33812 Datasheet, PDF (20/25 Pages) Freescale Semiconductor, Inc – SMALL ENGINE CONTROL IC

TYPICAL APPLICATIONS
ISO-9141 TRANSCEIVER OPERATION
TYPICAL APPLICATIONS
Low Voltage Operation
During a low voltage condition (4.5 V < VPWR < 9.0 V) the
device will operate as described in the functional description,
however, certain parameters listed in the tables may be out of
specification. Fault condition annunciation is not guaranteed
below the minimum parametric operating voltage.
Low Side Injector Driver Voltage Clamp
The Injector output of the 33812 incorporates an internal
voltage clamp to provide fast turn OFF and transient
protection. Each clamp independently limits the drain-to-
source voltage to V_{CLAMP_INJ}. The total energy clamped (E_J)
can be calculated by multiplying the peak current (I_PEAK)
times the clamp voltage (V_CL) times the Time (τ) all divided by
2 (see Figure 5).
Characterization of the output clamp, using a repetitive
pulse method at 1.0 A, indicates the maximum energy to be
100 mJ at 125°C junction temperature per output
.
Drain-to-Source Clamp
Voltage (V_CL = 50 V)
Drain Current
(I_PEAK = 0.3 A)
Drain Voltage
Clamp Energy
E_J=(τ x I_{PEAK x}V_CL)/2
Drain-to-Source ON
Voltage (V_DS(ON))
GND
τ
Figure 5. Output Voltage Clamping
Time
Reverse Battery and Transient Protection
The 33812 device requires external reverse battery
protection on the VPWR pin.
All outputs consist of a power MOSFET with an integral
substrate diode. During a reverse battery condition, current
will flow through the load via the substrate diode. Under this
condition load devices will turn on. If reverse battery
protection for the loads is required, a diode must be placed in
series with the load.
Good automotive engineering practices recommend the
use of transient voltage suppression on the VPWR line. A
TVS device and adequate capacitive decoupling are
necessary for a robust design.
33812
20
Analog Integrated Circuit Device Data
Freescale Semiconductor