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AS1361-BTTT-18 Datasheet(PDF) 9 Page - ams AG |
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AS1361-BTTT-18 Datasheet(HTML) 9 Page - ams AG |
9 / 13 page www.austriamicrosystems.com Revision 1.00 9 - 13 AS1361/AS1362 Data Sheet - D e t a i l e d D e s c r i p t i o n 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 100k Ω 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) The maximum power dissipation is calculated: PDMAX = (TJ - TAMB)/( θJC + θCA)(EQ 2) Where: TJ - TAMB is the temperature difference between the AS1361/AS1362 die junction and the surrounding air; θJC is the thermal resistance of the package; θCA is the thermal resistance through the PC board/copper traces/other materials to the surrounding air. Note: Pin GND of the AS1361/AS1362 provides the electrical connection to system ground and also serves as a heat sink. Connect pin GND to the system ground using a large pad or ground plane. Noise Reduction The AS1361/AS1362 noise bypass circuitry dramatically reduces output noise, exhibiting 9µVRMS of output voltage noise with CBYPASS = 0.01µF and COUT = 1µF. Use an external 0.01µF bypass capacitor between pin BYPASS and pin OUT (see Figure 1 on page 1). Note: Startup time is minimized by internal power-on circuitry which pre-charges CBYPASS. |
Similar Part No. - AS1361-BTTT-18 |
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Similar Description - AS1361-BTTT-18 |
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