TPS24751 IMON Current

I will recheck the factor of 16.17 written in the EVM user guide. For the EVM;

Ichannel / Vrimon = Rset / (Rsense * Rimon) = 51.1 / (0.002 * 1550) = 16.48

Please try 16.48 as the factor and let me know if this provides better correlation to your results.

The 16.48 factor is even worse. For example the I am using a BK Precision electronic load adjusted to 5A load CC and EVM is powered from 12VDC supply (Lead Acid battery ). The voltage  of 0.332 VDC is measured on Rimon which gives us a 16.48*0.332 = 5.471A current. I rechecked the current using the precision Fluke 8846A DMM and the result is the same, as the load settings - 4.999A. 

Sorry about that, Alex. I will have to involve design engineering to help understand what the problem might be.

But, as a data point I measured 0.376V on the EVM with 6.000A passing through the channel. This gives a factor of ~15.96 which is still quite a ways from your measured factor (4.999 / 0.332 = 15.06).

If possible, can you measure the R values of Rset and Rimon on your EVM (and verify the markings are for a 0.002 ohm Rsense)? It is possible that the EVM shop stuffed incorrect values, but they do test this during production.

The Rsense is marked as 0.002, Rset is 50.9 , Rimon is 1582.0 Ohm 

Thanks Alex.

I had misread the EVM user guide schematic for Rimon as 1550 but it is really 1582. Using 1582, the factor calculates as 16.17 (theoretical, but was close to what I measured on the EVM).

Can you confirm your load current by measuring the dc milli-volts (use meter in mV mode)  from TP6 on the EVM to R1 (Vcc side at solder joint)?

Yes, that's what I did exactly .The measured voltage values above made with bench DMM.

Again, I rechecked every element's value on the EVM, measured all possible voltages and currents - the error is consistent .I rechecked all the measurements twice ,with two different DMMs - the results are equal .

I rechecked again the voltage across the Rsense with different loads and the results are perfectly correct:

For 10A load VRsense = 19.98 mV; for 5A load VRsense = 9.97mV, for 1A load  VRsense = 2.01 mV.

I'm sorry to bother you for more data, but can you provide the following additional measurements (at known load current) for our analysis?

VSET - VSENM (DMM); measure the voltage drop from the SET to the SENM pin

Vrset – measure the drop across Rset directly

VIMOn – measure the voltage on the Vimon pin.

Iload = 1.00A

Vset=11.1736V

Vin=11.1740V

Vin-Vset = 2.92mV (exact measurement)

Vrset = 2.715mV (across R7 in EVB )

Vimon = 84.1mV

Alex,

Can you please share the waveform (ILOAD vs VIMON) or (Vsense vs VIMON)?

regards,

-vishal

See attached Excel file

IMON.xlsx

Hi People,

is there any resolution for this issue?

How has the story finished  at the end?

I am going to use the same IC in our application ...

BR,

Josko

Hi Rakesh,

The System will be for the nominal Input voltage 12V DC and maximum 10A. Actually, it will be a replacement for 10A automotive MINI fuse (LITTELFUSE 0297010.WXNV).  
Input voltage limiting range will be from 10V to 14V and operating temperature up to +50°C.  The 20A Current peaks however may occur, but their duration till now is not known.
How much Peak current could the TPS2475x handle?   

Actually, the 90% from EVM can be reused. The only concern is 18V max Input voltage of the TPS2475x eFuse because some can connect Laptop's power supply to this Input. And those have usually 19V output.   This means that TPS2475x should withstand 20V in off state (internal FET will be turned off for voltages above 14V).

BR,

Josko