NCP5314 ON Semiconductor, NCP5314 Datasheet - Page 24

• Manufacturer Part Number: NCP5314
• Description: Two/Three/Four-Phase Buck CPU Controller
• Manufacturer: ON Semiconductor

equation to find R
voltage droop divided by the output current. If inductor
sensing is used, R
assuming that the current sense network equation (eq. 30) is
valid. Refer to the discussion on Current Sensing for further
information.
8. Current Sensing
different phases, to limit the maximum phase current and to
limit the maximum system current. Since the current
information, sensed across the inductor, is a part of the
control loop, better stability is achieved if the current
information is accurate and noise−free. The NCP5314
introduces a novel feature to achieve the best possible
performance: differential current sense amplifiers.
Figure 28.
network (R
C
(and/or C
the V
the R
“square−wave” at the V
time and minimal overshoot as shown in Figure 32.
CSx
It is easiest to select a value for R
Current sensing is used to balance current between
Two sense lines are routed for each phase, as shown in
For inductive current sensing, choose the current sense
This will provide an adequate starting point for R
−0.02
−0.04
−0.06
−0.08
−0.10
−0.12
−0.14
. After the converter is constructed, the value of R
DRP
CSx
Figure 29. The DC Effects of AVP vs. Load
0
0
CSx
signal during a step change in load current. Tune
CSx
R CSx @ C CSx + Lo (R L ) R PCB )
C
) should be fine−tuned in the lab by observing
CSx
, C
10
CSx
network by varying R
L
DRP
will be the resistance of the inductor,
, x = 1, 2, 3 or 4) to satisfy
. R
20
DRP
Spec Min
LL
Spec Max
output pin with maximum rise
I
is simply the desired output
OUT
30
(A)
FB
and then evaluate the
VID − V
40
CSx
to provide a
OUT
50
CSx
http://onsemi.com
(30)
and
CSx
60
NCP5314
24
Constant of the Current Sense Network Is Too Short
Constant of the Current Sense Network Is Too Long
V
Constant of the Current Sense Network Is Optimal:
Figure 30. V
Figure 31. V
DRP
Figure 32. V
(Slow): V
and V
(Fast): V
OUT
DRP
DRP
DRP
DRP
DRP
Without Overshooting.
Respond to the Load Current Quickly
and V
Tuning Waveforms. The RC Time
Tuning Waveforms. The RC Time
Tuning Waveforms. The RC Time
and V
OUT
OUT
Respond Too Slowly.
Both Overshoot.