HIGH WITHSTAND-VOLTAGE VOLTAGE REGULATOR WITH RESET FUNCTION
S-87x Series
Rev.7.2_00
Operation
1. Reference voltage circuit
The reference voltage circuit operates all the time when the voltage is applied to VIN pin and is not
affected by the VPF signal.
2. Voltage regulator
Figure 18 shows the voltage regulator circuit. The S-87x Series has a Pch MOS transistor as the output
control transistor.
Reverse current may break IC if VOUT potential is higher than VIN, because a parasitic diode is formed
between VIN and VOUT due to the structure of the control transistor. Therefore, keep VOUT lower than
VIN+0.3 V.
The output voltage of the voltage regulator can be selected as follows:
2.5 V to 5.8 V±2.4 % (0.1 V step)
VIN
VREF
M1
−
*1
+
VOUT
R1
R2
*1. Parasitic diode
Figure 18 Voltage regulator circuit
Caution For an application with a load current of less than 1 μA, the leakage current of the control
transistor M1 increases the output voltage.
3. Short-circuit protection circuit
The S-87x Series has a built-in short-circuit protection circuit to protect the element from break caused by
a large current in case of a short circuit. The output short current is internally limited to approx. 70 mA.
Short-circuit protection circuit has three kinds characteristics according to input voltage (VIN) as shown in
Figure 19 to 21.
At 5 V Output:
(a) VIN/VOUT≥2.0
(b) 1.5≤VIN/VOUT<2.0
(c) VIN/VOUT<1.5
VOUT
[V]
VOUT
[V]
VOUT
[V]
IOUT
[mA]
IOUT
[mA]
IOUT
[mA]
IOS Imax
Figure 19
IOS
IOS
Figure 21
Figure 20
28
Seiko Instruments Inc.
SII [ SEIKO INSTRUMENTS INC ]
