TCA9517A: How TCA9517A influence the port input capacitance

Evan Peng

Part Number: TCA9517A

Tool/software:

Hi Expert,

This is Shenzhen FAE Evan. My customer use TCA9517A as a buffer between system SOC I2C port and external HDMI I2C port as shown in the schematic below. And A side is connected to external HDMI port, B side is connected to internal system SOC I2C. The issue is that, one test item of HDMI certification is the port input capacitance(should be below 50pF@100kHz I2C signal). The input capacitance Ci can be found in datasheet 13pF, I need to know how this parameter is measured, when IC is enable or not? When IC is enable, will the circuit after SCLB and SDAB have an influence on the total input capacitance at HDMI1_SCL_IN and HDMI1_SDA_IN? If TCA9517A can not remove the after-stage circuit capacitance influence, what device is recommended here?

over 1 year ago

0 Michael Ikwuyum over 1 year ago

TI__Guru 51816 points

Hi Evan,

Each device comes with some capacitance on each pins. This is by design and not measurement. It is designed with parasitics and total lumped sum of the specified capacitance and it’s always there pin or bus line.

if too large for customer design, please clarify target pin capacitance that will be okay for additional recommendation as this can not be 0 pF, thanks.

Best Regards,

Michael.

0 Evan Peng over 1 year ago in reply to Michael Ikwuyum

TI__Intellectual 1395 points

Hi Michael,

So, will the enable or disable status change the capacitance on SDAA and SCLA?

Regards,

Evan

+1 Michael Ikwuyum over 1 year ago in reply to Evan Peng

TI__Guru 51816 points

Hi Evan,

Unfortunately, no. EN pin on its' own has its' specified capacitance when enabled or disabled and SDAA and SCLA have their own independent capacitance, thanks.

Best Regards,

Michael.

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TCA9517A: How TCA9517A influence the port input capacitance