AAT4611 datasheet(8/10 Pages) AAT

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AAT4611

Current Limited Load Switch in SOT23 Package

4611.2006.09.1.4

Functional Block Diagram

Current

Limit

1.2V

Reference

Under-

Voltage

Lockout

Over-Temperature

Protection

OUT

SET

GND

SET

ON (ON)

Applications Information

Setting Current Limit

In most applications, the variation in ILIM must be

taken into account when determining RSET. The ILIM

variation is due to processing variations from part

to part, as well as variations in the voltages at IN

(Pin 5) and OUT (Pin 1) and the operating temper-

ature. See charts "Current Limit vs. Temperature"

and "Output Current vs. Output Voltage." Together,

these three factors add up to a ±25% tolerance

(see ILIM specification in Electrical Characteristics

section). In Figure 1, a cold device with a statisti-

cally higher current limit and a hot device with a

statistically lower current limit, both with RSET equal

to 10.5k

Ω, are shown. While the chart, "RSET vs.

ILIM" indicates an ILIM of 0.7A with an RSET of

10.5k

Ω, this figure shows that the actual current

limit will be at least 0.525A and no greater than

0.880A.

Figure 1: Current Limit Using 10.5k

Ω.

To determine RSET, start with the maximum current

drawn by the load and multiply it by 1.33 (typical ILIM

= minimum ILIM / 0.75). This is the typical current

limit value. Next, refer to "RSET vs. ILIM" and find the

RSET that corresponds to the typical current limit

value; choose the largest resistor available that is

less than or equal to it. For greater precision, the

value of RSET may also be calculated using the ILIM

RSET product found in the chart "RSET Coefficient vs.

0.2

0.4

0.6

0.8

1.2

234

Output Voltage (V)

0.88A

0.525A

Device With High Current Limit at -40

°C

Device With Low Current Limit at 85

°C

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