LM2641MTC-ADJ Datasheet, PDF (2/31 Pages) Texas Instruments – LM2641 Dual Adjustable Step-Down Switching Power Supply Controller

LM2641
SNVS040B – JANUARY 2000 – REVISED APRIL 2013
Connection Diagram
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Pin #
1
Name
CSH2
2
FB2
3
COMP2
4
SS2
5
ON/OFF2
6
SD
7
SYNC
8
GND
9
REF
10
2NDFB/FPWM
11
ON/OFF1
12
SS1
13
COMP1
14
FB1
15
CSH1
16
HDRV1
17
SW1
18
CBOOT1
19
LDRV1
20
PGND
Figure 1. 28-Lead TSSOP (PW)
Top View
See Package Number PW0028A
Pin Descriptions⁽¹⁾
Function
The sense point for the positive side of the voltage across the current sense resistor (R13) placed in
series with output #2.
The regulated output voltage appearing at output #2 is sensed using this pin by connecting it to the
center of the output resistive divider (R15 and R16).
An R-C network made up of R11, C10, and C12 is connected to this pin which provides loop
compensation for regulated output #2.
This provides programmable soft-start for the #2 output along with capacitor C15.
This pin turns off only output #2.
The part can be put into “sleep” mode using this pin, where both outputs are off and the internal chip
functions are shut down.
The internal oscillator may be synchronized to an external clock via this pin.
Connect this pin to circuit Signal Ground.
Internal 2.5V reference voltage. This voltage is turned off by the SD pin, but remains on if either or both
ON/OFF pins are pulled low, which turns off the regulated output(s).
A 12V supply can be generated using an auxiliary winding on the 5V output inductor. Feedback to
control this 12V output is brought in through this pin. If the 12V supply is not required, this pin can also
force the chip to operate at fixed frequency at light loads by pulling the pin low (this is the “forced-PWM”
mode of operation). This will prevent the converter from operating in pulse-skipping mode.
This pin turns off only output #1.
This provides programmable soft-start for the #1 output along with capacitor C3.
An R-C network made up of R6, C5, and C7 is connected to this pin which provides loop compensation
for regulated output #1.
The regulated output voltage appearing at output #1 is sensed using this pin by connecting it to the
center of the output resistive divider (R1 and R2).
The sense point for the positive side of the voltage across the current sense resistor (R4) placed in
series with output #1.
The drive for the gate of the high-side switching FET used for output #1.
This is the switching output drive point of the two power FETs which produce output #1.
The bootstrap capacitor (C8) for output #1 is returned to this point.
The drive for the gate of the low-side switching FET (synchronous rectifier) used for output #1.
Connect this pin to circuit Power Ground.
(1) (Refer to Typical Application Circuits)
2
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