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sakibnaz 11th January 2012 08:59 PM

TOSLINK Receiver (TORX147) Problem
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I am doing a project where I need to use TOLink Transmitter and Receiver. As my device is powered from 3.3V, so I chooses TOTX147 and TORX147 TOSLink cable connectors.

I have connected a Switch with TOTX and a LED with TORX. The problem I am facing is, TOTX147 is working fine but when Light comes in through the TOSLink cable TORX147 VOUT PIN Not generating any Voltage.

I have also some other connectors: TOTX177 and TORX177 which need 5 Volt to operate. Same circuit I have tested with this 5 Volt Connectors (with Supply 5V) which are working fine.

But as I need to operate from 3.3V so I need to fix the problem with TORX147.

Any suggestion please ... why I am not getting the VOUT from TORX147.

I have purchased several Parts from Several store. But all result are same. TOTX147 working but TORX147 not.

My TOSLink Test Schematic is attached.

Thank you in advance. Please help me out on this TORX issue.


Ken Newton 11th January 2012 10:17 PM


Originally Posted by sakibnaz (

Any suggestion please ... why I am not getting the VOUT from TORX147.


Try disconnecting that resistor + LED circuit attached to the TORX output and see if the signal now appears. I'm wondering whether the LED circuit is loading down the output signal voltage.

sakibnaz 13th January 2012 11:00 AM

Hello Ken.

Thanks for your message.

I tested again without Resistor. I measured the Voltage directly at TORX147 VOUT PIN, buts same result. When light comes through TOSLink cable, no VOUT Voltage.

Is my schematic ok? I am asking cause, I did not use any Capacitor and Induction though its mentioned this the TORX147 Application Circuit. Because with TOTX177 (5V TX) and TORX177 (5V RX) I got good VOUT without this Capacitor and Inductor.

Any advice please ...

Can anyone suggest any other TX and RX compatible with TOTX147 and TORX147?


Ken Newton 13th January 2012 02:33 PM

Let's verify a few basic conditions of your circuit so that we're not erroneously assuming anything. Please forgive any of the below questions which may come across as insultingly simple.

1. First, verify that the optical transmitter and cable are operating correctly. The easiest way to do this is to simply connecting them to some commercial DAC or digital AV receiver with a Toslink input. If the problem remains, then you have isolated it to the optical transmitter or the cable. Swap in a different optical cable to determine which is the problem. Conversely, you could instead connect a CD/DVD player with a Toslink output to your optical receiver circuit.

2. When you are checking for an TORX output voltage you should be using an oscilloscope. The output TORX receiver output signal will be high in frequency (several Megahertz) and you will not get a proper reading should you be trying to use a Digital Voltmeter.

3. You mention using a switch at the transmitter circuit. How exactly are you utilizing that switch? It would be helpful if you would include that switch in your schematic.

4. Lastly, while you should have included proper power supply decoupling (capacitors and ferrite chokes), the circuit still should produce an output signal if everything else were okay.

SoNic_real_one 13th January 2012 05:11 PM

The ORX147 has a 2mA output current. That LED will overload the output and possibly damage it.
Also, soldering time should not be longer that 10 seconds.
Absolute maximum supply voltage is 4.5V and should not be over for any short time (check the power supply).

PS: Funny, I found out your post on the Toshiba forums too :)

sakibnaz 13th January 2012 05:55 PM

Thanks for all of your reply.

Yes the TOSLink cable and TOTX147 is working fine. The only problem in receiver section. I am using Digital Multimeter to check the RX VOUT Voltage.

Basically my need is very simple. I am giving 3.3V to TOTX147 VIN PIN and what to detect the VOUT at TORX147. I am not using any High Freq signal.

I am using DC Supply from USB Port and drop the +5V to 3.3V using Regulator. Do you think USB Source can be a problem as so far I know USB Ports Max Current Supply is 500mAH?

- Is there any other (TOSHIBA or Non TOSHIBA) TX and RX compatible with TOTX147 and TORX147 which I can use?
- Today I also checked DiGiKey and Mouser but this Parts are our of Stock. Is there any other good store to order them?

Actually I am worried cause ... all under this same condition TOTX177 and TORX177 works fine.

Yes, I posted this issue on TOSHIBA Forum also, and wait few week ... but no one replies :(


Ken Newton 13th January 2012 07:50 PM

Remote troubleshooting is one of the more difficult endeavors. I was about to mention that the TORX147 datasheet has a minimum data rate spec. of 100kbps. The link protocol is modulated biphase marked. D.C. levels cannot be used directly without proper modulation.

Given, however, that you said the Toshiba 177 pair work fine in the same circuit, I don't know what else to suggest.

JensH 13th January 2012 08:37 PM

I also wondered whether the minimum data rate could be the problem. It could be that the two receivers behave differently when DC is used. The descriptions in the two data sheets are similar, but that does not necessarily mean that they behave in the same way.
Do you have an SPDIF source available for testing? Or could you modulate the transmitter with a square wave from a signal generator at more than 100kHz?

sakibnaz 13th January 2012 08:59 PM

Hi JensH. Thanks for your reply.

Actually I am controlling the TOTX from Microcontroller. My thinking is, as TOTX working when Microcontroling giving Voltage to VIN PIN so RX VOUT PIN should generate Voltage (cause cable is connectied between TX and RX and red light is passing through).

I have tested my Circuit by giving manually 1.5V ~ 3.3V to the RX VOUT PIN PCB PAD (By remove RX from the Board) ... the system behaves as expected.

Anyways, I am thinking some how the RX Parts are damaged :(

Can anyone refer good China Store to order TOSLink Parts?


Bacconary 13th January 2012 09:33 PM

The support voltage for the TORX need to be noise filtered. Otherwise the TORX does not work as he should. First use a simlpy LC filter over the 3,3V like this

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