LP8758-E0: SDA/SCL pin

Yuto Sakai

Mastermind 6100 points

Part Number: LP8758-E0
Other Parts Discussed in Thread: LP8758

Hi,

Could you tell me about SDA/SCL pin of LP8758-E0.

Is there a connection such as pulldown, pull-up etc. inside the SDA/SCL pin?

When this device is off, is the level of these pins Hi-Z?

Best Regards,

Yuto Sakai

over 6 years ago

0 Krishnamurthy Hegde over 6 years ago

TI__Expert 8730 points

Hi,

I have assigned your request to responsible Applications Engineer and we will get back to you as soon as possible.

Regards,

Murthy

0 Jari Niemela13 over 6 years ago in reply to Krishnamurthy Hegde

TI__Expert 5600 points

Hi Sakai-san,

SCL and SCL pins do not have pull-up or pull-down resistors on chip. They are Hi-Z in off state.

Best regards,

Jari Niemelä

0 Yuto Sakai over 6 years ago in reply to Jari Niemela13

Mastermind 6100 points

Hi Jari-san,

Thank you for your reply.

I confirmed the voltage of SDA / SCL pin with LP8758-E0 EVM.

Then an intermediate voltage of about 1.5 V was confirmed like the image below.(CH1:SDA,CH2:SCL)

The condition is that there is no power supply to VIN, only USB is connected from the PC.

From this, I think that the SDA / SCL pin has a pull-down resistor, and the pulled-up voltage appears to be divided in SDA / SCL.

Is SDA / SCL really Hi-Z?

Best Regards,

Yuto Sakai

0 Jari Niemela13 over 6 years ago in reply to Yuto Sakai

TI__Expert 5600 points

Hi Sakai-san,

There is no passive pull-down resistors in SDA or SCL lines. Voltage leaks from SCL and SDA pins via internal structure if VIN is not present. This is normal behavior.

When VIN voltage is present SCL and SDA are Hi-Z.

Best regards,

Jari Niemelä

0 Yuto Sakai over 6 years ago in reply to Jari Niemela13

Mastermind 6100 points

Hi Jari-san,

Thank you for your reply.
Could you tell me about the detail of "internal structure"?
I would like to know what kind of route the leak exists and our custormer would like to know the information.

Best Regards,
Yuto Sakai

0 Jari Niemela13 over 6 years ago in reply to Yuto Sakai

TI__Expert 5600 points

Hi Sakai-san,

There is ESD protection structure which leaks due to missing VIN voltage.
The LP8758 is designed to be used so that when SCL/SDA has voltage also VIN voltage is present.

Best regards,
Jari Niemelä

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LP8758-E0: SDA/SCL pin