L9960T datasheet(69/95 Pages) STMICROELECTRONICS

69 / 95 page

DS11115 Rev 10

69/95

L9960, L9960T

Functional description

4.8.5

Diagnostic of "Open Load" in on-state

The diagnostic of the Open Load in on-state is possible as long as, at least, one

freewheeling cycle (meaning PWM = 0) is done through the body diode of the low-side

transistor meaning "passive freewheeling". The diagnostics is consequently available in

PWM/DIR and IN1/IN2 mode when the recirculation is performed through LS drivers.

After OL diagnostics activation, to update the OL status register it is needed that a time

Tstable_on is expired.

This is allowed by setting the bit OL_ON = “1” each time the open-load diagnostic is

requested:

Note:

(-) available in the D9 bit position in SPI command frame 6.

After the first PWM ='0' cycle the active HS is turned-off and a passive recirculation phase is

present to avoid shoot-through before enabling the ls driver and perform the OL diagnostics

after T_stable_on.

The voltage of the low-side transistor drain is monitored to track a recirculation current

(drain voltage below ground in case of current recirculation).

Note:

(-) available in the R1,R0 in SPI answer frame 8b.

In case OL_ON bit = “0” (Diag function disabled), the OL_ON_STATUS=[00].

Note:

if several diagnostics are performed between two SPI reads, the open-load diagnostic bits

can only be overwritten if the new diagnostic has a higher priority than the one already

stored in the register.

After the OL fault disappears there is no need to perform any action on DIS or PWM in order

to come back to Normal mode (bridge directly switch to Normal operating).

Table 81. OL_ON

Bit config

Description

Condition

Open Load in on-state disabled

Reset value

Open Load in on-state enabled

Table 82. OL_ON_STATUS [1:0]

Bit status

Description

Priority

Condition

OL disabled

No diag done

Low

Default value

OL / Diag done

High

No OL / Diag done

Medium

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