19-5361; Rev 7/11
71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
JULY 2011
FEATURES
The 71M6515H is a high-accuracy analog front-end
(AFE) IC that provides measurements for 3-quadrant
3-phase metering. The combination of a 21-bit
sigma-delta A/D converter with a six-input analog
front-end, a thermally compensated high-precision
reference, and a compute engine results in high
accuracy and wide dynamic range. Our Single
Converter Technology® reduces cross talk and cost.
This IC also provides RTC and battery backup for
time-of-use (TOU) metering.
High Accuracy
< 0.1% Wh accuracy over 2000:1 range
Exceeds IEC 62053/ANSIC 12.20 specifications
Up to 10ppm/C precision ultra-stable voltage
reference
Single Converter Technology reduces cross talk
and power consumption
Six sensor inputs—referenced to V3P3
Compatible with CTs, resistive shunts and
Rogowski Coil sensors
Digital temperature compensation
Sag detection
Measures Wh, VARh, VAh, Vrms, Irms, V-to-V
phase and load angle on each phase
Four-quadrant metering.
Four low-jitter pulse outputs from selectable
measurements
Four pulse count registers
Selectable default status for pulse pins
Same calibration data for 46Hz to 64Hz line
frequency
Broad CT phase compensation (±7deg)
VOLTAGE
CURRENT
GENERAL DESCRIPTION
Battery
UART, IRQZ
RTC
COMPUTE
ENGINE
HOST
PROCESSOR
RAM
SSI
VOLTAGE
REFERENCE
CONTROL
DIO
TERIDIAN 71M6515H
Figure 1: Meter Block Diagram
As shown in the block diagram (Figure 1), the host
processor communicates with the 71M6515H
through a UART interface using the programmable
IRQZ interrupt. The 71M6515H calculates and accumulates meter measurements for each accumulation
interval. A high-speed synchronous serial port (SSI)
is provided to facilitate high-end metering. Integrated
rectifying functions on the battery-backup circuit
enable minimal external component usage and
minimum back-up current. Also, eight multipurpose
pins are provided for control of peripherals.
Single Converter Technology is a registered trademark of
Maxim Integrated Products, Inc.
Page: 1 of 60
Battery Backup
Powers real-time clock during power supply
outage
Compatible with Li-ion, NiCd, or super capacitor
Battery backup current 2µA typical at 25°C
External Data Interface
UART control interface, two selectable data rates
8 general-purpose I/O pins with alarm capability
5 or 10MHz selectable high-speed synchronous
serial output for DSP interface
IRQ output signal for alarms and end of
measurement intervals
Alarms on voltage sag, overvoltage, overcurrent
Low System Cost
Power consumption 30mW at 3.3V typical
Real-time clock with temperature compensation
Built-in power-fault detection
Single 32kHz crystal time base
Single-supply operation (3.3V)
64-lead LQFP package
© 20052011 Teridian Semiconductor Corporation
1.6
VREF
PULSEW
PULSER
V3P3A
GNDA
GNDA
∆Σ ADC
CONVERTER
IA
VA
IB
VB
IC
VC
GNDD
MUX
VOLT
REG
V3P3A
+
V3P3D
21
GNDD
VREF
VX
TEMP
VREF
GNDD
V2P5
MUXSYNC
2.5V to logic
VBIAS
(1.5V)
CALCULATIONS
SSI INTERFACE
SSCLK
SSDATA
OUTPUT VALUES:
Whr (A, B, C)
VARhr (A, B, C)
VAhr (A, B, C)
Vrms (A, B, C)
Irms (A, B, C)
Iphase (A, B, C)
Frequency (Selected Phase)
Temperature
SFR
SRDY
SYSTEM CLOCKS
CK_GEN
CKTEST
ALARMS:
Voltage Sag (A, B, C)
Zero Cross (Selected Phase)
Over-Voltage (All)
Over-Current (All)
D0-D7 State Change
BATTERY BACKUP
OSC
(32KHz)
XIN
XOUT
RTC
VBAT
PULSE4
PULSE3
PULSE_INIT
BAUDRATE
DATA
RAM
CONTROL
MISC
TX
IRQZ
UART
RX
I/O CONTROL
D0
D4
D1
D5
D6
D2
Change of State
(D0...D7)
D3
D7
TEST
VFLT
FAULT DETECT
VBIAS
(1.5V)
GNDD
V3P3
TMUXOUT
VX
RESERVED
64 PINS -- 64 TQFP
RESETZ
March 3, 2008
Figure 2: IC Functional Block Diagram
ELECTRICAL SPECIFICATIONS
Page: 2 of 60
© 2005−2011 Teridian Semiconductor Corporation
1.6
71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
JULY 2011
ABSOLUTE MAXIMUM RATINGS
Supplies and Ground Pins:
V3P3D, V3P3A
|V3P3D – V3P3A|
VBAT
GNDD
Analog Output Pins:
−0.5V to 4.6V
0V to 0.5V
-0.5V to 4.6V
-0.5V to +0.5V
-1mA to 1mA,
-0.5V to V3P3A+0.5V
-1mA to 1mA,
-0.5 to 3.0V
VREF
V2P5
Analog Input Pins:
IA, VA, IB, VB, IC, VC
VFLT, VX
XIN, XOUT
Digital Input Pins:
RX
D0…D7
All other pins
-0.5V to V3P3A+1.0V
-0.5V to V3P3A+0.5V
-0.5V to 3.0V
-0.5V to 3.6V
-0.5V to 6V
-0.5V to V3P3D+0.5V
Operating junction temperature (peak, 100ms)
Operating junction temperature (continuous)
Storage temperature
Solder temperature – 10 second duration
ESD Stress
Pins IA, VA, IB, VB, IC, VC, RX, TX
All other pins
140 °C
125 °C
−45 °C to 165 °C
250 °C
6kV
2kV
Stresses beyond Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only and functional
operation at these or any other conditions beyond those indicated under “recommended operating conditions” is not implied. Exposure to
absolute-maximum-rated conditions for extended periods may affect device reliability. All voltages are with respect to GNDA.
RECOMMENDED OPERATING CONDITIONS
PARAMETER
CONDITION
MIN
3.3V Supply Voltage (V3P3A, V3P3D)+
Normal Operation
Battery Backup
No Battery
Battery Backup
3.0
3.3
3.6
V
0
3.8
V
Externally Connect to V3P3D
2.0
3.8
V
-40
85
ºC
VBAT
Operating Temperature
+
TYP
MAX
UNIT
V3P3A and V3P3D should be shorted together on the circuit board. GNDD and GNDA should also be shorted on the circuit board.
Page: 3 of 60
© 2005−2011 Teridian Semiconductor Corporation
1.6
71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
JULY 2011
LOGIC LEVELS
PARAMETER
CONDITION
Digital high-level input voltage, VIH
Digital low-level input voltage, VIL
ILOAD = 1mA
ILOAD = 15mA
ILOAD = 1mA
ILOAD = 15mA
VIN=0V
Input pull-up current, IIL
RESETZ
E_RXTX, E_ISYNC/BRKRQ
E_RST
Other digital inputs
Input pull down current, IIH
TEST
Other digital inputs
1
TYP
2
−0.3
V3P3D
–0.4
V3P3D0.61
0
Digital high-level output voltage VOH
Digital low-level output voltage VOL
MIN
MAX
UNIT
V3P3D
0.8
V
V
V3P3D
V
V
0.4
0.81
V
V
10
10
10
-1
100
100
100
+1
µA
µA
µA
µA
10
-1
100
+1
µA
µA
VIN=V3P3D
Guaranteed by design; not production tested.
SUPPLY CURRENT
PARAMETER
V3P3A + V3P3D
V3P3A current
V3P3D current
VBAT current
VBAT current,
VBAT=3.6V
1
CONDITION
MIN
Normal Operation,
V3P3A=V3P3D=3.3V
VBAT=3.6V
TYP
MAX
UNIT
8.8
3.7
5.1
2
11.5
4.7
6.8
300
4
mA
mA
mA
nA
µA
4
12
-300
Battery backup,
≤25°C
V3P3A=V3P3D=0V
85°C
fOSC = 32kHz
1
µA
Guaranteed by design; not production tested.
VREF
Page: 4 of 60
© 2005−2011 Teridian Semiconductor Corporation
1.6
71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
JULY 2011
PARAMETER
CONDITION
MIN
MAX
VREF output voltage, VNOM(25)
VREF output impedance
VNOM definition 2
Ta = 25ºC
1.193
1.195
1.197
ILOAD = 10µA, -10µA
2.5
VNOM(T) = VREF(22) + (T-22)TC1 + (T-22)2TC2
VREF(T) deviation from VNOM(T)
Ta = -40ºC to +85ºC, for
71M6515H-IGT/F
VREF (T ) − VNOM (T )
10
VNOM
max(| T − 22 |,40)
6
Ta = -40ºC to +85ºC, for
71M6515H-IGTW/F
1
+10
1
+40
-10
-40
±25
VREF aging
1
TYP
UNIT
V
kΩ
V
1
PPM/ºC
1
PPM/ºC
PPM/year
Guaranteed by design; not production tested.
2
This relationship describes the nominal behavior of VREF at different temperatures. The values of TC1 and TC2 are device
specific in general and are programmed into the device at manufacturing.
Page: 5 of 60
© 2005−2011 Teridian Semiconductor Corporation
1.6
71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
JULY 2011
2.5V VOLTAGE REGULATOR
PARAMETER
CONDITION
Reduce V3P3 until V2P5
drops 200mV
RESETZ=1, ILOAD=0
Voltage Overhead V3P3D-V2P5
PSRR
MIN
ΔV2P5/ΔV3P3D
TYP
-3
MAX
UNIT
440
mV
+3
mV/V
RTC
PARAMETER
CONDITION
Range for date
MIN
TYP
MAX
UNIT
2000
--
2255
year
MIN
TYP
MAX
UNIT
11
µs
µs
RESETZ
PARAMETER
CONDITION
Reset pulse width
Reset pulse fall time
1
5
Guaranteed by design; not production tested.
CRYSTAL OSCILLATOR
PARAMETER
Maximum Output Power to Crystal4
Xin to Xout Capacitance
Capacitance to DGND
Xin
Xout
Watchdog RTC_OK threshold
CONDITION
MIN
TYP
MAX
1
3
5
5
UNIT
µW
pF
25
pF
pF
kHz
MAX
UNIT
TEMPERATURE SENSOR
PARAMETER
CONDITION
Nominal Sensitivity (Sn)
Nominal Offset (Nn)
4
MIN
TA=25ºC, TA=85ºC
Nominal relationship:
N(T)= Sn*T+Nn
4
TYP
-900
LSB/ºC
40000
0
LSB
Temperature Error, relative to 25ºC error
ERR = (T − 25) −
1
( N (T ) − N (25))
Sn
TA = -40ºC to +85ºC
-31
+31
ºC
Guaranteed by design; not production tested.
Page: 6 of 60
© 2005−2011 Teridian Semiconductor Corporation
1.6
71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
JULY 2011
PULSE GENERATOR TIMING SPECIFICATIONS
PARAMETER
CONDITION
MIN
TYP
MAX
UNIT
7.56
kHz
0.15
kHz
0.15
kHz
CONDITION
VALUE
UNIT
Air velocity 0 m/s. Part soldered to PCB.
63.7
°C/W
APULSE=231-1,
WRATE=215-1
PULSE3=231-1,
WRATE=215-1
PULSEW, PULSER maximum rate
PULSE3, PULSE4 maximum rate
Pulse count frequency
all pulse outputs
THERMAL CHARACTERISTICS
PARAMETER
Thermal resistance, junction to ambient (RθJA )
UART HOST INTERFACE
PARAMETER
CONDITION
Baud Rate
Character set
Data Format
Byte-to-byte delay (6515H times out after
maximum delay)
Byte-to-byte delay
Response time to read command
Response time to read command when
71M6515H is post-processing data
Host sending data to
6515H
6515H sending data to
host
6515H has data ready
Data not ready
CE_ONLY = 1
CE_ONLY = 0 and
VAH_SELECT = 0
CE_ONLY = 0 and
VAH_SELECT = 1
MIN
TYP
MAX
UNIT
19.2
binary
8N1
38.4
kBaud
10
20
ms
0
0.1
ms
0.5
2
ms
40
ms
80
ms
350
ms
MAX
UNIT
-250
250
mV
peak
-101
+101
µV/V
90
dB
dB
kΩ
ADC CONVERTER, V3P3 REFERENCED
PARAMETER
CONDITION
Usable Input Range (Vin-V3P3A)
Voltage to Current cross talk:
Page: 7 of 60
TYP
Vin = 200mV peak, 65Hz,
on VA, VB, or VC
10 6 *Vcrosstalk
cos(∠Vin − ∠Vcrosstalk ) Vcrosstalk = largest
Vin
measurement on IA, IB, or
THD (First 10 harmonics)
250mV-pk
20mV-pk
Input Impedance
MIN
IC
Vin=65Hz,
64kpts FFT, BlackmanHarris window
Vin=65Hz
-75
-90
40
© 2005−2011 Teridian Semiconductor Corporation
1.6
71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
JULY 2011
Temperature Coefficient of Input
Impedance
LSB size
Digital Full Scale
ADC Gain Error vs.
%Power Supply Variation
Vin=65Hz
Ω/°C
355
+884736
nV/LSB
LSB
Vin=200mV pk, 65Hz
V3P3A=3.0V, 3.6V
10 6 ∆Nout PK 357nV / VIN
100 ∆V 3P3 A / 3.3
Input Offset (Vin-V3P3A)
1
1.7
-10
50
PPM/
%
+10
mV
Guaranteed by design; not production tested.
RECOMMENDED EXTERNAL COMPONENTS
NAME
C1
C2
FROM
V3P3A
V3P3D
TO
AGND
DGND
XTAL
XIN
XOUT
CXS
CXL
C2P5
XIN
XOUT
V2P5
AGND
AGND
DGND
FUNCTION
Bypass capacitor for 3.3V supply
Bypass capacitor for 3.3V supply
32.768kHz crystal – electrically similar to
ECS .327-12.5-17X or Vishay XT26T, load
capacitance 12.5pF
Load capacitor for crystal (depends on crystal
specs and board parasitics).
Bypass capacitor for V2P5
VALUE
≥0.1±20%
≥0.1±20%
UNIT
µF
µF
32.768
kHz
27±10%
27±10%
≥0.1±20%
pF
pF
µF
FOOTNOTES:
1 This spec is guaranteed, has been verified in production samples, but is not measured in production.
2 This spec is guaranteed, has been verified in production samples, but is measured in production only at DC.
3 This spec is measured in production at the limits of the specified operating temperature.
4 This spec defines a nominal relationship rather than a measured parameter. Correct circuit operation is verified with other specs that use
this nominal relationship as a reference
Page: 8 of 60
© 2005−2011 Teridian Semiconductor Corporation
1.6
71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
JULY 2011
VB
V3P3A
GNDA
50
49
53
VC
VA
54
51
IC
55
52
IA
IB
56
VX
VREF
57
VFLT
59
58
XIN
GNDA
61
60
XOUT
GNDD
62
RESERVED
64
63
PIN CONFIGURATION AND PIN FUNCTION
GNDD
1
48
GNDD
RESERVED
TMUXOUT
/RTM
TX
2
47
RESETZ
3
46
V2P5
45
VBAT
44
RX
SSCLK
5
CKTEST
6
V3P3D
7
SSDATA
SFR
TERIDIAN
4
71M6515H-IGT
Or
71M6515H-IGTW
8
9
43
RESERVED
42
D0
41
IRQZ
40
PULSE_INIT
39
D6
10
RESERVED
11
38
D5
RESERVED
12
37
D4
RESERVED
13
36
PULSER
PULSE3
14
35
PULSEW
PULSE4
15
34
UARTCSZ
33
D7
19
20
21
22
23
24
25
26
27
28
29
30
31
RESERVED
RESERVED
RESERVED
D1
D2
D3
SRDY
MUX_SYNC
RESERVED
GNDD
RESERVED
RESERVED
RESERVED
RESERVED
RESERVED
18
17
16
RESERVED
BAUD_RATE
32
RESERVED
Pins marked RESERVED should be left unconnected during normal use.
Page: 9 of 60
© 2005−2011 Teridian Semiconductor Corporation
1.6
71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
JULY 2011
Analog Pin Description
IA,
IB,
IC
VA,
VB,
VC
VFLT
VX
VREF
Pin
No.
56
55
54
53
52
51
59
58
57
XIN,
XOUT
61
63
Name
Type
Circuit
I
6
I
6
I
I
I/O
7
6
9
I
8
Description
Line Current Sense Inputs: Voltage inputs to the internal A/D converter. Typically,
they are connected to the output of a current transformer. The input is referenced
to V3P3A. Unused pins must be tied to V3P3A.
Line Voltage Sense Inputs: Voltage inputs to the internal A/D converter. Typically,
they are connected to the output of a resistor divider. The input is referenced to
V3P3A. Unused pins must be tied to V3P3A.
Power Fault Input. This pin must be tied to V3P3A.
Auxiliary input (not used). This pin should be tied to VREF.
Voltage Reference for the ADC.
Crystal Inputs: A 32768Hz crystal should be connected across these pins.
Typically, a 15pF capacitor is also connected from each pin to GNDA. See the
datasheet of the crystal manufacturer for details.
Pin types: P = Power, O = Output, I = Input, I/O = Input/Output
The circuit number denotes the equivalent circuit, as specified under “I/O Equivalent Circuits”.
Digital Pin Description
Unless otherwise indicated, all inputs and outputs are standard CMOS. Inputs do NOT have internal pull-ups or pull-downs.
Pin
No.
Type
Circuit
CKTEST
6
I/O
4
D0
D1
D2
D3
D4
D5
D6
D7
PULSE4
PULSE3
42
21
22
23
37
38
39
33
15
14
PULSE_INIT
Name
I/O
3, 4
O
O
4
4
40
I
3
BAUD_RATE
16
I
3
IRQZ
41
O
4
MUXSYNC
25
O
4
RESETZ
47
I
1
Page: 10 of 60
Description
Clock PLL output. Can be enabled and disabled by CKOUT_DSB (see
Status Mask).
Input/output pins 0 through 7. These pins must be terminated to
V3P3D or ground if configured as input pins.
D0 through D7 are high impedance after reset or power-up and are
configured as outputs and driven low 140ms after RESETZ goes
high.
The fourth pulse generator output
The third pulse generator output
The pulse output initial power-up voltage (0: 0V, 1: 3.3V), default is 1.
This pin must be terminated to V3P3D or ground.
The UART baud rate (1: 38.4kbd, 0: 19.2kbd). This pin must be
terminated to V3P3D or ground.
Interrupt output, low active. A falling edge indicates the end of a
measurement frame, as well as alarms. Rises when status word is
read.
Internal signal. MUXSYNC falls at the beginning of each conversion
cycle (multiplexer frame).
Chip reset: Input pin with internal pull-up resistor, used to reset the chip
into a known state. For normal operation, this pin is set to 1. To reset
the chip, this pin is driven to 0 for 5 microseconds. No external reset
circuitry is necessary for power-up reset.
© 2005−2011 Teridian Semiconductor Corporation
1.6
71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
JULY 2011
Name
Pin
No.
Type
Circuit
UARTCSZ
34
I
3
SRDY
SFR
SSCLK
SSDATA
24
9
5
8
I
O
O
O
3
4
4
4
RX
44
I
3
TX
TMUXOUT
PULSER
PULSEW
4
3
36
35
O
O
O
O
4
4
4
4
Description
Enables the UART when 0. The UART is disabled when this pin is set
to 1. A positive pulse on this pin will reset the UART. This pin must be
terminated to ground.
High-Speed Synchronous Interface (SSI).
The SRDY input should be tied to ground.
SSI frame pulse output, one SSCLK wide.
SSI clock output (5MHz or 10MHz selectable).
SSI data output, changes on the rising edge of SSCLK.
UART serial Interface receiver input. The voltage at this pin must not
exceed 3.6V. This pin must be terminated to V3P3D or ground.
UART serial Interface transmitter output.
Digital output test multiplexer. Controlled by TMUX[2:0].
Selectable pulse output (default: VARh pulse).
Selectable pulse output (default: Wh pulse).
Power/Ground Pin Description
Name
Pin No.
Type
GNDA
P
Analog ground: This pin should be connected directly to the ground plane.
P
Digital ground: These pins must be connected directly to the ground plane.
V3P3A
49,60
1,27,
48,62
50
P
Analog power: A 3.3V analog power supply should be connected to this pin.
V3P3D
7
P
Digital power supply: A 3.3V digital power supply should be connected to this pin.
VBAT
45
P
V2P5
46
O
GNDD
Description
Battery backup power supply. A battery or super-capacitor is to be connected between
VBAT and GNDD. If no battery is used, connect VBAT to V3P3D.
Output of the 2.5V regulator. A 0.1µF capacitor should be connected from this pin to GND.
Pin types: P = Power, O = Output, I = Input, I/O = Input/Output
The circuit number denotes the equivalent circuit, as specified under “I/O Equivalent Circuits”.
Reserved Pins
Pins labeled RESERVED are not to be connected.
Name
RESERVED
Page: 11 of 60
Pin No.
2,10,11,12,
13,17,18,19,
20,26,28,29,
30,31,32,43,
64
Description
DO NOT CONNECT THESE PINS!
© 2005−2011 Teridian Semiconductor Corporation
1.6
71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
JULY 2011
I/O Equivalent Circuits
V3P3D
V3P3A
V3P3D
V3P3D
110K
Digital
Input
Pin
CMOS
Input
Analog
Input
Pin
To
MUX
from
internal
reference
V2P5
Pin
GNDD
GNDA
Digital Input Equivalent Circuit
Type 1:
Standard Digital Input or
pin configured as DIO Input
with Internal Pull-Up
GNDD
Analog Input Equivalent Circuit
Type 6:
ADC Input
V2P5 Equivalent Circuit
Type 10:
V2P5
V3P3D
V3P3A
Digital
Input
Pin
CMOS
Input
110K
GNDD
Comparator
Input
Pin
To
Comparator
GNDD
GNDD
GNDA
Comparator Input Equivalent
Circuit Type 7:
Comparator Input
Digital Input
Type 2:
Pin configured as DIO Input
with Internal Pull-Down
V3P3D
Digital
Input
Pin
Power
Down
Circuits
VBAT
Pin
VBAT Equivalent Circuit
Type 12:
VBAT Power
V3P3D
CMOS
Input
Oscillator
Pin
GNDD
To
Oscillator
GNDD
Digital Input Type 3:
Standard Digital Input or
pin configured as DIO Input
Oscillator Equivalent Circuit
Type 8:
Oscillator I/O
V3P3D
V3P3D
V3P3A
Digital
Output
Pin
CMOS
Output
GNDD
GNDD
Digital Output Equivalent Circuit
Type 4:
Standard Digital Output or
pin configured as DIO Output
Page: 12 of 60
from
internal
reference
VREF
Pin
GNDA
VREF Equivalent Circuit
Type 9:
VREF
© 2005−2011 Teridian Semiconductor Corporation
1.6
71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
JULY 2011
%Error
TYPICAL PERFORMANCE CHARACTERISTICS
0.2
0.15
0.1
0.05
0
-0.05
-0.1
-0.15
-0.2
0 Deg
60 Deg
-60 Deg
180 Deg
1
3
0.3
200
10
0.1
1
25 30
10
100
100
A
1000
Figure 3: Wh Accuracy, 0.3A - 200A/240V
0.2
90 Deg
0.15
150 Deg
0.1
% Error
0.05
3
0
270 Deg
10
25
1
30
0.3
100
-0.05
200
-0.1
-0.15
-0.2
0.1
1
10
A
100
1000
Figure 4: VARh Accuracy for 0.3A to 200A/240V Performance
Page: 13 of 60
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Energy Meter IC
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2
1
0
Error [%]
-1
-2
-3
50Hz Harmonic Data
60Hz Harmonic Data
-4
-5
-6
-7
-8
1
3
5
7
9
11
13
15
17
19
21
23
25
Harmonic
Measured at current distortion amplitude of 40% and voltage distortion amplitude of 10%.
Figure 5: Meter Accuracy over Harmonics at 240V, 30A
Error [%]
Performance for Apparent Energy (VAh)
0.2
0.15
0.1
0.05
0
-0.05
-0.1
-0.15
-0.2
0.1
1
10
100
1000
Current [A]
Figure 6: Typical VAh Accuracy for VAh Using Vector Method
Page: 14 of 60
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71M6515H
Energy Meter IC
A Maxim Integrated Products Brand
DATA SHEET
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FUNCTIONAL DESCRIPTION
THEORY OF OPERATION
The 71M6515H integrates the primary functional blocks required to implement a solid-state electricity meter front end. Included
on-chip are an analog front end (AFE), a digital computation engine (CE), a voltage reference, a real time clock, and I/O pins.
Various current sensor technologies are supported including Current Transformers (CT), Resistive Shunts, and Rogowski
(di/dt) Coils.
In a typical application, the 71M6515H sequentially digitizes the voltage inputs on pins IA, VA, IB, VB, IC, VC and performs
calculations to measure active energy (Wh), reactive energy (VARh), and apparent energy (VAh). In addition to these
measurement functions, the real time clock function allows the device to record time of use (TOU) metering information for
multi-rate applications.
The 71M6515H contains a temperature-trimmed ultra-precise voltage reference, and the on-chip digital temperature compensation mechanism includes a temperature sensor and associated controls for correction of unwanted temperature effects on
measurement. RTC accuracy can be greatly improved by supplying correction coefficients derived from crystal
characterization. The combination of both features enables designers to produce electricity meters with exceptional accuracy
over the industrial temperature range.
Meter Equations
The 71M6515H implements the equations in Table 1. Register EQU specifies the equation to be used. In one sample time,
each of the six inputs is converted and the selected equation updated. In a typical application, IA, IB, IC are connected to
current transformers that sense the current on each phase of the line voltage. VA, VB, and VC are typically connected to
voltage sensors (resistor dividers) with respect to NEUTRAL. NEUTRAL is to be connected to V3P3A, the analog supply
voltage. NEUTRAL is the zero reference for all analog measurements.
EQU
Watt & VAR Formula
Application
Channels used from MUX
sequence
Mux State:
0
1
2
3
4
5
0
VA IA
1 element, 2W 1ø
IA
VA
-
-
-
-
1*
VA(IA-IB)/2
1 element, 3W 1ø
IA
VA
IB
-
-
-
2
VA IA + VB IB
2 element, 3W 3 øDelta
IA
VA
IB
VB
-
-
3*
VA (IA - IB)/2 + VC IC
2 element, 4W 3ø Delta
IA
VA
IB
-
IC
VC
4*
VA(IA-IB)/2 + VB(IC-IB)/2)
2 element, 4W 3ø Wye
IA
VA
IB
VB
IC
-
5
VA IA + VB IB + VC IC
3 element, 4W 3ø Wye
IA
VA
IB
VB
IC
VC
Note: Equations 1*, 3*, 4* available only when IMAGE = 00 (CT mode).
Table 1: Meter Equations
Table 2 shows how the elements of the meter are mapped for the six possible equations.
Page: 15 of 60
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EQU
Element Output Mapping
Watt & VAR Formula
(WSUM/VARSUM)
W0SUM/
VAR0SUM
W1SUM/
VAR1SUM
W2SUM/
VAR2SUM
I0SQ
SUM
I1SQ
SUM
I2SQ
SUM
VA*IA
-
-
IA
-
-
VA*(IA-IB)/2
VA*IB
-
IA-IB
IB
-
0
VA IA (1 element, 2W 1φ)
1
VA*(IA-IB)/2
(1 element, 3W 1φ)
2
VA*IA + VB*IB
(2 element, 3W 3φ Delta)
VA*IA
VB*IB
-
IA
IB
-
3
VA*(IA-IB)/2 + VC*IC
(2 element, 4W 3φ Delta)
VA*(IA-IB)/2
-
VC*IC
IA-IB
IB
IC
4
VA*(IA-IB)/2 + VB*(IC-IB)/2
(2 element, 4W 3φ Wye)
VA*(IA-IB)/2
VB*(IC-IB)/2
IA-IB
IC-IB
IC
5
VA*IA + VB*IB + VC*IC
(3 element, 4W 3φ Wye)
VA*IA
VB*IB
IA
IB
IC
VC*IC
Table 2: Meter Element Output Mapping
ANALOG FRONT END
A/D Converter (ADC)
A single delta-sigma A/D converter (ADC) digitizes the inputs to the device. The resolution of the ADC is 21 bits. The ADC
operates at 5MHz oversampling rate and places the digital results in CE memory. Each analog input is sampled at 2520Hz.
Once each accumulation interval, it refreshes the temperature value that is placed in the TEMP_RAW register. The analog reference for all inputs is V3P3A, i.e. the ADC processes voltages between the input pins and V3P3A.
Voltage Reference
The device includes an on-chip precision bandgap voltage reference that incorporates auto-zero techniques as well as
production trims to minimize errors caused by component mismatch and drift. The result is a voltage output with a predictable
temperature coefficient.
The CE compensates for temperature characteristics of the voltage reference by modifying the gain applied to the V and I
channels based on the coefficients PPMC and PPMC2. See the section “TEMPERATURE COMPENSATION” for details.
DIGITAL COMPUTATION
The six ADC outputs are processed and accumulated digitally. The default product summation is based on 42*60 (if the
SUM_CYCLES register is set to 60) samples per accumulation interval. At the end of each accumulation interval, a ready
interrupt (IRQZ) is signaled (if enabled with the READY bit in STMASK), indicating that fresh data is available to the host. For
instance, if SUM_CYCLES =30, the IRQZ rate will be 2Hz (500ms).
A dedicated 32-bit Computation Engine (CE) performs the precision computations necessary to accurately measure energy.
Internal CE calculations include frequency-insensitive offset cancellation on all six channels and a frequency insensitive 90°
phase shifter for VAR calculations. The CE also includes LPF smoothing filters after each product and squaring circuit to
attenuate ripple and eliminate beat frequencies between the power line fundamental and the accumulation time. The CE
2
2
directly calculates Watts, VARs, V , and I and accumulates them for one interval.
At the end of each CE computation cycle, the accumulated data are post-processed to calculate RMS amplitudes, phase
angles, and VAh. When post-processing is complete, the IRQZ signal is activated.
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The minimum combined cycle time for CE and post-processor is 400ms, which makes the maximum frequency for the IRQZ
signal 2.5Hz.
If the 71M6515H is interfacing to an external DSP (typically, but not necessarily through the SSI interface), the host may turn
off post-processing by setting the CE_ONLY bit in the CONFIG word. This will permit setting SUM_CYCLES below its
recommended lower limit of 24. SUM_CYCLES may then be reduced to 1, creating an accumulation interval of only 42 samples.
The outputs available in CE only mode are limited to temperature, frequency, voltage phases, input signal zero crossings, plus
WSUM and VARSUM for each phase and VSQSUM, ISQSUM, and ISQFRACT for each phase.
Pulse Generators
The chip contains four pulse generators connected to the pins PULSEW, PULSER, PULSE3, and PULSE4 that create low
jitter pulses from 32-bit data. The peak time jitter for PULSEW and PULSER is the 397µs MUX frame period, and is
independent of the rate of the generator or the length of time the generator is monitored. Thus, if the pulse generator is
monitored for 1 second, the peak jitter is 400PPM. After 10 seconds, the peak jitter is 40PPM.
PULSE3 and PULSE4 are updated at a slower rate and have four times higher jitter, i.e. 160PPM after 10 seconds.
The average jitter is always zero. If it is attempted to drive either pulse generator faster than its maximum rate, it will simply
output at its maximum rate without exhibiting any roll-over characteristics.
Pulse generator inputs may be from three sources:
•
Internal (directly from the CE), PULSEW and PULSER only
•
External (controlled by the host writing to registers APULSEW, APULSER, APULSE3, APULSE4)
•
Post-processed values
The source is selected individually for each pulse output with the PULSEW_SRC, PULSER_SRC, PULSE3_SRC, and PULSE4_SRC
registers. Figure 7 shows internal pulse generation for the PULSEW output selected by writing the value 35 into the
PULSEW_SRC register.
35: WSUM
CE
2: WBSUM
35
PULSEW_SRC
3: WCSUM
4: VARSUM
POST PROCESSOR
0: WSUM
1: WASUM
PULSEW
OUTPUT
34: VAR2SUM_E
36: APULSEW
HOST
Figure 7: Internal Pulse Generation Selected in the PULSEW_SRC Register
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Internal data is pulsed out during the accumulation interval immediately following its accumulation interval. Post-processed
values are pulsed out one accumulation interval after that.
The pulse generator output rate depends on its input value, WRATE, PULSE_SLOW, and PULSE_FAST. Additionally, its
maximum pulse width (negative going pulse) is controlled by PULSEWIDTH. High frequency pulses will have 50% duty cycle
until their rate slows enough that their pulse width is limited by PULSEWIDTH.
In internal and post-processed modes, the pulse rate, expressed as Kh (Wh per pulse) is given by the formula:
Kh =
VMAX IMAX
1.5757 Wh / Pulse
In _ 8 ⋅ SUM _ CYCLES ⋅ WRATE ⋅ X
where
VMAX is the meter voltage corresponding to an input voltage of 176mV (rms) at the VA, VB, and VC input pins ,
IMAX is the meter current corresponding to an input voltage of 176mV (rms) at the IA, IB, and IC input pins,
In_8 is the additional ADC gain (1 or 8), as controlled by the IA_X, IB_X and IC_X bits in the CONFIG register.
X is the pulse speed factor determined from Table 3.
PULSE_SLOW
0
0
1
1 (default)
PULSE_FAST
0
1
0
1 (default)
X
2
1.5*2 =6
1.5*26=96
1.5*2-4=0.09375
1.5
Table 3: Pulse Speed Factor X
In external pulse mode, the pulse rate is given by the formula:
Rate(Hz) = WRATE * X * input * 35.82*10-12,
where input is the value in registers APULSER, APULSEW. APULSE3 or APULSE4,
X is the pulse speed factor determined from Table 3.
External pulse generation can be seen as providing the raw voltage and current readings equivalent to Vin*Iin / LSB directly to
the pulse generator.
The maximum pulse rate is 7.56kHz for PULSEW and PULSER, and 150Hz for PULSE3 and PULSE4.
In external pulse mode, the pulse generators load their data at the beginning of each CE accumulation interval, preserving any
partially implemented pulses from the previous interval. The source of data is controlled by the entries in the PULSE_SRCS
register. PULSER_SRCS contains 8-bit entries for each pulse source, PULSEW, PULSER, PULSE3, and PULSE4. See the
register description for details.
The procedure for accurate external pulse generation controlled by the host is:
1)
Respond to a READY interrupt by reading the accumulated values.
2)
Process the accumulated values.
3)
Write the processed value(s) to APULSER, APULSEW, APULSE3, or APULSE4. The host must write to APULSER,
APULSEW, APULSE3, and APULSE4 before the next READY interrupt for the pulse generation to be beginning in the
following accumulation interval.
Figure 8 illustrates pulse generator timing.
Regardless of the source, the pulse generators should receive new data during each accumulation interval. If this does not
occur and if the corresponding bit in the STMASK register is set, an APULSE_ERR interrupt will be issued.
The PULSEW, PULSER, PULSE3 and PULSE4 pins are suitable for driving LEDs through a current limiting resistor. The LED
should be connected so it is on when the pulse pin is low.
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The pin PULSE_INIT determines the logic level applied to the pulse pins on power-up, i.e. with PULSE_INIT low, the pulse
pins will be initialized to low (default = 1).
The pulse width PW is controlled with the PULSEWIDTH register for the PULSER and PULSEW output pins per the following
formula:
PW =
2 ⋅ PULSEWIDTH + 1
2520.6
The PULSE3 and PULSE4 output pins will always generate pulses with 50% duty cycle.
Internal Data (Directly by CE)
Accumulation Interval
CE Operations
Post Processing
Accumulation 2
Accumulation 1
XFER
XFER
Post 0
Pulse Generator
Accumulation 3
XFER
Post 2
Post 1
READY
READY
READY
Pulse 0
Pulse 1
Pulse 2
Post-Processed Data
Accumulation Interval
CE Operations
Post Processing
Accumulation 2
Accumulation 1
XFER
XFER
Post 0
Post 2
Post 1
READY
READY
APULSE write
Pulse 0
APULSE write
Pulse 1
READY
Pulse Generator
APULSE write
Pulse -1
Accumulation 3
XFER
External (Host data is transferred to the pulse generator in the first accumulation interval after the
next READY)
Accumulation Interval
CE Operations
Post Processing
XFER
Post 0
Pulse Generator
Host 0
APULSE write
Pulse -2
Accumulation 3
XFER
Post 2
Post 1
READY
Host Processing
Accumulation 2
Accumulation 1
XFER
READY
Host 1
APULSE write
Pulse -1
READY
Host 2
APULSE write
Pulse 0
Figure 8: Pulse Generator Timing
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Internal Resources
Oscillator
The oscillator drives a standard 32.768kHz watch crystal. Crystals of this type are accurate and do not require a high current
oscillator circuit. The 71M6515H oscillator has been designed specifically to handle watch crystals and is compatible with their
high impedance and limited power handling capability. The oscillator power dissipation is very low to maximize the lifetime of
any battery backup device attached to VBAT. Using PLL techniques, all internal clocks, such as the 4.915MHz clock for the
ADC and the post-processor, are derived from the watch crystal frequency.
Real-Time Clock (RTC)
The RTC is driven directly by the crystal oscillator. In the absence of V3P3, it is powered by the battery-backed up supply. The
RTC consists of a counter chain and output registers. The counter chain consists of registers for seconds, minutes, hours, day
of week, day of month, month, and year. The nominal quadratic temperature coefficient of the crystal is automatically
compensated in the RTC. The RTC is capable of processing leap years.
I/O Peripherals
The 71M6515H includes several I/O peripheral functions that improve the functionality of the device and reduce the
component count for most meter applications. The I/O peripherals include a UART and digital I/O.
Digital I/O
The device includes eight pins of general purpose digital I/O (D0…D7). Each pin can be configured independently as an input
or output with the D_DIR bits. Inputs are standard CMOS with no pull-ups or pull-downs. Outputs are standard CMOS. The
DIO pins are controlled by the D_CONFIG register.
Immediately after reset or power-up, D0 through D7 are in tri-state mode. 140 ms after reset, D0 through D7 are configured as outputs and driven low.
UART Host Interface
The UART is a dedicated 2-wire serial interface, which can communicate with the host processor. The operation of each pin is
as follows:
RX: Is the pin accepting the serial input data. It inputs data to internal registers. The bytes are input LSB first. The voltage
applied to this pin must be restricted to 0 to 3.6V.
TX: Is the pin used for serial output data. It outputs the contents of a block of internal registers. The bytes are output LSB
first.
BAUD_RATE: The baud rate can be selected with the BAUD_RATE pin (38.4bps when high, 19.2bps when low).
UARTCSZ: This pin enables the UART when low. The UART can be reset by taking UARTCSZ briefly to the high state and
then low again.
The 71M6515H has several on-chip registers, which can be read and written. All transfers start with a stream of 8-bit bytes
(LSB first) from the host on the RX input, followed by a (possibly null) stream of 8-bit bytes (LSB first) to the host on the TX
output (see Figure 9 and Figure 10). The UART is configured as 8N1 (8 bits, no parity, 1 stop bit).
If the READY bit in STMASK is enabled, the IRQZ pin can be used to signal data availability to the host. If data read cycles
exceeding 1 second are used, care should be taken to prevent data overflow.
UART Write Register Operation
The registers are written by sending a byte, consisting of a starting register address in the seven MSBs and ‘0’ in the LSB
indicating this is a write operation. It is followed by a one byte length of bytes to write. If more bytes arrive than fit in the
addressed register, subsequent registers will be written. The bytes are processed in “big-endian” order (i.e. most significant
byte first). See Figure 9 (read bits and bytes from left to right).
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L
W S
B
M
S
B
L
S
B
M
S
B
L
S
B
M
S
B
L
S
B
M
S
B
RX
register address
most significant
data byte
length
least significant
data byte
time
TX
Figure 9: UART Write Operation
UART Read Register Operation
The registers are read by sending a byte, consisting of a start register address in the seven MSBs and ‘1’ in the LSB indicating
this is a read operation. It is followed by a one byte length of bytes to read. If more bytes are asked for than the size of the
addressed register, subsequent registers will be read. The bytes are in “big-endian” order (i.e. most significant byte first). See
Figure 10.
L
R S
B
M
S
B
L
S
B
M
S
B
RX
register address
length
time
L
S
B
TX
M
S
B
most significant
data byte
L
S
B
M
S
B
least significant
data byte
Figure 10: UART Read Operation
Note: In both register read and write operations, the register address can be 0 through 127 (0x7F). The register address byte
is obtained by left-shifting the register address by one bit and setting bit 0 to 1 for read or setting bit 0 to 0 for write.
Synchronous Serial Interface (SSI)
A high speed, handshake, serial interface is available to send a contiguous block of CE data to an external data logger or
DSP. The block of data, configurable as to location and size, is sent at the beginning of each ADC multiplex cycle. The SSI
interface is enabled by the SSI_EN bit and consists of the outputs SSCLK, SSDATA, and SFR and of the SRDY input pin. The
interface is compatible with 16-bit and 32-bit processors. The operation of each pin is as follows:
SSCLK: This pin provides the serial clock. The clock can be 5MHz or 10MHz, as specified by the SSI_10M bit. The
SSI_CKGATE bit controls whether SSCLK runs continuously or is gated off when no SSI activity is occurring. If SSCLK is
gated, it will begin three cycles before SFR rises and will persist three cycles after the last data bit is output.
SSDATA: This pin provides the serial output data. SSDATA changes on the rising edge of SSCLK and outputs the contents
of a block of CE words starting with address SSI_STRT and ending with SSI_END. The words are output MSB first. SSDATA
is stable with the falling edge of SSCLK.
SFR: This pin provides the framing pulse. Although CE words are always 32 bits, the SSI interface will frame the entire data
block as a single field, as multiple 16 bit fields, or as multiple 32 bit fields. The SFR pulse is one clock cycle wide, changes
state on the rising edge of SSCLK and precedes the first bit of each field. The field size is set with SSI_FSIZE: 0-entire data
block, 1-8 bit fields, 2-16 bit fields, 3-32 bit fields. The polarity of the SFR pulse can be inverted with SSI_FPOL. The first
SFR pulse in a frame will rise on the third SSCLK clock period after MUX_SYNC (fourth SSCLK period, if SSCLK is 10MHz).
MUX_SYNC can be used to synchronize the fields arriving at the data logger or DSP.
SRDY: The SRDY input should always be tied to GND.
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The SSI timing is shown in Figure 11.
If 16bit fields
If SSI_CKGATE =1
If 32bit fields
If SSI_CKGATE =1
SFR (Output)
SCLK (Output)
31
SSDATA (Output)
30
16
15
1
0
31
30
SSI_BEG
16
15
1
SSI_BEG+1
0
1
31
0
SSI_END
MUX_STATE
Figure 11: SSI Timing (SSI_FPOL = SSI_RDYPOL = 0)
Fault and Reset Behavior
Reset Mode
When RESETZ is pulled low or when VFLT < V3P3/2, all activity (i.e. sampling of analog signals, CE, generation of digital
outputs) in the chip stops while the analog circuits are active. The exceptions are the oscillator and RTC module, which
continue to run. Additionally, all I/O Register bits are cleared. As long as VFLT > V3P3/2, the internal 2.5V regulator will
continue to provide power to the digital section.
Once initiated, the reset mode will persist until the reset timer times out. This will occur in 4100 cycles of the real time clock
after RESETZ goes high, at which time the 71M6515H will begin executing its preboot and boot sequences.
Power Fault Circuit
The power fault comparator compares the voltage at the VFLT pin to V3P3/2. The comparator output internally enables the
battery backup protection for oscillator, RTC and RAM during the power fail mode.
Temperature Compensation
Voltage Reference
The internal voltage reference of the 71M6515H is calibrated at 25°C during device manufacture. The 71M6515H is given
additional temperature-related calibrations which further compensate its ADC gain and allow it to achieve 10PPM/°C over
±60°C temperature range.
Temperature Sensor
The device includes an on-chip temperature sensor for determining the temperature of the bandgap reference. The primary
use of the temperature data is to determine the magnitude of compensation required to offset thermal drift in the system. The
temperature sensor is read once per accumulation interval.
Temperature measurement can be implemented with the following steps:
1)
At a known temperature TN, read the TEMP_RAW register and write the value into TEMP_NOM register.
2)
Read the DELTA_T register at the known temperature. The obtained value should be