M51995AFP datasheet(34/43 Pages) RENESAS

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M51995AP/AFP

REJ03D0835-0300 Rev.3.00 Jun 06, 2008

Page 32 of 40

Current Limiting Circuit

1. Peripheral circuit of CLM

+, CLM− terminal

VCC

Collector

CVCC

VOUT

CLM+

Emitter

GND

M51995A

RNF1

RNF2

CNF

RCLM

CFIN

Input

smoothing

capacitor

Figure 29 Peripheral Circuit Diagram of CLM

+ Terminal

VCC

Collector

CVCC

VOUT

CLM

−

Emitter

GND

M51995A

RNF1

RNF2

CNF

RCLM

CFIN

Input

smoothing

capacitor

Figure 30 Peripheral Circuit Diagram of CLM

− Terminal

Figure 29 and 30 show the example circuit diagrams around the CLM

+ and CLM− terminal. It is required to

connect the low pass filter, as the main current or drain current contains the spike current especially during the turn-

on duration of MOS FET.

1,000 pF to 22,000 pF is recommended for CNF and the RNF1 and RNF2 have the functions both to adjust the “current-

detecting-sensitivity” and to consist the low pass filter.

To design the RNF1 and RNF2, it is required to consider the influence of CLM terminal source current (IINCLM+ or

INFCLM−), which value is in the range of 90 to 270 µA.

In order to be not influenced from these resistor paralleled value of RNF1 and RNF2, (RNF1/RNF2) is recommended to

be less than 100

Ω.

The RCLM should be the non-inductive resistor.

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