L6706 datasheet(32/47 Pages) STMICROELECTRONICS

32 / 47 page

Soft-start

L6706

32/47

Doc ID 15698 Rev 2

Figure 14.

SSOSC connection

where TSS is the time spent to reach the programmed voltage VSS and RSSOSC the resistor

connected between SSOSC and SSEND (through a signal diode) in k

Ω.

Figure 15.

Soft-start time (TSS) when using RSSOSC, diode versus SSEND

Use the following relationship to select the maximum LTB switching frequency:

where FLIMIT has to be higher than the FSW switching frequency.

SSOSC

SS_END

RSSOSC

RPull-Up(1k)

VPull-Up(1.2V)

to SSEND Logic

Rb(10k)

RFLIMIT

Soft Start time and FLIMIT

selected in indipendent way.

RFLIM_SS

Soft Start time depends

on selected FLIMIT.

SSOSC kΩ

[]

D2 μs

[] 40 10

–

1.24

DIODE V

[]

–

1.24

-----------------------------------------------

⋅⋅

⋅

SS μs

[]

200

μs

[]

SSOSC kΩ

[]

40 10

–

⋅

-----------------------------------

1.24

DIODE V

[]

–

-----------------------------------------------

BOOT

------------------

⋅⋅

if V

BOOT

()

SSOSC kΩ

[]

40 10

–

⋅

-----------------------------------

1.24

DIODE V

[]

–

-----------------------------------------------

BOOT

------------------

⋅⋅

if V

BOOT

()

⎩

⎪

⎨

⎪

⎧

FLIMIT kΩ

[]

2.11 10

⋅

LIMIT kHz

[]

---------------------------------

1.24

BJT

[]

–

1.24

-----------------------------------------------

⋅

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