L9960 datasheet(66/95 Pages) STMICROELECTRONICS

66 / 95 page

Functional description

L9960, L9960T

66/95

DS11115 Rev 10

Figure 28. Example of NO Overcurrent detection by Tdiag2

The way to define the validity of the diagnostic is based on a programmable time called

"Tdiag1" and the fixed time “Tdiag2”. As soon as an activation command is set (PWM edge

or IN1!=IN2), the timing "Tdiag1" starts.

Tdiag1 is defined as the maximum programmable time in which it is expected that the

current reaches the current limitation threshold for a valid detection. Tdiag2 starts

automatically when Ion_th is overcome and depends on the conditions on Vps (pls refer to

Vps_norm thresholds on Table 63). Both are digital filters and guaranteed through scan.

Depending on the load current profile the two filters could be overlapped or as worst case,

sequential.

Here below it is explained the diagnostics result, with respect to Iload and Tdiag1 and Tdiag2:



If the current reaches the over-current threshold "OC_hs(ls)" for a duration "Toc_hs

(ls)" during diagnostics (Tdiag1, Tdiag2), the failure is detected and the bits "OCxx1:0"

are set to "00", which means "OVER-CURRENT ".



If the current is above I_lim_H and below the over-current threshold "OC_hs(ls)" and

the duration above Ion_threshold is shorter than “Tdiag2”, then "OCxx1:0" are set to

"10" which means "NO OVER-CURRENT".



If the current is above I_lim_H and below the over-current threshold "OC_hs(ls)" and

the duration above Ion_threshold is longer than “Tdiag2”, then "OCxx1:0" are set to

"10" which means "NO OVER-CURRENT" (current limitation reached).



If the Tdiag1 duration cannot be reached and no overcurrent detected for duration

Toc_hs(ls), then "OCxx1:0" are set to "10" which means "NO OVER-CURRENT".



If the current is above Ion_threshold and below the over-current threshold "OC_hs(ls)"

and an overcurrent is detected in same time as diagonal MOS, then "OCxx1:0" are set

to "11" which means "NO OVER-CURRENT BUT IO-ON is above threshold"

In case the overcurrent threshold is reached after Tdiag1+Tdiag2 expiration (worst case),

the device is still protected by an automatic shut-off after Timer expiration.

Ion_th

ILoad

Ioc

Tdiag2

Tdiag1

User case for validity bit assertion

GAPGPS02551

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