S-87X_1 Datasheet, PDF (28/53 Pages) Seiko Instruments Inc – HIGH WITHSTAND-VOLTAGE VOLTAGE REGULATOR WITH RESET FUNCTION

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 V_OUT potential is higher than V_IN, because a parasitic diode is formed
between V_IN and V_OUT due to the structure of the control transistor. Therefore, keep V_OUT lower than
V_IN+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)
V_IN
V_REF
−
+
M1
*1
V_OUT
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 (V_IN) as shown in
Figure 19 to 21.
At 5 V Output:
(a) V_IN/V_OUT≥2.0
V_OUT
[V]
(b) 1.5≤V_IN/V_OUT<2.0
V_OUT
[V]
(c) V_IN/V_OUT<1.5
V_OUT
[V]
I_OS I_max
Figure 19
I_OUT
[mA]
I_OS
Figure 20
I_OUT
[mA]
I_OS
Figure 21
I_OUT
[mA]
28
Seiko Instruments Inc.