ZHCSLM3B August 2020 – May 2024 LP8864-Q1
PRODUCTION DATA
The LP8864-Q1 current-mode-controlled boost DC/DC controller generates the anode voltage for the LEDs. The boost is a current-mode-controlled topology with a cycle by cycle current limit. The boost converter senses the switch current and across the external sense resistor connected between ISNS and ISNSGND. A 20mΩ sense resistor results in a 10A cycle by cycle current limit. The sense resistor value could vary from 15mΩ to 50mΩ depending on the application. Maximum boost voltage is configured with external FB-pin resistor divider connected between VOUT and FB. The FB-divider equation is described in Section 6.3.6.3.
Figure 6-3 Boost
Controller Block DiagramThe boost switching frequency is adjustable from 100kHz to 2.2MHz via an external resistor at BST_FSET (see Table 6-2). Resistor with 1% accuracy is needed to ensure proper operation.
| R_BST_FSET (kΩ) | BOOST FREQUENCY (kHz) |
|---|---|
| 3.92 | 400 |
| 4.75 | 200 |
| 5.76 | 303 |
| 7.87 | 100 |
| 11 | 500 |
| 17.8 | 1818 |
| 42.2 | 2000 |
| 124 | 2222 |