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PDF AS8500 Data sheet ( Hoja de datos )
| Número de pieza | AS8500 | |
| Descripción | Universal multi pupose data aquisition system | |
| Fabricantes | austriamicrosystems AG | |
| Logotipo |  |
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1.1
AS8500
2 Universal multi pupose data aquisition system
3
www.DataSheet4U.com
Data Sheet
DATA SHEET
1 Features
16 bits resolution
differential inputs
Single + 5V supply
Low power 15 mW
SOIC16 package
16 kHz maximum sampling frequency
internal temperature measurement
internal reference
programmable current sources
digital comparator
active wake-up
PGA gains 6, 24, 50, 100
Zero offset
Zero offset TC
Extremely low noise
Internal oscillator with comparator for active wake up
3-wire serial interface, !P compatible
temperature range – 40 to + 125 °C
2 Applications
battery management for automotive systems
power management
mV/µ V-meter
thermocouple temperature measurement
RTD precision temperature measurement
high-precision voltage and current measurement
3 General description
The AS8500 is a complete, low power data acquisition system
for very small signals (i.e. voltages from shunt resistors,
thermocouples) that operates on a single 5 V power supply. The
chip powers up with a set of default conditions at which time it
can be operated as a read-only-converter. Reprogramming is at
any time possible by just writing into two internal registers via
the serial interface.
The AS8500 has four ground refering inputs which can be
switched separately to the internal PGA. Two input channels can
also be operated as a fully differential ground free input. The
system can measure both positive and negative input signals.
The PGA amplification ranges from 6 to 100 which enables the
system to measure signals from 7mV to 120 mV full scale range
with high accuracy, linearity and speed.
The chip contains a high precision bandgap reference and an
active offset compensation that makes the system offset free
(better than 0,5 !V) and the offset-TC value negligible. The built-
in programmable digital filter allows an effective noise
suppression if the high speed is not necessary in the application.
The input noise density is only 35 nV / Hz and due to
ETR
ETS
VBAT
RSHH
RSHL
REF
AGND
VDDA
VSSA
INTERNAL TEMPERATURE
1.26 V
REFERENCE
INPUT MUX
CHOPPER
PROTECTION
BUF
16 BIT - CONVERTER
PGA
and
LEVEL SHIFT
CALIBRATION
DATA
DSP
CONTROLLER
FILTER
INT. CLOCK
TIMER
COMPARATOR
CURRENT
SOURCES
SERIAL INTERFACE / CONTROL REGISTERS
VDDD
VSSD
CLK
EZPRG
SCLK
SDAT
Figure 1: Functional Block Diagram
INTN
the high internal chopping frequency the system is free of 1/f-noise down
to DC.The 0-10 Hz noise is typical below 1 µ V i.e. as good or better than
any other available chopper amplifier.
For high speed synchronous measurements the chip can run in an
automatic switching mode between two input channels with pre-
programmed parameter sets.
The circuit has been optimised for the application in battery management
systems in automotive systems. As a front end data acquisition system it
allows an high quality measurement of current, voltage and temperature
of the battery.
With a high quality 100 !" resistor the system can handle the starter
current of up to 1500 A, a continuous current of # 300 A as well as the
very low idle current of a few mA in the standby mode.
For external temperature measurement the chip can use a wide variety of
different temperature sensors such as RTD, PTC, NTC, thermocouples or
even diodes or transistors. A built-in programmable current source can be
switched to any input and activate these sensors without the need of
other external components.
The measurement of the chip temperature with the integrated internal
temperature sensor allows in addition the temperature compensation of
sensitive parameters which increases the total accuracy considerably.
The flexibility of the system is further increased by a digital comparator
that can be assigned to any measured property
(current, voltage, temperature) and an active wake-up in the sleep-mode.
All analog input-terminals can be checked for wire break via the SDI-
interface.
Revision 1.2, 08-Junel-06
www.austriamicrosystems.com
Page 1 of 41
1 page  
AS8500 - Data Sheet
6 Electrical characteristics
austriamicrosystems
www.DataSheet4U.com
VDDA=5V +/-0.1 V, fclk=8.192 MHz, chopping ratio MM=4 (see 7.5.3), oversampling frequency=2.048 MHz, oversampling ratio=128
temperature range : -40 to 125°C if not otherwise noted
symbol
parameter
conditions
min typ
max units
input characteristics
for gain 1 the input signal is connected directly to th input of the converter, this is not possible for the RSHH-RSHL
G1 input
Gain gains of PGA
6, 24, 50, 100
AC_g6
Accuracy at gain 6
0 to 85 °C
0.4 % @-120mV
-40 to 125°C
1.0 % @-120mV
AC_g24
Accuracy at gain 24
0 to 85 °C
0.2 % @+-20mV
-40 to 125°C
0.6 % @+-20mV
AC_g50
Accuracy at gain 50
0 to 85 °C
1 % @+-10mV
AC_g100
Accuracy at gain 100
0 to 85 °C
1 % @+-5mV
Vin
input voltage ranges
G1
-300 to + 800
mV
(with reference to RSHL) G6
+/- 120
mV
G24
+/- 30
mV
G50
+/- 15
mV
G100
+/- 7.5
mV
1)
2)
2),3)
2)
2) 3)
2)4)
2)4)
5)
6)
6)
7)
7)
Notes:
1) the absolute gain values are subjected to a manufacturing spread of +/-30%
2) Accuracy relies on bandgap characteristic, on the gain variation over temperature and on the trimm information. To achieve optimum performance,
the circuit may be trimmed by the user for best temperature stability by writting aproporiate data to the TRR register (see sections 7.4 and 7.5)
Default content of TRR register is 17.
3) due to a nonlinear behaviour of the gain and reference voltage over temperature the accuracy is lower for the extended temperature range.
4) It is recommended to use these gain settings only for applications in the temperature range 0 t0 85°C
therefore it is recommended to use these gain settings only for applications in the temperature range 0 to 85°C.
5) this gain range is not using the internal PGA, the input is directely connected to the AD-converter. Therefore the input resistance is lower then for
other gain ranges.
It has been designed mainly for positive input voltages up to 0.8 V i.e. for measurements of temperature with transistors and diodes.
The limitation for negative input voltages is due to the onset of conduction of the input protection diodes.
6) the ASSP is optimised for G6 and G24 concerning linearity, speed and TC, therefore these ranges are recommended whenever possible.
7) because of higher TC value at elevated temperature G50 and G100 are recommended for applications in the temperature range 0 to 85°C
Revision 1.2, 08-Junel-06
www.austriamicrosystems.com
Page 5 of 41
5 Page 
AS8500 - Data Sheet
austriamicrosystems
Writing into subregister TRIMBV of TRR changes the absolute value linearly by 5.1 mV per digit as shown in the followinwgwgwra.pDhaatnadSdheesecrti4bUed.cinomfull
detail in 7.5.7
as function of temperature
1,36
1,32
1,28
1,24
1,20
1,16
0
75 °C
24 °C
5 10 15 20 25 30
content of TRIMBV in bits
Trimming the TC value is similarly done by writing into subregister TRIMBTC. Since the TC trimming is also changing the absolute value it is important
to trim the TC first and then the absolute value.
200
150
100
50
0
-50
-100
-150
-200
-250
0
temperature coefficient as function of TRIMBTC setting
change 12.7 ppm/K
per step
5 10 15 20 25 30 35
setting of subregister TRIMBTC of TRR
The TC trimming also opens the unique possibility to change the TC-value within the time of reprogramming of the TRR-register (i.e. within µ sec) to
allow the compensation of
different TC-values of the external circuitry for different channels.
In addition it can be used for very fast autocalibration of the total TC of a given channel. An external reference voltage is applied to the channel to be
checked. Then all numbers from 0 to 31 are written into subregister TRIMBTC and a reading is done for the input voltage and the internal temperature
as well. The same is repeated at any temperature above RT. From these data the TRIMBTC setting for a minimum drift can be easily calculated.
Revision 1.2, 08-Junel-06
41
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| PDF Descargar | [ Datasheet AS8500.PDF ] | |
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