Datasheet LTC3822 (Analog Devices) - 6

LTC3822
PIN FUNCTIONS BG (Pin 1):
Bottom Gate Driver Output. This pin drives
FREQ (Pin 6):
This pin serves as the frequency select the gate of the external bottom MOSFET. This pin has an input. Tying this pin to GND selects 300kHz operation; output swing from GND to BOOST. tying this pin to VIN selects 750kHz operation. Floating this pin selects 550kHz operation.
TG (Pin 2):
Top Gate Driver Output. This pin drives the gate of the external topside MOSFET. This pin has an output
IPRG (Pin 7):
Selects maximum peak sense voltage be- swing from GND to BOOST. tween the VIN and SW pins (i.e., the maximum allowed drop across the external top-side MOSFET). Tie to V
BOOST (Pin 3):
Positive Supply Pin for the Gate Driver IN, GND or fl oat to select 200mV, 82mV or 120mV respectively. Circuitry. A bootstrapped capacitor, charged through an external Schottky diode from VIN, is connected between
VFB (Pin 8):
Feedback Pin. This pin receives the remotely the BOOST and SW pins. Voltage swing at the BOOST pin sensed feedback voltage from an external resistor divider is from VIN to 2VIN. Alternatively, the diode can be connected across the output. to SW and a separate 5V supply to provide 5V gate drive.
I
In this case, the BOOST pin swings from 5V to 5V + V
TH (Pin 9):
Current Threshold and Error Amplifi er Com- IN. pensation Point. Nominal operating range on this pin is
VIN (Pin 4):
This pin powers the control circuitry and serves from 0.7V to 2V. The voltage on this pin determines the as the positive input to the differential current comparator. threshold of the main current comparator. Pin 4 must not be locally decoupled with a capacitor as it
RUN (Pin 10):
Run Control Input. Forcing this pin below is also the positive terminal for current sense. 1.1V shuts down the chip. Driving this pin to VIN or releas-
SW (Pin 5):
Switch Node Connection to Inductor. This pin ing this pin enables the chip to start-up with the internal is also the negative input to the differential current com- soft-start. parator and an input to the reverse current comparator.
GND (Pin 11):
Exposed Pad. The exposed pad is ground Normally this pin is connected to the source of the external and must be soldered to the PCB ground for electrical top-side MOSFET, the drain of the external bottom-side contact and optimal thermal performance. MOSFET, and the inductor. 3822fa 6