AM26C31: Current between channel pairs are >20mA

Art Mecina

Part Number: AM26C31
Other Parts Discussed in Thread: AM26LS31

Hello Guys,

Good day.

Our customer is using AM26C31 in their encoder, but when they test the current between channel pairs (they use 120 ohms between the channel pairs), the current measured is around 23-24 mA. However, based on the datasheet, the current should be limited within 20mA only.

What could be the reason? They are asking because their customer asked for current limitation with 20mA.

Note that the channel pairs measurement were done between pin2 and pin 3, between pin 5 and pin 6, between pin 10 and pin 11 and as such.

Thanks and regards,

Art

over 3 years ago

0 Hao L over 3 years ago

TI__Mastermind 25705 points

Art,

The output voltage and current curves can be found in this thread. 20mA is a recommended value, not the maximum. Actually you can tell the device works up to 40~50mA load.

0 Art Mecina over 2 years ago in reply to Hao L

TI__Genius 16505 points

Thanks Hao!

0 Hao L over 2 years ago in reply to Art Mecina

TI__Mastermind 25705 points

Art,

AM26LS31 has the similar driving strength as AM26C31. The Voh/Vol spec ((2.5V-0.5V)/20mA) is equivalent to 2V Vod over 100Ohm (RS-422 standard).

With heavier load (for example 54Ohm), the devices may not meet the min 1.5V standard of RS-485. But as long as the receiver side has enough margin over its threshold, the communication should work fine.

Interface

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AM26C31: Current between channel pairs are >20mA