MAX108 Datasheet, PDF (21/32 Pages) Maxim Integrated Products – ±5V, 1.5Gsps, 8-Bit ADC with On-Chip 2.2GHz Track/Hold Amplifier

±5V, 1.5Gsps, 8-Bit ADC with
On-Chip 2.2GHz Track/Hold Amplifier
Table 6. Demux Operating and Reset Control Signals
SIGNAL NAME
CLK+, CLK-
DREADY+, DREADY-
RSTIN+, RSTIN-
RSTOUT+, RSTOUT-
TYPE
Sampling clock inputs
Differential PECL outputs
Differential PECL inputs
Differential PECL outputs
FUNCTION
Master ADC timing signal. The ADC samples on the rising edge of CLK+.
Data-Ready PECL Output. Output data changes on the rising edge of
DREADY+.
Demux reset input signals. Resets the internal demux when asserted.
Reset outputs for resetting additional external demux devices.
Reset Pipeline
The next section in the reset signal path is the reset
pipeline. This block adds clock cycles of latency to the
reset signal to match the latency of the converted ana-
log data through the ADC. In this way, when reset data
arrives at the RSTOUT+/RSTOUT- PECL output it will be
time-aligned with the analog data present in the prima-
ry and auxiliary ports at the time the reset input was
deasserted at RSTIN+/RSTIN-.
Demux Clock Generator
The demux clock generator creates the DIV1, DIV2, or
DIV4 clocks required for the different modes of demux
and non-demultiplexed operation. The TTL/CMOS con-
trol inputs DEMUXEN and DIVSELECT control the
demuxed mode selection, as described in Table 2. The
timing diagrams in Figures 16 and 17 show the output
timing and data alignment in DIV1, DIV2, and DIV4
modes, respectively.
The phase relationship between the sampling clock at
the CLK+/CLK- inputs and the data-ready clock at the
Dready+/Dready- outputs will be random at device
power-up. As with all divide-by-two circuits, two possi-
ble phase relationships exist between these clocks.
The difference between the phases is simply the inver-
sion of the DIV2-Dready clock. The timing diagram in
Figure 16 shows this relationship.
Reset all MAX108 devices to a known DREADY phase
after initial power-up for applications such as interleav-
ing, where two or more MAX108 devices are used to
achieve higher effective sampling rates. This synchro-
nization is necessary to set the order of output samples
between the devices. Resetting the converters accom-
plishes this synchronization. The reset signal is used to
force the internal counter in the demux clock-generator
block to a known phase state.
CLK+
50%
CLK-
t_PD1
DREADY-
"PHASE 1"
50%
DREADY+
t_FDREADY
DREADY +
80%
"PHASE 2"
20%
DREADY -
t_RDREADY
80%
20%
t_PWH
CLK+
CLK-
AUXILIARY PORT DATA
t_PWL
t_PD1
t_PD2
DREADY +
DREADY -
PRIMARY PORT DATA
Figure 16. CLK and DREADY Timing in Demuxed DIV2 Mode
Showing Two Possible DREADY Phases
Figure 17. Output Timing for All Modes (DIV1, DIV2, DIV4)
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