LTM4673 datasheet(28/132 Pages) AD

28 / 132 page

LTM4683

Rev. 0

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OPERATION

Fault reporting and shutdown behavior are fully con-

figurable. Four individual FAULT0, FAULT1, FAULT2,

and FAULT3, outputs are provided. Each FAULTn can be

masked independently.

Six dedicated pins for ALERT_01, ALERT_23, PGOOD0,

PGOOD1, PGOOD2, and PGOOD3 functions are provided.

The shutdown operation also allows all faults to be indi-

vidually masked and can be operated in either unlatched

(hiccup) or latched modes.

Individual status commands enable fault reporting over

the serial bus to identify the specific fault event. Fault or

warning detection includes the following:

Output Undervoltage/Overvoltage

Input Undervoltage/Overvoltage

Input and Output Overcurrent

Internal Overtemperature

Communication, Memory or Logic (CML) Fault

EEPROM WITH ECC

The LTM4683 contains internal EEPROM with error cor-

rection coding (ECC) to store user configuration set-

tings and fault log information for Channels 0 and 1 and

Channels 2 and 3. EEPROM endurance retention and

mass write operation time are specified in the Electrical

Characteristics and Absolute Maximum Ratings sections.

Write operations above TJ = 85°C are possible, although

the Electrical Characteristics are not guaranteed, and the

EEPROM will be degraded. Read operations performed at

temperatures between –40°C and 125°C will not degrade

the EEPROM. Writing to the EEPROM above 85°C will

result in degrading retention characteristics. The fault log-

ging function, which is useful in debugging system prob-

lems that may occur at high temperatures, only writes to

fault log EEPROM locations. If occasional writes to these

registers occur above 85°C, the slight degradation in the

data retention characteristics of the fault log will not take

away from the usefulness of the function.

It is recommended that the EEPROM not to be written

when the die temperature is greater than 85°C. If the die

temperature exceeds 130°C, the LTM4683 will disable all

EEPROM write operations. All EEPROM write operations

will be re-enabled when the die temperature drops below

125°C. (The controller will also disable all the switching

when the die temperature exceeds the internal overtem-

perature fault limit of 160°C with a 10°C hysteresis).

The degradation in EEPROM retention for temperatures

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

sionless acceleration factor using Equation 1.

= e

⎛

⎝⎜

⎞

⎠⎟

•

TUSE+273

–

TSTRESS+273

⎛

⎝⎜

⎞

⎠⎟

⎡

⎣

⎢

⎤

⎦

⎥

(1)

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 in °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 = e([(1.4/8.617 • 10

–5) • (1/398 – 1/403)] ) = 1.66

The equivalent operating time at 125°C = 16.6 hours.

Thus, the overall retention of the EEPROM was degraded

by 6.6 hours as a result of operating at a junction tempera-

ture of 130°C for 10 hours. The effect of the overstress is

negligible when compared to the overall EEPROM reten-

tion rating of 87,600 hours at a maximum junction tem-

perature of 125°C.

The integrity of the entire onboard EEPROM is checked with

a CRC calculation each time its data is to be read, such as

after a power-on reset or execution of a RESTORE_USER_

ALL command. If a CRC error occurs, the CML bit is set in

the STATUS_BYTE and STATUS_WORD commands, the

EEPROM CRC Error bit in the STATUS_MFR_SPECIFIC

command is set, and the ALERT and RUN pins pulled low

(PWM channels off). At that point, the device will only

respond at a special address 0x7C, which is activated

LTM4673 Datasheet(PDF) 28 Page - Analog Devices

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