71M6533 Datasheet, PDF (76/132 Pages) Teridian Semiconductor Corporation – Energy Meter IC

71M6533/G/H and 71M6534/H Data Sheet
FDS_6533_6534_004
VBAT/
V3P3D
R₂
1k ?
Reset
Switch
0.1µF
V3P3D
71M6533/
71M6534
10k ?
R₁
RESET
GNDD
71M6533/
71M6534
Figure 42: External Components for the RESET Pin: Push-Button (Left), Production Circuit (Right)
4.9 Connecting the Emulator Port Pins
Even when the emulator is not used, small shunt capacitors to ground (22 pF) should be used for protection
from EMI as illustrated in Figure 43. Production boards should have the ICE_E pin connected to ground
via a resistor of around 200 Ω.
The 71M6534 is capable of supporting a trace emulator. To connect this non-standard emulator, the pins
E_TBUS0 (SEG51) – E_TBUS3 (SEG54) and E_ISYNC (SEG55) have to be brought out to the emulator
interface.
V3P3D
LCD Segments
(optional)
62 Ω
62 Ω
71M6533/71M6534
ICE_E
E_RST
E_RXT
62 Ω
22 pF 22 pF 22 pF
E_TCLK
Figure 43: External Components for the Emulator Interface
4.10 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
inaccurate 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 44. 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.
76
Rev 2