ir3082pbf International Rectifier Corp., ir3082pbf Datasheet - Page 13

• Manufacturer Part Number: ir3082pbf
• Description: Xphase Amd Opterontm/athlon 64tm Control Ic
• Manufacturer: International Rectifier Corp.

The voltage at the VDRP pin is a buffered version of the share bus and represents the sum of the DAC voltage and
the average inductor current of all the phases. The VDRP pin is connected to the FB pin through the resistor R
Since the Error Amp will force the loop to maintain FB to be equal to the VDAC reference voltage, current will flow
into the FB pin equal to (VDRP-VDAC) / R
increases accordingly. More current flows through the feedback resistor R
proportional to the load current. The positioning voltage can be programmed by the resistor R
impedance produces the desired converter output impedance. The offset and slope of the converter output
impedance are referenced to and therefore independent of the VDAC voltage.
Inductor DCR Temperature Correction
If the thermal compensation of the inductor DCR provided by the temperature dependent gain of the current sense
amplifier is not adequate, a negative temperature coefficient (NTC) thermistor can be used for additional correction.
The thermistor should be placed close to the inductor and connected in parallel with the feedback resistor as shown
in Figure 9. The resistor in series with the thermistor is used to reduce the nonlinearity of the thermistor.
Page 13 of 33
Figure 9 - Temperature compensation of inductor DCR
VDAC
Control IC
Droop
Amplifier
Error
Amplifier
+
-
If b
VDAC
Figure 8 - Adaptive voltage positioning
VDRP
-
+
Control IC
. When the load current increases, the adaptive positioning voltage
FB
Droop
Amplifier
EA
VDRP
IIN
VDAC
Error
Amplifier
Rv drp
+
-
If b
Rf b
Vo
-
+
ISHARE
ISHARE
VDAC
VDAC
EA
FB
IIN
Phase IC
Phase IC
Rf b
Rv drp
VDRP
10k
10k
Rf b
Rt
FB
Current Sense
Amplifier
Current Sense
Amplifier
, and makes the output voltage lower
Vo
+
-
+
-
CS+
CS-
CS+
CS-
IR3082PbF
VDRP
01/31/05
so that the droop
VDRP
.