MMA8652 vs MMA8451

[tuurbo46]

Hi,

I am just in the process of selecting a new Accelerator.  I have rounded my selection down to two chips, the MMA8652 and the MMA8451.  Am I correct in thinking other than one is 12bit and the other 14bit, and they have different packages, they are both similar in complexity?  My meaning is, one is not easier to program and configure over the other chip.

Also from a design point of view on low power battery powered products, is it better to have the INT pins pull-up or pull-down?

Lastly looking at the datasheet on the MMA8652, the circuit diagram shows polarized capacitors around the chip, I think these should be none polarized.  Am I correct?

Thanks,

[david_diaz]

Hello,

1. Basically, the main differences between the devices mentioned are the resolution and the package options.

2. In regard with the complexity you mentioned, both of the devices use the I2C interface.

You can find software examples here in order to program and configure the device you need.

3. It depends of your application if you place a pull-up or pull-down on the INT pins.

The interrupt pins can be configured to be push-pull or open drain and can be either Active High or Active Low. If a pull-up resistor is used on the interrupt pins with the open drain setting, then the accelerometer should be configured to Active Low. If a pull-down resistor is used, then the interrupt pin should be configured to be Active High. This is done in Register 0x2C (MMA8451, 2, 3Q).

For more details please review the Application note AN4077:

AN4077 - MMA845xQ Design Checklist and Board Mounting Guidelines

4. Finally, the capacitor at the BYP pin should be place there in order to guarantee the stability of the internal regulator while the rest of them are decoupling capacitors.

I hope this information will be useful for you.

If I misunderstood your question, feel free to let me know.  I will be glad to help.

Have a great day.

David Diaz.

[tuurbo46]

Hi David,

Thanks for your reply.

Just to double confirm, the datasheet shows all 4 capacitors as polarized, which I think is a typo.  Is it OK to use 4 none polarized capacitors?

Thanks.