SLUSEK7 September 2024 BQ25773
PRODUCTION DATA
Refer to the PDF data sheet for device specific package drawings
Normally, the IC switches in fixed frequency which can be adjusted through FSW_SYNC pin. The charger also supports frequency dithering function to improve EMI performance and help pass IEC-CISPR 32 specification. This function is disabled by default with setting EN_DITHER=00b. It can be enabled by setting EN_DITHER=01/10/11b, the switching frequency is not fixed when dithering is enabled, it varies within determined range by EN_DITHER setting, 01/10/11b is corresponding to ±2%/4%/6% switching frequency. The larger dithering range is selected, the smaller EMI noise peak will be, but at same time slightly larger output capacitor voltage ripple is generated. Therefore, the dithering frequency range selection is a trade-off between EMI noise peak and output voltage ripple, recommend to choose the lowest dithering range which can pass IEC-CISPR 32 specification. The patented dithering pattern can improve EMI performance from switching frequency and up to 30-MHz high frequency range which covers the entire conductive EMI noise range.
It should be noted that the Dithering feature will not work if an external clock is provided.