71M6521BE
Energy Meter IC
DATA SHEET
JANUARY 2008
Crystal Oscillator
The oscillator of the 71M6521BE 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.
Since the oscillator is self-biasing, an external resistor must not be connected across the crystal.
With a typical 32kHz crystal, the 71M6521BE needs 600 to 650 milliseconds to stabilize the oscillator clock after power-up.
This time is added to the 125ms (4096 CK32 cycles) for the PLL_OK signal to become true which is required for the part to
enter MISSION mode.
Flash Programming
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.
MPU Firmware Library
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
71M6521BE IC. The Demonstration Kits come with the 71M6521BE 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).
Meter Calibration
Once the TERIDIAN 71M6521BE 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 71M6521BE supports common industry standard calibration techniques, such as single-point (energy-only), multi-point
(energy, Vrms, Irms), and auto-calibration.
V1.0
© 2005-2008 TERIDIAN Semiconductor Corporation
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