S1172 Datasheet, PDF (17/35 Pages) Seiko Instruments Inc – HIGH RIPPLE-REJECTION LOW DROPOUT

Rev.2.2_01
HIGH RIPPLE-REJECTION LOW DROPOUT HIGH OUTPUT CURRENT CMOS VOLTAGE REGULATOR
S-1172 Series
 Precautions
• Wiring patterns for the VIN pin, the VOUT pin and GND should be designed so that the impedance is low. When
mounting an output capacitor between the VOUT pin and the VSS pin (C_L) and a capacitor for stabilizing the input
between the VIN pin and the VSS pin (C_IN), the distance from the capacitors to these pins should be as short as
possible.
• Note that generally the output voltage may increase when a series regulator is used at low load current (1.0 mA or
less).
• Note that generally the output voltage may increase due to the leakage current from an output driver when a series
regulator is used at high temperature.
• Note that the output voltage may increase due to the leakage current from an output driver even if the ON/OFF pin is
at OFF level when a series regulator is used at high temperature.
• Generally a series regulator may cause oscillation, depending on the selection of external parts. The following
conditions are recommended for the S-1172 Series. However, be sure to perform sufficient evaluation under the
actual usage conditions for selection, including evaluation of temperature characteristics. Refer to “5. Example of
equivalent series resistance vs. Output current characteristics (Ta = +25°C)” in “ Reference Data” for the
equivalent series resistance (R_ESR) of the output capacitor.
Input capacitor (C_IN):
Output capacitor (C_L):
4.7 μF or more
4.7 μF or more
• The voltage regulator may oscillate when the impedance of the power supply is high and the input capacitance is
small or an input capacitor is not connected. Note that the voltage regulator may oscillate when the value of the
output capacitor is greater than that of the input capacitor.
• Ringing may occur when these three conditions below are satisfied. Before selecting an input capacitor, be sure to
evaluate sufficiently under the actual usage conditions, including the temperature characteristics.
The power supply inductance is high.
The load current is 100 mA or more.
The difference between the input voltage and the output voltage is close to the value of dropout voltage.
• If the output capacitance is small, power supply’s fluctuation and the characteristics of load fluctuation become worse.
Sufficiently evaluate the output voltage’s fluctuation with the actual device.
• Overshoot may occur in the output voltage momentarily if the voltage is rapidly raised at power-on or when the power
supply fluctuates. Sufficiently evaluate the output voltage at power-on with the actual device.
• The application conditions for the input voltage, the output voltage, and the load current should not exceed the
package power dissipation.
• Do not apply an electrostatic discharge to this IC that exceeds the performance ratings of the built-in electrostatic
protection circuit.
• In determining the output current, attention should be paid to the output current value specified in Table 7 in
“ Electrical Characteristics” and footnote *5 of the table.
• SII claims no responsibility for any disputes arising out of or in connection with any infringement by products including
this IC of patents owned by a third party.
Seiko Instruments Inc.
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