BD9007F View Datasheet(PDF) - ROHM Semiconductor

Part Name

Description

Manufacturer

BD9007F

Flexible Step-down Switching Regulators with Built-in Power MOSFET

ROHM Semiconductor 

BD9006F, BD9006HFP, BD9007F, BD9007HFP

Technical Note

●Description of operations

・ERROR AMP

The ERROR AMP block is an error amplifier used to input the reference voltage (0.8V Typ.) and the INV pin voltage. The

output FB pin controls the switching duty and output voltage Vo. These INV and FB pins are externally mounted to

facilitate phase compensation. Inserting a capacitor and resistor between these pins enables adjustment of phase margin.

(Refer to recommended examples on pages 11~13.)

・SOFT START

The SOFT START block provides a function to prevent the overshoot of the output voltage Vo through gradually

increasing the normal rotation input of the error amplifier when power supply turns ON to gradually increase the switching

Duty. The soft start time is set to 5msec (Typ.).

・SYNC

By making the “EN/SYNC” terminal less than 0.8V, the circuit can be shut down.

Furthermore, by applying pulse with higher frequency than the configured oscillation frequency to the “EN/SYNC”

terminal, external sync is possible. (Sync possible with double the configured frequency-configured frequency or 500kHz)

・OSC(Oscillator)

This circuit generates the pulse wave to be input to the slope, and by connecting resistance to “RT”, 50~500kHz

oscillating frequency can be configured. (Refer to p.11 Fig.24)

・slope

This block generates saw tooth waves from the clock generated by the OSC. The generated saw tooth waves are sent

to PWM COMPARATOR.

・PWM COMPARATOR

The PWM COMPARATOR block is a comparator to make comparison between the FB pin and internal saw tooth wave

and output a switching pulse

The switching pulse duty varies with the FB value. (min Duty width : 250ns.)

・TSD (Thermal Shut Down)

In order to prevent thermal destruction/thermal runaway of the IC, the TSD block will turn OFF the output when the chip

temperature reaches approximately 150℃ or more. When the chip temperature falls to a specified level, the output will be

reset. However, since the TSD is designed to protect the IC, the chip junction temperature should be provided with the

thermal shutdown detection temperature of less than approximately.150℃.

・CURRENT LIMIT

While the output POWER P-ch MOS FET is ON, if the voltage between drain and source (ON resistance×load current)

exceeds the reference voltage internally set with the IC, this block will turn OFF the output to latch. The overcurrent

protection detection values have been set as shown below:

BD9006F,BD9006HFP, BD9007F,BD9007HFP ・・・ 4A (Typ.)

Furthermore, since this overcurrent protection is an automatically reset, after the output is turned OFF and latched, the

latch will be reset with the RESET signal output by each oscillation frequency.

However, this protection circuit is only effective in preventing destruction from sudden accident. It does not support for the

continuous operation of the protection circuit (e.g. if a load, which significantly exceeds the output current capacitance, is

normally connected). Furthermore, since the overcurrent protection detection value has negative temperature

characteristics, consider thermal design.

www.rohm.com

© 2009 ROHM Co., Ltd. All rights reserved.

8/17

2009.05 - Rev.A

Share Link: