L6759D datasheet(46/51 Pages) STMICROELECTRONICS

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PMBus support

L6759D

46/51

Doc ID 023240 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 recommended resistor values, the L6759D 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 kΩ and RDOWN=10 kΩ.

Errors in defining the divider lead to monitoring errors accordingly.

Filter the 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 L6759D 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 kΩ and RDOWN=470 Ω.

12.5

Output voltage monitoring (READ_VOUT)

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

sections. The L6759D 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 the output current for the multi-

phase section. The L6759D 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 L6759D returns the value of the temperature sensed by NTC

connected on the TM pin (the same as VR12 temperature zone) in celsius degrees (linear

format, N=0).

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