Intelligent Power ICs Protect Themselves and Their Loads from Harm

As higher voltages, currents, and power levels become more the rule rather than the exception in industrial and automotive systems, safety and reliability are becoming increasingly critical specifications for power ICs under the hood.

For this reason, power semiconductor giants from Infineon and STMicroelectronics to Renesas Electronics and ROHM are rolling out new intelligent power devices (IPDs) that combine power MOSFETs with analog circuitry for diagnostic, protection, and control functions in a single chip. They’re “intelligent” in the sense that they can carefully regulate power while protecting themselves and their loads from failing or breaking down.

To enhance power density, these companies pack everything into smaller, more rigid packages and upgrade them under the hood to limit resistance and other parasitics that can cause excess power losses and, thus, heat that can sap the system’s performance. They’re also improving these power ICs to protect against a wider range of abnormal conditions and isolate faults faster—before they can lead to permanent damage.

These devices are typically designed to be placed on the high side of the system between the positive power line and the load, or on the low side connecting the load to ground. But regardless of where they’re placed, IPDs promise to reduce the risk and severity of failures even in the event of a malfunction in the microcontroller or other embedded processors. IPDs can also typically send diagnostics to the MCU that controls the power supply.

IPDs are relatively new to the world of power electronics, first hitting the market a decade ago or so. Below, we’ll explore how these devices are constructed and review some of the latest offerings on the market.

The IPD: More Than a Standard Power MOSFET

At the heart of every intelligent power device is a MOSFET, IGBT, or other power switching device that gives it the ability to drive resistive, inductive, and capacitive loads at different power levels, despite operating at relatively tame voltage levels.

While sufficient for a wide range of electronic systems, a normal power FET can sometimes fall short in situations where high power loads require more robustness and reliability. IPDs bring additional protection mechanisms and embedded control into the same die as the power FETs, which are at risk of failure or malfunction due to short circuits or other high currents and, in turn, heat that’s generated.

While it’s possible to use discrete components to add current limiting to a power FET, an IPD is said to measure current more accurately during light and heavy loads due to integrated current-sense circuitry.

Since they can protect the device itself and the load from large amounts of current and heat, IPDs are able to operate without breaking down due to abnormal conditions, including short circuits. These perks also open the door for them to replace traditional relays and fuses in some cases.

To prevent damage to the load, a fuse is placed in the path of the component that must be protected from potentially dangerous levels of current. When it blows, the fuse opens the circuit and blocks current before it enters the load.

IPDs use power FETs or other (relatively) high-speed switch devices to more quickly detect and interrupt overcurrent faults. Unlike fuses that must be ripped out and replaced after they blow, IPDs are resettable. They also remove the mechanical contact points in traditional relays, resulting in longer lifespans and higher reliability, which helps reduce the complexity and wiring requirements of power-distribution systems.

Intelligent Switch Safeguards Power Distribution in Cars

The latest single-channel, high-side “smart” power switch from Renesas is designed to distribute power safely and reliably around the rapidly evolving electrical and electronic (E/E) architectures in vehicles.

Based on its latest process technology for power FETs, the automotive-grade IPD features on-resistance of 2.3 mΩ and protects against short circuits and overcurrent conditions, open ground faults, overheating, and undervoltage lockout (UVLO). Current sensing and diagnostics are also part of the TO-252-7 package, which uses 40% less space on the PCB compared to the standard TO-263.

The IPD is designed to accommodate typical load currents of 30 to 35 A and has a minimum short-circuit overcurrent detection threshold of 150 A. Besides load current, internal temperatures and sense voltage levels are monitored by internal logic to protect the device and load during shutdown or power limiting. As usual with high-side switches, the internal FET is turned on and off by pulse-width-modulation (PWM) signals from the MCU.

In the event of a reverse battery condition where the output voltage exceeds the input, Renesas said the IPD can protect itself by turning on the FET upon detection of a simultaneous reverse ground current.

To improve the safety and reliability of power-distribution boxes and other power electronics in cars, the RAJ2810024H12HPD adds advanced current sensing so that it can accurately detect overcurrent events. Renesas said the IPD is also accurate at low loads, which enables you to design safe, precise power control systems that can detect even slight abnormalities. Charge-pump gate control circuitry is also integrated.

Today, power from the battery is distributed to each electronic control unit via long, thick wires from a distribution box that consists of mechanical relays and fuses. By replacing them with IPDs and programming the fuse characteristics into an MCU, you can use shorter, thinner wires to save costs and weight. The IC integrates a 3.3-/5-V logic interface to support more advanced automotive processors.

Low-Side Power Devices Turn Down the Heat During Switching

ROHM Semiconductor recently released two new families of 40-V, smart low-side switches—the BV1LExxxEFJ-C and BM2LExxxFJ-C series. They can support a broad range of on-resistance values (40/80/160/250 mΩ) in both single- and dual-channel configurations for everything from engine, transmission, and other control systems in cars as well as industrial control units and programmable logic controllers (PLCs).

The power ICs provide overcurrent and overvoltage protection, diagnostic features, and the ability to detect rapid temperature rise. The active-clamp circuit protects the IPDs from counter-electromotive force (stray energy that manifests as a voltage generated by motors, coils, and various other inductive loads). Self-turn-on protection prevents malfunctions during rapid battery rise. Contact discharge tolerance of the new series is higher than standard products, enhancing its reliability, said ROHM.

These devices can switch currents for resistive and capacitive loads, but they stand out when switching inductive loads on and off to control power distribution. While switching inductive loads off, the power MOSFET inside the smart switch needs to dissipate all of the magnetic energy stored inside the inductor’s magnetic field. During the transition, the device protects itself by actively clamping the voltage to a safe level. The power dissipated in the process generates heat that spreads out on the top of the power FET.

The new power switches integrate a high degree of heat dissipation while restricting on-resistance (RDS(on)) that can cause excessive power losses. These tend to be tradeoffs inside SOP-J8 (4.9 × 6.0 × 1.65 mm), HTSOP-J8 (4.9 × 6.0 × 1.0 mm), and other compact packages.

ROHM said it used its unique thermally distributed active-clamp control (TDACC) technology to optimally control how many current-carrying channels are present in each power IC and overcome the tradeoff.

12-V High-Side Power Switch Has Adjustable Current Limits

Current limiting is vitally important for driving large capacitive loads, including safety-critical systems and dashboard displays in cars. Charging a large capacitive load can draw inrush currents as high as 100 A, which can deal damage to both the load and the power switch itself. A large transient current can also inadvertently lead to supply voltage droop, which may harm other circuits in the system connected to the same power supply.

Addressing that issue, Infineon launched a smart automotive high-side 12-V power switch, called PROFET Load Guard. The power devices support a wide current limitation range between 0.3 and 8.7 A that changes depending on the on-resistance. As a result, you can set the protection level without intervention by the MCU. It avoids peak currents that endanger loads and provides fast fault isolation to the power-distribution side in the event of overload conditions due to failures in safety-critical loads such as the sensor-fusion box.

Using its capacitive load switching (CLS) mode, the power ICs can rapidly charge large capacitors while remaining within their safe operating area (SOA), improving robustness. The parts can accurately measure large amounts of current to prevent loads from being damaged as well as sense smaller amounts of current to allow for more accurate diagnostics and monitoring of the loads.

Featuring a wide operating voltage range from 3 to 28 V, the Load Guard power switches have a high degree of flexibility, said Infineon. If the load or system requirements change, the analog overcurrent limit can be easily adjusted to the new conditions by simply changing the resistor connected to the OCT pin. Besides flexibility, this feature also allows hardware-based wire protection for time-independent loads.

Rated at 2 to 3 A, the family consists of two 90-mΩ and two 50-mΩ devices, both available as single- and dual-channel automotive high-side power switches housed in a PG-TS-DSO-14 package.

Automotive High-Side Driver IC Has Smart Power Handling

A new series of single-, double-, and quad-channel automotive high-side drivers from STMicroelectronics present a more robust and accurate way to manage and protect automotive power-distribution systems and loads.

The intelligent power ICs are manufactured on the company’s VIPower M0-9 technology, which integrates the power blocks with on-chip temperature and current sensors, opening the door to more robust protection and more precise control of automotive loads. With very low standby current of only several microamps, these drivers reduce the drain on the battery when the vehicle is turned off and not being used.

The power ICs feature load-current limiting, load-dump protection up to 35 V, and limiting of fast thermal transients in the PowerSSO-16 package. Flexible reset management means you can configure the driver’s responses to faults depending on the system’s requirements. They support reverse-battery protection through a self-turn-on feature, which limits the power dissipation on the circuit board to a safe level.

There are also a wide range of diagnostic features, including high-accuracy, proportional load-current sensing that can detect malfunctions in the load. In addition, the power ICs support overload, short-to-ground, and short-to-VCC, and off-state open-load detection. The diagnostics functions work whether the power switch is turned on or off, permitting faults to be detected even when the load isn’t supplied, according to ST. Open load detection is used to flag open circuit failures in the power supply.

These switches are ideal for power-distribution boxes that deliver power from the 12-V battery bus—or the DC-DC converter that acts as the de facto 12-V battery in electric vehicles—to various sensitive electrical loads.

High- and Low-Side Power ICs Operate Up to 110°C

High- and low-side switching both have merits. But choosing one over the other often comes down to the application at hand. In general, using a high-side switch is recommended in cases where a heavy load only needs to be switched on or off. When the power to a load must be controlled via PWM, the preference is a low-side switch. Toshiba plays both sides of the switching debate.

The company rolled out a pair of intelligent power switches for industrial applications, including the eight-channel, high-side TPD2015FN switch and the eight-channel, low-side TPD2017FN.

The power ICs are based on Toshiba’s proprietary analog BiCD process technology, giving the power MOSFETs inside them the ability to achieve on-resistance of 400 mΩ on the output stage—a 50% improvement over its predecessors. They deliver power dissipation of up to 1.8 W, while offering internal current limiting and embedded control and charge pump circuitry (in the high-side switch).

Instead of requiring separate relays and fuses to protect against potentially harmful conditions, the IPDs integrate on-chip overcurrent protection. While current limiting helps prevent overheating, it’s not enough since the switch’s power dissipation stems both from current traveling through it and its voltage drop. Thus, they also support thermal shutdown, which turns the device off when the junction temperature rises above a safe level.

According to Toshiba, these power ICs are designed for industrial switching power supplies and inductive loads such as motors and inverters. To handle the high-stress environments on factory floors, the parts sport a maximum operating temperature of 110°C, which is 25°C higher than the company’s current power ICs. They come in a 9.7- × 7.6- × 1.2-mm SSOP30 package, which is significantly smaller (approximately 70%), shorter (around 80%), and narrower (with a 0.65-mm pin pitch) than its existing SSOP24 package.

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