Hello,
My customer uses 3.3V and 1.5V pull-up voltage on PG and EN of the TPS7A7300 depending on the project.
What are the recommended pull-up resistor values for 3.3V and 1.5V respectively? How should the customer determine the value based on the pull-up voltage?
Thank you.
JH
Hello JH,
For the PG pin, the theoretical limitation is based on the voltage listed in the datasheet, the voltage you need, as well as the maximum sink current the LDO pin can provide. For this device that is 1mA and 0.4V. So if you operate at 3.3V pull up, and 0.4V is adequate then (3.3V - 0.4V) / 1mA = 2.9 k-ohms. You need at least 2.9k ohms resistance for this pull up. It is common to use a value of 10k ohms to 100k ohms, or a resistor already in the BoM in this range.
If you need to dissipate less power then you will want a larger resistor. At some point the pull up resistor value will make an impact with the leakage current. The leakage current for the EN pin is 0.1 uA and for the PG pin is 1uA. If a high pull up resistor is used, the leakage current will begin to multiply by the pull up resistance to reduce the voltage drop across the pull up resistor, and increase the voltage from the PG pin or EN pin to GND. 0.4V drop on the PG pin will happen at 400k pull up (1uA * 400k = 0.4V). So if the connecting electronics need that voltage or less to detect as a logic low, you will have an upper range of 400k ohms. Similar math can be performed on the EN pin.
Thanks,
- Stephen
