LM5166DRCT datasheet(35/57 Pages) TI2

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OUT

SW(PFM)

PK(PFM)

˜ ¨

PGOOD

ILIM

VIN

HYS

GND

VOUT

COUT

4.7 PH

VIN = 4.5 V...36 V

VOUT = 3.3 V

CIN

IOUT = 0.3 A

RILIM

56.2 k:

47 PF

4.7 PF

LM5166Y

LM5166

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SNVSA67B – DECEMBER 2016 – REVISED JUNE 2017

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8.2.3 Design 3: High-Density PFM Converter Rated at 3.3 V, 0.3 A

Figure 70. Schematic for Design 3 With VIN(nom) = 24 V, VOUT = 3.3 V, IOUT(max) = 0.3 A, FSW(nom) = 600 kHz

8.2.3.1 Design Requirements

The target efficiency is 75% for loads above 10 mA based on a nominal input voltage of 24 V, an output voltage

of 3.3 V, with the emphasis on small solution size. The required input voltage range is 4.5 V to 36 V. The

LM5166 has an internally-set soft-start time of 900 µs and an adjustable peak current limit threshold. The

required components are listed in Table 6.

(1)

See Third-Party Products Disclaimer.

Table 6. List of Components for Design 3(1)

COUN

REF

DES

DESCRIPTION

PART NUMBER

MFR

CIN

Capacitor, Ceramic, 4.7 μF, 50 V, X7R, 10%, 1206

GRM31CR71H475MA12L

Murata

885012208094

Würth

COUT

Capacitor, Ceramic, 47 μF, 6.3 V, X5R, 10%, 1206

GRM31CR60J476KE19

Murata

Inductor, 4.7 µH, 0.18 Ω typ, 2.2 A Isat, 1.2 mm max

TFM252012ALMA4R7TMAA

TDK

Inductor, 4.7 µH, 0.3 Ω typ, 2.1 A Isat, 1.2 mm max

Würth

RILIM

Resistor, Chip, 56.2 kΩ, 1/16W, 1%, 0402

Std

LM5166Y, Synchronous Buck Converter, VSON-10, 3.3-V Fixed

LM5166YDRCR

8.2.3.2 Detailed Design Procedure

8.2.3.2.1

Peak Current Limit Setting – RILIM

Install a 56.2-kΩ resistor from ILIM to GND to select a 750-mA peak current limit threshold setting to meet the

rated output current of 300 mA in PFM. See Adjustable Current Limit for more detail.

8.2.3.2.2

Switching Frequency – LF

Tie RT to GND to select PFM mode of operation. The inductor, input voltage, output voltage and peak current

determine the pulse switching frequency of a PFM-configured LM5166. For a given input voltage, output voltage

and peak current, the inductance of LF sets the switching frequency when the output is in regulation. Use

Equation 28 to select an inductance of 4.7 μH based on the target PFM converter switching frequency of 600

kHz at 24-V input.

(28)

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