Hi,
ok, I think I need some help here - I tried the Sn74CBTD3861, which looked good at the first sight, but in my application it has the problem, that it produces too high voltages on the 3V side.
Reproducable, I tried two chips.
I think, the problem is, that I added 1K as pull-up - resitors on the 5V side.
Ok, more details:
I need level-shifting for (minimum) two busses: Commodore IEC and PS2 (Keyboard, 5V 2x Datalines)
IEC is :
1 x 5V -> Teensy input
1 x Teensy output -> 5V
3 x 5V <--> teensy bidirectional.
The speed is not high - absolute maximum is around 300kBIT / second.
The solution should be small, I don't want masses of transistors and resistors, and I try to use a minimum amount of SMD parts.
The problem with integrated circuits is : The serial IEC Bus is quite old. It is a active-low bus ("open collector") with 1K PULL-UPs in every device. It is possible to connect up to 8 devices - so 8*5mA = 40mA per line!! max.
But it is very unlikely that all all lines will be driven low at the same time.
Transistors + resistors take much room ... and is a lot to solder.
Does anyone have any hints for me ?
Edit: + I need a solution for the PS2 Keyboard which is 5V, too.
Edit2: Later, I want to add the "UserPort" wich adds >10 more 5 Volt signals, bidirectional (but without the pullup resitors on board) "open collector"
Edit3: Worst case, I can reduce the amount of allowed devices to one, two, or three..
Edit4: I have NO direction signal for the bidirectional lines.
ok, I think I need some help here - I tried the Sn74CBTD3861, which looked good at the first sight, but in my application it has the problem, that it produces too high voltages on the 3V side.
Reproducable, I tried two chips.
I think, the problem is, that I added 1K as pull-up - resitors on the 5V side.
Ok, more details:
I need level-shifting for (minimum) two busses: Commodore IEC and PS2 (Keyboard, 5V 2x Datalines)
IEC is :
1 x 5V -> Teensy input
1 x Teensy output -> 5V
3 x 5V <--> teensy bidirectional.
The speed is not high - absolute maximum is around 300kBIT / second.
The solution should be small, I don't want masses of transistors and resistors, and I try to use a minimum amount of SMD parts.
The problem with integrated circuits is : The serial IEC Bus is quite old. It is a active-low bus ("open collector") with 1K PULL-UPs in every device. It is possible to connect up to 8 devices - so 8*5mA = 40mA per line!! max.
But it is very unlikely that all all lines will be driven low at the same time.
Transistors + resistors take much room ... and is a lot to solder.
Does anyone have any hints for me ?
Edit: + I need a solution for the PS2 Keyboard which is 5V, too.
Edit2: Later, I want to add the "UserPort" wich adds >10 more 5 Volt signals, bidirectional (but without the pullup resitors on board) "open collector"
Edit3: Worst case, I can reduce the amount of allowed devices to one, two, or three..
Edit4: I have NO direction signal for the bidirectional lines.
Last edited: