This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

The TPS40400EVM-351 1.2V-EVM have large inaccuracy in current reading while using PMBus read-out

Other Parts Discussed in Thread: TPS40400EVM-351

Dear Sir,

I've been playing with the TPS40400EVM-351 1.2V-EVM and monitor the current Iout reading while change the load from slight to heavy. This caused serious current inaccuracy in PMBus read. The following Word document showing the monitor readings. In that Word document, the green rectangular form is read by DVM, but the red rectangular form is read by PMBus. Obviously, There are many inaccuracy in PMBus read while slight load. Could anyone tell me where my wrong is ? Please help and thanks!

TPS40400EVM-351 Board    1.2V PMBus Read Test Report
 
Item
   Meter Read
PMBus Read
Error
Vout
Iout
Pout
Vout
Iout
Pout
Vout
Iout
V
A
W
V
A
W
V
%
A
%
1
1.204
0.0
0.00
1.188
0.06
0.07
-0.016
-1.35
0.060
---
2
1.204
0.5
0.60
1.219
0.06
0.07
0.015
1.23
-0.439
-87.97
3
1.204
1.0
1.21
1.188
0.06
0.07
-0.016
-1.31
-0.949
-94.05
4
1.203
1.5
1.81
1.203
0.06
0.08
0.000
-0.03
-1.444
-96.01
5
1.203
2.0
2.42
1.188
0.06
0.07
-0.015
-1.25
-1.954
-97.02
6
1.202
4.0
4.82
1.188
1.75
2.08
-0.014
-1.13
-2.261
-56.37
7
1.200
6.0
7.21
1.188
3.69
4.38
-0.012
-1.01
-2.314
-38.54
8
1.198
8.0
9.59
1.188
5.75
6.83
-0.010
-0.87
-2.251
-28.13
9
1.197
10.0
11.98
1.203
8.00
9.36
0.006
0.51
-2.012
-20.10
10
1.196
12.0
14.36
1.203
10.00
12.11
0.007
0.62
-2.009
-16.73
11
1.194
14.0
16.72
1.188
12.25
14.36
-0.006
-0.53
-1.754
-12.52
12
1.193
16.0
19.09
1.188
14.69
17.74
-0.005
-0.42
-1.315
-8.22
13
1.192
18.0
21.45
1.188
17.06
20.49
-0.004
-0.30
-0.941
-5.23
14
1.190
20.0
23.80
1.188
19.69
23.46
-0.002
-0.18
-0.310
-1.55
 
 
 
Average
-0.005
-0.43
-1.421
-43.26
Max.
0.015
1.23
0.060
-1.55
Min.
-0.016
-1.35
-2.314
-97.02

 
TPS40400EVM-351 Board    1.2V PMBus Read Test Report
 
Item
   Meter Read
PMBus Read
Error
Vout
Iout
Pout
Vout
Iout
Pout
Vout
Iout
V
A
W
V
A
W
V
%
A
%
1
1.204
0.0
0.00
1.188
0.06
0.07
-0.016
-1.35
0.060
---
 2
1.204
0.5
0.60
1.219
0.06
0.07
0.015
1.23
-0.439
-87.97
3
1.204
1.0
1.21
1.188
0.06
0.07
-0.016
-1.31
-0.949
-94.05
4
1.203
1.5
1.81
1.203
0.06
0.08
0.000
-0.03
-1.444
-96.01
5
1.203
2.0
2.42
1.188
0.06
0.07
-0.015
-1.25
-1.954
-97.02
6
1.202
4.0
4.82
1.188
1.75
2.08
-0.014
-1.13
-2.261
-56.37
7
1.200
6.0
7.21
1.188
3.69
4.38
-0.012
-1.01
-2.314
-38.54
8
1.198
8.0
9.59
1.188
5.75
6.83
-0.010
-0.87
-2.251
-28.13
9
1.197
10.0
11.98
1.203
8.00
9.36
0.006
0.51
-2.012
-20.10
10
1.196
12.0
14.36
1.203
10.00
12.11
0.007
0.62
-2.009
-16.73
11
1.194
14.0
16.72
1.188
12.25
14.36
-0.006
-0.53
-1.754
-12.52
12
1.193
16.0
19.09
1.188
14.69
17.74
-0.005
-0.42
-1.315
-8.22
Slight  Load
 
Heavy  Load
 
13
1.192
18.0
21.45
1.188
17.06
20.49
-0.004
-0.30
-0.941
-5.23
14
1.190
20.0
23.80
1.188
19.69
23.46
-0.002
-0.18
-0.310
-1.55
 
 
 
Average
-0.005
-0.43
-1.421
-43.26
Max.
0.015
1.23
0.060
-1.55
Min.
-0.016
-1.35
-2.314
-97.02