Tomorrow’s Vehicles Will Have Even More Technology

Von Rich Miron

Zur Verfügung gestellt von Digi-Key Electronics

In the past, electronic systems contributed as little as one percent of the total value of vehicles. Today, however, consumer demand for more technology and the increased technological capabilities available have resulted in the number of electronic control units (ECUs) required in a vehicle to skyrocket. For example, as many as 100 ECUs and up to 100 million lines of code may be required in a high-end automobile today - far more than past vehicles and proof to the importance of ECUs to the makeup of an automobile.

Electricity increasingly powers advanced electronics and fuels hybrid (HEV) and electric vehicles (EVs) while reducing CO2 emissions while electronic systems replace manual and motorized components. All of this ensures that the future of driving will look very different from transportation today. Emission optimized HEVs and self-driven, zero-emission EVs will communicate within the vehicle’s systems and with city and roadway infrastructure in addition to other vehicles. The Texas Instruments’ (TI) white paper, “Driving the Green Revolution in Transportation”, goes into further detail of the benefits of HEVs and EVs.

There are several major factors that are driving a surge in consumer demand for HEVs and EVs:

  • Internal combustion engine environmental regulatory pressures
  • Electric powertrain and battery technological advances
  • Consumer expectations for features of convenience and infotainment

There is one limiting factor, the capacity limits of the traditional 12 V lead acid battery are being pushed by the increasing power-load requirements of these innovations. The automobile industry has come up with a solution in order to meet this increased demand for electrification. They have developed a secondary 48 V electrical system which supplies more power than a traditional 12 V battery can produce alone. These high voltage systems, however, require extensive isolations for safety and insulation control to keep drivers and their passengers safe from electric shock along with avoiding the breakdown of system safety.

To help overcome these design challenges and enable a safer, more efficient transportation systems, TI offers many solutions and design aids. The following is a selection of some these parts and reference designs.

TIDAs – Texas Instruments Reference Designs

TIDA-03040 – Automotive Shunt-Based ±500 A Precision Current Sensing Reference Design: This TI shunt-based current sensor reference design (Figure 1) offers a < 0.2% FSR accuracy over the operating temperature range of -40°C to +125°C. A number of automotive applications require precision current sensing including battery management systems, motor currents, and others. Poor accuracy in these critical applications can generally result from non-linearity, temperature drift, and shunt tolerances. These problems are solved by this design by using TI’s current shunt monitors (INA240) and signal conditioners (PGA400-Q1).

Block Diagram of Texas Instruments’ TIDA-03040 Reference Design

Figure 1: Texas Instruments’ TIDA-03040 Reference Design Block Diagram for an Automotive Shunt-Based ±500 A Precision Current Sensor. (Image source: Texas Instruments)

TIDA-03050 - Automotive, mA-to-kA Range, Current Shunt Sensor Reference Design: In this reference design, a busbar-type shunt resistor is used to detect currents in the mA to KA range. The EV and HEV ever rising demand from their high-capacity batteries forces larger operating current spans and highly accurate current sensors to monitor demand. Accurately measuring current over three decades (mA to A, 1 A to 100 A, and 100 A to 1,000 A) is quite a challenge since there is a large amount of system noise. To solve this problem, this design uses a TI high-resolution analog-to-digital converter (ADC) and high-accuracy current shunt monitors.

TIDA-01604 - 98.6% Efficiency, 6.6-kW Totem-Pole PFC Reference Design for HEV/EV Onboard Charger: Silicon carbide (SiC) MOSFETs driven by a C2000 MCU with SiC-isolated gate drivers is the basis of this reference design (Figure 2). Three-phase interleaving is implemented in this design which operates in continuous conduction mode (CCM) with a 98.46% efficiency when at a 240 V input and 6.6 kW full power. Light load power factor is improved by phase shedding and adaptive dead-time control enabled by the C2000 MCU. The gate driver board (see TIDA-01605 discussed next) can deliver a 4 A source current and sink peak current of 6 A while implementing a reinforced isolation and withstanding more than 100 V/ns common-mode transient immunity (CMTI). The gate driver board also contains a two-level turn-off circuit, protecting the MOSFET from voltage overshoot if a short-circuit situation occurs.

Image of Texas Instruments’ TIDA-01604 Reference Design for a HEV/EV Onboard Charger

Figure 2: Texas Instruments’ TIDA-01604 Reference Design for a HEV/EV Onboard Charger. (Image source: Texas Instruments)

TIDA-01605 - Automotive Dual Channel SiC MOSFET Gate Driver Reference Design with Two Level Turn-off Protection: This TI reference design features an automotive qualified isolated gate driver solution for driving SiC MOSFETs in a half-bridge configuration. Two push-pull bias supplies for the dual channel isolated gate driver are included in this design with each supply capable of providing +15 V and -4 V output voltages and an output power of 1 W. As noted earlier, this gate driver can deliver a 4 A source current and a 6 A sink peak current. Its reinforced isolation is capable of withstanding 8 kV Peak and 5.7 kV RMS isolation voltages and has a CMTI of >100 V/ns. Also noted earlier, this board contains a two-level turn-off circuit, protecting the MOSFET from voltage overshoot if a short-circuit situation occurs. This design features a configurable DESAT detection threshold and delay time for second stage turn-off. For interfacing the signals of fault and reset, an ISO7721-Q1 digital isolator is used. Overall, this reference design fits on a two-layer printed-circuit board (PCB) board with a 40 × 40 mm compact form factor.

TIDA-01168 - Bidirectional DC-DC Converter Reference Design for 12 V/48 V Automotive Systems: This reference design functions as a 4-phase, bidirectional DC-DC converter development platform for 12 V/48 V automotive systems. The system uses a TMS320F28027F MCU and two LM5170-Q1 current controllers for power stage control. The C2000 MCU provides voltage feedback while the LM5170-Q1 subsystems use average current feedback for current control. Using this control scheme eliminates phase current balancing typical for multiphase converters. LM5170-Q1 based systems allow a high level of integration, reducing PCB area, simplifying design, and accelerating development.

Products

ISO7731-Q1: The ISO773x-Q1 device family are high performance, triple-channel digital isolators with 5,000 VRMS (DW package) and 3000 VRMS (DBQ package) isolation ratings per UL 1577. This family has reinforced insulation ratings according to CQC, CSA, TUV, and VDE. These devices provide high electromagnetic immunity with low emissions at low power, while isolating CMOS or LVCMOS digital I/Os. Logic input and output buffers are separated by a silicon dioxide (SiO2) insulation barrier in each isolation channel. Device enable pins can be used to place the respective outputs in high impedance for multi-master driving applications and for reduced power consumption. The ISO7730-Q1 device has all three channels in the same direction while the ISO7731-Q1 device has two forward and one reverse-direction channel. Upon losing either the input power or signal, the default output is low for devices with “F” suffix and high for devices without “F” suffix.

UCC21520-Q1: This device is an isolated dual-channel gate driver (Figure 3). It features a 4 A source current and 6 A sink peak current. It is designed to drive power MOSFETs, SiC MOSFETs, and IGBTs at up to 5 MHz with low propagation delay and pulse-width distortion. The input side and the two output drivers are isolated by a 5.7 kVRMS reinforced isolation barrier, with a minimum of 100 V/ns CMTI. A working voltage of up to 1500 VDC is allowed by internal functional isolation between the two secondary-side drivers. The design of this device allows every driver to be configured as either two low-side drivers, two high-side drivers, or a half-bridge driver with programmable dead time (DT). Both outputs are shut down simultaneously by a disable pin, allowing normal operation when left open or grounded. Primary-side logic failures force both outputs low as a fail-safe measure.

Functional Block Diagram of the UCC21520-Q1 isolated dual-channel gate driver from Texas Instruments

Figure 3: Functional Block Diagram of the UCC21520-Q1 isolated dual-channel gate driver from Texas Instruments. (Image source: Texas Instruments)

UCC21222-Q1: This isolated dual channel gate driver with programmable dead time and wide temperature range exhibits consistent performance and robustness under extreme temperature conditions. Its 4 A peak-source and 6 A peak-sink current are designed to drive power MOSFET, IGBT, and GaN transistors. The UCC21222-Q1 has multiple configurations: two low-side drivers, two high-side drivers, or a half-bridge driver. The 5 ns delay matching performance allows the paralleling of two outputs which doubles the drive strength for high load conditions without the risk of internal shoot-through. The two output drivers are isolated from the input side by a 3.0 kVRMS isolation barrier with a minimum of 100 V/ns CMTI.

LM5170-Q1: The essential high voltage and precision elements of a dual-channel bidirectional converter for automotive 48 V and 12 V dual battery systems is enabled by the LM5170-Q1 controller. It does this by regulating the average current flowing between the high voltage and low voltage ports in the direction designated by the DIR input signal. The current regulation level is programmed through either the analog or the digital PWM inputs. Typical current accuracy of one percent is achieved by dual-channel differential current sense amplifiers and dedicated channel current monitors. The 5 A half-bridge gate drivers are capable of driving parallel MOSFET switches which can deliver 500 W or more per channel. Additionally, not only does the diode emulation mode of the synchronous rectifiers prevent negative currents, but it also enables discontinuous mode operation for improved efficiency with light loads. Many protection features are incorporated into the device including MOSFET failure detection, overvoltage protection at both HV and LV ports, cycle-by-cycle current limiting, and over temperature protection.

INA301-Q1: This device includes both a high common-mode, current-sensing amplifier and a high-speed comparator configured to provide overcurrent protection. It does this by measuring the voltage across a current-sensing or current-shunt resistor and comparing it to a defined threshold limit. The INA301-Q1 features an adjustable limit-threshold range that can be set by using a single external limit-setting resistor. This current-shunt monitor measures differential voltage signals on common-mode voltages that can vary from 0 V up to 36 V, independent of the supply voltage. The open-drain alert output has the option to be configured to operate in either a transparent mode, where the output status follows the input state, or in a latched mode, where the alert output is cleared when the latch is reset. Rapid detection of overcurrent events is enabled by a device alert response time of less than 1 µs.

INA240-Q1: The automotive-qualified INA240-Q1 is a voltage-output, current-sense amplifier with enhanced PWM rejection. It can sense drops across shunt resistors over a wide common-mode voltage range from -4 V to 80 V, independent of the supply voltage. The benefit of the negative common-mode voltage is that it allows the device to operate below ground which accommodates the flyback period of typical solenoid applications. The device’s enhanced PWM rejection provides high levels of suppression for large common-mode transients (ΔV/Δt) in systems that use PWM signals including motor drives and solenoid control systems. This feature ensures accurate current measurements without large transients and associated recovery ripple on the output voltage. The INA240-Q1 operates from a single 2.7 V to 5.5 V power supply and draws a maximum of 2.4 mA. There are currently four fixed gains available: 20 V/V, 50 V/V, 100 V/V, and 200 V/V. The device’s low offset, zero-drift architecture enables current sensing with maximum drops across the shunt as low as 10 mV full-scale. Grade 1 versions are offered in an 8-pin TSSOP and 8-pin SOIC packages and operate over the extended temperature range of –40°C to +125°C. Grade 0 versions are only offered in an 8-pin SOIC package and operate over the extended temperature range of -40°C to +150°C.

AMC1305M05-Q1: This is a precision delta-sigma (ΔΣ) modulator with a capacitive double isolation barrier that is highly resistant to magnetic interference separating the output from the input circuitry (Figure 4). The isolation barrier is certified to provide reinforced isolation of up to 7,000 VPEAK according to the DIN V VDE V 0884-10, UL1577, and CSA standards. When paired with isolated power supplies, the AMC1305M05-Q1 prevents noise currents that may be present on a high common-mode voltage line from entering the local system ground and interfering with or damaging low voltage circuitry. This device, optimized for direct connection to shunt resistors or other low voltage level signal sources, supports excellent AC and DC performance. Typically, shunt resistors sense currents in onboard chargers, traction inverters, or other such automotive applications. With the use of an appropriate digital filter to decimate the bit stream, such as those integrated on the TMS320F2837x, the device can achieve 16-bits of resolution with a dynamic range of 85 dB (13.8 ENOB) at a data rate of 78 kSPS.

Simplified Schematic of Texas Instruments’ AMC1305M05-Q1 precision delta-sigma (ΔΣ) modulator

Figure 4: Simplified Schematic of Texas Instruments’ AMC1305M05-Q1 precision delta-sigma (ΔΣ) modulator. (Image source: Texas Instruments)

TMS320F28069M: The automotive qualified F2806x Piccolo family of MCUs include the power of the C28x core and CLA coupled with highly integrated control peripherals in low pin-count devices. These devices are code-compatible with previous C28x-based code and provide a high level of analog integration. Other features include an internal voltage regulator that allows for single-rail operation and enhancements to the HRPWM module that allow for dual-edge control (frequency modulation). Additionally, analog comparators with internal 10-bit references that can be routed directly to control the ePWM outputs have been added. The ADC, which has an interface optimized for low overhead and latency, converts from 0 to 3.3 V fixed full-scale range and supports ratio-metric VREFHI/VREFLO references.

ISO1042-Q1: This is a galvanically-isolated controller area network (CAN) transceiver device that meets the specifications of the ISO11898-2 (2016) standard. The ISO1042-Q1 offers ±70 VDC bus fault protection and a common-mode voltage range of ±30 V. It supports a data rate up to 5 Mbps in CAN FD mode which allows a much faster transfer of payload when compared to classic CAN. There is a SiO2 insulation barrier in this device that has a withstand voltage of 5,000 VRMS and a working voltage of 1,060 VRMS. The electromagnetic compatibility of the ISO1042-Q1 has been significantly enhanced to enable system-level ESD, EFT, surge, and emissions compliance. When paired with isolated power supplies, this device can help protect against high voltage and noise currents from the bus entering the local ground. The ISO1042-Q1 is available for both basic and reinforced isolation applications and supports a wide ambient temperature range of -40°C to +125°C. It is available in two package sizes, the SOIC-16 (DW) package and a smaller SOIC-8 (DWV) package.

Conclusion

The future of the automotive industry is bright. However, the designs will be more complicated as more features, driven by environmental regulations and consumer demand, are added to vehicles. To help support these features, Texas Instruments has a wide variety reference designs and products available now that can help reduce design time and get these future automotive designs to the consumer sooner.

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Über den Autor

Rich Miron

Rich Miron, Senior Technical Content Developer bei Digi-Key Electronics, ist seit 2007 in der Gruppe für technische Inhalte tätig und ist hauptsächlich für das Schreiben und Bearbeiten von Artikeln, Blogs und Produktschulungsmodulen verantwortlich. Vor Digi-Key hat er Mess- und Regelsysteme für Atom-U-Boote getestet und qualifiziert. Rich hat einen Abschluss in Elektrotechnik und Elektronik von der North Dakota State Universität in Fargo.

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Digi-Key Electronics

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