L9907 datasheet(11/49 Pages) STMICROELECTRONICS

11 / 49 page

DS11800 Rev 5

11/49

L9907

Functional description

2.4

Boost converter

The purpose of the Boost converter is to generate a voltage around 10 V higher than the

one present at VDH monitor pin. This voltage is used to supply HS drivers (through

dedicated regulators) and LS drivers (through VCAP regulator). The regulated voltage is

present at BST_C pin. BST_L pin is the drain of an integrated NDMOS switch. VCAP

regulator is a current limited voltage regulator, fed by Boost and referred to SLS3 voltage,

used to supply LS drivers. Each HS driver has a current limited voltage regulator that is fed

by Boost, referred to SHSx pins and with regulated voltage present at CBSx pins. These

regulators limit VGS of the external FETs. Overvoltage at BST_C pin (e.g. due to low current

demand) is limited by skipping turn on pulses until over voltage condition is removed. A

fixed voltage threshold on BST_C is implemented, in order to avoid the boost voltage

exceeding a safety level in case of high voltage on VDH monitor pin. In case the user would

not need this over voltage protection (e.g. for applications where high voltage is present on

the VDH rail), L9907 provides a disabling bit in CMD3 SPI command (DIS_BSTov). The

Boost converter is disabled in case of validated Fault (see Table 6) and reactivated by fault

removal and cleared after SPI reading.

Figure 3. MOSFET drivers supply structure

SHS1

GHS1

CBS1

SHS2

GHS2

CBS2

SHS3

GHS3

CBS3

SLS1

GLS1

SLS2

GLS2

SLS3

GLS3

ate-Driver 1

ate-Driver 2

ate-Driver 3

ate-Driver 1

ate-Driver 2

ate-Driver 3

BST_C

HS-G

V-re

HS-G

V-re

HS-G

V-re

LS-G

VCAP

V-reg

GAPGPS00835

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