S-1137 Datasheet, PDF (15/47 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
 Standard Circuit
Input
C_IN^*1
VIN
VOUT
ON / OFF SSC
VSS
Output
C_SS^*3
C_L^*2
Single GND
GND
*1. CIN is a capacitor for stabilizing the input.
*2. A ceramic capacitor of 1.0 μF or more can be used as CL.
*3. A ceramic capacitor of 0.22 nF to 22 nF can be used for CSS.
Figure 14
Caution The above connection diagram and constant will not guarantee successful operation. Perform
thorough evaluation using the actual application to set the constant.
 Condition of Application
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
Caution Generally a series regulator may cause oscillation, depending on the selection of external parts.
Confirm that no oscillation occurs in the application for which the above capacitors are used.
 Selection of Input and Output Capacitors (CIN, CL)
The S-1137 Series requires an output capacitor between the VOUT and VSS pins for phase compensation. Operation is
stabilized by a ceramic capacitor with an output capacitance of 1.0 μF or more over the entire temperature range.
When using an OS capacitor, a tantalum capacitor, or an aluminum electrolytic capacitor, the capacitance must be 1.0
μF or more.
The value of the output overshoot or undershoot transient response varies depending on the value of the output
capacitor. The required capacitance of the input capacitor differs depending on the application.
The recommended capacitance for an application is CIN ≥ 1.0 μF, CL ≥ 1.0 μF; however, when selecting the output
capacitor, perform sufficient evaluation including evaluation of temperature characteristics with the actual device.
 Selection of Capacitor for Soft-start (CSS)
The S-1137 Series requires a capacitor for soft-start (CSS) between the SSC and VSS pins. Over the entire temperature
range, the S-1137 Series operates stably with a ceramic capacitor of 0.22 nF or more. According to CSS capacitance, the
rising speed of the output voltage is adjustable. The time that the output voltage rises to 99% is 0.7 ms typ. at
CSS = 1.0 nF. The recommended value for applications is 0.22 nF ≤ CSS ≤ 22 nF, however, define the values by
sufficient evaluation including the temperature characteristics under the usage condition.
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