Datasheet LTC3713 (Analog Devices) - 7

LTC3713
U U U PI FU CTIO S RUN/SS (Pin 1):
Run Control and Soft-Start Input. A
VFB2 (Pin 12):
Boost Converter Feedback. The VFB2 pin is capacitor to ground at this pin sets the ramp time to full connected to INTVCC through a resistor divider to set the output current (approximately 3s/µF) and the time delay voltage on INTVCC. Set INTVCC voltage according to: for overcurrent latchoff (see Applications Information). V Forcing this pin below 0.8V shuts down the device. INTVCC = 1.23V(1 + RF4/RF3)
SW2 (Pin 13):
Boost Converter Switch Pin. Connect
VON (Pin 2):
On-Time Voltage Input. Voltage trip point for inductor/diode for boost converter portion here. Minimize the on-time comparator. Tying this pin to the output trace area at this pin to keep EMI down. voltage makes the on-time proportional to VOUT. The comparator input defaults to 0.7V when the pin is grounded,
PGND (Pins 14, 19):
Power Ground. Connect these pins 2.4V when the pin is tied to INTV closely to the source of the bottom N-channel MOSFET, CC. the (–) terminal of C
PGOOD (Pin 3):
Power Good Output. Open-drain logic VCC and the (–) terminal of CIN. output that is pulled to ground when the output voltage is
VIN2 (Pin 15):
Input Supply Pin for Boost Converter not within ±7.5% of the regulation point. Portion of LTC3713. Must be locally bypassed.
V V RNG (Pin 4):
Sense Voltage Range Input. The voltage at
IN1 (Pin 16):
Main Input Supply. Decouple this pin to this pin is ten times the nominal sense voltage at maxi- PGND with an RC filter (1Ω, 0.1µF). mum output current and can be set from 0.5V to 2V by a
INTVCC (Pin 17):
Internal Regulator Output. The driver and resistive divider from INTVCC. The nominal sense voltage control circuits are powered from this voltage. Decouple defaults to 70mV when this pin is tied to ground, 140mV this pin to power ground with a minimum of 4.7µF low ESR when tied to INTVCC. tantalum or ceramic capacitor.
FCB (Pin 5):
Forced Continuous Input. Tie this pin to
BG (Pin 18):
Bottom Gate Drive. Drives the gate of the ground to force continuous synchronous operation at low bottom N-channel MOSFET between ground and INTVCC. load, to INTVCC to enable discontinuous mode operation at low load or to a resistive divider from a secondary output
SENSE– (Pin 20):
Negative Current Sense Comparator when using a secondary winding. Input. The (–) input to the current comparator is normally connected to power ground unless using a resistive di-
ITH (Pin 6):
Current Control Threshold and Error Amplifier vider from INTVCC (see Applications Information). Compensation Point. The current comparator threshold increases with this control voltage. The voltage ranges
SENSE+ (Pin 21):
Positive Current Sense Comparator from 0V to 2.4V with 0.8V corresponding to zero sense Input. The (+) input to the current comparator is normally voltage (zero current). connected to the SW1 node unless using a sense resistor (see Applications Information).
SGND (Pins 7, 11):
Signal Ground. All small-signal com- ponents and compensation components should connect to
SW1 (Pin 22):
Switch Node. The (–) terminal of the this ground, which in turn connects to PGND at one point. bootstrap capacitor CB connects here. This pin swings from a diode voltage drop below ground up to VIN.
ION (Pin 8):
On-Time Current Input. Tie a resistor from VIN to this pin to set the one-shot timer current and thereby set
TG (Pin 23):
Top Gate Drive. Drives the top N-channel the switching frequency. MOSFET with a voltage swing equal to INTVCC superim- posed on the switch node voltage SW1.
VFB1 (Pin 9):
Error Amplifier Feedback Input. This pin connects the error amplifier input to an external resistive
BOOST (Pin 24):
Boosted Floating Driver Supply. The (+) divider from V terminal of the bootstrap capacitor C OUT. B connects here. This pin swings from a diode voltage drop below INTVCC up to
SHDN (Pin 10):
Shutdown, Active Low. Tie to 1V or more VIN + INTVCC. to enable boost converter portion of the LTC3713. Ground to shut down. 3713fa 7