SN65HVD1471: Problem in communicating SN65HVD1471 transceiver with MAX14850 isolator

user4764564

Part Number: SN65HVD1471

Hi, I met a problem when i tried to interface my SN65HVD1471 transceiver with MAX14850 isolator. Please refer to my connection below,

R(Transceiver) - INA1- OUTB1 - Rx(MCU)

Tx(MCU) - INB1 - OUTA1 - D(Transceiver)

Transceiver differential pair

A - TX+

B - TX-

Y - RX+

Z - RX-

Between A and B, Y and Z i connected 120 Ohms . After this connection does not works, i loop back the connection between OUTB1 and INB1, now also it is not working. I also tried with I/O pins. Please point out my mistake.

over 5 years ago

0 Miguel Robertson over 5 years ago

TI__Guru 62920 points

Hello,

Y and Z are the transmitter outputs. A and B are the receiver inputs. It sounds like you may have them swapped - can you please double check this?

Regards,
Max

0 user4764564 over 5 years ago in reply to Miguel Robertson

Intellectual 380 points

This is my schematic. During hardware check, i loop back D and R, it works. But when i loop back UART_tx and UART_rx, it won't work.

0 Miguel Robertson over 5 years ago in reply to user4764564

TI__Guru 62920 points

If it works when you loop back D to R then the connections from the UART to the isolator must be OK. (It should also work, then, if you loop back Y to A and Z to B; have you tried this?)

When you loop back UART_tx to UART_rx, are both VccA and VccB of the isolator powered up? I'm wondering if side A might be active and driving a low level that may be interfering with the loopback data.

Also, I noticed that these ports of the isolator are open-drain. I don't see a pull-up resistance on the UART_tx or UART_rx lines, though - is this implemented somewhere else on the schematic (or integrated into the MCU)?

Regards,
Max

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SN65HVD1471: Problem in communicating SN65HVD1471 transceiver with MAX14850 isolator