S1212B Datasheet, PDF (15/58 Pages) Seiko Instruments Inc – HIGH-WITHSTAND VOLTAGE LOW CURRENT CONSUMPTION LOW DROPOUT CMOS VOLTAGE REGULATOR

HIGH-WITHSTAND VOLTAGE LOW CURRENT CONSUMPTION LOW DROPOUT CMOS VOLTAGE REGULATOR
Rev.3.0_00
S-1212B/D Series
3. ON / OFF pin
The ON / OFF pin controls the internal circuit and the output transistor in order to start and stop the regulator. When
the ON / OFF pin is set to OFF, the internal circuit stops operating and the output transistor between the VIN pin and
the VOUT pin is turned off, reducing current consumption significantly.
The internal equivalent circuit related to the ON / OFF pin is configured as shown in Figure 16. Since the ON / OFF
pin is neither pulled down nor pulled up, do not use it in the floating status. When not using the ON / OFF pin, connect
it to the VIN pin. Note that the current consumption increases when a voltage of V_SL max.^*1 to V_IN − 0.3 V is applied to
the ON / OFF pin.
Table 14
Product Type
B/D
B/D
ON / OFF Pin
"H": ON
"L": OFF
Internal Circuit
Operate
Stop
VOUT Pin Voltage
Constant value^*2
Pulled down to V_SS^*3
Current Consumption
I_SS1
I_SS2
*1. Refer to Table 13 in " Electrical Characteristics".
*2. The constant value is output due to the regulating based on the set output voltage value.
*3. The VOUT pin voltage is pulled down to V_SS due to the discharge shunt circuit (R_LOW = 70 kΩ typ.), the
feedback resistors (R_s and R_f) and a load.
VIN
ON / OFF
VSS
Figure 16
4. Overcurrent protection circuit
The S-1212B/D Series has a built-in overcurrent protection circuit to limit the overcurrent of the output transistor.
When the VOUT pin is shorted with the VSS pin, that is, at the time of the output short-circuit, the output current is
limited to 120 mA typ. due to the overcurrent protection circuit operation. The S-1212B/D Series restarts regulating
when the output transistor is released from the overcurrent status.
Caution 1. This overcurrent protection circuit does not work as for thermal protection. For example, when
the output transistor keeps the overcurrent status long at the time of output short-circuit or
due to other reasons, pay attention to the conditions of the input voltage and the load current
so as not to exceed the power dissipation.
2. Note that any interference may be caused in the output voltage start-up when a load heavier
than
V_OUT(S)
100 mA
is connected.
15