MAX11040_10 Datasheet, PDF (27/32 Pages) Maxim Integrated Products – 24-Bit, 4-Channel, Simultaneous-Sampling,Cascadable,Sigma-Delta ADC

24-Bit, 4-Channel, Simultaneous-Sampling,
Cascadable, Sigma-Delta ADC
Applications Information
Multiple Device Synchronization
Synchronizing Multiple Devices
Using a Shared XIN Clock Source
To synchronize multiple devices sharing a single XIN
clock source, transition the SYNC input that is shared
by all devices high to low. When an external sync
source is not available, connect DRDYOUT of one
MAX11040 to the SYNC input of all devices in the
chain. The MAX11040 ignores any SYNC transitions
applied during the power-on reset.
Synchronizing Multiple Devices
Using Independent XIN Clock Sources
If it is undesirable to connect the XIN clock sources
together, due to EMI or other reasons, use DRDYIN,
DRDYOUT, and SYNC to align the conversion timing as
shown in Figure 17. This minimizes the effects of drift
between the clock sources by resynchronizing after
each conversion when DRDYOUT transitions low. In
this configuration, the maximum correction caused by a
SYNC edge is one XIN clock cycle.
The resulting sampling rate is determined by the sampling
frequency of the device with the slowest clock source,
plus the delay through the DRDYIN to DRDYOUT chain
between this slowest device and the end of the chain.
Synchronizing Multiple Devices
to an Independent Clock Source
To periodically synchronize multiple devices to an inde-
pendent timing source, connect the timing source to
the SYNC inputs of the devices. If minimal jitter is
important in the application, program the MAX11040’s
to a frequency slightly slower than the external frequen-
cy, such that SYNC falling edges only occur a short
time after the DRDYOUT signals.
DSP OR
MICROCONTROLLER
SYNC
CS
SCLK
DIN
MAX11040
CASCIN
CASCOUT
DRDYIN
DRDYOUT
DEVICE 0
FAULT
OVRFLW
DOUT
XIN XOUT CLKOUT
SYNC
CS
SCLK
DIN
MAX11040
CASCIN
CASCOUT
DRDYIN
DRDYOUT
DEVICE n
FAULT
OVRFLW
DOUT
XIN XOUT
SYNC
CS
SCLK
DIN
MAX11040
CASCIN
DRDYOUT
DRDYIN
DEVICE n+1
FAULT
OVRFLW
DOUT
XIN XOUT
CASCADE UP TO 8 DEVICES
Figure 17. One Crystal per MAX11040 and All SYNC Inputs Driven by DRDYOUT of the Last Device in the Chain
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