AS8267 / AS8268
Single-Phase 2-Current Energy Measurement Integrated Circuits
with Microcontroller, RTC, Programmable Multi-Purpose I/Os,
LCD Driver and On-Chip FLASH Memory
DATA SHEET
1. Key Features
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Mains current lead/lag status indication for
reactive energy measurement.
Low power battery operating mode for meter
reading when Mains voltage is not present.
AS8267: 20 x 4 segment LCDD
9 x multi-purpose I/O (MPIO)
AS8268: 24 x 4 segment LCDD
12 x multi-purpose I/O (MPIO)
Precision single-phase, one or two current input
energy measurement front-end including Sigma-
Delta modulators for A/D-conversion and digital
signal processor (DSP).
Low current consumption of 5mA, depending on
MCU activity.
Digital phase correction and selectable gain on
both current channels for use with two current
transformers (CT) or one CT and one shunt.
Power-supply monitor (PSM) for power-on reset
and reset when the supply voltage falls below a
defined threshold.
Customer programmable 8-bit 8051 compatible
microcontroller (MCU).
Programmable MCU clock for optional low
power operating conditions.
Highly reliable 32kBytes of non-volatile Flash
memory is provided on-chip for storage of both
program and data.
Program and data security is provided by
optional password and attack counter
protection.
2 x Universal Asynchronous Receiver /
Transmitters (UART) for external
communications such as programme download
and debugging.
Programmable watchdog timer (WDT) and
external system reset pin.
Real-time clock/calendar (RTC) with on-chip
digital calibration and separate battery supply
pin.
On-chip temperature sensor for optional
temperature compensation.
On-chip voltage reference (VREF) with small
temperature coefficient (15ppm/K typ.).
Low power 3.0 – 4.0MHz crystal oscillator.
SPI compatible interface for optional external
non-volatile EEPROM memory selectable up to
32kBytes.
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2. General Description
The AS8267 / AS8268 are highly integrated CMOS
single-phase energy metering devices for fully
electronic LCD meter systems. The AS8267 /
AS8268 have been designed to ensure a meters
full compliance with the international Standards
IEC62052 and ANSI.
The AS8267 / AS8268 ICs include all the functions
required for conventional 1 current or 2-current
anti-tamper meters. The functions include precision
energy measurement, an 8-bit microcontroller unit
(MCU) with 32kBytes of Flash memory, an on-chip
Liquid Crystal Display driver (LCDD),
programmable multi-purpose Inputs/Outputs
(MPIO), a real time clock/calendar (RTC) for
complex tariff functions such as time-of-use or
maximum demand billing and a Serial Peripheral
Interface (SPI) for reading data from and writing
data to an optional external non-volatile memory
(EEPROM).
The AS8267 / AS8268 ICs have a dedicated energy
measurement front-end, which includes an analog
front-end and programmable Digital Signal
Processor (DSP) from which active energy, mains
voltage and mains current are provided. Reactive
and apparent energy can also be calculated.
The on-chip 8-bit 8051 compatible microcontroller
is freely programmable and provides user access to
the various functional blocks. The dedicated
Universal Asynchronous Receiver / Transmitter
(UART1) in the System Control block allows access
to various system functions and blocks. A second
UART (UART2) is also provided, which may for
example be used for debugging. The on-chip
memory includes 32kByte of highly reliable non-
volatile Flash program (and data) memory and
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Revision 1.0, 19-Jun-07
Page 1 of 136
Data Sheet AS8267 / AS8268
1kByte volatile data memory. The meter system
designer also has the option of an additional
external EEPROM memory, which is selectable in
size from 1kByte to 32kByte (in binary steps).
Program and data stored in the on-chip non-volatile
Flash memory can be secured by password
protection, in addition to an attack counter which
‘locks’ access after 5 unauthorised attacks.
An on-chip programmable watchdog timer (WDT) is
available to automatically initiate a system reset if
a regular ‘hold-off’ signal is not detected.
The system timing and real time clock (RTC) has a
dedicated external battery supply pin (VDD_BAT),
enabling the oscillator and RTC to continue
operation during ‘power-down’. The RTC may be
digitally calibrated for oscillator frequency
accuracy.
The on-chip temperature sensor provides the meter
designer the option of temperature compensation
for any of the measured parameters or functional
blocks provided, over the full operating temperature
range of the device.
The LCD Driver (LCDD) block enables the display
of information provided by the microcontroller,
directly to the LCD. Two dedicated data register
banks are provided to simplify programming,
particularly in the case where scrolled display data
is required.
The programmable multi-purpose I/O pins (MPIO)
may be independently configured as inputs or
outputs. All the I/O pins are programmable for data
direction, pull-up/pull-down resistors and drive
strength (4mA/8mA). Typical functions may include
LED energy consumption pulse output, energy
direction and fault condition indication depending
on current 1 or current 2 being active for the
energy calculation, push button for display
scrolling, mains isolation relay control for
prepayment meters, optical interface etc.
An on-chip analog ground buffer (ABUF) and
voltage reference (VREF) ensures that no external
circuitry is required. A power-supply monitor (PSM)
provides a reset, when VDD falls below a safe
operating threshold.
A reset pin (RES_N) is available for external
system reset.
The AS8267 / AS8268 ICs are available in LQFP64
plastic package.
Revision 1.0, 19-Jun-07
Page 2 of 136
Data Sheet AS8267 / AS8268
3. Typical Application Circuit
3.3V
3.3V
+
+
LCD
3.3V
XIN XOUT
32
33
Low
Power
Oscillator
VDDA
7
Low
Power
Divider
13
VDDD
22
LBP0
LBP1
LBP2
LBP3
kWh
Vrms
Irms
37 38 39 40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
9
LSD0
LSD1
LSD2
LSD3
LSD4
LSD5
LSD6
LSD7
LSD8
LSD9
LSD10
LSD11
LSD12
LSD13
LSD14
LSD15
LSD16
LSD17
LSD18
LSD19
LSD20
LSD21
LSD22
LSD23
IO0
IO1
IO2
IO3
IO4
IO5
IO6
IO7
IO8
IO9
IO10
IO11
LED
DIRO
FAULT
VDD_BAT 31
RTC
System Timing & RTC
LOAD
I1P
3
Analog Front End
LCD
Driver
SDM
I1N
I2N
4
6
SDM
I2P
VP
5
1
DSP
MCU
SDM
VN
RES_N
2
34
I/Os
Examples
only
10
11
WDT
Temperature
Sensor
FLASH
Memory
Multi-
purpose
I/Os
12
15
16
17
18
19
26
27
28
Push-Button
Reference pulses
for calibration
AS8268 only
System
Control
UART1
23 S_N
20 MISO
24 MOSI
25 SC
SPI
29
TXD
VI
VO
30
RXD
3.3V
8
VSSA
14
VSSD
21
VSSD
EEPROM
S 1
Q
2
3.3V W 3
VSS
4
8 VCC 3.3V
HOLD 3.3V
7
6 C
5 D
+
GND
N
L
Figure 1:
Typical application circuit of the AS8267 / AS8268
Revision 1.0, 19-Jun-07
AS8268 only
Page 3 of 136
Data Sheet AS8267 / AS8268
4. Pin Out
LSD19
LSD18
LSD17
LSD16
LSD15
LSD14
LSD13
LSD12
LSD11
LSD10
LSD23
LSD22
LSD21
LSD20
LSD19
LSD18
LSD17
LSD16
LSD15
LSD14
LSD13
LSD12
LSD11
LSD10
51
LSD9
LSD8
LSD9
50
64
63
62
61
60
59
58
57
56
55
54
53
52
64
63
62
61
60
59
58
57
56
55
54
53
52
51
50
49
VP
VN
I1P
I1N
I2P
I2N
VDDA
VSSA
IO0
IO1
IO2
IO3
VDDD
VSSD
IO4
IO5
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
48
47
46
45
44
43
42
LSD7
LSD6
LSD5
LSD4
LSD3
LSD2
LSD1
LSD0
LBP3
LBP2
LBP1
LBP0
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RES_N
XOUT
VP
VN
I1P
I1N
I2P
I2N
VDDA
VSSA
IO0
IO1
IO2
IO3
VDDD
VSSD
IO4
IO5
49
LSD8
48
47
46
45
44
43
42
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1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
LSD7
LSD6
LSD5
LSD4
LSD3
LSD2
LSD1
LSD0
LBP3
LBP2
LBP1
LBP0
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RES_N
XOUT
AS8267
LQFP64
41
40
39
38
37
36
35
34
33
AS8268
LQFP64
41
40
39
38
37
36
35
34
33
VDD_BAT
IO6
IO7
IO8
IO9
IO10
MISO
MOSI
IO11
S_N
VSSD
TXD
VDDD
5. Pin Description
Pin
No.
1
2
3
Pin Name Pin Name
AS8267
AS8268
VP
VN
I1P
VP
VN
I1P
Type
AI
AI
AI
Description
Positive input for the voltage channel. VP is a differential input with VN. The
typical differential voltage is
±100mV
peak.
Negative input for the voltage channel. VN is a differential input with VP.
Positive input for the first current channel. I1P is a differential input with I1N.
The input gain is programmable depending on the desired current sensor. The
typical differential voltage is
±150mV
peak (Gain = 4).
Negative input for the first current channel. I1N is a differential input with I1P.
The input gain is programmable depending on the desired current sensor. The
typical differential voltage is
±150mV
peak (Gain = 4).
Positive input for the second current channel. I2P is a differential input with
I2N. The input gain is programmable depending on the desired current sensor.
The typical differential voltage is
±150mV
peak
(Gain = 4).
Negative input for the second current channel. I2N is a differential input with
I2P. The input gain is programmable depending on the desired current sensor.
The typical differential voltage is
±150mV
peak
(Gain = 4).
Positive supply voltage for the analog circuitry. The required supply voltage is
3.3V
±10%.
Ground reference for the analog circuitry.
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
4
I1N
I1N
AI
5
I2P
I2P
AI
6
I2N
I2N
AI
7
8
9
10
VDDA
VSSA
IO0
IO1
VDDA
VSSA
IO0
IO1
S
S
DIO
DIO
Revision 1.0, 19-Jun-07
VDD_BAT
VDDD
VSSD
MISO
MOSI
RXD
RXD
S_N
TXD
XIN
XIN
IO6
IO7
IO8
SC
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SC
Page 4 of 136
Data Sheet AS8267 / AS8268
Pin
No.
11
12
13
14
15
16
17
18
19
20
Pin Name Pin Name
AS8267
AS8268
IO2
IO3
VDDD
VSSD
IO4
IO5
IO6
IO7
IO8
MISO
IO2
IO3
VDDD
VSSD
IO4
IO5
IO6
IO7
IO8
MISO
Type
DIO
DIO
S
S
DIO
DIO
DIO
DIO
DIO
Description
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
Positive supply voltage to the digital circuitry and is internally connected to pin
22. The required supply voltage is 3.3V
±10%.
Ground reference for the digital circuitry.
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
DIOPD Serial peripheral interface (SPI):
Serial Data input in Master mode
Serial Data output in Slave mode
S
S
Ground reference for the digital circuitry.
Positive digital supply. VDDD provides the positive supply voltage to the digital
circuitry and is internally connected to pin 13. The required supply voltage is
3.3V
±10%.
21
22
VSSD
VDDD
VSSD
VDDD
23
24
S_N
MOSI
S_N
MOSI
DIOPU Serial peripheral interface (SPI): Chip select
DIOPD Serial peripheral interface (SPI):
Serial Data output in Master mode
Serial Data input in Slave mode
DIOPU Serial peripheral interface (SPI): Serial clock
DIO
DIO
DIO
DO
DIPU
S
AI
AO
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
Programmable multi-purpose input/output, with selectable pull-up or pull-down
resistors and selectable drive strength.
Universal Asynchronous Receiver/Transmitter (UART1) serial transmit data
output.
Universal Asynchronous Receiver/Transmitter (UART1) serial receive data
input.
Battery backup supply voltage input for the real time clock (RTC).
A 3.0 to 4.0MHz crystal may be connected across XIN and XOUT.
Alternatively, an external clock signal may be applied to XIN.
See XIN above, for the connection of a crystal. When an external clock is
applied to XIN, XOUT is not connected.
System reset active low.
Not connected
25
26
27
28
29
30
31
32
33
34
35
SC
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TXD
RXD
SC
IO9
IO10
IO11
TXD
RXD
VDD_BAT VDD_BAT
XIN
XOUT
RES_N
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XIN
XOUT
RES_N
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Revision 1.0, 19-Jun-07
Page 5 of 136
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