HIGH WITHSTAND-VOLTAGE VOLTAGE REGULATOR WITH RESET FUNCTION
S-87x Series
Rev.7.2_00
Transient Characteristics
An undershoot or an overshoot may occur in the output voltage of the voltage regulator if input voltage or
load current fluctuates transiently. If an undershoot is large, the voltage detector operates to output reset
signal in the B type in which the voltage detector detects the output voltage of the regulator. If an overshoot
is large, the load circuit is adversely affected. Therefore it is important to determine the capacitor value so as
to minimize undershoot and overshoot.
1. Line: Transient characteristics due to input voltage fluctuation
Input voltage fluctuation differs depending on the types of the signal applied: type 1 which is a rectangular
wave between (VOUT+1) V and 10 V, and type 2 which is a rectangular wave from 0 V to 10 V. (Refer to
Figure 26 to 27) The ringing waveforms and parameter dependency of each type are described below.
The measuring circuit is shown in Figure 28 for reference.
10 V
Input voltage
(VOUT+1) V
Overshoot
Output voltage
deviation
Undershoot
Figure 26 Rectangular wave between (VOUT+1) V and 10 V (Type 1)
10 V
0 V
Input voltage
Overshoot
Undershoot
Output voltage
deviation
Remark Rise/fall time (time between 10 % and 90 %) is 1 μs.
Figure 27 Rectangular wave from 0 V to 10 V (Type 2)
Fast amplifier
VIN
VOUT
RO
S-87x Series
VSS
*1
Oscilloscope
10:1 probe
+
CL
−
P.G.
*1. AL electrolytic capacitor
Figure 28 Measuring circuit
33
Seiko Instruments Inc.
SII [ SEIKO INSTRUMENTS INC ]
