PWM/ VFM Step-up DC/DC Converter for White LED Applications
The R1214Z is a CMOS-based low supply current PWM/ VFM step-up DC/DC converter. Internally, the device consists of an Nch MOSFET driver, an oscillator, a PWM comparator, a voltage reference unit, an error amplifier, an overcurrent protection circuit, an under voltage lockout circuit (UVLO), an overvoltage protection circuit (LXOVP, LEDOVP), a thermal shutdown protection circuit and 2-channel current drivers for white LEDs.
The R1214Z requires minimal external component count. By simply using an inductor, a resistor, capacitors and a diode, the white LEDs can be driven with constant current and high efficiency. The LED current can be determined by the value of current setting resistor. The brightness of the LEDs can be adjusted quickly by applying a 200Hz to 300kHz PWM signal to the PWM pin.
The R1214Z provides the PWM control or the PWM/VFM auto switching control. The PWM control switches at fixed frequency rate in low output current in order to reduce noise. Likewise, the PWM/VFM auto switching control automatically switches from PWM mode to VFM mode in low output current in order to achieve high efficiency. RICOH’s unique control method can suppress a ripple voltage in the VFM mode, thus the R1214Z can achieve both low ripple voltage at light load and high efficiency.
The R1214Z provides an overcurrent protection circuit to limit the LX peak current, an UVLO circuit to prevent the malfunction of the device at low input voltage, a LXOVP circuit to monitor the excess LX voltage, a LEDOVP circuit to monitor the excess LED1-2 voltage and a thermal shutdown protection circuit to detect the overheating of the device and stops the operation to protect the device from damage.
The R1214Z is offered in a 9-pin WLCSP-9-P1 package.
|Input Voltage Range (Maximum Rating)||2.7V to 5.5V (6.5V)|
|Supply Current||Typ. 500µA|
|Standby Current||Typ. 0.2µA, Max. 5µA|
|Lx Current Limit||Typ. 2A|
|Overcurrent Protection Circuit||Typ. 1.9A|
|Overvoltage Protection (OVP) Circuit||Typ. 35V|
|LED1-2 Current Matching Circuit||Max. 0.5% (R1214Zxx1C/D, 20mA)
Max. 1.0% (R1214Zxx1A/B, 20mA)
|Oscillator Frequency||Typ. 750 kHz/ 450 kHz|
|Maximum Duty Cycle||Typ. 96% (R1214Zx11x)
Typ. 94% (R1214Zx21x)
|Nch ON Resistance||Typ. 0.25Ω (VIN = 3.6V)|
|Undervoltage Lockout (UVLO) Circuit||Typ. 2.4V|
|Thermal Shutdown Circuit||Typ. 150°C|
|LED Dimming Control||By sending a 200Hz to 300kHz PWM signal to the PWM pin|
- ・White LED backlight driver for LCD displays for portable equipment
- ・White LED backlight driver for LCD displays for Smartphones, Tablets and Note PCs
|Data Sheet||Flyer||Design Guide||Package Info.||Quality Assurance
|to be prepared|
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