AS1339 datasheet(21/25 Pages) AMSCO

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AS1339

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

Example

The following system should be designed:

- A supply with a Lithium-Ion Battery = 4.5V

-VOUT = 3.0V

IOUTMAX = 500mA

For the first step VREF is calculated as shown in Equation (EQ 5).

Due to Equation (EQ 6): VIN = 3.23V

If VIN is falling below 3.23V the device is going into Bypass mode (see Bypass Mode on page 17).

Hence a 2.2µH coil is used,

ΔIL can be calculated with Equation (EQ 3): ΔIL= 227mA

With this result IMAX can be calculated with Equation (EQ 4): IMAX = 614mA.

The saturation current of the coil should be chosen slightly higher than IMAX because heavy load transients could

increase the peak current. For a short period of time (~50µs) the peak inductor current can rise up to a value of approx-

imately 1.1A (p-channel MOSFET peak current limit). In this case a coil with a rated saturation current of ~800mA can

be chosen.

Figure 52. Efficiency Comparison of different

Inductors; VIN = 3.9V, VOUT = 1.0V

Figure 53. Efficiency Comparison of different

Inductors; VIN = 3.9V, VOUT = 1.5V

100

1000

Output Current (mA)

MLP2520S1R5S

MLP2520S2R2S

MLP2520S3R3S

EPL2014-222

EPL2014-332

EPL2014-472

100

1000

Output Current (mA)

MLP2520S1R5S

MLP2520S2R2S

MLP2520S3R3S

EPL2014-222

EPL2014-332

EPL2014-472

(EQ 5)

REF

OUT

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

12V

(EQ 6)

269

REF

≤

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