L6751C datasheet(52/57 Pages) STMICROELECTRONICS

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PMBus support (preliminary)

L6751C

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DocID025037 Rev 1

12.3

Input voltage monitoring (READ_VIN)

The dedicated PMBus command allows the user to monitor input voltage. By connecting the

VIN pin to the input voltage with the recommended resistor values, the L6751C returns the

value of the input voltage measured as a voltage (linear format, N = -4).

The divider needs to be programmed to have 1.24 V on the pin when VIN = 15.9375 V.

According to this, RUP = 118.5 k and RDOWN = 10 k.

Errors in defining the divider lead to monitoring errors accordingly.

Filter VIN pin locally to GND to increase stability of the voltage being measured.

12.4

Duty cycle monitoring (READ_DUTY)

The dedicated PMBus command allows the user to monitor duty cycle for multi-phase with

the aim of calculating input current inexpensively (no need for input current-sense resistors).

By connecting the PHASE pin to the phase1 PHASE pin, the L6751C returns the value of

the duty cycle as a percentage (linear format, N = -2).

The divider needs to be programmed to respect absolute maximum ratings for the pin

(7 Vmax). According to this, RUP = 5.6 k and RDOWN = 470 .

12.5

Output voltage monitoring (READ_VOUT)

The dedicated PMBus command allows the user to monitor output voltage for both sections.

The L6751C returns the value of the programmed VID in VID LSBs (i.e. number of LSBs.

C8h = 200 dec x 5 mV = 1.000 V).

12.6

Output current monitoring (READ_IOUT)

The dedicated PMBus command allows the user to monitor output current for both sections.

The L6751C returns the value of the delivered current by reading IMON voltage (same as

VR12 register 15h) in amperes (linear format, N = 0).

12.7

Temperature monitoring (READ_TEMPERATURE)

The dedicated PMBus command allows the user to monitor the temperature of the power

section for multi-phase. The L6751C returns the value of the temperature sensed by NTC

connected on the TM/STM pin (the same as VR12 temperature zone) in degrees Celsius

(linear format, N = 0).

12.8

Overvoltage threshold setting

The dedicated MFR_SPECIFIC command allows the user to program specific thresholds for

multi-phase and single-phase sections.

The threshold can be programmed according to Table 17. Different thresholds can be

configured for multi-phase and single-phase sections.

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