Electronic Design

Mixed-Signal 16-Bit μcontroller Supports 40-V I/Os for Auto Use

While digital circuits are obvious beneficiaries of deep-submicron technologies, analog and mixed-signal circuits also have benefited tremendously from these advances. Analog circuit techniques have been developed to tap the advantages of scaled CMOS processes and thereby achieve higher levels of mixed-signal integration. By modifying a standard embedded memory-logic CMOS process, engineers at Motorola's Semiconductor Products Sector in Munich, Germany, have shown that highly robust system-level integration is possible.

In paper 21.1 at last month's ISSCC in San Francisco, Motorola's engineers disclosed a 16-bit flash microcontroller that implements a set of robust analog I/O peripherals, such as voltage regulators, bus interfaces, and sensor interfaces, with 40-V breakdown voltage capability. In fact, this mixed-signal programmable microcontroller meets the mechatronic requirements of emerging automotive controller area network (CAN) applications.

According to the engineers, the real challenge was accommodating a wide voltage range on the same monolithic die. From 5 V for internal digital and analog functions, the chip also handles the 40 V needed for the analog I/O peripherals. To achieve this integration, the baseline 0.65-µm n-well/p-substrate process, with two-layer metal and poly, was modified to include two more mask steps. These additional steps provide MOS and bipolar components with a 40-V breakdown voltage. The gate oxide is 15 nm for the digital and 35 nm for the 40-V LDMOS transistors, respectively. As a result, to meet the needs of automotive analog peripherals, the process affords a number of high-voltage devices like low-ohmic LDMOS, high-voltage PMOS, bipolar npn, and substrate pnp.

Since the microcontroller is aimed at automotive CAN applications, the peripheral I/Os are designed to operate from a nominal voltage of 14 V with a breakdown of 40 V. The peripherals include a trimmable low-dropout voltage regulator, a physical network interface, and switch monitors that can read mechanical switches or Hall sensors in the automotive environment. With 1.8 million transistors on-chip, the 16-bit mixed-signal microcontroller dissipates 750 mW at 14 V.

TAGS: Automotive
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