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TL331-Q1: Please review the schematicof TL331-Q1, and have some questions

Chase Jeong
Mastermind 8065 points
Part Number: TL331-Q1
Other Parts Discussed in Thread: TL331LV-Q1

Tool/software:

Dear TI experts,

My customer drew tieht schematic with TL331-Q1. Could you review this schematic?

And here are more questions;

1. Is it okay to apply 0.5V~4.5V to HV_VDC_D?

1-1. Is there any limitation applying 5VLV if I apply 0.5V~4.5V to HV_VDC_D? (i.e., I should apply larger than 1.5V if I want to apply 0.5V~4.5V to HV_VDC_D.) 

2. If I change 5VLV(real 5V) to 13VLV(real 12V), Could you expect the output voltage HVFLT_OV?

2-1. Is output voltage changed depends on the input voltage HV_VDC_D?

Please check this issue. Thanks.

Best regards,

Chase

  • 0
    Guru 319020 points

    The TL331-Q1 has a limited common-mode input voltage range; with a 5 V supply, you must not use input voltages above 3 V.

    Using a 12 V supply would work. But for low-voltage applications like this, you should use a low-voltage comparator like the TL331LV-Q1.

  • 0 in reply to Clemens Ladisch
    TI__Genius 12545 points

    Hi Chase,

    1. Is it okay to apply 0.5V~4.5V to HV_VDC_D?

    No, you can't apply 0.5V to 4.5V on HV_VDC_D. As Clemens said, this comparator has an input common mode voltage range of VCC - 2V = 3V. If you have HV_VDC_D range from 0.5V to 4.5V, it's possible for you to have both inputs above the input common mode voltage range and the output of the comparator may be incorrect.

    1-1. Is there any limitation applying 5VLV if I apply 0.5V~4.5V to HV_VDC_D? (i.e., I should apply larger than 1.5V if I want to apply 0.5V~4.5V to HV_VDC_D.) 

    Yes, you need to increase the 5VLV such that you won't have a situation where both inputs are above the input common mode voltage range. Alternatively, you can change the switching thresholds at the non-inverting terminal to ensure that that terminal is always within the input common mode voltage range. That way, you can apply 0.5V to 4.5V to HV_VDC_D because you'd have the one input within the input common mode range conditions (see section 7.2.2.1 Input Voltage Range in the TL331-Q1 datasheet).

    Could you please elaborate on what question 2 and 2-1 mean? I'm unsure of what you are referring to there. The output voltage will be higher because the pull-up voltage will change from 5V to 12V.