NCP5392 ON Semiconductor, NCP5392 Datasheet - Page 27

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

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thermally compensated to cancel this effect to a great
degree by adding an NTC in parallel with R
the droop gain as the temperature increases. The NTC
device is nonlinear. Putting a resistor in series with the NTC
helps make the device appear more linear with
By including the NTC R
Equation 17
Figure 16 shows the comparison of the compensated output
impedance and uncompensated output impedance varying
with temperature.
IMON for Current Monitor
phases. It can be fed into the IMON amplifier for current
monitoring as shown in Figure 17. IMON amplifier has a
fixed gain of 2 with an offset when VDRP is equal to 1.3 V,
the internal floating reference voltage. The IMON
amplifier will be saturated at an maximum output of 1.09 V
therefore the total gain of current should be carefully
considered to make the maximum load current indicated by
the IMON output. Figure 18 shows a typical of the relation
between IMON output and the load current.
Actual DCR increases by temperature, the system can be
The typical equation of an NTC is based on a curve fit
The demo board use a 10 kW NTC with a b value of 3740.
Since VDRP signal reflects the current information of all
0.0013
0.0012
0.0011
0.0009
0.0008
0.0007
0.0006
0.001
25
RT2(T) + RT2
Figure 16. Z
Z
out
(T) +
45
Zout
Zout(uncomp)
T2
out
R
25C
Celsius
Z
FB
and the series isolation resistors the new equation becomes:
out
vs. Temperature
@ e
@ DCR
(T) +
b
65
273)T
R
25C
1
FB
@ (1 ) 0.00393 @ (T * 25)) @ A
*
@ DCR
298
1
NOR
85
25C
to reduce
(eq. 17)
@ (1 ) 0.00393 @ (T * 25)) @ A
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105
27
R
R
temperature. The series resistor is split and inserted on both
sides of the NTC to reduce noise injection into the feedback
loop. The recommended total value for R
approximately 1.0 kW.
by the equation:
Power Saving Indicator (PSI) and Phase Shedding
signal to the VR controller to indicate when the processor
is in a low power state. NCP5392 use the status of PSI pin
to decide if there is a need to change its operating state to
maximize efficiency at light loads. When PSI = 0, the PSI
function will be enabled, and VR system will be running at
a single phase power saving mode.
normal power state.
NCP5359 driver to represent diode emulation mode at light
load for further power saving.
shedding will be presented. Only one phase is active in the
DRP
DRP
I1
I2
I3
I4
The output impedance varies with inductor temperature
VR11.1 requires the processor to provide an output
The PSI signal will de−assert 1 ms prior to moving to a
At power saving mode, NCP5392 works with the
When system switches on PSI function, an phase
1.05
0.84
0.63
0.42
0.21
Ilim
0
CSSUM
0
Figure 18. IMON Output vs. Output Current
+
Acssum
10
@
(R
20
NOR
Figure 17. IMON Circuit
CSSUM
R
NOR
RISO1
)R
RSUM
30
@(R
ISO1
@ A
Vimon vs. Iout
ISO1
)R
40
DRP
)R
ISO2
Adrp
Iout−A
RNOR
+
−
ISO2
50
RT2
)R T2 )@R
)R T2 )
60
SUM
RISO2
ISO1
70
+
Gain = 2
−
+
−
plus R
80
(eq. 15)
(eq. 16)
90 100
OCP
Imon
event
ISO2
is