AME AME811R

Analog Microelectronics, Inc.
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
AME811/AME811A/AME811R
n Key Features
n General Description
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
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-multiplexed LCD display directly.
These A/D converters are inherently versatile and accurate. They are immune to the high noise environments. 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 without any external adjustments.
n Applications
l Digital multimeter
l pH meter
l Capacitance meter
l Thermometer
l Digital Panel meter
l Photometer
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.
0.1
35
34
C REF+ C REF-
1M
AN ALOG
INPUT
31
LCD DISPLAY
2-19 SEGMENT
22-25 DRIVE
IN HI
0.01
30
32
28
47K
PO L
IN LO
BP
CO M
V+
29
27
21
MINUS SIGN
BACKPLANE
D RIVE
38
24K
BUF
0.47
0.22
20
V REF+
A/Z
36 V REF
9V
1K
V REF- 33
V- 26
INT
O SC 2
OSC 1
39
40
20M
TO ANALO G
COM MON (P32)
470K
V+
V+
20pF
40KHz
10pF
FULL SCALE IN PUT 200.0mV
V REF
100.0mV
1
Analog Microelectronics, Inc.
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
AME811/AME811A/AME811R
n Absolute Maximum Ratings
AME811
Supply Voltage (V+ to V-)
12V
Analog Input Voltage (Either inputs)
V+ to V-
Reference Input Voltage (Either inputs)
V+ to V-
Clock Input
Test to V+
Power Dis sipation
Operating Temperature
Storage Temperature
Lead Temperature (Soldering 60 seconds)
800mW
0 o C to 70 oC
-55 o C to 150 oC
300 o C
Static sensitive device. Unused devices must be stored in the conductive material.
Protect device from static discharge and static field. Stresses exceed the above Absolute Maximum
Ratings may cause permanent damage to the device. Exposure to Absolute Maximum Rating Conditions
for extended periods may affect the reliability of the device.
n Ordering Information
2
Part Number
Display
AME811CPL
LCD
AME811RCPL
LCD
AME811ACKW
LCD
Marking
AME811CPL
YYWW
AME811RCPL
YYWW
AME811ACKW
YYWW
Package
Pin Layout
Temp.Range
40 Pin PDIP
Normal
0oC to 70oC
40 Pin PDIP
Reverse
0oC to 70oC
44 Pin PQFP
Normal
0oC to 70oC
Analog Microelectronics, Inc.
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
AME811/AME811A/AME811R
n Electrical Characteristics
o
Unless otherwise noted, AME811 is specified at TA = 25 C, fclock = 48KHz. Supply voltage = 9V (V+ to V-)
Parameter
Zero Input Reading
Ratiometric Reading
Roll-Over Error
(Difference in Reading for
Equal Positive and Negative
Reading Near Full-Scale)
Linearity (Max. Deviation
From Best Straight Line Fit)
Common-Mode
Rejection Ratio
Noise (Pk-Pk Value Not
Exceeded 95% of Time)
Leakage Current at Input
Zero Reading Drift
Analog Common Voltage
(With respect to V+)
Conditions
Vin = 0V
Full-Scale = 200.0mV
Vin = Vref = 100.0mV
Min
-0
Max
Unit
+0 Digital Reading
999 999/1000 1000 Digital Reading
-Vin = +Vin ≈ 200.0mV -1
–0.2
+1
Counts
-1
–0.2
+1
Counts
Full-Scale = 200.0mV
Vcm = –1V, Vin =0V
Full-Scale = 200.0mV
Vin = 0V
Full-Scale = 200.0mV
Vin = 0V
o
o
Vin = 0V, 0 C to 70 C
25KΩ Between
Common and V+
2.8
Temp. Coeff. of Analog
25KΩ Between
Common (With respect to V+) Common and V+
o
Low Battery Flag
Test Pin Voltage
LCD Segment Drive Voltage
Backplane Drive Voltage
Typ
w0
50
µV/V
15
µV
1
10
pA
0.2
1
µV/ C
3
3.2
V
50
75
ppm/ C
7.0
5
5
5
7.7
6
6
6
V
V
V
V
o
o
o
0 C m TA m 70 C
V+ to VWith respect to V+
V+ to V- = 9V
V+ to V- = 9V
6.3
4
4
4
Notes: 1. Input voltage may exceed the supply voltages provided the input current is limited to ±100µA.
2. Dissipation rating assumes a device is mounted with all leads soldered to printed circuit board.
3
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
n Pin Configurations
4
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
Analog Microelectronics, Inc.
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
AME811/AME811A/AME811R
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
V27
(14)
35
INT
28
29
30
31
32
33
(13)
(12)
(11)
(10)
(9)
(8)
36
37
38
39
40
41
BUF
A/Z
INLO
INHI
COM
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
Analog Microelectronics, Inc.
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
AME811/AME811A/AME811R
n Pin Description (Cont.)
40-pin DIP 40-pin DIP 44-pin PQFP
Pin Number (Reverse) Pin Number
34
(7)
42
35
(6)
43
36
(5)
44
¢w
1
¢w
2
37
(4)
3
38
¢w
39
40
(3)
(2)
(1)
n Function Description
6
4
5
6
7
Symbol
Description
CREFCREF+
VREF+
DEEN
INTEN
TEST
Reference capacitor, negative terminal
Reference capacitor, positive terminal
Analog-reference input, positive terminal
De-integration status flag
Integration status flag
Display-test pin, When pulled to V+,
display should read -1888.
Positive supply voltage
Buffered OSC1
Crystal oscillator output
Crystal oscillator input
V+
OSC3
OCS2
OCS1
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
The A/D conversion has the following three phases:
1. Auto-Zero Phase
2. Integration Phase
3. De-integration Phase
Auto-Zero Phase
The INHI and INLO are shorted to analog common internally. The reference capacitor is charged to the reference voltage. A feedback loop is closed around the
system to cancel the offset voltage of buffer, integrator
and comparator.
Signal Integration phase
The converter integrates the differential voltage across
the INHI and INLO for a fixed time, 1000 system clocks.
The polarity of the signal is determined at the end of
this phase.
Reference Integration Phase
INLO is internally connected to the Analog Common,
INHI is connected across the reference capacitor with
appropriate polarity determined by the control circuit.
The integrator output will then return to zero. The time
it takes to return to zero, 1000 x VIN /VREF, is the digital representation of the analog signal.
Differential Signal Inputs (INHI & INLO)
The AME811 has true differential inputs and accepts
input signals within the input common mode voltage
range (Vcm). Typical range is from 1V above the V- to
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
1V below the V+. The integrator output can swing within
0.3 V of V+ or V- without increasing linearity errors.
Care must be exercised to make sure the integrator
output does not saturate. In a typical application, the
common mode is eliminated by connecting the INLO
to COM, Analog Common.
Differential Reference (VREF+ & VREF-)
The reference voltage can be generated anywhere
within the V+ to V-. Under a large common mode voltage, reference capacitor can gain charge during the
de-integration of a positive signal. The reference capacitor will lose charge when de-integrating a negative
input signal. The difference in reference voltage for
positive or negative input voltages can cause the
rollover error. To prevent rollover error from being induced by large common-mode voltages, reference capacitor should be large compared to stray node capacitance.
Analog Common (COM)
The Analog Common is to set a common mode voltage for the analog signal. The analog common is typically 3.0V below V+, set primary for the battery operated application. Analog common is capable to sink 20
mA. It’s source current is limited to 10 µA. Analog
common is therefore easily pulled to a more negative
voltage to override the internal reference. When supply voltage is greater than 7V, analog common can be
used as reference source with temperature coefficient
of typically 50 ppm/OC.
7
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
n Digital Block Diagrams
8
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
n Digital Section
Digital Ground
AME811 generates an internal digital ground, typically
5V below the V+.
Clock Circuit
The clock can be generated in either of the following
three methods.
1. An external oscillator connected to “OSC1”
2. A crystal between pins “OSC1” and “OSC2”
3. A R-C oscillator using “OSC1”, “OSC2” and
“OSC3”
Notes: There is no on-chip feedback resister across
osc1 and osc2.
Systems Timing
The oscillator frequency is divided by 4 prior to clocking the internal decade counters. Each conversion
takes 4000 counts or 16000 oscillator clock pulses.
The timing of each phase are as follows:
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
Auto-Zero Phase:
1000 to 3000 Counts
Signal Integration Phase:
1000 Counts (Fixed)
Reference Integration Phase :
0 to 2000 Counts
For signals less than full-scale, the unused reference
integration time is assigned to the autozero phase.
Segment Drivers
The backplane frequency is 1/800 of the oscillator clock
frequency. For example if the oscillator frequency is
48 KHz (3 conversions per second) the backplane frequency will be 60 Hz. The segment and backplane are
at the same frequency with a nominal 5 volt amplitude.
The segment is visible (ON) when the segment and the
backplane are out of phase, otherwise it is invisible
(OFF). The polarity segment is “ON” for negative analog inputs. When the TEST pin on the AME811 is pulled
to V+, all segments are turned “ON”. The display reads
-1888. During this mode the LCD segments have a
constant DC voltage impressed. DO NOT LEAVE THE
DISPLAY IN THIS MODE FOR MORE THAN SEVERAL MINUTES! LCD displays may be destroyed if
operated with DC levels for extended periods.
9
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
Test
Integration Status (INTEN)
When the TEST is pulled to V+ all segments and the
minus sign will be activated. The TEST pin is tied to
the internally generated digital ground through a 500Ω
resistor in the AME811. It is typically 5V lower than V+.
TEST pin may be used as the negative power supply
for external CMOS logic at the maximum current of 1
mA.
The INTEN is an output signal of the converter, it is
“high” during the signal integration phase. This signal
can be used as a status indicator or a control to connect the analog signal to the converter for processing.
It is available in 44 pin package.
Data Hold
When the Hold pin is connected to V+ the conversion
result will not be updated. The conversion is still free
running during the hold mode.
n Component Value Selection
Auto-Zero Capacitor (Caz)
The Caz capacitor size has some influence on system
noise. A 0.47µF capacitor is recommended for 200
mV full-scale applications. A 0.047µF capacitor is recommended for 2.0V full-scale applications. A mylar
dielectric capacitor is adequate.
10
De-integration Status (DEEN)
The DEEN is an output signal of the converter, it is
“high” during the reference de-integration phase. The
period of the DEEN is proportional to the conversion
result. Users may calculate the conversion result by
counting the number of clock pulse on the OSC3 pin
when DEEN is “high”. The conversion result is equal
to (N /4) - 1/2 where N is the number of the pulse at the
OSC3 pin. It is available in 44 pin package.
Reference Capacitor (Cref)
A 0.1µF capacitor is acceptable when “INLO” is tied
to analog common. If a large common-mode voltage
exists and the application requires 200 mV full-scale,
increase Cref to 1.0 µF. A mylar dielectric capacitor is
adequate.
Analog Microelectronics, Inc.
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
AME811/AME811A/AME811R
Integrating Capacitor (Cint)
Cint should be selected to maximize the integrator output 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 expression 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 recommended.
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 currents 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 l l sc a l e
200.0m V
2.000V
Caz
R in t
0.47µF
47 K Ω
0.047µF
470 K Ω
C in t
0.22µF
V re f
100.0m V
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 signalintegrate 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 l l -S c a l e V o l ta g e
V re f
200.0 m V
100.0 m V
2 .0 0 0
1 .0 0 0
V
V
In some applications a scale factor other than unity may
exist between a transducer output voltage and the required digital reading. Assume, for example, a pressure 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 transducer 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 between INHI and COMMON and the variable offset voltage 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 annunciator for AME811.
11
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
n Typical Applications
12
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
13
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
14
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
www.analogmicro.com
E-Mail: info@analogmicro.com
Life Support Policy:
These products of Analog Microelectronics, Inc. are not authorized for use as critical components in lifesupport devices or systems, without the express written approval of the president
of Analog Microelectronics, Inc.
Analog Microelectronics, Inc. reserves the right to make changes in the circuitry and specifications of its
devices and advises its customers to obtain the latest version of relevant information.
 Analog Microelectronics, Inc. , July 2001
Document: 1021-duc-B-0704
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Tel : (408) 988-2388
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