L6711 datasheet(20/38 Pages) STMICROELECTRONICS

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L6711

20/38

obtaining the following relationship:

where RSENSE is the sensing element resistance value (at TMOS = 25ºC), B is the constant obtainable from

Figure 13, kT is the Temperature Coupling Coefficient between the sensing element and the Controller (it

results KT = (TJ-25)/(TMOS-25)) and

α is the Temperature Coefficient of the sensing element. Since RTC

depends from the constant B depending in turn from RTC, an iterative process is required to properly de-

sign the RTC value.

As a consequence of the nature of the thermal sensor, a negative offset is needed to compensate the na-

tive offset introduced by the ITS at a referenced temperature Tref and it is obtainable by connecting a

ROFFSET resistor between the OFFSET pin and SGND as follow:

To disable this function, short the pin to SGND.

Figure 13. Integrated Thermal Sensor Constant vs. External resistor RTC

DYNAMIC VID TRANSITION

The device is able to manage Dynamic VID Code changes that allow Output Voltage modification during

normal device operation.

OVP and UVP signals are masked during every VID transition and they are re-activated after the transition

finishes.

When changing dynamically the regulated voltage (D-VID), the system needs to charge or discharge the

output capacitor accordingly. This means that an extra-current ID-VID needs to be delivered, especially

when increasing the output regulated voltage and it must be considered when setting the over current

threshold. This current result:

where dVOUT is the selected DAC LSB (12.5mV for VRD10.x or 25mV for Hammer DAC) and TVID is the

time interval between each LSB transition.

SENSE α

MOS

–

()

⋅⋅

-------------------------------------------------------------------- I

OUT

----------- BT

–

()

⋅⋅

–

SENSE

----------------------

⋅

α I

OUT

⋅

---------------------

⋅

OFFSET

TC Tref

()

–

ref

–

()

⋅

----------------------------------------------

450

475

500

525

550

575

600

625

650

102030

40 50 60708090 100

1.50

1.60

1.70

1.80

1.90

2.00

10 20 30405060 70 80 90 100

A [mV] vs. RTC [K

Ω]

B [mV/°C] vs. RTC [K

Ω]

DVID

–

OUT dVOUT

⋅

VID

---------------------------------------

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