78M6610+LMU Data Sheet
RMS Current
The 78M6610+LMU reports true RMS measurements for current inputs. The RMS current is obtained by
performing the sum of the squares of the instantaneous current samples over the accumulation interval
and then performing a square root of the result after dividing by the number of samples in the interval.
An optional “RMS offset” for the current channels can be adjusted to reduce errors due to noise or system
offsets (crosstalk) exhibited at low input amplitudes. Full scale values in the IxRMS_OFFS registers are
squared and subtracted from the accumulated/divided squares. If the resulting RMS value is negative,
zero is used.
IxRMS_OFF2
Instantaneous
N-1
Current (Ix)
Ix2_SUM
Ix2
X
Ix_RMS
−
∑
N
n=0
Figure 20. RMS Current Computation
Minimum Current
The device includes a squelch feature to report zero current for no-load conditions. When the RMS
current value (checked at each accumulation interval) falls below the threshold (IRMS_MIN), the device
will report zero current and prevent the continued accumulation of energy.
Register
Description
If measured Ix_RMS is less than value in IRMS_MIN, then Ix_RMS
is squelched and energy accumulation stops
IRMS_MIN
Crest Factor
The crest factor outputs capture the result of the equation Ix_CREST = Ix_PEAK / Ix_RMS for the most
recent accumulation interval. They have a range of 0 to 256.
30
Rev 0
MAXIM [ MAXIM INTEGRATED PRODUCTS ]
