TLV2171: How to decrease TLV2171 Iq

Part Number: TLV2171
Other Parts Discussed in Thread: TLV9102, OPA2991, OPA2990, TLV9152, OPA2244, TLV9042, TLV9151

Hi team,

My customer use TLV2171 to sense battery voltage, and they want to decrease the TLV2171 Iq consumption during the off-work status beacuse TLV2171 always connect to the battery even though in off-work status.

Support Need: TLV2171 peripheral circuit design to decrease the Iq consumption

Looking forward to your reply, thx

  • Hi Chen,

    Good question! To make things easier to design as well as well as reduce the number of external circuits needed to do this, I recommend choosing a device with built in shutdown capabilities. The TLVx171 family does not have that so if you want to try that, then I would recommend taking a look at the TLV9102 or the TLV9152. If you need something to support an even higher supply voltage then I recommend using the OPA2990 or OPA2991. 

    A follow up question for you is, why would you need to use a high voltage device to sense the battery voltage? If the output of your op-amp is going to an ADC, then that ADC is likely a lower voltage device! 

    Best Regards,

    Robert Clifton

  • Hi Robert,

    Very appreciate your quick reply. it's a good idea to use a device with built in shutdown capability, nice~ i will recommend it to my customer Slight smile

    Btw, you are totally right, the Amps output to ADC, and customer use TLV2171 with 5V power supply.

    Now i recommend TLV9042IDR  Iq=10μA  and TLV9151SIDBVR  to customer.

    Lastly, i have a question, Does the devices Iq parameter is fixed regardless peripheral circuit design changed? 

    Looking forward to your reply.

    Have a nice day.

  • Hi Chen,

    While quiescent current can very slightly from device to device as well as change across different temperatures and/or supply voltages, the peripheral circuit shouldn't change quiescent current. 

    Best Regards,

    Robert Clifton

  • Hi Robert,

    update.

    My customer test the TLV9042IDR & OPA2244, and they found that there is no large difference of battery quiescent current consumption, comparing with TLV2171 in off-work status.

    The amp circuit shows as below

    And they want to identify if the input back to back diode will affect the Iq consumption.

    Could you please help to check the reason why this is no more difference between TLV2171 and TLV9042?

    And they want to identify if TLV9151 is useful to reduce battery quiescent current consumption.

    Thx

  • add.

    Customer didn't test TLV2171 & TLV9042 Iq, just test the battery quiescent current consumption, which show no much difference.

    In this battery voltage sensing application, customer want to know if the low Iq amp could reduce the battery quiescent consumption?

    Thx, looking forward to your reply.

  • Hey Chen, 

    Can you provide what voltages are expected at BAT+ and BAT-? 
    Additionally what are the resistor and capacitor values that are missing? Specifically what are the values for R5, R6, R7, R8, R9, and C1? 

    From the customer's description it seems that testing between the two op amps, there is not a difference in the system's Iq? 
    If this interpretation is correct, the op amps Iq must be so low to the overall Iq of the system. I would focus on lowering the overall system Iq. 

    All the best,
    Carolina

  • Carolina,

    Sorry for the mix expression. Customer want to reduce the battery 12V quiescent current consumption in the machine off status, in which the power of amp is off.

    But the quiescent current consumption is about 200uA with TLV2171, and after replacing TLV9042 the quiescent current is 190uA.

    So, customer want to get the support of reducing the quiescent current, and i recommend to increase the R1~R4,and R8, to decrease the current. And add RC to eliminate noise caused by increased resistance.

    Do you have another good advices? thx

  • Hey Chen, 

    Can you please provide the values of R5, R6, R7, R8, R9, and C1? 

  • I need to double check with their values Slight smile

    Do you have better solution about this case? Thx 

  • Hey Chen, 

    The Iq seems really high to me, therefore I would like to know the values to see if I get the same results. 
    Implying that there is something else going on here that is not just the op amps. 

    The only obvious solution to dramatically decrease the Iq is what Robert already suggested which is to use shutdown devices. The TLV904X family is also available in shutdown. 

    All the best,
    Carolina

  • Hey Caro,

    I have to notice that in this situation, the power of amp is off. But the battery quiescent current consumption is very high.

    I don't think it's the op amps effect, may be the R1 R2 R3 R4 is too small , which cause a high current consumption?

    In this way, does the shutdown would works to reduce the current, even though no power supply for amp?

  • Hi Chen,

    I'm concerned that they are turning off the power supplies in to have the op-amp act in a "shutdown" state since the ESD protection might be turning on here, hence why even though the op-amp is turned off, there's still current consumption. Please refer to this document:  Op Amps with Special Input Protection, as well as this blog: (+) So what exactly is an Op Amp shutdown pin supposed to do? - Precision Hub - Archives - TI E2E support forums

    This is why we recommend to be using an op-amp with the shutdown feature rather than pulling the power supply from the op-amp to have it act like it's in a shutdown state! 

    Best Regards, 

    Robert Clifton 

  • Hi Robert,

    Customer want to decrease the battery quiescent consumption in the shutdown state, in this state, customer found that the battery output current is 200μA;

    After increasing the circuit resisters with 5x, the current decrease to 34μA; but it's still too big.

    So customer want to identify if the TLV2171 input protect back to back diode cause the big current?

  • Hi Chen,

    Do you know what the customer's target current consumption is? 

    Did you inform the customer our concerns with them turning off the power supplies while still having an input signal? 

    It's possible that the TLV2171 input protection diodes are the cause of this current as having the op-amp have voltage on the input pins while the power supplies are 0V. We actually talk about this in the datasheet in section 7.3.3 Electrical Overstress. Here's the section that is likely happening to their board:

    "Another common question involves what happens to the amplifier if an input signal is applied to the input when the power supplies (V+ or V–) are at 0 V. Again, this question depends on the supply characteristic when at 0 V, or at a level below the input signal amplitude. If the supplies appear as high impedance, then the input source supplies the operational amplifier current through the current-steering diodes. This state is not a normal bias condition; most likely, the amplifier does not operate normally. If the supplies are low impedance, then the current through the steering diodes can become quite high. The current level depends on the ability of the input source to deliver current, and any resistance in the input path." 

    It's not only the input resistance but also the supply pins impedance that will have an affect on how much current gets pulled! 

    Best Regards,

    Robert Clifton 

  • Robert,

    Impressive, thx for your explain.

    I notice that the TLV9151 stand high impedance state when shunt down.

    So i want to know if TLV9151 will still cause quiescent consumption when shunt down?

    Thx

  • Hi Chen,

    I'm assuming we are talking about the TLV9151S which supports shutdown mode. When in shutdown the op-amp will still consume about 20uA of current so just take note of that. But that's from it's supply rails not the inputs of the amplifier! 

    Best Regards,

    Robert Clifton