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PDF AS8168 Data sheet ( Hoja de datos )
| Número de pieza | AS8168 | |
| Descripción | Single Phase Average Energy Metering IC | |
| Fabricantes | austriamicrosystems AG | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de AS8168 (archivo pdf) en la parte inferior de esta página. Total 30 Páginas | ||
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AS8168
Single Phase Average Energy Metering IC
with On-Chip Calibration, Stepper Motor Drive and LED Output
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DATA SHEET
Features
- Extremely accurate, surpassing the accuracy
requirements of the IEC1036 Specification with less
than 0.1% error over a 1000 : 1 dynamic range
- On-chip programmable current input gain suitable for
use with low-resistance shunt resistor or current
transformer
- On-chip programming for output pulse rate selection.
- On-chip calibration eliminates the need for an external
resistor network or trim-potentiometer
- Programmable on-chip creep prevention under no-load
condition
- All on-chip programmable functions may be
reprogrammed a second time
- Outputs directly drive an electromechanical counter or
a two phase stepper motor counter and consumption
LED indicator
- Fast calibration pulse output for high speed manual or
automated calibration
- On-chip voltage reference and power supply
monitoring
- Bi-directional or unidirectional energy measurement,
with direction indication output available
Description
The AS8168 is a very accurate single-phase bi-directional
average energy measurement integrated circuit, which
surpasses all the accuracy requirements for IEC1036
alternating current static watt-hour meters. The measured
energy is converted into pulses with the number of output
pulses being proportional to the measured energy.
The AS8168 is ideal for use in ‘stand alone’ kWh meter
applications, where the IC directly drives an
electromechanical counter with a two-phase stepper
motor, or for more complex meter applications, the
AS8168 interfaces directly to a micro-controller.
The highly integrated AS8168 design includes all the
required functional blocks. The blocks comprise of analog
to digital converters (ADC) for the voltage and current
channels, digital filters, a digital signal processing block, a
control block and non-volatile calibration memory for the
on-chip programming. The on-chip programming enables
the setting of the current input gain, the anti-creep
threshold, the output pulse rates and the system
calibration. The high level of integration ensures a
minimum number of non-critical external components are
required.
The on-chip anti-creep circuit ensures that the AS8168
does not output pulses when the meter is in a no-load
condition and that the IEC1036 anti-creep test
requirements are fully complied with, for both direct or
transformer connection meters.
The AS8168 offers three different pulse outputs. A stepper
motor drive output for directly driving a stepper motor
display, a LED output for energy consumption indication
and a dedicated high frequency output for fast single point
system calibration.
The AS8168 is available in either surface mount SOIC-18
or dual-in-line DIP-18 packages.
Block Diagram
AGND
Buffer
VP
Σ∆-mod
VN
IP
Σ∆-mod
IN
XIN
XOUT
VREF
Crystal
Osc
POR
Non-volatile
Calibration
Digital
Filter
Digital
Filter
Power
Calculation
Control
CAL
LED
MON
MOP
Figure 1 Block diagram of the AS8168
Revision 1.2, 11-Feb-05
Page 1 of 30
1 page  
Data Sheet AS8168
0,5
0,4
0,3
0,2
0,1
0
-0,1
-0,2
-0,3
-0,4
-0,5
45 50 55 60 65
fmains[Hz]
Graph 7: Error as a % of reading with mains frequency variation
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Functional Description
The AS8168 is a CMOS mixed signal integrated circuit that measures electrical power over a dynamic range of 1000:1, to an
accuracy of better than 0.1%.
The AS8168 comprises of standard functional blocks including two sigma/delta modulators, which convert the analog voltage
and current input signals into digital signals. The voltage and current signals are then digitally filtered, which eliminates
offsets thus enabling a single point calibration cycle. A power calculation block calculates the active energy value. An on-chip
voltage reference (30ppm/K typical), oscillator and non-volatile calibration registers and control block for programming the
AS8168 completes the core functional elements.
Programming of the AS8168 enables the device to be configured to suite the users specific input and output requirements
and allows for fast and efficient calibration. The AS8168 device provides the user with two complete opportunities to
programme the device. The following parameters may be programmed via the on-chip non-volatile memory:
- Current channel input gain
- Calibration pulse output frequency
- Stepper motor output drive frequency
- LED output frequency
- Anti-creep threshold
- Calibration constant
A detailed description of the versatility of the AS8168 is given below.
Current Inputs for Energy Calculation
The current channel input consisting of inputs IP and IN is differential and connected to a low resistance shunt or current
transformer, in series with the load. The current input signal level may be programmed by means of an on-chip
programmable gain amplifier (PGA). The gain is selected through the programming of 2 bits in the on-chip memory as
follows:
Parameter: Gain
Setting Voltage
Gain
1 1 20
1 0 16
01
00 4
Input Voltage
-30mVpeak≤VIP≤30mVpeak
-38mVpeak≤VIP≤38mVpeak
-150mVpeak≤VIP≤150mVpeak
Comments
Shunt mode
CT mode
CT mode
Revision 1.2, 11-Feb-05
Page 5 of 30
5 Page 
Data Sheet AS8168
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Direction Input (DIRI)
The direction input pin (DIRI) is used to program the AS8168 for either bi-directional energy measurement, or unidirectional
measurement.
Bi-directional measurement mode ensures that all energy is measured regardless of the direction of the current through the
current sensor. In unidirectional energy measurement mode, all negative going energy is suppressed and thus excluded from
the accumulated energy value.
The programming conditions for the DIRI pin are given below:
DIRI Pin
0
1
Mode
Unidirectional
Bi-directional
The default condition, when the DIRI pin is not connected is bi-directional energy measurement, as the DIRI pin has an on-
chip pull-up resistor.
Direction Output (DIRO)
The Direction Output pin (DIRO) is a logic output providing information on the direction of the current flow through the current
sensor. The DIRO output may be used to directly drive an LED to indicate a reversal in the direction of current flow.
The conditions that will initiate a change in the DIRO logic output are given below:
If DIRI = 1 (bi-directional mode) DIRO changes only when there is a pulse at CAL or LED.
If DIRI = 0 (unidirectional mode) DIRO changes at a zero-crossing when not in anti-creep.
The timing diagram below demonstrates the operation of the DIRO output and the pulse outputs (MOP/MON, CAL and LED)
relative to the sign of the measured energy and the setting of the DIRI input.
For illustration purposes, the timing diagram below only shows the LED output.
1234
VP
IP
DIRI
LED
DIRO
Figure 5 Timing diagram for the DIRI and DIRO functions
Revision 1.2, 11-Feb-05
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11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet AS8168.PDF ] | |
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