L9658 datasheet(36/64 Pages) STMICROELECTRONICS

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Functional description

L9658

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Doc ID 14219 Rev 3

Odd parity check includes all 16 bits. “Don’t care” bit is included in the parity check as well.

When bit D12 is set to ‘1,’ device executes bit D12 through bit D0. Otherwise, bit D12

through bit D0 is ignored. Diagnostic Mode Response is sent in the subsequent SPI

transmission regardless of bit D12.

The diagnostic currents comprise of diagnostic bias current (IBIAS) and resistance

measurement current (ISRC). Diagnostic bias current is used to run continuity tests, e.g.

short to battery, short to ground, and open circuit tests. During a resistance measurement,

ISRC and ISINK is turned on.

ISRC and ISINK are turned on when bit D8 is ‘1,’ bit D9 is ‘1,’ bit D11 is ‘0,’ and bit D12 is ‘1.’

Otherwise, ISRC and ISINK are off. When bit D11 is set to ‘1,’ MOS diagnostic is enabled.

Depending upon the state of bit D10, either a low side MOS or a high side MOS will be

switched on. When bit D 11 is set to ‘0,’ MOS diagnostic is disabled and bit D10 ignored.

When bit D9 is set to ‘1,’ a diagnostic current source is enabled. Bit D8 determine if IBIAS or

ISRC will be switched on. When bit D9 is set to ‘0,’ the diagnostic current sources is disabled

and bit D8 ignored. Bit D2 through bit D0 selects a specific channel, which will be

connected. The decoding scheme of this channel selection is shown ahead.

Continuity tests and MOS diagnostics are performed through comparators which set proper

bits on diagnostic register.

Differential amplifier used for squib resistance measure reflects the scaled voltage across

SQH and SQL pins. AOUT is connected to the differential amplifier.

Externally, AOUT pin will be connected to an ADC input of a processor. When bit D7 is set to

'1,' AOUT output is enabled. Otherwise, AOUT is in a high impedance state. Multiple devices

may be connected to a single ADC input of a processor. If an AOUT is driven, the rest of

AOUT shall be driven to the high-impedance state.

Diagnostic Current Disable (default)

Diagnostic Current Enable

Diagnostic Bias Current, IBIAS, Enable

Resistance Measurement Current, ISRC, Enable

AOUT Disable (default)

AOUT Enable

AOUT/Comparator Channel Select

AOUT: Resistance Measurement (default)

AOUT: Calibration

Diagnostic Current: Channel Select

Table 19.

MOSI diagnostic mode message definition (continued)

Bit

State

Description

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