4 Small size is useful only if you can remove the heat

Putting more current into a smaller area raises heat density. A compact converter only helps if efficiency and thermal performance keep pace with the reduction in size. Optimizing the magnetic element in an integrated package together with the silicon helps reduce DC and AC losses, and the package itself can help spread heat away from the die.

Both advantages are important in an optical module. DSPs, lasers, and analog circuitry already contribute to the thermal load, and the fixed form factor limits cooling options. If the power stage runs too hot, your options are rather limited: reduce performance, improve the mechanical heat path, or accept less operating margin at elevated temperatures.

A current rating alone does not reveal whether a converter will work well in an optical module. Designers also need to look at efficiency at the actual operating point, temperature rise, and safe operating area (SOA). The question is not simply whether a converter can supply the current, but whether it can do so inside the real thermal environment of the module. Figure 3 shows the SOA curve for the TI 30A TPSM8287B30 power module with a 5.0V input voltage.