LT8607 datasheet(9/24 Pages) AD

9 / 24 page

LT8607/LT8607B

Rev. D

For more information www.analog.com

PIN FUNCTIONS

BST: This pin is used to provide a drive voltage, higher

than the input voltage, to the topside power switch. Place

a 0.1µF boost capacitor as close as possible to the IC. Do

not place a resistor in series with this pin.

SW: The SW pin is the output of the internal power

switches. Connect this pin to the inductor and boost

capacitor. This node should be kept small on the PCB for

good performance.

INTVCC: Internal 3.5V Regulator Bypass Pin. The internal

power drivers and control circuits are powered from this

voltage. INTVCC max output current is 20mA. Voltage on

INTVCC will vary between 2.8V and 3.5V. Decouple this

pin to power ground with at least a 1µF low ESR ceramic

capacitor. Do not load the INTVCC pin with external circuitry.

RT: A resistor is tied between RT and ground to set the

switching frequency. When synchronizing, the RT resistor

should be chosen to set the LT8607 switching frequency

to equal or below the lowest synchronization input.

SYNC (MSOP Only): External Clock Synchronization

Input. Ground this pin for low ripple Burst Mode operation

at low output loads. Tie to a clock source for synchroni-

zation to an external frequency. Leave floating for pulse-

skipping mode with no spread spectrum modulation. Tie

to INTVCC or tie to a voltage between 3.2V and 5.0V for

pulse-skipping mode with spread spectrum modulation.

When in pulse-skipping mode, the IQ regulating no load

will increase to several mA. There is no SYNC pin on

the LT8607 DFN package. The LT8607 DFN internally

ties SYNC to ground. The LT8607B package internally

floats SYNC.

FB (LT8607/LT8607B Only): The LT8607 regulates the

FB pin to 0.778V. Connect the feedback resistor divider

tap to this pin.

VOUT (LT8607-5 Only): The LT8607-5 regulates the VOUT

pin to 5V. This pin connects to a 6.6MΩ internal divider.

TR/SS (MSOP Only): Output Tracking and Soft-Start Pin.

This pin allows user control of output voltage ramp rate

during start-up. A TR/SS voltage below 0.778V forces the

LT8607 to regulate the FB pin to equal the TR/SS pin volt-

age. The LT8607-5 will track the TR/SS pin voltage based

on a factor set by the internal resistor divider. The part

will track to 6.43 times the TR/SS voltage. When TR/SS

is above 0.778V, the tracking function is disabled and the

internal reference resumes control of the error amplifier.

An internal 2µA pull-up current from INTVCC on this pin

allows a capacitor to program output voltage slew rate.

This pin is pulled to ground with a 300Ω MOSFET dur-

ing shutdown and fault conditions; use a series resistor

if driving from a low impedance output. There is no TR/

SS pin on the LT8607 or LT8607B DFN and the node is

internally floated.

PG: The PG pin is the open-drain output of an internal

comparator. PG remains low until the FB pin is within

±8.5% of the final regulation voltage, and there are no

fault conditions. PG is valid when VIN is above 3.2V and

when EN/UV is high. PG is pulled low when VIN is above

3.2V and EN/UV is low. If VIN is near zero, PG will be high

impedance.

VIN: The VIN pin supplies current to the LT8607 internal

circuitry and to the internal topside power switch. This pin

must be locally bypassed. Be sure to place the positive

terminal of the input capacitor as close as possible to the

VIN pins, and the negative capacitor terminal as close as

possible to the GND pins.

EN/UV: The LT8607 is shut down when this pin is low and

active when this pin is high. The hysteretic threshold volt-

age is 1.05V going up and 1.00V going down. Tie to VIN

if the shutdown feature is not used. An external resistor

divider from VIN can be used to program a VIN threshold

below which the LT8607 will shut down.

GND: Exposed Pad Pin. The exposed pad must be con-

nected to the negative terminal of the input capaci-

tor and soldered to the PCB in order to lower the

thermal resistance.

LT8607 датащи(PDF) 9 Page - Analog Devices

LT8607 датащи(HTML) 9 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

датащи скачать

ссылки URL