TLV1824: Factors contributing to longer propagation delay

Hi Hori-san,

Are you able to provide any oscilloscope waveforms of the inputs and outputs to the TLV1824? Any schematics?

The significantly slower propagation delay may be due to a large underdrive in the input signal. This device family is quite sensitive to large voltage underdrive, so this family isn't recommended for applications where propagation delay is critical:

Hori Shota said:

Moreover, regarding the ability to handle 24V input and the existence of a 4-channel comparator, I believe there are currently no faster alternatives than the TLV1824. Is that correct? Are there any plans for new products to be released in the near future?

Are push-pull outputs a necessity? If not, you could potentially look at the TLV1704: TLV170x 2.2-V to 36-V, microPower Comparator datasheet (Rev. D)

The TLV183x and TLV184x Family of 40V, High-Speed Comparators datasheet (Rev. B) is the high-speed version of the TLV181x/TLV182x, though its currently only available in single and dual packages.

Hi HO-san,

Thank you for recommending high-speed comparators.

Regarding the TLV1824DR, based on the datasheet, I understand that the propagation delay due to overdrive voltage should be no more than approximately 800ns. In our current circuit configuration, the comparator output is open-drain, pulled up to 24V through a 20kΩ resistor. The output is connected to the IN2+ input of TLV1824DR, and the load capacitance is approximately 200pF. We are observing a delay of about 8µs from the moment the input goes high until the output voltage begins to change. Could you help us identify what might be causing this extended propagation delay? Is this delay possibly related to the open-drain configuration?

Best regards,　shota

Hi Shota-san,

Could you please show a schematic of the configuration? It's hard to visualize all of the connections without a schematic, especially if it's a four channel device. Could you show an oscilloscope screenshot showing the voltage swings?

The 800ns you're referring to is probably from the Typical Characteristics plots on the data sheet. Those plots show propagation delay with a varied overdrive. This family of devices have sensitivity towards large voltage underdrive. For example, if IN- = 12V and IN+ swings from 0V to 13V, there is a 1V overdrive and a 12V underdrive. This device is sensitive to large underdrive. Are there large underdrive in your tests?

Hi HO-san,

Regarding the circuit diagram, I am currently checking with my customer and will follow up once I receive their response. In the meantime, I have another question. For the open-drain output, the datasheet specifies the propagation delay time from high to low. However, I could not find any information regarding the propagation delay time from low to high. Could you kindly let me know the delay time for the low-to-high transition?

Thank you very much for your continued support.

Best regards, Shota

The circuit diagram will be ready shortly. I'm still waiting for your response regarding the low-to-high transition of the open-drain.　Best regards, Shota

Hi Shota-san,

We usually have a TPLH specification for open-drain outputs at a specific pull-up resistor and load capacitance, but it seems like it wasn't done for this device.The TPLH is dependent on the load capacitance and the pull-up resistor. You could estimate the TPLH of an open-drain device by adding the propagation delay of ~420ns + RC time constant of output cap and pull-up resistor.

Hi HO-san,

Hi,

I’ve prepared the schematic and will send it personally. I’ve also sent a friendship request—could you please confirm it?

Additionally, I have a few questions:

1. When are the 4-channel versions of TLV183x and TLV184x expected to be released?
2. Are there any comparators that are not sensitive to underdrive voltage?
3. Why is TLV1824 particularly sensitive to underdrive voltage?
4. Is LM339B sensitive to underdrive voltage as well?

Best Regards,

Shota

Hi Shota-san,

Friendship request accepted, please go ahead and share with me the schematic through direct messages.

1. There are currently no definitive dates on the release of the quad channel TLV1834 and TLV1844.

2. Underdrive directly affects propagation delay in all comparators, which is why we specify the input conditions in our propagation delay specifications; the level of sensitivity may be different than the TLV181x/TLV182x family which are especially sensitive towards large underdrives in TPLH. Higher speed devices (which are typically lower voltage) like the TLV3601 have propagation delays that are less sensitive to input underdrive.

3. Power consumption and speed are usually direct trade-offs in devices. The TLV182x being a low power device with 5uA of quiescent current per channel has this speed tradeoff when the input underdrive is large.

4. I'm not aware of the LM339B being as sensitive to underdrive as the TLV181x/TLV182x family, but please note that the LM339B has an input common mode voltage range that is not rail-to-rail (VCC - 2V).

Hi HO-san,

Thank you very much for your reply.

The TLV184x series datasheet no longer mentions sensitivity to underdrive voltage. Does this indicate that the device's performance has been improved?

Is the absence of the underdrive voltage specification due to the TLV184x having a higher quiescent current than the TLV1824?

Best Regards,

Shota

Hi HO-san,

Although there is currently no confirmed release date for the quad-channel TLV1834 and TLV1844, if there is a rough schedule available, could you kindly share it with us?

Best Regards,

Shota