S-812C_1 Datasheet, PDF (17/52 Pages) Seiko Instruments Inc – HIGH OPERATING VOLTAGE CMOS VOLTAGE REGULATOR

Rev.4.0_00
HIGH OPERATING VOLTAGE CMOS VOLTAGE REGULATOR
S-812C Series
3. Power-off function (ON/OFF pin)
This function starts and stops the regulator.
When the ON/OFF pin is set to power-off 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 MΩ between the VOUT and VSS pin.
The ON/OFF pin is configured as shown in Figure 17 Since the ON/OFF pin is neither pulled down nor
pulled up internally, do not use it in the floating state. Note that if applying the voltage of V_IN + 0.3 V or
more, the current flows to V_IN via a parasitic diode in the IC.
When not using the power-off pin in the product with the power-off function, connect the ON/OFF pin to
the VIN pin (in positive logic), or to the VSS pin (in negative logic).
The output voltage may increase by stopping regulation when a lower current (less than 100 µA) is
applied.
If the output voltage increased during power-off, pull the VOUT pin down to the VSS pin and set the
ON/OFF pin to the power-down level.
Table 11
Logic Type
B
B
ON/OFF Pin
“L”: Power off
“H”: Power on
Internal Circuits
Stop
Operation
VOUT Pin Voltage
V_SS level
Set value
Current Consumption
I_SS2
I_SS1
VIN
ON/OFF
VSS
Figure 17
4. Short-circuit protection circuit
In the S-812C Series, users are able to select whether to set the short circuit protection, which protects
the output capacitor from short-circuiting the VOUT and VSS pin.
The short circuit protection circuit controls the output current against voltage V_OUT, as seen in “„
Characteristics (Typical Data) 1”, and limits the output current at approx. 40 mA even if the VOUT and
VSS pins are short-circuited.
However, this short circuit protection circuit does not work as for thermal protection. Pay attention to the
conditions of input voltage and load current so that, under the usage condition including short circuit, the
loss of the IC will not exceed power dissipation of the package.
Even if pins are not short-circuited, this protection circuit works to limit the current to the specified value,
in order to protect the output capacitor, when the output current and the potential difference between
input and output voltages increase.
In the product without the short circuit protection circuit, the S-812C Series allows the relatively larger
current because this protection circuit is detached.
Seiko Instruments Inc.
17