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TLV1701-Q1: Application question confirm

Lanxi Li
Expert 6315 points
Part Number: TLV1701-Q1
Other Parts Discussed in Thread: TLV1701, TLV1821

Hello team,

My customer is reviewing the worst case calculate of TLV1701, please help review the questions as below.

1. How to understand the direction of input bias current? Can we understand that the Ib current is flowing into the comparator?  

2. How to judge the input bias current? So this related to the Input structure?

3. How to understand the Vo spec?

TLV1701 is an open-collector output. The output terminal is pulled up to the power supply VCC through a pull-up resistor. Does this deviation refer to the deviation from the pull-up power supply (the same voltage as the power rail of the comparator)? For example, if the pull-up power supply is 5V, in extreme cases, the output high-level VOH may reach 5-0.9=4.1V, and the output low-level VOL may reach 0.6V?

Best regards,

Lanxi

  • 0
    TI__Guru 54766 points

    Hello Lanxi,

    Remember that the rail-to-rail inputs are in parallel - the PNP and NPN input pair. So bias current changes directions around Vcc-1.2V. The PNP's work for the majority of the input range, and current flows OUT of the inputs towards ground. When the NPN's kick in, the bias current reverses.

    If V+ is greater than the pull-up voltage, then there will be up to 70nA flowing between the output and V+. This would limit the maximum value of the pull-up resistor.

    If output swing is an issue, please look at the TLV1821. It has picoamp bias currents and better VOL swing.