BD9873CP-V5E2 ROHM [Rohm], BD9873CP-V5E2 Datasheet - Page 4

• Manufacturer Part Number: BD9873CP-V5E2
• Description: Simple Step-down Switching Regulators with Built-in Power MOSFET
• Manufacturer: ROHM [Rohm]

●Block Function Explanations
●Notes for PCB layout
© 2009 ROHM Co., Ltd. All rights reserved.
BD9873CP-V5,BD9874CP-V5
www.rohm.com
• Place capacitors between Vcc and Ground, and the Schottky diode as close as possible to the IC to reduce noise and
• Connect resistors between INV and Ground, and the output capacitor filter at the same Ground potential in order to stabilize
（If the patterning is longer or thin, it’s possible to cause ringing or waveform crack.）
maximize efficiency.
the output voltage.
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VREF
OSC
Error AMP
PWM COMP
DRIVER
STBY
Thermal Shutdown (TSD)
Over Current Protection (OCP)
Soft Start (SS)
Generates the regulated voltage from Vcc input, compensated for temperature.
Generates the triangular wave oscillation frequency (900kHz) using an internal resistors and capacitor. Used for PWM
comparator input.
This block, via the INV pin, detects the resistor-divided output voltage, compares this with the reference voltage, then
amplifies and outputs the difference.
Outputs PWM signals to the Driver block, which converts the error amp output voltage to PWM form.
This push-pull FET driver powers the internal Pch MOSFET, which accepts direct PWM input.
Controls ON/OFF operation via the STBY pin. The output is ON when STBY is High.
This circuit protects the IC against thermal runaway and damage due to excessive heat. A thermal sensor detects the
junction temperature and switches the output OFF once the temperature exceeds a threshold value (175°C).
Hysteresis is built in (15°C) in order to prevent malfunctions due to temperature fluctuations.
The OCP circuit detects the voltage difference between Vcc and OUT by measuring the current through the internal
Pch MOSFET and switches the output OFF once the voltage reaches the threshold value. The OCP block is a
self-recovery type (not latch).
This block conducts soft start operations. When STBY is High and the IC starts up the internal capacitor begins
charging. The soft start time is fixed at 5ms.
C1：100uF
R2:1kΩ
C2：4.7uF
1
VCC
INV
4
R1:4kΩ
C3：0.47uF
GND
Fig.3
3
STB Y
OUT
4/12
2
5
L1：100uH
D1
C4：680uF
5.0V
Technical Note
2009.07 - Rev.A