L9908 datasheet(102/152 Pages) STMICROELECTRONICS

102 / 152 page

5.18

Ground Loss Monitor (GLM)

L9908 implements two ground reference pins, a Power Ground (PGND) dedicated as reference for the noisy, high

power gate supply circuitry (CP1, CP2) and a Signal Ground (SGND) dedicated to the low power internal analog/

digital circuitry.

For EMI robustness the GND pin is internally split in two GND reference PADs: GND_ANA (ground reference for

analog circuitry supplied from V3V3_ANA) and GND_DIG (ground reference for digital circuitry supplied by

V3V3_DIG), GND_ANA is connected to the ESD GND ring by means of a direct metal connection and bias the

substrate through SUB Plugs placed all around IC border.

GND_ANA and PGND are connected to the ESD GND by means of a standard ESD protection for ground pins

composed by a double couple of anti-parallel LV diodes.

Figure 77. Ground pins inter-connection

L9908 implements a monitoring unit to detect disconnection affecting ground references.

If VPGND-VGND_ANA ≥ VTH_GND occurs for an interval longer than T_glm_loss_flt filtering time, the

PGND_LOSS flag is set.

If VGND_DIG-VGND_ANA ≥ VTH_GND occurs for an interval longer than T_glm_loss_flt filtering time, the

DGND_LOSS flag is set.

If VGND_DIG-VPGND ≥ VTH_GND occurs for an interval longer than T_glm_loss_flt filtering time, the

AGND_LOSS flag is set.

The correct operation Ground Loss Monitor stage is safety relevant and then a self-check procedure is

implemented.

Table 99. GLM electrical characteristics

Symbol

Parameter

Min

Typ

Max

Unit

Notes

GLM_th

GLM detection threshold VTH_GND

0.24

0.4

0.55

T_glm_loss_flt

GLM filter time

1.25

1.5

Digital Filter

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.

5.19

Temperature Monitor (OTM)

L9908 implements a monitoring unit of the average junction temperature able to detect excessive over-heating

conditions affecting the device.

L9908

Functional description

DS13546 - Rev 5

page 102/152

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