ROHM’s New Energy-Saving DC-DC Converter ICs Offered in the TSOT23 Package
Compact size reduces component area by 72%, contributing to smaller power supplies in consumer and industrial equipment


ROHM has developed four new compact DC-DC step-down converter ICs suitable for consumer and industrial applications, including refrigerators, washing machines, PLCs, and inverters. ROHM is expanding the lineup which includes the BD9E203FP4-Z, a 2A buck converter with switching frequency of 350kHz.

In recent years, increasing application functionality in consumer devices and industrial equipment is driving the demand to minimize board space, resulting in a rise in the adoption rate of compact DC-DC converter ICs.

Furthermore, as reducing standby power consumption is becoming a significant challenge, there is a growing need for DC-DC converter ICs to deliver higher efficiency during light load (low power) conditions. To meet these demands, ROHM developed products that achieve higher efficiency in an even smaller package than existing SOP-J8 (JEDEC standard: SOIC8 equivalent) products.

The new converter ICs deliver an output current of 1A to 3A in the compact TSOT23 package (2.8mm × 2.9mm). This reduces component area by up to 72% compared to the general SOP-J8 package (4.9mm × 6.0mm), contributing to the miniaturization of power supply blocks. On top, adopting a flip chip on lead frame TSOT23 package design enables high-efficiency operation by eliminating bond wire resistance.

The BD9E105FP4-Z, BD9E202FP4-Z, and BD9E304FP4-LBZ also utilize a COT control mode during light load operation. As a result, efficiency during light load operation is improved over standard products, making them ideal for applications requiring low standby power consumption.

Going forward, ROHM will continue to focus on developing products that leverage analog design technologies, contributing to greater miniaturization and energy efficiency in consumer and industrial equipment applications.

Package Area Comparison
Power Conversion Efficiency Comparison

TSOT23 Package Product Lineup

Part No. Data
Max. Input
NewBD9E105FP4-Z PDF 30 4.5 to 28 0.1VIN / 0.7 to 0.8VIN 1 500 - - -40
NewBD9E202FP4-Z PDF 30 4.5 to 28 0.1VIN / 0.7 to 0.8VIN 2 500 - -40
☆BD9E203FP4-Z - 350 - -
NewBD9E304FP4-LBZ PDF 39 4.5 to 36 0.1VIN / 0.7 to 0.8VIN 3 300 - - -40
NewBD9A201FP4-LBZ PDF 7 2.7 to 5.5 0.8 to 0.7VIN 2 1000 - -

☆: Under Development

Application Examples

3.3V/5V/12V/24V power supply applications
Consumer Appliances:

Refrigerators, washing machines, air conditioners, etc.
Industrial Equipment:
PLCs (Programmable Logic Controllers), inverters, AC servos, etc.

Input Power Rail Voltage vs Output Current (TSOT23 Package Products)

Online Sales Information

Sales Start Date: March 2024 (in succession)
Pricing: $3.0/unit (samples, excluding tax)
Online Distributors: DigiKey, Mouser and Farnell
The products will be offered at other online distributors as they become available.

Online Distributors

  • DigiKey
  • Mouser
  • Farnell

Product Information

In addition to the ICs, evaluation boards together with various support tools are available that enable immediate evaluation during application design.

Product Part No. Evaluation Board
BD9E105FP4-Z BD9E105FP4-EVK-001 12V to 24V input, 5V/1A output
BD9E202FP4-Z BD9E202FP4-EVK-001 4.5V to 28V input, 0.7V to VIN x 0.8V/2A output
BD9E304FP4-LBZ BD9E304FP4-EVK-001 12V input, 1.2V/3A output
BD9E304FP4-EVK-002 24V input, 12V/3A output
BD9E304FP4-EVK-003 12V input, 5V/3A output
Preparation in progress
BD9A201FP4-EVK-001 5V input, 1.8V/2A output

Evaluation Boards

Online Distributors: DigiKey, Mouser and Farnell

Various Support Tools

• Calculation Sheet:A calculation tool for application circuits that facilitates external constant design. By setting values as described, users will be able to determine the circuit parameters that satisfy the desired characteristics.
The sheet is available for download from the ‘Tools’ section on each product page on ROHM’s website.
[BD9E105FP4-Z / BD9E304FP4-LBZ / BD9A201FP4-LBZ]

ROHM Solution SimulatorA free simulation tool that runs on ROHM’s website. Changing the external constants in the topology described in the datasheet allows the optimal solution for frequency response (for a power supply) to be considered.
[BD9E105FP4-Z / BD9E202FP4-Z / BD9E304FP4-LBZ / BD9A201FP4-LBZ]

*Logging in to MyROHM is required to use the tool.

• Other Content: SPICE models for circuit simulation along with application notes that contain useful information on thermal design, circuit design, and verification can also be downloaded from each product page.


COT (Constant ON Time) Control Method
A feedback circuit control method for stabilizing the output voltage. When the feedback voltage drops below the reference voltage, the switching element turns ON, then automatically turns OFF after a fixed time has elapsed. This enables stable output to be efficiently obtained at light loads.
Unnecessary electromagnetic waves that deviate from the originally required predetermined frequency.
Overshoot Prevention Function
If the output current of the power supply IC exceeds the expected value, the output is shut down by the OCP (overcurrent protection) function. When recovering from a shutdown, a momentary overshoot (excessive output voltage) occurs, causing a delay in recovery, so it is necessary to expedite recovery and suppress overshoot.
ESD (Electrostatic Discharge)
Static electricity (surge) is generated when electrically charged objects come into contact with each other. This static electricity (surge) may cause circuits and equipment to malfunction or destruction.
EMI (Electromagnetic Interference)
EMI is used as an indicator for how much noise is generated when operating the target product, which may cause problems in surrounding ICs and systems. ‘Good EMI characteristics’ mean that less noise is generated.

Featured Products

Featured Products
Compact SOT23 Package
Energy-Saving Buck DC-DC Converter ICs
BD9ExxxFP4-Z, BD9E304FP4-LBZ, BD9A201FP4-LBZ (PDF: 1.1MB)