L6714 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
L6714
STMicroelectronics
'L6714' PDF : 70 Pages View PDF
L6714
15.1
Soft start
Intel mode
Once L6714 receives all the correct supplies and enables, and Intel Mode has been
selected, it initiates the Soft-Start phase with a T1 = 1ms(min) delay. After that, the reference
ramps up to VBOOT = 1.081V (1.100V - 19mV) in T2 according to the SSOSC settings and
waits for T3 = 75µsec(typ) during which the device reads the VID lines. Output voltage will
then ramps up to the programmed value in T4 with the same slope as before (See
Figure 14).
SSOSC defines the frequency of an internal additional Soft-Start-oscillator used to step the
reference from zero up to the programmed value; this oscillator is independent from the
main oscillator whose frequency is programmed through the OSC pin. SSOSC sets then the
Output Voltage dV/dt during Soft-Start according to the resistor RSSOSC connected vs.
SGND. In particular, it allows to precisely programming the start-up time up to VBOOT (T2)
since it is a fixed voltage independent by the programmed VID. Total Soft-Start time
dependence on the programmed VID results (See Figure 15):
RSSOSC[kΩ] = T2[µs] ⋅ 4.9783 ⋅ 10–2
Note:
TS S [ µs ]
=
⎧
⎪
1075 [ µs ]
+
⎪
⎨
⎪
⎪
⎩
--R-----S---S---O----S----C----[--k---Ω-----]--
5.3816 ⋅ 10–2
⋅
--R-----S---S---O----S----C----[--k---Ω-----]--
5.3816 ⋅ 10–2
⋅
VSS
[VBOOT + (VBOOT – VSS)]
if(VSS > VBOOT)
if(VSS < VBOOT)
where TSS is the time spent to reach the programmed voltage VSS and RSSOSC the resistor
connected between SSOSC and SGND in kΩ.
Protections are active during Soft-Start, UVP is enabled after the reference reaches 0.6V
while OVP is always active with a fixed 1.24V threshold before VBOOT and with the threshold
coming from the VID (or the programmed VOVP) after VBOOT (See red-dashed line in
Figure 14).
If during T3 the programmed VID selects an output voltage lower than VBOOT, the output
voltage will ramp to the programmed voltage starting from VBOOT.
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