L9679P datasheet(208/272 Pages) STMICROELECTRONICS

208 / 272 page

General purpose output (GPO) drivers

L9679P

208/272

DocID029275 Rev 1

PWM control is based on a 125Hz frequency. 6 bits of GPOCTRLx are reserved to this

mode, in order to control the drivers with 64 total levels from a 0% to a full 100% duty cycle.

When both GPO channels are used in PWM Mode at the same frequency they are

synchronized to provide parallel configuration capability.

PWM control is implemented through a careful slew rate control to mitigate EMC emissions

while operating the interface. The driver output structure is designed to stand -1V on its

terminals and a +1V reverse voltage across source and drain.

The GPO driver is protected against short circuits and thermal overload conditions. The

output driver contains diagnostics available in the GPO Fault Status Register (GPOFLTSR).

All faults except for thermal overload will be latched until the GPOFLTSR register is read.

Thermal overload faults will remain active after reading the GPOFLTSR register should the

temperature remain above the thermal fault condition. For current limit faults, the output

driver will operate in a linear mode (ILIM) until a thermal fault condition is detected.

Figure 66. GPO Over temperature logic

The device offers also an open load diagnostics while in ON state. The diagnostics is run

comparing the current through the output stage with a reference threshold IOpenLoad: should

the output current be lower than the threshold, the open detection flag is asserted.

The device is also able to detect a fault condition during the OFF state by means of the

Voltage Regulator Current Monitor (VRCM) block. During the OFF state the VRCM block

tries to force a voltage VOUT_GPOx_OL (2.5 V) on GPOD pin if LS mode is selected (with a

current limitation of ILIM_GPOD_SRC/SINK) or on GPOS pin if the HS mode is selected (with a

current limitation of ILIM_GPOS_SRC/SINK) and, at the same, it compares the current sourced

or sunk in order to detect if a fault on GPO pins is present. The diagnostic in OFF state is

able to detect the open load in both HS and LS modes, the short to ground fault in LS mode

and the short to battery fault in HS mode:

Table 16. Short to ground fault in LS mode

LS MODE

GPOxSHORT GPOxOFFOPN

Interpretation

IOFF > ISRC_TH

Short to ground

- ISINK_TH_LS < IOFF < ISRC_TH

Open

IOFF < - ISINK_TH_LS

Normal

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