MSP430F5338: RTC working time when powered using Super Capacitor only

VEERAMANI VISWANATHAN B

Prodigy 85 points

Part Number: MSP430F5338

Hi,.

We are designing a system in which MSP430F5338 is used.

For powering the RTC in the MSP430 during shutdown, we have used a 3.5V 0.22uF super capacitor connected to VBAT.

The question is that, how long will the super cap alone be able to supply power for RTC to work?

Or, how can we determine the duration for the which the RTC is working with super cap alone connected?

Thank you.

over 5 years ago

0 Eddie LaCost over 5 years ago

TI__Mastermind 38590 points

Hello Veeramani,

The current consumption of the MSP430F5338 can be found in the datasheet(section 5.5). Also, note the minimum operational voltage in section 5.2 as the supercap will discharge fairly linearly and you will need to know when the MSP430 cannot operate any more. Also, I found a handy calculator tool to help calculate the discharge time.

www.circuits.dk/calculator_capacitor_discharge.htm

0 VEERAMANI VISWANATHAN B over 5 years ago in reply to Eddie LaCost

Prodigy 85 points

Hi Eddie,
Thanks for the reply
According to the section 5.2 the minimum operational voltage is 1.70V
So, if I am testing it practically, and I get a different result, Which result should I consider?

0 Eddie LaCost over 5 years ago in reply to VEERAMANI VISWANATHAN B

TI__Mastermind 38590 points

I would go with the datasheet value. I am assuming that you have observed it can actually operate at a lower voltage. It is possible that our devices can operate outside of the specification, especially at lower clock rates, but this is not guaranteed and could vary from device to device. The minimum datasheet specification should be applicable to all devices we ship.

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MSP430F5338: RTC working time when powered using Super Capacitor only