RT9907 3 Channel DC/DC Converters IC with High-Efficiency Step-Up and Step-Down General Description Features The RT9907 is a three channel power-supply solution for digital still cameras and other battery-powered devices. It integrates an asynchronous step-up and two synchronous step-down DC-DC converters. The RT9907 is targeted for applications that use two AA cells or a single lithium-ion battery. z 1.5V to 5.5V Battery Input Voltage Range z Main step-up DC-DC Converter ` 1.5V to 5.5V Adjustable Output Voltage ` Up to 90% Efficiency ` 2.6A, 0.3Ω Ω Internal Power Switch Two Step-Down DC-DC Converters ` 0.8V to 5.5V Adjustable Output Voltage ` 94% Efficiency ` 100% Duty Cycle Up to 1.4MHz Switching Frequency 1uA 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) 24-Lead VQFN Package RoHS Compliant and 100% Lead (Pb)-Free The three DC-DC converters (CH1, CH2, CH3) accept input voltage from 1.5V to 5.5V. Each DC-DC converter has better transient response and excellent stability by providing current-mode control and external compensation network. With built-in Internal MOSFET and up to 1.4MHz operating frequency, the RT9907 allows minimum BOM cost and PCB area. z z z z z z The step-down DC-DC converters (CH2, CH3) can regulate output voltage as low as 0.8V. Three operational modes are available: PWM, PSM, Low-Dropout modes. At PWM mode, Internal synchronous rectifier with low RDS(ON) dramatically reduces conduction loss and achieve 94% efficiency. It enters Low-Dropout mode when normal PWM cannot provide regulated output voltage by continuously turning on the upper P-MOSFET. No external Schottky diode is required in practical application. Each DC-DC converter has independent enable input and soft-start function allowing versatile power sequence combination. Complete protection functions are implemented such as short circuit, over-voltage protection. z z z z Applications z z z Digital Still Camera PDAs Portable Device Pin Configurations (TOP VIEW) ments of IPC/JEDEC J-STD-020. ` EN2 FB2 COMP2 EN3 19 18 EN1 VDD3 2 17 ENM LX3 3 16 VDD2 PGND3 4 15 LX2 SS 5 14 PGND2 RT 6 13 LX1 GND 25 7 8 9 10 11 12 VDD1 RoHS compliant and compatible with the current require- 20 PGND1 ` 21 COMP1 Richtek products are : 22 FB1 Note : 23 1 GND Package Type QV : VQFN-24L 4x4 (V-Type) Lead Plating System P : Pb Free G : Green (Halogen Free and Pb Free) 24 COMP3 VDDM RT9907 GND Ordering Information FB3 The RT9907 is available in small VQFN-24L 4x4 package. VQFN-24L 4x4 Suitable for use in SnPb or Pb-free soldering processes. DS9907-10 April 2011 www.richtek.com 1 RT9907 Typical Application Circuit 1-cell Li+ Battery 3.4V to 4.2V V BAT 4.7μH 10μF 10μF 0.1μF 1μF 10μF x 2 4.7μH 1.5V/500mA 200k 100pF 10μF x 4 2 VDD3 3 LX3 24 VDDM 8 V BAT LX1 13 SS0520 FB3 VDD1 12 5V/500mA 220k 680k Chip Enable 17 ENM 18 EN1 21 22 130k RT9907 VDD2 10k 19 COMP2 30k 1 COMP3 LX2 6 4 4.7μH 3.3V/500mA 14 11 470k 20 GND PGND1 PGND2 PGND3 5 SS 15 100pF FB2 1nF V BAT 10μF x 2 10 COMP1 1nF 16 EN3 20k 1nF 10μF x 4 FB1 EN2 RT 4.7nF 9 10μF x 4 150k 7, 23, Exposed Pad (25) Figure 1. Typical Application Circuit for 1-cell Li+ Battery www.richtek.com 2 DS9907-10 April 2011 RT9907 2-AA Battery 1.8V to 3.2V 1μF 10μF x 2 4.7μH 1.5V/300mA 200k 100pF 10μF x 4 3 24 VDDM 8 2 V BAT VDD3 LX1 13 LX3 4.7μH SS0520 FB3 VDD1 12 I/O 3.3V/500mA 220k 470k Chip Enable 9 17 ENM 18 EN1 21 22 150k RT9907 VDD2 10k 19 COMP2 30k 1 COMP3 LX2 6 4.7μH 2.5V/300mA 4 14 11 470k 20 GND PGND1 PGND2 PGND3 5 SS 15 100pF FB2 1nF 3.3V 10μF x 2 10 COMP1 1nF 16 EN3 20k 1nF 10μF x 4 FB1 EN2 RT 4.7nF V BAT 10μF x 2 10μF x 4 220k 7, 23, Exposed Pad (25) Figure 2. Typical Application Circuit for 2-AA Battery Supply DS9907-10 April 2011 www.richtek.com 3 RT9907 Function Block Diagram VDDM ENM EN CH1 Current-MODE Asynchronous Step-Up PWM EN1 VDD1 LX1 PGND1 Boost SS Soft-Start OSC RT PWM OSC COMP1 FB1 EN2 VDD2 CH2 Current-MODE Synchronous Step-Down PWM LX2 PGND2 Buck2 Thermal Shutdown COMP2 FB2 EN3 VDD3 CH3 Current-MODE Synchronous Step-Down PWM LX3 PGND3 Buck3 COMP3 FB3 GND www.richtek.com 4 ENM EN1 EN2 EN3 CH1 CH2 CH3 0 X X X Off Off Off 1 0 0 0 Off Off Off 1 1 0 0 On Off Off 1 1 1 0 On On Off 1 1 1 1 On On On DS9907-10 April 2011 RT9907 Functional Pin Description Pin No. Pin Name Pin Function 1 COMP3 CH3 Feedback Compensation Pin. 2 VDD3 3 LX3 CH3 Power Input Pin. CH3 Switch Node. Drains of the internal P-MOSFET and N-MOSFET switches. Connect an inductor to LX3 pins together as close as possible. 4 PGND3 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 GND Analog Ground. 8 VDDM Device Input Power Pin. 9 FB1 CH1 Feedback Input Pin. 10 COMP1 CH1 Feedback Compensation Pin. 11 PGND1 Power Ground for CH1 12 VDD1 CH1 Power Input Pin. Connect output of Boost to this pin. 13 LX1 CH1 Switch Node. Connect an inductor to LX1 Pins together as close as possible. 14 PGND2 15 LX2 Power Ground for CH2. CH2 Switch Node. Drains of the internal P-Channel and N-MOSFET switches. Connect an inductor to LX2 pins together as close as possible. 16 VDD2 17 ENM 18 EN1 19 COMP2 CH2 Feedback Compensation Pin. 20 FB2 21 EN2 22 EN3 CH2 Feedback Input. CH2 Enable Input. Tie this pin higher than 1.3V to enable CH2. Tie below 0.4V to turn off the CH2. CH3 Enable Input. Tie this pin higher than 1.3V to enable CH3. Tie below 0.4V to turn off the CH3. 24 FB3 7, 23 25 (Exposed Pad) GND DS9907-10 April 2011 CH2 Power Input Pin. Whole Device Control Pin. Tie this pin higher than 1.3V to enable the device. Tie below 0.4V to turn off the device. CH1 Enable Input. Tie this pin higher than 1.3V to enable CH1. Tie below 0.4V to turn off the CH1. CH3 Feedback Input. The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation. www.richtek.com 5 RT9907 Absolute Maximum Ratings z z z z z z z z z z z z (Note 1) Supply Input Voltage, VDDM, VDD1, VDD2,VDD3 -------------------------------------------------------- −0.3 to 7V LX1 Pin Switch Voltage ------------------------------------------------------------------------------------------ −0.3V to 7V LX2 Pin Switch Voltage ------------------------------------------------------------------------------------------ −0.3V to (VDD2 + 0.3V) LX3 Pin Switch Voltage ------------------------------------------------------------------------------------------ −0.3V to (VDD3 + 0.3V) Other I/O Pin Voltage --------------------------------------------------------------------------------------------- −0.3V to (VDDM + 0.3V) Power Dissipation, PD @ TA = 25°C VQFN-24L 4x4 ----------------------------------------------------------------------------------------------------- 1.85W Package Thermal Resistance (Note 2) VQFN-24L 4x4, θJA ------------------------------------------------------------------------------------------------ 54°C/W Junction Temperature Range ------------------------------------------------------------------------------------ −40°C to 125°C Lead Temperature (Soldering, 10 sec.) ----------------------------------------------------------------------- 260°C Operation Temperature Range ---------------------------------------------------------------------------------- −40°C to 85°C Storage Temperature Range ------------------------------------------------------------------------------------ −65°C to 150°C ESD Susceptibility (Note 3) HBM (Human Body Mode) -------------------------------------------------------------------------------------- 2kV MM (Machine Mode) ---------------------------------------------------------------------------------------------- 200V Electrical Characteristics (VDDM =3.3V, TA = 25°C, Unless Otherwise specification) Parameter Symbol Test Conditions Min Typ Max Unit -- 1.5 -- V 2.4 -- 5.5 V 5.5 V Supply Voltage Minimum Startup Voltage (Boost) V ST Boost loading < 1mA VDDM Operating Voltage V VDDM VDDM Pin Voltage VDD1, VDD2, VDD3 Operating V VDD1 V VDD2 , VDD1, VDD2, VDD3 Pin Voltage V VDD3 Voltage VDDM Over Voltage Protection 1.5 -- 6.5 -- V -- 0.01 1 uA -- 250 350 uA -- 250 350 uA -- 250 350 uA Supply Current Shutdown Supply Current IOFF V ENM pin=0V V VDDM = 3.3V, CH1 DC/DC Converter IVDDM V FB1 = 0.9V V ENM = 3.3V, VEN1 = 3.3V, V EN2 = 0V, VEN3 = 0V V VDDM = 3.3V, CH2 DC/DC Converter Supply Current CH3 DC/DC Converter Supply Current IVDDM IVDDM V FB2 = 0.9V V ENM = 3.3V, VEN1 = 0V, V EN2 = 3.3V, VEN3 = 0V V VDDM = 3.3V, V FB3 = 0.9V V ENM = 3.3V, VEN1 = 0V, V EN2 = 0V, VEN3 = 3.3V To be continued www.richtek.com 6 DS9907-10 April 2011 RT9907 Parameter Symbol Test Conditions Min Typ Max Unit Oscillator Operation Frequency Range F OSC 475 550 625 kHz CH1 Maximum Duty Cycle DMAX1 RT Open -- 85 90 % CH2 Maximum Duty Cycle DMAX2 -- -- 100 % CH3 Maximum Duty Cycle DMAX3 -- -- 100 % 0.788 0.8 0.812 V -- -- 12 mV GM -- 0.2 -- ms Compensation Source Current -- 22 -- uA Compensation Sink Current Power Switch -- 22 -- uA N-MOSFET -- 300 400 mΩ VVDD1 = 3.3V 2 2.6 3 A N-MOSFET, VVDD2 = 3.3V -- 350 450 mΩ P-MOSFET, VVDD2 = 3.3V -- 350 450 mΩ 1.3 1.5 1.9 A N-MOSFET, VVDD3 = 3.3V -- 350 450 mΩ P-MOSFET, VVDD3 = 3.3V -- 350 450 mΩ 1.3 1.5 1.9 A UVP Threshold Voltage @FB2, FB3 0.3 0.4 0.5 V Over Voltage Protection @FB2 0.95 1 -- V VVDDM = 3.3V -- 0.8 1.3 V VVDDM = 3.3V 0.4 0.8 -- V 140 180 -- °C -- 10 -- °C Feedback Voltage (CH1, CH2, CH3) Feedback Voltage V FB Feedback Voltage ︱ΔV FB︱ CH1, CH2, CH3 CH1, CH2, CH3 3.0V < VDDM < 5.5V Error Amplifier CH1 On Resistance of MOSFET RDS(ON) CH1 Current Limitation CH2 On Resistance of MOSFET RDS(ON) CH2 Current Limitation CH3 On Resistance of MOSFET VVDD2 = 3.3V RDS(ON) CH3 Current Limitation VVDD3 = 3.3V UVP (CH2, CH3) & Over Voltage Protection (CH2) Control ENM, EN1, EN2, EN3 Input High Level Threshold ENM, EN1, EN2, EN3 Input Low Level Threshold Thermal Protection Thermal Shutdown T SD Thermal Shutdown Hysteresis ΔT SD Note 1. Stresses listed as the above "Absolute Maximum Ratings" may cause permanent damage to the device. These are for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may remain possibility to affect device reliability. Note 2. θ JA is measured in the natural convection at T A = 25°C on a low effective thermal conductivity test board of JEDEC 51-3 thermal measurement standard. Note 3. Devices are ESD sensitive. Handling precaution is recommended. DS9907-10 April 2011 www.richtek.com 7 RT9907 Typical Operating Characteristics Oscillator Ferquency vs. RRT 1800 0.806 1600 Oscillator Frequecny (kHz) Reference Voltage (V) Reference Voltage vs. Temperature 0.808 0.804 0.802 0.8 0.798 0.796 0.794 1400 1200 1000 800 600 400 200 0.792 0 -50 -30 -10 10 30 50 70 90 0 100 200 300 Temperature (°C) Boost Efficiency vs. Output Current 2V 1.8V 70 60 Boost Output Voltage (V) 2.5V 80 VBAT = 2.5V, VDDM = 3.3V, IOUT = 250mA 3.34 VIN 3V 90 Efficiency (%) 600 Boost Output Voltage vs. VDD1 Voltage 3.345 VOUT = 3.3V 3.335 3.33 3.325 3.32 3.315 3.31 3.305 50 1 10 100 1.5 1000 Output Current (mA) 2 2.5 3 3.5 4 4.5 5 5.5 VDD1 Voltage (V) Boost Output Voltage vs. VDDM Voltage Boost Load Transient Response 3.332 Output Voltage Deviation (100mV/Div) VBAT = 2.5V, VDD1 = 3.3V, IOUT = 250mA 3.328 3.326 3.324 3.322 Load Current (200mA/Div) Output Voltage (V) 500 RRT (kΩ) 100 3.33 400 3.32 3.318 3.316 2.4 2.8 3.2 3.6 4 4.4 4.8 5.2 5.6 VIN = 1.8V, VOUT = 3.3V, @IOUT = 100mA to 400mA Time (1ms/Div) VDDM Voltage (V) www.richtek.com 8 DS9907-10 April 2011 RT9907 Boost Load Transient Response VIN = 2.5V, VOUT = 3.3V, @IOUT = 100mA to 400mA Time (1ms/Div) Time (1ms/Div) Boost Load Transient Response Boost LX & Output Ripple VIN = 1.8V, VOUT = 3.3V, @IOUT = 100mA LX1 (2V/Div) VIN = 3V, VOUT = 3.3V, @IOUT = 100mA to 400mA Output Ripple (10mV/Div) Load Current (200mA/Div) Load Current (200mA/Div) VIN = 2V, VOUT = 3.3V, @IOUT = 100mA to 400mA Output Voltage Deviation (100mV/Div) Load Current (200mA/Div) Output Voltage Deviation (100mV/Div) Output Voltage Deviation (100mV/Div) Boost Load Transient Response Time (1ms/Div) Time (1us/Div) Boost LX & Output Ripple Boost LX & Output Ripple Output Ripple (10mV/Div) Output Ripple (10mV/Div) Time (1us/Div) DS9907-10 April 2011 VIN = 2.5V, VOUT = 3.3V, @IOUT = 100mA LX1 (2V/Div) LX1 (2V/Div) VIN = 1.8V, VOUT = 3.3V, @IOUT = 300mA Time (1us/Div) www.richtek.com 9 RT9907 Boost LX & Output Ripple Boost LX & Output Ripple VIN = 3V, VOUT = 3.3V, @IOUT = 100mA Output Ripple (10mV/Div) Output Ripple (10mV/Div) LX1 (2V/Div) LX1 (2V/Div) VIN = 2.5V, VOUT = 3.3V, @IOUT = 400mA Time (1us/Div) Time (1us/Div) Buck2 Efficiency vs. Output Current Boost LX & Output Ripple 100 VIN = 3V, VOUT = 3.3V, @IOUT = 400mA VOUT = 1.5V VIN = 2.2V Output Ripple (10mV/Div) LX1 (2V/Div) Efficiency (%) 90 80 VIN = 4.5V VIN = 2.5V VIN = 3V VIN = 3.8V 70 60 50 Time (1us/Div) 1 10 100 1000 Output Current (mA) Buck2 Efficiency vs. Output Current 100 Buck2 Efficiency vs. Output Current 100 VOUT = 1.8V VIN = 2.5V 90 VIN = 4.5 80 80 Efficiency (%) Efficiency (%) VOUT = 2.5V 90 VIN = 3V VIN = 4.5 VIN = 3.8V 70 70 60 VIN = 3.8V 50 VIN = 3V 60 40 30 50 1 10 100 Output Current (mA) www.richtek.com 10 1000 1 10 100 1000 Output Current (mA) DS9907-10 April 2011 RT9907 Buck2 Output Voltage vs. VDDM Voltage Buck2 Output Voltage vs. VDD2 Voltage 1.82 1.82 VDD2 = 3.3V, IOUT = 250mA 1.818 1.816 1.816 Output Voltage (V) Output Voltage (V) VBAT = VDDM = 3.3V, IOUT = 250mA 1.818 1.814 1.812 1.81 1.808 1.814 1.812 1.81 1.808 1.806 1.806 1.804 1.804 2 2.5 3 3.5 4 2 4.5 3.5 4 4.5 5 5.5 VDDM Voltage (V) Buck2 Load Transient Response Buck2 Load Transient Response 6 @IOUT = 100mA to 400mA VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V Load Current (200mA/Div) Output Voltage Deviation (100mV/Div) Output Voltage Deviation (100mV/Div) Load Current (200mA/Div) 3 VDD2 Voltage (V) @IOUT = 100mA to 400mA Time (1ms/Div) VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V Time (1ms/Div) DS9907-10 April 2011 Output Voltage Deviation (100mV/Div) Buck2 Load Transient Response Load Current (200mA/Div) Output Voltage Deviation (100mV/Div) @IOUT = 100mA to 400mA VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V Time (1ms/Div) Buck2 Load Transient Response Load Current (200mA/Div) 2.5 @IOUT = 100mA to 400mA VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V Time (1ms/Div) www.richtek.com 11 RT9907 Buck2 LX & Output Ripple Buck2 LX & Output Ripple @IOUT = 250mA Time (500ns/Div) Buck2 LX & Output Ripple Buck2 LX & Output Ripple LX2 (2V/Div) Output Ripple (10mV/Div) @IOUT = 250mA VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V @IOUT = 500mA VDD2 = 3V, VDDM = 3.3V, VOUT = 1.8V Time (500ns/Div) Time (500ns/Div) Buck2 LX & Output Ripple Buck2 LX & Output Ripple LX2 (2V/Div) @IOUT = 250mA VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V Time (500ns/Div) www.richtek.com 12 Output Ripple (10mV/Div) Output Ripple (10mV/Div) VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V Time (500ns/Div) LX2 (2V/Div) Output Ripple (10mV/Div) Output Ripple (10mV/Div) VDD2 = 2.5V, VDDM = 3.3V, VOUT = 1.8V LX2 (2V/Div) Output Ripple (10mV/Div) LX2 (2V/Div) LX2 (2V/Div) @IOUT = 500mA @IOUT = 500mA VDD2 = 3.8V, VDDM = 3.3V, VOUT = 1.8V Time (500ns/Div) DS9907-10 April 2011 RT9907 Buck2 LX & Output Ripple Output Ripple (10mV/Div) Output Ripple (10mV/Div) LX2 (2V/Div) LX2 (2V/Div) Buck2 LX & Output Ripple @IOUT = 250mA VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V @IOUT = 500mA VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V Time (500ns/Div) Time (500ns/Div) Buck3 Efficiency vs. Output Current Buck3 Efficiency vs. Output Current 100 100 VOUT = 1.5V VOUT = 1.8V VIN = 2.2V 90 80 Efficiency (%) Efficiency (%) 90 VIN = 4.5V VIN = 3V VIN = 3.8V 70 VIN = 2.5V 80 VIN = 4.5V VIN = 3.8V VIN = 3V 70 60 60 50 50 1 10 100 1 1000 10 100 1000 Output Current (mA) Output Current (mA) Buck3 Efficiency vs. Output Current Buck3 Output Voltage vs. VDD3 Voltage 100 1.806 VOUT = 2.5V VBAT = VDDM = 3.3V, IOUT = 250mA 1.804 90 Output Voltage (V) VIN = 4.5V 80 Efficiency (%) VIN = 2.5V 70 VIN = 3.8V 60 50 VIN = 3V 40 1.802 1.8 1.798 1.796 1.794 1.792 30 1.79 1 10 100 Output Current (mA) DS9907-10 April 2011 1000 2 2.5 3 3.5 4 4.5 VDD3 Voltage (V) www.richtek.com 13 RT9907 Buck3 Output Voltage vs. VDDM Voltage Buck3 Load Transient Response 1.806 Output Voltage Deviation (100mV/Div) VDD3 = 3.3V, IOUT = 250mA 1.802 1.8 @IOUT = 100mA to 400mA 1.798 1.796 Load Current (200mA/Div) Output Voltage (V) 1.804 1.794 1.792 1.79 2 2.5 3 3.5 4 4.5 5 5.5 VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V 6 Time (1ms/Div) VDDM Voltage (V) VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V Load Current (200mA/Div) Load Current (200mA/Div) Output Voltage Deviation (100mV/Div) @IOUT = 100mA to 400mA Buck3 Load Transient Response Output Voltage Deviation (100mV/Div) Buck3 Load Transient Response VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V Time (1ms/Div) Time (1ms/Div) Buck3 Load Transient Response Buck3 LX & Output Ripple @IOUT = 250mA VDD3 = 4.5V, VDDM = 3.3V, VOUT = 1.8V Time (1ms/Div) www.richtek.com 14 Output Ripple (10mV/Div) LX3 (2V/Div) Output Voltage Deviation (100mV/Div) @IOUT = 100mA to 400mA Load Current (200mA/Div) @IOUT = 100mA to 400mA VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V Time (500ns/Div) DS9907-10 April 2011 RT9907 Buck3 LX & Output Ripple Buck3 LX & Output Ripple Output Ripple (10mV/Div) VDD3 = 2.5V, VDDM = 3.3V, VOUT = 1.8V LX3 Output Ripple (10mV/Div) (2V/Div) @IOUT = 250mA LX3 (2V/Div) @IOUT = 500mA Time (500ns/Div) Time (500ns/Div) Buck3 LX & Output Ripple Buck3 LX & Output Ripple @IOUT = 500mA @IOUT = 250mA VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V LX3 Output Ripple (10mV/Div) (2V/Div) LX3 Output Ripple (10mV/Div) (2V/Div) VDD3 = 3V, VDDM = 3.3V, VOUT = 1.8V VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V Time (500ns/Div) Time (500ns/Div) Buck3 LX & Output Ripple Buck3 LX & Output Ripple VDD3 = 3.8V, VDDM = 3.3V, VOUT = 1.8V Time (500ns/Div) DS9907-10 April 2011 LX3 Output Ripple (10mV/Div) (2V/Div) Output Ripple (10mV/Div) LX3 (2V/Div) @IOUT = 500mA @IOUT = 250mA VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V Time (500ns/Div) www.richtek.com 15 RT9907 Buck3 LX & Output Ripple Output Ripple (10mV/Div) LX3 (2V/Div) @IOUT = 500mA VDD2 = 4.5V, VDDM = 3.3V, VOUT = 1.8V Time (500ns/Div) www.richtek.com 16 DS9907-10 April 2011 RT9907 Application Information The RT9907 is a three-channel DC/DC converter with one voltage detector for digital still cameras and other handheld device. The three 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. 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. TSS = 10 x CSS (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 N-MOSFET turns on by a constant DS9907-10 April 2011 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 N-MOSFET 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 P-MOSFET 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 enters low dropout mode. Duty could be as long as 100% to extend battery life. www.richtek.com 17 RT9907 Protection Thermal Protection Current limit (CH2, CH3) Thermal protection function is integrated in the chip. When the chip temperature is higher than 180°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. The current of high-side P-MOSFET is sensed cycle by cycle to prevent over current. If the current is higher than 1.5A (typical), then the high-side P-MOSFET is off and the low-side N-MOSFET 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 P-MOSFET is off and low-side N-MOSFET is on. This status is latched and could be reset by toggling ENM. 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. www.richtek.com 18 DS9907-10 April 2011 RT9907 Outline Dimension D2 D SEE DETAIL A L 1 E E2 e b 1 1 2 2 DETAIL A Pin #1 ID and Tie Bar Mark Options A A3 A1 Note : The configuration of the Pin #1 identifier is optional, but must be located within the zone indicated. Symbol Dimensions In Millimeters Min Dimensions In Inches 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 3.950 4.050 0.156 0.159 D2 2.300 2.750 0.091 0.108 E 3.950 4.050 0.156 0.159 E2 2.300 2.750 0.091 0.108 e L 0.500 0.350 0.020 0.450 0.014 0.018 V-Type 24L QFN 4x4 Package Richtek Technology Corporation Richtek Technology Corporation Headquarter Taipei Office (Marketing) 5F, No. 20, Taiyuen Street, Chupei City 5F, No. 95, Minchiuan Road, Hsintien City Hsinchu, Taiwan, R.O.C. Taipei County, Taiwan, R.O.C. Tel: (8863)5526789 Fax: (8863)5526611 Tel: (8862)86672399 Fax: (8862)86672377 Email: [email protected] Information that is provided by Richtek Technology Corporation is believed to be accurate and reliable. Richtek reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. No third party intellectual property infringement of the applications should be guaranteed by users when integrating Richtek products into any application. No legal responsibility for any said applications is assumed by Richtek. DS9907-10 April 2011 www.richtek.com 19