HA16114 データシートの表示（PDF） - Renesas Electronics

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HA16114

Switching Regulator for Chopper Type DC/DC Converter

Renesas Electronics 

HA16116FP/FPJ, HA16121FP/FPJ

7.2 Adjusting UVL Voltage (when intermittent operation is not used)

The UVL voltage setting in this IC series can be adjusted externally as shown below.

Using the relationships shown in the figure, the UVL voltage in relation to VIN can be adjusted by changing

the relative values of VTH and VTL.

When the IC is operating, transistor Q4 is off, so VON = 3VBE ≈ 2.1 V. Accordingly, by connecting resistors

RC and RD, the voltage at which UVL is cancelled is as follows.

VIN = 2.1 V ×

RC + RD

RD

This VIN is simply the supply voltage at which the UVL stops functioning, so in this state Vref is still below

2.5 V. In order to restore Vref to 2.5 V, a VIN of approximately 4.3 V should be applied.

With this IC series, VON/OFF makes use of the VBE of internal transistors, so when designing a power supply

system it should be noted that VON has a temperature dependency of around –6 mV/°C.

VIN

P.VIN

S.VIN

TIM

RC

(open)

To output

stage

To latch

To other circuitry

ON/OFF

50 kΩ

RD

Q1

Vref

generation

circuit

Q2

Q3

Q4

Vref output

GND

On/off hysteresis circuit

3

2

Vref

1

VOFF

1.4 V

2.5 V

VON

2.1 V

VIN ≥ 4.5 V

0

012 345

VON/OFF

Figure 7.2 Adjusting UVL Voltage

Rev.2.0, Sep.18.2003, page 19 of 33

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