L9908 datasheet(46/153 Pages) STMICROELECTRONICS

46 / 153 page

Note:

If no oscillator clock is available, the SPI data processing cannot work properly: L9908 delivers always the latest

answer.

5.10

Motor Battery Monitor (MBM)

L9908 implements a monitoring unit on the voltage level of the motor`s battery through the pin VDH with the

purpose of detecting over-voltage events that can harm the device and under-voltage events that can prevent a

correct motor driving. Hysteresis on thresholds and filtering time are implemented.

If VDH ≤ VDH_uv_th occurs for an interval longer than T_vdh_uv_flt filtering time, VDH_UV flag is set. The error

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

If VDH ≥ VDH_ov_th occurs for an interval longer than T_vdh_ov_flt filtering time, VDH_OV flag is set. The error

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

The correct level of motor`s battery stage monitor is safety relevant and then a self-check procedure is

implemented on its monitor.

The under-voltage thresholds VDH_uv_th can be configured by dedicated SPI bits as follows:

Table 39. Motor battery monitor UV threshold configuration bits

VDH_UV_CFG1

VDH_UV_CFG0

Description

12 V Systems (Defaults)

24 V Systems

48 V Systems

VDH UV Disabled

The over-voltage threshold VDH_ov_th can be configured by dedicated SPI bits as follows:

Table 40. Motor battery monitor OV threshold configuration bits

VDH_OV_CFG2

VDH_OV_CFG1

VDH_OV_CFG0

Description

12 V Systems 1

12 V Systems 2

24 V Systems 1

24 V Systems 2

48 V Systems 1

48 V Systems 2

48 V Systems 3

48 V Systems 4 (Defaults)

The filter time on under/over voltage diagnosis T_vdh_uv_flt/ T_vdh_ov_flt can be configured by dedicated SPI

bits as follows:

Table 41. Motor battery monitor filtering configuration bits

VDH_FLT_CFG1

VDH_FLT_CFG0

Description

12.25 μs (Defaults)

25 μs

50 μs

100 μs

L9908

Motor Battery Monitor (MBM)

DS13546 - Rev 3

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