LTC2972 datasheet(20/112 Pages) LINER

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LTC2972

2972fa

For more information www.linear.com/LTC2972

OPERATION

• Record minimum and maximum input voltage, input

current, input power, output voltages, output currents

and output temperatures.

• Access user EEPROM data directly, without alter-

ing RAM space (Mfr_ee_unlock, Mfr_ee_erase, and

Mfr_ee_data).Facilitatesin-housebulkprogramming.

• Accommodate multiple hosts with Command Plus.

EEPROM

The LTC2972 contains internal EEPROM (Nonvolatile

Memory) with error-correcting-code (ECC) to store con-

figuration settings and fault log information. EEPROM

endurance, retention and mass write operation time are

specifiedovertheoperatingtemperaturerange.SeeElectri-

calCharacteristicsandAbsoluteMaximumRatingssections.

Non-destructive operation above TJ = 105°C is possible

although the Electrical Characteristics are not guaranteed

and the EEPROM will be degraded.

Operating the EEPROM above 105°C may result in a

degradation of retention characteristics. The fault logging

function, which is useful in debugging system problems

that may occur at high temperatures, only writes to fault

log EEPROM locations. If occasional writes to these

registers occur above 105°C, a slight degradation in the

data retention characteristics of the fault log may occur.

It is recommended that the EEPROM not be written using

STORE_USER_ALL or bulk programming when TJ>85°C.

The degradation in EEPROM retention for temperatures

>105°C can be approximated by calculating the dimen-

sionless acceleration factor using the following equation.

AF = e

⎛

⎝

⎜

⎞

⎠

⎟

⎟ •

TUSE +273

–

TSTRESS+273

⎛

⎝

⎜

⎜⎜

⎞

⎠

⎟

⎟⎟

⎡

⎣

⎢

⎤

⎦

⎥

where:

AF = acceleration factor

Ea = activation energy = 1.4eV

k = 8.617 • 10–5 eV/°K

TUSE = 105°C specified junction temperature

TSTRESS = actual junction temperature °C

Example: Calculate the effect on retention when operating

at a junction temperature of 125°C for 10 hours.

TSTRESS = 125°C

TUSE = 105°C

AF = 8.65

Equivalent operating time at 105°C = 86.5 hours.

So the overall retention of the EEPROM was degraded

by an additional 76.5 hours as a result of operation at a

junction temperature of 125°C for 10 hours. Note that the

effect of this overstress is negligible when compared to

the overall EEPROM retention rating of 175,200 hours at

a junction temperature of 105°C.

AUXFAULTB

The MFR_CONFIG2_LTC2972 and MFR_CONFIG3_

LTC2972 commands can be used on a per channel basis

to select which, if any, fault conditions will cause the

AUXFAULTB pin to be driven low. The only fault types

which can be propagated to the AUXFAULTB pin are over/

under voltage faults.

RESETB

Holding the WDI/RESETB pin low for more than tRESETB

will cause the LTC2972 to enter the power-on reset state.

While in the power-on reset state, the device will not

communicate on the I2C bus. Following the subsequent

rising-edge of the WDI/RESETB pin, the LTC2972 will

execute its power-on sequence per the user configuration

stored in EEPROM. Connect WDI/RESETB to VDD33 with

a 10k resistor. WDI/RESETB includes an internal 256µs

deglitch filter so additional filter capacitance on this pin

is not recommended.

VDDIO

The VDDIO pin defines the input threshold of the SDA, SCL,

ALERTB, PWRGD, FAULTB[1:0], CONTROL[1:0], PG[1:0],

WDI/RESETB,andWPpinstoallowforlowervoltagedigital

communication.AninternalresistivedividerattheVDDIOpin

setstheinternalthresholdvoltagetoapproximately45%of

the VDDIO pin voltage. The VOUT_EN[1:0], AUX_FAULTB,

and SHARE_CLK pins are not affected by the voltage at

the VDDIO pin and should always be pulled up to VDD33.

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