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AS1341

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

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 propa-

gation 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 opti-

mum performance, select an inductor with the lowest possible DC resistance that fits in the allotted dimensions.

Maximum Output Current

The AS1341 output current determines the regulator’s switching frequency. When the converter approaches continu-

ous mode, the output voltage falls out of regulation. For the typical application, the maximum output current is approxi-

mately:

(EQ 5)

For low-input voltages, the maximum on-time may be reached and the load current is limited by:

(EQ 6)

Table 5. Recommended Inductors

Part Number

L

DCR

Current Rating

Circuit

Manufacturer

MSS6132-103ML

10µH

85m

Ω

1.4A

1, 4, 5

Coilcraft

www.coilcraft.com

LPS4018-472ML

4.7µH

125m

Ω

1.8A

2, 5

MSS6132-393ML

39µH

345m

Ω

0.8A

3, 5

LPS4018-223ML

22µH

360m

Ω

0.7A

4, 5

CDRH6D28NP-150

15µH

62m

Ω

1.4A

1, 5

Sumida

www.sumida.com

CDRH5D18NP-4R1

4.1µH

57m

Ω

1.95A

2, 5

CDRH6D28NP-470

47µH

176m

Ω

0.8A

3, 5

CDRH5D18NP-220

22µH

215m

Ω

0.8A

4, 5

LQH66SN-100M03

10µH

36m

Ω

1.6A

1, 5

Murata

www.murata.com

LQH55DN-150M03

15µH

150m

Ω

1.4A

1, 5

LQH66SN-470M03

47µH

170m

Ω

0.8A

3, 5

LQH55DN-470M03

47µH

400m

Ω

0.8A

3, 5