CS5516 ETC, CS5516 Datasheet - Page 14

• Manufacturer Part Number: CS5516
• Description: 16BIT/20-BIT BRIDGE TRANSDUCER A/D CONVERTER
• Manufacturer: ETC

System Initialization
Whenever
CS5516/CS5520 A/D converters, the devices
must be reset to a known condition before
proper operation can occur. The internal reset is
applied after power is established and lasts for
approximately 100 ms. The RST pin can also be
used to establish a reset condition. The reset sig-
nal should remain low for at least one XIN clock
cycle to ensure adequate reset time. It is recom-
mended that the RST pin be used to reset the
converter if the power supplies rise very slowly
or with poor startup characteristics. The RST
signal can be generated by a microcontroller out-
put, or by use of an R-C circuit.
The reset function initializes the configuration
register and all five of the calibration registers;
and places the microcontroller in command
mode ready to accept a command from the serial
port. Whenever the device is reset the DRDY
pin will be set to a logic 1 and the on-chip regis-
ters are initialized to the following states:
14
Configuration
Calibration registers:
DAC
Gain
AIN Ratiometric Offset
AIN Non-ratiometric Offset
VREF Non-ratiometric Offset 000000(H)
power
is
applied
000000(H)
000000(H)
800000(H)
000000(H)
000000(H)
to
the
CALIBRATION
After the CS5516/20 is reset, the device is func-
tional and can perform measurements without
being calibrated. The converter will utilize the
initialized values of the calibration registers to
calculate output words.
The converter uses the two outputs (AIN &
VREF) of the dual channel converter along with
the contents of the calibration registers to com-
pute the conversion data word. The following
equation indicates the computation.
Where R0 is the output data, D
are the digital output words from the AIN and
VREF digital filter channels, and R1, R2, R3
and R4 are the contents of the following calibra-
tion registers:
R1 = AIN non-ratiometric offset
R2 = VREF non-ratiometric offset
R3 = AIN ratiometric offset
R4 = Gain
The computed output word, R0, is a two’s com-
plement number.
Calibration minimizes the errors in the converted
output data. If calibration has not been per-
formed, the measurements will include offset
and gain errors of the entire system.
The converter may be calibrated each time it is
powered up, or calibration words from a pre-
vious calibration may be uploaded into the
appropriate calibration registers from some type
of E
The converter uses five different registers to
store specific calibration information. Each of
the calibration registers stores information perti-
nent to correcting a specific source of error
associated with either the converter or with the
input transducer and its wiring. The method by
2
PROM by the system microcontroller.
R0
R4
[
[
D
D
VREF
AIN
CS5516, CS5520
R1
R2
]
AIN
R3
and D
]
DS74F1
VREF