HA17431H Datasheet, PDF (8/15 Pages) Hitachi Semiconductor – Shunt Regulator

HA17431H Series
Application Hints (cont.)
No. Application Example
6
Constant voltage regulator circuit
V_CC
R₁
Q
Vout
R₂
GND
Cf
R₃
GND
7
Discharge type constant current circuit
V_CC
R
Q
GND
2.5 V
R_S
+
I_L
–
8
Induction type constant current circuit
+
V_CC
R
I_L
–
Q
GND
2.5 V
R_S
Description
This is a 3-pin regulator with a discrete configuration, in
which the output voltage
Vout = 2.5 V × ^{(R2 + R3)}
R₃
R₁ is a bias resistance for supplying the HA17431H
cathode current and the output transistor Q base
current.
This circuit supplies a constant current of
I_L ≅
2.5 V
R_S
[A] into the load. Caution is required
since the HA17431H cathode current is also
superimposed on I .
L
The requirement in this circuit is that the cathode
current must be greater than Imin = 0.2 mA. The I_L
setting therefore must be on the order of several mA or
more.
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 HA17431H cathode
current is not superimposed on I , so that I can be kept
L
L
small (0.2 mA or less is possible). The constant current
value is the same as for circuit 7 above:
I_L ≅
2.5 V
R_S
[A]
Rev.0, Sep. 2001, page 8 of 15