How can we determine whether the IC's fault output PIN can drive the transistor?

小太阳yy

How can we determine whether the IC's fault output PIN can drive the transistor? [Copy link]

How can we determine whether the fault output PIN of IC can drive the transistor? Which parameters should we look at?

maychang

"How can I determine whether the IC's fault output PIN can drive the transistor?"

Whether it can drive a transistor obviously requires careful reading of the datasheet.

As for the "fault output PIN", not sure what that means.

小太阳yy

maychang posted on 2022-4-28 15:59 "How can I determine whether the fault output PIN of the IC can drive the transistor? " Whether it can drive the transistor, obviously you have to read the datasheet carefully. As for...

Similar to the OPEN drain output pin

maychang

Xiao Taiyangyy posted on 2022-4-28 17:48 Similar to the OPEN drain open drain output pin

Let’s not talk about what “fault output PIN” means.

Whether the open drain pin can drive the transistor does not depend on the open drain tube, but on the pull-up resistor of the tube.

In addition, the question of whether it can drive transistors is also vague. The base drive current of a low-power transistor may be tens of microamperes or even several microamperes, while a high-power transistor may require several milliamperes or even tens of milliamperes or hundreds of milliamperes.

chunyang

OD output can only provide sink current, so it is obvious that the external transistor can only be driven by a PNP tube. Whether it can be driven depends on whether the base current required by the transistor matches the sink current parameter of the OD type IO. If the external transistor is an NPN tube, the OD type IO cannot be driven, and the base current must be provided by an external pull-up resistor. The OD type IO only acts as a bypass switch.

小太阳yy

chunyang posted on 2022-4-28 19:23 OD output can only provide sink current, so it is obvious that the only external transistor to drive is PNP transistor. Whether it can be driven depends on the base current required by the transistor and the OD type IO ...

Some chips have internal pull-ups on their OD outputs, so there is no need to configure external pull-ups.

maychang

小太阳yy posted on 2022-4-29 08:24 Some chips have internal pull-ups on their OD outputs, so there is no need to configure external pull-ups

"Some chips have internal pull-ups on their OD outputs, so there is no need to configure external pull-ups."

If the chip is configured with a pull-up inside, it is not an OD output.

As for whether external pull-up is needed, it depends on the specific situation. For example, in the 51 single-chip microcomputer, all ports except P0 are equipped with pull-up inside the chip, but the pull-up current is very small. If a larger driving capability is required, an external pull-up resistor must be configured.

chunyang

小太阳yy posted on 2022-4-29 08:24 Some chips have internal pull-ups on their OD outputs, so there is no need to configure external pull-ups

Once there is an internal pull-up, it is no longer an OD output. The O in OD means open.

chunyang

If you mean weak pull-up IO driving NPN tube, you need to pay attention to the IO pull current parameter. If it is not enough, you can use external pull-up resistor to enhance it, but you need to pay attention to the IO sink current parameter at the same time, so as to avoid the external resistor value being too low and causing the transistor to fail to turn off when the IO outputs logic 0.

小太阳yy

maychang posted on 2022-4-29 08:46 "Some chips have internal pull-ups for OD output, so there is no need to configure external pull-ups." If the chip has internal pull-ups, it is not an OD output...

OK, got it. Thanks.

小太阳yy

chunyang posted on 2022-4-29 13:08 If the OP is talking about weak pull-up IO driving NPN tube, you need to pay attention to the IO pull current parameter. If it is not enough, you can enhance it by adding an external pull-up resistor, but you need to...

OK, got it. Thanks.