Analog Microelectronics, Inc.
AME811/AME811A/AME811R
nn
n Key Features
nn
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
nn
n Applications
nn
l Digital multimeter
l pH meter
l Capacitance meter
l Thermometer
l Digital Panel meter
l Photometer
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
nn
n General Description
nn
The AME811 family are high performance, low power.
3-1/2 digit, dual-slope integrating A/D converters, with
on-chip display drivers. The AME81 1 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.
Low-battery flag, integration and de-integration status
flags are three additional features which are available
in the 44-pin package, AME811ACKW.
nn
n Typical Operating Circuit
nn
1M
ANALOG
INPUT
0.01
47K
0.47
0.22
V+ V+
* 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
C
REF+
31
30
32
28
29
27
470K
20pF 10pF
REF-
IN H I
IN LO
COM
BUF
A/Z
INT
OSC OSC
2-19
22-25
POL
BP
V+
V
REF+
V
REF-
V-
21
20M
40KHz
4039
SEGMENT
DRIVE
20
MINUS S IGN
21
38
36
33
26
LCD DISPLAY
BACKPLANE
DRIVE
24K
V
REF
1K
COM MON (P32)
FU LL SCAL E INPUT 200.0mV
V
9V
TO ANALO G
REF
100 .0m V
1
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
nn
n Absolute Maximum Ratings
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AME811
Su pply V olt age (V+ t o V-) 12V
Analog Input Volt age (E ither inputs ) V+ to V Referenc e Input V oltage (E ither inputs ) V+ t o V Clock Input Test to V +
Po wer Diss ipation 800mW
o
Operating Temperature 0
St orage Temperature -55
Lead Temperature (Soldering 60 sec onds )
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.
C to 70oC
o
C to 150oC
o
300
C
nn
n Ordering Information
nn
Part Number Display Marking Package Pin Layout Temp.Range
AM E 811CPL LCD
AM E 811RCPL LCD
AME811ACKW LCD
AM E811CPL
YYWW
AM E811RCPL
YYWW
AME811ACKW
YYWW
40 Pin P DIP Normal
40 Pin P DIP Reverse
44 Pin P QFP Normal
o
0
C to 70oC
o
0
C to 70oC
o
0
C to 70oC
2
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
With HOLD And Differential Reference Inputs
nn
n Electrical Characteristics
nn
Unless otherwise noted, AME81 1 is specified at TA = 25oC, fclock = 48KHz. Supply voltage = 9V (V+ to V-)
Parameter Conditions Mi n Typ Max Unit
Zero Input Reading
Ratiometric Reading Vin = Vref = 100.0mV 999 999/1000 1000 Digital Reading
Roll-Over Error
(Differenc e in Reading for
Equal Positive and Negative
Reading Near Full-Scale)
Linearity (Max. Deviation
From Best Straight Line Fit)
Common-Mode Vcm = –1V, Vin =0V
Rejecti on Ratio Full-Scale = 200.0mV
Noise (Pk-Pk Value Not Vin = 0V
Exceeded 95% of Time) Full-Scale = 200.0mV
Leakage Current at Input Vin = 0V 1 10 pA
Vin = 0V -0 w 0 +0 Digital Reading
Full-Scale = 200.0mV
-Vin = +Vin ≈ 200.0mV
Full-Scale = 200.0mV
3-1/2 Digit A/D Converter - Low Power
Counts+1–0.2-1
-1 –0.2 +1 Counts
µ
50
15
V/V
µ
V
Zero Reading Drift Vin = 0V, 0oC to 70oC0.21µV/oC
Analog Common Voltage 25KΩ Between
(With respect to V+) Common and V+
Temp. Coeff. of Analog
Common (With res pect to V+) Common and V+
Low Battery Flag V+ to V- 6.3 7.0 7.7 V
Test Pin Voltage With respect to V+ 4 5 6 V
LCD Segment Drive Voltage V+ to V- = 9V 4 5 6 V
Backplane Drive Voltage V+ to V- = 9V 4 5 6 V
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.
25KΩ Between
0oC m TA m 7 0oC
2.8 3 3.2
50 75
V
ppm/oC
3
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
nn
n Pin Configurations
nn
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
4
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
nn
n Pin Description
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40-pin DIP 40-pin DIP 44-pin PQFP Symbol Description
Pin Number (Reverse) Pin Number
1 (40) 8 HOLD HOLD pin, Logic 1, Holds Di splay
2 (39) 9 D1 Units-digi t D-segment driver
3 (38) 10 C1 Units-di git C-segment driver
4 (37) 11 B1 Units-digi t B- segment driver
5 (36) 12 A1 Units-digi t A- segment driver
6 (35) 13 F1 Units-digit F- segment driver
7 (34) 14 G1 Units-digit G- segment driver
8 (33) 15 E1 Units-digi t E- segment driver
9 (32) 16 D2 Tens-digit D-segment dr iver
10 (31) 17 C2 Tens-digit C-segment driver
11 (30) 18 B2 Tens-digit B- segment driver
12 (29) 19 A2 Tens-digit A- segment driver
13 (28) 20 F2 Tens-digi t F- segment driver
14 (27) 21 E2 Tens-digit E- segment driver
15 (26) 22 D3 Hundreds-digit D-segment driver
16 (25) 23 B3 Hundreds-digi t B- segment driver
17 (24) 24 F3 Hundreds- di git F-segment dr iver
18 (23) 25 E3 Hundreds-digi t E- segment driver
19 (22) 26 AB4 Thousands-di gi t, B &C segments driver
20 (21) 27 POL Negative-polarity driver
21 (20) 28 BP LC D backplane driver
22 (19) 29 G3 Hundreds- di git G-segment dri ver
23 (18) 30 A3 Hundreds-digi t A- segment driver
24 (17) 31 C3 Hundreds-digit C-segment driver
25 (16) 32 G2 Tens-digit G- segment driver
¢w 33 LB Low-battery f lag segment driver
26 (15) 34 V- Negative power supply voltage
27 (14) 35 INT Integrator output. Connec tion point for
integration capacitor.
28 (13) 36 BUF Integrator r esi stor connection-point.
29 (12) 37 A/Z Auto-zero capaci tor connection-point
30 (11) 38 INLO Analog-input low
31 (10) 39 INHI Analog-input high
32 (9) 40 COM Analog-common
33 (8) 41 VREF- Analog-referenc e input, negative ter minal
5
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
With HOLD And Differential Reference Inputs
nn
n Pin Description (Cont.)
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40-pin DIP 40-pin DIP 44-pin PQFP Symbol Descr iption
Pin Number (Reverse) Pin N umber
34 (7) 42 CREF- Refere nce capacitor, negative terminal
35 (6) 43 CREF+ Refer e nce capacitor, positi ve termina l
36 (5) 44 VREF+ Analog-refe renc e input, po sitive terminal
¢w 1 DEEN D e-integration status flag
¢w 2 INTEN Integration status f lag
37 (4) 3 TE ST D isplay-test pin, When pulled to V+ ,
38 (3) 4 V+ Positive supply voltage
¢w 5 OSC3 Bu f fer ed OSC1
39 (2) 6 OCS2 C rystal oscillator ou tput
40 (1) 7 OCS1 C rystal oscillator input
3-1/2 Digit A/D Converter - Low Power
display should read - 18 88.
nn
n Function Description
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6
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
nn
n Digital Block Diagrams
nn
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
8
Analog Microelectronics, Inc.
AME811/AME811A/AME811R
nn
n Digital Section
nn
Digital Ground
AME81 1 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
Aut o- Zero Phas e: 1000 t o 3000 Counts
Si gnal Integrati on P hase: 1000 Count s (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 AME81 1 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 LEA VE 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
Test
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 AME81 1. 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.
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.
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
Integration Status (INTEN)
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.
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.
nn
n Component Value Selection
nn
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
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.
µ
µ
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:
Fu ll sca le 200.0m V 2.000V
Caz 0.47
Rint
Cint 0.22
V ref 100.0m V 1.000V
Note: fosc = 48 KHz
47 K
F 0.047µF
Ω
F 0.22 µF
470 K
Ω
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
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.
Full-Scale Voltage Vref
200.0 m V 100.0 m V
2.000 V 1.000 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
nn
n Typical Applications
nn
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
12
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
3-1/2 Digit A/D Converter - Low Power
With HOLD And Differential Reference Inputs
14
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 life-
support 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
Corporate Headquarters Asia Pacific Headquarters
Analog Microelectronics, Inc. AME, Inc.
3100 De La Cruz Blvd. Suite 201 2F, 187 Kang Chien Road, Nei-Hu District
Santa Clara, CA. 95054-2046 Taipei 114, Taiwan, R.O.C.
Tel : (408) 988-2388 Tel : 886 2 2627-8687
Fax: (408) 988-2489 Fax : 886 2 2659-2989
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