ncp5381 ON Semiconductor, ncp5381 Datasheet - Page 29

• Manufacturer Part Number: ncp5381
• Description: Ac-dc Offline Switching Controllers/regulators
• Manufacturer: ON Semiconductor

Dynamic VID Testing
Intel Requirements. Select the Dynamic VID option.
Before enabling the test set the lowest VID to 0.5 V or
greater and set the highest VID to a value that is greater than
the lowest VID selection, then enable the test. See Figures
21 through 23.
The VTT tool provides for VID stepping based on the
Figure 23. Dynamic VID Settling Time Falling
Figure 22. Dynamic VID Settling Time Rising
Figure 21. 1.6 to 0.5 Dynamic VID Response
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NCP5381
29
Design Methodology
Decoupling the V
minimize supply noise on the IC. The resistor should be
sized such that it does not generate a large voltage drop
between the 12 V supply and the IC. See the schematic
values.
Understanding Soft−Start
legacy VR10 ramp to the initial VID code, or a VR11 Ramp
to the 1.1 V VID code, with a pause to capture the VID code
then resume ramping to target value based on an internal
slew rate limit. See Figures 24 and 25. The controller is
designed to regulate to the voltage on the SS pin until it
reaches the internal DAC voltage. The soft−start cap sets
the initial ramp rate using a typical 5.0 mA current. The
typical value to use for the soft−start cap (SS), is typically
set to 0.01 mF. This results in a ramp time to 1.1 V of 2.2 ms
based on equation 1.
An RC input filter is required as shown in the V
The controller supports two different startup routines. A
C ss ^ i ss
2.2 · ms
C ss + 0.01 · mF
Figure 25. VR10 Legacy Startup
1.1 · V
Figure 24. VR11 Startup
CC
+
Pin on the IC
dv ss
dt ss
dv ss
dt ss
and i ss + 5 · mA
CC
(eq. 1)
pin to