71M6541D Datasheet, PDF (102/166 Pages) Maxim Integrated Products – 0.1% Accuracy Over 2000:1 Current Range Energy Meter ICs

71M6541D/F/G and 71M6542F/G Data Sheet
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.
V3P3SYS
71M654x
OPT_RX
100 pF 10 kΩ
R₁
Phototransistor
V3P3SYS
OPT_TX
R₂
LED
Figure 41: Connection for Optical Components
4.12 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 Figure 42, left side. The RESET signal may be sourced from
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.
For a production meter, the RESET pin should be protected by the external components shown in
Figure 42, right side. R1 should be in the range of 100Ω and mounted as closely as possible to the IC.
Since the 71M6541D/F/G and 71M6542F/G generate their own power-on reset, a reset button or circuitry, as
shown in Figure 42, is only required for test units and prototypes.
VBAT/
V3P3D
R₂
1k Ω
Reset
Switch
0.1µF
V3P3D
71M654x
10kΩ
R₁
RESET
GNDD
71M654x
GNDD
Figure 42: External Components for the RESET Pin: Push-Button (Left), Production Circuit (Right)
4.13 Connecting the Emulator Port Pins
Even when the emulator is not used, small shunt capacitors to ground (22 pF) should be used for
protection from EMI as illustrated in Figure 43. Production boards should have the ICE_E pin connected
to ground.