Z8F2480 Datasheet, PDF (7/24 Pages) Zilog, Inc. – Load current up to 3 amps

Z8F2480 Power Monitor with an eZ80F91 Webserver
Reference Design
period immediately after the switch is toggled to allow for one initial period measurement
and to synchronize to the positive half-cycle of the FWR amplifier output. During the next
eight AC periods, individual measurements of the positive and negative FWR amplitudes
are averaged together, as are the number of IPO timer ticks between the peak HWR volt-
age (reference) and positive peak FWR amplifier output to determine the phase of the
FWR signal. After eight sets of samples have been averaged with Switch U5-A in the volt-
age position and eight sets of samples have been averaged with Switch U5-A in the current
position, the phase shift between voltage and current is calculated by subtracting the load
current tick delay (i.e., the I-phase) from the AC voltage tick delay (V-phase) to determine
the phase shift between the FWR voltage and FWR current signals.
Firmware running on the Z8F2480 MCU constantly performs these measurements and
updates the average AC period, input voltage, load current, and phase shift between peak
load voltage and current approximately every 18AC periods (or about 3 times per second).
The eZ80F91 Webserver Module contains a web page that displays the last set of AC mea-
surements obtained by the Z8F2480 MCU. These measurements are transmitted over the
optically-isolated I²C bus established through U4. The eZ80F91 Webserver Module is the
I²C Master, and polls the Z8F2480 MCU (operating as the I²C slave) to obtain new mea-
surement data. I²C requests can be initiated by this Master at any time; however, the
Z8F2480 MCU only responds to requests for AC measurements when it is otherwise idle.
If the Z8F2480 MCU is actively performing a measurement or updating an average, the
I²C request remains pending until the active AC measurement operation/calculation com-
pletes. After obtaining the raw measurements, scripts on the web page convert the data
into a human-readable format and display the results. A sample of the measurements dis-
played on the web page is shown in Figure 5.
RD002702-0814
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