Powering the Device with Modern DC-DC Regulators
The fleet tracking/management device, like other transportation electronics, is physically small. Removing the heat dissipation from the device to keep its temperature within range is a challenge. Fitting the power circuit into a small space requires high integration. Modern DC-DC power solutions that effectively integrate the power MOSFETs, compensation circuit, and other external components help reduce the circuit size. Combining the small solution size with the efficient synchronous rectification technology helps reduce the power dissipation. MAX15062 (4.5V-60V, 300mA), from Maxim’s Himalaya family, is an example of such a device, providing 92% peak efficiency in a tiny 8-TDFN 2x2mm package.
Figure 7: MAX15062 typical application schematic
To further increase integration, Himalaya power modules also integrate the power inductor, resistors, and capacitors with a DC-DC regulator. The result is easy-to-use, easy-to-design, and quick time-to-market power module solutions that only require an input capacitor, an output capacitor, two small voltage setting resistors , and an optional soft-start setting capacitor to complete the power solution. MAXM17545 (4.5V to 42V, 1.7A) and MAXM17575 (4.5V to 60V, 1.5A) are good examples of Himalaya power modules.
¬Today’s automobiles have hundreds of sensors. The same situation is true in intelligent transport automation. In both of these cases, the sensors are being added to equipment with extreme space constraints. Powering sensors requires even higher integration. MAXM17532 uses revolutionary packaging technology to miniaturize a 42V, 100mA power solution into a 2.6x3x1.5mm uSLICTM power module. This highly efficient synchronous DC-DC buck power module also minimizes the heat dissipation in the sensor.
- 4.0V to 42V VIN range
- 0.9 – 5.5V VOUT range
- 100mA continuous current
Figure. 8: MAXM17532 typical application schematic
Figure. 9: MAXM17532 uSLICTM power module in a tiny proximity sensor
One might say: I can power the sensor using an LDO! Yes, this is true since LDO is generally low cost and very simple to use, but it has high power dissipation, which is a main drawback. For example, a traditional simple digital/analog sensor might need 5V at 20mA and has 24V input (nominal). The power dissipation across the LDO is (24V – 5V) x 20mA = 0.38W (nominal). Newer sensors are packed with more intelligence, more functionality, and more flexibility – all of which also require more power, say 100mA.
Keeping the same input/output voltages, the power dissipation across the LDO would be (24V – 5V) x 100mA = 1.9W. This significantly higher power dissipation must be dissipated in the same sensor’s physical form factor. On top of this, there are now a lot more circuitries added to the sensor, requiring smaller size and higher integration. A power module that can address size and power dissipation requirements while delivering great efficiency would fit the bill here. Low power dissipation means lower system operating temperature and higher long-term reliability. Maxim’s Himalaya’s uSLICTM power module addresses both size and power dissipation requirements. At 24V input, 5V/100mA output, and 85% efficiency, the power dissipation in the MAXM17532 is (5V x 100mA) x (1/85% – 1) = 0.09W or a mere 5% of 1.9W, that would be dissipated in an LDO. Low power dissipation means lower system operating temperature and higher long-term reliability.
Summary
The after-market transportation electronics industry is growing to address both in-vehicle systems and transport infrastructure. Equipment designed for this market must be robust against transient conditions such as over voltage, over current, reverse voltage, reverse current, over temperature, etc. Highly integrated protection ICs provide all of the above protections and simplify the design over discrete solutions. Equipment is getting more functionality yet shrinking in size, requiring higher integration. Highly efficient power management solutions mitigate thermal dissipation challenges and enhance long-term reliability of the system.
