STPM098C datasheet(31/110 Pages) STMICROELECTRONICS

31 / 110 page

During normal operation the PWM pins driving is managed by the digital section of the loop controller which is in

charge of the TON and TOFF generation along with their minimum value limitations (MFR_T_MIN). In case of

fault event, the PWM pin driving is overridden by the diagnostic control which applies to the configured reaction

(as instance: 3Tclk turn-off then HIZ, cycle-by-cycle turn-off, etc.).

Since fault events are not synchronous with normal PWM generation and since reaction countermeasure shall be

applied within a specific fault tolerant time, it turns out that PWM driving by loop and by diagnostic controllers

cannot be synchronous as well and diagnostic shall have the highest priority.

In case of fault events requiring PWM turn-off or switch to HiZ, the MINIMUM ON/OFF time configured in

MFR_T_MIN cannot be guaranteed.

Figure 21. Minimum TON clipping during LTC fault reaction

Ton

MIN

Fault reaction time

Fault happens

PWM_DIG

PWMn

DIAG_DIS

3.4.2.3

Ignore faults

When a fault whose reaction is set as “ignore” is detected, the related PMBus™ flag is set to ‘1’. Logic performs

no corrective action. The PMBus™ flag can be cleared when all the following conditions are met in this sequence:

1. Fault is removed.

2. Clear mechanism - One of the following actions, required by application software:

–

VR_EN1/VR_EN2 is asserted low for at least T_clear and then asserted back high.

–

CLEAR_FAULTS command by PMBus™ (clears all faults).

–

Dedicated clear commands by PMBus™ (clears single fault).

Note:

•

VR1_EN toggling is used to clear specific fault affecting loop 1. VR2_EN toggling is used to clear specific

fault affecting loop 2. Generic faults affecting both loops can be cleared by toggling either VR1_EN or

VR2_EN.

•

Faults clearing through the PMBus™ command make use of paging for faults affecting the specific loop.

Generic faults affecting both loops can be cleared independently of the command page.

STPM098C

Functional description

DS14440 - Rev 1

page 31/110

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