Z8F2480 Datasheet, PDF (4/24 Pages) Zilog, Inc. – Load current up to 3 amps

Z8F2480 Power Monitor with an eZ80F91 Webserver
Reference Design
Current sense resistor R8 provides a signal for the MCU to determine a load current ampli-
tude, as well as a current zero crossing point to determine the phase shift between the AC
voltage and the load current.
Figure 4 shows the location of components on the Power Board.
Figure 4. Location of Components on the Power Board
To minimize power dissipation on the current sense resistor, its resistance value is set very
low, and a signal conditioner with a detector/amplifier (U2A–C) and a MOSFET (Q3) is
used to increase the signal to an acceptable level for the MCU.
A comparator (U2D) is used to provide overvoltage/overcurrent information to the
Z8F2480 MCU.
An optically-isolated I²C interface (U4) creates a communication channel between the
Power Board’s Z8F2480 MCU and the eZ80F91 Webserver Module connected to J3.
A power jack (J7) is used to provide +5 V from a wall adapter to drive the eZ80F91 Mod-
ule. This voltage is reduced to 3.3 V by a linear voltage regulator (U1) and is applied to the
eZ80F91 Module through connector J3, to which the Module is mounted.
RD002702-0814
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