Rainbow-electronics MAX1109 Manual de usuario descargar pdf (Pagina 15)

MAX1108/MAX1109

Single-Supply, Low-Power,

2-Channel, Serial 8-Bit ADCs

______________________________________________________________________________________ 15

CS does not need to be held low once a conversion is

started. Pulling CS high prevents data from being

clocked into the MAX1108/MAX1109 and three-states

DOUT, but it does not adversely affect an internal

clock-mode conversion already in progress. In this

mode, data can be shifted in and out of the

MAX1108/MAX1109 at clock rates up to 2MHz, provid-

ed that the minimum acquisition time (t

ACQ

) is kept

above 1µs.

Quick Look

To quickly evaluate the MAX1108/MAX1109’s analog

performance, use the circuit of Figure 9. The device

requires a control byte to be written to DIN before each

conversion. Tying CS to GND and DIN to V

feeds in

control bytes of FFH. In turn, this triggers single-ended,

unipolar conversions on CH0 in relation to COM in

external clock mode without powering down between

conversions. Apply an external 50kHz to 500kHz clock

SCLK

DIN

DOUT

1 4 8

START

SEL2 SEL1SEL0

I/EREF I/ECLK

REF

SHDN

D7 D6 D5

D3 D2 D1 D0

ACQ

IDLE

A/D STATE

10 14 18

CONV

35µs MAX

Figure 8. Single Conversion Timing, Internal Clock Mode

1µF

0.1µF

GND

SCLK

DIN

DOUT

0.01µF

CH0

COM

REF

1µF

ANALOG

INPUT

OSCILLOSCOPE

CH1

CH2

5µs/div

*CONVERSION RESULT = 10101010

MAX1108

MAX1109

SUPPLY

500kHz

OSCILLATOR

DOUT*

SCLK

MSB

LSB

Figure 9. Quick-Look Schematic

1 2 ... 10 11 12 13 14 15 16 17 18 19 20

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