AS1361 Ver la hoja de datos (PDF) - austriamicrosystems AG

Número de pieza

componentes Descripción

Fabricante

AS1361

150mA/300mA, Ultra-Low-Noise, High-PSRR Low Dropout Regulators, with POK

austriamicrosystems AG 

AS1361/AS1362

Datasheet - Detailed Description

Figure 18. AS1361/AS1362 - Block Diagram

AS1361/AS1362

IN

SHDNN

BYPASS

GND

Shutdown and

Power-Down

Control

Thermal

Sensor

-

Error

Amp

+

1.25 Reference

and Noise Bypass

MOS

Driver w/

ILIMIT

–

95%

+

OUT

POK

Power-OK

The power-ok circuitry is built around an N-channel MOSFET. The circuitry monitors the output voltage and if the volt-

age goes out of regulation (e.g. during dropout, current limit, or thermal shutdown) pin POK goes low.

The power-OK feature is not active during shutdown and provides a power-on-reset (POR) function that can operate

down to VIN = 1V. A capacitor to GND may be added to generate a POR delay.

To obtain a logic-level output, connect a pull-up resistor from pin POK to pin OUT. Larger values for this resistor will

help minimize current consumption; a 100kΩ resistor is perfect for most applications (see Figure 1 on page 1).

Current Limit

The AS1361/AS1362 include a current limiting circuitry to monitor and control the P-channel MOSFET pass transis-

tor’s gate voltage, thus limiting the device output current to 270mA (AS1361) and 510mA (AS1362).

Note: See Table 4 on page 4 for the recommended min and max current limits. The output can be shorted to ground

indefinitely without causing damage to the device.

Thermal Protection

Integrated thermal protection circuitry limits total power dissipation in the AS1361/AS1362. When the junction temper-

ature (TJ) exceeds +160ºC, the thermal sensor signals the shutdown logic, turning off the P-channel MOSFET pass

transistor and allowing the device to cool down. The thermal sensor turns the pass transistor on again after the

device’s junction temperature drops by 10ºC, resulting in a pulsed output during continuous thermal-overload condi-

tions.

Note: Thermal protection is designed to protect the devices in the event of fault conditions. For continuous operation,

do not exceed the absolute maximum junction temperature rating of +150ºC.

Operating Region and Power Dissipation

The AS1361/AS1362 maximum power dissipation is dependant on the thermal resistance of the case and PCB, the

temperature difference between the die junction and TAMB, and airflow rate.

Power dissipation across the device is calculated as:

PD = IOUT (VIN - VOUT)

(EQ 1)

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Revision 1.03

10 - 15

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