
Pin Functions
V
SW(Pin 1): This is the drain of the internal NMOS power
switch. Minimize the metal trace area connected to this pin to
minimize EMI.
V
IN(Pin 2): Input Supply Pin. Bypass this pin with a capacitor
as close to the device as possible. The capacitor should
connect between V
IN and GND.
SHDN(Pin 3): Shutdown Pin. The shutdown pin signal is
active low. A voltage of less than 0.3V disables the device. A
voltage greater than 0.85V enables the device.
FSLCT(Pin 4): Frequency Select Pin. Connecting FSLCT to
AGND selects a 600 kHz operating frequency for the switch-
ing regulator. Connecting FSLCT to V
IN selects a 1.25 MHz
operating frequency. If FSLCT is left floating, the switching
frequency defaults to 600 kHz.
Vs+(Pin 5): Supply pin for the four Gamma buffers. Bypass
this pin with a capacitor as close to the device as possible.
The capacitor should connect between Vs+ and GND.
GMA1-in(Pin 6):Gamma Buffer input pin.
GMA2-in(Pin 7): Gamma Buffer input pin.
GMA3-in(Pin 8): Gamma Buffer input pin.
GMA4-in(Pin 9): Gamma Buffer input pin.
NC(Pin 10):No Connection.
NC(Pin 11): No Connection.
GMA4-out(Pin 12): Gamma Buffer output pin.
GMA3-out(Pin13): Gamma Buffer output pin.
GMA2-out(Pin 14): Gamma Buffer output pin.
GMA1-out(Pin 15): Gamma Buffer output pin.
SS(Pin 16): Softstart pin. Connect capacitor to SS pin and
AGND to slowly ramp inductor current on startup.
V
C(Pin
17): Compensation Network for Boost switching
regulator. Connect resistor/capacitor network between V
C
pin and AGND for boost switching regulator AC compensa-
tion.
FB(Pin 18): Feedback pin. Set the output voltage by select-
ing values of R1 and R2 using:
Connect the ground of the feedback network to the AGND
plane, which can be tied directly to the GND pin.
AGND(Pin 19): Analog ground pin. Ground connection for
the Gamma buffers and the boost switching regulator. AGND
must be tied directly to GND at the pins.
GND(Pin 20): Power ground pin. Ground connection for the
NMOS power device of the boost switching regulator. GND
must be tied directly to AGND at the pins.
Ordering Information
Order Number
Package Type
NSC Package Drawing
Supplied As
LM2711MT-ADJ
TSSOP-20
MTC20
73 Units, Rail
LM2711MTX-ADJ
TSSOP-20
MTC20
2500 Units, Tape and Reel
LM271
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