Datasheet

LTM4649
7
4649f
For more information www.linear.com/LTM4649
PIN FUNCTIONS
GND (A1-A5, A7-A11, B1, B9-B11, E1, F3, F5, G1-G7):
Ground Pins for Both Input and Output Returns. All ground
pins need to connect with large copper areas underneath
the unit.
TEMP (A6): Onboard Temperature Diode for Monitoring
the VBE Junction Voltage Change with Temperature. See
the Applications Information section.
CLKIN (B3): External Synchronization Input to Phase De-
tector Pin. A clock on this pin will enable synchronization
with forced continuous operation. See the Applications
Information section.
PHMODE (B4): This pin can be tied to GND, tied to INTV
CC
or left floating. This pin determines the relative phases
between the internal controllers and the phasing of the
CLKOUT signal. See Table 2 in the Operation section.
MODE (B5): Mode Select Input. Connect this pin to IN-
TV
CC
to enable Burst Mode operation. Connect to ground
to enable forced continuous mode of operation. Floating
this pin will enable pulse-skipping mode.
NC (B7-B8, C3-C4): No Connection Pins. Either float these
pins or connect them to GND for thermal purpose.
V
IN
(C1, C8, C9, D1, D3-D5, D7-D9 and E8): Power Input
Pins. Apply input voltage between these pins and GND
pins. Recommend placing input decoupling capacitance
directly between V
IN
pins and GND pins.
V
OUT
(C10-C11, D10-D11, E9-E11, F9-F11, G10-G11):
Power Output Pins. Apply output load between these pins
and GND pins. Recommend placing output decoupling
capacitance directly between these pins and GND pins.
SW (C5): Switching Node of the Circuit. This pin is used
to check the switching frequency. Leave pin floating. A
resistor-capacitor snubber can be placed from SW to
PGND to eliminate high frequency switch node ringing.
See the Applications Information section.
PGOOD (C7): Output Voltage Power Good Indicator. Open-
drain logic output that is pulled to ground when the output
voltage is not within ±10% of the regulation point.
V
OUT_LCL
(G9): This pin is connected to the top of the
internal top feedback resistor for the output. When the
remote sense amplifier is used, connect the remote sense
amplifier output DIFFOUT to V
OUT_LCL
to drive the 10k top
feedback resistor. When the remote sense amplifier is not
used, connect V
OUT_LCL
to V
OUT
directly.
FREQ (E3): Frequency Set Pin. A 10µA current is sourced
from this pin. A resistor from this pin to ground sets a
voltage, that in turn, programs the operating frequency.
Alternatively, this pin can be driven with a DC voltage that
can set the operating frequency. See the Applications In-
formation section. The LTM4649 has an internal resistor
to program frequency to 450kHz.
TRACK/SS (E5): Output Voltage Tracking Pin and Soft-
Start Inputs. The pin has a 1.2µA pull-up current source.
A capacitor from this pin to ground will set a soft-start
ramp rate. In tracking, the regulator output can be tracked
to a different voltage. The different voltage is applied to
a voltage divider then the slave output’s track pin. This
voltage divider is equal to the slave output’s feedback
divider for coincidental tracking. See the Applications
Information section.
FB (E7): The Negative Input of the Error Amplifier. Internally,
this pin is connected to V
OUT_LCL
with a 10k precision
resistor. Different output voltages can be programmed
with an additional resistor between V
FB
and ground pins.
In PolyPhase operation, tying the V
FB
pins together allows
for parallel operation. See the Applications Information
section for details.
RUN (F1): Run Control Pin. A voltage above 1.25V will
turn on the module. Each RUN pin has a 1µA pull-up cur-
rent, once the RUN pin reaches 1.2V an additional 4.5µA
pull-up current is added to this pin.
CLKOUT (F2): Output Clock Signal for PolyPhase Opera-
tion. The phase of CLKOUT is determined by the state of
the PHMODE pin.
INTV
CC
(F4): Internal 5V LDO for Driving the Control Cir-
cuitry and the Power MOSFET Drivers. The 5V LDO has
a 100mA current limit.
PACKAGE ROW AND COLUMN LABELING MAY VARY
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
LAYOUT CAREFULLY.