R1287x Series

PWM/VFM, Dual-channel Step-up/Inverting DC/DC Converter with Synchronous Rectifier for LCD

Data Sheet
Data Sheet
(1.43MB)

The R1287x is a CMOS-based PWM/ VFM dual-channel step-up/ inverting DC/DC converter with synchronous rectifier for LCD. The step-up DC/DC converter (CH1) generates a 4.5V to 5.8V boosted output voltage and the inverting DC/DC converter (CH2) generates a −4.5V to −6.0V inverting output voltage.

Internally, the R1287x consists of an oscillator circuit, PWM control circuits, a reference voltage unit, error amplifiers, soft-start circuits, a LX peak current limit circuit, short protection circuits, thermal shutdown circuit, an under voltage lockout circuit (UVLO), a NMOS transistor driver and a synchronous PMOS transistor driver for CH1, and a PMOS transistor driver and a synchronous NMOS transistor driver for CH2.

The R1287x is employing synchronous rectification for improving the efficiency of rectification by replacing diodes with built-in switching transistors. Using synchronous rectification not only increases circuit performance but also allows a design to reduce parts count.

The R1287x provides the normal PWM control or the PWM/VFM auto switching control. The PWM normal 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 R1287x can achieve both low ripple voltage at light load and high efficiency.

Both CH1 and CH2 can independently control the ON/OFF control and freely set the starting sequence and shutdown sequence.

Both CH1 and CH2 own an auto-discharge function which actively discharges the output voltage to ground when the device is placed in shutdown mode.

The R1287x is offered in a 12-pin WLCSP-12-P1 package and a 12-pin DFN3030-12 package.

  • Operating Voltage Range
2.5V to 5.5V
  • [ Step-up DC/DC Converter (CH1) ]
  Selectable Step-up Output Voltage (VOUTP) R1287xxxxy: 4.5V to 5.8V (0.1V Step)
Step-up Output Voltage (Externally adjustable) R1287x001y: 4.5V to 5.8V
Maximum Output Current (Dependent on inductance) R1287xxxxB/D: 200mA
R1287xxxxC: 100mA
  • [ Inverting DC/DC Converter (CH2) ]
  Selectable Step-up Output Voltage (VOUTN) R1287xxxxy: −4.5V to −5.8V (0.1V Step)
Inverting Output Voltage (externally adjustable) R1287x001y: −4.5V to −6.0 V
Maximum Output Current (dependent on inductance) R1287xxxxB/D: 200mA
R1287xxxxC: 100mA
  • [ Controller ]
  ON/OFF Control: Operates CH1/CH2 separately by the EN1/EN2 pin.
Auto-discharge Function: Discharges the output voltage to GND within a short time in shutdown mode.
Latch-type Short Circuit Protection: Short-circuiting of either one of CH1 or CH2 activates this circuit.
  • Maximum Duty Cycle
  • LX Peak Current Limit Function
  • Undervoltage Lockout (UVLO) Threshold
Typ. 2.25V
  • Thermal Shutdown Temperature
Typ. 150°C
  • Oscillator Frequency
R1287xxxxB/D: 1MHz
R1287xxxxC: 300kHz
  • Package
WLCSP-12-P1, DFN3030-12
  • Power source for hand-held equipment
  • Power source for LCD
Data Sheet Flyer Design Guide Package Info. Quality Assurance Data
R1287x Series R1287x Series R1287Zxxxy Series WLCSP-12-P1 to be prepared
DFN3030-12 Reliability

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