33874 datasheet(30/38 Pages) FREESCALE

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Analog Integrated Circuit Device Data

Freescale Semiconductor

33874

TYPICAL APPLICATION

DIAGNOSIS WITHOUT MCU

When any fault appears (over-current, open load…), a full

diagnosis can be reported via the SPI. Without an MCU, the

fault status pin allows reduced diagnosis, as illustrated in

table 3.

We can note that it is not possible to distinguish over

temperature, over-current, under-voltage, and over-voltage.

Nevertheless, Open load and short-circuit to VPWR fault can

be singled out. All protections are reported to Fault status pin

(FS), Open load and short-circuit to VPWR are reported only if

the Output is OFF. If the fault is latched, the output must be

turned OFF then ON to disable the fault.

CONCLUSION

Although the MC33874 is not fully functional without a

microcontroller to control and program it, standalone

functioning is safe because all protections are available.

Diagnosis is limited, but the fault status pin will report any

malfunction.

This is a good way to evaluate the main electrical

MC33874 features. Some simplified applications can also

use the MC33874 switch without an MCU to drive a high

power load with full protection.

Table 3. Diagnosis without SPI

IN[x] level

HS[x] level

FS level

Latched

Normal operation

N/A

Over-temperature

YES

Under-voltage

YES

Over-voltage

Over-current

YES

Short-circuit to VPWR

Open load

H : High Level, L : Low Level, Z : High-impedance, potential depends on the external circuit

33874 Datasheet(PDF) 30 Page - Freescale Semiconductor, Inc

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