LTC3890-3 Datasheet, PDF (9/40 Pages) Linear Technology – 60V Low IQ, Dual, 2-Phase Synchronous Step-Down DC/DC Controller

LTC3890-3
Pin Functions
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.
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
I_LIM Pin for Adjustable
Yes
No
Current Sense Voltage?
CLKOUT and PHASMD Pins
Yes
No
for PolyPhase^® Operation?
Independent PGOOD Pins for Yes; PGOOD1 and PGOOD2
Each Channel
No; PGOOD1 Only
Overvoltage Protection
Yes
Yes
Bottom Gate “Crowbar?”
Current Foldback During
Yes
Yes
Overcurrent Events
Light Load Operation When
Synchronized to External
Clock Using PLLIN/MODE Pin
Forced Continuous
Forced Continuous
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
LTC3890-2
Yes
Yes
Yes; PGOOD1 and PGOOD2
No; BG Not Forced On
No
Pulse-Skipping
LTC3890-3
No
No
No; PGOOD1 Only
No; BG Not Forced On
No
Pulse-Skipping
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
For more information www.linear.com/3890-3
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