Datasheet

C
OUT
V
IN
(4.5Vto15V)
C
IN
C
CS3
C
CS1
R
DROOP
V
OUT
(0.7Vto3.5V)
R
FB1
R
FB2
R
FB3
C
FB1
R
RT
C
SS
R
ILIM2
C
BP5
R
CS1
R
CS3
21
23
VIN
PWM3
19
L2
L1
TI
Synchronous
Buck
Driver
PWM1
3
6 1
CS3
CS1ILIM
17
RT
7
SS
15
GND
9
10
COMP
16
DROOP
4
2
CS4
CS2
FB
12
13
VOUT
GNDS
11 DIFFO
8 REF
22 BP5
5
CSCNPGOOD
24
EN/SYNC
PWM2
20
PWM4
18
14
TI
Synchronous
Buck
Driver
BP5
TPS40090PW
R
ILIM1
C
REF
TPS40090
TPS40091
SLUS578B –OCTOBER 2003– REVISED MAY 2006 www.ti.com
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
DESCRIPTION CONTINUED
The TPS4009x uses fixed frequency, peak current mode control with forced phase current balancing. When
compared to voltage mode control, current mode results in a simplified feedback network and reduced input line
sensitivity. Phase current is sensed by using either current sense resistors installed in series with output
inductors or, for improved efficiency, by using the DCR (direct current resistance) of the filter inductors. The latter
method involves generation of a current proportional signal with an R-C circuit (shown in Figure 10).
The R-C values are selected by matching the time constants of the R-C circuit and the inductor; R-C = L/DCR.
With either current sense method, the current signal is amplified and superimposed on the amplified voltage error
signal to provide current mode PWM control.
An output voltage droop can be programmed to improve the transient window and reduce size of the output filter.
Other features include a single voltage operation, a true differential sense amplifier, a programmable current
limit, soft-start and a power good indicator.
SIMPLIFIED TWO-PHASE APPLICATION DIAGRAM
2 Submit Documentation Feedback Copyright © 2003–2006, Texas Instruments Incorporated
Product Folder Link(s): TPS40090 TPS40091