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LTC2947
30A Power/Energy Monitor
with Integrated Sense Resistor
Features
nn Measures Current, Voltage, Power, Charge, Energy
nn ±30A Current Range with Low 9mA Offset
nn Integrated 300µΩ Sense Resistor
nn 0V to 15V Input Range Independent of Supply Voltage
nn Instantaneous Multiplication of Voltage and Current
nn 0.5% Voltage Accuracy
nn 1% Current and Charge Accuracy
nn 1.2% Power and Energy Accuracy
nn Alerts When Thresholds Exceeded
nn Stores Maximum and Minimum Values
nn
nn
SI2hCu/StdPoIwCnomMpoadteibwleitIhntIeQr<fa1ce0μA
nn Available in 32-Lead 4mm × 6mm QFN Package
Applications
nn Servers
nn Telecom Infrastructure
nn Industrial
nn Electric Vehicles
nn Photovoltaics
Description
The LTC®2947 is a high-precision power and energy
monitor with an internal sense resistor supporting up
to ±30A. Three internal No Latency Δ∑™ ADCs ensure
accurate measurement of voltage and current, while high-
bandwidth analog multiplication of voltage and current
provides accurate power measurement in a wide range of
applications. Internal or external clocking options enable
precise charge and energy measurements.
An internal 300µΩ, temperature-compensated sense
resistor minimizes efficiency loss and external compo-
nents, simplifying energy measurement applications while
enabling high accuracy current measurement over the full
temperature range.
All measured quantities are stored in internal registers ac-
cessible via the selectable I2C/SPI interface. The LTC2947
features programmable high and low thresholds for all
measured quantities to reduce digital traffic with the host.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and No
Latency ∆∑ and QuikEval are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners. Protected by U.S. Patents, including 8907703,
8841962.
Typical Application
0V TO 15V
IP 300µΩ IM
–30A TO 30A
5V AVCC
1µF
AGND
VP
DVCC LTC2947
1µF
DGND
VM
CFP
1µF
CFM
BYP
1µF AD1
AD0
CLKI
OVDD
SCL
SDI
SDO
ALERT
CLKO
LOAD
5V
SDI
SDA
I2C
INTERFACE
2947 TA01a
Energy Measurement Total Unadjusted
Error vs Current, VP – VM = 12V
0.5
0.4
INTERNAL CLOCK
EXTERNAL CLOCK
0.3
0.2
0.1
0.0
–0.1
–0.2
–0.3
–0.4
–0.5
0
10 20
ISENSE (A)
30
2947 TA01b
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LTC2947
Table of Contents
Description......................................................................................................................... 1
Absolute Maximum Ratings...................................................................................................... 3
Order Information.................................................................................................................. 3
Pin Configuration.................................................................................................................. 3
Electrical Characteristics......................................................................................................... 4
Timing Diagrams.................................................................................................................. 7
Typical Performance Characteristics........................................................................................... 8
Pin Functions......................................................................................................................10
Block Diagram.....................................................................................................................11
Operation.......................................................................................................................... 12
Overview................................................................................................................................................................ 12
Modes of Operation............................................................................................................................................... 12
Current, Voltage and Temperature Measurement................................................................................................... 14
Power Measurement.............................................................................................................................................. 14
Charge, Energy Measurement and Accumulated Time .......................................................................................... 14
Applications Information........................................................................................................15
TimeBase: Internal/External Clock/Crystal............................................................................................................ 15
Configuring the GPIO Pin....................................................................................................................................... 15
Internal Sense Resistor.......................................................................................................................................... 16
Current and Voltage Input Filtering........................................................................................................................ 16
Layout Considerations........................................................................................................................................... 17
Digital Interface...................................................................................................................19
Selecting SPI or I2C Serial Interface...................................................................................................................... 19
SPI Mode .............................................................................................................................................................. 19
I2C Mode .............................................................................................................................................................. 21
Register Map......................................................................................................................24
Register Description.............................................................................................................25
Register Naming Conventions............................................................................................................................... 25
Paging Mechanism................................................................................................................................................ 25
PAGE Control......................................................................................................................................................... 25
Operation Control.................................................................................................................................................. 25
Register Map PAGE0.............................................................................................................................................. 26
Register Map PAGE1.............................................................................................................................................. 37
Typical Applications..............................................................................................................39
Package Description.............................................................................................................41
Typical Application...............................................................................................................42
Related Parts......................................................................................................................42
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LTC2947
Absolute Maximum Ratings
(Notes 1, 2)
Supply Pins:
AVCC to AGND Voltage........................... –0.3V to 20V
DVCC to DGND Voltage........................... –0.3V to 20V
DGND to AGND Voltage.......................... –0.1V to 0.1V
Digital Input/Output Pins:
OVDD to DGND Voltage......................... –0.3V to 5.5V
SCL, SDI, SDO, GPIO, ALERT, AD1,
AD0 to DGND Voltage..........................–0.3V to VOVDD
CLKI to DGND Voltage........................... –0.3V to 5.5V
Analog Pins
VP, VM to AGND Voltage......................... –0.3V to 20V
VP to VM Voltage.................................... –0.3V to 20V
IP, IM Total Current (for 1ms)................... –50A to 50A
IP, IM Total Current (Note 7).................... –36A to 36A
IP, IM Current Per Pin (for 1ms)............. –8.3A to 8.3A
IP, IM Current Per Pin (Note 7).................... –6A to 6A
CFP, CFM, BYP, CLKO..................................... (Note 3)
Operating Ambient Temperature Range
LTC2947I................................................ –40° to 85°C
Storage Temperature Range..................... –65° to 150°C
Pin Configuration
TOP VIEW
IM 1
IM 2
IM 3
IM 4
IM 5
IM 6
AGND 7
DGND 8
AD0 9
AD1/CS 10
32 31 30 29 28 27
33
34
DGND
11 12 13 14 15 16
26 IP
25 IP
24 IP
23 IP
22 IP
21 IP
20 AVCC
19 DNC
18 DVCC
17 BYP
UFE PACKAGE
VARIATION: UFE32MA
32-LEAD PLASTIC QFN (4mm × 6mm)
TJMAX = 125°C, θJA = 50°C/W
EXPOSED PAD (PIN 33); DO NOT CONNECT
EXPOSED PAD (PIN 34) IS DGND, MAY BE CONNECTED TO DGND OR LEFT FLOATING
Order Information http://www.linear.com/product/LTC2947#orderinfo
TUBE
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2947IUFE#PBF
LTC2947IUFE#TRPBF 2947
32-Lead (4mm × 6mm) Plastic QFN
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
For more information www.linear.com/LTC2947
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LTC2947
E lectrical Characteristics The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX
UNITS
Power Supply
VAVCC, VDVCC Supply Voltage
VOVDD
Supply Voltage of Digital Interface
VUVLO
VAVCC, VDVCC Undervoltage Lockout
Threshold
VAVCC, VDVCC Falling
l 4.5
l 1.8
l
15 V
5.5 V
4.5 V
IAVCC Supply Current Analog Section Continuous Mode
Idle Mode
Shutdown Mode
Shutdown Mode
l
3 3.5
mA
l
0.2 0.3
mA
0.3 0.5
μA
l
0.3 1
µA
IDVCC
Supply Current Digital Section
Continuous Mode
Idle Mode
Shutdown Mode
Shutdown Mode
l
68
mA
l
68
mA
7 9.5
μA
l
7 90
µA
Delay of VAVCC,DVCC to VOVDD at
Power-Up
VOVDD, VAVCC, VDVCC ≥ 0.9 VOVDDfinal
(Note 8)
l
0
ns
Current Sense (IP, IM) ADC
Resolution (No Missing Codes)
(Note 5)
l 15
Bit
ISENSE
RSENSE
Input Current Through IP and IM
Internal Sense Resistor
Sense Resistor Voltage
(Note 6)
(Note 7)
Current through IP and IM = 30A
l ±30
l 140 300 450
9
A
µΩ
mV
Common Mode Input Voltage Range
l –0.1
15.5 V
LSBI Current Sense Quantization Step
Current Gain Error
3 mA
±0.75 % of reading
l ±1 % of reading
IOS Current Offset
±3 LSB
l ±5 LSB
INLI Current Integral Nonlinearity
TUEI Total Unadjusted Error
(Note 6)
|I| ≥ 6A (Note 6)
l
l
±0.3 %
±1 % of reading
±1.5 % of reading
Input DC Common Mode Rejection
l 120
dB
RMS Noise
(Note 5)
320 nV
Sampling Rate
10.5 MHz
Voltage Sense (VP, VM) ADC
Resolution (No Missing Codes)
(Note 5)
l 14
bit
Common Mode Voltage
l0
15.5 V
VD
Input Differential Voltage Range
VVP – VVM
VD Quantization Step
Voltage Gain Error
l –0.3
15.5 V
2 mV
l ±0.4 % of reading
Voltage Offset
l ±2 LSB
INLV Voltage Integral Nonlinearity
TUEV Voltage Total Unadjusted Error
VD ≥ 4.0V
Input DC Voltage Common Mode
Rejection
l
l
l 70
±2 LSB
±0.5 % of reading
dB
Sampling Rate
5.25 MHz
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LTC2947
E lectrical Characteristics The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C.
SYMBOL PARAMETER
CONDITIONS
MIN TYP MAX
UNITS
Power Measurement
Resolution (No Missing Codes)
(Note 5)
l 18
bit
Full-Scale Power
450 W
Power Quantization Step
50 mW
Power Gain Error
±0.8 % of reading
l ±1 % of reading
Power Offset
±4 LSB
l ±6 LSB
INLP Power Integral Nonlinearity
|I| ≥ 6A, VD ≥ 12V (Note 6)
l
±0.3 % of reading
±0.5 % of reading
TUEP
Power Total Unadjusted Error
|I| ≥ 6A, VD ≥ 12V (Note 6)
l
±1.2 % of reading
±1.5 % of reading
Sampling Rate
5.25 MHz
Timing
TUETB
Time Base Total Unadjusted Error
Internal Clock
l
±0.5 % of reading
±1 % of reading
Ideal External Clock or Ideal 4MHz
Crystal (Note 5)
l
±340 ppm
tUPDATE
Update Time of Result Registers
Energy Measurement
l 95
100 105
ms
TUEE Energy Total Unadjusted Error
|I| ≥ 6A,
(Note 6)
VD
12V,
Ideal
External
Clock
l
±1.2 % of reading
±1.5 % of reading
|I| ≥ 6A,
(Note 6)
VD
12V,
Internal
Clock
l
±1.5 % of reading
±2.5 % of reading
Charge Measurement
TUEC
Charge Total Unadjusted Error
|I| ≥ 6A, Ideal External Clock (Note 6)
l
±1 % of reading
±1.5 % of reading
|I| ≥ 6A, Internal Clock (Note 6)
l
±1.5 % of reading
±2.5 % of reading
Temperature Measurement ADC
Resolution (No Missing Codes)
(Note 5)
l 13
bit
Temperature Quantization Step
0.204
°C
Temperature Error
(Note 5)
±5 K
Digital Inputs and Digital Outputs SCL, SDI, GPIO, ALERT, SDO, CS, CLKI, ADO
VITH Logic Input Threshold
SCL, SDI, GPIO, CS, ADO
l 0.3 VOVDD
0.7 VOVDD
IIN Input Current SCL, SDI, GPIO
l ±1
CIN Input Capacitance
(Note 5)
l 10
VOL Low Level Output Voltage SDO, GPIO, VOVDD ≥ 3.3V, IPIN = 3mA
l
ALERT
1.8V ≤ VOVDD < 3.3V, IPIN = 1mA
l
0.4
0.4
VOH
High Level Output Voltage (SDO)
ISDAO = –0.5mA
l VOVDD – 0.5
CLKI Input Threshold
l 0.4
0.7
2
V
μA
pF
V
V
V
V
External Clock Frequency on Pin CLKI
l 0.2
25 MHz
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