S-1172 Datasheet, PDF (15/34 Pages) Seiko Instruments Inc – HIGH RIPPLE-REJECTION LOW DROPOUT HIGH OUTPUT CURRENT CMOS VOLTAGE REGULATOR

Rev.1.1_00
HIGH RIPPLE-REJECTION LOW DROPOUT HIGH OUTPUT CURRENT CMOS VOLTAGE REGULATOR
S-1172 Series
3. Shutdown pin (ON/OFF pin)
This pin starts and stops the regulator.
When the ON/OFF pin is set to the shutdown level, the entire internal circuit stops operating, and the built-in
P-channel MOS FET output transistor between the VIN and VOUT pin is turned off, in order to reduce the current
consumption significantly. The VOUT pin is set to the V_SS level by the internal dividing resistor of several hundred
kΩ between the VOUT and VSS pin.
Note that the current consumption increases when a voltage of 0.3 V to 1.0 V is applied to the ON/OFF pin.
The ON/OFF pin is configured as shown in Figure 14. Since the ON/OFF pin is neither pulled down nor pulled up
internally, do not use it in the floating state.
When not using the ON/OFF pin, connect it to the VSS pin in the product A type, and connect it to the VIN pin in B
type.
Table 8
Logic Type
A
A
B
B
ON/OFF Pin
“L”: Power on
“H”: Power off
“L”: Power off
“H”: Power on
Internal Circuits
Operate
Stop
Stop
Operate
VOUT Pin Voltage
Set value
V_SS level
V_SS level
Set value
Current Consumption
I_SS1
I_SS2
I_SS2
I_SS1
VIN
ON/OFF
VSS
Figure 14
4. Overcurrent protection circuit
The S-1172 Series has an overcurrent protection circuit having the characteristics shown in (1) Output Voltage vs.
Output Current (When load current is increased) (Ta = 25°C) in “„ Characteristics (Typical Data)”, in order to
protect the output transistor against an excessive output current and short circuiting between the VOUT and VSS
pin. The current (I_SHORT) when the output pin is short-circuited is internally set at approx. 200 mA (Typ.), and the
initial value is restored for the output voltage, if releasing a short circuit once.
Caution This overcurrent protection circuit does not work as for thermal protection. If this IC long keeps
short circuiting inside, pay attention to the conditions of input voltage and load current so that,
under the usage conditions including short circuit, the loss of the IC will not exceed power
dissipation of the package.
Seiko Instruments Inc.
15