LM3243

SNVS782C – OCTOBER 2010 – REVISED AUGUST 2015

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The ACB circuit automatically adjusts its output current to keep the steady-state inductor current below the

steady-state peak current limit. Thus, the inductor RMS current will effectively always be less than the

bursts, the effective overall RMS current would be much lower.

For good efficiency, the inductor’s resistance should be less than 0.2

Ω; low DCR inductors (< 0.2 Ω) are

recommended. Table 3 suggests some inductors and suppliers.

Table 3. Suggested Inductors and Their Suppliers

MODEL

VENDOR

SIZE (mm)

DCR

DFE201610C-1R5M

TOKO

2 × 1.6 × 1

2.2 A

120 m

Ω

(1285AS-H-1R5M)

PSD20161T-1R5MS

CYNTEC

2 × 1.6 × 1

1.6 A

143 m

Ω

TFM201610-1R5M

TDK

2 × 1.6 mm × 1

2.2 A

140 m

Ω

8.2.2.2 Capacitor Selection

The LM3243 is designed to use ceramic capacitors for its input and output filters. Use a 10-µF capacitor for the

input and approximately 10-µF total output capacitance. Capacitor types such as X5R, X7R 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 suggested part numbers and suppliers. DC bias characteristics of

the capacitors must be considered while selecting the voltage rating and case size of the capacitor. Smaller case

sizes for the output capacitor mitigate piezo-electric vibrations of the capacitor when the output voltage is

stepped up and down at fast rates. However, they have a bigger percentage drop in value with DC bias. For

even smaller total solution size, 0402 case size capacitors are recommended for filtering. Use of multiple 2.2-µF

or 1-µF capacitors can also be considered. For RF Power Amplifier applications, split the output capacitor

recommended. The optimum capacitance split is application dependent, and for stability the actual total

capacitance (taking into account effects of capacitor DC bias, temperature de-rating, aging and other capacitor

close to the respective device. A high-frequency capacitor (3300 pF) is highly recommended to be placed next to

Table 4. Suggested Capacitors And Their Suppliers

CAPACITANCE

MODEL

SIZE (W × L) (mm)

VENDOR

10 µF

GRM185R60J106M

1.6 × 0.8

Murata

10 µF

CL05A106MQ5NUN

1 × 0.5

Samsung

4.7 µF

CL05A475MQ5NRN

1 × 0.5

Samsung

1.0 µF

CL03A105MQ3CSN

0.6 × 0.3

Samsung

3300 pF

GRM022R60J332K

0.4 × 0.2

Murata

8.2.2.3 Setting The Output Voltage

8.2.2.3.1

DAC Control

An analog voltage to the VCON pin can dynamically program the output voltage from 0.4 V (typical) to 3.6 V

(typical) in both PFM and PWM modes of operation, without the need for external resistors. The output voltage is

governed by Table 5.

Table 5. Output Voltage Selection

VCON (V)

VCON = 0.16V to 1.44V

2.5 × VCON

16

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