ZHCSKL3C December 2019 – May 2024 LP8866-Q1
PRODUCTION DATA
Spread spectrum function could be enabled when BST_SYNC pin is high and disabled when BST_SYNC pin is low.
If an external CLK signal is on the BST_SYNC pin, the boost controller can be clocked by this signal. If the clock disappears later, the boost continues operation at the frequency defined by RBST_FSET resistor, and the spread spectrum function will be enabled or disabled depending on the final pin level of BST_SYNC.
| BST_SYNC PIN LEVEL | BOOST CLOCK MODE |
|---|---|
| Low (GND) | Spread spectrum disabled |
| High (VDDIO) | Spread spectrum enabled |
| 100kHz to 2222kHz clock frequency | Spread spectrum disabled, external synchronization mode |
If using the external BST_SYNC input, the RBST_SET resistor should be chosen the closest boost frequency options with the external frequency.
The spread spectrum function helps to reduce EMI noise around the switching frequency and its harmonic frequencies. The internal spread spectrum function modulates the boost frequency ±3.3% to 7.2% from the central frequency with a 200Hz to 1.2kHz modulation frequency. The switching frequency variation is programmable by SPREAD_RANGE register, and the modulation frequency is programmable by SPREAD_MOD_FREQ register. The spread-spectrum function cannot be used when an external synchronization clock is used.
| SPREAD_RANGE (Binary) | SWITCHING FREQUENCY VARIATION |
|---|---|
| 00 | ±3.3% |
| 01 | ±4.3% |
| 10 (Default) | ±5.3% |
| 11 | ±7.2% |
| SPREAD_MOD_FREQ (Binary) | MODULATION FREQUENCY |
|---|---|
| 00 (Default) | 200Hz |
| 01 | 500Hz |
| 10 | 800Hz |
| 11 | 1200Hz |