Tool/software:
Hello,
The standard MIDI IN schematic contains an optocoupler to receive incoming signals.
I have good results with 6N138.
But what opto-emulator would be the best replacement?
MIDI runs at 31250 bits per second and most designs are 5V
Thank you in advance!!
Bas ten Hoor
That circuit could be improved by changing R1 to 1 kΩ, and adding a 10 kΩ resistor from pin 7 to GND. (Source)
Anyway, the ideal optocoupler for MIDI is a digital device that switches with (less than) 5 mA and supports a speed of 31.25 kbit/s, such as the PC900/H11L1. ISOM811x devices are designed to have characteristics similar to ananlog phototransistor optocouplers, which usually are too slow for MIDI, but the ISOM811x actually are faster, and fast enough that it is likely to work. The ISOM8110 has the lowest propagation delay. For the best signal quality, minimize the pulse width distortion, i.e., choose a pull-up that results in the same switching time for falling and rising edges, i.e., about 1 kΩ…2.2 kΩ. (Figure 6.2 (below) is for a forward current of 1.6 mA, so you can add a resistor of 1 kΩ in parallel with D1. But the minimum CTR is 100 %, so you should reduce the forward current only if using a pull-up larger than 1 kΩ.)
Hello Bas,
As Clemens said, the ISOM811x opto-emulator family is ideal for applications that need isolation with optocoupler behavior at faster data rates. ISOM8711 will have a closer pinout to the original application and be able to support up to 25Mbps as well.
You should be able to order/request samples directly on TI.com. Samples can be requested by logging in and navigating to the device's ordering and quality section as shown below (your webpage may look a little different).
Best,
Andrew
Hello Clemens,
I've signed up for Samples and set up my account.
Normally I can select sample request, but with this part the 'Request Sample' button is not there and I can only order.
I got to this page through the dataheet, where I clicked the request samples button
