71m6521fe Maxim Integrated Products, Inc., 71m6521fe Datasheet - Page 69

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

The oscillator of the 71M6521DE/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.
Board layouts with minimum capacitance from XIN to XOUT will require less battery current. Good layouts will have XIN and
XOUT shielded from each other.
Operational or test code can be programmed into the flash memory using either an in-circuit emulator or the Flash
Programmer Module (TFP-1) available from TERIDIAN. The flash programming procedure uses the E_RST, E_RXTX, and
E_TCLK pins.
All application-specific MPU functions mentioned above under “Application Information” are available from TERIDIAN as a
standard ANSI C library and as ANSI “C” source code. The code is available as part of the Demonstration Kit for the
71M6521DE/FE IC. The Demonstration Kits come with the 71M6521DE/FE IC preprogrammed with demo firmware mounted
on a functional sample meter PCB (Demo Board). The Demo Boards allow for quick and efficient evaluation of the IC without
having to write firmware or having to supply an in-circuit emulator (ICE).
Once the TERIDIAN 71M6521DE/FE energy meter device has been installed in a meter system, it has to be calibrated for
tolerances of the current sensors, voltage dividers and signal conditioning components. The device can be calibrated using the
gain and phase adjustment factors accessible to the CE. The gain adjustment is used to compensate for tolerances of
components used for signal conditioning, especially the resistive components. Phase adjustment is provided to compensate for
phase shifts introduced by the current sensors.
Due to the flexibility of the MPU firmware, any calibration method, such as calibration based on energy, or current and voltage
can be implemented. It is also possible to implement segment-wise calibration (depending on current range).
The 71M6521DE/FE supports common industry standard calibration techniques, such as single-point (energy-only), multi-point
(energy, Vrms, Irms), and auto-calibration.
v1.0
Since the oscillator is self-biasing, an external resistor must not be connected across the crystal.
Figure 39: External Components for the Emulator Interface
62Ω
62Ω
62Ω
62Ω
V3P3D
V3P3D
© 2005-2008 TERIDIAN Semiconductor Corporation
62Ω
62Ω
22pF
22pF
MPU Firmware Library
LCD Segments
LCD Segments
Crystal Oscillator
Meter Calibration
22pF
22pF
(optional)
(optional)
Flash Programming
22pF
22pF
71M6521DE/71M6521FE
ICE_E
ICE_E
E_RST
E_RST
E_RXTX
E_RXTX
E_TCLK
E_TCLK
71M6521
71M6521
Energy Meter IC
DATASHEET
JANUARY 2008
Page: 69 of 101