LTM8021 datasheet(6/16 Pages) LINER

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LTM8021

8021fb

PIN FUNCTIONS

VIN (Bank 1): The VIN pin supplies current to the LTM8021’s

internal regulator and to the internal power switch. This

pin must be locally bypassed with an external, low ESR

capacitor of at least 1μF.

VOUT (Bank 2): Power Output Pins. An external capacitor is

connected from VOUT to GND in most applications. Apply

output load between these pins and GND pins.

BIAS (Pin H3): The BIAS pin connects to the internal

boost Schottky diode and to the internal regulator. Tie to

VOUT when VOUT > 3V or to another DC voltage greater

than 3V otherwise. When BIAS > 3V the internal circuitry

will be powered from this pin to improve efﬁciency. Main

regulator power will still come from VIN.

RUN/SS (Pin A1): Tie RUN/SS pin to ground to shut down

the LTM8021. Tie to 1.6V or more for normal operation.

If the shutdown feature is not used, tie this pin to the VIN

pin. The RUN/SS also provides soft-start and frequency

foldback. To use the soft-start function, connect a resis-

tor and capacitor to this pin. Do not allow the RUN/SS

pin to rise above VIN. See the Applications Information

section.

GND (Bank 3): The GND connections serve as the main

signal return and the primary heatsink for the LTM8021. Tie

the GND pins to a local ground plane below the LTM8021

and the circuit components. Return the feedback divider

to this signal.

ADJ (Pin A2): The LTM8021 regulates its ADJ pin

to 0.8V. Connect the adjust resistor from this pin to

ground. The value of RADJ is given by the equation,

RADJ = 80/(VOUT – 0.8), where RADJ is in k.

VIN

8021 BD

BIAS

CURRENT MODE

CONTROLLER

VOUT

10μF

15pF

10μH

0.1μF

RUN/SS

100k

ADJ

GND

BLOCK DIAGRAM

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