NXP Semiconductors

21

33879

5.4.10 Output voltage clamp

Each output of the 33879 incorporates an internal voltage clamp to provide fast turn-off and transient protection of each output. Each

clamp independently limits the drain-to-source voltage to 45 V for low-side drive configurations and -20 V for high-side drive

configurations. The total energy clamped (EJ) can be calculated by multiplying the current area under the current curve (IA) times the

clamp voltage (VCL) (see Figure 18). Characterization of the output clamps, using a single pulse non-repetitive method at 0.35 A, indicates

the maximum energy per output to be 50 mJ at 150°C junction temperature.

Figure 18. Output Voltage Clamping

5.4.11 SPI configurations

The SPI configuration on the 33879 device is consistent with other devices in the Octal Serial Switch (OSS) family. This device may be

used in serial SPI or parallel SPI with the 33298 and 33291. Different SPI configurations may be provided. For more information, contact

NXP Analog Products Division or the local NXP representative.

5.4.12 Reverse battery

The 33879 has been designed with reverse battery protection on the VPWR pin. All outputs consist of a power MOSFET with an integral

substrate diode. During the reverse battery condition, current flows through the load via the substrate diode. Under this circumstance,

relays may energize and lamps turn on. Where load reverse battery protection is desired, a reverse battery blocking diode must be placed

in series with the load.

Current

Area (IA)

Clamp Energy

(EJ = IA x VCL)

Clamp Energy

(EJ = IA x VCL)

Drain Voltage

Source Voltage

Time

Time

BAT

Drain-to-Source Clamp

Voltage (VCL = 45 V)

Drain Current

(ID = 0.3 A)

GND

GND

VS

Drain-to-Source ON

Voltage (VDS(ON))

Drain-to-Source ON

Voltage (VDS(ON))

Current

Area (IA)

Source Current

(IS = 0.3 A)

Source Clamp Voltage

(VCL = -15 V)