JAJSJZ4B October 2020 – June 2024 TPS54J061
PRODUCTION DATA
The switching frequency and light load mode of operation are configured by the resistor on the MODE pin. From Table 6-1, the MODE pin is connected to VCC to set a 1100-kHz switching frequency with discontinuous conduction mode and skip mode enabled at light loads.
When selecting the switching frequency of a buck converter, the minimum on-time and minimum off-time must be considered. Equation 6 calculates the maximum fSW before being limited by the minimum on-time. When hitting the minimum on-time limits of a converter with D-CAP3 control mode, the effective switching frequency will change to keep the output voltage regulated. This calculation ignores resistive drops in the converter to give a worst case estimation.
Equation 7 calculates the maximum fSW before being limited by the minimum off-time. When hitting the minimum off-time limits of a converter with D-CAP3 control mode, the operating duty cycle will max out and the output voltage will begin to drop with the input voltage. This equation requires the DC resistance of the inductor, RDCR, selected in the following step so this preliminary calculation assumes a resistance of 10 mΩ. If operating near the maximum fSW limited by the minimum off-time, the variation in resistance across temperature must be considered when using Equation 7. The selected fSW of 1100 kHz is below the two calculated maximum values.