LM3262 datasheet(17/41 Pages) TI1

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ISAT > IOUT_MAX + IRIPPLE

VOUT

VIN

VIN - VOUT

2 x L

IRIPPLE =

where

LM3262

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SNVS875O – AUGUST 2012 – REVISED DECEMBER 2015

8.2.2.1.1

Method 1

The saturation current must be greater than the sum of the maximum load current and the worst-case average-

to-peak inductor current. This is shown in Equation 1 :

where

•

IRIPPLE: average-to-peak inductor current

•

IOUT_MAX: maximum load current (800 mA)

•

VIN: maximum input voltage in application

•

L: minimum inductor value including worst-case tolerances (30% drop can be considered for Method 1)

•

F: minimum switching frequency (5.7 MHz)

•

VOUT: output voltage

(1)

8.2.2.1.2

Method 2

A more conservative and recommended approach is to choose an inductor than can handle the maximum

current limit of 1600 mA.

The resistance of the inductor must be less than 0.1

Ω for good efficiency. Table 3 lists suggested inductors and

suppliers.

Table 3. Suggested Inductors

MODEL

SIZE (W × L × H) (mm)

VENDOR

LQM21PNR50XGHL11

2 × 1.25 × 1

Murata

MIPSZ2012D0R5

2 × 1.2 × 1

FDK

LQM21PNR54MG0

2 × 1.25 × 0.9

Murata

LQM2MPNR47NG0

2 × 1.6 × 0.9

Murata

CIG21LR47M

2 × 1.25 × 1

Samsung

CKP2012NR47M

2 × 1.25 × 1

Taiyo Yuden

8.2.2.2 Capacitor Selection

The LM3262 is designed for use with ceramic capacitors for its input and output filters. Use a 10-µF ceramic

capacitor for input and a sum total of 4.7-µF ceramic capacitance for the output. They should maintain at least

50% capacitance at DC bias and temperature conditions. Ceramic capacitors types such as X5R, X7R, and B

are recommended for both filters. These provide an optimal balance between small size, cost, reliability, and

performance for cell phones and similar applications. Table 4 lists some suggested part numbers and suppliers.

DC-bias characteristics of the capacitors must be considered when selecting the voltage rating and case size of

the capacitor. If it is necessary to choose a 0603 (1608) size capacitor for VIN and 0402 (1005) size capacitor for

VOUT, the operation of the LM3262 must be carefully evaluated on the system board. Use of a 2.2-µF capacitor in

conjunction with multiple 0.47-µF or 1-µF capacitors in parallel may also be considered when connecting to

power amplifier devices that require local decoupling.

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