LT8601 datasheet(10/26 Pages) LINER

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LT8601

8601fa

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pin FuncTions

BIAS (Pin 10): Power to the Internal Regulator. Connect

to an output ≥ 3.2V when available. Decouple to ground

with a low ESR capacitor.

BST1, BST2 (Pins 4, 5): Boost Voltage for High Voltage

Channels. The Boost Voltage provides a drive voltage

higher than PVIN to the gate of the NMOS top switch.

CPOR (Pin 31): Power-On Reset Timer. Connect a capaci-

tor from this pin to ground to program the power-on reset

timer. CPOR has a 2μA (typical) pull-up current.

EN/UVLO (Pin 22): Enable/Undervoltage Lockout Input.

The LT8601 is in low power shutdown when this pin is

≤ 0.4V. A precision threshold at 1.20V (rising) enables

the switching regulator’s output switching stages. This

allows the EN/UVLO pin to be used as an input undervolt-

age lockout by connecting to a resistor divider between

VIN and GND. When the EN/UVLO voltage is between 0.4V

and 1.2V, the LT8601 input current will depend on the

mode selected, the VIN voltage, and the EN/UVLO voltage.

Connect this pin to VIN if the UVLO function is not needed.

FB1, FB2 (Pins 26, 25): Feedback Input Pins for the High

Voltage Converters. The converters regulate the corre-

sponding feedback pin to the lesser of 1V or the voltage

on the associated TRKSS pin.

FB3 (Pin 24): Feedback Input Pin for the Low Voltage

Converter. The converter regulates the corresponding

feedback pin to 800mV.

GND (Pins 2, 8, 9, 13, 16, 27, 30, 34, 35, 38, 40, 41):

Ground. These pins must be soldered to PCB ground.

The exposed pad must also be soldered to PCB ground.

INTVCC (Pin 28): Internal Regulator Bypass. Do not load

the INTVCC pin with external circuitry. INTVCC is 3.1V

when BIAS < 3.1V, 3.4V when BIAS > 3.4V, and approxi-

mately equal to BIAS when BIAS is between 3.1V and

3.4V. Decouple to ground with a low ESR, 4.7μF capacitor.

PG1, PG2 (Pins 1, 11): Power Good Indicators for Channels

1 and 2. Open-drain logic output pulls down until the corre-

sponding FB pin rises above 0.92V but remains below 1.08V.

PG3 (Pin 12): Power Good Indicator for Channel 3. Open-

drain logic output pulls down until the corresponding FB

pin rises above 0.736V but remains below 0.864V.

POREN (Pin 39): Power-On Reset Enable. This is a logic

input that starts the ramp on the POR timing capacitor.

PVIN1, PVIN2 (Pins 37, 14): Input Supply Voltage to High

Voltage Channels 1 and 2, respectively. These pins are

independent and can be powered from different sources

if necessary. Bypass each input with a low ESR capacitor

to the adjacent GND pin.

PVIN3 (Pin 17): Input Supply Voltage to Low Voltage

Channel 3. This pin is typically connected to one of the

high voltage converter outputs and should be locally

bypassed with a low ESR capacitor.

RST (Pin 32): Power-On Reset Output. CMOS output with

weak pull-up, this pin is held low until the POR times out.

RT (Pin 29): Frequency Programming Resistor. Connect

a resistor from this pin to ground to set the internal oscil-

lator frequency.

RUN3 (Pin 18): Run Input for the Low Voltage Converter.

Channel 3 is enabled when the voltage on this pin exceeds

0.72V (typical).

SW1 (Pin 3): Channel 1 Switch Node. This is the output

of the internal power switches for channel 1.

SW2 (Pins 6, 7): Channel 2 Switch Node. This is the out-

put of the internal power switches for channel 2. These

pins must be connected together.

SW3 (Pin 15): Channel 3 Switch Node. This is the output

of the internal power switches for channel 3.

SYNC (Pin 33): Clock Synchronization and Mode Select

Input. Connect this pin to ground to enable low ripple

Burst Mode operation. Connect this pin to INTVCC to

enable pulse skip operation. Apply a digital clock input to

synchronize the LT8601 switching frequency to a refer-

ence clock. When an external clock is applied, the LT8601

will operate in pulse-skipping mode.

TRKSS1, TRKSS2 (Pins 21, 20): Track/Soft-Start Inputs

for the High Voltage Converters. When this pin is below

1V, the converter regulates the FB pin to the TRKSS volt-

age instead of the internal reference. The TRKSS pin has

a 2.4μA (typical) pull-up current.

VIN (Pin 23): Input Supply Voltage to Internal Functions.

This pin is independent from any PVIN pin and can be

powered from different sources if necessary. VIN must

be above 3V for the part to operate.

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