L9663 Sync Pulse Interval

[ZXinb.1]

Dear,

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From the datasheet of L9663, the minimum interval of sync pulse period is 200us. But I want to send the sync pulses with period less than 200us, how can I do it?

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In the datasheet, it mentioned "If full flexibility for the sync pulse interval is required, use direct triggering either via SPI or direct interface."

But in the SPT register, it described the 200us "Minimum allowed period (if SYNC pulse trigger is generated by PIN or SPI)." The two sentences looks contradictious, or to say there is a special way to send the "direct triggering" signal?

And the 200us determined by the bootstrap circuit, but this bootstrap circuit could be bypassed. So it's possible to send the sync pulse with period less than 200us in principle.

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Thank you.

[TEvan.3]

SPT (Sync Pulse Timer) won't allow a shorter interval that 200us. For internally generated and external sync. Why would you want them closer? There would be no room for the returned data if they're too close together.

[Livius]

Is it an official answer about that there's no way to use lower sync pulse period then 200 us?

L9663 datasheet - page 19.

"The bootstrap circuits are enabled by default, activated by internal logic with timing sync pulses dependent, and can be disabled later on through a dedicated SPI command. The bootstrap block can recharge the capacitor so that subsequent sync pulses are allowed with a minimum period of 200 μs.

A useful option is the possibility to connect the BHx pin directly to a high voltage rail. In this configuration, VB has also to be connected to the same high voltage rail and the bootstrap circuit can be bypassed by disabling it through the dedicated SPI command (bit 12 of CH1_CR2, CH2_CR2, writable during PROG phase).

The bootstrap blocks are automatically switched off in case the voltage on VB is high enough to allow proper regulation. In this case both CBx capacitors should be omitted."

So, if i use VB = 12 V supply and i use this same supply, BHx = 12 V too, without any CBx capacitor, then after the bootstrap disabling, still not usable any lower sync pulse period then 200 us by an external SYNCx triggering? Recharge time for bootstrap capacitor (CBx) is max 130 us, so it can be a physical limitation but what happens if it is totaly disabled and do not need to do this charging?

For most of automotive airbag sensors need to use 120 us sync pulse period in bidirectional communication.