R1225 Series
18.5V Input PWM/VFM Step-down DC/DC Controller

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  • Description

    The R1225 Series are low supply current CMOS-based PWM/VFM controlled step-down DC/DC controllers with an external output transistor. By simply using a power transistor, an inductor, a diode, and a capacitor as external components, a high-efficiency step-down DC/DC converter can be easily configured. The PWM/VFM alternative circuit automatically switches to VFM control in the smaller output current range and provides high efficiency even in the smaller output current range. The version with fixed PWM control is also available.

    The latch type protection circuit embedded into the device latches the power MOS in the "OFF" state when the oscillator maximum duty cycle continues for a predetermined period of time. Protection time is adjustable by the capacity of an external capacitor of the DLY pin.

    R1225 also includes an under-voltage lockout circuit (UVLO) that stops DC/DC operation and prevents malfunction when the supply voltage falls below the UVLO detector threshold and reduces supply current.

  • Spec
    Input Voltage Range 2.3 V to 18.5 V (20.0 V)
    Operating Temperature Range -40°C to 85°C (125°C)
    Supply Current Typ. 20 µA (R1225Nxx2A/B/J/K)
    Typ. 30 µA (R1225Nxx2C)
    Typ. 40 µA (R1225Nxx2D)
    Standby Current Typ. 0 µA
    Output Voltage Range 1.2 V to 6.0 V (0.1 V step)
    Output Voltage Accuracy ±2% (Ta = 25°C)
    Output Voltage Temperature Coefficient Typ. ±100 ppm/°C
    Oscillator Frequency Typ. 180 kHz, 300 kHz, 500 kHz
    Efficiency Typ. 90%
    Package SOT-23-6W

    Protections / Functions

    TSD ILX OCP OVP UVLO OVLO Reverse Shutdown Soft Start SSCG PGOOD Auto Discharge Anti-ringing Sequencing Max Duty Ext. Phase LED Adjust
  • Technical
    • R1225Nxx2x Typical Application

      R1225Nxx2x Typical Application

      L: 27µH, C1: 10µF, C2: 0.1µF, C3: 47µF, C4: 0.02µF, R1: 10Ω

    • R1225N332A Efficiency vs. Output Current

      R1225N332A Efficiency vs. Output Current

  • Quality &
    • Refer to the datasheets for the details on the product.
    • The package file includes package dimensions, taping specifications, taping reels dimensions, power dissipations, and recommended land pattern.
    • Please contact us or our distributors for unpublished reliability information.

Download Datasheet

Functional Description

TSD Thermal Shutdown Function
ILX LX Current Limit Function
OCP Overcurrent Protection
OVP Overvoltage Protection
UVLO Undervoltage Lockout Protection
OVLO Overvoltage Lockout Protection
Reverse Reverse Current Protection Circuit
Shutdown Shutdown Function
Soft Start Soft Start Function
SSCG Spread Spectrum Clock Generator Function
PGOOD Power Good Output
Auto Discharge Auto Discharge Function
Anti-ringing Anti-ringing Switch Function
Sequencing Start-up Sequencing Control
Max Duty Maximum Duty Cycle
Ext. Phase Externally Adjustable Phase Compensation
LED Adjust LED High-speed Dimming Control

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