MAX1304_11 Datasheet, PDF (22/37 Pages) Maxim Integrated Products – 8-/4-/2-Channel, 12-Bit, Simultaneous-Sampling ADCs with ±10V, ±5V

8-/4-/2-Channel, 12-Bit, Simultaneous-Sampling ADCs
with ±10V, ±5V, and 0 to +5V Analog Input Ranges
CONVST
SAMPLE
INSTANT
t_ACQ
TRACK
EOC
EOLC
t_CONV
HOLD
t_NEXT
t_EOC
CS*
RD
D0–D11
t_CTR
t_ACC
CH0
t_REQ
*CS CAN BE LOW AT ALL TIMES, LOW DURING THE RD CYCLES, OR THE SAME AS RD.
t_RDH
t_RDL
TRACK
t_CVEOLCD
t_QUIET ≥ 50ns
t_RTC
CH1
Figure 7. Read During Conversion—Channel 0 and Channel 1 Selected, Internal Clock
Starting a Conversion
To start a conversion using internal clock mode, pull
CONVST low for the acquisition time (t_ACQ). The T/H
acquires the signal while CONVST is low, and conver-
sion begins on the rising edge of CONVST. The end-of-
conversion signal (EOC) pulses low whenever a
conversion result becomes available for read. The end-
of-last-conversion signal (EOLC) goes low when the last
conversion result is available (Figure 7).
To start a conversion using external clock mode, pull
CONVST low for the acquisition time (t_ACQ). The T/H
acquires the signal while CONVST is low. The rising
edge of CONVST is the sampling instant. Apply an
external clock to CLK to start the conversion. To avoid
T/H droop degrading the sampled analog input signals,
the first CLK pulse must occur within 10µs from the
rising edge of CONVST. Additionally, the external clock
frequency must be greater than 100kHz to avoid T/H
droop-degrading accuracy. The first conversion result
is available for read when EOC goes low on the rising
edge of the 13th clock cycle. Subsequent conversion
results are available after every third clock cycle there-
after (Figures 8 and 9).
In both internal and external clock modes, hold
CONVST high until the last conversion result is read. If
CONVST goes low in the middle of a conversion, the
current conversion is aborted and a new conversion is
initiated. Furthermore, there must be a period of bus
inactivity (t_QUIET) for 50ns or longer before the falling
edge of CONVST for the specified ADC performance.
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