HA17431H Datasheet, PDF (6/15 Pages) Hitachi Semiconductor – Shunt Regulator

HA17431H Series
Application Examples
As shown in figure 1, this IC operates as an inverting amplifier, with the REF pin as input pin. The open-
loop voltage gain is given by the reciprocal of “reference voltage deviation by cathode voltage change” in
the electrical specifications, and is approximately 50 to 60 dB. The REF pin has a high input impedance,
with an input current Iref of 0.6 µA Typ. The output impedance of the output pin K (cathode) is defined as
dynamic impedance Z_KA, and Z_KA is low (0.2 Ω) over a wide cathode current range. A (anode) is used at the
minimum potential, such as ground.
K
REF _– V_{CC OUT}
V_Z ≅ 2.5V
+ _VEE
A
Figure 1 Operation Diagram
Application Hints
No. Application Example
1
Reference voltage generation circuit
Vin
GND
R
K
REF A
Vout
C_L
GND
2
Variable output shunt regulator circuit
Vin
GND
R
R₁
R₂
Iref
K
REF
A
Vout
C_L
GND
Description
This is the simplest reference voltage circuit. The value
of the resistance R is set so that cathode current I_K ≥
0.2 mA.
Output is fixed at Vout ≅ 2.5 V.
The external capacitor C_L (C_L ≥ 3.3 µF) is used to
prevent oscillation in normal applications.
This is circuit 1 above with variable output provided.
Here, Vout ≅ 2.5 V × ^{(R1 + R2)}
R₂
Since the reference input current Iref = 0.6 µA Typ
flows through R₁, resistance values are chosen to allow
the resultant voltage drop to be ignored.
Rev.0, Sep. 2001, page 6 of 15