Datasheet

Normal Operation Transition Region Low Dropout Mode
E
Dropout
reduce dropout
Forced
off-time
Forced
off-time
Regulation
Point
ON-TIM CLK
VOUT VIN
f
SW(minDFC)
Extended
T
ON(max)
T
ON(max)
T
ON(maxDFC)
increased to
LM5088, LM5088-Q1
www.ti.com SNVS600H –DECEMBER 2008–REVISED MARCH 2013
Figure 18. Dropout Voltage Reduction using Dynamic Frequency Control
Frequency Dithering (LM5088-1 Only)
Electro-Magnetic Interference (EMI) emissions are fundamentally associated with switch-mode power supplies
due to sharp voltage transitions, diode reverse recovery currents and the ringing of parasitic L-C circuits. These
emissions will conduct back to the power source or radiate into the environment and potentially interfering with
nearby electronic systems. System designers typically use a combination of shielding, filtering and layout
techniques to reduce the EMI emissions sufficiently to satisfy EMI emission standards established by regulatory
bodies. In a typical fixed frequency switching converter, narrowband emissions typically peak at the switching
frequency with the successive harmonics having less energy. Dithering the oscillator frequency spreads the EMI
energy over a range of frequencies, thus reducing the peak levels. Dithering can also reduce the system cost by
reducing the size and quantity of EMI filtering components.
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