lt3740 Linear Technology Corporation, lt3740 Datasheet - Page 5

• Manufacturer Part Number: lt3740
• Description: Wide Operating Range, Valley Mode, No Rsense Synchronous Step-down Controller
• Manufacturer: Linear Technology Corporation

PI FU CTIO S
SN
pin to the source of the bottom MOSFET for No R
to a current sense resistor.
PGND (Pin 2): Power Ground. Connect this pin closely to
the source of the bottom N-channel MOSFET.
BGATE (Pin 3): Bottom Gate Drive. Drives the gate of the
bottom N-channel MOSFET.
BGDP (Pin 4): Bottom Gate Drive Power Supply. Connect
this pin to a voltage source higher than 7V (V
SN
to the drain of the bottom MOSFET for No R
current sense resistor.
SW (Pin 6): Switch Node. Connect this pin to the source
of the top N-channel MOSFET and the drain of the bottom
N-channel MOSFET.
TGATE (Pin 7): Top Gate Drive. Drives the gate of the top
N-channel MOSFET to BIAS.
BIAS (Pin 8): Top Gate Drive Power Supply. Connect a
capacitor between this pin and V
SWB (Pin 9): Switch Pin of the Internal Boost. Connect the
boost inductor here.
V
with a capacitor.
IN
–
+
U
(Pin 10): Input Supply Pin. Must be locally bypassed
(Pin 5): Positive Current Sensing Pin. Connect this pin
(Pin 1): Negative Current Sensing Pin. Connect this
U
U
IN
.
SENSE
IN
or BIAS).
SENSE
or to a
or
RANGE (Pin 11): Current Limit Range Select Pin. Ground
this pin for 50mV current sense voltage limit. Leave this
pin open for 80mV current sense voltage limit. Connect
this pin to V
PGOOD (Pin 12): Power Good Output. Open collector
logic output that is pulled low when the FB voltage lower
than 720mV.
SHDN (Pin 13): Shutdown Pin. Connect to 2.5V or higher
to enable device; 0.5V or less to disable device. Also, this
pin functions as soft-start when a voltage ramp is applied.
XREF (Pin 14): External Reference Pin. This pin sets the FB
voltage externally between 0V and 0.8V. It can be used to
slave the output voltage during normal operation or the
output start-up behavior to an external signal source. Tie
this pin to 1V or higher to use the internal 0.8V reference.
FB (Pin 15): Feedback Pin. Pin voltage is regulated to 0.8V
if internal reference is used or to the XREF pin if voltage is
between 0V and 0.8V. Connect the feedback resistor
divider to this pin.
V
Connect the external compensation RC to this pin. The
current comparator threshold increases with the voltage
of this pin.
Exposed Pad (Pin 17): Ground. Must be soldered to PCB
ground.
C
(Pin 16): Error Amplifier Compensation Pin.
IN
for current sense voltage limit of 105mV.
LT3740
3740fa
5