. At light load, efficiency is enhanced by pulse-skipping mode. In this mode, the high-side PMOS turns on by a constant pulse width. As loading increased, the converter operates at constant frequency PWM mode. While the input voltage is close to output voltage, the converter 17
Preliminary enters low dropout mode. Duty could be as long as 100% to extend battery life. Protection Current limit (CH2, CH3) The current of high-side PMOS is sensed cycle by cycle to prevent over current. If the current is higher than 1.5A (typical), then the high-side PMOS is off and the low-side NMOS is on. This state is latched and then reset automatically at next clock cycle. Under Voltage (CH2, CH3) The status of under voltage is decided by comparing FB2 (or FB3) voltage with 0.4V. This function is enabled after soft start finishes. If the FB2 (or FB3) voltage is less than 0.4V, then the high/low-side Power MOS are turned off immediately. And this state is latched. After a dummy count period, the CH2 (or CH3) begins a soft-start procedure. However, if the status of under voltage remains after 3 successive times of soft-start, then CH2 (or CH3) is latched. UV remain after 3 How to reset? successive soft-start CH2 CH2 is latched, and whole Toggle ENM IC is shut down CH3 CH3 is latched Toggle EN3 or ENM Over Voltage Protection (CH2) Over voltage protection (OVP) is used to protect the external parts connected to the output of CH2. If the FB2 voltage is higher than 1V, the high-side PMOS is off and low-side NMOS is on. This status is latched and could be reset by toggling ENM. The maximum output current can be determined by Cpump and C OUT ration. This equation would describe the relationship. I MAX = 2 x (V DDC -V F ) x Cpump x Fpump V F : Schottky diode forward voltage Fpump : Charge pump maximum frequency is 500kHz Recommand Cpump 0.1μF. VDDC V BAT CX Cpump C X R1 CPFB C OUT R2 Reference The chip has an internal 0.8V reference voltage, which is the inputs of the error amplifiers of the CH1, CH2, and CH3 to compare the difference of feedback voltage. The reference voltage can be set up stably when the supplied power (VDDM) is above 1.5V, and EN1 (or EN2, EN3) goes high. Thermal Protection Thermal protection function is integrated in the chip. When the chip temperature is higher than 178 degree C, the controllers of CH1, CH2, and CH3 are shutdown. 10 degree C is the hysteresis range of temperature to prevent unstable operation when the thermal protection happens. When the thermal protection is relieved, the chip operates well again. Charge Pump DC/DC converter This is a low quiescent charge pump DC/DC converter, which is enabled by ENM. Add a capacitor C X (~1nF) between charge pump V OUT and CP FB to speed up charge pump response time. Output ripple can be easily suppressed by increasing the capacitance ratio of C OUT and Cpump. This charge pump DC/DC converter can apply to μc stanby power or the gate driver power of IGBT for photoflash, etc. 18
Outline Dimension D D2 SEE DETAIL A 1 L E E2 e b 1 1 A A1 A3 2 2 DETAIL A Pin #1 ID and Tie Bar Mark Options Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Symbol Dimensions In Millimeters Dimensions In Inches Min Max Min Max A 0.800 1.000 0.031 0.039 A1 0.000 0.050 0.000 0.002 A3 0.175 0.250 0.007 0.010 b 0.180 0.300 0.007 0.012 D 4.950 5.050 0.195 0.199 D2 3.500 3.750 0.138 0.148 E 4.950 5.050 0.195 0.199 E2 3.500 3.750 0.138 0.148 e 0.500 0.020 L 0.350 0.450 0.014 0.018 V-Type 32L QFN 5x5 Package RICHTEK TECHNOLOGY CORP. Headquarter 5F, No. 20, Taiyuen Street, Chupei City Hsinchu, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 RICHTEK TECHNOLOGY CORP. Taipei Office (Marketing) 8F-1, No. 137, Lane 235, Paochiao Road, Hsintien City Taipei County, Taiwan, R.O.C. Tel: (8862)89191466 Fax: (8862)89191465 Email: marketing@richtek.com 19