1. INA240 High-voltage, enhanced PWM rejection current sense amplifier for large common-mode transients
Thank you, Matt. Great summary of the C2000’s performance capabilities. Now let’s talk about current sensing with a particular focus on the new INA240 product from TI.

2. Benefits of designing with current sense amplifiers
Discrete current sensing
Dedicated current sense amplifier
Op amp used for current sensing
External gain setting resistors
Input range limited by supply voltage
Current sensing has been in existence since the introduction of the standard op amp. A simple single-ended discrete implementation as shown in the left-hand side of the screen is very standard for a low-side current measurement. There may be many reasons for implementing a design as shown but some of the most common are legacy, cost perception and awareness. Most designers use their favorite op amp that they’ve used for many years and re-use it from one design to another. Another reason that is on top of all designers’ minds is cost. The perception in the industry is that a low-cost op amp with external gain resistors is the lowest cost solution. In general, this may be true but TI has new products that challenge this perception. The other major reason for implementing a discrete solution is simply awareness. Many designers don’t know there’s a better way to measure current effectively.
One drawback to implementing a solution discretely is board space due to the op amp and the external gain resistors. It’s physically smaller to use a current sense amplifier. Another drawback is the input voltage range is limited to the supply voltage. Because of this many implementations are limited to low-side current sensing, which means current is measured only between the load and ground.
TI’s current sense amplifiers offer many benefits; let me highlight a few of them here. First, you benefit from an integrated precision matched gain resistor network. Trying to equal the level of resistor matching on a PCB is not cost-effective. The second benefit leverages TI’s Zero-drift technology allowing very stable measurements over temperature. Another benefit is the capability to use the smallest shunt resistor possible to measure current due to low input offset voltage specifications of most current sense amplifiers. This allows for the smallest power dissipation possible without compromising on measurement accuracy. The last benefit I want to mention is the capability to monitor currents with a much wider input common-mode voltage range which is independent of the device supply.
Texas Instruments offers a wide variety of analog and digital current sense amplifiers for all types of applications, but now let’s focus on the new INA240 specifically designed for fast PWM transients.

3. Large, high slew rate input VCM
INA240 Family
High-voltage, enhanced PWM rejection current sense amplifier for large common-mode transients
Features
Benefits
Wide common-mode : -4V to 80V
Bi-directional
High AC CMRR: 50kHz
Enhanced PWM rejection
High accuracy
Input offset voltage: 25µV (Max) with 0.25µV/°C Max Drift
Gain error: ±0.20% (Max) with 2.5ppm/°C Max Drift
Available gains: 20, 50, 100, 200V/V
Package: TSSOP-8
AEC Q100 Option available in 1Q17
Large input range to integrate into increasing common-mode voltage applications
High accuracy minimizes system margins
High CMRR allows for direct in-line motor current sensing
Ex: In-line Motor Current Sensing
Ex: High-side DC-DC Current Sensing
VOUT
VCM
Applications
Motor control • Power supplies
Solenoid/valve Control
VCM
VOUT
Tools & Resources
Large, high slew rate input VCM
INA240EVM gain options:
20V/V, 50V/V, 100V/V, 200V/V
INA240EVM User’s Guide
TINA-SPICE Model
TIDA GaN half-bridge with in-line motor current sensing using INA240
Stable VOUT!
The INA240 is TI’s latest current sense amplifier with enhanced PWM rejection, which allows for operation in environments that may experience large common-mode voltage transients at a very fast slew rate. Testing in our lab has shown that even under extreme cases (such as 80V common mode and 10V/ns) the device behaves very well. Not so for competitive solutions that claim to work under these harsh conditions. The INA240 has a wide -4V to 80V common-mode input voltage range allowing for high-side current measurement and also to be used in solenoid applications that require a negative common-mode voltage due to the inductive kick-back during flyback. What’s equally impressive is the high accuracy. With an input offset voltage of 25µV (max), 0.25µV/°C max drift, a gain error of ±0.20% (max) and 2.5ppm/°C max drift, the INA240 promises to be the best in its class.
We offer this device in 4 gain options and is available in an 8-pin TSSOP with a temperature range of -40°C to 125°C. An EVM and a TI reference design is also readily available, but we’ll talk more about this in subsequent slides. 3

4. Enhanced PWM Rejection
What is it?
Active circuitry which monitors the input common-mode signals.
If a fast transition is detected, will suppress the signal to minimize the “glitch” to be propagated through the device’s output.
How do other solutions tackle this problem?
Competitive solutions typically utilize high-bandwidth amplifiers to settle the output as quickly as possible.
Problem with this approach is it may incur added delay due to the settling time.
VCM
VOUT
What system-level benefit is there with Enhanced PWM Rejection?
“Blanking time” is reduced substantially!
Can measure accurately at lower duty cycles!
So, you may ask, “Why is enhanced PWM rejection important for me?” I’ll answer this in a bit but first let’s talk about what it is and how other solutions address fast PWM rates. Enhanced PWM rejection is active circuitry which monitors the input common-mode signals. Fast transients trigger circuitry to suppress the signal as it traverses through the device and ultimately manifests itself at the output in the form of an unwanted glitch. The waveform shown in the upper right-hand corner shows a relatively large common-mode voltage swing of 24V with an edge rate of 10ns/V. Most current sense amplifiers (including competitive solutions) do not handle this well and produce a large glitch at the output or overshoot/undershoot transitions (also known as “ringing”) or both. The INA240, as is clearly shown, quickly settles on the desired output voltage.
Competitive solutions typically make use of high-bandwidth amplifiers only to settle the output as quickly as possible. This approach does help but still does not reduce the settling time as quickly and often times is an expensive proposition.
I’ll lightly touch on the benefit of using the INA240 with enhanced PWM rejection, but the main advantage is a greatly reduced “blanking time”. At lower duty cycles this is very important.

5. Why is in-line motor sensing important?
Why measure current in a motor?
Fault protection
Input into motor control algorithm
Why measure current in-line vs. low-side?
Low-side is a proven approach with a large customer base
and perceived to have a lower system cost, but has difficulty
to scaling to higher precision and lower drift
Low-side creates a non-linear output signal that must be
post-processed to extract the proportional base current information
In-line provides a faster response, higher precision, and the ability to have less drift over a wide temperature range
In-line reproduces a continuous proportional signal of the phase current which does not need further processing
Let’s focus our attention on the main reason the INA240 was developed – in-line motor current sensing. Current that is fed into the motor must be measured and monitored at all times. The first, and arguably most important, reason is fault detection. A stalled motor can produce large amounts of current and can lead to a catastrophic failure of the motor. An early alert provided by a current sensing amplifier allows the processor to shut the system down before this happens. System designers also monitor the current as a feedback mechanism into the processor keeping the motor running as efficiently as possible and for general health of the motor.
There are several ways to measure current in 3-phase DC motors. By far the most popular method is a low-side approach, which measures current at two or all of the three phase currents. The low-side configuration, which is not shown in the graphic, measures current between the power MOSFETs FET2, FET4, or FET6 and ground. If only two currents are measured then the third one is calculated. Many designers use this method because standard current-sensing solutions are readily available – typically with fast response times, higher bandwidths, fast output slew rates and low common-mode input voltages. But just because products are available that can sense phase current via low-side doesn’t mean that these solutions represent the easiest way since non-linear output signals are generated. There is a lot of post-processing involved to try to replicate the current being driven into the motor windings. This replication effort occurs in software, and it can be quite involved and never truly matches the current at each phase.
The in-line current sensing method (as shown in the graphic) is the most logical because that is the current you are ultimately trying to measure. As mentioned already, though, the main challenge is the large and fast PWM voltages. These PWM signals driving the MOSFETs (or IGBTs) wreak havoc on current-sense amplifiers. The common-mode signals at the sense resistor are driven from the supply voltage to ground with very fast transient switching characteristics, while the current-sense amplifier is trying to measure a small differential signal across the sense resistor itself. Luckily, we have now the INA240 that can do the job. In-line provides a faster response, higher precision, and the ability to have less drift over a wide temperature range. It also reproduces a continuous proportional signal of the phase current which does not need further processing. A huge benefit for system designers using the C2000 high-performance MCUs.

6. TI solutions for 3-phase DC Motor Control
Current meas. options in 3-phase DC motor
TI 3-phase DC motor current measurement solutions
In-line Phase Current
Device
VCM Range
VOS
VOS Drift
Gain
Gain Error
Gain Error Drift
Comment
INA240
–4V to +80V
25µV
0.25µV/°C
20, 50, 100, 200
0.2%
2.5ppm/°C
Enhanced PWM Rejection
Low-side Phase Current
INA303
0V to +36V
35µV
0.1µV/°C
20, 50, 100
0.10%
10ppm/°C
Integrated Window Comparator
High-side Motor Current Monitoring for Over-Current Protection
Ultra-high Precision
LMP8640HV
–2V to +76V
900µV
2.6µV/°C
0.25%
26.2ppm/°C
High Bandwidth
INA200
–16V to +80V
2.5mV
5µV/°C (typ) 1% -
Over-current
Low-side Motor Current Monitoring for Over-Current Protection
INA199
–0.3V to +26V
150µV
50, 100, 200
1.40%
Low-cost Current Sense Amplifier
INA301
Integrated Fast Comparator
For completeness, the graphic on the left-hand side shows all the different shunt-based current-sensing methods implemented by motor designers. Of course, not all methods will be used in a production environment but system designers typically use various combinations of them. As you can see not only is in-line and low-side current sensing shown, but it also shows high-side and low-side DC link, which is the dark blue current sense amplifier. High-side current sensing is typically used for gross fault conditions such as a short to ground, while low-side DC link is also requires much post-processing.
The table on the right provides a listing of key products TI recommends for motor current sensing for each of the current sensing methods. Due to the high common-mode voltage and its awesome features and specs, the INA240 is the “go-to” solution for in-line phase or high-side. Notice, once again, the stellar accuracy specifications on the INA240. For low-side phase current the INA303 is a great solution as it not only has very good accuracy specs, but it has a built-in window comparator function that sends an ALERT warning the current level has gone below or above an expected value. This threshold value can be set with a single external resistor.

7. TI solutions for 3-phase DC motor control
Current Meas. options in 3-phase DC Motor
TI 3-phase DC Motor Current Measurement Solutions
System benefits gained from using INA240
Most accurate phase current representation with in-line phase current sensing
Algorithm optimization
Reduced blanking time
Possible elimination of galvanic isolation
Increased motor efficiency
In-line Phase Current
Device
VCM Range
VOS
VOS Drift
Gain
Gain Error
Gain Error Drift
Comment
INA240
–4V to +80V
25µV
0.25µV/°C
20, 50, 100, 200
0.2%
2.5ppm/°C
Enhanced PWM Rejection
Low-side Phase Current
INA303
0V to +36V
35µV
0.1µV/°C
20, 50, 100
0.10%
10ppm/°C
Integrated Window Comparator
High-side Motor Current Monitoring for Over-Current Protection
Ultra-high Precision
LMP8640HV
–2V to +76V
900µV
2.6µV/°C
0.25%
26.2ppm/°C
High Bandwidth
INA200
–16V to +80V
2.5mV
5µV/°C (typ) 1% -
Over-current
Low-side Motor Current Monitoring for Over-Current Protection
INA199
–0.3V to +26V
150µV
50, 100, 200
1.40%
Low-cost Current Sense Amplifier
INA301
Integrated Fast Comparator
To summarize the system benefits in a 3-phase DC motor control application realized when using the new INA240, here are just a few key ones:
Coupled with a high common-mode input voltage, enhanced PWM rejection allows for the ability to monitor current in line. As discussed previously, the robustness of the current-sense amplifier is a necessity due to the harsh environment to which it’s exposed. Aside from this requirement, the amplifier must also have high AC and DC accuracy to provide system designers precise current sensor measurements.
This benefit goes hand-in-hand with algorithm optimization. With enhanced PWM rejection, the need to replicate or calculate the phase current is no longer an issue because the answer is already provided directly. Only pertinent software is required to run the motor efficiently.
As mentioned previously, common-mode PWM transient suppression allows for less “ringing” at the output of the current-sense amplifier. The GaN power stage, which produces a very fast edge rate, is not a problem for the INA240. Having to wait for the voltage signal to settle is a major drawback, especially for systems that require low duty cycles (≤10%) because the time available to take the current measurement is shortened. Reduced blanking time gives the designers using the C2000 MCU more flexibility in their end product.
Another benefit provided by the INA240 is subtle but important. With enhanced PWM rejection, designers may be able to eliminate the use of an isolated current-sensing device when galvanic isolation is not part of the system requirements. Customers often use isolated devices to decouple the noise generated as the PWM signals travel through the sense resistor, and not necessarily because a specific isolation specification was required. This decoupling is no longer needed with enhanced PWM rejection.
Finally, I get to last benefit, which arguably matters most to designers – increased motor efficiency. Motor manufacturers and motor-drive system designers are always looking for ways to improve efficiency in the motor. High AC and DC accuracy, fast output response and reduced blanking time enable motor operation at the highest efficiency possible. Precise timing control of the multiphase motor reduces the blanking time as much as possible, which in turn maximizes motor efficiency.
Next, let’s take a look at a power supply such as an embedded DC-DC application.

8. TI solutions for embedded DC-DC power
Current measurement in Embedded DC-DC
TI Solutions for Embedded DC-DC
High-side Current Sensing (system power)
Device
VCM Range
VOS
VOS Drift
Gain
Gain Error
Gain Error Drift
Comment
INA240
-4V to +80V
25µV
0.25µV/°C
20, 50, 100, 200
0.2%
2.5ppm/°C
Ultra-high Precision
INA210
-0.3V to +26V
35µV
60µV
100µV
0.1µV/°C
50, 75, 100,
200, 500
0.9%
10ppm/°C
High
Performance
INA301
0V to +36V
20, 50, 100
0.10%
Fast Comparator
INA302
Over/Under Current
High-side Current Sensing (phase power)
PWM Rejection
LMP8645
-2V to +42V
1000µV
7µV/°C
Adjustable 2%
140ppm/°C
Bandwidth
Low-side Current Sensing
INA199
–0.3V to +26V
150µV
50, 100, 200
1.40%
Low-cost
Warning/
Shutdown
Sense
Resistor
12VDC
Single-ph
DC-DC
Vout
System
Power
FETs
High-side
current sensing (phase power)
Load
High-side
current sensing
(system power)
Current Feedback
Low-side current sensing
The graphic shows a generic buck regulator with the various shunt-based current-sensing methods. In an embedded DC-DC application only one method will be typically used in a production environment, but this block diagram shows all instantiations. The INA240 is a perfect device for high-side measurement for several reasons. To name a few, the high 80V input common-mode voltage, ultra high DC accuracy specs and, of course, PWM rejection. Keep in mind, though, the need for PWM ejection is greatly reduced because the current measurement is done after the inductor in the high-side phase power case.
As on the previous slide, the table on the right provides a listing of key products TI recommends for each of the current sensing methods. We don’t have to go over all these solutions now, but for low-side current the INA302 is a very efficient way to monitor an event where current exceeds a certain threshold and an ALERT is sent to the processor warning it something may be going wrong in the system. If a second threshold is crossed, then something catastrophic may have definitely occurred and a SHUTDOWN is recommended with a second ALERT pin. The beauty of this INA302 and its sister device, the INA303, is the response time from detection to ALERT asserted is less than 1µs. 8

9. TI solutions for embedded DC-DC power
Current measurement in Embedded DC-DC
TI Solutions for Embedded DC-DC
System benefits gained from using INA240
Part of the feedback control loop for DC-DC controllers
High accuracy current measurement
Enables smaller sense resistor value which lowers overall system power dissipation
High-side Current Sensing (system power)
Device
VCM Range
VOS
VOS Drift
Gain
Gain Error
Gain Error Drift
Comment
INA240
-4V to +80V
25µV
0.25µV/°C
20, 50, 100, 200
0.2%
2.5ppm/°C
Ultra-high Precision
INA210
-0.3V to +26V
35µV
60µV
100µV
0.1µV/°C
50, 75, 100,
200, 500
0.9%
10ppm/°C
High
Performance
INA301
0V to +36V
20, 50, 100
0.10%
Fast Comparator
INA302
Over/Under Current
High-side Current Sensing (phase power)
PWM Rejection
LMP8645
-2V to +42V
1000µV
7µV/°C
Adjustable 2%
140ppm/°C
Bandwidth
Low-side Current Sensing
INA199
–0.3V to +26V
150µV
50, 100, 200
1.40%
Low-cost
Warning/
Shutdown
Sense
Resistor
12VDC
Single-ph
DC-DC
System
Power
FETs
Vout
High-side
current sensing (phase power)
Load
High-side
current sensing
(system power)
Current Feedback
Low-side current sensing
Summarizing the system level benefits in a power application when using the new INA240, there are a few worth mentioning. The fact that it is part of the feedback control loop so you can rest assured you’ll be getting the most accurate reading possible because of the high accuracy capability of the device. Another huge benefit is the ability to use the smallest shunt resistor value possible due to the excellent offset, offset drift and DC common-mode rejection ratio of 132 dB. The last thing a designer wants to do is settle for a larger resistor value because his current sense amplifier is not at accuracy level he or she needs. With a small shunt the power dissipation is kept to minimum.
In the next section I will cover Texas Instruments reference designs that makes use of all three technologies we presented today. 9

10. Thank you for joining!