Datasheet

LTC3890-3
9
38903f
For more information www.linear.com/3890-3
BG1, BG2 (Pin 23, Pin 18): High Current Gate Drives
for Bottom (Synchronous) N-Channel MOSFETs. Voltage
swing at these pins is from ground to INTV
CC
.
BOOST1, BOOST2 (Pin 24, Pin 17): Bootstrapped Supplies
to the Topside Floating Drivers. Capacitors are connected
between the BOOST and SW pins and Schottky diodes are
tied between the BOOST and INTV
CC
pins. Voltage swing
at the BOOST pins is from INTV
CC
to (V
IN
+ INTV
CC
).
SW1, SW2 (Pin 25, Pin 16): Switch Node Connections
to Inductors.
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.
pin FuncTions
PGOOD1 (Pin 27): Open-Drain Logic Output. PGOOD1 is
pulled to ground when the voltage on the V
FB1
pin is not
within ±10% of its set point.
TRACK/SS1, TRACK/SS2 (Pin 28, Pin 14): External Track
-
ing and Soft-Start Input. The LTC3890-3 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 LTC3890-3 output to track
the other supply during start-up.
Table 1. Summary of the Differences Between the Parts in the LTC3890 Family
LTC3890 LTC3890-1 LTC3890-2 LTC3890-3
I
LIM
Pin for Adjustable
Current Sense Voltage?
Yes No Yes No
CLKOUT and PHASMD Pins
for PolyPhase
®
Operation?
Yes No Yes No
Independent PGOOD Pins for
Each Channel
Yes; PGOOD1 and PGOOD2 No; PGOOD1 Only Yes; PGOOD1 and PGOOD2 No; PGOOD1 Only
Overvoltage Protection
Bottom Gate “Crowbar?”
Yes Yes No; BG Not Forced On No; BG Not Forced On
Current Foldback During
Overcurrent Events
Yes Yes No No
Light Load Operation When
Synchronized to External
Clock Using PLLIN/MODE Pin
Forced Continuous Forced Continuous Pulse-Skipping Pulse-Skipping
SENSE Pins Common Mode
Range
Operation with SENSE
Common Mode < 0.5V
Requires V
FB
< 0.65V
Operation with SENSE
Common Mode < 0.5V
Requires V
FB
< 0.65V
Not Dependent on V
FB
Voltage. Makes It Easy to
Make a Non-synchronous
Boost or SEPIC Converter
with Ground-Referenced
Current Sensing
Not Dependent on V
FB
Voltage. Makes It Easy to
Make a Non-synchronous
Boost or SEPIC Converter
with Ground-Referenced
Current Sensing