Power Control for Automotive Applications

Introduction
Maxim's analog and mixed-signal ICs have been widely accepted and acclaimed in the car electronics market. This is because many of the digital arithmetic processing technologies introduced to navigation units, high-speed communications systems, and sensing units make use of large-capacity, high-speed processing. Maxim is constantly committed to the development of new products tailored
to applications in the fragmented fields of infotainment, body electronics safety/security, and engine control and powertrain.

To maintain strict quality standards required of on-board products, Maxim has upgraded ISO 9000 certification to the automobile standard TS 16949, complies with AECQ-100 to ensure the reliability of each device, and, at the same time, performs tests requested by each user. This article describes products intended for car electronics.

3A Output Step-Down DC-DC Converter with a Built-In FET
Modern car electronics require highly efficient power ICs, as the vehicles are often equipped with a low-voltage, large-capacity core device. Since power ICs are mounted in radio units, it is important for ICs to operate in synchronization with the radio unit's frequency so that the switching frequency will not affect radios, TVs, GPSs, and other devices. The MAX16909 is a single-output current-mode step-down converter that uses a 45V process to ensure the reliability of onboard units (Figure 1). It is compatible with an input voltage range from 3.5V to 36V and capable of outputting a voltage of 1V to 10V.

Recently, there have been strong demands for high efficiency under a light load, and switching loss has been reduced by skip mode.

The MAX16909 operates in skip mode for reduced current consumption in light-load applications and supplies internal drive power from the output voltage. Thus, the device achieves an efficiency level of higher than 83% even under the conditions of an input voltage of 14V, an output voltage of 3.3V, and an output current of 10mA.

The MAX16909 supports a switching frequency range from 220kHz to 1MHz and can be downsized by sophisticated high-frequency Page 1 of 3design. However, the MAX16907 covers cases of switching in excess of the AM radio frequency range, and can deal with frequencies up to 2.2MHz. For packages, both TSSOP and TQFN are available.

LDO with a Built-In Current Sensing Amplifier and Switch for Remote Antenna
In the field of car electronics, a wide variety of radio units, including radios, digital TVs, and GPSs, are mounted in automobiles. In addition, a unit designed to convert radio signals into electric signals, which is called an antenna unit, is frequently installed separately from the main system. In this case, it is necessary to monitor both on-board problems and the current consumed by the unit in the remote state, and communicate them to the main system.

The MAX16946 is a device developed to support automotive remote module power applications (Figure 2). The basic principle of operation of this device is that the voltage of the onboard battery is converted into any given voltage between 3.3V and 15V by a linear regulator system, and this consumed current is detected by a current sensing amplifier (CSA) and output as an analog signal.
##IMAGE_2_C##
If the output detects a short circuit, earth fault, overcurrent, removal of load (detection of wire breakage), or another problem, each warning is communicated by a flag signal. The output current capacity is 500mA at 85°C and will be protected by a thermal shutdown function in the worst case.

Additionally, the dual-output MAX16948 is compatible with multiple power supplies. This product serves this application with the aid of a linear regulator system, but Maxim is considering a switching system in anticipation of growing demands for energy saving.

HB LED Driver with a Built-In High-Voltage CSA
Recently, the number of automobiles equipped with high-intensity LEDs for headlamps has increased. This is mainly because LEDs are superior to halogen and high-intensity discharge (HID) lamps, in that LEDs combine high efficiency, increased longevity, and distinguished design aesthetics. However, LED lamps required for car electronics need advanced analog technology because their intensity must be controlled at a constant level even in the wide voltage range of the on-board battery.

The MAX16833 drives high-intensity LEDs with a constant current and contains a high-side CSA. The switching FET is driven by detection by this sensing amplifier, so that the intensity of the LEDs connected in series can be maintained at a constant level. In addition, duty control (control that turns the LED current on and off) is used for the dimming of the LEDs, and a terminal for driving an FET other than the switching FET is provided.

The MAX16833 also supports three control systems, namely boost, SEPIC, and buck-boost. When the number of LEDs connected in series is large and the drop voltage of the LEDs is higher than the maximum value of the input voltage, only boost is applicable.

When the drop voltage of the LEDs is within the maximum and minimum values of the input voltage and boost cannot provide proper Page 2 of 3control, SEPIC or buck-boost is also available.
##IMAGE_3_C##
Conclusion
This article has described devices for on-board automobile applications. In the field of car electronics, Maxim develops new products, such as interfaces, battery monitors, and RF amplifiers, in addition to the products introduced herein.