MAX78615+LMU Data Sheet
Current Input Configuration
The MAX78615+LMU supports multiple analog input configurations for determining the two load currents in a
split-phase AC circuit. The device measures the current of any two conductors and uses this information to derive
the load currents shown below.
IA
Conductor A
IN
Conductor N
IA= - IB - IN
IB= - IA - IN
Conductor B
IB
Figure 10. Current Input Configuration
Each calculated load current (IA and IB) is derived from the following function of the current input slots (S1 and S3)
and 2 pairs of multiplier values (M1 and M3). This function derives source currents IA and IB by summing S1 x M1
and S3 x M3.
S1
M1
+ Ix
S3
M3
Figure 11. Computing Input Current
The user sets the multiplier values for each current source in the CONFIG register using the model where a one (1)
value adds the input, a two (2) value adds two of the input, a minus one (-1) value subtract the input, a zero (0)
value does not include the input.
CONFIG Bits
Multiplier
Source
7:6
5:4
M3 M1
IB
3:2
1:0
M3 M1
IA
There are four choices for every M value as shown below.
Bit Values
00
01
10
11
M (multiplier) Value
-1
0
1
2
The output registers IA and IB are automatically scaled by a factor of 0.5 if M1 and M3 are both nonzero.
For example, by setting the multiplier bits as follows:
���� = +1 ∗ ��1 − 1 ∗ ��3
The effective content of the Vc register would result in:
(+1 ∗ ��1) + (−1 ∗ ��3)
���� =
2
This scaling is done to prevent the output register from overflowing.
Rev 0
21