ES51993
11,000 Counts ADC
Function description
1. Dual Slope A/D－Four Phases Timing
ES51993 is a dual-slope analog-to-digital converter (ADC). Figure 1 is a structure
of dual-slope integrator. Its measurement cycle has two distinct phases: input signal
integration (INT) phase and reference voltage integration (DINT) phase.
In INT phase, the input signal is integrated for a fixed time period, then A/D
enters DINT phase in which an opposite polarity constant reference voltage is
integrated until the integrator output voltage becomes to zero. Since both the time
period for input signal integration and the amount of reference voltage are fixed, thus
the de-integration time is proportional to the input signal. Hence, we can define the
mathematical equation about input signal, reference voltage integration (see Figure 1.):
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) )
Cint
input
signal
Buf
reference
voltage
integrator
output
RAZ
BufX10
RAZ
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 1. the structure of dual-slope integrator and its output waveform.
If VIN (t) is a constant, we can rewrite above equation:
TINT
VREF
TDINT
=
×VIN
4
06/09/20
CYRUSTEK [ Cyrustek corporation ]
