CS5012A, CS5014, CS5016
Also, the CS5012A/14/16’s internal RC oscillator
±
exhibits jitter (typically 0.05% of its period),
+5V
which is high compared to crystal oscillators. If
the CS5012A/14/16 is configured for synchro-
nous sampling while operating from its internal
oscillator, this jitter will directly affect sampling
purity. The user can obtain best sampling purity
while synchronously sampling by using an exter-
nal crystal-based clock.
R
C
RST
CS5012A/14/16
Figure 6. Power-on Reset Circuit
Reset
Upon power up, the CS5012A/14/16 must be re-
set to guarantee a consistent starting condition
and initially calibrate the devices. Due to the
CS5012A/14/16’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 5%, 1% or
0.25% of its final value, for the CS5012A/14/16
respectively, before RST falls to guarantee an ac-
curate calibration. Later, the CS5012A/14/16 may
be reset at any time to initiate a single full cali-
bration. Reset overrides all other functions. If
reset, the CS5012A/14/16 will clear and initiate a
new calibration cycle mid-conversion or mid-cali-
bration.
eliminate the possibility of inadvertent software
reset. The EOC output remains high throughout
the calibration operation and will fall upon its
completion. It can thus be used to generate an
interrupt indicating the CS5012A/14/16 is ready
for operation. While calibrating, the HOLD input
is ignored until EOC falls. After EOC falls, six
CLKIN cycles plus 2.25 µs (1.32 µs for the
CS5012A -7 version only) must be allowed for
signal acquisition before HOLD is activated. Un-
der microprocessor-independent operation (CS,
RD low; A0 high) the CS5014’s and CS5016’s
EOC output will not fall at the completion of the
calibration cycle, but EOT will fall 15 CLKIN
cycles later.
Initiating Calibration
Resets can be initiated in hardware or software.
The simplest method of resetting the
CS5012A/14/16 involves strobing the RST pin
high for at least 100 ns. When RST is brought
high all internal logic clears. When it returns low,
a full calibration begins which takes 58,280
CLKIN cycles for the CS5012A (approximately
9.1 ms with a 6.4 MHz clock) and 1,441,020
CLKIN cycles for the CS5016, CS5014 and
CS5012 (approximately 360 ms with a 4 MHz
CLKIN). A simple power-on reset circuit can be
built using a resistor and capacitor, and a
Schmitt-trigger inverter to prevent oscillation (see
Figure 6). The CS5012A/14/16 can also be reset
in software when under microprocessor control.
The CS5012A/14/16 will reset whenever CS, A0,
and HOLD are taken low simultaneously. See the
Microprocessor Interface section (below) to
All modes of calibration can be controlled in
hardware or software. Accuracy can thereby be
insured at any time or temperature throughout op-
erating life. After initial calibration at power-up,
the CS5012A/14/16’s charge-redistribution design
yields better temperature drift and more graceful
aging than resistor-based technologies, so calibra-
tion is normally only required once, after
power-up.
The first mode of calibration, reset, results in a
single full calibration cycle. The second type of
calibration, "burst" cal, allows control of partial
calibration cycles. Due to an unforeseen con-
didtion inside the part, asynchronous termination
of calibration may result in a sub-optimal result.
Burst cal should not be used.
DS14F6
2-21
CIRRUS [ CIRRUS LOGIC ]
