LTC3890
pin FuncTions
TG1, TG2 (Pin 26, Pin 15):
High Current Gate Drives for
Top N-Channel MOSFETs. These are the outputs of float-
ing drivers with a voltage swing equal to INTV
CC
– 0.5V
superimposed on the switch node voltage SW.
PGOOD1, PGOOD2 (Pin 27, Pin 14):
Open-Drain Logic
Output. PGOOD1,2 is pulled to ground when the voltage
on the V
FB1,2
pin is not within ±10% of its set point.
I
LIM
(Pin 28):
Current Comparator Sense Voltage Range
Inputs. Tying this pin to SGND, FLOAT or INTV
CC
sets the
maximum current sense threshold to one of three different
levels for both comparators.
TRACK/SS1, TRACK/SS2 (Pin 29, Pin 13):
External
Tracking and Soft-Start Input. The LTC3890 regulates the
V
FB1,2
voltage to the smaller of 0.8V or the voltage on the
TRACK/SS1,2 pin. An internal 1µA pull-up current source
is connected to this pin. A capacitor to ground at this
pin sets the ramp time to final regulated output voltage.
Alternatively, a resistor divider on another voltage supply
connected to this pin allows the LTC3890 output to track
the other supply during start-up.
ITH1, ITH2 (Pin 30, Pin 12):
Error Amplifier Outputs and
Switching Regulator Compensation Points. Each associ-
ated channel’s current comparator trip point increases
with this control voltage.
V
FB1
, V
FB2
(Pin 31, Pin 11):
Receives the remotely sensed
feedback voltage for each controller from an external
resistive divider across the output.
SENSE1
+
, SENSE2
+
(Pin 32, Pin 10):
The (+) input to the
differential current comparators are normally connected
to DCR sensing networks or current sensing resistors.
The ITH pin voltage and controlled offsets between the
SENSE
–
and SENSE
+
pins in conjunction with R
SENSE
set
the current trip threshold.
3890fb
9
LINEAR [ LINEAR INTEGRATED SYSTEMS ]
