L9908 datasheet(94/152 Pages) STMICROELECTRONICS

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Note:

The application software must configure T_ofd_blank to ensure that the motor is not running and the phases are

not energized. For some applications the maximum available T_ofd_blank configuration could be too short, the

application software then shall enable the OFD circuit with an additional delay after disabling the bridge drivers.

Table 87. OFD electrical characteristics

Symbol

Parameter

Test condition

Min

Typ

Max Unit

Notes

OFD_rvef

OFD phase reference voltage

in with no fault

OFDn_EN = 01

OFDi,j_EN = 10

2.7

3.1

OFD_vpd_ol

OFD open load voltage in pd

mode

OFDn_EN = 10

SHS_n = No load

0.9

OFD_ipu

OFD pull up current capability

OFDn_EN = 01

2.25

3.3

mA -

OFD_ipd

OFD pull down current

capability

OFDn_EN = 10

0.6

0.75

0.9

It includes an ILEAK

contribution

OFD_scb_th

OFD_SCB detection threshold -

SLS_n+1.7

Not subject to

production test

OFD_scg_th

OFD_SCG detection threshold -

VDH-0.7

Not subject to

production test

T_ofd_flt

OFD fault detection filter time

100

115

μs

Digital filter

T_ofd_blank_acc OFD Blanking Time accuracy

CLK_SSM_EN = 0 -15

Note:

All parameters are guaranteed, and tested, in the voltage ranges reported above in Table 5 unless otherwise

specified. Where not specified the parametrical operating range equals the functional operating range.

5.15

On State Diagnosis (OND)

L9908 implements a monitoring unit to detect failure condition affecting the load during the half bridges ON state

by monitoring the voltage drain-source drop across the Ext. FET.

The ON state diagnosis unit is composed by a dedicated VDS comparator for each HS and LS Ext. FET that

constantly monitors the voltage drop during FET`s ON state.

ON State Load Failure Mode Detection:

•

Short-circuit to ground at one SHS_n terminals → HSn_STG flag is set to 1

•

Short-circuit to battery at one SHS_n terminals → LSn_STB flag is set to 1

The ON state diagnosis can be disabled by a dedicated SPI bit as follows:

Table 88. OND enable bits

ONDn_DIS

Description

ON State diagnosis enabled on n-th HS and LS (Default)

ON State diagnosis disabled on n-th HS and LS

When the OND monitoring is disabled while having the fault flag set, the flag will not be cleared until SPI read.

If VDH-SHS_n ≥ V_ond_hs_th occurs for an interval longer than T_ond_flt filter time, the HSn_STG flag is set.

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

If SHS_n-SLSn ≥ V_ond_ls_th occurs for an interval longer than T_ond_flt filter time, the LSn_STB flag is set. The

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

L9908

Functional description

DS13546 - Rev 5

page 94/152

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