ltc3890-1 Linear Technology Corporation, ltc3890-1 Datasheet - Page 8

• Manufacturer Part Number: ltc3890-1
• Description: 60v Low Iq, Dual, 2-phase Synchronous Step-down Dc/dc Controller
• Manufacturer: Linear Technology Corporation

LTC3890-1
PIN FUNCTIONS
ITH1, ITH2 (Pin 1, Pin 13): Error Amplifi er Outputs and
Switching Regulator Compensation Points. Each associ-
ated channel’s current comparator trip point increases
with this control voltage.
V
feedback voltage for each controller from an external
resistive divider across the output.
SENSE1
differential current comparators are normally connected
to DCR sensing networks or current sensing resistors.
The ITH pin voltage and controlled offsets between the
SENSE
the current trip threshold.
SENSE1
Differential Current Comparators. When greater than
INTV
current comparator.
FREQ (Pin 5): The Frequency Control Pin for the Internal
VCO. Connecting the pin to GND forces the VCO to a fi xed
low frequency of 350kHz. Connecting the pin to INTV
forces the VCO to a fi xed high frequency of 535kHz.
Other frequencies between 50kHz and 900kHz can be
programmed using a resistor between FREQ and GND.
An internal 20μA pull-up current develops the voltage to
be used by the VCO to control the frequency.
PLLIN/MODE (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. When not syn-
chronizing to an external clock, this input, which acts on
both controllers, determines how the LTC3890-1 operates
8
FB1
, V
CC
–
FB2
+
–
– 0.5V, the SENSE
and SENSE
, SENSE2
, SENSE2
(Pin 2, Pin 12): Receives the remotely sensed
+
–
+
(Pin 3, Pin 11): The (+) input to the
(Pin 4, Pin 10): The (–) Input to the
pins in conjunction with R
–
pin supplies current to the
SENSE
set
CC
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 fl oated. Tying this
pin to INTV
Tying this pin to a voltage greater than 1.2V and less than
INTV
SGND (Pin 7): Small-signal ground common to both
controllers, must be routed separately from high current
grounds to the common (–) terminals of the C
tors.
RUN1, RUN2 (Pin 8, Pin 9): Digital Run Control Inputs for
Each Controller. Forcing either of these pins below 1.2V
shuts down that controller. Forcing both of these pins
below 0.7V shuts down the entire LTC3890-1, reducing
quiescent current to approximately 14μA.
INTV
Regulator. The driver and control circuits are powered
from this voltage source. Must be decoupled to power
ground with a minimum of 4.7μF ceramic or other low
ESR capacitor. Do not use the INTV
purpose.
EXTV
Connected to INTV
bypassing the internal LDO powered from V
EXTV
the Applications Information section. Do not exceed 14V
on this pin.
PGND (Pin 21): Driver Power Ground. Connects to the
sources of bottom (synchronous) N-channel MOSFETs
and the (–) terminal(s) of C
V
be tied between this pin and the signal ground pin.
IN
(Pin 22): Main Supply Pin. A bypass capacitor should
CC
CC
CC
CC
(Pin 19): Output of the Internal Linear Low Dropout
– 1.3V selects pulse skipping operation.
(Pin 20): External Power Input to an Internal LDO
is higher than 4.7V. See EXTV
CC
forces continuous inductor current operation.
CC
. This LDO supplies INTV
IN
.
CC
pin for any other
CC
Connection in
IN
IN
CC
whenever
capaci-
power,
38901f