HA17431FP datasheet(14/20 Pages) RENESAS

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HA17431 Series

REJ03D0678-0300 Rev.3.00 Apr 03, 2007

Page 14 of 19

Application Hints

(cont.)

No.

Application Example

Description

Constant voltage regulator circuit

VCC

Vout

GND

This is a 3-pin regulator with a discrete configuration, in which the

output voltage

Vout = 2.5 V

(R2 + R3)

R1 is a bias resistance for supplying the HA17431 cathode current

and the output transistor Q base current.

Discharge type constant current circuit

GND

VCC

2.5 V

–

This circuit supplies a constant current of

IL ≅

[A] into the load. Caution is required

2.5 V

since the HA17431 cathode current is also superimposed on IL.

The requirement in this circuit is that the cathode current must be

greater than Imin = 1 mA. The IL setting therefore must be on the

order of several mA or more.

Induction type constant current circuit

GND

VCC

2.5 V

–

In this circuit, the load is connected on the collector side of

transistor Q in circuit 7 above. In this case, the load floats from

GND, but the HA17431 cathode current is not superimposed on IL,

so that IL can be kept small (1 mA or less is possible). The constant

current value is the same as for circuit 7 above:

IL ≅

[A]

2.5 V

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