HA17431_15 Datasheet, PDF (14/21 Pages) Renesas Technology Corp – Shunt Regulator

HA17431 Series
Application Hints (cont.)
No.
Application Example
6 Constant voltage regulator circuit
V_CC
R₁
Q
GND
R₂
Cf
R₃
Vout
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 HA17431 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 HA17431 cathode current is also superimposed on I_L.
The requirement in this circuit is that the cathode current must be
greater than Imin = 1 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 HA17431 cathode current is not superimposed on I_L,
so that I_L can be kept small (1 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]
R03DS0086EJ0400 Rev.4.00
Jan 10, 2014
Page 14 of 20