ir3092 International Rectifier Corp., ir3092 Datasheet - Page 23

• Manufacturer Part Number: ir3092
• Description: 2 Phase Opteron, Athlon, Or Vr10.x Control Ic
• Manufacturer: International Rectifier Corp.

Measure the inductance L and the inductor DC resistance R
The bias current flowing out of the non-inverting input of the current sense amplifier creates a voltage drop across R
which is equivalent to an input offset voltage of the current sense amplifier. The offset affects the accuracy of converter
current signal ISHARE as well as the accuracy of the converter output voltage if adaptive voltage positioning is adopted.
To reduce the offset voltage, a resistor R
output, as shown in Fig1
the bias current from the inverting input.
If R
k
Inductor DCR Temperature Correction
If the Current Sense Amplifier temperature dependent gain is not adequate to compensate the inductor DCR TC, a
negative temperature coefficient (NTC) thermistor can be added. The thermistor should be placed close to the inductor
and connected in parallel with the feedback resistor, as shown in Figure 10. The resistor in series with the thermistor is
used to reduce the nonlinearity of the thermistor.
Remote Voltage Sensing
To compensate for impedance in the ground plane, the VOSNS- pin is used for remote sensing and connects directly to
the load. The VDAC voltage is referenced to VOSNS- to avoid additional error terms or delay related to a separate
differential amplifier. The capacitor connecting the VDAC and VOSNS- pins ensure that high speed transients are fed
directly into the Error Amplifier without delay.
Master-Slave Current Share Loop
Current sharing between phases of the converter is achieved by a Master-Slave current share loop topology. The output
of the Phase 1 Current Sense Amplifier sets the reference for the Share Adjust Error Amplifier. The Share Adjust Error
Amplifier will then adjust the duty cycle of PWM Ramp2 to force its input error to zero, resulting in accurate current
sharing.
CSO
Page 23 of 37
is not used, R
CS
.
should be chosen so that the offset voltage is small enough. Usually R
The resistor R
CS
value is needed.
Figure 10- Temperature compensation of inductor DCR
CSO
RLINEAR
CSO
is determined by the ratio of the bias current from the non-inverting input and
R
RDRP
RFB
CSO
R
should be added between the amplifier inverting input and the converter
VDAC
VOSNS-
RNTC
CS
FB
VDRP
I
I
CSIN
CSIN
L
C
VDAC
IROSC
CS
VOUT SENSE+
R
¦
¥
L
L
. Pre-select the capacitor C
R
CS
ERROR AMPLIFIER
VDRP BUFFER
+
-
+
-
(11)
Current + VDAC
(12)
EAOUT
CS
and calculate R
CS
06/25/04
should be less than 2
CS
IR3092
as follows.
CS,