MAX6876 datasheet(13/39 Pages) MAXIM

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EEPROM-Programmable, Quad,

Power-Supply Tracker/Sequencer Circuit

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Pin Description (continued)

NAME

FUNCTION

GATE2

Gate Drive for External n-Channel FETs. GATE2 begins enhancing the external n-channel FETs when

all monitored inputs are within their selected thresholds (0.5V to 5.5V), at least one IN_ input or VCC is

above the minimum operating voltage, VTRKEN > 1.285V threshold, and the ENABLE input is logic

high. During power-up mode, GATE_ voltages are enhanced with internal control loops forcing all

OUT_ voltages to track the reference ramp (SYNCH) at a programmed slew rate. An internal charge

pump boosts GATE2 to VIN2 + 5V to fully enhance the external n-channel FET when power-up is

complete.

IN2

Supply Voltage and Tracked Input Voltage. Nominal supply range is 0.5V to 5V. IN1, IN2, IN3, IN4, or

VCC must be greater than the internal UVLO (VABP = 2.7V) to enable the tracking functionality. IN2 is

monitored with internally selected thresholds to ensure all supplies have stabilized before tracking (or

sequencing) is enabled.

OUT1

Monitored Output Voltage. Each OUT1 is monitored to control the supply slew rate and tracking

performance. OUT1–OUT4 begin to track up after the internal supply (ABP) exceeds the minimum

voltage requirements, VTRKEN > 1.285V threshold, ENABLE is logic high, and IN1–IN4 are all within

their selected thresholds. The OUT1 output falls out of the tracking equation as OUT1 approaches

IN1; other OUT_ supplies continue tracking up without signaling a system fault. OUT_ outputs are

tracked down during power-off conditions.

GATE1

Gate Drive for External n-Channel FETs. GATE1 begins enhancing the external n-channel FETs when

all monitored inputs are within their selected thresholds (0.5V to 5.5V), at least one IN_ input or VCC is

above the minimum operating voltage, VTRKEN > 1.285V threshold, and the ENABLE input is logic

high. During power-up mode, GATE_ voltages are enhanced with internal control loops forcing all

OUT_ voltages to track the reference ramp (SYNCH) at a programmed slew rate. An internal charge

pump boosts GATE1 to VIN1 + 5V to fully enhance the external n-channel FET when power-up is

complete.

IN1

Supply Voltage and Tracked Input Voltage. Nominal supply range is 0.5V to 5V. IN1, IN2, IN3, IN4, or

VCC must be greater than the internal UVLO (VABP = 2.7V) to enable the tracking functionality. IN1 is

monitored with internally selected thresholds to ensure all supplies have stabilized before tracking (or

sequencing) is enabled.

—

Exposed Paddle. Exposed paddle is internally connected to GND.

Detailed Description

The MAX6876 EEPROM-configurable, multivoltage

power tracker/supervisor monitors four system voltages

and ensures proper power-up and power-down condi-

tions for systems requiring voltage tracking and/or

sequencing. The MAX6876 provides a highly config-

urable solution as key thresholds and timing parame-

ters are programmed through an I2C interface and

these values are stored in internal EEPROM. In addition

to tracking and sequencing voltages, the MAX6876

also provides supervisory functions as well as an over-

current detection circuit.

The MAX6876 features programmable undervoltage

and overvoltage thresholds for each input supply. The

thresholds are EEPROM configured in 10mV (0.5V to

3.05V) or 20mV (1.0V to 5.5V) increments. When all of

the voltages are within their specifications, the device

turns on the external n-channel MOSFETs to either

sequence or track the voltages to the system. All of the

voltages can be sequenced or tracked or powered up

with a combination of the two options. During voltage

tracking, the voltage at the GATE of each MOSFET is

increased to slowly turn on each OUT_. The GATE

delay is EEPROM-selectable from 25µs to 1.6s. The

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