Datasheet LT3740 (Analog Devices) - 5

LT3740
TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C, unless otherwise noted) Error Amplifi er Transconductance BIAS-VIN to Enable Controller Undervoltage Lockout Threshold vs Temperature vs Temperature vs Temperature
400 7.50 3.0 390 7.45 2.5 380 7.40 (V) IN 370 7.35 2.0 360 (V) 7.30 IN 350 7.25 1.5 340 BIAS-V 7.20 TAGE LOCKOUT V ERROR AMP (μs) 1.0 330 7.15 VOL 320 7.10 UNDER 0.5 310 7.05 300 7.00 0 –50 –25 0 25 50 75 100 –50 –25 0 25 50 75 100 –50 –25 0 25 50 75 100 TEMPERATURE (°C) TEMPERATURE (°C) TEMPERATURE (°C) 3740 G12 3740 G13 3740 G14
PIN FUNCTIONS SN– (Pin 1):
Negative Current Sensing Pin. Connect this
VIN (Pin 10):
Input Supply Pin. Must be locally bypassed pin to the source of the bottom MOSFET for No RSENSE with a capacitor. or to a current sense resistor.
RANGE (Pin 11):
Current Limit Range Select Pin. Ground
PGND (Pin 2):
Power Ground. Connect this pin closely to this pin for 50mV current sense voltage limit. Leave this the source of the bottom N-channel MOSFET. pin open for 80mV current sense voltage limit. Connect this pin to V
BGATE (Pin 3):
Bottom Gate Drive. Drives the gate of the IN for current sense voltage limit of 105mV. bottom N-channel MOSFET.
PGOOD (Pin 12):
Power Good Output. Open collector logic output that is pulled low when the FB voltage lower
BGDP (Pin 4):
Bottom Gate Drive Power Supply. Connect than 720mV. this pin to a voltage source higher than 7V (VIN or BIAS).
SHDN (Pin 13):
Shutdown Pin. Connect to 2.5V or higher to
SN+ (Pin 5):
Positive Current Sensing Pin. Connect this enable device; 0.5V or less to disable device. Also, this pin pin to the drain of the bottom MOSFET for No RSENSE or functions as soft-start when a voltage ramp is applied. to a current sense resistor.
XREF (Pin 14):
External Reference Pin. This pin sets the
SW (Pin 6):
Switch Node. Connect this pin to the source FB voltage externally between 0V and 0.8V. It can be used of the top N-channel MOSFET and the drain of the bottom to slave the output voltage during normal operation or the N-channel MOSFET. output start-up behavior to an external signal source. Tie
TGATE (Pin 7):
Top Gate Drive. Drives the gate of the top this pin to 1V or higher to use the internal 0.8V reference. N-channel MOSFET to BIAS.
FB (Pin 15):
Feedback Pin. Pin voltage is regulated to 0.8V
BIAS (Pin 8):
Top Gate Drive Power Supply. Connect a if internal reference is used or to the XREF pin if voltage capacitor between this pin and VIN. is between 0V and 0.8V. Connect the feedback resistor
SWB (Pin 9):
Switch Pin of the Internal Boost. Connect divider to this pin. the boost inductor here. 3740fc 5