HA16108FP View Datasheet(PDF) - Hitachi -> Renesas Electronics

Part Name

Description

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HA16108FP

PWM Switching Regulator for High-performance Voltage Mode Control

Hitachi -> Renesas Electronics 

HA16107P/FP, HA16108P/FP

Vref Protection Functions: Overvoltage and Undervoltage

Vref overvoltage and undervoltage conditions are detected by the overvoltage detection circuit and UVL2

circuit. PWM output shuts down when Vref ≥ 8 V. UVL2 detects undervoltage with hysteresis between

approximately 4 V and 5 V. PWM output also shuts down below these voltages. It follows that PWM

output will shut off whenever the Vref pin is shorted to the power supply (VIN) or ground (GND). PWM

output also shuts off when VIN is turned on or off.

The following diagram shows how these protection functions operate when power comes on and goes off

(Vref < 6.45 V), and when a high external voltage is applied to the Vref pin (Vref > 6.45 V).

PWM

OUT

PWM output shut-

down region

Power-off,

or shorted

to ground

Power-up

PWM output

operating region

Shorted to

power supply

PWM output

shut-down region

Vref

0

4 V 5 V 6.45 V 8 V 10 V

UVL2

Vref

OVP

1. Current-Limiter Circuit

The current limiter pin (CL) is connected to the emitter of an npn transistor, as shown in the block

diagram. The threshold voltage is 240 mV typ. The switching speed of this circuit is approximately

100 ns from detection of overcurrent to shut-down of PWM output. Switching speed increases with the

strength of the signal input to the CL pin.

Instead of simple pulse-by-pulse current limiting, in these ICs the current limiting circuit is linked to the

timer-and-latch or ON/OFF timer circuit, and also detects the degree of overcurrent. The overcurrent

value is determined from the point at which current limiting is triggered in the ON-duty cycle. With a

large overcurrent (causing current limiting to operate even at a small ON-duty), the IC automatically

shortens the timer time.

10

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