71m6543h-igtr/f Maxim Integrated Products, Inc., 71m6543h-igtr/f Datasheet - Page 94

• Manufacturer Part Number: 71m6543h-igtr/f
• Description: Energy Meter Ic
• Manufacturer: Maxim Integrated Products, Inc.

controlled by OPT_FDC[1:0] (I/O RAM 0x2457[5:4]), which can select 50%, 25%, 12.5%, and 6.25% duty
71M6543F/H Data Sheet
The OPT_TX output may be modulated at 38 kHz when system power is present. Modulation is not
available in BRN mode. The OPT_TXMOD bit (I/O RAM 0x2456[1]) enables modulation. The duty cycle is
cycle. A 6.25% duty cycle means OPT_TX is low for 6.25% of the period. The OPT_RX pin uses digital
signal thresholds. It may need an analog filter when receiving modulated optical signals.
If operation in BRN mode is desired, the external components should be connected to V3P3D. However,
it is recommended to limit the current to a few mA.
4.10 Connecting the Reset Pin
Even though a functional meter does not necessarily need a reset switch, it is useful to have a reset
pushbutton for prototyping as shown in
V3P3SYS (functional in MSN mode only), V3P3D (MSN and BRN modes), or VBAT (all modes, if a battery is
present), or from a combination of these sources, depending on the application.
Since the 71M6543F/H generates its own power-on reset, a reset button or circuitry, as shown in
only required for test units and prototypes.
94
Figure 36: External Components for the RESET Pin: Push-Button (Left), Production Circuit (Right)
V3P3D
VBAT/
increase the distance along the optical path.
With modulation, an optical emitter can be operated at higher current than nominal, enabling it to
For a production meter, the RESET pin should be protected by the by the external components
shown in
to the IC.
1k Ω
Figure
R
2
0.1µF
71M6543F/H
Switch
36, right side. R1 should be in the range of 100Ω and mounted as closely as possible
Reset
Figure 35: Connection for Optical Components
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OPT_RX
OPT_TX
R
V3P3D
10k Ω
1
Figure
100 pF
36, left side. The RESET signal may be sourced from
RESET
GNDD
71M6543
10 kΩ
R
2
V3P3SYS
R
LED
Phototransistor
1
V3P3SYS
R
R
100Ω
100Ω
1
1
RESET
RESET
DGND
DGND
71M6543
71M6533
71M6533
Figure
36, is
v1.0