Datasheet
78M6610+PSU Data Sheet
2 Functional Description and Operation
This section describes the 78M6610+PSU functionality. It includes measurements and relevant
calculations, alarms, auxiliary functions such as calibrations, zero-crossing, relay control, etc.
A set of input (write), output (read) and read/write registers are provided to allow access to calculated
data and alarms and to configure the device. The input (write) registers values can be saved into flash
memory through a specific command. The values saved into flash memory will be loaded in these
registers at reset or power-on as defaults.
2.1 Voltage and Current Inputs Conditioning
The sensor input voltages are digitized using a single integrated second-order delta-sigma A/D converter.
The analog front-end includes a temperature sensor whose output is digitized and used for temperature
(gain) compensation.
SINC
3
DECIMATOR
AIP
CROSS
POINT
∆Σ
MODULATOR
PRECISION
REFERENCE
IA
_ RAW
VA_
RAW
v
F
ADC
DELAY
COMP
+
250
mv
ADC
X
X
X X
i
AIN
CT PHASE
COMP
ON-
CHIP
TEMPERATURE
SENSOR
Temperature
Compensation
AVP
DIE_ TEMP
GAIN CORRECTION
SIGNAL
CONDITIONING
AVN
ATEMP
2
Igain
Vgain
PhaseComp
X
X
Tgain
Toffs
HPFcoeffI
HPF
HPF
HPFcoefV
Figure 2-1: Analog Input Signal Conditioning
2.1.1 High Pass Filters (HPF) and Offset Correction
The high-pass filters (HPF) in Figure 2-1 and Figure 2-2
can remove any DC from the signal paths and
consequently from power and RMS calculated values. The HPFs work by subtracting the value of the
offset register (Voffs, Ioffs) from the corresponding voltage or current input. The offset registers can be set
by the user, by an automatic calibration routine or adjusted dynamically by the FW.
HPF
HPFcoef
-
X
∑
N-1
n=0
offs
N
+
Figure 2-2: HPF
2.1.2 Phase Compensation
A phase compensation register is provided to compensate phase errors introduced by current
transformers (CT) or external filters. The amount of phase shift is set by the PhaseComp register as a
fractional number of ADC samples with a total range of +/- 4 ADC samples (roughly +/- 20 degrees for a
60Hz line frequency).
10 Rev 3