L9908 datasheet(90/152 Pages) STMICROELECTRONICS

90 / 152 page

Symbol

Parameter

Min Typ Max

Unit

Notes

1.2

1. Measurement setup: Tj = 25⁰C IS+n = IS-n, RLP = 1 kΩ; CLP = 270 pF; VOFS = 2.5 V. Measured after low pass filter.

5.14

Off-State diagnosis (OFD)

L9908 implements a monitoring unit to detect failure conditions affecting the load during the half bridge tristate

condition (VGHn - VSHn = 0 V and VGLn - VSLn = 0 V).

Load failure mode detection:

•

Open load at one of the SHS_n terminals;

•

Short-circuit to ground at one or multiple SHS_n terminals;

•

Short-circuit to battery at one or multiple SHS_n terminals.

Each error flag remains set until the failure condition is removed and the flag is cleared by the SPI command.

Figure 65. OFF State diagnosis simplified block diagram

The off state diagnosis unit is composed by a multiple force stage and a multiple monitor stage.

The force stage has the purpose of driving the state of each SHS_n terminal into a predetermined voltage

condition, any deviation from this condition is then detected by the monitor stage and interpreted as a faulty

condition.

The force stage is composed by a protected controlled pull-up/pull-down current source for each phase

respectively towards V3V3_A and SGND.

The monitor stage is composed by the LS VDS and the HS VDS comparators which compare the n-th phase

voltage with respectively OFD_SCB_TH and OFD_SCG_TH fixed thresholds.

The n-th phase OFD unit can be enabled/disabled by dedicated SPI bits as follows:

Table 84. OFD enable bits

OFDn_EN1

OFDn_EN0

Description

Off State diagnosis disabled (Default)

L9908

Functional description

DS13546 - Rev 5

page 90/152

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