Rainbow Electronics ATA6626 - Manual (Page 6)

6
4970A–AUTO–01/07
ATA6621/22/24 Development Board
2.5 Temp Pin (TEMP) (ATA6621 Only)
Besides the internal temperature monitoring of the voltage regulator, an additional sensor
measures the junction temperature and provides a linearized voltage at the TEMP pin.
Together with the analog functions of the microcontroller (for example, the analog comparator
and/or the analog-to-digital converter), this enables the application to detect overload condi-
tions. Further actions in order to prevent the IC from damage can be implemented.
2.6 Mode and TM Input Pins (MODE and TM)
The TM input is only used for Atmel ® internal-testing purposes and therefore connected
directly to GND. The Mode input is pulled to GND by the 4.7-k
Ω
resistor R1 and therefore the
watchdog is active in the normal operation mode. Especially during the early development
phase it can be helpful to have the possibility to deactivate the watchdog in order to debug the
application program without disturbing RESETS caused by the watchdog. Therefore the
watchdog can be switched off by connecting the MODE pin to VCC externally.
2.7 Reset Output (NRES)
After ramping up the battery voltage or after a wake-up from Sleep mode, the 5V regulator is
switched on and the VCC voltage exceeds the undervoltage threshold. The implemented und-
ervoltage delay keeps the NRES output at low level for approximately 10 ms after VCC
reaches its nominal value. Then it switches to high and the watchdog waits for the trigger
sequence from the microcontroller.
The NRES pin switches to low if the watchdog is not triggered correctly (see Section 2.3 on
page 4 ).
In the ATA6621 the Reset output is a push-pull state supplied by the VCC voltage.
In the ATA6622 and ATA6624, the Reset output is an open drain output implemented with a
single MOS transistor which is switched on in case of a VCC undervoltage or if the watchdog
is not triggered correctly. In order to pull up the NRES output of the ATA6622/24 an external
resistor connected to VCC
is necessary. This resistor (R9) is taken into account on the devel-
opment board.
If a reset occurs (NRES is Low), the circuit switches to Pre-normal mode (Fail Safe mode).
2.8 KL_15 Input (KL_15) (ATA6622/24 Only)
This pin is a high voltage input used to wake up the device from Sleep or Silent mode. It is an
edge sensitive pin (rising edge). It is usually connected to the ignition in order to generate a
local wake-up in the application if the ignition is switched on. To protect the pin against voltage
transients, a series resistor R12 and a 100-nF ceramic capacitor C8 have to be used. If this
pin is not needed, it must be connected to GND.
2.9 Inhibit Output (INH) (ATA6622/24 Only)
This pin is a high-side switch and it is normally used to switch on an external voltage regulator
during Normal mode or Fail Safe mode. In Sleep mode or Silent mode the INH output is
switched off.
For master node applications it is possible to switch off the external master resistor (R4) by the
INH pin.