L9942 datasheet(34/40 Pages) STMICROELECTRONICS

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Appendix

L9942

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Doc ID 11778 Rev 7

bridge and current comparator has as new reference the overcurrent limit. A shortage to

ground can be detected, but not between the outputs.

Is it recommended to use the different fast decay modes too, especially in period if the load

current has to reduce from step to step. The duration of fast decay can set by fixed time ore

that it depends on the comparator signal utilizing the second current mirror at LS switch.

There can be monitored the undershoot of bridge current during OFF state.

Fast decay can be seen as switching the bridge in opposite direction, if it is compared to ON

state before. The load current control at HS switch is not used, but the comparator is still

active. The reference value is changed to overcurrent limit and a shortage to ground or now

between the outputs too will result in a signal. The internal filter time of at least 4 us will

inhibit the signal in many applications. Then you can use the mode “auto decay without any

delay time“ (On Section 5.1 mode 100). On page 12 you can find in the lower part of

Figure 3 the phase counter values, when fast decay as only part of mixed decay is used and

the shortages can be detected during a longer time. After this it is signalized in register 7 as

overcurrent in HS switch (e.g. in Figure 17 HSA1).

L9942 Datasheet(PDF) 34 Page - STMicroelectronics