LTM8003 datasheet(10/26 Pages) LINER

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LTM8073

8073fa

For more information www.linear.com/LTM8073

Typical perForMance characTerisTics

CISPR22 Class B Radiated

DC2389A Demo Board, VOUT = 5V

No Filter (FB1 Short, C8, C9 Open)

CISPR22 Class B Radiated

DC2389A Demo Board, VOUT = 5V

No Filter (FB1 Short, C8, C9 Open)

TA = 25°C, unless otherwise noted.

fSW = 1.2MHz, VIN = 28V, IOUT = 3.5A

CLASS B LIMIT

HORIZONTAL

VERTICAL

FREQUENCY (MHz)

200

400

600

800

1000

–10

8073 G55

fSW = 1.2MHz, VIN = 14V, IOUT = 3.5A

CLASS B LIMIT

HORIZONTAL

VERTICAL

FREQUENCY (MHz)

200

400

600

800

1000

–10

8073 G56

pin FuncTions

GND (Bank 1, A1, A6, B3): Tie these GND pins to a

local ground plane below the LTM8073 and the circuit

components. In most applications, the bulk of the heat

flow out of the LTM8073 is through these pads, so the

printed circuit design has a large impact on the ther-

mal performance of the part. See the PCB Layout and

Thermal Considerations sections for more details.

VIN (Bank 2): VIN supplies current to the LTM8073’s

internal 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 (Pin A2): The BIAS pin connects to the internal

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

If VOUT is greater than 3.2V, connect this pin to AUX.

Decouple this pin with at least 1µF if the voltage source

for BIAS is remote.

PG (Pin A3): The PG pin is the open-collector output

of an internal comparator. PG remains low until the FB

pin voltage is between 0.73V and 0.88V typical. The PG

signal is valid when VIN is above 3.4V. If VIN is above

3.4V and RUN is low, PG will drive low. If this function

is not used, leave this pin floating.

SHARE (Pin A4): Tie this to the SHARE pin of another

LTM8073 to load share. Otherwise leave floating. Do not

drive this pin.

RT (Pin A5): The RT pin is used to program the switching

frequency of the LTM8073 by connecting a resistor from

this pin to ground. The Applications Information section

of the data sheet includes a table to determine the resis-

tance value based on the desired switching frequency.

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

FB (Pin B1): The LTM8073 regulates its FB pin to 0.8V.

Connect the adjust resistor from this pin to ground. The

value of RFB is given by the equation RFB = 199.7/(VOUT

– 0.8), where RFB is in kΩ.

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