Maxim Design Solution | Making ADAS High-Resolution Remote Cameras Smaller and More Flexible

author:

- Bryan Dick, Senior Applications Engineer, Automotive Products Division, Maxim Integrated

- Chintan Parikh, Executive Business Manager, Automotive Products Division, Maxim Integrated

- Nazzareno (Reno) Rossetti, Analog and Power Management Technology Specialist, Maxim Integrated

High-resolution, remote cameras in modern cars (Figure 1) require more and more power while fitting into smaller spaces. Therefore, the power management components in the camera must be small and efficient to minimize heat generation, which would otherwise cause the internal temperature of the camera to rise rapidly, potentially affecting its reliability. Power management integrated circuits (PMICs) can effectively reduce size, but often at the expense of flexibility. This design review the shortcomings of common solutions and propose a highly integrated solution that is efficient and reduces PCB space while maintaining design flexibility and easy reuse.

Figure 1. Assisted parking

Figure 2 shows a high-level remote camera system. The remote camera is powered by an 8V supply over the coaxial cable. This POC (power over coax) rail is then stepped down into three voltage rails to power the imager and serializer.

Figure 2. Remote camera power supply

The typical solution shown in FIG3 uses three ICs and a large number of passive components to implement the power supply function shown in FIG2 , and the final PCB size is about 69 mm ² .

Figure 3. PCB size of a common solution (68.7mm ² )

Figure 4 shows a highly integrated solution where the three voltage rails (AVDD, I/O, CORE) are all from a monolithic PMIC.

Figure 4. Flexible PMIC architecture.

The above architecture can be implemented with the MAX20049 , a flexible, miniature, dual-channel, 500mA step-down converter with two LDOs. Spread spectrum and 2.2MHz switching frequency help reduce EMI and meet CISPR low-noise specifications. The stand-alone LDO3 has excellent PSRR, up to 90dB @ 1kHz. The PMIC integrates 4 regulators in a small 3mm x 3mm side-wettable SW) TQFN-16 package.

Thanks to the high clock frequency, the external components are very small. Combined with the small size TDFN-12 package, the PCB size is only about 38mm2 ^, as shown in Figure 5. This is 45% smaller than the traditional solution shown in Figure 3.

Figure 5. Using the MAX20049 results in a smaller PCB size (37.8mm ² )

The efficiency curve shown in Figure 6 was measured under the following conditions:

BUCK1 = 3.8V

I/O = 1.8V, I _BUCK2 100mA to 600mA

AVDD = 3.3 V, I _LDO3 = 50 mA

CORE = 1.2V, I _LDO4 = 100mA

Under these three conditions, system efficiency (output power on the three voltage rails divided by input power) at full load is an excellent 73%, compared to just 67% for competing products.

Figure 6. Higher efficiency helps reduce heat generation.

Three of the four regulators (BUCK1, BUCK2, LDO3) are almost independent with fully accessible inputs and outputs. This allows for great flexibility in the PMIC architecture, supporting multiple configurations with different image sensors. The fourth regulator (LDO4) is internally connected to BUCK2 to save pins and integrate the solution into the smallest possible package.

Figure 7. Highly flexible PMIC supports different image sensors

The PMIC is stress-test certified for packaged integrated circuits and fully meets AEC-Q100 requirements. The IC has fault protection to prevent abnormal conditions. If any buck output is shorted, the corresponding converter will perform cycle-by-cycle current limiting. If the LDOs are cascaded, the corresponding LDO output follows the buck output. The IC provides voltage monitoring for all four output voltage rails. When overvoltage or undervoltage is detected, the power-good indicator will become high-impedance.

The IC has an internal soft-start timer. Referring to Figure 4, the BUCK1 converter starts first with a ramp rate of 3.3V/ms. LDO3 starts simultaneously with BUCK1 with a soft-start time of 500μs. After BUCK1 reaches the regulation voltage, BUCK2 soft-starts with a ramp rate of 3.3V/ms. After BUCK2 reaches the regulation voltage, LDO4 begins soft-start. The IC provides overvoltage and undervoltage monitoring for all four voltage rails. When an overvoltage or undervoltage is detected, the power-good indicator changes to a high-impedance state.

The use of high-resolution remote cameras in modern automobiles is growing rapidly, requiring more and more power while fitting into smaller spaces. This creates challenges for flexibility, miniaturization of electronics, and heat dissipation. We review the shortcomings of currently available solutions and introduce the MAX20049 highly integrated PMIC, which increases efficiency while reducing PCB area and ensures design flexibility, allowing different image sensors to be easily reused.

Related Reading:

Maxim Press Release | Four-channel power management IC provides the most compact solution for automotive camera modules