L6713ATR View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
L6713ATR
STMicroelectronics
'L6713ATR' PDF : 64 Pages View PDF
Soft-start
16 Soft-start
L6713A
L6713A implements a soft-start to smoothly charge the output filter avoiding high in-rush
currents to be required to the input power supply. The device increases the reference from
zero up to the programmed value in different ways according to the selected operative mode
and the output voltage increases accordingly with closed loop regulation.
The device implements soft-start only when all the power supplies are above their own turn-
on thresholds and the OUTEN pin is set free.
At the end of the digital soft-start, SS_END/PGOOD signal is set free. Protections are active
during this phase; under voltage is enabled when the reference voltage reaches 0.6 V while
over voltage is always enabled with a threshold dependent on the selected operative mode
or with the fixed threshold programmed by ROVP (See “Over voltage and programmable
OVP” Section).
Figure 15. Soft-start
OUTEN
Intel Mode
OUTEN
AMD 6BIT Mode
VOUT
OVP
t
VOUT
t
OVP
SS_END
t
PGOOD
t
T1 T2 T3 T4
t
TSS
t
TSS
16.1
Intel mode
Once L6713A receives all the correct supplies and enables, and Intel mode has been
selected, it initiates the soft-start phase with a T1 = 1 ms(min) delay. After that, the reference
ramps up to VBOOT = 1.081 V (1.100V - 19mV) in T2 according to the SS/LTBG/AMD settings
and waits for T3 = 75 μsec(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 15).
SS/LTB/AMD 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.
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 17 and See Figure 19).
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