LTC3785-1 Linear Technology, LTC3785-1 Datasheet - Page 6

• Manufacturer Part Number: LTC3785-1
• Description: Buck-Boost Controller
• Manufacturer: Linear Technology

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PIN FUNCTIONS
LTC3785-1
MODE (Pin 8): Burst Mode Control Pin.
• MODE = High: Enable Burst Mode Operation. In Burst
• MODE = Low: Disable Burst Mode operation and maintain
PGOOD (Pin 9): Open drain output. PGOOD is pulled to
ground when the voltage on V
of its setpoint. PGOOD will also be pulled low when the
part is in shutdown or input UVLO.
I
inverting Input. This pin is normally connected to the drain
of the N-channel MOSFET D (TG2 driven).
V
Switch D. This pin will swing from a diode below V
to V
SW2 (Pin 13): Ground Reference for Driver D. Gate drive
from TG2 will reference to the common point of output
switches C and D.
I
ing Input. This pin is normally connected to the source of
the N-channel MOSFET D (TG2 driven).
V
Switches. Connect this pin to V
BG1, BG2 (Pins 17, 15): Bottom gate driver pins drive
the ground referenced N-channel MOSFET switches B
and C.
6
SVOUT
SSW2
BST2
DRV
Mode operation the operation is variable frequency,
which provides a signifi cant effi ciency improvement
at light loads. The Burst Mode operation will continue
until the pin is driven low.
low noise, constant frequency operation.
OUT
(Pin 14): Reverse Current Limit Comparator Invert-
(Pin 16): Driver Supply for Ground Referenced
(Pin 11): Boosted Floating Driver Supply for Boost
(Pin 10): Reverse Current Limit Comparator Non-
+ V
CC
– V
DIODE
.
SENSE
CC
potential.
is not within ±7.5%
CC
up
I
inverting Input. This pin is normally connected to the
source of the N-channel MOSFET A (TG1 driven).
SW1 (Pin 19): Ground Reference for Driver A. Gate drive
from TG1 will reference to the common point of output
switches A and B.
TG1, TG2 (Pins 20, 12): Top gate drive pins drive the
top N-channel MOSFET switches A and D with a voltage
swing equal to V
and SW2 nodes respectively.
V
Buck Switch A. This pin will swing from a diode below
V
I
ing Input. This pin is normally connected to the drain of
N-channel MOSFET A (TG1 driven).
V
driver and control circuits are powered from this voltage
to limit the maximum VGS drive voltage. Decouple this pin
to power ground with at least a 4.7μF ceramic capacitor.
For low V
V
V
ceramic capacitor of at least 10μF is recommended close
to the V
Exposed Pad (Pin 25): The GND and PGND pins are con-
nected to the Exposed Pad which must be connected to
the PCB ground for electrical contact and rated thermal
performance.
SSW1
SVIN
BST1
CC
CC
OUT
IN
(Pin 24): Input Supply Pin for the V
up to V
(Pin 23): Internal 4.5V LDO Regulator Output. The
(Pin 22): Forward Current Limit Comparator Invert-
through a Schottky diode.
(Pin 18): Forward Current Limit Comparator Non-
(Pin 21): Boosted Floating Driver Supply for the
IN
IN
and GND pins.
IN
applications, V
+ V
CC
CC
– V
– V
DIODE
DIODE
CC
.
superimposed on the SW1
can be bootstrapped from
CC
Regulator. A
37851f