TPS40180 Datasheet, PDF (17/52 Pages) Texas Instruments – SINGLE PHASE STACKABLE CONTROLLER

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TPS40180
SLVS753B – FEBRUARY 2007 – REVISED NOVEMBER 2007
t1 =
C_SS
I_SS1
æ
´ç
è
V_PREBIAS ´ R_BAIS
R1+ R_BIAS
ö
÷
ø
(3)
t2
=
C_SS
I_SS2
æ
´ çç V_REF
è
-
æ
ç
è
V_PREBIAS ´ R_BIAS
R1+ R_BIAS
öö
÷
ø
÷÷ø
(4)
T_SS = t1+ t2
(5)
where
•
•
•
•
•
•
t₁ is the time to the first PWM pulse in seconds
t₂ is the time from the first PWM pulse until regulation in seconds
C_(SS) is the SS pin capacitor in µF
I_(SS1) is the SS1 pin charging current in µA, 7.5 µA
I_(SS2)is the SS2 pin charging current in µA,15 µA
T_SS is the total soft-start time
Tracking
The TPS40180 can function in a tracking mode, where the output tracks some other voltage. To do this, a
voltage divider is connected from the voltage to be tracked to GND, with the tap of the divider connected to the
SS pin of the TPS40180. See Figure 24. The capacitors C1 and C2 are required for two purposes. First they
provide a means for timing of overcurrent restart attempts. Second, they provide for matching output voltage
ramp up rate of the TPS40180 to the controlling external supply.
R5
R4
C3
TPS40180
R3
2 DIFFO
R6
C4
C5
1 FB
24 COMP
+
V_EXT
-
R1 C1
I_SS
7
SS
R2
C2
Figure 24. Tracking Setup
UDG-07027
Copyright © 2007, Texas Instruments Incorporated
Product Folder Link(s): TPS40180
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