CS5101A CS5102A
Registered Burst Transmission (RBT)
The SSH/SDL goes low coincident with the first
falling edge of SCLK, and returns high 2 CLKIN
cycles after the last rising edge of SCLK. This
signal frames the 16 data bits and is useful for
interfacing to shift registers (e.g. 74HC595) or to
DSP serial ports.
RBT mode is selected by tying SCKMOD high,
and OUTMOD low. As in PDT mode, SCLK is
an input, however data is available immediately
following conversion, and may be clocked out
the moment TRK1 or TRK2 falls. The falling
edge of HOLD clears the output buffer, so any
unread data will be lost. A new conversion may
be initiated before all the data has been clocked
out if the unread data bits are not important
(Figure 4).
SYSTEM DESIGN WITH THE CS5101A
AND CS5102A
Figure 7 shows a general system connection dia-
gram for the CS5101A and CS5102A.
Synchronous Self-Clocking (SSC)
Digital Circuit Connections
SSC mode is selected by tying SCKMOD low,
and OUTMOD high. In SSC mode, SCLK is an
output, and will clock out each bit of the data as
it’s being converted. SCLK will remain high be-
tween conversions, and run at a rate of 1/4 the
master clock speed for 16 low pulses during con-
version (Figure 5).
When TTL loads are utilized the potential for
crosstalk between digital and analog sections of
the system is increased. This crosstalk is due to
high digital supply and signal currents arising
from the TTL drive current required of each digi-
tal output. Connecting CMOS logic to the digital
outputs is recommended. Suitable logic families
include 4000B, 74HC, 74AC, 74ACT, and
74HCT.
The SSH/SDL goes low coincident with the first
falling edge of SCLK, and returns high 2 CLKIN
cycles after the last rising edge of SCLK. This
signal frames the 16 data bits and is useful for
interfacing to shift registers (e.g. 74HC595) or to
DSP serial ports.
System Initialization
Upon power up, the CS5101A and CS5102A
must be reset to guarantee a consistent starting
condition and initially calibrate the device. Due
to each device’s low power dissipation and low
temperature drift, no warm-up time is required
before reset to accommodate any self-heating ef-
fects. However, the voltage reference input
should have stabilized to within 0.25% of its final
value before RST rises to guarantee an accurate
calibration. Later, the CS5101A and CS5102A
may be reset at any time to initiate a single full
calibration.
Free Run (FRN)
Free Run is the internal, synchronous loopback
mode. FRN mode is selected by tying SCKMOD
and OUTMOD low. SCLK is an output, and op-
erates exactly the same as in the SSC mode. In
Free Run mode, the converter initiates a new
conversion every 80 master clock cycles, and al-
ternates between channel 1 and channel 2. HOLD
is disabled, and should be tied to either VD+ or
DGND. CH1/2 is an output, and will change at
the start of each new conversion cycle, indicating
which channel will be tracked after the current
conversion is finished (Figure 6).
When RST is brought low all internal logic
clears. When RST returns high on the CS5101A,
a calibration cycle begins which takes 11,528,160
master clock cycles to complete (approximately
1.4 seconds with an 8 MHz master clock). The
18
DS45F2
CIRRUS [ CIRRUS LOGIC ]
