S-19253E12H-U5T1U Datasheet, PDF (16/30 Pages) Seiko Instruments Inc – CMOS VOLTAGE REGULATOR WITH SOFT-START FUNCTION

FOR AUTOMOTIVE 105°C OPERATION LOW DROPOUT HIGH OUTPUT CURRENT CMOS VOLTAGE REGULATOR WITH SOFT-START FUNCTION
S-19253xxxH Series
Rev.1.0_00
8. Soft-start function
The S-19253xxxH Series has the built-in soft-start circuit to suppress the inrush current and overshoot of the output
voltage generated at power-on or at the time when the ON / OFF pin is set to ON. The soft-start time (t_SS) is the
time period from when the output voltage rises slowly immediately after power-on or when the ON / OFF pin is set
to ON until when the output voltage rises to 99%.
Input voltage
(V_IN, V_{ON / OFF})
V_IN
SSC pin voltage
(V_SSC)
Output voltage
(V_OUT(E))
V_OUT(E) × 0.99
Soft-start time (t_SS)
Figure 13
t [ms]
8. 1 Soft-start time
t_SS can be adjusted by the external capacitor (C_SS) connected between the SSC pin and the VSS pin, and is
calculated by using the following calculation.
t_SS [ms] = Soft-start coefficient^*1 [ms / nF] × C_SS [nF] + t_D0^*2 [ms]
*1. It is determined by charging the built-in constant current (approx. 2.1 μA) to C_SS.
*2. The delay time of internal capacitance.
When the C_SS value is sufficiently large, the t_D0 value can be disregarded. When the ON / OFF pin is set to OFF,
the electrical charge charged in C_SS is discharged by the transistor of the discharge shunt circuit.
Table 9 Soft-start Coefficient [ms / nF]
Operation Temperature
Min.
Typ.
T_j = +105°C
T_j = +25°C
T_j = −40°C
0.398
0.436
0.467
0.539
0.574
0.604
Max.
0.690
0.704
0.717
Table 10 Delay Time of Internal Capacitnace (t_D0)
Operation Temperature
Min.
Typ.
Max.
T_j = −40°C to +105°C
0.032 ms
0.047 ms
0.108 ms
Caution
The above calculation will not guarantee successful operation. Perform thorough evaluation using
the actual application including the temperature characteristics under the actual usage conditions
to determine C_SS capacitance. Refer to " Condition of Application" and " Characteristics (Typical
Data)" for details.
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