Signal Driving problems

[Norman Yang]

Hello all:
I have meet a problem that seems related to the chip driving capacity.
The problem is like this:
There is a bi-direction signal on the board. Logic value error is
detected on it. When we check the errors, we found that the signal is
not the ground when it need to be "0". There is a 0.5 ~ 0.6 v margin
between the signal low level and the ground. It would stay there and
dont get lower more.

There is also the case that the signal could be drived to ground by
the same device but the falling edge it slow.

The device we are using is already for sell so we think it is a good
one. So the problem is on the board. But we dont find anything
abnormal on the board, include the power supply to that chip. (It
seems ok to me)

Could any one here give me some advice about check what place for this
problem. Thank any way.

Regards!
Norman

 

[Paul]

Norman,

You need to specify the circuit that is driving the signal, and
what else is attached to the signal. If there is an active input
(TTL, resistor pull-up, etc), then having a non-zero low voltage
might be correct.

Paul


Norman Yang wrote:

Hello all:
I have meet a problem that seems related to the chip driving capacity.
The problem is like this:
There is a bi-direction signal on the board. Logic value error is
detected on it. When we check the errors, we found that the signal is
not the ground when it need to be "0". There is a 0.5 ~ 0.6 v margin
between the signal low level and the ground. It would stay there and
dont get lower more.

There is also the case that the signal could be drived to ground by
the same device but the falling edge it slow.

The device we are using is already for sell so we think it is a good
one. So the problem is on the board. But we dont find anything
abnormal on the board, include the power supply to that chip. (It
seems ok to me)

Could any one here give me some advice about check what place for this
problem. Thank any way.

Regards!
Norman