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TLV4172: Common-mode voltage range

Hirotaka Matsumoto
Guru 27585 points
Part Number: TLV4172

Hi all

Would you mind if we ask TLV4172?

<Question1>
There is the description "The input range can be extended beyond (V+) – 2 V up to V+. See the Typical Characteristics and Application and Implementation sections for additional information."
What does it mean  "The input range can be extended beyond (V+) – 2 V up to V+."?
Common-mode voltage range should be range (V-) - 0.1 to  (V+) - 2V.
Is it possible to use (V-) - 0.1 to (V+)  with normal operation?

<Question2>
There is the description on the datasheet P1 as follows;
"The input can operate 100 mV below the negative rail and within 2 V of the positive rail for normal operation.
 Note that these devices can operate with a full rail-to-rail input 100 mV beyond the positive rail, but with reduced performance within 2 V of the positive rail."
In case of beyond common mode voltage range, we assume that the output will be saturated　with V+ or V-.
It is not normal operation. So, that's why, it is not "with reduced performance", right?

Kind regards,

Hirotaka Matsumoto


  • 0
    TI__Guru**** 159831 points
    Hirotaka-san,

    Figure 3 in data sheet is a clear picture of operation above VCC-2V.
    There won't be any problems like phase reversal , also called phase inversion, in the range within 2V of VCC.

    For input > VCC-2V, expect poor DC offset error, lower gain and slew rate.
    For input more than 100mV past either supply rail , expect out saturated.
  • 0 in reply to Ron Michallick
    TI__Genius 15410 points

    Hello Hirotaka-san,

    In addition to what Ron said, please see Table 2 in section 8.4.1 of the datasheet for typical performance within 2V of the positive supply.

    Thank you,

    Tim Claycomb

  • 0
    Guru 140200 points

    Hi Hirotaka,

    you wrote: "In case of beyond common mode voltage range, we assume that the output will be saturated　with V+ or V-.
    It is not normal operation. So, that's why, it is not "with reduced performance", right?"

    No. There will not be output saturation with V+ or V-.

    You asked: "Is it possible to use (V-) - 0.1 to (V+)  with normal operation?"

    Yes, but if input voltage enters the range (V+) - 0.2V ... (V+) the TLV4172 beginns to work less accurate. Have a look at figure 3 of datasheet, e.g.. You will see, that input offset voltage increases up to 50mV, when the input voltage is between +16V and +18V. For input voltages smaller than +16V, the input offset voltage is only 0.5mV typically. This is a huge difference! If this is a problem in your application, then you must not use the TLV4172.

    Kai