Rainbow-electronics MAX1314 Manual do Utilizador descarregar pdf (Página 20)

MAX1304–MAX1306/MAX1308–MAX1310/MAX1312–MAX1314

8-/4-/2-Channel, 12-Bit, Simultaneous-Sampling ADCs

with ±10V, ±5V, and 0 to +5V Analog Input Ranges

20 ______________________________________________________________________________________

Data Throughput

The data throughput (f

) of the MAX1304–MAX1306/

MAX1308–MAX1310/MAX1312–MAX1314 is a function

of the clock speed (f

CLK

). In internal clock mode, f

CLK

15MHz (typ). In external clock mode, 100kHz ≤ f

CLK

≤

20MHz. When reading during conversion (Figures 7 and

8), calculate f

as follows:

where N is the number of active channels and t

QUIET

the period of bus inactivity before the rising edge of

CONVST. See the Starting a Conversion section for

more information.

Table 1 uses the above equation and shows the total

throughput as a function of the number of channels

selected for conversion.

Clock Modes

The MAX1304–MAX1306/MAX1308–MAX1310/MAX1312–

MAX1314 provide a 15MHz internal conversion clock.

Alternatively, an external clock can be used.

Internal Clock

Internal clock mode frees the microprocessor from the

burden of running the ADC conversion clock. For inter-

nal clock operation, connect INTCLK/EXTCLK to AV

and connect CLK to DGND. Note that INTCLK/EXTCLK

is referenced to AV

, not DV

External Clock

For external clock operation, connect INTCLK/EXTCLK

to AGND and connect an external clock source to CLK.

Note that INTCLK/EXTCLK is referenced to AV

, not

. The external clock frequency can be up to

20MHz. Linearity is not guaranteed with clock frequen-

cies below 100kHz due to droop in the T/H circuits.

ACQ QUIET

CLK

+ − +

12 3 1 1()

Table 1. Throughput vs. Channels Sampled: f

CLK

= 15MHz, t

ACQ

= 100ns, t

QUIET

= 50ns

CHANNELS

SAMPLED

(N)

CLOCK CYCLES

UNTIL

LAST RESULT

CLOCK CYCLE

FOR READING

LAST CONVERSION

TOTAL

CONVERSION

TIME (ns)

TOTAL

THROUGHPUT

(ksps)

THROUGHPUT

PER CHANNEL

)

112 1800 983 983

21511000 1643 821

31811200 2117 705

42111400 2474 618

52411600 2752 550

62711800 2975 495

73012000 3157 451

83312200 3310 413

1 2 ... 15 16 17 18 19 20 21 22 23 24 25 ... 35 36

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