LTC3829
9
3829fc
For more information www.linear.com/LTC3829
PIN FUNCTIONS
(UHF/FE)
ISET (Pin 15/Pin 17): Stage Shedding Comparator and
Burst Mode Comparator Programming Pin. A resistor to
ground programs the stage shedding comparator threshold
or Burst Mode comparator threshold and its current limit
depending on MODE pin setting.
I
LIM
(Pin 16/Pin 18): Current Comparator Sense Voltage
Range Pin. This pin is to be programmed to SGND, FLOAT
or INTV
CC
to set the maximum current sense threshold to
one of three different levels for each comparator.
PGOOD (Pin 17/Pin 19): Power Good Indicator Output.
Open-drain logic out that is pulled to ground when the
output exceeds ±10% regulation window after the internal
100µs power bad mask timer expires.
PLLIN (Pin 18/Pin 20): External Synchronization Pin. A
clock on the pin synchronizes the internal oscillator with
the clock on this pin.
EXTV
CC
(Pin 23/Pin 25): External Power Input to an Inter-
nal Switch Connected to INTV
CC
. This switch closes and
supplies the IC power, bypassing the internal low dropout
regulator, whenever EXTV
CC
is higher than 4.7V. Do not
exceed 6V on this pin and ensure V
IN
> V
EXTVCC
at all times.
INTV
CC
(Pin 24/Pin 26): Internal 5V Regulator Output. The
control circuits are powered from this voltage. Decouple
this
pin to PGND with a minimum of 4.7µF low ESR tan-
talum or ceramic capacitor.
V
IN
(Pin 25/Pin 27): Main Input Supply. Decouple this pin
to PGND with a capacitor (0.1µF to 1µF).
BG1, BG2, BG3 (Pins 30, 29, 22/Pins 32, 31, 24): Bot
-
tom Gate Driver Outputs. These pins drive the gates of the
bottom N-channel MOSFETs between PGND and INTV
CC
.
SW1, SW2, SW3 (Pins 31, 28, 21/Pins 33, 30, 23):
Switch Node Connections to Inductors. Voltage swing
at these pins is from a Schottky diode (external) voltage
drop below ground to V
IN
.
TG1, TG2, TG3 (Pins 32, 27, 20/Pins 34, 29, 22): Top Gate
Driver Outputs. These are the outputs of floating drivers
with a voltage swing equal to INTV
CC
superimposed on
the switch nodes voltages.
BOOST1, BOOST2, BOOST3 (Pins 33, 26, 19/Pins 35,
28, 21): Boosted Floating Driver Supplies. The (+) terminal
of the bootstrap capacitors connect to these pins. These
pins swing from a diode voltage drop below INTV
CC
up
to V
IN
+ INTV
CC
.
CLKOUT (Pin 34/Pin 36): Clock Output Pin. CLKOUT is
60° out of phase relative to channel 1 in non-shedding
mode. During stage shedding, CLKOUT is 180° out of
phase with channel 1.
MODE (Pin 35/Pin 37): Forced Continuous Mode, Burst
Mode or Shed Mode Selection Pin. Connect this pin to
SGND to force IC in continuous mode of operation. Con-
nect to
INTV
CC
to enable shed mode operation. Leave the
pin floating to enable Burst Mode operation.
IFAST (Pin 36/Pin 38): Programmable Pin for Nonlinear
Control Trip Threshold. A resistor to ground programs the
tripping threshold for nonlinear control circuit. Connect
this pin to INTV
CC
to disable this feature. See Applications
Information section for details. Leave this pin floating
when it is not used.
ITEMP (Pin 37/Pin 1): Input of the Temperature Sensing
Comparator. Connect this pin to external NTC resistors
placed near inductors.
DIFFOUT (Pin 38/Pin 2): Output of Remote Sensing
Differential Amplifier. Connect this pin to V
FB
through a
resistive divider.
SGND/PGND (Exposed Pad Pin 39/Exposed Pad Pin 39):
Combined Signal and Power Ground Pad. Connect this pad
closely to the sources of the bottom N-channel MOSFETs,
the (–) terminal of C
VCC
and the (–) terminal of C
IN
. All
small-signal components and compensation components
should also Kelvin-connect to this pad.
