LTM4613 datasheet(14/30 Pages) LINER

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LTM8003

8003fc

For more information www.linear.com/LTM8003

PIN FUNCTIONS

GND(Bank1,A1,A6):TietheseGNDpinstoalocalground

plane below the LTM8003 and the circuit components.

In most applications, the bulk of the heat flow out of the

LTM8003 is through these pads, so the printed circuit

design has a large impact on the thermal performance of

the part. See the PCB Layout and Thermal Considerations

sections for more details.

VIN (Bank 2): VIN supplies current to the LTM8003’s in-

ternal regulator and to the internal power switch. These

pins must be locally bypassed with an external, low ESR

capacitor; see Table 1 for recommended values.

VOUT (Bank 3): Power Output Pins. Apply the output filter

capacitor and the output load between these pins and

GND pins.

BIAS (Pins G1, G2): The BIAS pin connects to the internal

power bus. Connect to a power source greater than 3.2V

and less than 18V. If VOUT is greater than 3.2V, connect

this pin there. If the output voltage is less, connect this to a

voltage source above 3.2V. Decouple this pin with at least

1µF if the voltage source for BIAS is remote. If unused or

generating a negative output, tie BIAS to LTM8003 GND.

RUN (Pins B5, B6): Pull the RUN pin below 0.9V to shut

down the LTM8003. Tie to 1.06V or more for normal

operation. If the shutdown feature is not used, tie this

pin to the VIN pin.

RT (Pins A4, A5): The RT pin is used to program the

switchingfrequencyoftheLTM8003byconnectingaresis-

tor from this pin to ground. The Applications Information

section of the data sheet includes a table to determine the

resistancevaluebasedonthedesiredswitchingfrequency.

Minimize capacitance at this pin. Do not drive this pin.

SYNC (Pins A2, B2): External clock synchronization input

and operational mode. This pin programs four different

operating modes:

1. Burst Mode®. Tie this pin to ground for Burst Mode

operationatlowoutputloads—thiswillresultinultralow

quiescent current.

2. Pulse-skipping mode. Float this pin for pulse-skipping

mode. This mode offers full frequency operation down

to low output loads before pulse skipping occurs.

3. Spread spectrum mode. Tie this pin high (between

2.9V and 4.2V) for pulse-skipping mode with spread

spectrum modulation.

4. Synchronizationmode.Drivethispinwithaclocksource

tosynchronizetoanexternalfrequency.Duringsynchro-

nization the part will operate in pulse-skipping mode.

PG (Pin B1, C1): The PG pin is the open-collector output

of an internal comparator. PG remains low until the FB

pin voltage is within about 10% of the final regulation

CISPR25 Class 5 Peak Radiated

DC2416A Demo Board, VOUT = 5V

Spread Spectrum Enabled

CISPR25 Class 5 Average Radiated

DC2416A Demo Board, VOUT = 5V

Spread Spectrum Enabled

fSW = 2MHz

IOUT = 3.5A

FREQUENCY (MHz)

200

400

600

800

1000

–10

8053 G91

VERTICAL POLARIZATION

fSW = 2MHz

IOUT = 3.5A

FREQUENCY (MHz)

200

400

600

800

1000

–10

8053 G92

TYPICAL PERFORMANCE CHARACTERISTICS T

A = 25°C, unless otherwise noted.

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