S-812C Seiko Instruments Inc, S-812C Datasheet - Page 7

• Manufacturer Part Number: S-812C
• Description: HIGH OPERATING VOLTAGE CMOS VOLTAGE REGULATOR
• Manufacturer: Seiko Instruments Inc

Rev.1.0
„ Description of Operation
1. Basic operation
2. Output transistor
5. Dropout voltage (Vdrop)
6. Temperature coefficient of output voltage [ V
Temperature change ratio for output voltage [mV/°C] is calculated by using the following equation.
Temperatures change ratio for output voltage
Figure 9 shows the block diagram of the S-812C
series.
The error amplifier compares a reference voltage
V
feedback resistors Rs and Rf, and supplies the gate
voltage to the output transistor, necessary to ensure
certain output voltage independent from change of
input voltage and temperature.
The S-812C Series uses a Pch MOS transistor as the output transistor.
The voltage at VOUT must not exceed VIN+0.3V. When the VOUT voltage becomes higher than that of VIN,
reverse current flows and may break the regulator since a parasitic diode between VOUT and VIN exists
inevitably.
This parameter indicates the difference between the input voltage (V
voltage falls to 98 % of V
Vdrop = V
The output voltage lies in the shaded area in the whole operating temperature shown in figure 8 when the
temperature coefficient of the output voltage is 100 ppm/ C.
ref
V
Ta
OUT
with a part of the output voltage divided by the
mV/ C
IN
1-[V
Specified output voltage
OUT
V
V
OUT
V
[V]
OUT
(E) × 0.98]
OUT
(E)
(S) V
Figure 8 Example for the S-812C30A
OUT
-40
(E) by gradually decreasing the input voltage (V
HIGH OPERATING VOLTAGE CMOS VOLTAGE REGULATOR
Ta V
V
OUT
Output voltage temperature coefficient
OUT
25
Seiko Instruments Inc.
ppm/ C
OUT
/( Ta V
85
1000
Current
source
VSS
VIN
+0.30mV/ C
-0.30mV/ C
OUT
V
output voltage at 25 C.
Vref
OUT
Reference
voltage
)]
Ta [ C]
(E) is a measured value of
Figure 9 Block Diagram
Error amplifier
IN
1) and the output voltage when output
IN
).
Rf
Rs
S-812C Series
* : Parasitic diode
*
VOUT
7