L9969X datasheet(38/70 Pages) STMICROELECTRONICS

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This principle only works at load currents above a certain threshold. If the load current is below that limit, the free

wheeling phase is too short to be detected correctly. This threshold is not specified here but it must be considered

in any case in order not to lead to a wrong diagnosis.

Once an OLDA was detected, the error has to be confirmed before being reported in DIA_REG1. The way

how the confirmation algorithm works, can be set in SPECIAL_REG, Bit4 (OLDAFILTER). Two alternatives are

possible: either the error has to be confirmed during the next possible retry, or the error has to be confirmed

during a retry after 40 ms.

5 V < VBATT < 18 V, 4.5 V < VDD < 5.5 V, TJ= -40 °C to 150 °C, unless otherwise specified.

Table 23. Under ground thresholds parameters

Symbol

Parameter

Condition

Min

Typ

Max

Unit

VUGND_OUTxy

Under ground threshold voltage at OUTxy

-0.25

-0.15

-0.05

OUTxy

3.2.6.10

Diagnosis in inactive mode

In inactive mode, i.e the HBR is disabled via the signals NABE or DIS, both the outputs OUT1 and OUT2 are

in the tristate condition (all four power transistors are switched off). In order to avoid any wrong diagnostic by

generated effects of the connected load, a filtering time tdiag_OL must have expired before the diagnosis is run.

In inactive mode, the following diagnostics are available: Open Load, Short to Ground and Short to Battery. At

power-up if load is not connected and OUTx1 is shorted to battery voltage or GND, the diagnosis detects SCG or

SCB and no OL.

Figure 25 shows how the OFF diagnosis is working, when the power-stage is disabled.

Figure 25. Principle of diagnosis in inactive mode

When the OFF state diagnosis is enabled, an internal buffer regulates a typical voltage of 1.8 V (VOFF_OUT1)

on OUTx1 pin, with a certain ISOURCE and ISINK capability, whose limits are equal to IOFF_LIM_SRC_OUT1 and

IOFF_LIM_SRC_OUT1 respectively; on OUTx2 is present pull-down current (IOFF_PD_OUT2), whose typical value is

120 µA.

If the load is connected and its resistance is below ROL, the buffer shall source a current equal to -IOFF_PD_OUT2,

so the diagnostic result is “no fault”.

If ISOURCE becomes higher than IOFF_OL_TH (lower in absolute value), it means that load is disconnected, or its

resistance has become more than ROL, so the diagnostic result is Open Load.

If ISOURCE becomes lower than IOFF_SCG_TH (higher in absolute value), it means that there is a short to ground.

L9969x

Functional behavior in detail

DS14029 - Rev 3

page 38/70

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