LTM4623_15 Datasheet, PDF (6/26 Pages) Linear Technology – Ultrathin 20VIN, 3A Step-Down DC/DC Module Regulator

LTM4623
Pin Functions
PACKAGE ROW AND COLUMN LABELING MAY VARY
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
LAYOUT CAREFULLY.
COMP (A1): Current Control Threshold and Error Amplifier
Compensation Point. The current comparator’s trip thresh-
old is linearly proportional to this voltage, whose normal
range is from 0.3V to 1.8V. Tie the COMP pins together for
parallel operation. The device is internally compensated.
This is an output pin. Do not force a voltage on this pin.
TRACK/SS (A2): Output Tracking and Soft-Start Input.
Allows the user to control the rise time of the output volt-
age. Putting a voltage below 0.6V on this pin bypasses the
internal reference input to the error amplifier, and servos
the FB pin to match the TRACK/SS voltage. Above 0.6V,
the tracking function stops and the internal reference
resumes control of the error amplifier. There’s an internal
2µA pull-up current from INTV_CC on this pin, so putting a
capacitor here provides a soft-start function.
RUN (A3): Run Control Input of the Switching Mode
Regulator. Enables chip operation by tying RUN above
1.2V. Pulling it below 1.1V shuts down the part. Do not
leave floating.
FREQ (A4): Frequency is set internally to 1MHz. An ex-
ternal resistor can be placed from this pin to SGND to
increase frequency, or from this pin to INTV_CC to reduce
frequency. See the Applications Information section for
frequency adjustment.
FB (B1): The Negative Input of the Error Amplifier. Internally,
this pin is connected to V_OUT with a 60.4k precision resis-
tor. Different output voltages can be programmed with an
additional resistor between the FB and SGND pins. Tying
the FB pins together allows for parallel operation. See the
Applications Information section for details.
PHMODE (B2): Control Input to Phase Selector of the
Switching Mode Regulator Channel. This pin determines
the phase relationship between internal oscillator and
CLKOUT signal. Tie it to INTV_CC for 2-phase operation, tie
it to SGND for 3-phase operation, and tie it to INTV_CC/2
for 4-phase operation.
GND (B3, C3, D3-D4, E3): Power Ground Pins for Both
Input and Output Returns.
SGND (B4): Signal Ground Connection. Tie to GND with
minimum distance. Connect FREQ resistor, COMP com-
ponent, MODE, TRACK/SS component, FB resistor to this
pin as needed.
V_OUT (C1, D1-D2, E1-E2): Power Output Pins. Apply out-
put load between these pins and GND pins. Recommend
placing output decoupling capacitance directly between
these pins and GND pins.
PGOOD (C2): Output Power Good with Open-Drain Logic.
PGOOD is pulled to ground when the voltage on the FB pin
is not within ±10% of the internal 0.6V reference.
MODE (C4): Operation Mode Select. Tie this pin to INTV_CC
to force continuous synchronous operation at all output
loads. Tying it to SGND enables discontinuous mode
operation at light loads. Do not leave floating.
SV_IN (C5): Signal V_IN. Input voltage to the on-chip 3.3V
regulator. Tie this pin to the V_IN pin in most applications.
Otherwise connect SV_IN to an external voltage supply of
at least 4V which must also be greater than V_OUT.
V_IN (D5, E5): Power Input Pins. Apply input voltage be-
tween these pins and GND pins. Recommend placing
input decoupling capacitance directly between V_IN pins
and GND pins.
INTV_CC (E4): Internal 3.3V Regulator Output. The internal
power drivers and control circuits are powered from this
voltage. This pin is internally decoupled to GND with a
1µF low ESR ceramic capacitor.
CLKIN (A5): External Synchronization Input to Phase
Detector of the Switching Mode Regulator. This pin is
internally terminated to SGND with 20k. The phase-locked
loop will force the top power NMOS’s turn-on signal to
be synchronized with the rising edge of the CLKIN signal.
CLKOUT (B5): Output Clock Signal for PolyPhase Op-
eration of the Switching Mode Regulator. The phase of
CLKOUT with respect to CLKIN is determined by the state
of the PHMODE pin. CLKOUT’s peak-to-peak amplitude
is INTV_CC to GND. This is an output pin. Do not force a
voltage on this pin.
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