ir3084u International Rectifier Corp., ir3084u Datasheet - Page 24

• Manufacturer Part Number: ir3084u
• Description: Xphasetm Vr10, Vr11 & Opteron/athlon64 Control Ic
• Manufacturer: International Rectifier Corp.

System Reference Voltage (VBIAS)
The IR3084U supplies a 6.8V/6mA precision reference voltage from the VBIAS pin. The oscillator ramp trip points
are based on the VBIAS voltage so it should be used to program the Phase ICs phase delay to minimize phase
errors.
Phase IC Gate Driver Bias Regulator / VRHOT Comparator
An internal amplifier can be configured as a gate driver bias regulator to provide programmable gate driver
voltage for phase ICs (Figure 12a), or a thermal monitor to provide VRHOT/VRFAN signal as required in VR11
(Figure 12b).
The internal current source IREGSET whose value is programmed by the switching frequency going through the
external RSET resistor sets the gate driver voltage or the VRHOT/VRFAN threshold voltage. An NTC thermistor
is used to monitor the temperature on the VRM/VRD.
Page 24 of 47
R2
100K
Figure 12a – IR3084U Bias Regulator configured for Gate Driver Bias Regulator
CVGDRV
10nF
Figure 12b – IR3084U Bias Regulator configured for VRHOT/VRFAN function
R1
10K
R3
3K
RH2
36K
C1
1nF
RVGDRV
97.6K
REGSET
REGFB
IR3084 CONTROL IC
VBIAS
IR3084 CONTROL IC
VCC
REGSET
RH1
1.1MEG
IREGSET
+
-
VCC
REGDRV
IREGSET
0Adc
+
-
REGDRV
REGFB
R4
2K
R5
1K
+12V
C2
10nF
+
RPU
1ohm / 1206
Q1
CJD200
C2
10uF
+3.3V
VGDRIVE
RPU1
2K
Q5
2N7002
VRHOT#
IR3084U
9/14/2005