R1243x Series

30V Input 2A Buck DC/DC Converter

Data Sheet / Flyer
Data Sheet * Flyer

The R1243x Series is the CMOS-based Step-Down DC/DC Converter with internal Nch high side Tr. (0.175Ω), which can provide the maximum 2A output current. The IC consists of an Oscillator, a PWM control circuit, a Reference Voltage unit, an Error amplifier, phase compensation circuits, a slope circuit, a soft start circuit, protection circuits, internal voltage regulators, and a switch for bootstrap circuit. The R1243x Series can make up a Step-Down DC/DC Converter with the following external components: an inductor, resistors, a diode, and capacitors.

The R1243x series are current mode operating type DC/DC converter which does not require external current sense resistor, and it works high speed response time, high efficiency and compatible with ceramic capacitors.

There are two types for the oscillator frequency. A/B version's frequency is fixed 1000kHz, and C/D version's frequency is fixed 330kHz.As a protection function, it has cycle by cycle peak current limit function, short protection function, thermal shutdown function and UVLO.

There are two types for short protection, A/C version has latch protection function with 2ms delay time, and B/D version has fold back protection function that keep operating at short condition with lower operating frequency and limiting the Lx current.

The R1243 Series has the built-in soft start time (Typ. 0.4ms). In addition to this, the soft start time is adjustable by adding an external capacitor. The R1243x Series has the FLG pin, which mainly monitors the FB pin voltage and gives the flag output by the Nch open drain if the abnormal condition is detected.

Since the packages for these ICs are HSOP-8E, and DFN(PLP)2527-10, therefore high density mounting of the ICs on boards is possible.

Operating Voltage 4.5V ~ 30V
Standby Function Typ. 0μA, Max. 10μA (VIN =30V, CE="L")
Supply Current Typ. 0.7mA (VIN=30V VFB=1.0V)
Output Voltage Range 0.8V ~ 18V (Adjustable with external resistor)
Feed Back Voltage 0.5V with 1.4% accuracy
Output Current Max. 2A
Peak Current Limit Function Typ. 3.8A
Internal Nch MOSFET Driver Typ. 175mΩ
Maximum Duty Cycle Min. 85%
Operating Frequency Ver.A/B 1000kHz, Ver.C/D 330kHz
Short protection delay time for Output Latch Typ. 2ms : Ver.A/C
Built-in Foldback Protection and its Frequency 1/4 frequency at fold condition : Ver.B/D
Ver.B 250kHz, Ver.D 82.5kHz
Internal Soft Start Time Typ. 0.4ms, with TSS pin open
External Soft Start Time Typ. 12ms, with CSS=0.1μF
Flag Output Function Typ. 0.25ms, FLG “OFF” delay time
UVLO Released Voltage Typ. 4.0V
Thermal Shutdown Function Typ. 160°C, with 35°C hysteresis
Package HSOP-8E, DFN(PLP)2527-10
  • *)This is an approximate value, because output current depends on conditions and external parts.
  • Power source for digital home appliance
  • Power source for hand-held communication equipment, cameras, video instruments such as VCRs, camcorders.
  • Power source for battery-powered equipment.
  • Battery Charger

Data Sheet Flyer Package Info. Mark Info. Quality Assurance Data
R1243x Series R1243x Series HSOP-8E R1243S Reliability
DFN(PLP) 2527-10 R1243K Reliability

All PDF files are less than 1MB unless otherwise stated.

  • Buy Products / Order Sample


Ricoh semiconductor products are available at those dealers.


Page Top