Keysight Technologies Accelerate Debug And Evaluation Of IoT Devices By Current Profile Analysis. Application Note

Keysight Technologies Accelerate Debug And Evaluation Of IoT Devices By Current Profile Analysis Application Note

02 Keysight Accelerate debug and evaluation of IoT devices by current profile analysis - Application Note Table of Contents Introduction... 03 Challenges of the IoT device design and development... 04 Can you solve these challenges using conventional methods?... 04 The benefits of the new method: Characterization and analysis of current profile... 05 The current profile contains crucial information... 05 Requirements on an instrument to obtain a useful current profile... 06 Issues of conventional measurement instruments... 06 New solution: CX3300 device current waveform analyzer... 07 Measurement Examples... 09 Connection... 09 Entire current profile... 09 Detailed current profile analysis during active mode... 09 Precise analysis of transient between sleep and active mode...10 Noise analysis during sleep mode...10 Quick current profile analysis with the Automatic Power and Current Profiler...10 Concurrent voltage measurement with the current waveform...11 Evaluation of fast inrush current and spikes...11 Validation of software operations...11 Measurement Hints...12 How to choose the right current sensor...12 How to connect a current sensor to your DUT...12 How to choose the appropriate current range...13 Low current measurement tips...13 Ordering Information...14 Summary...14

Introduction The application of the Internet of Things (IoT) has significantly expanded from consumerbased applications like healthcare, smart home and wearables, to industrial applications, like industrial automation and smart city. According to market research, the IoT device market is expected to further grow, with billions of devices connected to the internet in the near future. As such, the IoT device market represents a huge opportunity for device manufacturers. A typical IoT device structure is shown in Figure 1. Most IoT devices consist of MCU, PMIC, RFIC, sensors and small batteries such as coin batteries to sense motion from humans or other things and communicate with edge or cloud. Since IoT devices are typically used without power lines, the battery can seldom be re-charged or replaced. In order to minimize current consumption, IoT devices therefore typically only maintain active mode for brief periods of time, mostly operating in a sleep mode as shown in Figure 2. Battery Power Management To OSC Digital I/O MCU Actuator/ Display I/F RF Sensor AFE I/F Figure 1. Typical IoT device structure

04 Keysight Accelerate debug and evaluation of IoT devices by current profile analysis - Application Note Challenges of the IoT device design and development R&D engineers are facing the following challenges to design and develop IoT devices: Achieve an optimal balance between performance and power consumption to maximize battery life. Reduce the circuit design cycles of complicated, multifunctional products to meet time-to-market goals and maintain a competitive advantage. Prevent product defects to avoid costly recalls. Since most IoT devices run on small batteries, it is critical to achieve a balanced tradeoff between performance and power consumption. Current Active mode Sleep mode Figure 2. Basic IoT device operation Time It is also critical to retain or shorten the time-to-market to maintain the competitive advantage against the various advanced IoT devices continuously being introduced to the market. IoT devices are typically shipped in very high volumes. It is therefore vital to prevent any defects from occurring in advance, because any quality issues that result in measures such as a product recall can be extremely costly. Can you solve these challenges using conventional methods? Battery DMM Averaged power consumption IoT devices are typically evaluated with an oscilloscope, a signal analyzer, and a digital multimeter (DMM) as shown in Figure 3. However, as the functions and control of IoT devices are becoming more complicated, the typical tests mainly based on the voltage measurement, are no longer sufficient to solve the IoT device development challenges of optimizing performance and power consumption, shorting time-to-market, and of preventing product defects. Oscilloscope Digital I/O Actuator/ display Power management I/F To MCU OSC Signal analyzer Oscilloscope Sensor AFE I/F RF Figure 3. Typical evaluation configuration

05 Keysight Accelerate debug and evaluation of IoT devices by current profile analysis - Application Note The benefits of the new method: Characterization and analysis of current profile As shown in Figure 4, accurate measurement and analysis of the current profile provides the followings benefits that are not achievable by conventional methods, though the dynamic current waveforms of each component in the circuit have not been measured: Details of the circuit operation can clearly be seen, which helps with the optimization of performance and current consumption. It enables you to validate the hardware design and find potential defects at an earlier stage. It enables you to validate the software operation, managing the transition between sleep and active modes. It enables you to capture spikes, noise and other unexpected signals that can cause problems. You can solve the IoT device development challenges and dramatically improve the development efficiency and quality with current profile measurement and analysis. The current profile contains crucial information Figure 5 illustrates the types of important information that you can obtain from a detailed current profile. Digital I/O Actuator/ Display Figure 4. Characterization and analysis of current profile Current A Sensor Battery Power Management Active mode A A I/F A AFE I/F Sleep mode A Current profile for each power line To A MCU OSC A RF Inrush currents and spikes Inrush currents and spikes occur when the device changes mode, for example, from sleep to active mode. It can cause a voltage drop of Vdd or a degradation of battery capacity. Concurrent analyses of current and voltage waveforms on Vdd and subsystems can provide indications of the problem causes or troubleshooting. It also helps you to optimize the timing control and component selections, and validate your modifications perform as expected. Inrush current and spike Sleep current Time Active current Sleep current Active current Current profile analysis provides you with the current value and timing of each transition or segment in detail, and helps you to validate if the entire system is operated and managed as expected. In addition, the total current in the active state is the operating current consumption, which greatly affects the entire power consumption. Accurate current profile enables you to analyze each segment in detail and quantitatively determine the optimum balance between performance and current consumption, which has been difficult by measuring the averaged current. Figure 5. Current profile shows the interior device operation

06 Keysight Accelerate debug and evaluation of IoT devices by current profile analysis - Application Note Sleep current The sleep current greatly affects the standby power of the device. It is not negligible and impacts the overall power consumption particularly for IoT devices that stay in sleep mode most of the time. The current profile in sleep mode enables you to validate whether the device is in an unexpected state and consuming more power due to bugs in the software or hardware. Current > 10 MHz Sleep Wake-up Active Requirements on an instrument to obtain a useful current profile As shown in Figure 6, typical IoT devices have sleep current below μa, active current above 100 ma, and transient time between sleep and active modes below μs. Therefore, the measuring instrument must meet the following requirements in order to accurately analyze the current profile. Wide dynamic range to measure both sleep current below μa and active current above 100 ma. Wide bandwidth over 10 MHz to capture fast spikes and transients. Various functions to analyze current profile quickly. Concurrent measurement and analysis with voltage waveform and digital I/O signal to debug and troubleshoot efficiently. Sleep current < µa Figure 6. Characteristics of a typical IoT device Active current > 100 ma Time Issues of conventional measurement instruments Using a DMM or an oscilloscope with a shunt resistor/current probe is the most common way to measure current. However, the fast current waveform which changes between sleep and active cannot be captured with a single instrument or a single measurement with these instruments due to the lack of bandwidth, dynamic range or sensitivity as shown in Figure 7. Current Sleep Wake-up Active A DMM is too slow to capture the dynamic current waveform such as spike and transient, due to its slow sampling rates and averaging operation. Time Furthermore, an oscilloscope with a shunt resistor/current probe is not sensitive enough to measure the low-level dynamic current of IoT devices much lower than ma range. Additionally, even if these instruments can acquire the current waveform, it will not contain sufficient detail to be useful. Furthermore, this is coupled with there being no efficient and speedy way to create a current profile from the captured waveform. Cannot measure sleep current Cannot capture inrush currents and spikes Figure 7. Issues of conventional measurement instruments Cannot clearly view transient current

07 Keysight Accelerate debug and evaluation of IoT devices by current profile analysis - Application Note New solution: CX3300 device current waveform analyzer The Keysight CX3300 Device Current Waveform Analyzer is a new category of instrument that allows you to overcome IoT device measurement challenges and visualize previously undetectable wideband, low-level current waveforms. Key benefits: It can measure a complete current profile over a wide dynamic range, enabling the capture of sleep currents, active currents and everything in between in one measurement. It can capture spikes and low-level signals that were not previously detectable. It can immediately analyze details of a captured waveform. Figure 8 is an example of a transient current measurement from sleep to active mode. The CX3300 Device Current Waveform Analyzer can clearly capture the fast inrush current, transient current, and small noise in the sleep mode with a single measurement which was never possible to capture with conventional instruments. Clearly capture inrush current Capture the small noise in the sleep mode. Using a DMM Clearly view transient current Using a CX3300 Device Current Waveform Analyzer Idd (primary channel for whole current profile) Idd (secondary channel for sleep current) Figure 8. An example of a transient current measurement

08 Keysight Accelerate debug and evaluation of IoT devices by current profile analysis - Application Note CX3300 mainframe Max. 200 MHz bandwidth Max. 1 GSa/s sampling rate Max. 256 Mpts memory depth A similar look & feel to an oscilloscope enables you to start up quickly. Intuitive GUI on wide multi touch screen enables youto analyze and debug the waveform interactively. Sensor connector inputs (2ch or 4ch) CX1101A Single channel current sensor 40 na to 10 A Max. 100 MHz bandwidth Max. 40 V common mode voltage CX1151A Passive Probe Interface Adapter (for voltage monitor) Max. 80 V (with 1/10 probe) CX1102A Dual channel current sensor 40 na to 1 A Max. 100 MHz bandwidth Max. 12 V common mode voltage CX1103A Low side current sensor 150 pa to 20 ma Max. 200 MHz bandwidth Max. 1.0 V common mode voltage (with 50 Ω input on) CX1152A 10 MΩ Input Digital Channel (CX3324A option) Max. 8-channel Figure 9. The CX3300 Series Device Current Waveform Analyzer Product Overview Key features 14/16-bit resolution and wide dynamic range (from na to A) Max. 1 GSa/s sampling rate and 200 MHz bandwidth Max. 256 Mpts/ch memory depth Various functions to analyze current profile: automatic current profiler, cumulative current distribution function (CCDF) and fast Fourier transform (FFT)

09 Keysight Accelerate debug and evaluation of IoT devices by current profile analysis - Application Note Measurement Examples Here are the current profile measurement examples of IoT devices using a CX3300 Device Current Waveform Analyzer. Connection Figure 10 shows a connection example of an IoT device and a CX3300 Device Current Waveform Analyzer. The current sensor is inserted into the power supply line (Vdd) to measure the current (Idd) of the line. A passive probe is connected to Vdd to measure the voltage waveform at the same time, and Digital Channels are connected to the digital I/Os. Three types of the current sensors are available to satisfy the various application needs as shown in Figure 9. The CX1102A Dual Channel Current Sensor is used in this measurement because it is suitable for the wide dynamic range measurement of an IoT device. Figure 10. Connection example 10 sec with 20 MSa/s Digital channel Current sensor Passive probe Entire current profile Figure 11 shows the current profile for approximately 10 seconds after turning on the power. Detailed operation can be clearly captured over a long period due to the deep memory of up to 256 M pts/ch, and fast sampling rate Max. 1 G Sa/s. (In this example, 20 MSa/s with 200 Mpts memory is used.) Is the power-on sequence expected? From the Idd waveform, the device wakes up every 200 ms after power-on, and the operation mode is changed after a few seconds. From the entire current profile, you can validate the sequence after power-on, the approximate active and sleep current level and active period. The trigger source of this example is the Idd (primary channel), however you can change it to another current or voltage channel or digital channel depending on your application. Detailed current profile analysis during active mode Figure 12 shows the zoomed waveforms of Idd (primary and secondary channel) during the active mode of Figure 11. From the waveform of the primary channel, you can see the detailed transition between sleep and active mode and the operation in active mode. From the waveform of the secondary channel, you can see the small noise in sleep mode. Wake up every 200 ms Power-on Operation mode is changed Vdd Idd (primary channel at 200 ma range for whole current profile) Idd (secondary channel at 2 ma range for sleep current) Digital channel Figure 11. Whole current profile after power-on Zoom 1 ms/div What is the cause of the noise in sleep mode? Is the operation at the transition and active mode expected? Idd (primary channel) 10 ma/div Idd (secondary channel) 1 ma/div Figure 12. Zoomed Idd of active mode

10 Keysight Accelerate debug and evaluation of IoT devices by current profile analysis - Application Note Measurement Examples (continued) Precise analysis of transient between sleep and active mode Figure 13 shows the zoomed waveform at the transition from active to sleep mode of Figure 12, and shows that the device goes through several steps to reach sleep mode. From the transient current waveform, you can validate and debug the control sequence at the transitions. This example uses the Anywhere zoom function that allows you to zoom any specified section in the waveform. By checking the entire current profile and the zoomed waveform at the same time, you can validate and debug the waveform quickly and effectively. Is the power-on sequence expected? Figure 13. Zoomed Idd from active to sleep Zoom Expected sleep mode? Noise analysis during sleep mode Figure 14 shows the detailed noise analysis during sleep mode shown in Figure 12. The current waveform shows that the noise is 300 μa amplitude, and 1 ms interval, and the frequency-domain analysis by FFT shows that noise has peaks in the 8-10 MHz. With the never before seen wideband low-level waveform and analysis using a variety of analysis functions, you can reliably capture and analyze low but fast noise. 300 μa Zoom 1 ms FFT Figure 14. Noise analysis in sleep mode using FFT 10 MHz Quick current profile analysis with the Automatic Power and Current Profiler Figure 15 shows the detailed analysis of the current profile of Idd during the active mode shown in Figure 12. The Automatic Power and Current Profiler automatically segments a captured current waveform into different regions, and displays the information of each segment for analysis. (e.g. total charge consumed in a given region, average current consumption in that region, etc.). Automatic Power and Current Profiler It has been difficult to capture an accurate current waveform and create the current profile quickly using conventional instruments. However, using the CX3300 Device Current Waveform Analyzer, you can greatly accelerate the process of creating a current profile based on the precise dynamic current waveform, and dramatically improve debug efficiency. Figure 15. Easy current profile analysis using Automatic Power and Current Profiler

11 Keysight Accelerate debug and evaluation of IoT devices by current profile analysis - Application Note Measurement Examples (continued) Concurrent voltage measurement with the current waveform 7 mv 5 mv/div Figure 16 shows the voltage (Vdd) and current (Idd) waveforms during active mode. This shows that the peak of inrush current is 11.7 ma, and it causes a 7 mv drop of Vdd. By simultaneously monitoring voltage and current, you can understand how the voltage changes with changes of current, and validate, debug and troubleshoot the circuit modifications quantitatively and efficiently. 11.4 ma 2 ma/div Is the inrush current and voltage drop of it is in the allowable range? Vdd Idd Evaluation of fast inrush current and spikes Figure 16. Effective design validation through concurrent voltage measurement with the current waveform Figure 17 is the detailed analysis at the inrush current of Figure 16. You can check the shape of the inrush current and subsequent transient current waveform, quickly extract the key parameters such as the width or the peak with a variety of analysis functions, improve the debug efficiency and optimize the circuit design. Width: 1.4 µs Peak: 11.4 ma Figure 17. Inrush current analysis using the measurement function Validation of software operations Figure 18 shows the current waveforms with/without a software bug. The waveform on the upper figure takes longer at power-down than expected, indicating a possible bug of the control software. You can validate the software operation with the detailed current waveform traces. In addition, you can immediately check whether the bug is fixed. Bugs in the transition from active to sleep Expected transition Figure 18. A comparison of the transition with/without a bug in the software of the MCU

12 Keysight Accelerate debug and evaluation of IoT devices by current profile analysis - Application Note Measurement Hints In order to take full advantages of the CX3300 Device Current Waveform Analyzer s capabilities, there are some important points to note such as how to select the right current sensor and how to connect the current sensor to the DUT. Here are the measurement hints to perform appropriate measurements for accurate current profile analysis of IoT devices. How to choose the right current sensor As shown in Figure 9, the CX3300 Device Current Waveform Analyzer is configured with a dedicated mainframe and three sensors, CX1101A, CX1102A and CX1103A. These sensors are differentiated by bandwidth, current coverage and sensitivity, to satisfy various measurement needs. Table 1 below shows the bandwidth of the current range of each current sensor. The current measurement is limited between the upper limit and the noise floor of the range. The noise floor can be roughly estimated as 1/1000 of the full scale of the range and approximately 3-digits sensitivity is achievable in a single range, though actual noise floor can be influenced by environmental noise and the measurement conditions. For current profile measurements of IoT devices, the CX1102 dual channel current sensor is recommended. It covers wide measurement ranges from 40 na to 1 A, the bandwidth Max. 100 MHz 1 and the common mode voltage Max. ±12V. This sensor provides dual range, primary range and secondary range which is 1/100 of the primary range 2. The primary range is suitable to measure the entire current profile and the secondary range is suitable to accurately measure the sleep current at the same time. How to connect a current sensor to your DUT As the shown in Figure 19, there are three types of connection for the CX1101A and CX1102A, the coaxial (SMA) type, the twisted pair type and the test lead type. The SMA connector adapters enable wideband measurements, while the twisted pair and the test lead adapters are useful for quick current waveform measurements below 10 MHz. As shown in Figure 20, the current sensor is inserted where the current is measured in the circuit. Connect the negative electrode of the battery to the chassis ground terminal of the sensor via the ground lead. Table 1. The bandwidth of the current range of each current sensor Current Range Maximum bandwidth CX1101A CX1102A CX1103A Primary range Secondary range 10 A 3 MHz N/A N/A N/A 1 A 100 MHz 100 MHz N/A N/A 200 ma 100 MHz 100 MHz N/A N/A 20 ma 100 MHz 500 khz 100 MHz 200 MHz 2 ma 100 MHz 500 khz 100 MHz 75 MHz 200 μa 25 khz N/A 500 khz 9 MHz 20 μa 25 khz N/A 500 khz 2.5 MHz 2 μa N/A N/A N/A 250 khz 200 na N/A N/A N/A 100 khz 1. Max. standalone bandwidth 2. Except for the primary 1A range which operates with the 20 ma secondary range. Sensor heads and connection Solder wires With coaxial termination adapter With twisted pair adapter With test lead adapter Figure 19. The connection of sensor heads

13 Keysight Accelerate debug and evaluation of IoT devices by current profile analysis - Application Note How to connect a current sensor to your DUT (continued) As shown in Figure 20, the current sensor is inserted where the current is measured in the circuit. Connect the negative electrode of the battery to the chassis ground terminal of the sensor via the ground lead. Chassis ground terminal Ground lead How to choose the appropriate current range All current sensors have multiple current ranges and the range can be easily changed using the front panel 1. The maximum bandwidth and the input resistance of the current sensor depends on the range. When you switch the range, it is also changed automatically. The primary 200 ma range/secondary 2 ma range of CX1102 dual channel current sensor is recommended. The maximum bandwidth is 100 MHz 2 and the input resistance is 410 mω with the range. 1. Except for the CX1101A 10 A range. 2. Max. standalone bandwidth Meas. Target DUT GND Figure 20. Connection diagram of the current sensor Low current measurement tips It is necessary to minimize the noise and offset current as described below for measuring low-level current waveform. Minimize the influence of external noise The electrostatic shield is effective to reduce the influence of external noise. The shield should be connected to the chassis ground terminal of the current sensor. Minimize the noise floor of the instrument There is a trade-off between the bandwidth and noise floor, the lower noise floor with lower bandwidth. There are several ways to change the measurement bandwidth, by changing the Bandwidth Limit, Sampling Rate or Post-Filter. You can select these options according to your application needs. Minimize the offset current of the instrument and DUT The CX3300 Device Current Waveform Analyzer supports the User Calibration and Null. The User Calibration can calibrate the offset current of the current sensor itself, and the Null can minimize the offset current between the current sensor and the DUT. For further information 7 hints for precise current measurements with the CX3300 Series Device Current Waveform Analyzer (Pub #: 5992-2118EN) Before Mainframe + Current Sensor User Calibration Null DUT After the User Calibration and Null The User Calibration and Null offset is automatically subtracted from the waveform Figure 21. Minimize the offset current

14 Keysight Accelerate debug and evaluation of IoT devices by current profile analysis - Application Note Ordering Information Table 2 shows the typical configuration for the current profile measurement of IoT devices. You can select alternative configurations with higher bandwidth options and add the current sensors and sensor heads according to your application needs. Table 2. Typical configuration for current profile measurement of IoT devices Model CX3324A Opt. B05 Opt. 256 Description Device Current Waveform Analyzer, 1 GSa/s, 14/16-bit, 4 Channel Bandwidth 50 MHz Memory 256 Mpts/ch CX1102A Current Sensor, Dual Channel, ±12 V, 100 MHz, 40 na - 1 A CX1205A CX1151A N2843A CX1152A Sensor Head, Test Lead Adapter Passive Probe Interface Adapter Passive Probe, 10:1, 500 MHz Digital Channel, 10 Mohm Input, ±25 V, 8 Channel For further information, see the Configuration Guide of the CX3300 Series Device Current Waveform Analyzer (Pub #: 5992-1434EN) Summary As discussed in this application note, you can now obtain a significant amount of crucial information by measuring a current profile that has not been measured before. However, it is not possible to measure and analyze the current profile accurately and efficiently using conventional instruments such as a DMM and an oscilloscope with a shunt resistor/current probe. The new CX3300 Device Current Waveform Analyzer enables significant acceleration in the debugging and evaluation of IoT devices as follows: It enables you to measure and analyze the detailed current profile over a wide dynamic range from sleep to active mode on a single instrument. It enables you to capture the fast spikes and low-level signals that were not previously detectable. It enables you to analyze the details of a captured waveform quickly and efficiently. By enabling accurate and detailed current profile measurement and analysis, the Device Current Waveform Analyzer helps you to solve the following challenges that are faced when designing and developing IoT devices: Achieving an optimal balance between performance and power consumption to maximize battery life. Reducing the circuit design cycles of complicated, multifunctional products to meet time-to-market goals and maintain competitive advantage. Preventing product defects to avoid costly recalls.

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