LM3243

SNVS782B – OCTOBER 2010 – REVISED FEBRUARY 2013

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Table 3. Suggested Inductors and Their Suppliers

Model

Vendor

Size

DCR

DFE201610C-1R5M

TOKO

2.0 mm x 1.6 mm x 1.0 mm

2.2A

120 m

Ω

(1285AS-H-1R5M)

PSD20161T-1R5MS

CYNTEC

2.0 mm x 1.6 mm x 1.0 mm

1.6A

143 m

Ω

TFM201610-1R5M

TDK

2.0 mm x 1.6 mm x 1.0 mm

2.2A

140 m

Ω

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 actual 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

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

capacitors very close to the respective device. A high-frequency capacitor (3300 pF) is highly recommended to

Table 4. Suggested Capacitors and Their Suppliers

Capacitance

Model

Size (Wx L) (mm)

Vendor

10 µF

GRM185R60J106M

1.6 x 0.8

Murata

10 µF

CL05A106MQ5NUN

1.0 x 0.5

Samsung

4.7 µF

CL05A475MQ5NRN

1.0 x 0.5

Samsung

1.0 µF

CL03A105MQ3CSN

0.6 x 0.3

Samsung

3300 pF

GRM022R60J332K

0.4 x 0.2

Murata

EN Input Control

Use the system controller to drive the EN HIGH or LOW with a comparator, Schmitt trigger or logic gate. Set EN

= HIGH (>1.2V) for normal operation and LOW (<0.5V) for shutdown mode to reduce current consumption to

0.02 µA (typ.) current.

Startup

Next, EN should go HIGH (>1.2V). Finally, VCON should be set to a value that corresponds to the required

startup time and behavior of the output voltage, the LM3243 will always start up in PWM mode (even when

MODE = HIGH and output load current

≤ 75mA), then seamlessly transition into PFM mode.

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