8
LTC1436A
LTC1436-PLL-A/LTC1437A
14367afb
PIN FUNCTIONS
UUU
Forcing this pin below 1.3V causes the device to be shut
down. In shutdown all functions are disabled.
TGL: High Current Gate Drive for Main Top N-Channel
MOSFET. This is the output of a floating driver with a
voltage swing equal to INTV
CC
superimposed on the
switch node voltage SW.
TGS: High Current Gate Drive for a Small Top N-Channel
MOSFET. This is the output of a floating driver with a
voltage swing equal to INTV
CC
superimposed on the
switch node voltage SW. Leaving TGS open invokes Burst
Mode operation at low load currents.
BG: High Current Gate Drive for Bottom N-Channel
MOSFET. Voltage swing at this pin is from ground to
INTV
CC
(DRV
CC
).
SFB: Secondary Winding Feedback Input. Normally
connected to a feedback resistive divider from the
secondary winding. This pin should be tied to: ground to
force continuous operation; INTV
CC
in applications that
don’t use a secondary winding; and a resistive divider from
the output in applications using a secondary winding.
POR: Open Drain Output of an N-Channel Pull-Down. This
pin sinks current when the output voltage is 7.5% out of
regulation and releases 65536 oscillator cycles after the
output voltage rises to –5% of its regulated value. The
POR output is asserted when Run/SS is low independent
of V
OUT
.
LBO: Open Drain Output of an N-Channel Pull-Down. This
pin will sink current when the LBI pin goes below 1.19V.
LBI: The (+) Input of the Low Battery Voltage Comparator.
The (–) input is connected to a 1.19V reference.
PLLIN: External Synchronizing Input to Phase Detector.
This pin is internally terminated to SGND with 50kΩ. Tie
this pin to SGND in applications which do not use the
phase-locked loop.
PLL LPF: Output of Phase Detector and Control Input of
Oscillator. Normally a series RC lowpass filter network is
connected from this pin to ground. Tie this pin to SGND in
applications which do not use the phase-locked loop. Can
be driven by 0V to 2.4V logic signal for a frequency shifting
option.
AUXFB: Feedback Input to the Auxiliary Regulator/
Comparator. When used as a linear regulator, this input
can either be connected to an external resistive divider or
directly to the collector of the external PNP pass device for
12V operation. When used as a comparator, this is the
noninverting input of a comparator whose inverting input
is tied to the internal 1.19V reference. See Auxiliary
Regulator/Comparator in Applications Information section.
AUXON: Pulling this pin high turns on the auxiliary regulator/
comparator. The threshold is 1.19V.
AUXDR: Open Drain Output of the Auxiliary Regulator/
Comparator. The base of an external PNP device is
connected to this pin for use as a linear regulator. An
external pull-up resistor is required for use as a comparator.
A voltage > 9.5V on AUXDR causes the internal 12V
resistive divider to be connected to AUXFB.
