E981.18A39FB ELMOS Semiconductor, E981.18A39FB Datasheet - Page 34

• Manufacturer Part Number: E981.18A39FB
• Description: Motor / Motion / Ignition Controllers & Drivers 8ch squib driver
• Manufacturer: ELMOS Semiconductor
• Type: Airbag Squib Driverr

Specifications of E981.18A39FB

• Rohs: yes
• Product: Electromechanical Drivers
• Operating Supply Voltage: 5 V
• Supply Current: 4.3 mA
• Operating Temperature: - 40 C to + 95 C
• Mounting Style: SMD/SMT
• Package / Case: QFN-44
• Number Of Outputs: 8
• Power Dissipation: 3.2 W

8-Channel Airbag Squib Driver
PRELIMINARY INFORMATION - AUG 01, 2011
Measurement principle:
The I
the squib-lines TxU. The current loop in the squib-path can be closed by activating the Low Side Driver
(LSD) connected to the according TxL pin under test mode (TM) condition. The current limitation of the
LSD in TM is always larger than the internal 40mA current source. Because of the over voltage
detection at the TxL pins in TM (T
first the LSD and then the current source at the according TxU pin. Otherwise the OV condition
at the TxL pin will prevent the driver activation.
The current loop of the external reference resistor RREF is given by the grounded structure itself.
The difference voltage drop of RREF and of the squib-resistors can be switched by the multiplexors S2
and S3 to the internal amplifier. The amplifier output is visible at the AMX-pin.
For the voltages at the amplifier inputs following equations are valid:
1) I
2) I
At all TxU and TxL pins, polarization units are connected inside the IC, used for the leakage
measurements and to avoid floating nodes at the squib feed and squib return lines. These polarization
units consists of a buffer, forcing a bias voltage over a 1.3kΩ resistor to the TxL and TxU lines. Due to
the fact that the LSD activation in TM will cause a CMIR of the measurement close to GND-level, the
polarization buffer at the HSD would contribute an additional error current into the squib.
To eliminate this, the buffer of the selected TxU is disabled automatically by the same SPI-CMD, which
activates the I
The buffer output current of the TxL polarization unit will shift the CMIR range of the measurement, but
will not influence the difference voltage measurements. Consequently the buffer at the TxL is not
disabled.
Detection of an open Power Ground (PGND):
The 40mA current source can be used to detect a bond wire demolition at each LSD PGND pin. In this
case the ESD diode between internal PGND pad and system Ground (SGND) will trace the I
current source. Each LSD Source Pin is only connected by a bond-wire to the according external PGND
pin. There is no galvanic path to system ground SGND via substrate. Due to ESD protection each LSD
Source pin has got a own protection circuitry of one diode in forward and one diode in backward
direction to the system ground SGND. This is sketched in Fig. 18, too. Consequently the voltage drop at
the TxL pin will be enlarged by a voltage U
missing. Each TxL voltage can be switched to the AMX buffer by the according SPI-CMD. (see chapter
5.14). Thus following equations are valid for PGND connected and PGND not connected:
1) V- =V
2) V- =V
R
This document contains information on a pre-production product. ELMOS Semiconductor AG reserves the right to change specifications and information herein without notice.
ELMOS Semiconductor AG
ON_LSD
with R
REF40mA
REF40mA
REF40mA
is given in chapter 5.12.1, here the TxL and PGND bond wires are included.
AMX
AMX
BOND_MAX
→ RREF;
→TxU;
reference current source can be switched by multiplexor S4 to the external pin RREF or to
= I
= I
REF40mA
REF40mA
REF40mA
=100mΩ, given by design, not tested during production test.
at the selected channel (see chapter 5.14 for the SPI-CMD-list).
∙(R
∙(R
ON_LSD
ON_LSD
V
V
+
+
→ RREF;
→ TxU;
) for PGND connected
+U
D
) for PGND not connected
OV_BLNK_TxL_TM
V
V
-
-
D
→ GND
→ TxL
(0.3V..0.9V) of the ESD forward diode, if the bond wire is
Page 34 of 63
Data Sheet
=0, see chapter 5.12.2) it is mandatory to activate
: (V
: (V
+
+
- V
- V
-
-
) = I
) = I
REF40mA
REF40mA
∙(R
∙(R
BOND_RREF
BOND_TxU
QM-No.: 25DS0072E.00
+ R
+RREF)
BOND_TxL
E981.18
REF40mA
+ R
SQUIB
)