Functional description

L9733

18/35

DocID11319 Rev 12

4

Functional description

L9733 integrates 8 self-configuring outputs (OUT1-8) which are able to drive either

incandescent lamps, inductive loads (non-pwm'd, in pwm an external diode to reduce

flyback power dissipation is necessary), or resistive loads biased to Vbat (low-side

configuration) or to GND (high-side configuration). These outputs can be enabled and

disabled via the SPI bus. Each of these outputs has a short circuit protection (with

0.8-2.4 Amps threshold) selectable via SPI bus between a filtered switching OFF

overcurrent protection or a linear current limitation (default condition after power ON is

switching OFF protection enabled).

An over-temperature protection as described in Section 2.1 is available for each output.

When a high-side configured output is commanded OFF after having been commanded ON,

the source voltage will go to (VGND - 15 V). This is due to the design of the circuitry and the

transconductance of the MOSFET. When a low-side configured output is commanded OFF

after having been commanded ON, the output voltage will rise to the internal zener clamp

voltage (50 VDC minimum) due to the flyback of the inductive load.

Outputs 1-8 are able to drive any combination of inductive loads or lamps at one time.

Inductive loads for the L9733 can range from 35 mH to a maximum of 325 mH. The

recommended worst-case solenoid loads (at -40 °C) are calculated using a minimum

resistance of 40 Ω for each output. The maximum single pulse inductive load energy the

L9733 output is able to be safely handled is 20 mJ at -40 °C to 125 °C (Worst-case load of

325 mH and 40 Ω).

4.1

Configurations for outputs 1-8

The drain and source pins for each output must be connected in one of the two following

configurations (see Figure 7).

4.1.1

Low-side drivers

When any combination of outputs 1-8 are connected in a low-side drive configuration the

source of the applicable output (Src1-8) shall be connected to ground. The drain of the

applicable output (Drn1-8) shall be connected to the low-side of the load.

4.1.2

High-side drivers

When any combination of outputs 1-8 are connected in a high-side drive configuration the

drain of the applicable output (Drn1-8) shall be connected to Vbat. The source of the

applicable output (Src1-8) shall be connected to the high-side of the load.

4.2

Outputs 1-5

These five outputs can be used as either high or low-side drives. The room temperature

Rdson of these outputs is 0.7 Ω A current limited (100 μA max) voltage generator is

connected to Src 1-5 for open load and short to GND detection when a low-side configured

output is commanded OFF. Another current limited (100 μA max if VDrn 1-5 > 60 %Vbat,

280 μA max if VDrn 1-5 < 60 % Vbat) voltage generator is connected to Drn 1-5 for open

load and short to V bat detection when a high-side configured output is commanded OFF.