ATA6620 데이터 시트보기 (PDF) - Atmel Corporation

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ATA6620

LIN Bus Transceiver with Integrated Voltage Regulator

Atmel Corporation 

Figure 4-6. VCC Voltage Regulator: Ramp Up and Undervoltage

VS

12V

5.5V

3V

VCC

5V

Vthun

ATA6620

NRES

5V

TVCC

Tres

Tes_f

5. Fail-safe Features

• During a short circuit at LIN, the output limits the output current to IBUS_LIM. Due to the power

dissipation, the chip temperature exceeds TLINoff and the LIN output is switched off. The chip

cools down and after a hysteresis of Thys, switches the output on again. During LIN

overtemperature switch-off, the VCC regulator works independently.

• There are now reverse currents < 3 µA at pin LIN during loss of VBatt or GND. This is optimal

behavior for bus systems where some slave nodes are supplied from battery or ignition.

• During a short circuit at VCC, the output limits the output current to IVCCn. Because of

undervoltage, NRES switches to low and sends a reset to the microcontroller. The IC

switches into Pre–normal mode. If the chip temperature exceeds the value TVCCoff, the VCC

output switches off. The chip cools down and after a hysteresis of Thys, switches the output on

again. Because of Pre-normal mode, the VCC voltage will switch on again although EN is

switched off from the microcontroller.The microcontroller can then start with normal

operation.

• Pin EN provides a pull-down resistor to force the transceiver into recessive mode if EN is

disconnected.

• Pin RXD is set floating if VBatt is disconnected.

• Pin TXD provides a pull-up resistor to force the transceiver into recessive mode if TXD is

disconnected.

9

4850D–AUTO–02/06

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