Other Parts Discussed in Thread: THS4551, ADS8695, INA240, TINA-TI, OPA189, OPA388
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Thank you Kenith. I hope my design would be better with this part.
Do you have any suggestions for alternate part with high precision? Because I have to monitor current in high side from 0 to few Amperes with 10uA resolution. 20bit ADC would be suffice to my design. so that I need to sense by current sense resistor and give to ADC with some amplification. But the amplifier itself also has some offset right? for example of figure 111 in datasheet ADS8902B has the amplifier which posses 375uV offset. so can you please suggest the suitable amplifier part? or suitable design?
Hi Keith,
Thank you for your suggestion,
Due to the concern the power dissipation of sense resistor, I plan to put the resistor value as 40mOhm. so for 10uA step the drop across resistor is only 0.4uV for one step, in this situation this 0.4uV change will be sensible by the ADC?
I simulated the analog front end shown in Figure 111 of ADS8902B datasheet in separate with this 40mOhm resistor in the Tina-TI software. but the change of 0.4uV is not given any effective change in the output. the output changes atleast for 250uV drop. so what should I do?
I also simulated the front end as shown in Figure 105 of ADS8902B Datasheet. It gives perfect change of voltage in 0.4uV range but still it is confusing that whether the ADS8902B will sense this much change? for full scale the voltage is only 140mV, but for map this to a good reference(ex:4 or 4.5V), I should amplify the signal. But i didn't find good amplifier. for map to 4V i need 28Gain, for 4.5v ref, i need 32gain. What should I do?
the INA240 itself have fixed gains like 20,50,100,200 but the output is unstable in first 50mA(resistor drop 2mV). The changes also gives for 20uA once. But I need the changes for 10uA.
and I have plan to amplify the drop with either OPA388 or OPA189 but the bandwidth of them are not satisfied. I require 500KHz. buth those are gives stable gain for few frequencies only. so can you please suggest anything?
Hi keith
Please tell me that is it possible to change the gain of the analog front end shown in the figure 105 and figure 111 of ADS8902B. Or I should design a separate amplifier section before the analog front end? please suggest any application circuit regarding this.