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HIGH RIPPLE-REJECTION LOW DROPOUT SOFT-START FUNCTION CMOS VOLTAGE REGULATOR
S-1137 Series
Rev.2.0_01
Seiko Instruments Inc.
22
Precautions
Wiring patterns for the VIN, VOUT and GND pins should be designed so that the impedance is low. When mounting
an output capacitor between the VOUT and VSS pins (CL), the capacitor for stabilizing the input between the VIN and
VSS pins (CIN), and the capacitor for soft-start between the SSC and VSS pins, the distance from the capacitors to
these pins should be as short as possible.
Note that the output voltage may increase when a series regulator is used at low load current (1.0 mA or less).
Note that the output voltage may increase due to the leakage current from a driver 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 this IC. However, be sure to perform sufficient evaluation under the actual usage
conditions for selection, including evaluation of temperature characteristics. See “(8) Example of Equivalent Series
Resistance vs. Output Current Characteristics (Ta = 25
°C)” in “
Reference Data” for the equivalent series
resistance (RESR) of the output capacitor.
Input capacitor (CIN) :
1.0
μF or more
Output capacitor (CL) :
1.0
μF or more
Capacitor for soft-start (CSS) : 0.22 nF to 22 nF
The voltage regulator may oscillate when the impedance of the power supply is high and the input capacitor is small or
an input capacitor is not connected.
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.
Although this IC has a soft-start circuit, small overshoot may be included in the output voltage by the lower-valued
capacitor for soft-start (CSS). Evaluate sufficiently with actual devices.
The application conditions for the input voltage, output voltage, and 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 10 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.