www.austriamicrosystems.com

Revision 1.02

13 - 18

AS1326

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

Inductor Selection

The AS1326A/AS1326B high switching-frequency allows the use of a small 3.3µH surface-mount inductor. The induc-

tor should generally have a saturation current rating exceeding the N-channel switch current limit; however, it is

acceptable to bias the inductor current into saturation by as much as 20% if a slight reduction in efficiency is accept-

able.

Lower current-rated inductors may be used if ISET is used to reduce the peak inductor current (see Setting the Switch

Current Limit on page 12). For high efficiency, select an inductor with a high-frequency ferrite core material to reduce

core losses. To minimize radiated noise, use a toroid or shielded inductor. Connect the inductor from the battery to the

pin LX as close to the device as possible.

External Schottky Diode

For output voltages greater than 4V, an external Schottky diode must be connected between pin LX and POUT, in par-

allel with the integrated synchronous rectifier (see Figure 25). The diode should be rated for 0.5A. An external diode is

also recommended for applications that must start with input voltages at or below 1.8V. The Schottky diode carries cur-

rent during startup and after the synchronous rectifier turns off; thus, its current rating only needs to be 500mA.

Note: Connect the diode as close to the IC as possible.

For circuits that do not require startup with inputs below 1.8V and have an output of 4V or less, the external

diode is not needed.

Caution: Do not use ordinary rectifier diodes as their slow switching speeds and long reverse-recovery times render

them unacceptable.

Table 7. Recommended Inductors

Part Number

L

DCR

Current Rating Dimensions (L/W/T)

Manufacturer

MOS6020-332

3.3µH

46m

Ω

1.8A

6.8x6.0x2.4mm

Coilcraft

www.coilcraft.com

LPS4018-332

3.3µH

80m

Ω

2.0A

4x4x1.8mm

DO1608C-272

2.7µH

80m

Ω

2.1A

6.6x4.45x2.92mm

CDRH5D18NP-4R1N

4.1µH

57m

Ω

1.95A

6x6x2mm

Sumida

www.sumida.com

76

78

80

82

84

86

88

90

92

94

96

0.1

1

10

100

1000

Output Current (mA)

MOS6020-332

DO1608C-272

CDRH5D18NP-4R1N

LPS4018-332

70

72

74

76

78

80

82

84

86

88

90

92

94

96

0.1

1

10

100

1000

Output Current (mA)

MOS6020-332

DO1608C-272

CDRH5D18NP-4R1N

LPS4018-332