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# SN74LVC2G04: SN74LVC2G04 Voh

Part Number: SN74LVC2G04

Hello Team,

For 3.3V application, the max Voh is 0.5V@24mA, but the ASIC Vil is 0.3V, so there should be risk.

Can you share the internal circuit of this part? Why the Voh is different when there is different Ioh? Thanks

Regards,

Nanfang

• The output MOSFET behaves pretty much like a resistor when in the allowed range, so the actual VOH depends linearly on the current.
(See figure 16 of Input and Output Characteristics of Digital Integrated Circuits at 3.3-V Supply Voltage (SZZA010).)

The input impedance of a CMOS input is approximately infinite, so the actual current is approximately zero.

• Hi Nanfang,
The output of the SN74LVC2G04 is a typical push-pull CMOS inverter.

When the output is driving LOW, current is sinking into our device and passing through a single n-channel MOSFET. This MOSFET will have an associated internal resistance, which will produce a voltage drop. In the case you have listed, 24mA with a 0.5V drop, using Ohm's law we can calculate the output resistance, which is 0.5V / 24mA = 20.83 ohms.

The output resistance should be close to that value all the way from 1mA up to 24mA. Can I ask why your application requires 24mA of constant current drive? Most logic applications have current less than 1uA.
• Hello Emrys,

Thanks, it is a push-pull COMS inverter. My application has very small current drive. I just want to know what's the internal circuit and how to calculate the resistor, now I know it, thanks

Regards,

Nanfang