HA17431 Hitachi Semiconductor, HA17431 Datasheet - Page 16

• Manufacturer Part Number: HA17431
• Description: Regarding the change of names mentioned in the document/ such as Hitachi Electric and Hitachi XX/ to Renesas Technology Corp.
• Manufacturer: Hitachi Semiconductor

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
a wide cathode current range. A (anode) is used at the minimum potential, such as ground.
Application Hints
No.
1
2
Rev.1, Sep. 2002, page 14 of 24
Application Example
Reference voltage generation circuit
GND
Variable output shunt regulator circuit
GND
Vin
Vin
R
R
R
REF
R
1
2
REF
Iref
A
K
K
A
C
C
L
Vout
GND
L
Vout
GND
Figure 1 Operation Diagram
V
Z
≅ 2.5V
REF
Description
This is the simplest reference voltage circuit. The value
of the resistance R is set so that cathode current I
mA.
Output is fixed at Vout ≅ 2.5 V.
The external capacitor C
prevent oscillation in normal applications.
This is circuit 1 above with variable output provided.
Here,
Since the reference input current Iref = 3.8 µA Typ (V
version: Iref = 2 µA Typ) flows through R
values are chosen to allow the resultant voltage drop to
be ignored.
–
+
V
V
A
CC
EE
Vout ≅ 2.5 V ×
OUT
K
(R
KA
1
L
R
(C
, and Z
+ R
2
L
≥ 3.3 µF) is used to
2
)
KA
is low (0.2 Ω) over
1
, resistance
K
≥ 1