LT8613 datasheet(10/26 Pages) LINER

10 / 26 page

LT8619/LT8619-5

8619f

For more information www.linear.com/LT8619

PIN FUNCTIONS

NC (Pin 1, 3, 13, MSOP Only): No Connect. These pins

are not connected to the internal circuitry.

VIN (Pin 1/Pin 2): The VIN pin supplies current to the

LT8619 internal circuitry and to the internal topside power

switch. Be sure to place the positive terminal of the input

bypass capacitor as close as possible to the VIN pin, and

the negative capacitor terminal as close as possible to

the GND pin.

EN/UV (Pin 2/Pin 4): The LT8619 is shut down when this

pin is low and active when this pin is high. The EN/UV pin

power-on threshold is 1V. When forced below 0.56V, the

IC is put into a low current shutdown mode. Tie to VIN if

shutdown feature is not used. An external resistor divider

from VIN can be used to program the VIN UVLO.

RT (Pin 3/Pin 5): A resistor is tied between RT and ground

to set the switching frequency. When synchronizing, the

RT resistor should be chosen to set the LT8619 switch-

ing frequency equal to or below the synchronization fre-

quency. Do not apply external voltage to this pin.

PG (Pin 4/Pin 6): Open-Drain Power Good Output. PG

remains low until the FB pin is within ±7.5% of the final

regulation voltage. The PG pull-up resistor can be con-

nected to the INTVCC, VOUT or an external supply voltage

that is lower than 6V.

SYNC (Pin 5/Pin 7): External Clock Synchronization Input.

Tie to a clock source for synchronization to an external

frequency. During clock synchronization, the controller

enters forced continuous mode. Ground the SYNC pin for

Burst Mode operation. Connect to INTVCC to enable forced

continuous mode operation. Floating this pin will enable

pulse-skipping mode operation. During start-up, the con-

troller is forced to run in pulse-skipping mode. When in

pulse-skipping or forced continuous mode operation, the

IQ will be much higher compared to Burst Mode operation.

FB (Pin 6/Pin 9, 10, LT8619 Only): The LT8619 regulates

the FB pin to 0.8V. Connect the feedback resistor divider

tap to this pin. Also, connect a phase lead capacitor

between FB and VOUT. Typically, this capacitor is between

4.7pF to 10pF. Do not apply an external voltage to this pin.

OUT (Pin 9, 10, LT8619-5 MSOP Only): Connect to the

regulator output VOUT. The LT8619-5 regulates the OUT

pin to 5V. This pin connects to the internal 10MΩ feed-

back divider that programs the fixed output voltage.

BIAS (Pin 7/Pin 11): The internal regulator will draw cur-

rent from BIAS instead of VIN when the BIAS pin is tied

to a voltage higher than 3.1V. For switching regulator

output voltages of 3.3V and above, this pin should be tied

to VOUT. If this pin is tied to a supply other than VOUT, use

a 1μF local bypass capacitor on this pin.

INTVCC (Pin 8/Pin 12): Internal 3.3V Regulator Output.

The internal power drivers and control circuits are pow-

ered from this voltage. INTVCC maximum output current

is 20mA. INTVCC current will be supplied from BIAS if

VBIAS > 3.1V, otherwise current will be drawn from VIN.

Voltage on INTVCC will vary between 2.8V and 3.3V when

VBIAS is between 3.0V and 3.5V. Decouple this pin to GND

with at least a 1μF low ESR ceramic capacitor. Do not load

the INTVCC pin with external circuitry.

BST (Pin 9/Pin 14): 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.

SW (Pin 10/Pin 15, 16): 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.

GND (Exposed Pad Pin 11/Pin 8, Exposed Pad Pin 17):

Ground. The exposed pad must be connected to the nega-

tive terminal of the input capacitor and soldered to the

PCB in order to lower the thermal resistance.

(DFN/MSOP)

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