THVD1550: Behavior of THVD1550 when the power supply voltage is lower than the Recommended Operating Conditions

Masanori-san,
Internally THVD1550 has POR circuitry to monitor the supply. If the supply is lower than 4.5V but higher than POR threshold, the device still functions but might fail some specification. If the supply is too low, POR will shut down the device therefore TX and RX output will become high Z. During power up/down stage, the device won't generate any glitch on these output pins (a highlighted feature on first page). If there is any specific use case you have concern, please let me know.
Regards,
Hao

Hello Hao-san,

Thank you for kindly teaching me.

Our customer is planning to use RS-485 communication with multi-point connection.
The customer has concerns whether RS-485 communication will be affected or not when turning off one RS-485 transceiver "THVD1550" connected multi-point line.

I think no problem in the state where POR is applied, because the output of the driver is Hi-Z.
However, due to the customer's system configuration, the power supply voltage of RS-485 transceiver drops slowly when the power is off.
The customer's matter of concern is whether the driver of RS-485 transceiver does not output unnecessary until POR is applied.

Since glitch does not occur, may I understand there is no problem for above point of view?

Best regards,
M. Tachibana

Masanori-san,

From your description, it should not be an issue in the application. The device was designed to have no glitches in power up/down scenario, in which many variations have been taken into account, such as ramp time. Please let me know if you have other questions.

Regards,

Hao

Hello Hao-san,

Thank you for the explanation.

I understood that there was no concern with slow power off.
I think that customers can use at ease

Best regards,
M. Tachibana