LM2648 National Semiconductor, LM2648 Datasheet - Page 2

• Manufacturer Part Number: LM2648
• Description: Synchronous Step-Down 3-Channel Switching Regulator Controller
• Manufacturer: National Semiconductor

www.national.com
Connection Diagram
Pin Descriptions
SW1 (Pin 1): Switch-node connection for Channel 1, which
is connected to the source of the top MOSFET of Channel 1.
It serves as the negative supply rail for the top-side gate
drive, HDRV1.
RSNS1 (Pin 2): The negative (-) Kelvin sense for the internal
current limit comparator of Channel 1. Connect this pin to the
low side of the current sense resistor that is placed between
VIN and the drain of the top MOSFET. Always use a sepa-
rate trace to connect this pin.
ILIM1 (Pin 3): Current limit threshold setting for Channel 1. It
sinks a variable current adjusted by RILIM (Pin11), which is
converted to a voltage through a resistor connected from this
pin to the top of the current sense resistor. The voltage
across the resistor is compared with the voltage across the
external current sense resistor to determine if an over-
current condition has occurred on Channel 1.
NC (Pin 4): All NC pins should be connected to SGND.
See NS Package Number MTD56
Order Number LM2648MTD
56-Lead TSSOP (MTD)
TOP VIEW
2
COMP1 (Pin 5): Compensation pin for Channel 1. This is the
output of the internal error amplifier. The compensation net-
work should be connected between this pin and the feed-
back pin, FB1 (PIN 6).
FB1 (Pin 6): Feedback input for channel 1. Connect to Vout
through a voltage divider to set the channel 1 output voltage.
TEST (Pin 7): Connect to SGND.
COMP3 (Pin 8): Compensation pin for Channel 3. This is the
output of the internal transconductance amplifier. The com-
pensation network should be connected between this pin
and SGND.
FB3 (Pin 9): Feedback input for channel 3. Connect to Vout
through a voltage divider to set the Channel 3 output voltage.
NC (Pin 10): All NC pins should be connected to SGND.
RILIM (Pin 11): Connect a resistor from this pin to SGND to
set the internal ILIM reference current.
ON/UVLO (Pin 12): This is a dual function pin providing
thresholds for user adjustable UVLO and device shutdown.
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