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
|
||||
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
|