HA17431_15 Datasheet, PDF (12/21 Pages) Renesas Technology Corp – Shunt Regulator

HA17431 Series
Application Examples
As shown in the figure on the right, 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
3.8 μA Typ (V version: Iref = 2 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
Description
This is the simplest reference voltage circuit. The value of the
resistance R is set so that cathode current I_K ≥ 1 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.
2 Variable output shunt regulator circuit
Vin
GND
R
R₁
R₂
Iref
K
REF
A
Vout
C_L
GND
This is circuit 1 above with variable output provided.
Here, Vout ≅ 2.5 V × ^{(R1 + R2)}
R₂
Since the reference input current Iref = 3.8 μA Typ (V version: Iref =
2 μA Typ) flows through R₁, resistance values are chosen to allow
the resultant voltage drop to be ignored.
R03DS0086EJ0400 Rev.4.00
Jan 10, 2014
Page 12 of 20