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Datasheet

Datasheet

BM2PXX5F/BM2PXX6F/BM2PXX7F/BM2PXX8F Series

TSZ02201-0F2F0A200210-1-2

28.Oct.2016.Rev.002

© 2012 ROHM Co., Ltd. All rights reserved.

www.rohm.com

TSZ22111・15・001

(4) DCDC driver (PWM comparator, frequency hopping, slope compensation, OSC, burst)

BM2PxxxF has a current mode PWM control.

An internal oscillator sets a fixed switching frequency (65 kHz Typ).

BM2PxxxF has an integrated switching frequency hopping function, which causes the switching frequency to fluctuate as

shown in figure 10 below.

The fluctuation cycle is 125 Hz (Typ).

Figure 10. Frequency Hopping Function

Maximum duty cycle is fixed at 75% (Typ) and minimum pulse width is fixed at 400 ns (Typ).

In current mode control, sub-harmonic oscillation may occur when the duty cycle exceeds 50%.

As a countermeasure, this IC has built-in slope compensation circuits.

This IC has built-in burst mode and frequency reduction circuits to achieve lower power consumption when the load is light.

(Only BM2P0xxF series have frequency reduction circuits )

FB pin voltage is changed by secondary output voltage (secondary load power).

FB pin is monitored, burst mode operation and frequency detection start.

Figure 11 shows the FB voltage, and the DCDC switching frequency operation.

＜

BM2P0xxF＞

＜

BM2PAxxF＞

・

mode1 : Burst operation

・

mode1 : Burst operation

・

mode2 : Frequency reduction operation

・

mode2 : Fixed frequency operation

( operates at max frequency)

・

mode3 : Fixed frequency operation

・

mode3 : Fixed frequency operation

(operates at max frequency)

(operates at max frequency)

・

mode4 : Overload operation

・

mode4 : Overload operation

(detects the overload state and stops the pulse operation)

(detects the overload state and stops the pulse operation)

Figure 11-1. Switching Operation State Changes by FB Pin Voltage

Figure 11-2. Switching Operation State Changes by FB Pin Voltage

( BM2P0xxF series)

( BM2PAxxF series)