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PDF AME811R Data sheet ( Hoja de datos )
| Número de pieza | AME811R | |
| Descripción | 3-1/2 Digit A/D Converter - Low Power With HOLD And Differential Reference Inputs | |
| Fabricantes | Analog Microelectronics | |
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Analog Microelectronics, Inc.
AME811/AME811A/AME811R
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
n Key Features
l 100µV Resolution
l High Impedance Differential Inputs
l Differential Reference
l Drive LCD Directly
l Three New Convenient Features
(AME811A Only)
l Low-Battery Indication
l Integration Status Indication
l De-Integration Status Indication
n Applications
l Digital multimeter
l pH meter
l Capacitance meter
l Thermometer
l Digital Panel meter
l Photometer
n General Description
The AME811 family are high performance, low power.
3-1/2 digit, dual-slope integrating A/D converters, with
on-chip display drivers. The AME811 is designed for a
single battery operated system, will drive non-multi-
plexed LCD display directly.
These A/D converters are inherently versatile and ac-
curate. They are immune to the high noise environ-
ments. The true differential high impedance inputs and
differential reference are very useful for making
ratiometric measurement, such as resistance, strain
gauge and bridge transducers. The built-in auto-zero
feature automatically corrects the system offset with-
out any external adjustments.
Low-battery flag, integration and de-integration status
flags are three additional features which are available
in the 44-pin package, AME811ACKW.
n Typical Operating Circuit * For the operating circuit of the reverse-pins version, please refer to
pin configuration on page 4 and pin description on page 5 & 6.
1M
AN ALOG
IN PU T
0.01
47K
0.22
0.1
35 34
CREF+ CREF-
31 IN HI
2-19 SEGMENT
22-25 DRIVE
LCD DISPLAY
30 IN LO
32 COM
POL 20
BP 21MINUS SIGN
V+ 38
BACKPLANE
D RIVE
28 BUF
0.47
29 A/Z
27 INT
24K
VREF+ 36 VREF
VREF- 33
V- 26
1K
9V
O SC2
OSC1
39
470K
20M
40
TO ANALO G
COM MON (P32)
V+
20pF
40KHz
V+
10pF
FULL SCALE IN PUT 200.0mV
V REF
100.0mV
1
1 page  
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
n Pin Description
40-pin DIP 40-pin DIP 44-pin PQFP Symbol
Pin Number (Reverse) Pin Number
1 (40) 8 HOLD
2 (39) 9 D1
3 (38) 10 C1
4 (37) 11 B1
5 (36) 12 A1
6 (35) 13 F1
7 (34) 14 G1
8 (33) 15 E1
9 (32) 16 D2
10 (31)
17 C2
11 (30)
18 B2
12 (29)
19 A2
13 (28)
20 F2
14 (27)
21 E2
15 (26)
22 D3
16 (25)
23 B3
17 (24)
24 F3
18 (23)
25 E3
19 (22)
26 AB4
20 (21)
27 POL
21 (20)
28 BP
22 (19)
29 G3
23 (18)
30 A3
24 (17)
31 C3
25 (16)
32 G2
¢w 33 LB
26 (15)
34 V-
27 (14)
35 INT
28 (13)
29 (12)
30 (11)
31 (10)
32 (9)
33 (8)
36 BUF
37 A/Z
38 INLO
39 INHI
40 COM
41 VREF-
Description
HOLD pin, Logic 1, Holds Display
Units-digit D-segment driver
Units-digit C-segment driver
Units-digit B-segment driver
Units-digit A-segment driver
Units-digit F-segment driver
Units-digit G-segment driver
Units-digit E-segment driver
Tens-digit D-segment driver
Tens-digit C-segment driver
Tens-digit B-segment driver
Tens-digit A-segment driver
Tens-digit F-segment driver
Tens-digit E-segment driver
Hundreds-digit D-segment driver
Hundreds-digit B-segment driver
Hundreds-digit F-segment driver
Hundreds-digit E-segment driver
Thousands-digit, B&C segments driver
Negative-polarity driver
LCD backplane driver
Hundreds-digit G-segment driver
Hundreds-digit A-segment driver
Hundreds-digit C-segment driver
Tens-digit G-segment driver
Low-battery flag segment driver
Negative power supply voltage
Integrator output. Connection point for
integration capacitor.
Integrator resistor connection-point.
Auto-zero capacitor connection-point
Analog-input low
Analog-input high
Analog-common
Analog-reference input, negative terminal
5
5 Page 
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
Integrating Capacitor (Cint)
Cint should be selected to maximize the integrator out-
put voltage swing without causing output saturation. A
± 2V full-scale integrator output swing is recommended
if “ANALOG COMMON” is used as signal reference.
For 3 readings/second (fosc = 48 KHz) a 0.22 µF 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 expres-
sion for Cint is:
Cint = [(4000)(1/fosc)(Vfs/Rint)] / Vint
where:
fosc= Oscillator clock frequency
Vfs = Full-scale input voltage
Rint = Integrating resistor
Vint = Desired full-scale integrator output swing
Cint must have low dielectric absorption to minimize
rollover error. A polypropylene capacitor is recom-
mended.
Integrating Resistor (Rint)
The input buffer amplifier and integrator both have a
class A output stage with 100 µA quiescent current.
The integrator and buffer can supply 20 µA drive cur-
rents with negligible linearity errors. Rint is chosen to
keep the output stage in the linear region. For a 200mV
full-scale, it is 47KΩ; 2.0V full-scale requires 470KΩ.
Summary of component selection:
F u ll sc a le
Caz
R in t
C int
V re f
200.0m V
0.47µF
47 K Ω
0.22µF
100.0m V
2.000V
0.047µF
470 K Ω
0.22 µF
1.000V
Note: fosc = 48 KHz
Oscillator Components
R-C Oscillator
A 100 KΩ Rosc is recommended for all frequencies.
Cosc is selected by using the equation:
fosc = 0.45/(RC)
For fosc of 48KHz, Cosc is 100pF nominally.
To achieve maximum line noise rejection, the signal-
integrate period should be a multiple of line period. The
optimum oscillator frequencies for 60 Hz and 50 Hz
rejection are listed as follows:
For 60 Hz rejection:
40KHz, 48KHz, 60KHz etc.
For 50 Hz rejection:
40KHz, 50KHz, 66-2/3KHz etc.
Reference Voltage Selection
A full-scale reading (2000 counts) requires the input
signal be twice the reference voltage.
F u ll-S ca le V o lta g e
200.0 m V
2.000 V
V re f
100.0 m V
1.000 V
In some applications a scale factor other than unity may
exist between a transducer output voltage and the re-
quired digital reading. Assume, for example, a pres-
sure transducer output is 600 mV for 2000 Ib/in2. Rather
than dividing the input voltage by three the reference
voltage should be set to 300 mV. This permits the trans-
ducer input to be used directly. The integrator resistor
would be 120KΩ. In some temperature and weighting
system with variable tare, the offset reading can be
generated by connecting the voltage transducer be-
tween INHI and COMMON and the variable offset volt-
age between COMMON and INLO.
Low Battery Flag (LB)
The low battery flag is set when the supply voltage (V+
to V-) is lower than seven volts, typical. Once the LB is
set, the waveform of the LB will be out of phase with
the BP (Back Plane) to turn on a low battery annuncia-
tor for AME811.
11
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet AME811R.PDF ] | |
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