Rainbow Electronics MAX1326 - Manual (Page 17)

MAX1316–MAX1318/MAX1320–MAX1322/MAX1324–MAX1326
8-/4-/2-Channel, 14-Bit, Simultaneous-Sampling ADCs
with ±10V, ±5V, and 0 to +5V Analog Input Ranges
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Data Throughput
The data throughput (f TH ) of the MAX1316–MAX1318/
MAX1320–MAX1322/MAX1324–MAX1326 is a function
of the clock speed (f
CLK ). In internal-clock mode, f CLK =
10MHz. In external-clock mode, 100kHz ≤ f
CLK
≤
12.5MHz. When reading during conversion (Figures 5
and 6), calculate f
TH as follows:
where N is the number of active channels and t
QUIET
includes acquistion time t
ACQ
. t
QUIET
is the period of bus
inactivity before the rising edge of CONVST. Typically use
t
QUIET = t ACQ + 50ns, and prevent disturbance on the
output bus from corrupting signal acquistion. See the
Starting a Conversion section for more information.
Reading a Conversion Result
Reading During a Conversion
Figures 5 and 6 show the interface signals for initiating a
read operation during a conversion cycle. These figures
show two channels selected for conversion. If more chan-
nels are selected, the results are available successively
every third clock cycle. CS can be low at all times; it can
be low during the RD cycles, or it can be the same as RD.
After initiating a conversion by bringing CONVST high,
wait for EOC to go low (about 1.6µs in internal-clock
mode or 17 clock cycles in external-clock mode) before
reading the first conversion result. Read the conversion
result by bringing RD low, thus latching the data to the
parallel digital-output bus. Bring RD high to release the
digital bus. Wait for the next falling edge of EOC (about
300ns in internal-clock mode or three clock cycles in
external-clock mode) before reading the next result.
When the last result is available, EOLC goes low.
f
t
x N
f
TH
QUIET
CLK
=
+
+ − +
1
16 3 1 1 ( )
Table 3. Throughput vs. Channels Sampled (t QUIET = t ACQ = 200ns, f CLK = 10MHz)
CHANNELS
SAMPLED
(N)
CLOCK CYCLES
UNTIL LAST
RESULT
CLOCK CYCLE FOR
READING LAST
CONVERSION
TOTAL
CONVERSION
TIME (ns)
SAMPLES PER
SECOND
(ksps)
THROUGHPUT
PER CHANNEL
(ksps)
1 16 1 1900 526 526
2 19 1 2200 909 455
3 22 1 2500 1200 400
4 25 1 2800 1429 357
5 28 1 3100 1613 323
6 31 1 3400 1765 294
7 34 1 3700 1892 270
8 37 1 4000 2000 250
Figure 5. Read During Conversion—Two Channels Selected, Internal Clock
CONVST
CH0
TRACK
HOLD
D0–D13
SAMPLE
t 1
t 13
t 12
t 10 t 3
t 11
TRACK
CH1
t CONV t NEXT
EOC
RD
t
20