2mV of offset voltage on LTC2053 output

Question

LTC2053 datasheet promises typical input offset of -5uV and maximum of +- 10uV, which means the typical output offset voltage with the gain of 20.1 would be 
 -5	imes20.1=-100.5uV

and 
 \pm10	imes20.1=\pm201uV

maximum. However, I see almost a 2mV (2000uV) of output offset voltage which violates the spec. Can anyone provide a possible explanation for this 2mV offset? 
 Here is the schematic of the circuit I'm working with: 
 
 Note: For pin 1, EN = SYNC which is left floating 
 And here is how the circuit is setup in reality: 
 
 V_DUT and I_DUT are connected through the screw block (J101). R1 and R2 have 0.1% tolerance. The inputs to the amplifier are connected to channel 1 of PAC1942 evaluation board as shown here: 
 
 R111, R112, and C100 are all depopulated and twisted paired wires are directly soldered to the corresponding pads. 
 The offset voltage was measured with Keysight 34461A 6 1/2 Digit Multimeter when the IC is powered with 3.3V and V_DUT is 1V while I_DUT is disconnected. Across R100 (4mOhm sense resistor) and the inputs of the amplifier, U1 (IN+ & IN-), 0.0000mV were measured; however, the output was measured to be 1.99mV. 
 I repeated the measurements with different I_DUT setting drawing 0.01A, 0.002A, ... 0.3A and the error (calculated as: 
 Error=Measured-Expected

) seem to be consistently around 2mV until I_DUT increases past 50mA as shown in the data below:

I_DUT (how much current the load should draw in A) 
 I_DUT (how much current the load actually draw in 0A) 
 V_SENSE(at R_SENSE in mV) 
 V_SENSE(at op-amp input in uV) 
 V_OUT (mV) 
 Expected V_OUT (mV) 
 Error (measured - expected)

0.0000 
 0 
 0.0000 
 0.0000 
 1.9900 
 0 
 1.9900

0.0100 
 0.006 
 0.033 
 0.0321 
 2.6100 
 0.4824 
 2.1276

0.0200 
 0.016 
 0.7150 
 0.7100 
 3.3700 
 1.2864 
 2.0836

0.0300 
 0.026 
 0.1091 
 0.1086 
 4.1490 
 2.0904 
 2.0586

0.0400 
 0.036 
 0.1482 
 0.1456 
 4.9350 
 2.8944 
 2.0406

0.0500 
 0.046 
 0.1855 
 0.1836 
 5.6800 
 3.6984 
 1.9816

0.1000 
 0.096 
 0.3750 
 0.3710 
 9.4800 
 7.7184 
 1.7616

0.1500 
 0.146 
 0.5630 
 0.5625 
 13.3200 
 11.7384 
 1.5816

0.2000 
 0.196 
 0.755 
 0.7528 
 17.1000 
 15.7584 
 1.3416

0.2500 
 0.246 
 0.9430 
 0.9450 
 20.9600 
 19.7784 
 1.1816

0.3000 
 0.296 
 1.1340 
 1.1338 
 24.7700 
 23.7984 
 0.9716

Note that the error reduces as I_DUT increases.

Arsol · Accepted Answer

Hi KennyWizard 
 Thank you for getting back to me. 
 Your application is trying to configure the part with a differential output. 
 But LTC2053 is designed for single-ended output only , if you are trying to create a circuit with a differential output. Then, we have a fully differential PGIA in our portfolio, which I can recommend: AD8231 , LTC6373 , ADA4254 , and ADA4255 . 
 I recommend using this typical configuration for a single supply mode: 
 
 Hope this helps. 
 Regards,)

Arsol · Answer

Hi KennyWizard 
 Thank you for reaching out to the team and sharing your inquiries. 
 To further assess your questions and be able to share the best recommendations, we would like to know more about the intended applications and design parameters. 
 Please share the following items: 
 
 The Intended Applications : what is the purpose of this circuit? i.e., as a Current source, Current sense, simple instrumentation amplifier( gaining up the differential inputs), etc.? 
 The desired Gain is 20.1 ? From the circuit: (19.1k/1k) +1 
 This part is single-ended output; If you are trying to create a circuit with a differential output. Then, we have a fully differential PGIA in our portfolio, which I can recommend; these are: AD8231 , LTC6373 , ADA4254 , and ADA4255 
 
 If you are trying to compute and measure the output offset voltage, I suggest shorting both inputs (-IN Pin2 and +IN Pin3) to Ground. Then, measure the output thru Pin7. 
 
 Regards

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2mV of offset voltage on LTC2053 output