ame7106 AME, Inc., ame7106 Datasheet - Page 12

• Manufacturer Part Number: ame7106
• Description: 3-1/2 Digit A/d Converter High Accuracy, Low Power
• Manufacturer: AME, Inc.

n Component Value Selection
Auto-Zero Capacitor (Caz)
systemnoise. A 0.47 F capacitor is recommended for 200mV
full-scale applications. A 0.047 F capacitor is recommended
for 2.0V full-scale applications. A mylar dielectric capacitor
is adequate.
Reference Capacitor (Cref)
analog common. If a large common-mode voltage exists
and the application requires 200 mV full-scale, increase Cref
to 1.0 F. A mylar dielectric capacitor is adequate.
Integrating Capacitor (Cint)
put voltage swing without causing output saturation. A +2V
full-scale integrator output swing is recommended if “ ANA-
LOG COMMON” is used as signal reference. For 3 read-
ings/second (fosc = 48 KHz) a 0.22 F value is suggested.
If a different oscillator frequency is used, Cint must be
changed in inverse proportion to maintain the nominal 2V
integrator swing. An exact expression for Cint is:
rollover error. A polypropylene capacitor is recommend-ed.
Integrating Resistor (Rint)
A output stage with 100 A quiescent current. The integra-
tor and buffer can supply 20 A drive currents with negligible
linearity errors. Rint is chosen to keep the output stage in
the linear region. For a 200mV full-scale, it is 47K ; 2.0V
full-scale requires 470K .
12
AME7106 / 7106A / 7106R
AME7107 / 7107A / 7107R
The Caz capacitor size has some influence on
A 0.1 F capacitor is acceptable when “ INLO” is tiedto
Cint should be selected to maximize the integrator out-
Cint = [(4000)(1/fosc)(Vfs/Rint)] / Vint
Cint must have low dielectric absorption to minimize
The input buffer amplifier and integrator both have a class
where:
fosc= Oscillator clock frequency
Vfs = Full-scale input voltage
Rint = Integrating resistor
Vint = Desired full-scale integrator output swing
AME, Inc.
Summary of component selection:
Oscillator Components
R-C Oscillator
Cosc is selected by using the equation:
integrate period should be a multiple of line period. The
optimum oscillator frequencies for 60 Hz and 50 Hz re-
jection are listed as follows:
Reference Voltage Selection
signal be twice the reference voltage.
may exist between a transducer output voltage and the
required digital reading. Assume, for example, a pres-
sure transducer output is 600 mV for 2000 Ib/in
than dividing the input voltage by three the reference volt-
age should be set to 300 mV. This permits the trans-
ducer input to be used directly. The integrator resistor
would be 120K
system with variable tare, the offset reading can be gen-
erated by connecting the voltage transducer between INHI
and COMMON and the variable offset voltage between
COMMON and INLO.
A 100 K
For fosc of 48KHz, Cosc is 100pF nominally.
To achieve maximum line noise rejection, the signal-
For 60 Hz rejection:
For 50 Hz rejection:
A full-scale reading (2000 counts) requires the input
In some applications a scale factor other than unity
Note: fosc = 48 KHz
40KHz, 48KHz, 60KHz etc.
40KHz, 50KHz, 66-2/3KHz etc.
Full scale
High Accuracy, Low Power
Full-Scale Voltage
fosc = 0.45/(RC)
Caz
Rint
Cint
Vref
3-1/2 Digit A/D Converter
Rosc is recommended for all frequencies.
200.0mV
2.000V
In some temperature and weighting
200.0mV
100.0mV
0.47 F
0.22 F
47K
100.0mV
1.000V
0.047 F
2.000V
470K
0.22 F
1.000V
Vref
2
. Rather
Rev.H.02