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Power Management Power Management

Once again, powering down

peripherals shows quite ob-
vious advantages. This simple
technique might require rewrit-
ing some existing software and
drivers but does not need any
hardware modification. If you
need to add a load switch, the
Figure 5: Footprint & layout of the SPI32431 load switch from Vishay. footprint will be very small and
the task quite simple as de-

Obviously, the bigger battery option will end up picted in the following picture.
at the bottom of this list as it would be the most
Table 1: Cost with buck regulator. expensive choice. On the opposite, the selection of a bigger battery
often imply additional costs. For instance, the The use of an additional LDO here proves to be will increase the device’s form factor and foot-
highly efficient solution which consists in adding an economically viable choice. While the im- print, with a high probability of having to rede-
a buck regulator might be overlooked in some provement of power consumption might be less FORM FACTOR sign the mechanical casing. Yet, this modification
cases because of its relatively high price. significant, it is a satisfying low-cost strategy. The last criterion that will influence the choice might have a low impact if made at a very early

of a power management technique is its form stage of the design cycle.
On the opposite, the simple fact of powering At last, a load switch is not only simple to imple- factor. It will have a more or less significant im-
down each unused peripheral not only provides ment but also fairly affordable. Although battery pact on the decision-making process. It depends, Some solutions require adding passives, which
excellent results, but it also has almost no im- life gains are smaller than with other strategies, for instance, on available engineering resources, slightly increases the complexity of the design,
pact on the final budget. it is a must-have for most high-end use cases. the project’s advancement, the device’s size and as for the use of a buck regulator (six addition-
weight constraints, etc. al passives) or LDO regulators (four additional
passives). Those techniques will impact the PCB

Table 2: Cost with LDO.

Table 3: Cost for other components. Figure 6: Footprint & layout of the LTC3406A buck regulator from Analog Devices

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