AS1345B datasheet(18/29 Pages) AMSCO

18 / 29 page

AS1345 – 18

ams Datasheet, Confidential: 2013-Nov [1-51]

De tail ed De sc rip t ion

Power OK Operation

If desired the POK functionality can be used. In this case a

resistor R1 (~100k) has to be applied between the POK pin and

VIN, because the POK output is an open drain type. If the POK

functionality is not used the pin should be unconnected.

During shut-down the POK pin is high impedance to save

current. Therefore it shows VIN if connected to VIN with a

resistor or is floating otherwise. During start-up the POK goes

to LOW. During normal operation it is usually HIGH but it goes

to LOW if for some reason VOUT drops below 90% of the

nominal output voltage.

Thermal Shutdown

To prevent the AS1345 from short-term misuse and overload

conditions the chip includes a thermal overload protection. To

block the normal operation mode all switches will be turned

off. The device is in thermal shutdown when the junction

temperature exceeds 150°C typ. To resume the normal

operation the temperature has to drop below 140°C typ. A good

thermal path should be provided to dissipate the heat

generated within the package, especially at higher output

power. To dissipate as much heat as possible from the package

into a copper plane with as much area as possible, it’s

recommended to use multiple vias in the printed circuit board.

Continuing operation in thermal overload conditions may

damage the device, and therefore, is considered a bad practice.

AS1345B датащи(PDF) 18 Page - ams AG