MAX11044_11 Datasheet, PDF (18/27 Pages) Maxim Integrated Products – 4-/6-/8-Channel, 16-/14-Bit, Simultaneous-Sampling ADCs

4-/6-/8-Channel, 16-/14-Bit,
Simultaneous-Sampling ADCs
Starting a Conversion
CONVST initiates conversions. The MAX11044/
MAX11045/MAX11046 and MAX11054/MAX11055/
MAX11056 provide two acquisition modes set through
the configuration register. Allow a quiet time (t_Q) of
500ns prior to the start of conversion to avoid any noise
interference during readout or write operations from
corrupting a sample.
In default mode (CR0 = 0), drive CONVST low to place
the MAX11044/MAX11045/MAX11046 and MAX11054/
MAX11055/MAX11056 into acquisition mode. All the
input switches are closed and the internal T/H circuits
track the respective input voltage. Keep the CONVST
signal low for at least 1µs (t_ACQ) to enable proper set-
tling of the sampled voltages. On the rising edge of
CONVST, the switches are opened and the
MAX11044/MAX11045/MAX11046 and MAX11054/
MAX11055/MAX11056 begin the conversion on all the
samples in parallel. EOC remains high until the conver-
sion is completed.
In the second mode (CR0 = 1), the MAX11044/
MAX11045/MAX11046 and MAX11054/MAX11055/
MAX11056 enter acquisition mode as soon as the previ-
ous conversion is completed. CONVST rising edge initi-
ates the next sample and conversion sequence.
CONVST needs to be low for at least 20ns to be valid.
Provide adequate time for acquisition and the requisite
quiet time in both modes to achieve accurate sampling
and maximum performance of the MAX11044/
MAX11045/MAX11046 and MAX11054/MAX11055/
MAX11056.
Reading Conversion Results
The CS and RD are active-low, digital inputs that con-
trol the readout through the 16-/14-bit, parallel, 20MHz
data bus (D0–D15/D13). After EOC transitions low, read
the conversion data by driving CS and RD low. Each
low period of RD presents the next channel’s result.
When CS or RD are high, the data bus is high imped-
ance. CS may be driven high between individual chan-
nel readouts or left low during the entire 8-channel
readout.
Reference
Internal Reference
The MAX11044/MAX11045/MAX11046 and MAX11054/
MAX11055/MAX11056 feature a precision, low-drift,
internal bandgap reference. Bypass REFIO with a 0.1µF
capacitor to AGND to reduce noise. The REFIO output
voltage may be used as a reference for other circuits. The
output impedance of REFIO is 10kΩ. Drive only high
impedance circuits or buffer externally when using REFIO
to drive external circuitry.
External Reference
Set the configuration register to disable the internal ref-
erence and drive REFIO with a high-quality external ref-
erence. To avoid signal degradation, ensure that the
integrated reference noise applied to REFIO is less
than 10µV in the bandwidth of up to 50kHz.
CS
(USER SUPPLIED)
t₅
t₃
t₄
WR
(USER SUPPLIED)
t₇
t₆
CR0–CR3
(USER SUPPLIED)
CONFIGURATION
REGISTER
Figure 4. Programming Configuration-Register Timing
Requirements
CS
(USER SUPPLIED)
RD
(USER SUPPLIED)
DB0–DB15
t₈
t₉
t₁₀
t₁₁
t₁₂
t₁₃
S_n
S_{n + 1}
Figure 5. Readout Timing Requirements
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