SLUSCZ1 May 2017 TPS92518-Q1
PRODUCTION DATA.
NOTE
Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality.
The TPS92518-Q1 buck current controller is suitable for implementing step-down LED drivers. This section presents a simplified design process for an LED driver with the specifications shown in Design Requirements:
Use the following design procedure to select component values for this and similar buck applications.
Buck converter topology.
PARAMETER | VALUE | UNIT | |
---|---|---|---|
VIN | Input voltage | 50 | V |
ILED | LED current | 1.6 | A |
VLED | LED voltage | 9.4 | V |
ΔIL-PP | Ripple voltage change | 12.5% | |
LEDx_PK_DAC[7:0] | Target switching frequency | 550 | kHz |
VEN/UV | 40 | V | |
VEN/UV-HYST | 5 | V |
TPS92518-Q1 Design Equations and sample Calculations.
Start by calculating the converter Duty Cycle
then:
The user has the option of choosing a value of 68µH, however, this design uses the next common value of 100 µH in order to meet the ripple requirements. When selecting an inductor, ensure both the average and peak current values are met with adequate margin.
CH4 (Green) : Inductor Current (500 mA per division) | CH1 (Blue) : SWx Node (20 V per division) | Time Base: 4µs per division |
CH4 (Green) : Inductor Current (500 mA per division) | CH1 (Blue) : SWx Node (20 V per division) | Time Base: 2µs per division |
TPS92518-Q1 Useful Equations:
Converter Output Equation (A) (Ideal)
Converter Output Equation (A) (With error sources)
Do:
Don't: