NCP5392 ON Semiconductor, NCP5392 Datasheet - Page 22

• Manufacturer Part Number: NCP5392
• Description: 2/3/4-Phase Controller
• Manufacturer: ON Semiconductor

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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 5 V supply and the IC.
Understanding Soft−Start
AMD ramp to the initial VID code, or a VR11 Ramp to the
1.1 V boot voltage, with a pause to capture the VID code
then resume ramping to target value based on internal slew
rate limit. The initial ramp rate was set to be 0.8 mV/mS.
An RC input filter is required as shown in the V
The controller supports two different startup routines. An
Figure 7. 1.6 V to 0.5 V Dynamic VID response
Figure 8. Dynamic VID Settling Time Rising
(CH1: VID1, CH2: DAC, CH3:VCCP)
CC
Pin on the IC
CC
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pin to
22
Programming the Current Limit and the Oscillator
Frequency
approximately 330 kHz. The R
reference voltage which is divided down with a resistor
divider and fed into the current limit pin ILIM. Then
calculate the individual RLIM1 and RLIM2 values for the
divider. The series resistors RLIM1 and RLIM2 sink
current from the ILIM pin to ground. This current is
internally mirrored into a capacitor to create an oscillator.
The period is proportional to the resistance and frequency
is inversely proportional to the total resistance. The total
resistance may be estimated by Equation 1. This equation
is valid for the individual phase frequency in both three and
four phase mode.
The demo board is set for an operating frequency of
R
30.5 kW ^ 20947
Figure 9. VR11.1 Startup
osc
Figure 10. AMD Startup
^ 20947
OSC
F
SW
330
pin provides a 2.0 V
*1.1262
*1.1262
(eq. 1)