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AS1341

Datasheet - A p p l i c a t i o n I n f o r m a t i o n

9.3 Setting Current Limit

The AS1341 adjustable peak current limit is set by connecting ILIMIT as shown in Table 4.

The current limit chosen should reflect the maximum load current. The maximum output current is half of the peak current limit. Choosing a lower

current limit allows using an inductor with a lower current rating, however, it requires a higher inductance (see Inductor Selection) and does not

allow for reduced inductor package size.

9.4 Inductor Selection

The AS1341 operates with a wide range of inductance values. For most applications, values between 10µH and 47µH work best with the

controller’s high switching frequency. Larger inductor values will reduce the switching frequency and thereby improve efficiency and EMI.

Note:

The four key factors in inductor selection are inductance value, saturation rating, series resistance, and size.

The trade-off for improved efficiency is a higher output ripple and slower transient response. On the other hand, low-value inductors respond

faster to transients, improve output ripple, offer smaller physical size, and minimize cost. If the inductor value is too small, the peak inductor

current exceeds the current limit due to current-sense comparator propagation delay, potentially exceeding the inductor’s current rating.

Calculate the minimum inductance value as follows:

(EQ 3)

Where:

The inductor saturation current rating must be greater than the peak switch current limit, plus the overshoot due to the 250ns current-sense

comparator propagation delay. Saturation occurs when the magnetic flux density of the inductor reaches the maximum level the core can support

and the inductance starts to fall. Choose an inductor with a saturation rating greater than IPEAK in the following equation:

(EQ 4)

Inductor series resistance affects both efficiency and dropout voltage (see Dropout Voltage on page 9). High series resistance limits the

maximum current available at lower input voltages, and increases the dropout voltage. For optimum performance, select an inductor with the

lowest possible DC resistance that fits in the allotted dimensions.

Table 4. Setting Peak Current Limit

Current Limit

ILIMIT Connected To

700mA

GND

1400mA

IN

Table 5. Recommended Inductors

Part Number

L

DCR

Current Rating

Manufacturer

MSS6132-103ML

10µH

85m

Ω

1.4A

Coilcraft

www.coilcraft.com

LPS4018-472ML

4.7µH

125m

Ω

1.8A

MSS6132-393ML

39µH

345m

Ω

0.8A

LPS4018-223ML

22µH

360m

Ω

0.7A

CDRH6D28NP-150

15µH

62m

Ω

1.4A

Sumida

www.sumida.com

CDRH5D18NP-4R1

4.1µH

57m

Ω

1.95A

CDRH6D28NP-470

47µH

176m

Ω

0.8A

CDRH5D18NP-220

22µH

215m

Ω

0.8A

LQH66SN-100M03

10µH

36m

Ω

1.6A

Murata

www.murata.com

LQH55DN-150M03

15µH

150m

Ω

1.4A

LQH66SN-470M03

47µH

170m

Ω

0.8A

LQH55DN-470M03

47µH

400m

Ω

0.8A