71M6521FE-IM/F Maxim Integrated Products, 71M6521FE-IM/F Datasheet - Page 71

• Manufacturer Part Number: 71M6521FE-IM/F
• Description: IC ENERGY METER 32K FLASH 68-QFN
• Manufacturer: Maxim Integrated Products

Specifications of 71M6521FE-IM/F

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

71M6521DE/DH/FE Data Sheet
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 40, 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 40, right side. R
as closely as possible to the IC.
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 41, 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 implemented with a watchdog timer reset (i.e. the hardware WDT must be enabled).
The oscillator of the 71M6521DE/DH/FE drives a standard 32.768kHz watch crystal. The oscillator has been
designed specifically to handle these crystals and is compatible with their high impedance and limited power handling
capability. The oscillator power dissipation is very low to maximize the lifetime of any battery backup device attached
to VBAT.
Rev 2
V3P3D
V3P3D
VBAT/
VBAT/
Figure 40: External Components for RESET: Development Circuit (Left), Production Circuit (Right)
Since the 71M6521DE/DH/FE generates its own power-on reset, a reset button or circuitry, as shown in
Figure 40, left side, is only required for test units and prototypes.
1kΩ
1kΩ
R
R
2
2
1nF
1nF
Switch
Switch
Reset
Reset
Figure 41: External Components for the Emulator Interface
62Ω
62Ω
62Ω
62Ω
V3P3D
V3P3D
Connecting the Emulator Port Pins
62Ω
62Ω
22pF
22pF
R
R
V3P3D
V3P3D
10kΩ
10kΩ
1
1
LCD Segments
LCD Segments
Crystal Oscillator
22pF
22pF
(optional)
(optional)
22pF
22pF
RESET
RESET
DGND
DGND
71M6521
71M6521
1
should be in the range of 100Ω and mounted
ICE_E
ICE_E
E_RST
E_RST
E_RXTX
E_RXTX
E_TCLK
E_TCLK
71M6521
71M6521
R
R
100Ω
100Ω
1
1
RESET
RESET
DGND
DGND
71M6521
71M6521
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