L9908 datasheet(21/153 Pages) STMICROELECTRONICS

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Functional description

5.1

Internal supply

5.1.1

VDD power supply

The internal supply rails for analog and digital circuitries on L9908 are generated from the VDD pin which is the

main power input. Additionally VDD is used as reference voltage for Current Measurement Analog output (CSO

Buffers).

5.1.2

Internal supply monitor

Each internal supply voltage level (V3V3_ANA/DIG) is monitored by means of a dedicated UV and an OV

diagnosis. Abnormal behavior on internal supply level will cause the generation of a POR (Power on Reset) event

that consequently sends L9908 into a RESET state. Hysteresis on thresholds and filtering time are implemented.

If V3V3_ANA/DIG ≤ V3V3_uv_th occurs for an interval longer than T_por_htol_flt, INT_RST flag is set. The error

flag remains set until the failure condition is removed and the flag is cleared by an SPI command. POR_ANA/DIG

is set low and internal reset is triggered.

If V3V3_ANA/DIG ≥ V3V3_ov_th occurs for an interval longer than T_por_htol_flt, INT_RST flag is set. The error

flag remains set until the failure condition is removed and the flag is cleared by an SPI command. POR_ ANA/DIG

is set low and internal reset is triggered. OV/UV Resets related to V3V3 internal reference are represented in

Figure 8.

The internal supply monitor is safety relevant and then a self-check procedure is implemented.

Note:

All parameters are guaranteed and tested in the voltage ranges specified in Table 5 unless otherwise specified.

Where not specified parametrical operating range equals functional operating range.

Table 11. Internal power supply electrical characteristics

Symbol

Parameter

Min

Typ

Max

Unit

Notes

VBG_vout

Bandgap output voltage

1.188

1.2

1.212

V3V3_vout

V3V3_ANA/DIG output voltage

3.2

3.3

3.34

V3V3_uv_th

V3V3_ANA/DIG under-voltage threshold

2.65

2.73

2.93

Comparator output Low to High

V3V3_uv_hys

V3V3_ANA/DIG under-voltage hysteresis

V3V3_ov_th

V3V3_ANA/DIG over-voltage threshold

3.6

3.7

3.9

Comparator output Low to High

V3V3_ov_hys

V3V3_ANA/DIG over-voltage hysteresis

V3V3_pre_vout V3V3_PRE output voltage

2.7

3.35

3.55

T_por_ltoh_flt

POR_V3V3 Low to High state filter time

3.2

4.8

7.3

μs

Analog filter

T_por_htol_flt

POR_V3V3 High to Low state filter time

5.4

8.3

13.5

μs

Analog filter

L9908

Functional description

DS13546 - Rev 3

page 21/153

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