A customer comparing the USB voltage regulators on the Series 0 and Series 1 Giant Gecko devices noticed that the required capacitances for VREGI (VBUS) and VREGO are different. In fact, they're actually reversed on Series 1 vs. Series 0:
|4.7 µF||1 µF||p.7 of AN0002.0 (revision 1.48) and AN0046|
|1 µF||4.7 µF||p. 27 of AN0002.1 (revision 1.50) and EFM32GG11 Reference Manual|
Given that certain packages for Series 1 Giant Gecko provide a pin-compatible upgrade path from Series 0, this could certainly cause some confusion. Is this a mistake?
While pin-compatibility purposes ought to dictate that the USB regulator on Giant Gecko Series 1 uses the same input and output capacitances as on Series 0, this is not the case. Those familiar with other EFM32 Series 1 (and EFR32) devices might recognize that the 4.7 µF output load capacitor is the same value as is used for the output DC-to-DC converter. In this respect, it makes sense that these voltage regulators have comparable requirements to maintain the stability of the output load and use the same recommended 4.7 µF capacitor.
So, customers upgrading their USB designs from Series 0 Giant Gecko to Series 1 will want to take note of this and make sure that the 1 µF capacitor is placed on VREGI while the 4.7 µF capacitor is placed on VREGO. Also, it's important to note that the capacitor for VREGO can be within the range of 1 to 10 µF depending on the load requirements with 4.7 µF being a nominal value suitable for most applications.