Datasheet

LT3740
5
3740fc
Error Amplifi er Transconductance
vs Temperature
BIAS-V
IN
to Enable Controller
vs Temperature
Undervoltage Lockout Threshold
vs Temperature
PIN FUNCTIONS
SN
(Pin 1): Negative Current Sensing Pin. Connect this
pin to the source of the bottom MOSFET for No R
SENSE
or 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
IN
or BIAS).
SN
+
(Pin 5): Positive Current Sensing Pin. Connect this
pin to the drain of the bottom MOSFET for No R
SENSE
or
to a 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
IN
.
SWB (Pin 9): Switch Pin of the Internal Boost. Connect
the boost inductor here.
V
IN
(Pin 10): Input Supply Pin. Must be locally bypassed
with a capacitor.
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
IN
for current sense voltage limit of 105mV.
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.
TEMPERATURE (°C)
–50
ERROR AMP (µs)
340
390
370
380
350
360
400
3740 G12
330
320
310
300
25 500–25
75
100
TEMPERATURE (°C)
–50
BIAS-V
IN
(V)
7.20
7.45
7.35
7.40
7.25
7.30
7.50
3740 G13
7.15
7.10
7.05
7.00
25 500–25
75
100
TEMPERATURE (°C)
–50
UNDERVOLTAGE LOCKOUT V
IN
(V)
2.0
2.5
1.5
3.0
3740 G14
1.0
0.5
0
25 500–25
75
100
TYPICAL PERFORMANCE CHARACTERISTICS
(T
A
= 25°C, unless otherwise noted)