LTC3810-5
10
38105fd
pin FuncTions
BG (Pin 18): Bottom Gate Drive. The BG pin drives the
gate of the bottom N-channel synchronous switch MOSFET.
This pin swings from BGRTN to DRV
CC
.
BGRTN (Pin 19): Bottom Gate Return. This pin connects to
the source of the pulldown MOSFET in the BG driver and
is normally connected to ground. Connecting a negative
supply to this pin allows the synchronous MOSFET ’s gate
to be pulled below ground to help prevent false turn-on
during high dV/dt transitions on the SW node. See the
Applications Information section for more details.
SENSE
+
, SENSE
–
(Pin 24, Pin 20): Current Sense Com-
parator Input. The (+) input to the current comparator is
normally connected to SW unless using a sense resistor.
The (–) input is used to accurately kelvin sense the bottom
side of the sense resistor or MOSFET.
SW (Pin 25): Switch Node Connection to Inductor and
Bootstrap Capacitor. The voltage swing at this pin is –0.7V
(a Schottky diode (external) voltage drop) to V
IN
.
TG (Pin 26): Top Gate Drive. The TG pin drives the gate of
the top N-channel synchronous switch MOSFET. The TG
driver draws power from the BOOST pin and returns to the
SW pin, providing true floating drive to the top MOSFET.
BOOST (Pin 27): Top Gate Driver Supply. The BOOST pin
supplies power to the floating TG driver. BOOST should
be bypassed to SW with a low ESR (X5R or better) 0.1µF
capacitor. An additional fast recovery Schottky diode from
DRV
CC
to the BOOST pin will create a complete floating
charge-pumped supply at BOOST.
I
ON
(Pin 31): On-Time Current Input. Tie a resistor from V
IN
to this pin to set the one-shot timer current and thereby
set the switching frequency.
SGND (Exposed Pad Pin 33): Signal Ground. All small-
signal components should connect to this ground and
eventually connect to PGND at one point.
