Rainbow Electronics MAX1092 User Manual

Page 13

can be used. At power-up, the MAX1090/MAX1092
enter the default external clock mode.

Internal Clock Mode

Select internal clock mode to release the µP from the
burden of running the SAR conversion clock. To select
this mode, bit D7 of the control byte must be set to 1
and bit D6 must be set to 0; the internal clock frequen-
cy is then selected, resulting in a 3.6µs conversion
time. When using the internal clock mode, connect the

CLK pin either high or low to prevent the pin from float-
ing.

External Clock Mode

To select the external clock mode, bits D6 and D7 of
the control byte must be set to one. Figure 6 shows the
clock and WR timing relationship for internal (Figure 6a)
and external (Figure 6b) acquisition modes with an
external clock. Proper operation requires a 100kHz to
7.6MHz clock frequency with 30% to 70% duty cycle.
Operating the MAX1090/MAX1092 with clock frequen-

MAX1090/MAX1092

400ksps, +5V, 8-/4-Channel, 10-Bit ADCs

with +2.5V Reference and Parallel Interface

______________________________________________________________________________________

CLK

WR GOES HIGH WHEN CLK IS HIGH.

WR GOES HIGH WHEN CLK IS LOW.

CWS

CWH

ACQUISITION STARTS

CONVERSION STARTS

ACQUISITION ENDS

ACQMOD = "0"

Figure 6a. External Clock and

Timing (Internal Acquisition Mode)

CLK

WR GOES HIGH WHEN CLK IS HIGH.

WR GOES HIGH WHEN CLK IS LOW.

CWH

CWS

ACQUISITION STARTS

CONVERSION STARTS

ACQUISITION ENDS

ACQMOD = "1"

ACQMOD = "0"

Figure 6b. External Clock and

Timing (External Acquisition Mode)