[FAQ] TDA4VM: Is Fast Mode Plus supported?

Part Number: TDA4VM

TDA4 I2C Fast Mode Plus support and pullup resistor recommendations

FAQ:  What value of pullup resistor should be used on the I2C Open-Drain SCL and SDA lines when using I2C in Fast Mode Plus mode?

Summary Response:  The TDA4VM device does not support the full I2C Fast mode Plus spec (1.0 MHz), due to the extremely high capacitive load that is documented as part of that spec.  However, in practical applications, the TDA4VM device can support Fast Mode Plus frequencies based on the following considerations.

When using I2C Fast Mode Plus, the recommendation is to use 2.2 KOhm to 4.7 KOhm pullup⁽¹⁾ resistors from the SCL and SDA lines to 1.8V or 3.3V, and to minimize the bus capacitive loading (e.g., connect to only 1 peripheral, and keep the total bus capacitance per line to <25pF).

⁽¹⁾ Optimal pullup resistor value depends on the capacitive loading of the SCL and SDA lines.  Refer to I2C Bus Pullup Resistor Calculation (SLVA689).

Additional Information:  Although the I2C bus spec lists a maximum capacitive load for each bus line of up to 550pF,  such high capacitance is not recommended when using TDA4 devices.  High bus capacitance necessitates use of low-resistance pullup resistors on SDA and SCL lines, resulting in high current through the open-drain output driver.  Bus capacitance of <25 pF allows use of pullup resistors in the recommended 2.2KOhm to 4.7KOhm range.  Bus capacitance of up to 50pF can be handled by using 2.2KOhm pullup resistors.  Higher bus capacitance can be handled by using lower-resistance pullup resistors although the resistance must be calculated in accordance with SLVA689 while taking into account the TDA4 I2C Open-Drain I_OL spec.