LM5166DRCT datasheet(35/53 Pages) TI1

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PGOOD

ILIM

VIN

HYS

GND

COUT

47 PF

4.7 PH

RFB1

169 k:

RFB2

100 k:

VIN = 4.5V...36V

VOUT = 3.3 V

CIN

2.2 PF

IOUT = 300 mA

RILIM

56.2 k:

LM5166

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SNVSA67A – DECEMBER 2016 – REVISED DECEMBER 2016

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8.2.3 Design 3: High-Density PFM Converter Rated at 3.3 V, 300 mA

Figure 68. Schematic for Design 3 with VIN(nom) = 24 V, VOUT = 3.3 V, IOUT(max) = 300 mA, 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)

Count Ref Des

Description

Part Number

MFR

CIN

Capacitor, Ceramic, 2.2 μF, 50 V, X5R, 10%, 1206

GRM31CR71H225KA88

Murata

COUT

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

GRM31CR60J476KE19

Murata

Inductor, 4.7 µH, 0.315 Ω typ, 2.2 A Isat, 1.2 mm max

TFM252012ALMA4R7TMAA

TDK

RILIM

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

Std

RFB1

Resistor, Chip, 169 kΩ, 1/16W, 1%, 0402

Std

RFB2

Resistor, Chip, 100 kΩ, 1/16W, 1%, 0402

Std

IC, Synchronous Buck Converter, VSON-10, ADJ

LM5166QDRCRQ1

8.2.3.2 Detailed Design Procedure

8.2.3.2.1

Feedback Resistors – RFB1, RFB2

The output voltage of the LM5166 is externally adjustable using a resistor divider network. The divider network

comprises the upper feedback resistor RFB1 and lower feedback resistor RFB2. Select RFB1 of 169 kΩ to minimize

quiescent current and improve light-load efficiency in this application. With the desired output voltage setpoint of

3.3 V and VFB = 1.223 V, calculate the resistance of RFB2 using Equation 15 as 99.5 kΩ. Choose the closest

available standard value of 100 kΩ for RFB2. Please refer to Adjustable Output Voltage (FB) for more detail.

8.2.3.2.2

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. Please refer to Adjustable Current Limit for more detail.

LM5166DRCT Datasheet(PDF) 35 Page - Texas Instruments

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