Rainbow-electronics MAX1204 Manual de usuario descargar pdf (Pagina 17)

MAX1204

5V, 8-Channel, Serial, 10-Bit ADC

with 3V Digital Interface

______________________________________________________________________________________ 17

Hardware Power-Down

The SHDN pin places the converter into full

power-down mode. Unlike the software power-down

modes, conversion is not completed; it stops coinci-

dentally with SHDN being brought low. There is no

power-up delay if an external reference, which is not

shut down, is used. SHDN also selects internal or

external reference compensation (Table 7).

Power-Down Sequencing

The MAX1204’s automatic power-down modes can

save considerable power when operating at less than

maximum sample rates. The following sections discuss

the various power-down sequences.

Lowest Power at up to

500 Conversions per Channel per Second

Figure 14a depicts MAX1204’s power consumption for one

or eight channel conversions using full power-down mode

and internal reference compensation. A 0.01µF bypass

capacitor at REFADJ forms an RC filter with the internal

20kΩ reference resistor, with a 0.2ms time constant. To

achieve full 10-bit accuracy, 10 time constants (or 2ms in

this example) are required for the reference buffer to settle.

When exiting FULLPD, waiting this 2ms in FASTPD mode

(instead of just exiting FULLPD mode and returning to nor-

mal operating mode) reduces power consumption by a

factor of 10 or more (Figure 13).

Figure 12b. Timing Diagram for Power-Down Modes (Internal Clock)

FULL

POWER-DOWN

POWERED

POWERED UP

DATA VALID

INTERNAL CLOCK MODE

XXXX

10 S 00

XXXXX 

MODE

DOUT

DIN

CLOCK

MODE

SETS INTERNAL

CLOCK MODE

SETS FULL

POWER-DOWN

CONVERSION

SSTRB

Figure 12a. Timing Diagram for Power-Down Modes (External Clock)

POWERED UP

FULL

POWER-

DOWN

POWERED

POWERED UP

DATA VALID

(10 + 2 DATA BITS)

DATA VALID

(10 + 2 DATA BITS)

DATA 

INVALID



EXTERNAL

INTERNAL

XXXX

11 S 01

XXXXX XXXXX

S11

FAST

POWER-DOWN

MODE

DOUT

DIN

CLOCK

MODE

SHDN

SETS EXTERNAL

CLOCK MODE

SETS EXTERNAL

CLOCK MODE

SETS FAST

POWER-DOWN 

MODE

1 2 ... 12 13 14 15 16 17 18 19 20 21 22 23 24

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Rainbow-electronics MAX1204 Manual de usuario Pagina 17

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