TI INA230AIRGTT

INA230
SBOS601 – FEBRUARY 2012
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High- or Low-Side Measurement,
Bidirectional CURRENT/POWER MONITOR with I2C™ Interface
Check for Samples: INA230
FEATURES
DESCRIPTION
•
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The INA230 is a current-shunt and power monitor
with an I2C interface that features 16 programmable
addresses. The INA230 monitors both shunt voltage
drops and bus supply voltage. Programmable
calibration value, conversion times, and averaging,
combined with an internal multiplier, enable direct
readouts of current in amperes and power in watts.
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23
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Bus Voltage Sensing From 0 V to +28 V
High- or Low-Side Sensing
Current, Voltage, and Power Reporting
High Accuracy:
– 0.5% Gain Error (Max)
– 50-μV Offset (Max)
Configurable Averaging Options
Programmable Alert Threshold
Power Supply Operation: 2.7 V to 5.5 V
Package: 3-mm x 3-mm, 16-Pin QFN
The INA230 senses current on buses that vary from 0
V to +28 V, with the device powered from a single
+2.7 V to +5.5 V supply, drawing 330 μA (typical) of
supply current. The INA230 is specified over the
operating temperature range of –40°C to +125°C.
RELATED PRODUCTS
APPLICATIONS
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DESCRIPTION
Smartphones
Tablets
Servers
Computers
Power Management
Battery Chargers
Power Supplies
Test Equipment
DEVICE
Current/power monitor with watchdog, peak-hold,
and fast comparator functions
INA209
Zerø-drift, low-cost, analog current shunt monitor
series in small package
INA210, INA211,
INA212, INA213,
INA214
Zerø-drift, bidirectional current power monitor with
two-wire interface
INA219
High or low side, bidirectional current/power monitor
with two-wire interface
INA220
HIGH-OR LOW-SIDE SENSING
Power Supply
(0 V to 28 V)
HighSide
Shunt
CBYPASS
0.1 mF
VS
(Supply Voltage)
BUS
INA230
SDA
SCL
´
Load
Power Register
V
2
Current Register
ADC
LowSide
Shunt
I
Voltage Register
IC
Interface
ALERT
A0
Alert Register
A1
GND
1
Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas
Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.
I C is a trademark of NXP Semiconductors.
All other trademarks are the property of their respective owners.
2
2
3
PRODUCTION DATA information is current as of publication date.
Products conform to specifications per the terms of the Texas
Instruments standard warranty. Production processing does not
necessarily include testing of all parameters.
Copyright © 2012, Texas Instruments Incorporated
INA230
SBOS601 – FEBRUARY 2012
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This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with
appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more
susceptible to damage because very small parametric changes could cause the device not to meet its published specifications.
PACKAGE INFORMATION (1)
(1)
PRODUCT
PACKAGE-LEAD
PACKAGE DESIGNATOR
PACKAGE MARKING
INA230
QFN-16
RGT
I230
For the most current package and ordering information see the Package Option Addendum at the end of this document, or see the
INA230 product folder at www.ti.com.
ABSOLUTE MAXIMUM RATINGS (1)
Over operating free-air temperature range (unless otherwise noted).
Supply voltage, VS
INA230
UNIT
6
V
Differential (VIN+) – (VIN–) (2)
–30 to +30
V
Common-mode
–0.3 to +30
V
SDA
GND – 0.3 to +6
V
SCL
Analog inputs, IN+, IN–
GND – 0.3 to VS + 0.3
V
Input current into any pin
5
mA
Open-drain digital output current
10
mA
Storage temperature
–65 to +150
°C
Junction temperature
+150
°C
Human body model (HBM)
2500
V
Charged-device model (CDM)
1000
V
Machine model (MM)
150
V
ESD Ratings
(1)
(2)
2
Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may
degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond
those specified is not implied.
VIN+ and VIN– may have a differential voltage of –30 V to +30 V; however, the voltage at these pins must not exceed the range –0.3 V to
+30 V.
Copyright © 2012, Texas Instruments Incorporated
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SBOS601 – FEBRUARY 2012
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ELECTRICAL CHARACTERISTICS
At TA = +25°C, VS = +3.3 V, VIN+ = 12 V, VSENSE = (VIN+ – VIN–) = 0 mV, and VBUS = 12 V, unless otherwise noted.
INA230
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNIT
SHUNT INPUT
Shunt voltage input range
CMR
Common-mode rejection
VOS
Shunt offset voltage, RTI (1)
PSRR
vs power supply
-81.92
VIN+ = 0 V to +28 V
100
81.9175
120
mV
dB
±10
±50
μV
TA = –40°C to +125°C
0.1
0.5
μV/°C
VS = +2.7 V to +5.5 V
10
μV/V
BUS INPUT
Bus voltage input range (2)
VOS
Bus offset voltage, RTI (1)
PSRR
vs power supply
0
TA = –40°C to +125°C
28
V
±5
±30
mV
10
40
μV/°C
2
BUS pin input impedance
mV/V
830
kΩ
INPUT
IIN+, IIN-
Input bias current
Input leakage (3)
μA
10
0.5
μA
(VIN+) + (VIN–), Power-Down mode
0.1
Shunt voltage
2.5
μV
1.25
mV
DC ACCURACY
ADC native resolution
1 LSB step size
Shunt voltage gain error
Bus voltage gain error
16
Bus voltage
TA = –40°C to +125°C
TA = –40°C to +125°C
0.2
0.5
%
10
50
ppm/°C
0.2
0.5
%
10
50
ppm/°C
±0.1
Differential nonlinearity
ADC conversion time
Bits
LSB
CT bit = 000
140
154
μs
CT bit = 001
204
224
μs
CT bit = 010
332
365
μs
CT bit = 011
588
646
μs
CT bit = 100
1.1
1.21
ms
CT bit = 101
2.116
2.328
ms
CT bit = 110
4.156
4.572
ms
CT bit = 111
8.244
9.068
ms
28
35
ms
1
μA
SMBus
SMBus timeout (4)
DIGITAL INPUT/OUTPUT
Input capacitance
Leakage input current
3
0 ≤ VIN ≤ VS
0.1
pF
VIH
High-level input voltage
0.7(VS)
6
V
VIL
Low-level input voltage
–0.5
0.3(VS)
V
VOL
Low-level output voltage (SDA, ALERT) IOL = 3 mA
0
0.4
Hysteresis
(1)
(2)
(3)
(4)
500
V
mV
RTI = Referred-to-input.
Although the input range is 28 V, the full-scale range of the ADC scaling is 40.96 V. Do not apply more than 28 V. See the Basic ADC
Functions section for more details
Input leakage is positive (current flowing into the pin) for the conditions shown at the top of this table. Negative leakage currents can
occur under different input conditions.
SMBus timeout in the INA230 resets the interface any time SCL is low for more than 28 ms.
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ELECTRICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = +3.3 V, VIN+ = 12 V, VSENSE = (VIN+ – VIN–) = 0 mV, and VBUS = 12 V, unless otherwise noted.
INA230
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNIT
POWER SUPPLY
Operating supply range
+2.7
Quiescent current
Power-Down mode
Power-on reset threshold
+5.5
V
330
420
μA
0.5
2
μA
2
V
TEMPERATURE
–40
Specified range
+125
°C
THERMAL INFORMATION
INA230
THERMAL METRIC
(1)
RGT (QFN)
UNITS
10 PINS
θJA
Junction-to-ambient thermal resistance
46.1
θJCtop
Junction-to-case (top) thermal resistance
58.4
θJB
Junction-to-board thermal resistance
19.1
ψJT
Junction-to-top characterization parameter
1.3
ψJB
Junction-to-board characterization parameter
19.1
θJCbot
Junction-to-case (bottom) thermal resistance
4.7
(1)
4
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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PIN CONFIGURATIONS
NC
NC
NC
IN+
16
15
14
13
RGT PACKAGE
QFN-16
(TOP VIEW)
ALERT
3
10
GND
SDA
4
9
VS+
8
BUS
NC
11
7
2
NC
A0
6
IN-
NC
12
5
1
SCL
A1
PIN DESCRIPTIONS
PIN
NAME
NO.
ANALOG/DIGITAL
INPUT/OUTPUT
DESCRIPTION
A0
2
Digital input
Address pin. Connect to GND, SCL, SDA, or VS. Table 7 shows pin settings and
corresponding addresses.
A1
1
Digital input
Address pin. Connect to GND, SCL, SDA, or VS. Table 7 shows pin settings and
corresponding addresses.
ALERT
3
Digital output
GND
10
Analog
NC
6, 7, 8, 14, 15, 16
—
SCL
5
Digital input
SDA
4
Digital input/output
BUS
11
Analog input
Bus voltage input
IN–
12
Analog input
Negative differential shunt voltage input. Connect to load side of shunt resistor.
IN+
13
Analog input
Positive differential shunt voltage input. Connect to supply side of shunt resistor.
VS
9
Analog
Thermal Pad
Multi-functional alert, open-drain output.
Ground
No internal connection
Serial bus clock line, open-drain input.
Serial bus data line, open-drain input/output.
Power supply, 2.7 V to 5.5 V.
This pad can be connected to ground or left floating.
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REGISTER BLOCK DIAGRAM
Power
(1)
Bus Voltage
(1)
´
Shunt Voltage
Channel
Current
(1)
ADC
Bus Voltage
Channel
Calibration
(2)
´
Shunt Voltage
(1)
Data Registers
(1)
Read-only
(2)
Read/write
Figure 1. Register Block Diagram
6
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TYPICAL CHARACTERISTICS
At TA = +25°C, VS = +3.3 V, VIN+ = 12 V, VSENSE = (VIN+ – VIN–) = 0 mV, and VBUS = 12 V, unless otherwise noted.
SHUNT INPUT OFFSET VOLTAGE
PRODUCTION DISTRIBUTION
FREQUENCY RESPONSE
0
−10
Population
Gain (dB)
−20
−30
−40
−50
1
10
100
1k
Frequency (Hz)
10k
100k
−50
−45
−40
−35
−30
−25
−20
−15
−10
−5
0
5
10
15
20
25
30
35
40
45
50
−60
G001
Input Offset Voltage (µV)
Figure 3.
SHUNT INPUT OFFSET VOLTAGE
vs TEMPERATURE
SHUNT INPUT COMMON-MODE REJECTION RATIO
vs TEMPERATURE
−9
Common-Mode Rejection Ratio (dB)
170
−9.2
−9.4
Offset (µV)
G002
Figure 2.
−9.6
−9.8
−10
−10.2
−10.4
−50
−25
0
25
50
Temperature (°C)
75
100
160
150
140
−50
125
−25
0
G003
Figure 4.
25
50
Temperature (°C)
75
100
125
G004
Figure 5.
SHUNT INPUT GAIN ERROR PRODUCTION DISTRIBUTION
SHUNT INPUT GAIN ERROR vs TEMPERATURE
600
Population
Gain Error (m%)
500
400
300
200
Shunt Gain Error (m%)
0
−50
500
400
300
200
100
0
−100
−200
−300
−400
−500
100
−25
0
25
50
Temperature (°C)
75
100
125
G006
G005
Figure 6.
Figure 7.
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TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = +3.3 V, VIN+ = 12 V, VSENSE = (VIN+ – VIN–) = 0 mV, and VBUS = 12 V, unless otherwise noted.
SHUNT INPUT GAIN ERROR
vs COMMON-MODE VOLTAGE
BUS INPUT OFFSET VOLTAGE
PRODUCTION DISTRIBUTION
300
200
Population
Gain Error (m%)
250
150
100
50
G007
30
25
27.5
20
22.5
15
17.5
10
12.5
5
7.5
36
0
32
2.5
8
12
16
20
24
28
Common−Mode Input Voltage (V)
−2.5
4
−5
0
−5
−50
−15
0
Input Offset Voltage (mV)
G008
Figure 8.
Figure 9.
BUS INPUT OFFSET VOLTAGE vs TEMPERATURE
BUS INPUT GAIN ERROR PRODUCTION DISTRIBUTION
−0.6
Population
Offset (mV)
−0.8
−1.0
G009
BUS INPUT GAIN ERROR vs TEMPERATURE
500
400
INPUT BIAS CURRENT vs COMMON-MODE VOLTAGE
25
Input Bias Current (µA)
500
Gain Error (m%)
G010
Figure 11.
600
400
300
200
100
−25
0
25
50
Temperature (°C)
75
100
125
20
15
10
5
0
0
G011
Figure 12.
8
300
Input Gain Error (m%)
Figure 10.
0
−50
200
125
100
100
0
75
−100
25
50
Temperature (°C)
−200
0
−300
−25
−400
−1.4
−50
−500
−1.2
4
8
12
16
20
24
28
Common-Mode Input Voltage (V)
32
36
G012
Figure 13.
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TYPICAL CHARACTERISTICS (continued)
At TA = +25°C, VS = +3.3 V, VIN+ = 12 V, VSENSE = (VIN+ – VIN–) = 0 mV, and VBUS = 12 V, unless otherwise noted.
INPUT BIAS CURRENT vs TEMPERATURE
INPUT BIAS CURRENT vs TEMPERATURE, SHUTDOWN
260
Input Bias Current − Shutdown (nA)
Input Bias Current (µA)
24
22
20
18
16
−50
−25
0
25
50
Temperature (°C)
75
100
220
180
140
100
60
20
−50
125
−25
0
G013
Figure 14.
ACTIVE IQ vs TEMPERATURE
100
125
G014
SHUTDOWN IQ vs TEMPERATURE
1.2
Quiescent Current − Shutdown (µA)
Quiescent Current (µA)
75
Figure 15.
500
400
300
200
100
−50
25
50
Temperature (°C)
−25
0
25
50
Temperature (°C)
75
100
1
0.8
0.6
0.4
0.2
−50
125
−25
0
G015
25
50
Temperature (°C)
75
100
125
G016
Figure 16.
Figure 17.
ACTIVE IQ vs I2C CLOCK FREQUENCY
SHUTDOWN IQ vs I2C CLOCK FREQUENCY
500
300
250
Shutdown IQ (mA)
IQ (mA)
450
400
200
150
100
350
50
300
0
1
10
100
1,000
10,000
1
10
100
Frequency (kHz)
Frequency (kHz)
Figure 18.
Figure 19.
1,000
10,000
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APPLICATION INFORMATION
The INA230 is a digital current shunt monitor with an I2C- and SMBus-compatible interface. This device provides
digital current, voltage, and power readings necessary for accurate decision-making in precisely-controlled
systems. Programmable registers allow flexible configuration for measurement resolution, as well as
continuous-versus-triggered operation. Detailed register information appears towards the end of this data sheet,
beginning with Table 2. See Figure 1 for a block diagram of the INA230.
INA230 TYPICAL APPLICATION
The figure on the front page shows a typical application circuit for the INA230. For power-supply bypassing, use
a 0.1-μF ceramic capacitor placed as close as possible to the supply and ground pins.
BASIC ANALOG-TO_DIGITAL CONVERTER (ADC) FUNCTIONS
The INA230 performs two measurements on the power-supply bus of interest. The voltage developed from the
load current that flows through a shunt resistor creates the shunt voltage signal that is measured at the IN+ and
IN– pins. The device can also measure the power supply bus voltage by connecting this voltage to the BUS pin.
The differential shunt voltage is measured with respect to the IN– pin while the bus voltage is measured with
respect to ground.
The INA230 is typically powered by a separate supply that can range from 2.7 V to 5.5 V. The bus that is being
monitored can range in voltage from 0 V to 28 V. NOTE: Based on the fixed 1.25 mV LSB for the bus voltage
register, a full-scale register would result in a 40.96-V value. However, the actual voltage that is applied
to the input pins of the INA230 should not exceed 28 V. There are no special considerations for power-supply
sequencing because the common-mode input range and power-supply voltage are independent of each other;
therefore, the bus voltage can be present with the supply voltage off, and vice-versa.
As noted, the INA230 takes two measurements, shunt voltage and bus voltage. It then converts these
measurements to current, based on the Calibration register value, and then calculates power. Refer to the
Configure/Measure/Calculate Example section for additional information on programming the Calibration register.
The INA230 has two operating modes, continuous and triggered, that determine how the ADC operates after
these conversions. When the INA230 is in the normal operating mode (that is, the MODE bits of the
Configuration register are set to '111'), it continuously converts a shunt voltage reading followed by a bus voltage
reading. After the shunt voltage reading, the current value is calculated based on Equation 3. This current value
is then used to calculate the power result using Equation 4. These values are subsequently stored in an
accumulator, and the measurement/calculation sequence repeats until the number of averages set in the
Configuration register is reached. Note that the current and power calculations are based on the value
programmed into the Calibration register. If the Calibration register is not programmed, the result of the current
and power calculations is zero. Following every sequence, the present set of measured and calculated values
are appended to the previously collected values. After all of the averaging has been completed, the final values
for shunt voltage, bus voltage, current, and power are updated in the corresponding registers and can then be
read. These values remain in the data output registers until they are replaced by the next fully completed
conversion results. Reading the data output registers does not affect a conversion in progress.
The mode control bits in the Configuration register also permit selecting specific modes to convert only the shunt
voltage or the bus voltage in order to further allow the monitoring function configuration to fit specific application
requirements.
All current and power calculations are performed in the background and do not contribute to conversion time.
In triggered mode, writing any of the triggered convert modes into the Configuration register (that is, the MODE
bits of the Configuration register are set to ‘001’, ‘010’, or ‘011’) triggers a single-shot conversion. This action
produces a single set of measurements. To trigger another single-shot conversion, the Configuration register
must be written to again, even if the mode does not change.
In addition to the two operating modes (continuous and triggered), the INA230 also has a power-down mode that
reduces the quiescent current and turns off current into the INA230 inputs, which reduces the impact of supply
drain when the device is not being used. Full recovery from power-down mode requires 40 ms. The registers of
the INA230 can be written to and read from while the device is in power-down mode. The device remains in
power-down mode until one of the active modes settings are written into the Configuration register.
10
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Although the INA230 can be read at any time, and the data from the last conversion remain available, the
Conversion Ready Flag bit (CVRF bit, Mask/Enable register) is provided to help coordinate single-shot or
triggered conversions. The CVRF bit is set after all conversions, averaging, and multiplication operations are
complete for a single cycle.
The CVRF bit clears under these conditions:
1. Writing to the Configuration register, except when configuring the MODE bits for power-down mode; or
2. Reading the Status register.
Power Calculation
The current and power are calculated after shunt voltage and bus voltage measurements, as shown in Figure 20.
The current is calculated after a shunt voltage measurement based on the value set in the Calibration register. If
there is no value loaded into the Calibration register, the current value stored is zero. Power is calculated
following the bus voltage measurement based on the previous current calculation and bus voltage measurement.
If there is no value loaded in the Calibration register, the power value stored is also zero. These calculations are
performed in the background and do not add to the overall conversion time. These current and power values are
considered intermediate results (unless the averaging is set to 1) and are stored in an internal accumulation
register, not the corresponding output registers. Following every measured sample, the newly-calculated values
for current and power are appended to this accumulation register until all of the samples have been measured
and averaged based on the number of averages set in the Configuration register.
Bus and Power Limit Detect
Following Every Bus Voltage Conversion
Current Limit Detect Following
Every Shunt Voltage Conversion
I
V
I
P
V
I
P
V
I
P
V
I
V
P
I
P
V
I
P
V
I
P
V
I
P
V
I
V
P
I
P
V
I
P
V
I
P
V
I
P
V
I
P
V
I
V
P
P
Power Average
Bus Voltage Average
Shunt Voltage Average
Figure 20. Power Calculation Scheme
In addition to the current and power accumulating after every sample, the shunt and bus voltage measurements
are also collected. Once all of the samples have been measured and the corresponding current and power
calculations have been made, the accumulated average for each of these parameters is then loaded to the
corresponding output registers, where they can then be read.
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Averaging and Conversion Time Considerations
The INA230 has programmable conversion times for both the shunt voltage and bus voltage measurements. The
conversion times for these measurements can be selected from as fast as 140 μs to as long as 8.244 ms. The
conversion time settings, along with the programmable averaging mode, allow the INA230 to be configured to
optimize the available timing requirements in a given application. For example, if a system requires that data be
read every 5 ms, the INA230 can be configured with the conversion times set to 588 μs and the averaging mode
set to 4. This configuration results in the data updating approximately every 4.7 ms. The INA230 can also be
configured with a different conversion time setting for the shunt and bus voltage measurements. This type of
approach is common in applications where the bus voltage tends to be relatively stable. This situation allows for
the time spent measuring the bus voltage to be reduced relative to the shunt voltage measurement. The shunt
voltage conversion time can be set to 4.156 ms with the bus voltage conversion time set to 588μs, and the
averaging mode set to 1. This configuration also results in data updating approximately every 4.7 ms.
There are trade-offs associated with the settings for conversion time and the averaging mode used. The
averaging feature can significantly improve the measurement accuracy by effectively filtering the signal. This
approach allows the INA230 to reduce noise in the measurement that may be caused by noise coupling into the
signal. A greater number of averages enables the INA230 to be more effective in reducing the noise component
of the measurement.
The conversion times selected can also have an impact on the measurement accuracy; this effect can be seen in
Figure 21. Multiple conversion times are shown here to illustrate the impact of noise on the measurement. In
order to achieve the highest accuracy measurement possible, a combination of the longest allowable conversion
times and highest number of averages should be used, based on the timing requirements of the system.
10mV/div
Conversion Time: 140ms
Conversion Time: 1.1ms
Conversion Time: 8.244ms
0
200
400
600
800
1000
Number of Conversions
Figure 21. Noise vs Conversion Time
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Filtering and Input Considerations
Measuring current is often a noisy task, and such noise can be difficult to define. The INA230 offers several
options for filtering by allowing the conversion times and number of averages to be independently selected in the
Configuration register. The conversion times can be independently set for the shunt voltage and bus voltage
measurements to allow added flexibility in configuring the monitoring of the power-supply bus.
The internal ADC is based on a delta-sigma (ΔΣ) front-end with a 500 kHz (±30%) typical sampling rate. This
architecture has good inherent noise rejection; however, transients that occur at or very close to the sampling
rate harmonics can cause problems. Because these signals are at 1 MHz and higher, they can be managed by
incorporating filtering at the input of the INA230. The high frequency enables the use of low-value series resistors
on the filter with negligible effects on measurement accuracy. In general, filtering the INA230 input is only
necessary if there are transients at exact harmonics of the 500-kHz (±30%) sampling rate (greater than 1 MHz).
Filter using the lowest possible series resistance (typically 10 Ω or less) and a ceramic capacitor. Recommended
values for this capacitor are 0.1 μF to 1.0 μF. Figure 22 shows the INA230 with an additional filter added at the
input.
Overload conditions are another consideration for the INA230 inputs. The INA230 inputs are specified to tolerate
30 V across the inputs. A large differential scenario might be a short to ground on the load side of the shunt. This
type of event can result in full power-supply voltage across the shunt (as long as the power supply or energy
storage capacitors support it). Keep in mind that removing a short to ground can result in inductive kickbacks that
could exceed the 30-V differential and common-mode rating of the INA230. Inductive kickback voltages are best
controlled by zener-type transient-absorbing devices (commonly called transzorbs) combined with sufficient
energy storage capacitance.
In applications that do not have large energy-storage electrolytics on one or both sides of the shunt, an input
overstress condition may result from an excessive dV/dt of the voltage applied to the input. A hard physical short
is the most likely cause of this event, particularly in applications with no large electrolytics present. This problem
occurs because an excessive dV/dt can activate the ESD protection in the INA230 in systems where large
currents are available. Testing has demonstrated that the addition of 10-Ω resistors in series with each input of
the INA230 sufficiently protect the inputs against this dV/dt failure up to the 30-V rating of the INA230. Selecting
these resistors in the range noted has minimal effect on accuracy.
Power Supply
(0 V to 28 V)
CBYPASS
0.1 mF
VS
(Supply Voltage)
BUS
CFILTER
0.1 mF to 1 mF
Ceramic
Capacitor
SDA
SCL
´
RFILTER
£10 W
IN+
Power Register
V
2
Current Register
ADC
I
Load
RFILTER
£10 W
Voltage Register
IC
Interface
ALERT
A0
INAlert Register
A1
GND
Figure 22. INA230 with Input Filtering
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ALERT PIN
The INA230 has a single Alert Limit register (07h) that allows the ALERT pin to be programmed to respond to a
single user-defined event or to a conversion ready notification if desired. The Mask/Enable register allows for
selecton from one of the five available functions to monitor and/or set the conversion ready bit (CNVR,
Mask/Enable register) to control the response of the ALERT pin. Based on the function being monitored, a value
would then be entered into the Alert Limit register to set the corresponding threshold value that asserts the
ALERT pin.
The ALERT pin allows for one of several available alert functions to be monitored to determine if a user-defined
threshold has been exceeded. The five alert functions that can be monitored are:
• Shunt Voltage Over Limit (SOL)
• Shunt Voltage Under Limit (SUL)
• Bus Voltage Over Limit (BOL)
• Bus Voltage Under Limit (BUL)
• Power Over Limit (POL)
The ALERT pin is an open-drain output. This pin is asserted when the alert function selected in the Mask/Enable
register exceeds the value programmed into the Alert Limit register. Only one of these alert functions can be
enabled and monitored at a time. If multiple alert functions are enabled, the selected function in the highest
significant bit position takes priority and responds to the Alert Limit register value. For example, if the SOL and
the SUL are both selected, the ALERT pin asserts when the Shunt Voltage Over Limit register exceeds the value
in the Alert Limit register.
The conversion ready state of the device can also be monitored at the ALERT pin to inform the user when the
device has completed the previous conversion and is ready to begin a new conversion. The conversion ready
flag (CVRF) bit can be monitored at the ALERT pin along with one of the alert functions. If an alert function and
the CNVR bit are both enabled to be monitored at the ALERT pin, then after the ALERT pin is asserted, the
Mask/Enable register must be read following the alert to determine the source of the alert. By reading the CVRF
bit (D3), and the AFF bit (D4) in the Mask/Enable register, the source of the alert can be determined. If the
conversion ready feature is not desired, and the CNVR bit is not set, the ALERT pin only responds to an
exceeded alert limit based on the alert function enabled.
If the alert function is not used, the ALERT pin can be left floating without impacting the operation of the device.
Refer to Figure 20 to see the relative timing of when the value in the Alert Limit register is compared to the
corresponding converted value. For example, if the alert function that is enabled is Shunt Voltage Over Limit
(SOL), following every shunt voltage conversion the value in the Alert Limit register is compared to the measured
shunt voltage to determine if the measurements have exceeded the programmed limit. The AFF bit (D4,
Mask/Enable register) asserts high any time the measured voltage exceeds the value programmed into the Alert
Limit register. In addition to the AFF bit being asserted, the ALERT pin is asserted based on the Alert Polarity bit
(APOL, D1, Mask/Enable register). If the Alert Latch is enabled, the AFF bit and ALERT pin remain asserted until
either the Configuration register is written to or the Mask/Enable register is read.
The bus voltage alert functions (BOL and BUL, Mask/Enable register) compare the measured bus voltage to the
Alert Limit register following every bus voltage conversion and assert the AFF bit and ALERT pin if the limit
threshold is exceeded.
The power over limit alert function (POL, Mask/Enable Regsiter) is also compared to the calculated power value
following every bus voltage measurement conversion and asserts the AFF bit and ALERT pin if the limit
threshold is exceeded.
With the alert function comparing the programmed alert limit value to the result of each corresponding
conversion, it is possible to have an alert issued during a conversion cycle where the averaged value of the
signal does not exceed the alert limit. The triggering of the alert based on this intermediate conversion allows for
out-of-range events to be detected more quickly than the averaged output data registers are updated. This can
be used to create alert limits for quickly changing conditions through the use of the alert function, as well as to
create limits to longer-duration conditions through software monitoring of the averaged output values.
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PROGRAMMING THE INA230
An important aspect of the INA230 is that it does not necessarily measure current or power. The INA230
measures both the differential voltage applied between the IN+ and IN– input pins and the voltage applied to the
BUS pin. In order for the INA230 to report both current and power values, both the Current register resolution
and the value of the shunt resistor present in the application that resulted in the differential voltage being
developed must be programmed. The Power register is internally set to be 25 times the programmed least
significant bit of the current register (Current_LSB). Both the Current_LSB and shunt resistor value are used
when calculating the Calibration register value. The INA230 uses this value to calculate the corresponding
current and power values based on the measured shunt and bus voltages.
The Calibration register is calculated based on Equation 1. This equation includes the term Current_LSB, the
programmed value for the LSB for the Current register. This is the value used to convert the value in the Current
register to the actual current in amps. The highest resolution for the Current register can be obtained by using
the smallest allowable Current_LSB based on the maximum expected current, as shown in Equation 2. While this
value yields the highest resolution, it is common to select a value for the Current_LSB to the nearest round
number above this value to simplify the conversion of the Current register and Power register to amps and watts
respectively. RSHUNT is the value of the external shunt used to develop the differential voltage across the input
pins. The 0.00512 value in Equation 1 is an internal fixed value used to ensure scaling is maintained properly.
0.00512
CAL = Current_LSB · R
SHUNT
Current_LSB =
(1)
Maximum Expected Current
215
(2)
After the Calibration register has been programmed, the Current register and Power register are updated
accordingly based on the corresponding shunt voltage and bus voltage measurements. Until the Calibration
register is programmed, the Current and Power registers remain at zero.
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CONFIGURE/MEASURE/CALCULATE EXAMPLE
In this example, shown in Figure 23, a nominal 10-A load creates a differential voltage of 20 mV across a 2-mΩ
shunt resistor. The bus voltage for the INA230 is measured at the external BUS input pin; in this example, BUS
is connected to the IN– pin to measure the voltage level delivered to the load. For this example, the BUS pin
measures less than 12 V because the voltage at the IN– pin is 11.98 V as a result of the voltage drop across the
shunt resistor.
+12-V Supply
CBYPASS
0.1 mF
VS
(Supply Voltage)
BUS
SDA
SCL
´
IN+
Power Register
V
2
IC
Interface
Current Register
ADC
RSHUNT
2 mW
I
ALERT
Voltage Register
A0
IN-
A1
Alert Register
10A
Load
GND
Figure 23. Example Circuit Configuration
For this example, assuming a maximum expected current of 15 A, the Current_LSB is calculated to be 457.7
μA/bit using Equation 2. Using a value of 500 μA/bit or 1 mA/bit for the Current_LSB significantly simplifies the
conversion from the Current register and Power register to amps and watts. For this example, a value of 1 mA/bit
was chosen for the Current register LSB. Using this value for the Current_LSB trades a small amount of
resolution for a simpler conversion process on the processor side. Using Equation 1 in this example with a
current LSB of 1 mA/bit and a shunt resistor of 2 mΩ results in a Calibration register value of 2560, or A00h.
The Current register (04h) is then calculated by multiplying the decimal value of the Shunt Voltage register
contents by the decimal value of the Calibration register and then dividing by 2048, as shown in Equation 3. For
this example, the Shunt Voltage register contains a value of 8,000, which is multiplied by the Calibration register
value of 2560 and then divided by 2048 to yield a decimal value for the Current register of 10000, or 2710h.
Multiplying this value by 1 mA/bit results in the original 10-A level stated in the example.
Current =
ShuntVoltage · CalibrationRegister
2048
(3)
The LSB for the Bus Voltage register (02h) is a fixed 1.25 mV/bit. This fixed value means that the 11.98V present
at the BUS pin results in a register value of 2570h, or a decimal equivalent of 9584. Note that the MSB of the
Bus Voltage register is always zero because the BUS pin is only able to measure positive voltages.
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The Power register (03h) is then calculated by multiplying the decimal value of the Current register, 10000, by
the decimal value of the Bus Voltage register, 9584, and then dividing by 20,000, as defined in Equation 4. For
this example, the result for the Power register is 12B8h, or a decimal equivalent of 4792. Multiplying this result by
the power LSB (25 times the [1 × 10–3 Current_LSB]) results in a power calculation of (4792 × 25 mW/bit), or
119.8 W. The Power register LSB has a fixed ratio to the Current register LSB of 25 W/bit to 1 A/bit. For this
example, a programmed Current register LSB of 1 mA/bit results in a Power register LSB of 25 mW/bit. This ratio
is internally programmed to ensure that the scaling of the power calculation is within an acceptable range. A
manual calculation for the power being delivered to the load would use a bus voltage of 11.98 V (12VCM – 20 mV
shunt drop) multiplied by the load current of 10 A to give a result of 119.8 W.
Power =
Current · BusVoltage
20,000
(4)
Table 1 shows the steps for configuring, measuring, and calculating the values for current and power for this
device.
Table 1. Configure/Measure/Calculate Example (1)
(1)
STEP #
REGISTER NAME
ADDRESS
CONTENTS
DEC
LSB
Step 1
Configuration
00h
4127h
—
—
VALUE
—
Step 2
Shunt
01h
1F40h
8000
2.5 µV
20m V
Step 3
Bus
02h
2570h
9584
1.25 mV
11.98 V
Step 4
Calibration
05h
A00h
2560
—
—
Step 5
Current
04h
2710
10000
1 mA
10 A
Step 6
Power
03h
12B8h
4792
25 mW
119.8 W
Conditions: Load = 10 A, VCM = 12 V, RSHUNT = 2 mΩ, and VBUS =11.98 V.
PROGRAMMING THE INA230 POWER MEASUREMENT ENGINE
Calibration Register and Scaling
The Calibration register makes it possible to set the scaling of the Current and Power registers to the values that
are most useful for a given application. One strategy may be to set the Calibration register so that the largest
possible number is generated in the Current register or Power register at the expected full-scale point. This
approach yields the highest resolution based on the previously calculated minimum Current_LSB in the equation
for the Calibration register (Equation 1). The Calibration register can also be selected to provide values in the
Current and Power registers that either provide direct decimal equivalents of the values being measured, or yield
a round LSB value for each corresponding register. After these choices have been made, the Calibration register
also offers possibilities for end-user, system-level calibration. By physically measuring the current with an
external ammeter, the exact current is known. The value of the Calibration register can then be adjusted based
on the measured current result of the INA230 to cancel the total system error, as shown in Equation 5.
Corrected_Full_Scale_Cal = trunc
Cal ´ MeasShuntCurrent
INA230_Current
(5)
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Simple Current Shunt Monitor Usage
(No Programming Necessary)
The INA230 can be used without any programming if it is only necessary to read a shunt voltage drop and bus
voltage with the default power-on reset configuration and continuous conversion of shunt and bus voltage.
Without programming the INA230 Calibration register, the device is unable to provide either a valid current or
power value, because these outputs are both derived using the values loaded into the Calibration register.
Default INA230 Settings
The default power-up states of the registers are shown in the INA230 Register Descriptions section of this data
sheet. These registers are volatile, and if programmed to a value other than the default values shown in Table 2,
they must be reprogrammed at every device power-up. Detailed information on programming the Calibration
register is given in the Configure/Measure/Calculate Example section and calculated based on Equation 1.
REGISTER INFORMATION
The INA230 uses a bank of registers for holding configuration settings, measurement results, minimum/maximum
limits, and status information. Table 2 summarizes the INA230 registers; refer to Figure 1 for an illustration of the
registers.
Table 2. Summary of Register Set
POINTER
ADDRESS
(1)
(2)
18
POWER-ON RESET
HEX
REGISTER NAME
FUNCTION
BINARY
HEX
TYPE (1)
00
Configuration
All-register reset, shunt voltage and bus
voltage ADC conversion times and
averaging, operating mode
01000001 00100111
4127
R/W
01
Shunt Voltage
Shunt voltage measurement data
00000000 00000000
0000
R
02
Bus Voltage
Bus voltage measurement data
00000000 00000000
0000
R
Contains the value of the calculated
power being delivered to the load.
00000000 00000000
0000
R
(2)
03
Power
04
Current (2)
Contains the value of the calculated
current flowing through the shunt
resistor.
00000000 00000000
0000
R
05
Calibration
Sets full-scale range and LSB of current
and power measurements. Overall
system calibration.
00000000 00000000
0000
R/W
06
Mask/Enable
Alert configuration and conversion ready
flag
00000000 00000000
0000
R/W
07
Alert Limit
Contains the limit value to compare to
the selected alert function.
00000000 00000000
0000
R/W
FF
Die ID
ASCII
ASCII
R
Contains unique die identification
number.
Type: R = read-only, R/W = read/write.
The Current register defaults to '0' because the Calibration register defaults to '0', yielding a zero current and power value until the
Calibration register is programmed.
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REGISTER DETAILS
All 16-bit INA230 registers are two 8-bit bytes via the I2C interface.
Configuration Register (00h, Read/Write)
BIT #
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
BIT
NAME
RST
—
—
—
AVG2
AVG1
AVG0
VBUSCT2
VBUSCT1
VBUSCT0
VSHCT2
VSHCT1
VSHCT0
MODE3
MODE2
MODE1
POR
VALUE
0
1
0
0
0
0
0
1
0
0
1
0
0
1
1
1
The Configuration register settings control the operating modes for the INA230. This register controls the
conversion time settings for both the shunt and bus voltage measurements, as well as the averaging mode used.
The operating mode that controls which signals are selected to be measured is also programmed in the
Configuration register.
The Configuration register can be read from at any time without impacting or affecting the device settings or a
conversion in progress. Writing to the Configuration register halts any conversion in progress until the write
sequence is complete, resulting in the start of a new conversion based on the new contents of the Configuration
register. This feature prevents any uncertainty in the conditions used for the next completed conversion.
Bit Descriptions
RST:
Reset Bit
Bit 15
Setting this bit to '1' generates a system reset that is the same as a power-on reset; all registers are reset to default
values. This bit self-clears.
AVG:
Averaging Mode
Bits 9–11
Sets the number of samples that are collected and averaged together. Table 3 summarizes the AVG bit settings
and related number of averages for each bit.
Table 3. AVG Bit Settings [11:9] (1)
(1)
AVG2
(D11)
AVG1
(D10)
AVG0
(D9)
NUMBER OF
AVERAGES
0
0
0
1
0
0
1
4
0
1
0
16
0
1
1
64
1
0
0
128
1
0
1
256
1
1
0
512
1
1
1
1024
Shaded values are default.
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VBUS CT:
Bus Voltage Conversion Time
Bits 6–8
Sets the conversion time for the bus voltage measurement. Table 4 shows the VBUS CT bit options and related
conversion times for each bit.
Table 4. VBUS CT Bit Settings [8:6] (1)
(1)
VBUS CT2
(D8)
VBUS CT1
(D7)
VBUS CT0
(D6)
CONVERSION TIME
0
0
0
140 µs
0
0
1
204 µs
0
1
0
332 µs
0
1
1
588 µs
1
0
0
1.1 ms
1
0
1
2.116 ms
1
1
0
4.156 ms
1
1
1
8.244 ms
Shaded values are default.
VSH CT:
Shunt Voltage Conversion Time
Bits 3–5
Sets the conversion time for the shunt voltage measurement. Table 5 shows the VSH CT bit options and related
conversion times for each bit.
Table 5. VSH CT Bit Settings [5:3] (1)
(1)
VSH CT2
(D5)
VSH CT1
(D4)
VSH CT0
(D3)
CONVERSION TIME
0
0
0
140 µs
0
0
1
204 µs
0
1
0
332 µs
0
1
1
588 µs
1
0
0
1.1 ms
1
0
1
2.116 ms
1
1
0
4.156 ms
1
1
1
8.244 ms
Shaded values are default.
MODE:
Operating Mode
Bits 0–2
Selects continuous, triggered, or power-down mode of operation. These bits default to continuous shunt and bus
measurement mode. The mode settings are shown in Table 6.
Table 6. Mode Settings [2:0] (1)
(1)
20
MODE3
(D2)
MODE2
(D1)
MODE1
(D0)
MODE
0
0
0
Power-Down
0
0
1
Shunt Voltage, triggered
0
1
0
Bus Voltage, triggered
0
1
1
Shunt and Bus, triggered
1
0
0
Power-Down
1
0
1
Shunt Voltage, continuous
1
1
0
Bus Voltage, continuous
1
1
1
Shunt and Bus, continuous
Shaded values are default.
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DATA OUTPUT REGISTERS
Shunt Voltage Register (01h, Read-Only)
The Shunt Voltage register stores the current shunt voltage reading, VSHUNT. Negative numbers are represented
in twos complement format. Generate the twos complement of a negative number by complementing the
absolute value binary number and adding 1. Extend the sign, denoting a negative number by setting the MSB =
'1'.
Example: For a value of VSHUNT = –80 mV:
1. Take the absolute value: 80mV
2. Translate this number to a whole decimal number (80 mV ÷ 2.5 µV) = 32000
3. Convert this number to binary = 111 1101 0000 0000
4. Complement the binary result = 000 0010 1111 1111
5. Add '1' to the complement to create the twos complement result = 000 0011 0000 0000
6. Extend the sign and create the 16-bit word: 1000 0011 0000 0000 = 8300h
If averaging is enabled, this register displays the averaged value. Full-scale range = 81.9175 mV (decimal =
7FFF); LSB: 2.5 μV.
BIT #
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
BIT
NAME
SIGN
SD14
SD13
SD12
SD11
SD10
SD9
SD8
SD7
SD6
SD5
SD4
SD3
SD2
SD1
SD0
POR
VALUE
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Bus Voltage Register (02h, Read-Only) (1)
The Bus Voltage register stores the most recent bus voltage reading, VBUS.
If averaging is enabled, this register displays the averaged value. Full-scale range = 40.95875 V (decimal =
7FFF); LSB = 1.25 mV. Do not apply more than 28 V on the BUS pin.
BIT #
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
BIT
NAME
—
BD14
BD13
BD12
BD11
BD10
BD9
BD8
BD7
BD6
BD5
BD4
BD3
BD2
BD1
BD0
POR
VALUE
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
(1)
D15 is always zero because bus voltage can only be positive.
Power Register (03h, Read-Only)
If averaging is enabled, this register displays the averaged value.
BIT #
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
BIT
NAME
PD15
PD14
PD13
PD12
PD11
PD10
PD9
PD8
PD7
PD6
PD5
PD4
PD3
PD2
PD1
PD0
POR
VALUE
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
The Power register LSB is internally programmed to equal 25 times the programmed value of the Current_LSB.
The Power register records power in watts by multiplying the decimal values of the current register with the
decimal value of the bus voltage register according to Equation 4.
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Current Register (04h, Read-Only)
If averaging is enabled, this register displays the averaged value.
BIT #
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
BIT
NAME
CSIGN
CD14
CD13
CD12
CD11
CD10
CD9
CD8
CD7
CD6
CD5
CD4
CD3
CD2
CD1
CD0
POR
VALUE
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
The value of the Current register is calculated by multiplying the decimal value in the Shunt Voltage register with
the decimal value of the Calibration register, according to Equation 3.
Calibration Register (05h, Read/Write)
This register provides the INA230 with the shunt resistor value that was present to create the measured
differential voltage. This register also sets the resolution of the Current register. The Current register LSB and
Power register LSB are set through the programming of this register. This register is also used for overall system
calibration. See the Configure/Measure/Calculate Example for more information on programming this register.
BIT #
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
BIT
NAME
—
FS14
FS13
FS12
FS11
FS10
FS9
FS8
FS7
FS6
FS5
FS4
FS3
FS2
FS1
FS0
POR
VALUE
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Mask/Enable Register (06h, Read/Write)
The Mask/Enable register selects the function that controls the ALERT pin, as well as how that pin functions. If
multiple functions are enabled, the highest significant bit position alert function (D15:D11) takes priority and
responds to the Alert Limit register.
BIT #
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
BIT
NAME
SOL
SUL
BOL
BUL
POL
CNVR
—
—
—
—
—
AFF
CVRF
OVF
APOL
LEN
POR
VALUE
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
SOL:
Shunt Voltage Over-Voltage
Bit 15
Setting this bit high configures the ALERT pin to be asserted when the shunt voltage conversion exceeds the value
in the Alert Limit register.
SUL:
Shunt Voltage Under-Voltage
Bit 14
Setting this bit high configures the ALERT pin to be asserted when the shunt voltage conversion drops below the
value in the Alert Limit register.
BOL:
Bus Voltage Over-Voltage
Bit 13
Setting this bit high configures the ALERT pin to be asserted when the bus voltage conversion exceeds the value in
the Alert Limit register.
BUL:
Bus Voltage Under-Voltage
Bit 12
Setting this bit high configures the ALERT pin to be asserted when the bus voltage conversion drops below the
value in the Alert Limit register.
POL:
Over-Limit Power
Bit 11
Setting this bit high configures the ALERT pin to be asserted when the power calculation exceeds the value in the
Alert Limit register.
CNVR:
Conversion Ready
Bit 10
Setting this bit high configures the ALERT pin to be asserted when the Conversion Ready Flag bit (CVRF, bit 3) is
asserted, indicating that the device is ready for the next conversion.
22
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AFF:
Alert Function Flag
Bit 4
Although only one alert function at a time can be monitored at the ALERT pin, the Conversion Ready bit (CNVR, bit
10) can also be enabled to assert the ALERT pin. Reading the Alert Function Flag bit after an alert can help
determine if the alert function was the source of the alert.
When the Alert Latch Enable bit is set to Latch mode, the Alert Function Flag bit clears only when the Mask/Enable
register is read. When the Alert Latch Enable bit is set to Transparent mode, the Alert Function Flag bit is cleared
after the next conversion that does not result in an alert condition.
CVRF:
Conversion Ready Flag
Bit 3
Although the INA230 can be read at any time, and the data from the last conversion are available, this bit is
provided to help coordinate single-shot or triggered conversions. This bit is set after all conversions, averaging, and
multiplications are complete. This bit clears under the following conditions in single-shot mode:
1) Writing to the Configuration register (except for power-down or disable selections)
2.) Reading the Mask/Enable register
OVF:
Math Overflow Flag
Bit 2
This bit is set to '1' if an arithmetic operation results in an overflow error; it indicates that current and power data
may be invalid.
APOL:
Alert Polarity
Bit 1
Configures the latching feature of the ALERT pin and the flag bits.
1 = Inverted (active-high open collector)
0 = Normal (active-low open collector) (default)
LEN:
Alert Latch Enable
Bit 0
Configures the latching feature of the ALERT pin and flag bits.
1 = Latch enabled
0 = Transparent (default)
When the Alert Latch Enable bit is set to Transparent mode, the ALERT pin and flag bits reset to their idle states
when the fault has been cleared. When the Alert Latch Enable bit is set to Latch mode, the ALERT pin and flag bits
remain active following a fault until the Mask/Enable register has been read.
Alert Limit Register (07h, Read/Write)
The Alert Limit register contains the value used to compare to the register selected in the Mask/Enable register
to determine if a limit has been exceeded.
BIT #
D15
D14
D13
D12
D11
D10
D9
D8
D7
D6
D5
D4
D3
D2
D1
D0
BIT
NAME
AUL15
AUL14
AUL13
AUL12
AUL11
AUL10
AUL9
AUL8
AUL7
AUL6
AUL5
AUL4
AUL3
AUL2
AUL1
AUL0
POR
VALUE
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
BUS OVERVIEW
The INA230 offers compatibility with both I2C and SMBus interfaces. The I2C and SMBus protocols are
essentially compatible with one another.
The I2C interface is used throughout this data sheet as the primary example, with SMBus protocol specified only
when a difference between the two systems is discussed. Two bidirectional lines, SCL and SDA, connect the
INA230 to the bus. Both SCL and SDA are open-drain connections.
The device that initiates a data transfer is called a master, and the devices controlled by the master are slaves.
The bus must be controlled by a master device that generates the serial clock (SCL), controls the bus access,
and generates start and stop conditions.
To address a specific device, the master initiates a start condition by pulling the data signal line (SDA) from a
high to a low logic level while SCL is high. All slaves on the bus shift in the slave address byte on the rising edge
of SCL, with the last bit indicating whether a read or write operation is intended. During the ninth clock pulse, the
slave being addressed responds to the master by generating an Acknowledge bit (ACK) and pulling SDA low.
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Data transfer is then initiated and eight bits of data are sent, followed by an ACK. During data transfer, SDA must
remain stable while SCL is high. Any change in SDA while SCL is high is interpreted as a start or stop condition.
Once all data have been transferred, the master generates a stop condition, indicated by pulling SDA from low to
high while SCL is high. The INA230 includes a 28-ms timeout on its interface to prevent locking up the bus.
Serial Bus Address
To communicate with the INA230, the master must first address slave devices using a corresponding slave
address byte. The slave address byte consists of seven address bits and a direction bit that indicates whether
the action is to be a read or write operation.
The INA230 has two address pins: A0 and A1. Table 7 describes the pin logic levels for each of the 16 possible
addresses. The state of pins A0 and A1 is sampled on every bus communication and should be set before any
activity on the interface occurs.
Table 7. INA230 Address Pins and
Slave Addresses
A1
A0
SLAVE ADDRESS
GND
GND
1000000
GND
VS
1000001
GND
SDA
1000010
GND
SCL
1000011
VS
GND
1000100
VS
VS
1000101
VS
SDA
1000110
VS
SCL
1000111
SDA
GND
1001000
SDA
VS
1001001
SDA
SDA
1001010
SDA
SCL
1001011
SCL
GND
1001100
SCL
VS
1001101
SCL
SDA
1001110
SCL
SCL
1001111
Serial Interface
The INA230 operates only as a slave device on both the I2C bus and the SMBus. Connections to the bus are
made through the open-drain I/O lines, SDA and SCL. The SDA and SCL pins feature integrated
spike-suppression filters and Schmitt triggers to minimize the effects of input spikes and bus noise. Although
there is spike suppression integrated into the digital I/O lines, proper layout should be used to minimize the
amount of coupling into the communication lines. This noise introduction could occur from capacitively coupling
signal edges between the two communication lines themselves or from other switching noise sources present in
the system. Routing traces in parallel with ground in between layers on a printed circuit board (PCB) typically
reduces the effects of coupling between the communication lines. Shielding communication lines in general is
recommended to reduce to possibility of unintended noise coupling into the digital I/O lines that could be
incorrectly interpreted as start or stop commands.
The INA230 supports the transmission protocol for Fast (1 kHz to 400 kHz) and High-speed (1 kHz to 3.4 MHz)
modes. All data bytes are transmitted most significant byte first.
24
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WRITING TO/READING FROM THE INA230
Accessing a specific register on the INA230 is accomplished by writing the appropriate value to the register
pointer. Refer to Table 2 for a complete list of registers and corresponding addresses. The value for the register
pointer (shown in Figure 27) is the first byte transferred after the slave address byte with the R/W bit low. Every
write operation to the INA230 requires a value for the register pointer.
Writing to a register begins with the first byte transmitted by the master. This byte is the slave address, with the
R/W bit low. The INA230 then acknowledges receipt of a valid address. The next byte transmitted by the master
is the address of the register that data will be written to. This register address value updates the register pointer
to the desired register. The next two bytes are written to the register addressed by the register pointer. The
INA230 acknowledges receipt of each data byte. The master may terminate data transfer by generating a start or
stop condition.
When reading from the INA230, the last value stored in the register pointer by a write operation determines
which register is read during a read operation. To change the register pointer for a read operation, a new value
must be written to the register pointer. This write is accomplished by issuing a slave address byte with the R/W
bit low, followed by the register pointer byte. No additional data are required. The master then generates a start
condition and sends the slave address byte with the R/W bit high to initiate the read command. The next byte is
transmitted by the slave and is the most significant byte of the register indicated by the register pointer. This byte
is followed by an ACK from the master; then the slave transmits the least significant byte. The master
acknowledges receipt of the data byte. The master may terminate data transfer by generating a
Not-Acknowledge bit (No ACK) after receiving any data byte, or generating a start or stop condition. If repeated
reads from the same register are desired, it is not necessary to continually send the register pointer bytes; the
INA230 retains the register pointer value until it is changed by the next write operation.
Figure 24 and Figure 25 show the write and read operation timing diagrams, respectively. Note that register
bytes are sent most-significant byte first, followed by the least significant byte.
1
9
9
1
9
1
9
1
SCL
SDA
1
0
0
A3
A2
A1
A0
R/W
Start By
Master
Frame 1 Two-Wire Slave Address Byte
(1)
P7
P6
P5
P4
P3
P2
P1
ACK By
INA230
P0
D15 D14
D13
D12 D11 D10
D9
D8
(1)
D7
D6
D5
D4
D3
D2
D1
D0
ACK By
INA230
ACK By
INA230
Frame 2 Register Pointer Byte
ACK By
INA230
Frame 3 Data MSByte
Stop By
Master
Frame 4 Data LSByte
The value of the slave address byte is determined by the settings of the A0 and A1 pins. Refer to Table 7.
Figure 24. Timing Diagram for Write Word Format
1
9
1
9
1
9
SCL
SDA
1
0
0
A3
A2
A1
A0
R/W
Start By
Master
D15 D14
ACK By
INA230
Frame 1 Two-Wire Slave Address Byte
(1)
D13
D12
D11 D10
D9
D8
From
INA230
Frame 2 Data MSByte
D7
D6
D5
D4
D3
D2
D1
From
INA230
ACK By
Master
(2)
Frame 3 Data LSByte
D0
No ACK By
Master
(3)
Stop
(2)
(1)
The value of the slave address byte is determined by the settings of the A0 and A1 pins. Refer to Table 7.
(2)
Read data are from the last register pointer location. If a new register is desired, the register pointer must be updated.
See Figure 27.
(3)
ACK by Master can also be sent.
Figure 25. Timing Diagram for Read Word Format
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Figure 26 shows the timing diagram for the SMBus alert response operation. Figure 27 illustrates a typical
register pointer configuration.
ALERT
1
9
1
9
SCL
SDA
0
0
0
1
1
0
0
R/W
Start By
Master
1
0
0
A2
ACK By
INA230
A1
A0
0
From
INA230
Frame 1 SMBus ALERT Response Address Byte
(1)
A3
Frame 2 Slave Address Byte
NACK By
Master
Stop By
Master
(1)
The value of the slave address byte is determined by the settings of the A0 and A1 pins. Refer to Table 7.
Figure 26. Timing Diagram for SMBus Alert
1
9
1
9
SCL
¼
SDA
1
0
0
A3
A2
A1
A0
R/W
Start By
Master
P6
P5
P4
P3
P2
P1
ACK By
INA230
Frame 1 Two-Wire Slave Address Byte
(1)
P7
(1)
P0
Stop
ACK By
INA230
Frame 2 Register Pointer Byte
The value of the slave address byte is determined by the settings of the A0 and A1 pins. Refer to Table 7.
Figure 27. Typical Register Pointer Set
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High-Speed I2C Mode
When the bus is idle, both the SDA and SCL lines are pulled high by the pull-up devices. The master generates
a start condition followed by a valid serial byte containing High-Speed (HS) master code 00001XXX. This
transmission is made in fast (400 kHz) or standard (100 kHz) (F/S) mode at no more than 400 kHz. The INA230
does not acknowledge the HS master code, but does recognize it and switches its internal filters to support
3.4-MHz operation.
The master then generates a repeated start condition (a repeated start condition has the same timing as the start
condition). After this repeated start condition, the protocol is the same as F/S mode, except that transmission
speeds up to 3.4 MHz are allowed. Instead of using a stop condition, repeated start conditions should be used to
secure the bus in HS-mode. A stop condition ends the HS-mode and switches all the internal filters of the
INA230 to support the F/S mode.
t(LOW)
tF
tR
t(HDSTA)
SCL
t(HDSTA)
t(HIGH)
t(SUSTO)
t(SUSTA)
t(HDDAT)
t(SUDAT)
SDA
t(BUF)
P
S
S
P
Figure 28. Bus Timing Diagram
Bus Timing Diagram Definitions
FAST MODE
PARAMETER
HIGH-SPEED MODE
MIN
MAX
MIN
MAX
UNITS
SCL operating frequency
f(SCL)
0.001
0.4
0.001
3.4
MHz
Bus free time between stop and start
conditions
t(BUF)
600
160
ns
Hold time after repeated START condition.
After this period, the first clock is generated.
t(HDSTA)
100
100
ns
Repeated start condition setup time
t(SUSTA)
100
100
ns
STOP condition setup time
t(SUSTO)
100
100
ns
Data hold time
t(HDDAT)
0
0
ns
Data setup time
t(SUDAT)
100
10
ns
SCL clock low period
t(LOW)
1300
160
ns
SCL clock high period
t(HIGH)
600
60
Clock/data fall time
tF
Clock/data rise time
Clock/data rise time for SCLK ≤ 100 kHz
ns
300
160
ns
tR
300
160
ns
tR
1000
ns
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SMBus Alert Response
The INA230 is designed to respond to the SMBus alert response address. The SMBus alert response provides a
quick fault identification for simple slave devices. When an alert occurs, the master can broadcast the alert
response slave address (0001 100) with the Read/Write bit set high. Following this alert response, any slave
devices that generated an alert identify themselves by acknowledging the alert response and sending their
respective address on the bus.
The alert response can activate several different slave devices simultaneously, similar to the I2C general call. If
more than one slave attempts to respond, bus arbitration rules apply. The losing device does not generate an
acknowledge and continues to hold the ALERT line low until the interrupt is cleared.
28
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PACKAGE OPTION ADDENDUM
www.ti.com
2-Mar-2012
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package
Drawing
Pins
Package Qty
Eco Plan
(2)
Lead/
Ball Finish
MSL Peak Temp
(3)
INA230AIRGTR
ACTIVE
QFN
RGT
16
3000
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
INA230AIRGTT
ACTIVE
QFN
RGT
16
250
Green (RoHS
& no Sb/Br)
CU NIPDAU Level-2-260C-1 YEAR
Samples
(Requires Login)
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability
information and additional product content details.
TBD: The Pb-Free/Green conversion plan has not been defined.
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that
lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between
the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above.
Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight
in homogeneous material)
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information
provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and
continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals.
TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI to Customer on an annual basis.
Addendum-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
4-May-2012
TAPE AND REEL INFORMATION
*All dimensions are nominal
Device
Package Package Pins
Type Drawing
SPQ
Reel
Reel
A0
Diameter Width (mm)
(mm) W1 (mm)
B0
(mm)
K0
(mm)
P1
(mm)
W
Pin1
(mm) Quadrant
INA230AIRGTR
QFN
RGT
16
3000
330.0
12.4
3.3
3.3
1.1
8.0
12.0
Q2
INA230AIRGTT
QFN
RGT
16
250
180.0
12.4
3.3
3.3
1.1
8.0
12.0
Q2
Pack Materials-Page 1
PACKAGE MATERIALS INFORMATION
www.ti.com
4-May-2012
*All dimensions are nominal
Device
Package Type
Package Drawing
Pins
SPQ
Length (mm)
Width (mm)
Height (mm)
INA230AIRGTR
QFN
RGT
16
3000
346.0
346.0
29.0
INA230AIRGTT
QFN
RGT
16
250
210.0
185.0
35.0
Pack Materials-Page 2
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