LM5166DRCRG4 datasheet(29/57 Pages) TI2

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Load (mA)

0.01

0.1

100

500

100

D001

VIN = 8V

VIN = 12V

VIN = 24V

VIN = 36V

VIN = 65V

Load (mA)

0.01

0.1

100

500

4.9

4.92

4.94

4.96

4.98

5.02

5.04

5.06

5.08

5.1

D001

VIN = 8V

VIN = 12V

VIN = 24V

VIN = 36V

OUT

ESR

D 1 D

˜ '

OUT

ESR

D 1 D

LM5166

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SNVSA67B – DECEMBER 2016 – REVISED JUNE 2017

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8.2.1.2.7

Input Capacitor – CIN

An input capacitor is necessary to limit the input ripple voltage while providing switching-frequency AC current to

the buck power stage. To minimize the parasitic inductance in the switching loop, position the input capacitors as

close as possible to the VIN and GND pins of the LM5166. The input capacitors conduct a trapezoidal-wave

current of peak-to-peak amplitude equal to the output current. It follows that the resultant capacitive component

of AC ripple voltage is a triangular waveform. Together with the ESR-related ripple component, the peak-to-peak

input ripple voltage amplitude is given by Equation 26.

(26)

The input capacitance required for a particular load current, based on an input voltage ripple specification of

ΔVIN, is given by Equation 27.

(27)

The recommended high-frequency input capacitance is 2.2 μF or higher and should be a high-quality ceramic

component with sufficient voltage rating. Based on the voltage coefficient of ceramic capacitors, choose a

voltage rating of twice the maximum input voltage. Additionally, some bulk capacitance is required if the LM5166

circuit is not located within approximately 5 cm from the input voltage source. This capacitor provides damping to

the resonance associated with parasitic inductance of the supply lines and high-Q ceramics.

8.2.1.2.8

Soft-Start Capacitor – CSS

Connect an external soft-start capacitor for a specific soft-start time. In this example, select a soft-start

capacitance of 33 nF based on Equation 18 to achieve a soft-start time of 4 ms.

8.2.1.2.9

Application Curves

Unless otherwise stated, application performance curves were taken at TA = 25°C.

LF = 150 µH

COUT = 47 µF

FSW(nom) = 100 kHz

RRT = 309 kΩ

Figure 53. Converter Efficiency

LF = 150 µH

COUT = 47 µF

FSW(nom) = 100 kHz

RRT = 309 kΩ

Figure 54. Converter Regulation

LM5166DRCRG4 Datasheet(PDF) 29 Page - Texas Instruments

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