20 V Input, Tiny, 6.25 mm x 6.25 mm, 12 A and 15 A μModule Regulators
20VInpu15A μModule Regulators The LTM4626 and LTM4638 are high-efficiency, step-down μModule regulators capable of delivering 12 A and 15 A of continuous output current, respectively, from an input voltage of 3.1 V to 20 V. Both devices utilize an innovative 3D packaging structure called co-packaged package (CoP), in which the inductor is placed on top of the μModule device. The relatively high mass of the inductor, combined with direct air contact or attachment to a conventional heat sink, effectively draws heat away from the internal MOSFETs, enabling fast and efficient cooling in such small-area packages. These regulators are capable of supporting the output at full load conditions, where other regulators must operate at a reduced speed. For example, at 75°C ambient temperature and 200 LFM airflow, both regulators can generate a 1 V output at full load (12 A or 15 A) from a 12 V input.

Because they operate as current-mode DC/DC regulators, multiple devices can easily be combined in parallel to share higher load currents. Shunt regulators can operate out of phase to reduce input and output ripple by simply connecting the output and input clock pins of multiple devices. The total output voltage DC accuracy is guaranteed to be ±1.5% over the entire voltage, load, and temperature range (–40°C to + 125 °C). To compensate for any voltage drops caused by parasitic impedances at high currents, the LTM4626 and LTM4638 have built-in remote sensing. Output voltage tracking and soft-start features allow users to customize power sequencing. The switching frequency can be programmed with a simple external resistor (programmable from 400 kHz to 3 MHz) or synchronized to an external clock. The LTM4626 and LTM4638 have the same pinout.

Figure 1. The LTM4638 and LTM4626 have different output currents but have the same pinout.

12 V Input, 1 V Output, All Ceramic Capacitor Solution

Figure 3 shows an all-ceramic capacitor design that minimizes the overall solution size while allowing the input and output capacitors to be placed on the backside of the board. The design takes advantage of the built-in capabilities of the LTM4638 to minimize the circuit footprint, as shown in Figure 2. Figures 4 and 5 show the thermal performance and efficiency obtained using the DC2665A demonstration circuit under various conditions.

Figure 2. Tiny 15 A DC/DC μModule regulator solution using the LTM4638 mounted on a DC2665A-B demo board. The input and output capacitors are shown here - a few ceramic capacitors and a resistor on the back of the board.

Figure 3. LTM4638 12 V input, 1 V output, 600 kHz simplified schematic (using only ceramic capacitors and few components). The floating pins are not shown in the figure.

Figure 4. In this comparison (0 LFM and 200 LFM airflow), the effect of the efficient airflow cooling of the CoP design on the thermal performance of the LTM4638 is clearly visible (12 V input, 1 V/15 A output).

Figure 5. Efficiency of the LTM4626 and LTM4638 (12 V input, 1 V output, 600 kHz operating frequency).

Figure 6. LTM4626 on the DC2665A-A demo board.

in conclusion

The 6.25 mm x 6.25 mm LTM4626 and LTM4638 12 A and 15 A μModule regulators deliver high power in tiny thermally efficient packages. The CoP structure utilizes the exposed inductor as a heat sink for fast and efficient cooling. Only a few additional components are required to form a complete compact regulator solution. Multiple devices can easily be paralleled to provide larger loads for a truly high power density solution.