S-13R1 Datasheet, PDF (22/49 Pages) Seiko Instruments Inc – REVERSE CURRENT PROTECTION CMOS VOLTAGE REGULATOR

REVERSE CURRENT PROTECTION CMOS VOLTAGE REGULATOR
S-13R1 Series
Rev.1.2_01
8. Reverse current protection function
8. 1 Detection and release of reverse current protection mode
The reverse current protection function compares values of the VIN pin voltage (VIN) and the VOUT pin voltage
(VOUT), and prevents the current from flowing to the VIN pin and the VSS pin from the VOUT pin. Also, in the
S-13R1 Series A / B type, the current flows from the VOUT pin to the VSS pin due to a discharge shunt circuit.
During the reverse current protection mode, the connection direction of parasitic diode of the output transistor is
switched by the reverse current protection circuit, and the feedback resistors (Rs, Rf) and the VSS pin are
disconnected.
The reverse current is prevented by switching the reverse current protection mode before VIN becomes lower than
VOUT.
As shown in Figure 24, in the case of VIN − VOUT > VREVD, the S-13R1 Series is in normal operation mode. The
reverse current protection mode is detected when VIN − VOUT ≤ VREVD.
In order to insure the stable operation, there is also a hysteresis for detection and release of the reverse current
protection mode. Therefore, the reverse current protection mode is released when VIN − VOUT ≥ VREVR.
The reverse current detection circuit operates at 0 V ≤ VIN ≤ 5.5 V and VOUT ≥ 0.5 V.
Current flow
VIN
Current
supply
Error
amplifier
−
+
VIN
Current
supply
Reverse current
detection circuit
R_f
VOUT
Error
amplifier
−
+
Reverse current
detection circuit
R_f
Reference voltage
R_s
Reference voltage
circuit
R_s
circuit
VSS
VSS
VOUT
Reverse
current
(I_REV)
Current
flow
Figure 22 Normal Operation Mode
Figure 23 Reverse Current Protection Mode
V_IN
V_OUT + V_REVR
V_OUT + V_REVD
V_OUT
Reverse current protection
mode detection voltage (V_REVD)
Reverse current protection
mode release voltage (V_REVR)
Normal operation mode
Reverse current protection mode
Figure 24
Normal operation mode
22