LTC3892_15 Datasheet, PDF (11/36 Pages) Linear Technology – 60V Low IQ, Dual, 2-Phase Synchronous Step-Down DC/DC Controller

LTC3892/LTC3892-1
Pin Functions (LTC3892 (QFN)/LTC3892-1 (TSSOP))
BG1, BG2 (Pins 23, 19/Pins 24, 20): High Current Gate
Drives for Bottom N-Channel MOSFETs. Voltage swing at
these pins is from ground to DRV_CC.
BOOST1, BOOST2 (Pins 24, 18/Pins 25, 19): Bootstrapped
Supplies to the Topside Floating Drivers. Capacitors are
connected between the BOOST and SW pins. Voltage
swing at BOOST1 and BOOST2 pins is from approximately
DRV_CC to (V_IN1,2 + DRV_CC).
SW1, SW2 (Pins 25, 17/Pins 26, 18): Switch Node Con-
nections to Inductors.
TG1, TG2 (Pins 26, 16/Pins 27, 17): High Current Gate
Drives for Top N-Channel MOSFETs. These are the outputs
of floating drivers with a voltage swing equal to DRV_CC
superimposed on the switch node voltage SW.
TRACK/SS1, TRACK/SS2 (Pins 27, 15/Pins 28, 16):
External Tracking and Soft-Start Input. The LTC3892/
LTC3892-1 regulates the negative input (EA^–) of the er-
ror amplifier to the smaller of 0.8V or the voltage on the
TRACK/SS pin. An internal 10µA pull-up current source
is connected to this pin. A capacitor to ground at this pin
sets the ramp time at start-up to the final regulated output
voltage. Alternatively, a resistor divider on another sup-
ply connected to the TRACK/SS pin allows the LTC3892/
LTC3892-1 output voltage to track the other supply during
start-up. The TRACK/SS pin is pulled low in shutdown or
in undervoltage lockout.
VPRG1 (Pin 28/NA): Channel 1 Output Voltage Control Pin.
This pin sets channel 1 to adjustable output mode using
external feedback resistors or fixed 3.3V/5V output mode.
Floating this pin allows the output to be programmed from
0.8V to 60V with an external resistor divider, regulating
V_FB1 to 0.8V. This pin is only available on the LTC3892,
not the LTC3892-1.
ITH1, ITH2 (Pins 29, 12/Pins 1, 13): Error Amplifier
Outputs and Switching Regulator Compensation Points.
Each associated channel’s current comparator trip point
increases with this control voltage.
V_FB1 (Pin 30/Pin 2): For the LTC3892-1, this pin receives
the remotely sensed feedback voltage for channel 1 from
an external resistor divider across the output.
For the LTC3892, if the VPRG1 pin is floating, the V_FB1 pin
receives the remotely sensed feedback voltage for chan-
nel 1 from an external resistor divider across the output.
If VPRG1 is tied to GND or INTV_CC, the V_FB1 pin receives
the remotely sensed output voltage directly.
SENSE1⁺, SENSE2⁺ (Pins 31, 10/Pins 3, 11): The (+)
Input to the Differential Current Comparators. The ITH pin
voltage and controlled offsets between the SENSE^– and
SENSE⁺ pins in conjunction with R_SENSE set the current
trip threshold.
SENSE1^–, SENSE2^– (Pins 32, 9/Pins 4, 10): The (–) Input
to the Differential Current Comparators. When SENSE1,2^– is
greater than INTV_CC, then SENSE1,2^– pin supplies current
to the current comparator.
GND (Exposed Pad Pin 33/Exposed Pad Pin 29): Ground.
The exposed pad must be soldered to the PCB for rated
electrical and thermal performance.
Table 1. Summary of the Differences Between the LTC3892 and LTC3892-1
LTC3892
LTC3892-1
ILIM pin for selectable current sense voltage? Yes; 50mV, 75mV, or 100mV
No; fixed 75mV
VPRG1 pin for fixed or adjustable V_OUT1?
Yes; fixed 3.3V or 5V (with internal resistor divider) No; only adjustable with external resistor divider
or adjustable with external resistor divider
Independent PGOOD output for each channel? Yes; PGOOD1 and PGOOD2
No PGOOD function
Package
32-Pin 5mm × 5mm QFN (UH32)
28-Lead TSSOP (FE28)
For more information www.linear.com/LTC3892
38921f
11