ltc3787gn Linear Technology Corporation, ltc3787gn Datasheet - Page 10

• Manufacturer Part Number: ltc3787gn
• Description: Ltc3787 - Polyphase Synchronous Boost Controller
• Manufacturer: Linear Technology Corporation

LTC3787
pin FuncTions
SS (Pin 7/Pin 10): Output Soft-Start Input. A capacitor to
ground at this pin sets the ramp rate of the output voltage
during start-up.
SENSE2
tive Current Sense Comparator Input. The (–) input to the
current comparator is normally connected to the negative
terminal of a current sense resistor connected in series
with the inductor.
SENSE2
tive Current Sense Comparator Input. The (+) input to the
current comparator is normally connected to the positive
terminal of a current sense resistor. The current sense resis-
tor is normally placed at the input of the boost controller in
series with the inductor. This pin also supplies power to the
current comparator. The common mode voltage range on
SENSE
VFB (Pin 10/Pin 13): Error Amplifier Feedback Input. This
pin receives the remotely sensed feedback voltage from
an external resistive divider connected across the output.
ITH (Pin 11/Pin 14): Current Control Threshold and Error
Amplifier Compensation Point. The voltage on this pin sets
the current trip threshold.
NC (Pin 12/Pin 15): No Connect.
SW2, SW1 (Pin 13, Pin 24/Pin 16, Pin 27): Switch Node.
Connect to the source of the synchronous N-channel
MOSFET, the drain of the main N-channel MOSFET and
the inductor.
TG2, TG1 (Pin 14, Pin 23/Pin 17, Pin 26): Top Gate. Con-
nect to the gate of the synchronous N-channel MOSFET.
BOOST2, BOOST1 (Pin 15, Pin 22/Pin 18, Pin 25): Float-
ing power supply for the synchronous N-channel MOSFET.
Bypass to SW with a capacitor and supply with a Schottky
diode connected to INTV
10
+
–
+
and SENSE
, SENSE1
, SENSE1
+
–
–
(Pin 9, Pin 27/Pin 12, Pin 2): Posi-
(Pin 8, Pin 28/Pin 11, Pin 3): Nega-
pins is 2.5V to 38V (40V abs max).
CC
.
(QFN/SSOP)
PGND (Pin 19/Pin 22): Driver Power Ground. Connects
to the sources of bottom (main) N-channel MOSFETs and
the (–) terminal(s) of C
BG2, BG1 (Pin 16, Pin 21/Pin 19, Pin 24): Bottom Gate.
Connect to the gate of the main N-channel MOSFET.
INTV
Power supply for control circuits and gate drivers. De-
couple this pin to GND with a minimum 4.7μF low ESR
ceramic capacitor.
EXTV
pin is between 4.8V and 6V, an internal switch bypasses
the internal regulator and supply power to INTV
from EXTV
ground when not used.
VBIAS (Pin 20/Pin 23): Main Supply Pin. It is normally
tied to the input supply V
converter. A bypass capacitor should be tied between this
pin and the signal ground pin. The operating voltage range
on this pin is 4.5V to 38V (40V abs max).
PGOOD (Pin 25/Pin 28): Power Good Indicator. Open-drain
logic output that is pulled to ground when the output volt-
age is more than ±10 % away from the regulated output
voltage. To avoid false trips the output voltage must be
outside the range for 25μs before this output is activated.
ILIM (Pin 26/Pin 1): Current Comparator Sense Voltage
Range Input. This pin is used to set the peak current
sense voltage in the current comparator. Connect this pin
to SGND, open, and INTV
voltage to 50mV, 75mV and 100mV, respectively.
GND (Exposed Pad Pin 29) UFD Package: Ground. Must
be soldered to the PCB for rated thermal performance.
CC
CC
(Pin 18/Pin 21): External Power Input. When this
(Pin 17/Pin 20): Output of Internal 5.4V LDO.
CC
. Do not float this pin. It can be connected to
IN
CC
IN
and C
or to the output of the boost
to set the peak current sense
OUT
.
CC
directly
3787fa