HA17431 Hitachi Semiconductor, HA17431 Datasheet - Page 18

• 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 Hints (cont.)
No.
6
7
8
Rev.1, Sep. 2002, page 16 of 24
Application Example
Constant voltage regulator circuit
GND
Discharge type constant current circuit
V
GND
Induction type constant current circuit
V
GND
V
CC
CC
CC
R
1
Cf
R
R
2.5 V
2.5 V
R
R
Q
+
–
2
3
R
R
+
–
Q
Q
S
S
Vout
GND
I
I
L
L
Description
This is a 3-pin regulator with a discrete configuration, in
which the output voltage
Vout = 2.5 V ×
R
cathode current and the output transistor Q base
current.
This circuit supplies a constant current of
I
since the HA17431 cathode current is also
superimposed on I
The requirement in this circuit is that the cathode
current must be greater than Imin = 1 mA. The I
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
(1 mA or less is possible). The constant current value
is the same as for circuit 7 above:
I
L
L
1
≅
≅
is a bias resistance for supplying the HA17431
2.5 V
2.5 V
R
R
S
S
[A] into the load. Caution is required
[A]
(R
2
R
L
+ R
.
3
3
)
L
, so that I
L
can be kept small
L