U6268B Datasheet, PDF (6/14 Pages) TEMIC Semiconductors – Side-Airbag Sensor Dual Interface

3.8 GND Pins
A GND bond from the chip to pin 1 and pin 8 provides high ground breakage security and the
lowest voltage drop and ground shift between the IC and circuit ground. The four GND pins and
the die pad are directly connected to the copper leadframe, resulting in a very low thermal resis-
tance, R_thJC. To also achieve a low ambient thermal resistance (R_thJA) it is recommended metal
parts of the housing be connected in a proper way with the GND pins.
3.9 Power Dissipation
Worst case calculation of the supply current I_S:
I_S = 1.278 × (I_OUT1 + I_OUT2) + 18 mA
Worst case calculation of the IC's power dissipation P_V:
P_V = (V_S × I_S) – [(V_S – V_diff – V_ret-sat) × (I_OUT1 + I_OUT2) + R_OCM × ((I_OUT12 + I_OUT22)/81)]
3.10 Test Hint
V_S = Supply voltage (5.7 to 25V)
V_diff = V_S to V_OUTx voltage difference
V_diff = 3.6 V at 12 V ≤ V_S ≤ 25V
V_diff = 0.8 V at 5.7 V ≤ V_S ≤ 8.5V
V_ret-sat = 0.5 V saturation voltage return
I_OUTx = output current at pin OUTx = 0 to 60 mA
R_OCM = resistor at pin OCMx
An integrated overtemperature protection generates a switch-off signal at a chip temperature of
typically T_j = 160°C and a switch-on signal at typically T_j = 150°C.
If overtemperature is detected, only the corresponding channel will be disabled. The other chan-
nel stays enabled.
The RETURNx is switched off if the voltage at RETURNx exceeds 2V (short-circuit comparator
threshold) and overtemperature is detected.
The OUTx is switched off if the voltage at OCMx is higher than 4.6V (overcurrent detection level)
and overtemperature is detected. The OCM voltage monitors the output current at OUTx via the
current ratio of 0.1. The overcurrent-detection level of OUTx can be varied by changing the
OCMx resistor. If OUTx is switched off by overtemperature and overcurrent detection, the CLLx
output remains a logic low (overcurrent).
As the IC is only overtemperature-protected against short-circuit conditions at RETURNx or
OUTx, it has to be checked in each application that the chip temperature does not exceed
T_jmax = 150°C in normal operation.
The overtemperature signal can be activated by connecting ENABLE1 or ENABLE2 to
9V/10 mA.
6 U6268B
4808B–AUTO–09/05