ES51999
4 3/4 and 5 3/4 A/D AUTO
X10 function is OFF
X10 function is ON
switch INT phase DINT phase AZ phase INT phase DINT phase AZ phase
A
B
C
ON
OFF
OFF
ON
OFF
OFF
ON
ON
ON
OFF
ON
ON
OFF
OFF
ON
ON
ON
OFF
In AZ phase, all the switches is ON, the effective resistor is all the resistors in parallel.
The effective resistor is therefore less than 10 kΩ. If X10 function is never used, the
matching between 200 kΩ and (Rx + 20 kΩ) is not necessary. In this situration, (Rx + 20
kΩ) can be replaced by a resistor about 20 kΩ, or simply omitted.
(8) ZERO Calibration
In ES51999, the inherent delay of the OPAMP will introduce a few counts to the output.
The method to prevent this problem is zero calibration. When zero calibration is ON,
ES51999 shorts the input to SGND internally. uP needs to save the results of zero input.
After zero calibration is OFF, the result of zero input is then deducte from the counts of
the following measurements.
Zero calibration can be enabled on any measurement. When the ZERO bit is set by
uP, ES51999 begins to execute zero calibration. ES51999 stops executing zero
calibration until the ZERO bit is reset by uP.
In voltage/current/diode/capacitance measurement, the de-integration voltage is fixed,
therefore zero calibration needs only be enabled once. The results could be used for all
the following voltage/current/diode/capacitance measurement. However, in resistance
measurement, the de-integration voltage is not fixed, and varies with the resistance to be
measured. That is, zero calibration must be re-done if the resistance to be measured
changes. For convenience, the result of zero input in voltage measurement could be used
in resistance measurement.
(9)Frequency and duty cycle
When F[0:2] = “110”, ES51999 calculates frequency and duty cycle of FREQ at the same
time. However, some more computations are required to obtain both the results. There
are three output data at this measurement: D0, D1, and D2 which can be obtained from
the serial output.
15
07/07/06
CYRUSTEK [ Cyrustek corporation ]
