L9658 datasheet(37/64 Pages) STMICROELECTRONICS

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L9658

Functional description

Doc ID 14219 Rev 3

37/64

The current sources (IBIAS and ISRC) and the AOUT/Comparators multiplexers are

independently selectable. These multiplexers can address the same channel or individual

channels. They cannot address multiple channels concurrently. It is not possible to source

diagnostic current to more than one channel at a time. The AOUT multiplexer also selects

the measurement channel for the short to ground SGth and short to battery SBth

comparators. Please see Figure 13 for the deployment driver diagnostic block diagram.

This flexibility in multiplexer addressing permits the detection of short between loops. To

detect a short, enable the diagnostic current, direct it to channel X and monitor the MISO

Diagnostic Mode Response bit D7 on the other channels. If no short exists between channel

X and the channel under measurement, the MISO Diagnostic Mode Response will report a

SQL voltage below SGth threshold (D7=1). If a short exists between channel X and the

channel under measurement, the MOSI Diagnostic Mode Response will report a SQL

voltage above SGth threshold (D7=0).

Diagnostic of multiple device, requires the ability to turn on a current source in one device,

while reading AOUT voltage of another device.

Use the MOSI Diagnostic Mode Message to configure the device and the MISO Diagnostic

Mode Response to measure the results. Table 19 and 20 define the MOSI Diagnostic Mode

Message and MISO Diagnostic Mode Response bits respectively.

Bit D6 through bit D4 selects a specific channel, which will be monitored. If AOUT output is

enabled, AOUT shall reflect the voltage on the selected channel. Also, SBTH and SGTH

status bits shall report the status of the respective channel. The decoding scheme of this

channel selection is shown in the following table. The default states of these bits are ‘0’

(channel 0 selected).

Bit D3 is used to calibrate AOUT. If this bit is set to ‘1,’ AOUT pin contains the calibration

voltage. The processor can use this calibration voltage to make adjustment to the

subsequent resistance measurement reading. This is intended to improve the accuracy of

the resistance measurement. When this bit is set to ‘0,’ AOUT pin contains the resistance

measurement results.

The default state of this bit is ‘0.’

Table 20.

Channel selection decoding

Bit D6

Bit D5

Bit D4

Channel Selected

Bit D2

Bit D1

Bit D0

000

001

010

011

100

101

110

111

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