LTC3892-1_15 Datasheet, PDF (10/36 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))
FREQ (Pin 1/ Pin 5): The frequency control pin for the
internal VCO. Connecting this pin to GND forces the VCO
to a fixed low frequency of 350kHz. Connecting this pin
to INTV_CC forces the VCO to a fixed high frequency of
535kHz. Other frequencies between 50kHz and 900kHz can
be programmed using a resistor between FREQ and GND.
The resistor and an internal 20µA source current create a
voltage used by the internal oscillator to set the frequency.
PLLIN/MODE (Pin 2/Pin 6): External Synchronization
Input to Phase Detector and Forced Continuous Mode
Input. When an external clock is applied to this pin, the
phase-locked loop will force the rising TG1 signal to be
synchronized with the rising edge of the external clock,
and the regulators will operate in forced continuous
mode. When not synchronizing to an external clock, this
input, which acts on both controllers, determines how the
LTC3892/LTC3892-1 operates at light loads. Pulling this
pin to ground selects Burst Mode operation. An internal
100k resistor to ground also invokes Burst Mode operation
when the pin is floated. Tying this pin to INTV_CC forces
continuous inductor current operation. Tying this pin to
a voltage greater than 1.1V and less than INTV_CC – 1.3V
selects pulse-skipping operation. This can be done by
connecting a 100k resistor from this pin to INTV_CC.
PGOOD1, PGOOD2 (Pins 3, 4/NA): Open-Drain Logic
Output. PGOOD1,2 is pulled to ground when the voltage
on the respective V_FB1,2 pin is not within ±10% of its set
point. These pins are only available on the LTC3892, not
the LTC3892-1.
INTV_CC (Pin 5/Pin 7): Output of the Internal 5V Low Drop-
out Regulator. The low voltage analog and digital circuits
are powered from this voltage source. A low ESR 0.1µF
ceramic bypass capacitor should be connected between
INTV_CC and GND, as close as possible to the IC.
RUN1, RUN2 (Pins 6, 7/Pins 8, 9): Run Control Inputs
for Each Controller. Forcing any of these pins below 1.2V
shuts down that controller. Forcing all of these pins below
0.7V shuts down the entire LTC3892/LTC3892-1, reducing
quiescent current to approximately 3.6µA.
ILIM (Pin 8/NA): Current Comparator Sense Voltage Range
Input. Tying this pin to GND or INTV_CC or floating it sets
the maximum current sense threshold (for both channels)
to one of three different levels (50mV, 100mV, or 75mV
respectively). This pin is only available on the LTC3892,
not the LTC3892-1. For the LTC3892-1, the maximum
current sense threshold is 75mV.
V_FB2 (Pin 11/Pin 12): This pin receives the remotely sensed
feedback voltage for channel 2 from an external resistor
divider across the output.
DRVUV (Pin13/Pin 14): Determines the higher or lower
DRV_CC UVLO and EXTV_CC switchover thresholds, as listed
on the Electrical Characteristics table. Connecting DRVUV
to GND chooses the lower thresholds whereas tying DRVUV
to INTV_CC chooses the higher thresholds.
DRVSET (Pin 14/Pin 15): Sets the regulated output volt-
age of the DRV_CC LDO regulator. Connecting this pin to
GND sets DRV_CC to 6V whereas connecting it to INTV_CC
sets DRV_CC to 10V. Voltages between 5V and 10V can be
programmed by placing a resistor (50k to 100k) between
the DRVSET pin and GND.
DRV_CC (Pin 20/Pin 21): Output of the Internal or External
Low Dropout (LDO) Regulator. The gate drivers are pow-
ered from this voltage source. The DRV_CC voltage is set
by the DRVSET pin. Must be decoupled to ground with a
minimum of 4.7µF ceramic or other low ESR capacitor.
Do not use the DRV_CC pin for any other purpose.
EXTV_CC (Pin 21/Pin 22): External Power Input to an Internal
LDO Connected to DRV_CC. This LDO supplies DRV_CC power,
bypassing the internal LDO powered from V_IN whenever
EXTV_CC is higher than its switchover threshold (4.7V or
7.7V depending on the DRVSET pin). See EXTV_CC Con-
nection in the Applications Information section. Do not
float or exceed 14V on this pin. Do not connect EXTV_CC
to a voltage greater than V_IN. Connect to GND if not used.
V_IN (Pin 22/Pin 23): Main Supply Pin. A bypass capacitor
should be tied between this pin and the GND pin.
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