Maxim-integrated 71M6533-DB Instrukcja Użytkownika Pobierz pdf (Strona 46)

71M6533-DB Demo Board User’s Manual

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2.3 POWER SAVING MEASURES

In many cases, especially when operating the 71M6533 from a battery, it is desirable to reduce the power

consumed by the chip to a minimum. This can be achieved with the measures listed in Table 2-1.

Power Saving Measure

Software Control

Typical

Savings

Disable the CE

CE_EN = 0

0.16mA

Disable the ADC

ADC_DIS = 1

1.8mA

Disable clock test output CKTEST

CKOUTDIS = 1

0.6mA

Disable emulator clock

ECK_DIS = 1

0.1mA

Disable RTM outputs

RTM_EN = 0

0.01mA

Disable SSI output

SSI_EN = 0

Select DGND for the multiplexer input

TMUX[3:0] = 0

Disable reference voltage output

VREF_DIS = 1

Reduce the clock for the MPU

MPU_DIV = 5

0.4mA

Table 2-1: Power Saving Measures

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 71M6533 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 71M6533 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.

Figure 2-7: Voltage Divider for V1

On the 71M6533-DB Demo Board this feature is implemented with resistors R83/R86, capacitor C31 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 71M6533-DB Demo Boards provide

a reset pushbutton that can be used when prototyping and debugging software (see Figure 2-8).. For a

production meter, the RESET pin should be pulled down hard to GNDD.

V3P3

5kΩ

100pF

GND

V3P3

5kΩ

100pF

GND

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