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71M6513/71M6513H Demo Board User’s Manual
Page: 55 of 112
©
2005-2006 TERIDIAN Semiconductor Corporation
Revision 5.6
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 71M6513/6513H 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). For proper
debugging or loading code into the 71M6513/6513H mounted on a PCB, it is necessary to have a provision like
the header JP1 shown above R1 in Figure 2-7. A shorting jumper on this header pulls V1 up to V3P3 disabling
the hardware watchdog timer.
L1
FERRITE
D10
UCLAMP3301D
V3P3
1
2
JP1
HDR 1x2
C2
1000pF
GND
V1
C1
10uF
R2
21.5K
R1
10K
Figure 2-7: Voltage Divider for V1
On the 6513 Demo Boards this feature is implemented with resistors R83/R86, capacitor C31 (D6513T3C1
Demo Board) and TP10. 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 71M6513 Demo Boards provide a
reset pushbutton that can be used when prototyping and debugging software. When a circuit is used in an EMI
environment, the RESETZ pin should be supported by the external components shown in Figure 2-8. R
1
should
be in the range of 200
Ω
, R
2
should be around 10
Ω
. The capacitor C
1
should be 1nF. R1 and C1 should be
mounted as close as possible to the IC. In cases where the trace from the pushbutton switch to the RESETZ pin
poses a problem, R
2
can be removed.
C1
1000pF
GND
RESETZ
R2
0
R1
200
V3P3
SW1
PB-SW
R3
10
C2
0.1uF
Figure 2-8: External Components for RESETZ
http://www.datasheetcatalog.com/