71M6531D Datasheet, PDF (68/115 Pages) Teridian Semiconductor Corporation – Energy Meter IC

Data Sheet 71M6531D/F-71M6532D/F
V3P3D
LCD Segments
(optional)
62 Ω
62 Ω
62 Ω
22 pF 22 pF 22 pF
FDS 6531/6532 005
ICE_E
E_RST
E_RXT
E_TCLK
71M6531D/F
71M6532D/F
Figure 38: External Components for the Emulator Interface
3.13 Connecting a Battery
It is important that a valid voltage is connected to the VBAT pin at all times. For meters without a battery,
VBAT should be connected directly to V3P3SYS. Designs for meters with batteries need to ensure that
the meter functions even when the battery voltage decreases below the specified voltage for VBAT. This
can be achieved by connecting a diode from V3P3SYS to VBAT. However, the battery test will yield in-
accurate results if that technique is used, since the voltage at V3P3SYS will feed current to the VBAT pin.
A better solution is shown in Figure 39: During the battery test, a DIO pin is activated as an output and
applies a low voltage to the anode of the diode. This prevents the voltage at the power supply to influence
the voltage at the VBAT pin.
Power
Supply
V3P3SYS
V3P3A
DIO
Battery or ⁺
Super-Cap
-
VBAT
71M6531/71M6532
Figure 39: Connecting a Battery
As mentioned in section 2.3, meters equipped with batteries need to contain code that transitions
the chip to SLEEP mode as soon as the battery is attached in production. Otherwise, remaining in
BROWNOUT mode would add unnecessary drain to the battery.
3.14 Flash Programming
Operational or test code can be programmed into the flash memory using either an in-circuit emulator or
the Flash Programmer Module (TFP2) available from Teridian. The flash programming procedure uses
the E_RST, E_RXTX and E_TCLK pins. The FL_BANK[2:0] register must be set to the value correspond-
ing to the bank that is being programmed.
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