ES51999
4 3/4 and 5 3/4 A/D AUTO
TINT
1
1
VIN (t)dt =
×VREF ×TDINT
∫
0
Buf × C int
Buf × C int
where, VIN (t) = input signal
VREF = reference voltage
TINT = integration time (fixed)
TDINT = de-integration time (proportional toVIN (t) )
If VIN (t) is a constant, we can rewrite above equation:
TINT
TDINT
=
×VIN
VREF
Besides the INT phase and DINT phase, ES51999 exploits auto zero (AZ) phase and zero
integration (ZI) phase to achieve accurate measurement. In AZ phase, the system offset is
stored. The offset error will be eliminated in DINT phase. Thus a higher accuracy could
be obtained. In ZI phase, the internal status will be recovered quickly to that of zero input.
Thus the succeeding measurements won’t be disturbed by current measurement
especially in case of overload.
Cint
input
signal
Buf
Raz
reference
voltage
integrator
output
input signal < 0
input signal > 0
different
input
integration
time
fixed slope
fixed slope
different
input
integration
time
Fixed
integration deintegration
time time
Variable
Fixed
integration deintegration
time time
Variable
Figure 2.1 the structure of dual-slope integrator and its output waveform.
As mentioned above, the measurement cycle of ES51999 contains four phases:
(1) auto zero phase (AZ)
(2) input signal integration phase (INT)
(3) reference voltage integration phase (DINT)
10
07/07/06
CYRUSTEK [ Cyrustek corporation ]
