LTM4677 datasheet(34/110 Pages) AD

34 / 110 page

LTC3888-1

Rev. 0

For more information www.analog.com

OPERATION

FACTORY DEFAULT OPERATION

The LTC3888-1 ships from the factory with a default con-

figuration stored in its non-volatile memory unless custom

programming has been requested. These command values

are loaded into volatile RAM when the chip is initialized. Prior

to receiving any PMBus commands, a stock LTC3888-1 will

operate in the factory default mode. If a STORE_USER_

ALL command is executed, the contents of the non-volatile

memory are replaced with active command values from

internal RAM, and that will permanently overwrite the fac-

tory defaults. Table 5 summarizes the default factory opera-

tion settings of the LTC3888-1 if all resistor configuration

pins are left open. These defaults allow parameters listed

in bold text in the table to be overridden with configuration

resistor programming. Warning limits are given in Table 5

because exceeding them will cause the ALERT pin to be

asserted even if the PMBus interface is not being utilized.

Table 5. Factory Default Operation Summary

PARAMETER*

DEFAULT SETTING

UNITS

PMBus Address

All writes enabled to Channel 0 at address 0x4F (no PEC).

–

Operation

OPERATION enabled with RUN pin control and soft-off.

–

Input Voltage OFF Threshold

6.0

Input Voltage UV Warning Limit

6.3

Input Voltage ON Threshold

6.5

Input Voltage OV Fault Limit

15.5

Input Voltage OV Fault Response

Latch off

–

Soft-Start Time

1.6 (with no delay)

Maximum Start-Up Time (TMAX)

TMAX Fault Response

Retry every 350ms

–

Output Voltage UV Fault Limit

–10% of nominal VOUT

–

Output Voltage UV Fault Response

Retry every 350ms

–

Output Voltage

Set by external R-divider (VFB = 400mV, VOUT servo disabled)

–

Output Voltage OV Fault Limit

10% of nominal VOUT

–

Output Voltage OV Fault Response

Latch off

–

Shut Down

1.6ms soft-off

–

Output Current Monitor Gain

5.0

mΩ

Output Current OC Warning/Fault Limits

20/29.75

Output Current OC Fault Response

Ignore

–

PWM Switching Frequency

500

kHz

Master/Slave Configuration

4+4 (or 8-phase)

–

Internal Overtemperature Warning/Fault Limits

130/160

°C

Internal Overtemperature Responses

Warning: EEPROM disabled; Fault: PWM disabled

–

External Overtemperature Warning/Fault Limits

85/100

°C

External Overtemperature Fault Response

Retry every 350ms

–

FAULT

Asserts low for the following faults: VOUT UV or OV, VIN OV, external or internal OT,

TON_MAX, or output short cycle

–

ALERT Masking

Masked for loss of PLL lock and external fault inputs

–

*Bold entries can be changed with external configuration resistors

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