RP901K Series

Synchronous Step-down DC/DC Converter with VD and VR

Data Sheet / Flyer
Data Sheet * Flyer

The RP901xxxx is a CMOS-based current mode PWM control synchronous step-down DC/DC converter with a voltage detector (VD) and an LDO regulator (VR).

Each of Step-down DC/DC converters is composed of an oscillator, a voltage reference unit, an error amplifier, a switching control circuit, a soft-start circuit, a protection circuit, a UVLO circuit, a switching transistor. Due to the switching elements are built in and synchronous control, a high efficiency step-down DC/DC converter can be made with an inductor and capacitors. To realize high efficiency at light load, automatic PWM/VFM alternative mode can be selected other than the PWM fixed control mode.

As protection circuits, a current limit circuit which limits Lx peak current cycle by cycle and a hiccup mode protection circuit which works if the load current over the limit continues for a certain time*1 are built in. The output voltage can be preset with 0.05V step in the factory due to the built-in feed back resistance, and the tolerance is ±2%. Since the package is DFN (PLP) 2527-10, high density mounting on board is possible.

Built-in LDO regulator (VR) is composed of a voltage reference unit, a voltage detecting resistor-network, an error amplifier, a short current limit circuit, and a driver transistor. After the soft-start time of the DC/DC converter is over and a specified delay time, LDO starts up. The sequence function is fixed internally*2.

Built-in voltage detector (VD) supervises the input voltage or the output of the VR (The reset function works for UVLO and over-current of the DC/DC converter). The option is preset in the factory. The output type is N-channel open drain. The released delay time is built-in, typ.50ms.

If the junction temperature of the IC is over the limit, the system is reset by the built-in thermal shut-down circuit.

  • *1 A version: As soon as the load current is over the limit, the system restarts by the protection.
  • *2 C, D versions: No sequence function
Input Voltage Range 4.5V to 5.5V
Supply Current Typ. 460µA (at PWM mode)
Typ. 170µA (at light load applied to B, C, D versions)
Step-down DC/DC Converter  
  Output Voltage Range 1.2V to 1.8V, preset is possible by user's request
Output Voltage Tolerance ±2%
Oscillator Frequency Typ. 1.2MHz
Built-in driver ON resistance Typ. P-channel 0.25Ω, N-channel 0.25Ω (at VIN=5V)
Soft-start function Typ. 1ms
Lx peak current limit function Typ. 1.4A (D version: 1.5A)
Output Current Min. 800mA (D version: 900mA)
Protection Delay Time Typ. 0.1ms (applied to B, C, D versions)
UVLO function Typ. 3.5V
Chip enable function "H" active
LDO Regulator  
  Output Voltage Range 2.5V to 3.3V, preset is possible by user's request
Output Voltage Tolerance ±1.0%
Output Current Min. 600mA
Start-up delay time Typ. 2ms (applied to A, B versions)
Auto-Discharge function at turning off Discharge resistance Typ.50Ω (at VIN=5V)
  Voltage Detector Threshold Range 2.0V to 3.0V, preset is possible by user's request
(A version: VR output voltage is supervised),
3.0V to 5.0V, preset is possible by user's request
(B, C, D versions: Input voltage is supervised)
Released Delay Time Typ.50ms
Thermal shutdown circuit Typ.50, Detecting Temperature: Typ. 165°C,
Released temperature: Typ. 110°C
Package DFN(PLP)2527-10
External Components CIN: 10.0µF, COUT1=10.0μF, L=4.7µH (DC/DC),
  • Optical Disk Equipment

Data Sheet Flyer Package Info. Mark Info. Quality
Assurance Data
RP901K Series
RP901K Series DFN(PLP)2527-10 RP901K Reliability

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