33812 datasheet(20/25 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33812

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 VCLAMP_INJ. The total energy clamped (EJ)

can be calculated by multiplying the peak current (IPEAK)

times the clamp voltage (VCL) 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

Figure 5. Output Voltage Clamping

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.

Drain-to-Source Clamp

Voltage (VCL = 50 V)

Drain-to-Source ON

Voltage (VDS(ON))

Drain Voltage

Clamp Energy

EJ=(τ x IPEAK xVCL)/2

GND

Time

Drain Current

(IPEAK = 0.3 A)

33812 Datasheet(PDF) 20 Page - Freescale Semiconductor, Inc

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