Does anyone here can help me with TSM109, which are 2 comparators? My question - are these open-collector comparators? Based on our tests, they look to be open-collector, but the datasheet doesn't say anything about it. Thank you for your attention!

[MasterT]

Data sheet says :

High Level Output Current (Vid = 1V) 30 150 nA

so basically it's not open collector, weak current of the high side may be sufficient to drive CMOS logic inputs. To improve speed and drive capability you free to set pull-up R , just watch the current limits

Output Sink Currrent Vid= 1V, Vo = 1.5V 10 20 mA, minimum is correct value

[LCao.3]

Hi MasterT,

Thank you very much for addressing my question, and what you said makes sense. So the comparator has very weak driving capability. In our circuit, it is driving a MOSFET of 2N7002, and the output stays about 0 when it's supposed at high. I would guess the gate leakage current exceeds the maximum current limit of IOH.

[Peter BENSCH · Accepted solution]

Well, the TSM109 was discontinued a long time ago. But it does indeed have open-collector outputs, which are better suited for low-active driving. 

In fact, the most sensible thing to do is to add the pull-up resistor mentioned above, which retains the logic.

You could also replace the 2N7002 with a p-channel MOSFET, which then inverts the whole logic, but you still need the pull-up resistor, now to turn off the MOSFET.

Good luck!

Regards

/Peter

[LCao.3]

Hi Peter,

I am very glad that finally someone from ST confirmed that TSM109 has open-collector outputs, and really appreciate your inputs.

Kind regards,

Liyu

[Peter BENSCH]

Great!

If the problem is resolved, please mark this thread as answered by selecting Select as best under your preferred answer. This will help other users find that answer faster.

Regards

/Peter

[Uwe Bonnes]

You can find out that the part is open collector from the condition to measure 'tre' Response time. The condition is "RL= 5.1k connected to VCC+".