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Why does 1.6 kΩ attach to RREF pin of UPD720150 requires accuracy of ±1%?

Latest Updated:02/01/2009

Question:

Why does the 1.6 kΩ resister attached to the RREF pin  of the UPD720150 USB host/peripheral controller require an accuracy of ±1%?

Answer:

The RREF pin is used as both the AVSS (R) pin and the pin that generates the reference voltage for the internal analog circuits. To improve the accuracy of the generated voltage, the resistor connected to the pin must have an accuracy of ±1%. Also, when designing the board, be sure to implement a layout that ensures that this pin is not affected by noise. See the USB 2.0 Board Layout Guideline for details.
Suitable Products
I/F for Serial Control