71m6521fe Maxim Integrated Products, Inc., 71m6521fe Datasheet - Page 68

• Manufacturer Part Number: 71m6521fe
• Description: Energy Meter Ic
• Manufacturer: Maxim Integrated Products, Inc.

Even though a functional meter will not necessarily need a reset switch, it is useful to have a reset pushbutton for prototyping,
as shown in Figure 38, left side. The RESET signal may be sourced from V3P3SYS (functional in MISSION mode only),
V3P3D (MISSION and BROWNOUT modes), VBAT (all modes, if 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 38, right side. R
Capacitors to ground must be used for protection from EMI. Production boards should have the ICE_E pin connected to
ground.
If the ICE pins are used to drive LCD segments, the pull-up resistors should be omitted, as shown in Figure 39, and 22pF
capacitors to GNDD should be used for protection from EMI.
It is important to bring out the ICE_E pin to the programming interface in order to create a way for reprogramming
parts that have the flash SECURE bit (SFR 0xB2[6]) set. Providing access to ICE_E ensures that the part can be reset
between erase and program cycles, which will enable programming devices to reprogram the part. The reset required is im-
plemented with a watchdog timer reset (i.e. the hardware WDT must be enabled).
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V3P3D
V3P3D
VBAT/
VBAT/
Since the 71M6521DE/FE generates its own power-on reset, a reset button or circuitry, as shown in Figure 38, left
side, is only required for test units and prototypes.
Figure 38: External Components for RESET: Development Circuit (Left), Production Circuit (Right)
1kΩ
1kΩ
R
R
2
2
0.1nF
0.1nF
1
Switch
Switch
Reset
Reset
should be in the range of 100Ω and mounted as closely as possible to the IC.
GND
GND
V3P3
V3P3
Connecting the Emulator Port Pins
© 2005-2008 TERIDIAN Semiconductor Corporation
R
R
V3P3D
V3P3D
10kΩ
10kΩ
1
1
Figure 37: Voltage Divider for V1
R
R
1
1
R
R
RESET
RESET
DGND
DGND
2
2
71M6521
71M6521
71M6521DE/71M6521FE
5kΩ
5kΩ
R
R
3
3
100pF
100pF
C
C
1
1
R
R
100Ω
100Ω
1
1
Energy Meter IC
V1
V1
RESET
RESET
DGND
DGND
71M6521
71M6521
DATASHEET
JANUARY 2008
v1.0