Design your MSP430 power supply SMALLER

I recently wrote a post for the Power House blog on this same topic and thought was helpful to anyone using MSP430 as well. Check it out and leave me a comment.

So, let’s say you’re almost done with your latest and greatest MSP430 application. All the bugs have been rooted out and it’s working like a charm. It’s almost ready to hit the main stage but there’s one thing that still needs to be taken care of: power. After all, we can’t expect everyone to power their application with a lab supply, right?

                It’s not unusual that power comes as an afterthought. Systems are rarely, if ever, designed around power management; it’s the other way around. This sequence of events can cause panic, especially when there’s not a whole lot of space left on the PCB. Fortunately, quite a few MSP430 microcontrollers come in size-conscious packages that take up 4mm2 or less.

Although this helps our cause, it does not account for the surrounding analog circuitry. As a result, PCB space may still remain an issue.  The only recourse we have is to place the smallest power ICs we can find.

LDOs are a popular choice for applications stressed for space. This includes portable applications like fitness bands, smart watches, and other wearables. Engineers will often opt for LDOs because of the small chip sizes.

But should that be the only consideration?

It certainly is one of the most important. There are other factors that we need weigh like power consumption, noise characteristics, accuracy, etc., but the chip first needs to fit within the application to make it a plausible solution.

The physical dimensions of the IC begin to tell the story but are by no means comprehensive. As with any other IC, one needs to always consider external components. With an LDO, these include the resistor network, the input capacitor, and the output capacitor.

I recently wrote a post for the Power House blog on this same topic and thought was helpful to anyone using MSP430 as well. Check it out and leave me a comment.

So, let’s say you’re almost done with your latest and greatest MSP430 application. All the bugs have been rooted out and it’s working like a charm. It’s almost ready to hit the main stage but there’s one thing that still needs to be taken care of: power. After all, we can’t expect everyone to power their application with a lab supply, right?

It’s not unusual that power comes as an afterthought. Systems are rarely, if ever, designed around power management; it’s the other way around. This sequence of events can cause panic, especially when there’s not a whole lot of space left on the PCB. Fortunately, quite a few MSP430 microcontrollers come in size-conscious packages that take up 4mm2 or less.

Although this helps our cause, it does not account for the surrounding analog circuitry. As a result, PCB space may still remain an issue.  The only recourse we have is to place the smallest power ICs we can find.

LDOs are a popular choice for applications stressed for space. This includes portable applications like fitness bands, smart watches, and other wearables. Engineers will often opt for LDOs because of the small chip sizes.

But should that be the only consideration?

It certainly is one of the most important. There are other factors that we need weigh like power consumption, noise characteristics, accuracy, etc., but the chip first needs to fit within the application to make it a plausible solution.

The physical dimensions of the IC begin to tell the story but are by no means comprehensive. As with any other IC, one needs to always consider external components. With an LDO, these include the resistor network, the input capacitor, and the output capacitor.

Figure 2: A typical layout for an LDO power supply

This is the bottom line. There may be other LDOs out there that have a smaller chip size than 1x1mm but it’s impossible to find one with a smaller total solution size capable of sourcing 150mA. And, not only is it smaller, but it’s a more cost-effective solution.

[It should be noted here that although TLV713 is an extremely compact solution, it is not necessarily optimized for low-power operation like TPS782. Its quiescent current is rated at a typical 50uA which, although higher than that of an LDO like TPS782, isn’t necessarily detrimental to many battery-powered designs. Discretion should be exercised to determine if this tradeoff is appropriate for a given design.]

Power may be an afterthought but it need not necessarily be a nuisance.  Cap-free LDOs are capable of addressing power needs while consuming the minimum space possible: something that MSP430 applications are often in short supply of. Of course, research must be done to ensure that a Cap-Free LDO is the right fit for your application. Load transients or excessive ripple may very well dictate that it makes sense to add an output capacitor. Regardless, these LDOs offer another option in your back pocket when trying to optimize your power supply.

Before I head out, we will be giving 3 people a few of our EVM’s next week on Twitter. Just keep an eye out for images using the hashtag #IspywithTI and retweet for entry. I’ll update this post when the contest begins. Contest is now closed. Winners announced here.

As always, if you have any thoughts or questions about this topic or just want to say hello, please post a comment in the section below.

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