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AS1324

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 total losses of the coil have a strong impact on the efficiency of the dc/dc conversion and consist of both the losses

in the dc resistance and the following frequency-dependent components:

1. The losses in the core material (magnetic hysteresis loss, especially at high switching frequencies)

2. Additional losses in the conductor from the skin effect (current displacement at high frequencies)

3. Magnetic field losses of the neighboring windings (proximity effect)

4. Radiation losses

Output Capacitor Selection

The advanced fast-response voltage mode control scheme of the AS1324 allows the use of tiny ceramic capacitors.

Because of their lowest output voltage ripple low ESR ceramic capacitors are recommended. X7R or X5R dielectric

output capacitor are recommended.

At high load currents, the device operates in PWM mode and the RMS ripple current is calculated as:

While operating in PWM mode the overall output voltage ripple is the sum of the voltage spike caused by the output

capacitor ESR plus the voltage ripple caused by charging and discharging the output capacitor:

Table 5. Recommended Inductors

Part Number

L

DCR

Current Rating Dimensions (L/W/T)

Manufacturer

LQH32CN2R2M33

2.2µH

97m

Ω

790mA

3.2x2.5x2.0mm

Murata

www.murata.com

LQH32CN4R7M33

4.7µH

150m

Ω

650mA

3.2x2.5x2.0mm

LPS3008-222MLC

2.2µH

175m

Ω

1100mA

3.1x3.1x0.8mm

Coilcraft

www.coilcraft.com

LPS3015-222MLC

2.2µH

110m

Ω

2000mA

3.1x3.1x1.5mm

MOS6020-222MLC

2.2µH

35m

Ω

3260mA

6.0x6.8x2.4mm

MOS6020-472MLC

4.7µH

50m

Ω

1820mA

6.0x6.8x2.4mm

CDRH3D16NP-2R2N

2.2µH

72m

Ω

1200mA

4.0x4.0x1.8mm

Sumida

www.sumida.com

CDRH3D16ND-4R7N

4.7µH

105m

Ω

900mA

4.0x4.0x1.8mm

70

75

80

85

90

95

1

10

100

1000

Output Current (mA)

LQH32CN2R2

LPS3008-222

LPS3015-222

M OS6020-222

LQH32CN4R7

M OS6020-472

70

75

80

85

90

95

1

10

100

1000

Output Current (mA)

LQH32CN2R2

LPS3008-222

LPS3015-222

M OS6020-222

LQH32CN4R7

M OS6020-472

(EQ 4)

I

RMSC

OUT

V

OUT

1

V

OUT

V

IN

--------------

–

Lf

×

------------------------

1

23

×

-----------------

×

×

=

(EQ 5)

ΔV

OUT

V

OUT

1

V

OUT

V

IN

--------------

–

Lf

×

------------------------

1

8C

OUT

×

f

×

--------------------------------

ESR

+

⎝⎠

⎛⎞

×

×

=