Datasheet

V
OUT
C
EXT
R1
+
+
0.7 V
+
U3
+
+
From CSx
Amplifier
+
Ramp1
U7 Comparator
PWM
Logic
FBx
TRKx
Error Amplifier
COMPx
R
BIAS
12 µA
6 µA
V
REF
UDG−06031
0.7
VOUT
FBx
0
0
t0 t1
2.4
1.4
PGOOD
TRKx
VPRE-BIAS
6 µA
12 µA
FBx
VOUT
t2 t3
UDG-12121
TPS40140
SLUS660H –SEPTEMBER 2005–REVISED JUNE 2013 www.ti.com
Figure 5-2. Soft-Start with Pre-Biased Output Waveforms
Figure 5-3. Implementation of Pre-Biased Output
DESIGN HINT
If the pre-biased is greater than the regulation voltage, the controller does not start. This is a
condition of an overvoltage being applied before the controller starts PWM switching.
5.6 TRACK FUNCTION IN CONFIGURING A SLAVE CHANNEL
The TRKx pin is internally clamped to 2.4 V. To configure a channel as a slave, the TRKx pin is pulled up
externally to 5 V. This configures the output of the error amplifier, COMPx, for that channel to be a high
impedance, allowing the master COMP signal to control the slave channel.
18 APPLICATION INFORMATION Copyright © 2005–2013, Texas Instruments Incorporated
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