ATA6616_12 Datasheet, PDF (15/308 Pages) ATMEL Corporation – 8K/16K Flash Microcontroller with LIN Transceiver, 5V Regulator and Watchdog

Atmel ATA6616/ATA6617
3.5.5
3.5.6
Fail-safe Features
• During a short-circuit at LIN to V_Battery, the output limits the output current to I_{BUS_lim}. Due to
the power dissipation, the chip temperature exceeds T_LINoff, and the LIN output is switched
off. The chip cools down and after a hysteresis of T_hys, switches the output on again. RXD
stays on high because LIN is high. During LIN overtemperature switch-off, the VCC
regulator works independently.
• During a short-circuit from LIN to GND the IC can be switched into Sleep or Silent Mode. If
the short-circuit disappears, the IC starts with a remote wake-up.
• The reverse current is very low < 2µA at the LIN pin during loss of V_Batt. 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 I_{VCC_lin}. Due to
undervoltage, NRES switches to low and sends a reset to the microcontroller. The IC
switches into Fail-safe Mode. If the chip temperature exceeds the value T_VCCoff, the VCC
output switches off. The chip cools down and after a hysteresis of T_hys, switches the output
on again. Because of the Fail-safe Mode, the VCC voltage will switch on again even though
EN is switched off from the microcontroller. The microcontroller can start with its normal
operation.
• EN pin provides a pull-down resistor to force the transceiver into recessive mode if EN is
disconnected.
• RXD pin is set floating if V_Batt is disconnected.
• TXD pin provides a pull-up resistor to force the transceiver into recessive mode if TXD is
disconnected.
• If TXD is short-circuited to GND, it is possible to switch to Sleep Mode via ENABLE after
t_dom > 20ms.
• If the WD_OSC pin has a short-circuit to GND and the NTRIG Signal has a period time
> 27ms, the watchdog runs with an internal oscillator and guarantees a reset after the
second NTRIG signal at the latest.
• If the resistor at WO_OSC pin is disconnected, the watchdog runs with an internal oscillator
and guarantees a reseet after the second NTRIG signal at the latest.
Voltage Regulator
The voltage regulator needs an external capacitor for compensation and for smoothing the
disturbances from the microcontroller. It is recommended to use an electrolythic capacitor with
C ≥ 1.8µF and a ceramic capacitor with C = 100nF. The values of these capacitors can be
varied by the customer, depending on the application.
The main power dissipation of the IC is created from the VCC output current I_VCC, which is
needed for the application. In Figure 3-8 on page 16 the safe operating area of the Atmel^®
ATA6616/ATA6617 is shown.
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