JAJSCO5C November 2016 – June 2018 TUSB422
PRODUCTION DATA.
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The TUSB422 supports a large VDD supply range allowing it to be powered from an external battery (VBAT).
The TUSB422 I2C slave interface supports up to 1 MHz (Fast Mode+) at either 1.8 V or 3.3 V signal levels. Depending on the signaling level of the I2C master, the TUSB422 SDA and SCL should be pulled up to either 1.8 V or 3.3 V. For this particular example, the SDA and SCL are pulled up to 1.8 V. The actual pullup resistor value chosen is based maximum I2C bus capacitance and the maximum I2C frequency. A 1.5 KΩ resistor was chosen to support a 150 pF maximum I2C bus capacitance and a 400 KHz I2C clock.
The INT_N pin is used by the TUSB422 to communicate events to software running on an external CPU. This pin requires an external pull-up resistor to 1.8 V, 3.3 V, or TUSB422 VDD supply. Typically, INT_N is pulled up to the same supply as the SDA and SCL pins. The recommend pull-up value is 200 KΩ.
The USB Type-C specification uses VCONN to power Type-C active cables and cable plugs. The minimum VCONN power mandated by the specification is 1 W. The TUSB422 incorporates an internal switch to route power from VCONN pin to one of the CC pins (CC1 or CC2). A recent ECN for VCONN redefines VCONN voltage range to 3 V — 5.5 V from the originally defined 4.75 V — 5.5 V. Given TUSB422 maximum Rds(on) and the minimum I(VCONN) current, the allowable VCONN power through the TUSB422 is derived by Equation 1.
where:
For this example, to support the minimum Type-C V(VCONN) requirement (1 Watt at 3 V), the voltage on the VCONN pin must be greater than 3.25 Volts [(0.333 A x 0.75 Ω) + 3 V]. If system designer desires to support the old VCONN requirement of 1 W at 4.75 V, then the voltage on the VCONN pin must be greater than 4.9 volts [(0.21 A x 0.75 Ω) + 4.75 V].