ncp5392p ON Semiconductor, ncp5392p Datasheet - Page 25

• Manufacturer Part Number: ncp5392p
• Description: 2/3/4-phase Controller For Cpu Applications
• Manufacturer: ON Semiconductor

Simple Average SPICE Model
control system.
Compensation and Output Filter Design
significantly different, it's best to use the available PSPICE
models to design the compensation and output filter from
scratch.
2.0 MHz. The phase switching frequency is currently set to
330 kHz. It can easily be seen that the board impedance of
0.75 mW between the load and the bulk capacitance has a
large effect on the output filter. In this case the six 560 mF
bulk capacitors have an ESR of 7.0 mW. Thus the bulk ESR
A simple state average model shown in Figure 13 can be used to determine a stable solution and provide insight into the
If the required output filter and switching frequency are
The design target for this demo board was 1.0 mW up to
1.3V
VRamp_min
Unity Gain BW=15MHz
Voff
Voff
1E3
1k
RSUM
GAIN = 1
2.2k
RF
R8
1k
0
12V
V3
CH
22p
RDFB
{-2/3*4}
C4
0
10.6p
2k
10.6p
0
Figure 13. NCP5392P Average SPICE Model
C5
R6
1k
5.11k
CF
1.8n
22p
R12
1E3
0
12
0
Vdrp
CDFB
{185e-9/4}
GAIN = {6}
1
CFB1
680P
-
+
E1
http://onsemi.com
L
E
+
-
RFB
Voff
NCP5392P
1k
2
{0.6E-3/4}
RFB1
69.8
DCR
25
RDAC
50
plus the board impedance is 1.15 mW + 0.75 mW or
1.9 mW. The actual output filter impedance does not drop
to 1.0 mW until the ceramic breaks in at over 375 kHz. The
controller must provide some loop gain slightly less than
one out to a frequency in excess 300 kHz. At frequencies
below where the bulk capacitance ESR breaks with the
bulk capacitance, the DC-DC converter must have
sufficiently high gain to control the output impedance
completely. Standard Type-3 compensation works well
with the NCP5392P.
2
1
1
{3.5e-9/6}
CDAC
{560e-6*6}
ESLBulk
CBulk
{7e-3/6}
ESRBulk
12n
LBRD
0
100p
Voffset
1.3V
2
0.75m
DC = 1.2V
RBRD
AC = 0
R11
1k
R9
1k
2
CCer
1
{1.5e-9/18}
{22e-6*18}
{1.5e-3/18}
ESRCer
ESLCer
10.6p
Vdrp
VDAC
TRAN = PULSE
(0 0.05 400u 5u 5u 500u 1000u)
0
R10
2k
C6
0
0Adc
0Aac
Voff
1E3
TD = 100u
PER = 200u
PW = 100u
I2 = 110
TR = 50n
TF = 50n
I1 = 50
IMON
I1
0
Vout