I've been using the 5.0 volt version of this TSOP-5 chip for sometime without problems, until now. The regulator is driving a PIC 16F690. The PIC A/D reads a KTY-81 resistance temperature sensor as one side of a voltage divider and displays the result on a graphic LCD.
The temperature output is showing 5 degree F swings, at room temperature, when sampled at half second intervals. Bypassing the NCP551 with 5 volts eliminates these swings.
With a power source of 4 series alkaline "AA" cells the scope shows the Vreg output swinging from 4.92 to about 5.04 volts at a consistent frequency.
I prefer the NCP551 because the exterior capacitors are supposed to be non-critical. I'm using 0805 caps; a 0.1uf to bypass the input to the Vreg and a 1.0uf for Vreg output. Both caps are run of the mill chip units.
Have I underestimated the cap quality required? The NCP551 data sheet doesn't suggest this is so.
The temperature output is showing 5 degree F swings, at room temperature, when sampled at half second intervals. Bypassing the NCP551 with 5 volts eliminates these swings.
With a power source of 4 series alkaline "AA" cells the scope shows the Vreg output swinging from 4.92 to about 5.04 volts at a consistent frequency.
I prefer the NCP551 because the exterior capacitors are supposed to be non-critical. I'm using 0805 caps; a 0.1uf to bypass the input to the Vreg and a 1.0uf for Vreg output. Both caps are run of the mill chip units.
Have I underestimated the cap quality required? The NCP551 data sheet doesn't suggest this is so.