S-8363B-I6T1U2 Datasheet, PDF (11/50 Pages) Seiko Instruments Inc – PWM/PFM SWITCHABLE SWITCHING REGULATOR

STEP-UP, SUPER-SMALL PACKAGE, 1.2 MHz PWM/PFM SWITCHABLE SWITCHING REGULATOR
Rev.2.0_01
S-8363 Series
3. Soft-start function
The S-8363 Series has the built-in soft-start circuit. When power-on (connecting ON / OFF to VIN) or after
start-up at ON / OFF = “H”, the output voltage (VOUT) gradually rises, suppressing rush current and overshoot of
the output voltage. In the S-8363 Series, the soft-start time (tss) is from start-up to the time to reach 90% of the
VOUT output voltage setting value (VOUT(S)). A reference voltage adjustment method is adopted as the soft-start
method, the reference voltage gradually rises from 0 V simultaneously with start of the soft-start. The soft-start
circuit has two operation modes which is selected according to the VOUT voltage at start-up.
3.1 VOUT voltage at start-up > STU release voltage
The soft-start starts when the reference voltage gradually rises after ON / OFF = “H”.
Input voltage
(V_IN)
0V
Soft-start time (t_ss)
STU release
Output voltage
(V_OUT)
0V
Reference voltage
from
error amplifier ^{0 V}
ON/OFF
voltage _{0 V}
Soft-start period
V_OUT × 0.90
Figure 10
Time [s]
11