Charge-Pump for White LED and Power Supply RN5T651 Series
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Charge-Pump for White LED and Power Supply Electronic Devices Company This specification is subject to change without notice.

RN5T651 Charge-Pump for White LED and Power Supply

RN5T651 Charge-Pump for White LED and Power Supply

RN5T651 Charge-Pump for White LED and Power Supply RN5T651 contains constant frequency charge pump to optimize for white LED application, step-down DC/DC converter and two low-noise LDOs. Output enable/disable, LEDs current setting and LDO output voltage setting are individually controllable through I2C. • Power Supply Function S Step-down DC/DC converter x 1 (ON/OFF programmable) S Over current Protection (ALL Regulators) and thermal shutdown • White LED Charge Pump S Current capability: All currents capability 450mA S Four Main LEDs at 25mA max. S Individual LEDs current value setting S...

RN5T651 Charge-Pump for White LED and Power Supply

RN5T651 Charge-Pump for White LED and Power Supply 4. Block Diagram VIN1 C2P VIN2 LX V CORE Charge Pump DC/DC Step-down Thermal Shutdown

RN5T651 Charge-Pump for White LED and Power Supply

RN5T651 Charge-Pump for White LED and Power Supply 6. Functional Blocks 6.1 Regulators 6.1.1 LDO1 Electrical Characteristics VBATT = 3.6V, CREFO = 1μF, Ta = 25℃ Operating Conditions (unless otherwise specified) Output Voltage Output Current Current Limit Drop-out Voltage Line Regulation Load Regulation Output Voltage Temperature Coefficient Ripple Rejection Bypass Capacitor Supply Current Programmable Output Voltage Table 6-1 LDO1 Electrical Characteristics Note*: Bypass capacitor: 2.2μF, in mounted state. For optimized phase compensation, the bypass capacitor must be the ceramic type.

RN5T651 Charge-Pump for White LED and Power Supply 6.1.2 LDO2 Electrical Characteristics VBATT = 3.6V, CREFO = 1μF, Ta = 25℃ Operating Conditions (unless otherwise specified) Output Voltage Output Current Current Limit Drop-out Voltage Line Regulation Load Regulation Output Voltage Temperature Coefficient Ripple Rejection Bypass Capacitor Supply Current Programmable Output Voltage Table 6-2 LDO2 Electrical Characteristics Note*: Bypass capacitor: 2.2μF, in mounted state. For optimized phase compensation, the bypass capacitor must be ceramic type. Note*1: Vref Block Supply Current typ 20μA...

RN5T651 Charge-Pump for White LED and Power Supply 6.2 Step-down DC/DC Converters The output voltage is decided according to the resistance ratio of external resistor. Please refer to the formulas in section 6.2.2 for the output voltage set. It can be easily composed of DC/DC converters with only few kinds of external components such as inductor, capacitor and etc. For the output capacitors, ceramic type is recommended for voltage ripple. Max Duty circuit limits maximum pulse width of DC/DC. Current Limit circuit limits peak current of LX at clock cycle of DC/DC. Latch type protection...

RN5T651 Charge-Pump for White LED and Power Supply 6.2.3 Step-down DC/DC Convertors Electrical Characteristics Operating Conditions (unless otherwise specified) VBATT= 3.6V, CREFO = 1 (XF, Ta= 25°C Table 6-3 Step-down DC/DC Converter Electrical Characteristics Note* 1: The output voltages are selectable in ranges 1.2- 2.6V by trimming. 6.2.4 (Reference waveform) Soft-start Waveforms (simulation result) DC/DC Output Wave Form I 20us 1 80us 1 Enable Internal Signal "L": Active 'Warm Up 1 Rising Time 1

RN5T651 Charge-Pump for White LED and Power Supply 6.3 Thermal Shutdown Circuit The thermal shutdown circuit is consisted of two temperature detection circuits and an op-amp. 6.3.1 Thermal Shutdown Block Diagram VIN Temperature Detection Circuit Temperature Detection Circuit To Power-on Control Circuit Control Circuit Fig 6-2 Thermal Shutdown Circuit Diagram 6.3.2 Thermal Shutdown Explanation of Operation The overheat state can be detected by comparing the output voltages from two temperature detection circuits, which have different temperature Characteristics. If the overheat state is...

RN5T651 Charge-Pump for White LED and Power Supply RN5T651 charge pump drives up to six white LEDs and one strobe with regulated constant current for uniform Charge Pump Fig 6-3 Charge Pump Circuit Diagram

RN5T651 Charge-Pump for White LED and Power Supply 6.4.2 Operation Initial and 1x mode When any channel is turned ON, charge pump output (VOUT) voltage becomes VIN1 voltage. In this time, Soft-start prevents the inrush current. As a result, RN5T651 starts at 1x mode. In 1x mode, the following relation is the condition to stay in 1x mode. VOUT - Vf > 0.25V Here, VOUT and Vf mean output of Charge pump and forward voltage of white LED, respectively. 0.25V means mode transition threshold, in case of setting at 25mA of Main or Sub. 1x or 1.5x transition When the battery voltage decreases and...

RN5T651 Charge-Pump for White LED and Power Supply 6.4.3 Protection circuit When any DIN_ pin is floating or grounded, VOUT voltage is limited below protection voltage by gating on/off charge pump. In case any LED fails as an open circuit, VOUT voltage is also limited. Besides, when VOUT is smaller than approximately 1.2V, charge pump also stops. 6.4.4 Unused DIN_ pin In case that there is any unused DIN_ pin, connect DIN_ to GND to avoid over voltage protection status. 6.4.5 Soft-start When LEDs are turned ON, to prevent the inrush current, RN5T651 has Soft-start function. (The internal...

RN5T651 Charge-Pump for White LED and Power Supply 6.4.6 Charge Pump Electrical Characteristics Unless otherwise specified, VIN=3.6V, Ta=25℃, C1=C2=1uF, Cout=2.2uF Charge Pump Operating Voltage VOUT voltage (Over voltage) Over voltage detection hysteresis Maximum Output current Switching Frequency Soft-start time 1x mode, No load, (DET, Reference ON) Supply current Standby supply current Current Limit VOUT shorted LED Driver Maximum Sink current LED current accuracy (Main, Sub) LED current accuracy (Flash) Chattering noise reduction Table 6-5 Charge Pump Electrical Characteristics Note*1:...

RN5T651 Charge-Pump for White LED and Power Supply 6.4.7 STBB Logic Input STBB input is used to control the flash LEDs without accessing I2C. When STBB is driven to "L", the flash LEDs are driven by the current set in Strobe Luminance register. Driving STBB low overrides the flash LEDs set by I2C. With STBB high, the flash LEDs becomes controllable by I2C. Selecttor Flash Luminance Strobe Luminance 6.5 UVLO(Under Voltage Lock Out) CREFO = 1μF, Ta = 25℃ Operating Conditions (unless otherwise specified) Symbol Under voltage lock out threshold VCCVIN rising Under voltage lock out threshold...