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TIOS101: VCC voltage in low-side only (NPN) application

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Part Number: TIOS101

Hello,

I'm going to use the TIOS101 (no-LDO version) a low-side driver only. From the datasheet and discussions in this forum, it looks like that the VCC pin shall be powered even the voltage is not passed to the OUT pin (as it would be in high-side configuration). The application diagrams indicate that the VCC is used only to power the internal LDO (for applicable TIOS versions only) and the high-side driver. However because it is only illustrative diagram I'd like to ask following questions:

1. Can you please confirm that the TIOS101 cannot operate on low-side only mode with VCC_IN=5V and VCC= floating?

2. When both VCC_IN and VCC are needed, is it possible to operate the device from single 5V supply? The question arises from hypothesis that the minimum operating 7V voltage may be necessary to supply the internal LDO which is not needed in this case.

Thank you.

Josef Rypar

  • Hello Josef,

    Thank you for your interest in the TIOS101 and I would be happy to answer any questions you may have.

    1. Can you please confirm that the TIOS101 cannot operate on low-side only mode with VCC_IN=5V and VCC= floating?

    No, all versions of the TIOS101 are primarily powered through the higher voltage VCC pin and it cannot be left floating.  All versions have an internal LDO to power the digital core which requires the 7V on the VCC pin.  This isn't clearly shown in the diagrams, but the Diagnostics and Control block is supplied from the internal LDO that is sourced from the VCC pin.

    The differences in the devices comes to how the digital IO are handled and whether additional LDO current is sourced from the device, or the device requires an external voltage be supplied to set the thresholds and operate the digital IO circuitry.  I will also note, there is a fundamental difference in the TIOS101 (non-LDO) version and the TIOS1013/5 (LDO) versions in how the LDO is implemented.  However the digital core is fundamentally the same and it makes a determination on whether it is an LDO version or non-LDO version when it powers up by sensing whether there is a voltage present on the VCC_IN pin or not.  On the TIOS101, if the VCC is supplied, but the VCC_IN is not, the device will think it is LDO version and try to source a voltage on the VCC_IN pin.  However, once any decoupling capacitors are charged with this leakage voltage to approximately 3.3V, it will determine that it is the non-LDO version, and change to the non-LDO version causing the caps to discharge until the cycle repeats itself.  As a result, the TIOS101 requires both the VCC and VCC_IN to be supplied in order for the device to function properly.  No damage to the TIOS101 will happen by applying these voltages at different times, but if VCC_IN is not present when VCC is supplied, there may be some voltage detected on the VCC_IN pin at very low current (100uA).

    2. When both VCC_IN and VCC are needed, is it possible to operate the device from single 5V supply? The question arises from hypothesis that the minimum operating 7V voltage may be necessary to supply the internal LDO which is not needed in this case.

    No, due to the internal LDO that supplies the internal core, the device needs 7V.  The TIOS1013 or TIOS1015 is capable of operating off of a single supply but that must be the 7V VCC.

    I hope this answers your questions.  If you have any additional questions, please feel free to follow up in this post or in a new one.

    Regards,

    Jonathan

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