TMCS1101: Output offset error

Dino,

How low in current does the customer truly need to measure here? Given that they are looking at the A4 variant, I would assume that the current range they are looking to measure is either very small in scope, or small in magnitude, and they are hoping to amplify the output signal. Here's my take on each of these:

Small in Magnitude: Hall effect sensors are known to be inherently noisy, and the TMCS family isn't an exception. More importantly than the offset voltage, if you examine the noise density of thA4 variant, you can calculate that at full bandwidth, the device will exhibit noise characteristics of 25.4mArms, and 168mApp (6.6x for a 99.9% distribution). This can be improved by reducing the device BW, but it is something the customer should consider in their evaluation. If they are in fact trying to implement these devices to measure small magnitudes of current at high resolution, they may face challenges here, due to not only the above issues, but the offset as you mention in your initial post. If this is the case, however, can you share what is drawing the customer to the Hall-Effect devices rather than a traditional shunt here? Do they require isolation here?

Small in scope: Provided the customer isn't actually attempting to measure in the mA level, and simply wants mA resolution at a smaller range of higher amperage, these devices should be fine, and this challenge will ultimately fall to the ADC that they choose and how the analog measurement is quantized into their digital environment. They would need to ensure that their ADC choice uses an ENOB large enough to meet their desired resolution, and that the interfacing buffer (or lack thereof) is sufficient to drive the ADC to within 1/2 LSB in the designed acquisition time. 

The customer may wish to read through our app note on best practices for these devices as well. 

Hello Carolus, 

Thank you for your kind explanation. 

The customer application is AC/DC power supply of Air purifier like below. 

- AC 110/220V, 50/60Hz

- output power : 60W 

- Isolation is needed(mandatory)   

As your comment, TMCS series doesn't seem to be a suitable solution for customer application due to Small in Magnitude. 

Could you recommend right solution(INA series or others) and application note to apply AC line current sensing or DC link line (over 300V) current sensing for customer application? 

Thank you. 

Hello Carolus, 

I am sorry to push you but please let me know your opinion regarding right solution(INA series or others) and application note to apply AC line current sensing or DC link line (over 300V) current sensing for customer application. please refer to the above customer application. 

Thank you.