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AS1326

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

Setting the Switch Current Limit

The ISET pin is used to adjust the inductor current limit and to implement the soft-start feature.

With pin ISET connected to pin REF, the inductor current limit is set to 1.6A. With ISET connected to a resistor-divider

network from pin REF to GND, the current limit is calculated as:

Soft Start

The soft-start feature can be implemented by placing a resistor between pin ISET and pin REF (see Figure 21) and a

capacitor between pin ISET and GND.

Figure 21. Circuit for Soft-Start with Maximum Switch Current Limit

At power-up, ISET is 0V and the LX current is zero. As the capacitor voltage rises, the current increases and the output

voltage rises. The soft-start time constant is:

Where:

≥ 220kΩ.

Note: Placing a capacitor across the lower resistor of the current-limiting resistor-divider network enables both the

current-limit and soft-start (see Figure 22).

Figure 22. Application Circuit for Soft-Start with Reduced Switch Current Limit

(EQ 2)

1,6A

1,25V

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

⎝⎠

⎛⎞

⋅

=

1

ISET

2

REF

AS1326A/

AS1326B

10nF

(EQ 3)

1

ISET

2

REF

AS1326A/

AS1326B

10nF

()