THVD1451: VOCM Voltage

Pranay Upadhyay

Part Number: THVD1451
Other Parts Discussed in Thread: SN74LVC2G86, DS26LS32MQML, DS26LS31C, AM26LV31E, AM26C32, AM26LV32E, AM26C31, AM26C31-EP, AM26C31M, DS26C31MQML, SN75179B

Dear Team,

Our requirements is to convert single ended TTL input to Differential TTL Output with Common Mode Voltage -1.65V. As per Datasheet VOCM is VCC/ 2 to 3V. When we use VCC= 3.3VDC then we will get VOCM = 1.65V.

As per datasheet Is it possible to get VOCM = 3.3V. How can we change VOCM and fixed it to 1.65V.

Please guide.

over 1 year ago

0 Eric Hackett over 1 year ago

TI__Guru 74292 points

Pranay,

An engineer has been assigned to this thread and will respond by end of business Tuesday next week.

Regards,

Eric Hackett

0 Clemens Ladisch over 1 year ago

Guru 317320 points

What exactly do you mean with "differential TTL output"? The THVD1451 is an RS-485 transceiver, so its output voltage conforms to the RS-485 specification.

To output differential signals at 0 V and 3.3 V, route the same signal into a buffer gate and an inverter gate. To minimize the skew, implement this with two XOR gates like the SN74LVC2G86.

0 BOBBY over 1 year ago

TI__Guru 73851 points

Hi Pranay,

Do you have more information on what you're planning to interface with on the differential side? RS-485 generates the 'negative' voltage by comparing A-B where current flows from A to B to generate a positive VoD (A is output HIGH/Vcc while B is outputting LOW/GND when driving); while current flows from B to A to generate a negative VoD (B is output HIGH/Vcc while A is outputting LOW/GND when driving) so when A-B is measured across the 60 ohm load the voltage is negative.

Using an RS 485 driver may not be the right approach here if the above explanation isn't the kind of differential output you are looking for.

-Bobby

0 Pranay Upadhyay over 1 year ago in reply to Clemens Ladisch

Prodigy 40 points

Thanks for response.

We are trying to use Differential Line Driver for Line Receiver DS26LS32MQML.

https://www.ti.com/lit/ds/symlink/ds26ls32mqml.pdf?ts=1715666982961&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FDS26LS32MQML

As Line Driver for DS26LS32MQML as per datasheet DS26LS31C is obsolete.

Please suggest suitable part.

0 Pranay Upadhyay over 1 year ago in reply to BOBBY

Prodigy 40 points

Thanks for response.

We are trying to use Differential Line Driver for Line Receiver DS26LS32MQML.

https://www.ti.com/lit/ds/symlink/ds26ls32mqml.pdf?ts=1715666982961&ref_url=https%253A%252F%252Fwww.ti.com%252Fproduct%252FDS26LS32MQML

As Line Driver for DS26LS32MQML as per datasheet DS26LS31C is obsolete.

Please suggest suitable part.

0 Clemens Ladisch over 1 year ago in reply to Pranay Upadhyay

Guru 317320 points

Modern replacements are the AM26C31/AM26C32 (or AM26LV31E/AM26LV32E for a 3.3 V supply).

Do you need a military temperature range (AM26C31-EP) or military qualifications (DS26C31MQML, AM26C31M)?

0 Pranay Upadhyay over 1 year ago in reply to Clemens Ladisch

Prodigy 40 points

Thanks for response.

DS26LS32MQML part is at receiver side for differential input and DS26LS31C generating Differential Output.

Could we use THVD1451 or SN75179B to accept Differential line from DS26LS31C and generate differential line to DS26LS32MQML ?

0 Clemens Ladisch over 1 year ago in reply to Pranay Upadhyay

Guru 317320 points

Your application can be best described as RS-422.

All the devices you've mentioned can be used for RS-422, and are compatible with each other. (Full-duplex RS-485 transceivers are compatible with RS-422.) (The common-mode voltage does not really matter; all receivers accept a wide range.)

The x26x31 devices are four-channel transmitters. The x26x32 devices are four-channel receivers. If you need four channels, the x26x3x devices might be the simplest solution. If you need fewer channels, 1+1 transceivers like the THVD1451 might be simpler.

0 BOBBY over 1 year ago in reply to Pranay Upadhyay

TI__Guru 73851 points

(Thank you Clemens)

Hi Pranay,

Do you have any follow up questions or did Clemens clarify everything for you?

-Bobby

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THVD1451: VOCM Voltage