LTM2987 datasheet(22/114 Pages) AD

22 / 114 page

LTC2971

Rev. 0

For more information www.analog.com

OPERATION

• Prevent a DC/DC converter from re-entering the ON

state after a power cycle until a programmable interval

(MFR_RESTART_DELAY) has elapsed and its output

has decayed below a programmable threshold voltage

(MFR_VOUT_DISCHARGE_THRESHOLD).

• Read high side input current, input voltage, input

power, and accumulated input energy.

• 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 LTC2971 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.

Read operations performed between −40°C and 125°C

will not degrade the EEPROM. Write operations above

85°C are possible but will degrade retention characteris-

tics. It is recommended that the EEPROM not be written

above 85°C. 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 85°C,

theslightdegradationintheretentioncharacteristicsofthe

fault log will not take away the usefulness of the function.

The degradation in EEPROM retention for temperatures

>125°C can be approximated by calculating the dimen-

sionless acceleration factor using the following equation.

= e

⎛

⎝⎜

⎞

⎠⎟

•

TUSE+273

–

TSTRESS+273

⎛

⎝⎜

⎞

⎠⎟

⎡

⎣

⎢

⎤

⎦

⎥

where:

AF = acceleration factor

Ea = activation energy = 1.4eV

k = 8.617 • 10–5 eV/°K

TUSE = 125°C specified junction temperature

TSTRESS = actual junction temperature °C

Example: Calculate the effect on retention when operating

at a junction temperature of 130°C for 10 hours.

TSTRESS = 130°C

TUSE = 125°C

AF = 1.66

Equivalent operating time at 125°C = 16.6 hours.

So the overall retention of the EEPROM was degraded

by an additional 6.6 hours as a result of operation at a

junction temperature of 130°C for 10 hours. Note that the

effect of this overstress is negligible when compared to

the overall EEPROM retention rating of 87,600 hours at

a junction temperature of 125°C.

AUXFAULTB

The MFR_CONFIG2_LTC2971 and MFR_CONFIG3_

LTC2971 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 LTC2971 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 LTC2971 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.

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