16 V INPUT, 75 mA VOLTAGE REGULATOR
S-812C Series
Rev.7.0_01
Operation
1. Basic operation
Figure 17 shows the block diagram of the S-812C Series.
The error amplifier compares the reference voltage (Vref) with feedback voltage (Vfb), which is the output
voltage resistance-divided by feedback resistors (Rs and Rf). It supplies the gate voltage necessary to
maintain the constant output voltage which is not influenced by the input voltage and temperature
change, to the output transistor.
VIN
Current
supply
Vref
Error
amplifier
Reference voltage
circuit
*1
Rf
Vfb
Rs
VOUT
VSS
*1. Parasitic diode
Figure 17
2. Output transistor
In the S-812C Series, a low on-resistance P-channel MOS FET is used as the output transistor.
Be sure that VOUT does not exceed VIN 0.3 V to prevent the voltage regulator from being damaged due
to reverse current flowing from the VOUT pin through a parasitic diode to the VIN pin, when the potential
of VOUT became higher than VIN.
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