AAT1109-T2 AAT [Advanced Analog Technology, Inc.], AAT1109-T2 Datasheet - Page 5

• Manufacturer Part Number: AAT1109-T2
• Description: ONE-CHANNEL STEP-UP PWM CONTROLLER
• Manufacturer: AAT [Advanced Analog Technology, Inc.]

HOW TO SET THE TIME CONSTANT FOR SOFT-START AND SHORT
CIRCUIT PROTECTION
1. Soft-Start
2. Short Circuit Protection
AAT1109 operates in soft-start mode. The PWM comparator monitors the voltage at soft-start setting
and SCP pin, which varies proportionally to each other. This proportion relation controls the ON duty
of the OUT pin and activates the soft-start operation. In the Soft-start mode, the voltage at SCP pin
(
When the soft-started mode is completed, its setting voltage remains high and the circuit enters the
output short circuit protection wait state while
Soft-Start Time
In response to a sudden drop of the switching regulator output, the device locks the error amplifier, OE
pin, at
approximately 0.84V at this pin. This chain reaction protects the circuit by keeping the SCP pin and
output pin low. Users could reverse this process by restarting the device.
Short Circuit Detection Time
t
t
V
s
SCP
( )
SCP
sec
( )
sec
) is input to the PWM comparator, so that the ON duty of the OUT pin is determined by the
V
~
OS
0
+
~
.
84
, and starts feeding currents into the capacitor at SCP pin to achieve in a voltage value of
0
.
×
84
Advanced Analog Technology, Inc.
C
×
SCP
C
SCP
( )
µ
–
F
–
( )
µ
F
Advanced Analog Technology, Inc
台灣類比科技股份有限公司
V
SCP
Page 5 of 18
remains low.
.
–
–
AAT1109
V 1.0
V
SCP
.