S-1142D33A-E6T2U Datasheet, PDF (15/31 Pages) Seiko Instruments Inc – Built-in thermal shutdown circuit

HIGH-WITHSTAND VOLTAGE LOW CURRENT CONSUMPTION LOW DROPOUT CMOS VOLTAGE REGULATOR
Rev.1.1_01
S-1142C/DxxA Series
6. Overshoot of output voltage
Overshoot of output voltage occurs depending on the condition such as the rising speed of input voltage (VIN).
Overshoot voltage is the difference between the maximum value of output voltage generated by the fluctuation of
VIN and the actual output voltage (VOUT(E)) value.
6. 1 At normal operation
As shown in Figure 12, Vgs is the voltage difference between VIN and gate voltage of output driver.
The error amplifier controls Vgs in order to keep the output voltage constant depending on the fluctuation of VIN
and the output load.
V_IN
V_ref
−
+
V_gs
Output driver
Output voltage
Output
capacitance ^{Output load}
Figure 12 Circuit Diagram
6. 2 Occurrence of overshoot
If VIN voltage rises at a fast speed, Vgs may become large when gate voltage of output driver can not follow the
speed of VIN. When Vgs becomes large, the current supplied from output driver is increased transiently. Thereby,
output voltage rises, and then overshoot occurs.
Note that overshoot voltage is greatly affected by the following use conditions or temperature, etc.
• When VIN rises in the range of 2.0 V to VOUT(E).
• When the rising speed of VIN is fast.
• When the output capacitance is small.
• When the output load is small.
Input voltage (V_IN)
Rising speed of V_IN =
ΔV
t
ΔV
V_IN = 2.0 V to V_OUT(E)
Output voltage (V_OUT(E))
V_OUT(E)
V_IN = 2.0 V to V_OUT(E)
Overshoot voltage
Rising time (t)
Figure 13 VIN and Overshoot Voltage
Caution Under the following conditions, overshoot voltage tends to become larger especially.
• When VIN rises from around 98% of VOUT(E).
• When the rising speed of VIN is 200 mV/μs or more.
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