Rainbow Electronics ATA6823 - Manual (Page 6)

6
4856E–AUTO–07/07
ATA6823 [Preliminary]
5.1.2 Voltage Supervisor
This block is intended to protect the IC and the external power MOS transistors against overvolt-
age on battery level and to manage undervoltage on it.
Function: in case of both overvoltage alarm (V
THOV
) and of undervoltage alarm (V
THUV
) the exter-
nal NMOS motor bridge transistors will be switched off. The failure state will be flagged via DG2.
No other actions will be carried out. The voltage supervision block is connected to VBAT and fil-
tered by a first-order low pass with a corner frequency of typical 15 kHz.
5.1.3 Temperature Supervisor
There is a temperature sensor integrated on-chip to prevent the IC from overheating due to a
failure in the external circuitry and to protect the external NMOSFET transistors.
In case of detected overtemperature (150°C), the diagnostic pin DG3 will be switched to “H” to
signalize this event to the microcontroller. It should undertake actions to reduce the power dissi-
pation in the IC. In case of detected overtemperature (165°C), the V
CC
regulator and all drivers
including the LIN transceiver will be switched OFF immediately and /RESET will go LOW.
Both temperature thresholds are correlated. The absolute tolerance is ±10°C and there is a
built-in hysteresis of about 10°C to avoid fast oscillations. After cooling down below the 155°C
threshold; the IC will go into Active mode.
The LIN interface has a separate thermal shutdown with disabled the low-side driver at typically
165°C.
5.2 Sleep Mode
To be able to guarantee the low quiescent current of the inactive IC, a Sleep mode is estab-
lished. In Sleep mode it is possible to wake-up the IC by using the pins EN2 or LIN. In Sleep
mode, the following blocks are active:
• Band gap
• Internal 5V regulator (VINT) with external blocking capacitor of 220 nF
• Input structure for detecting the EN2 pins threshold
• Wake-up block of the LIN receive part
5.3 Wake-up and Sleep Mode Strategy
The IC has two modes: Sleep and Active. The change between the modes is described below.
The default state after power-on is Active mode.
The wake-up procedure brings the IC from a standby mode (Sleep) to an active mode (Active).
The internal 5V supply VINT, the EN2 pin input structure and a certain part of the LIN receiver
are permanently active to ensure a proper startup of the system.
The Go to Active and Go to Sleep procedures are implemented as follows:
• Go to Active by activating pin EN2
The input EN2 is intended as a switch-on pin from an external signal. Its input structure consists
of a comparator with built-in hysteresis. It is ESD-protected by diodes against GND and V
BAT
; for
this reason the input voltage level must be positive and not higher than V
BAT
.