LTM4682 datasheet(42/130 Pages) AD

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LTM4682

Rev. A

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OPERATION

Output Undervoltage Response

The response to an undervoltage comparator output can

be the following:

Ignore

Shut Down Immediately—Latch Off

Shut Down Immediately—Retry Indefinitely at the Time

Interval Specified in MFR_RETRY_DELAY.

The UV responses can be deglitched. See Table 18.

Peak Output Overcurrent Fault Response

Due to the current mode control algorithm, peak output cur-

rent across the inductor is always limited on a cycle-by-cycle

basis. The value of the peak current limit is specified in the

Electrical Characteristics table. The current limit circuit oper-

ates by limiting the COMPn maximum voltage. Since internal

DCR sensing is used, the COMPn maximum voltage has a

temperature dependency directly proportional to the TC of

the DCR of the inductor. The LTM4682 automatically monitors

the external temperature sensors and modifies the maximum

allowed COMPn to compensate for this term. The IOUT_OC_

FAULT_LIMIT section provides data points for IOUT Limiting,

see IOUT_OC_FAULT_LIMIT.

The overcurrent fault processing circuitry can execute the

following behaviors.

Current Limit Indefinitely

Shut Down Immediately—Latch Off

Shut Down Immediately—Retry Indefinitely at the Time

Interval Specified in MFR_RETRY_DELAY.

The overcurrent responses can be deglitched in incre-

ments of (0-7) • 16ms. See Table 19.

RESPONSES TO TIMING FAULTS

TON_MAX_FAULT_LIMIT is the time allowed for VOUT

to rise and settle at start-up. The TON_MAX_FAULT_

LIMIT condition is predicated upon detecting the

VOUT_UV_FAULT_LIMIT as the output is undergoing a

SOFT_START sequence. The TON_MAX_FAULT_LIMIT

time is started after TON_DELAY has been reached and

a SOFT_START sequence is started. The resolution of

the TON_MAX_FAULT_LIMIT is 10µs. If the VOUT_

UV_FAULT_LIMIT is not reached within the TON_MAX_

FAULT_LIMIT time, the response of this fault is determined

by the value of the TON_MAX_FAULT_RESPONSE com-

mand value. This response may be one of the following.

Ignore

Shut Down (Stop Switching) Immediately—Latch Off

Shut Down Immediately—Retry Indefinitely at the Time

Interval Specified in MFR_RETRY_DELAY.

This fault response is not deglitched. A value of 0 in

TON_MAX_FAULT_LIMIT means the fault is ignored.

The TON_MAX_FAULT_LIMIT should be set longer than

the TON_RISE time. It is recommended that TON_MAX_

FAULT_LIMIT always be set to a non-zero value, other-

wise the output may never come up, and no flag will be

set to the user. See Table 21.

RESPONSES TO VIN OV FAULTS

VIN overvoltage is measured with the ADC. The response

is naturally deglitched by the 100ms typical response time

of the ADC. The fault responses include the following.

Ignore

Shut Down Immediately—Latch Off

Shut Down Immediately—Retry Indefinitely at the

Time Interval Specified in MFR_RETRY_DELAY. See

Table 21.

RESPONSES TO OT/UT FAULTS

Internal Overtemperature Fault Response

An internal temperature sensor protects against NVM dam-

age. Above 85°C, no writes to NVM are recommended.

Above 130°C, the internal overtemperature warns thresh-

old is exceeded and the part disables the NVM, and does

not re-enable until the temperature has dropped to 125°C.

When the die temperature exceeds 160°C, the internal

temperature fault response is enabled, and the PWM is

disabled until the die temperature drops below 150°C.

Temperature is measured by the ADC. Internal tempera-

ture faults cannot be ignored. Internal temperature limits

cannot be adjusted by the user. See Table 20.

LTM4682 Datasheet(PDF) 42 Page - Analog Devices

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