ATA6621N-PGPW(2007) Ver la hoja de datos (PDF) - Atmel Corporation

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Fabricante

ATA6621N-PGPW
(Rev.:2007)

LIN Transceiver with 5V Regulator and Watchdog

Atmel Corporation 

ATA6621N

• If the WD_OSC pin has a short circuit to GND or the resistor is disconnected, the watchdog

oscillator runs with a high frequency and guarantees a reset. In order to activate this feature

in any condition it is recommended to enter the Silent mode (via the Normal mode) directly

after power up.

• The WD_OSC pin is a constant voltage regulator which supplies 2.5V for the external resistor

ROSC to adjust the watchdog timing. This output is short circuit protected. A short circuit to

GND causes a reset a pin NRES after typically 4 ms. An open circuit causes a reset at pin

NRES after typically 7 ms.

3.18

Voltage Regulator

The voltage regulator needs an external capacitor for compensation and to smooth the distur-

bances from the microcontroller. It is recommend to use an tantalum capacitor with C > 10 µF

and a ceramic capacitor with C = 100 nF. The values of these capacitors can be varied by the

customer, depending on the application.

During mode change from Silent to Normal mode, the voltage regulator ramps up to 6V for only

a few microseconds before it drops back to 5V. This behavior depends on the value of the load

capacitor. With 4.7 µF, the overshoot voltage has its greatest value. This voltage decreases with

higher or lower load capacitors.

The main power dissipation of the IC is created from the VCC output current IVCC, which is

needed for the application.

In Figure 3-8 on page 14 you see the safe operating range of the ATA6621N.

Figure 3-7. VCC Voltage Regulator: Ramp Up and Undervoltage

VS

12V

5.5V

3V

VCC

5V

Vthun

NRES

5V

tvcc

tres

t

tres_f

t

t

13

4887H–AUTO–12/07

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