MB39A103 Datasheet, PDF (15/33 Pages) List of Unclassifed Manufacturers – 4-Channel DC/DC Converter IC with Support for Low Voltage

MB39A103
■ SETTING THE SOFT-START TIME
To prevent rush currents when the IC is turned on, you can set a soft-start by connecting soft-start capacitors
(CS1 to CS4) to the CS1 terminal (pin 30) to the CS4 terminal (pin 16), respectively.
Setting each CTLx from “H” to “L” switches to charge the external soft-start capacitors (CS1 to CS4) connected
to the CS1 terminal (pin 30) to CS4 terminal (pin 16) at 10 µA.
The error amplifier output (FB1 to FB4) is determined by comparison between the lower one of the potentials
at two non-inverted input terminals (1.24 V, CS terminal voltages) and the inverted input terminal voltage (−INE1
to −INE4).
The FB terminal voltage during the soft-start period (CS terminal voltage < 1.24 V) is therefore determined by
comparison between the −INE terminal and CS terminal voltages. The DC/DC converter output voltage rises in
proportion to the CS terminal voltage as the soft-start capacitor connected to the CS terminal is charged.
The soft-start time is obtained from the following formula:
Soft-start time: ts (time to output 100%)
ts (s) =: 0.124 × CSX (µF)
• Soft-Start Circuit
VO
VREF
10 µA
R1
−INEx
R2
CH ON/OFF signal _CTLx
L: ON, H: OFF
CSx
CSx
FBx
L priority
Error Amp
−
+
+
1.24 V
UVLO
x: Each channel No.
15