AS1364

Datasheet - Detailed Descr i pti on

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Revision 1.8

10 - 19

8.1 Output Voltage Selection

At the factory trimmed versions of the AS1364 offering the bypass pin (see Figure ), the output voltage is then set to an internally trimmed voltage

(see Ordering Information on page 18).

For the adjustable AS1364-AD, an output voltage between +1.2V and +5V can be set by using two external resistors (see Figure 17). In this

(EQ 1)

Where:

(EQ 2)

Since the input bias current at SET is less than 100nA, large resistance values can be used for R1 and R2 to minimize power consumption and

therefore increasing efficiency.

Note: Up to 125k

 is acceptable for R2. If the SET pin is connected to GND without a resistor, 3.3V will be set as output voltage.

In preset voltage mode, the impedance from SET to GND should be less than 10k

 or spurious conditions may cause the voltage at SET to

exceed the 50mV threshold.

Figure 17. Adjustable Output Voltage Typical Application

8.2 Shutdown

If pin EN is connected to GND the AS1364 is disabled. In shutdown mode all internal circuits are turned off, reducing supply current to 10nA

(typ). For normal device operation pin EN must be connected to IN. During shutdown, POK goes low.

When in shutdown, a 5k

 (typ) discharge path is connected between the output pin and ground.

8.3 Power-OK

The AS1364 features a power-ok indicator that asserts when the output voltage falls out of regulation. The open-drain POK output goes low

when output voltage at OUT falls 6% below its nominal value. A 100k

 pull-up resistor from POK to a (typically OUT) provides a logic control

signal.

POK can be used as a power-on-reset (POR) signal to a microcontroller or can drive an external LED to indicate a power failure condition.

Note: POK is low during shutdown.

1

------

+







=

--------------------- 1

–







=

AS1364

4.7µF

3

IN

5

OUT

2

EN

7

SET/BYP

4.7µF

Reset Output

On

Off

4

IN

1

POK

6

OUT

8

GND