MAX1304 Datasheet, PDF (20/36 Pages) Maxim Integrated Products – 8-/4-/2-Channel, 12-Bit, Simultaneous-Sampling ADCs with ±10V, ±5V, and 0 to +5V Analog Input Ranges

8-/4-/2-Channel, 12-Bit, Simultaneous-Sampling ADCs
with ±10V, ±5V, and 0 to +5V Analog Input Ranges
Data Throughput
The data throughput (f_TH) 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_TH as follows:
f_TH
=
t_ACQ
+
t_QUIET
+
1
12
+
3
x (N −1)
f_CLK
+1
where N is the number of active channels and t_QUIET is
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_DD
and connect CLK to DGND. Note that INTCLK/EXTCLK
is referenced to AV_DD, not DV_DD.
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_DD, not
DV_DD. 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.
Table 1. Throughput vs. Channels Sampled: f_CLK = 15MHz, t_ACQ = 100ns, t_QUIET = 50ns
CHANNELS
SAMPLED
(N)
1
2
3
4
5
6
7
8
CLOCK CYCLES
UNTIL
LAST RESULT
12
15
18
21
24
27
30
33
CLOCK CYCLE
FOR READING
LAST CONVERSION
1
1
1
1
1
1
1
1
TOTAL
CONVERSION
TIME (ns)
800
1000
1200
1400
1600
1800
2000
2200
TOTAL
THROUGHPUT
(ksps)
983
1643
2117
2474
2752
2975
3157
3310
THROUGHPUT
PER CHANNEL
(f_TH)
983
821
705
618
550
495
451
413
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