ZHCSGN5B March 2017 – July 2018 LP8863-Q1
PRODUCTION DATA.
The boost controller can be clocked by an external BST_SYNC signal. If the external synchronization clock disappears the boost continues operation at the frequency defined by RBST_FSET resistor. If the external sync clock disappears while the SYNC pin level is low the boost continues operation without spread spectrum. If the external sync clock disappears, and BST_SYNC pin remains high the boost initially stops switching for approximately 256 μs and then begins switching with spread spectrum enabled.
If using the external BST_SYNC input, the external frequency must be between 1.2 and 1.5 times higher than the frequency defined by the RBST_SET resistor.
The boost converter has also an internal spread spectrum function that reduces EMI noise around the switching frequency and its harmonic frequencies. The internal spread spectrum function modulates the boost frequency ±3% from the central frequency with a 1.875-kHz modulation frequency. The spread-spectrum function cannot be used when an external synchronization clock is used.
BST_SYNC PIN LEVEL | BOOST CLOCK MODE |
---|---|
Low (GND) | Spread spectrum disabled |
High (VDDIO) | Spread spectrum enabled |
300-kHz to 2200-kHz clock frequency | Spread spectrum disabled, external synchronization mode |