S-1137 Datasheet, PDF (19/47 Pages) Seiko Instruments Inc – HIGH RIPPLE-REJECTION LOW DROPOUT SOFT-START FUNCTION CMOS VOLTAGE REGULATOR

HIGH RIPPLE-REJECTION LOW DROPOUT SOFT-START FUNCTION CMOS VOLTAGE REGULATOR
Rev.2.1_01
S-1137 Series
3. ON / OFF pin
This pin starts and stops the regulator.
When the ON / OFF pin is set to OFF level, the entire internal circuit stops operating, and the built-in P-channel MOS
FET output transistor between the VIN and VOUT pins is turned off, reducing current consumption significantly. The
S-1137 Series has a discharge shunt circuit which discharges the capacitor for soft-start (CSS) so that the SSC pin is
forcibly set to the VSS level.
Since the S-1137 Series A / B types have a built-in discharge shunt circuit to discharge the output capacitance, the
VOUT pin is forcibly set to VSS level. In the S-1137 Series C / D types, the VOUT pin is set to VSS level through several
hundred kΩ internal divided resistors between the VOUT and VSS pins.
Note that the current consumption increases when a voltage of 0.3 V to 1.0 V (Ta = 25°C) is applied to the ON / OFF
pin. The ON / OFF pin is configured as shown in Figures 17 and 18. In the S-1137 Series A / C types, the ON / OFF
pin is internally pulled down to the VSS pin in the floating status, so the VOUT pin is set to the VSS level. In the S-1137
Series B / D types, the ON / OFF pin is not internally pulled down, so do not use the pin in the floating status. When not
using the ON / OFF pin in the S-1137 Series B / D types, connect the pin to the VIN pin.
Table 11
Product Type ON / OFF Pin
Internal Circuit
VOUT Pin Voltage
Current Consumption
A/B/C/D
A/B/C/D
“H”: ON
“L”: OFF
Operate
Stop
Set value
VSS level
ISS1^*1
ISS2
*1. IC’s current consumption increases as much as current flows into the pull-down resistor when the ON / OFF
pin is connected to the VIN pin and the S-1137 Series A / C types is operating (Figure 17).
(1) S-1137 Series A / C Type
(2) S-1137 Series B / D Type
VIN
VIN
ON / OFF
VSS
Figure 17
ON / OFF
VSS
Figure 18
19