Hi there. Not sure exactly what section this fits into here but I'm trying to identify what is reporting current draw on my Dell motherboard. Specifically a Dell precision T5810 which is a lga 2011-3 socket. This is just something I'm playing with and to replace the board due to failure is of little concern (it's cheap) so I'm overclocking and hitting a current limit of 140 watts. I'd like to cut the reported value in half. I have no schematic for the motherboard. I do have schematics for the MOSFETs and pwm controller. And photos top and bottom of the MOSFETs on the board. I would assume the value is being reported by use of a shunt resistor. I'm having trouble testing what resistor or resistors would be in charge of that.

I also found these. They are 6 2.2 ohm resistors directly underneath of the 6 MOSFETs.

Any help would be appreciated.

 

I also found another pwm controller. I still have to test some pinouts on it to try and confirm its part of the cpu circuit. I think I need to get my needle tip leads for my meter which I took to work. Here is a quote from the data sheet on the ncp6133 I found on my board. Ive also attached the entire datasheet pdf.

Total Current Sense Amplifier
The NCP6133 uses a patented approach to sum the phase
currents into a single temperature compensated total current
signal. This signal is then used to generate the output voltage
droop, total current limit, and the output current monitoring
functions. The total current signal is floating with respect to
CSREF. The current signal is the difference between
CSCOMP and CSREF. The Ref(n) resistors sum the signals
from the output side of the inductors to create a low
impedance virtual ground. The amplifier actively filters and
gains up the voltage applied across the inductors to recover
the voltage drop across the inductor series resistance (DCR).
Rth is placed near an inductor to sense the temperature of the
inductor. This allows the filter time constant and gain to be
a function of the Rth NTC resistor and compensate for the
change in the DCR with temperature.
Figure 8.
-
+
CSN1
CSN2
CSN3
SWN1
SWN2
SWN3
Rref1
Rref2
Rref3
10
10
10
Rph1
Rph2
Rph3
Cref
1n
CSREF CSCOMP CSSUM
Ccs1
Ccs2
Rcs2 Rcs1
82.5 k 35.7 k
Rth
100 k
The DC gain equation for the current sensing:
VCSCOMP−CSREF -
−
Rcs2 Rcs1*Rth
Rcs1Rth
Rph * IoutTotal * DCR
(eq. 2)
Set the gain by adjusting the value of the Rph resistors.
The DC gain should set to the output voltage droop. If the
voltage from CSCOMP to CSREF is less than 100 mV at
ICCMAX then it is recommended to increase the gain of the
CSCOMP amp and add a resister divider to the Droop pin
filter. This is required to provide a good current signal to
offset voltage ratio for the ILIMIT pin. When no droop is
needed, the gain of the amplifier should be set to provide
~100 mV across the current limit programming resistor at
full load. The values of Rcs1 and Rcs2 are set based on the
100k NTC and the temperature effect of the inductor and
should not need to be changed. The NTC should be placed
near the closest inductor. The output voltage droop should
be set with the droop filter divider.
The pole frequency in the CSCOMP filter should be set
equal to the zero from the output inductor. This allows the
circuit to recover the inductor DCR voltage drop current
signal. Ccs1 and Ccs2 are in parallel to allow for fine tuning
of the time constant using commonly available values. It is
best to fine tune this filter during transient testing.
FZ -
DCR @ 25° C
2 * PI * LPhase
(eq. 3)
FP -
1
2 * PI * Rcs2 Rcs1*Rth@25° C
Rcs1Rth@25° C
* (Ccs1 Ccs2)
(eq. 4)