71M6533 Datasheet, PDF (72/124 Pages) Teridian Semiconductor Corporation – Energy Meter IC

71M6533/71M6534 Data Sheet
V3P3D
LCD Segments
(optional)
62 Ω
62 Ω
62 Ω
22 pF 22 pF 22 pF
FDS_6533_6534_004
71M6533/71M6534
ICE_E
E_RST
E_RXT
E_TCLK
Figure 40: External Components for the Emulator Interface
3.14 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 41: 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
71M6533/6534
Figure 41: Connecting a Battery
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.
3.15 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-2) available from Teridian. The flash programming procedure uses
the E_RST, E_RXTX, and E_TCLK pins. The FL_BANK register has to be set to the value corresponding
to the bank that is being programmed.
72
© 2007-2009 TERIDIAN Semiconductor Corporation
v1.1