LTM4677 datasheet(28/116 Pages) AD

28 / 116 page

LTC3883/LTC3883-1

Rev. F

For more information www.analog.com

OPERATION

external temperature sensors and modifies the maximum

allowed ITH to compensate for this term.

The overcurrent fault processing circuitry can execute the

following behaviors:

Current Limit Indefinitely

Shut Down Immediately—Latch Off

ShutDownImmediately—RetryIndefinitelyattheTime

Interval Specified in MFR_RETRY_DELAY

Theovercurrentresponsescanbedeglitchedinincrements

of (0-7) • 16ms. See Table 7

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 detection of 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 command value. This

response may be one of the following:

Ignore

Shut Down (Stop Switching) Immediately—Latch Off

ShutDownImmediately—RetryIndefinitelyattheTime

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 TON_MAX_FAULT_

LIMIT always be set to a non-zero value, otherwise the

outputmaynevercomeupandnoflagwillbesettotheuser.

See Table 9.

RESPONSES TO VIN OV FAULTS

VINovervoltageismeasuredwiththeMUX’dADC;therefore,

the response is naturally deglitched by the 80ms typical

response time of the ADC. The fault responses are:

Ignore

Shut Down Immediately—Latch Off

ShutDownImmediately—RetryIndefinitelyattheTime

Interval Specified in MFR_RETRY_DELAY

See Table 9.

RESPONSES TO OT/UT FAULTS

Overtemperature Fault Response—Internal

An internal temperature sensor protects against NVM

damage.Above85°C,nowritestoNVMarerecommended.

Above 130°C, the part disables the NVM and does not re-

enableuntiltheinternaltemperaturehasdroppedto125°C.

The LTC3883 sets bit 7 of the STATUS_TEMPERATURE

command (‘OT Warn’) above 130°C, and this bit cannot

be cleared until the internal temperature has dropped to

125°C. Above 160°C, the LTC3883 disables the PWM and

does not re-enable the PWM until the internal temperature

has dropped to 150°C. The part sets bit 6 of the STATUS_

TEMPERATURE command (‘OT Fault’) above 160°C, and

thisbitcannotbecleareduntiltheinternaltemperaturehas

dropped to 150°C. Temperature is measured by the ADC.

Internal temperature faults cannot be ignored. Internal

temperature limits cannot be adjusted by the user.

See Table 9.

Overtemperature and Undertemperature

Fault Response—Externals

An external temperature sensors can be used to sense

critical circuit elements like the inductor and power

MOSFETs. The OT_FAULT_RESPONSE and UT_FAULT_

RESPOSE commands are used to determine the appropri-

ateresponsetoanovertemperatureandundertemperature

condition,respectively.Ifnoexternalsenseelementisused

(not recommended) set the UT_FAULT_RESPONSE to

ignore and set the UT_FAULT_LIMIT to –275°C.

LTM4677 Datasheet(PDF) 28 Page - Analog Devices

LTM4677 Datasheet(HTML) 28 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL