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LTM4648

4648f

For more information www.linear.com/LTM4648

pin FuncTions

GND (A1-A5, A7-A11, B1, B9-B11, E1, F3, F5, G1-G7):

GroundPinsforBothInputandOutputReturns.Allground

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 INTVCC

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 INTVCC

to enable Burst Mode operation. Connect to ground to

enable forced continuous mode of operation. Floating this

pin will enable pulse-skipping mode of operation.

NC (B7-B8, C3-C4): No Connection Pins. Either float these

pins or connect them to GND for thermal purpose.

VIN (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 VIN pins and GND pins.

VOUT (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.

See Table 1.

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.

VOUT_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 in the LTM4648, connect

the remote sense amplifier output DIFFOUT to VOUT_LCL

to drive the 10k top feedback resistor. When the remote

sense amplifier is not used in the LTM4648, connect

VOUT_LCL to VOUT 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 LTM4648 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):TheNegativeInputoftheErrorAmplifier.Internally,

this pin is connected to VOUT_LCL with a 10k precision

resistor. Different output voltages can be programmed

with an additional resistor between VFB and ground pins.

In PolyPhase operation, tying the VFB pins together allows

for parallel operation. See the Applications Information

section for details.

RUN (F1): Run Control Pin. A voltage above 1.4V will turn

on the module. The RUN pin has a 1µA pull-up current,

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.

INTVCC (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.

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