71M6534H Demo Board User’s Manual
Page: 54 of 86
© 2005-2007 TERIDIAN Semiconductor Corporation
V2-0
2.4 SCHEMATIC INFORMATION
In this section, hints on proper schematic design are provided that will help designing circuits that are functional
and sufficiently immune to EMI (electromagnetic interference).
2.4.1 COMPONENTS FOR THE V1 PIN
The V1 pin of the 71M6534/6534H can never be left unconnected.
A voltage divider should be used to establish that V1 is in a safe range when the meter is in mission mode (V1
must be lower than 2.9V in all cases in order to keep the hardware watchdog timer enabled). Pulling ICE_E up
to V3P3 automatically disables the hardware watchdog timer.
V3P3
R
2
R
1
Figure 2-7: Voltage Divider for V1
On the 6534 Demo Boards this feature is implemented with resistors R83/R86/R105 and capacitor C21. See
the board schematics in the Appendix for details.
2.4.2 RESET CIRCUIT
Even though a functional meter will not necessarily need a reset switch, the 71M6534 Demo Boards provide a
reset pushbutton that can be used when prototyping and debugging software (see Figure 2-8). R1 and C1 are
mounted very close to the 71M6534. In severe EMI environments R
2
can be removed, if the trace from the
pushbutton switch to the RESETZ pin poses a problem,
For production meters, the RESET pin should be directly connected to GND.
Figure 2-8: External Components for RESET
R
3
5k
Ω
C
1
100pF
GND
V3P3
R
2
R
1
R
3
5k
Ω
C
1
100pF
GND
71M6534
R
1
71M6534
R
2
Reset
Switch
10
Ω
1nF
100
Ω
C
1
R
1
R
2
Reset
Switch
10
Ω
1nF
100
Ω
C
1
