IR3084UMTRPBF International Rectifier, IR3084UMTRPBF Datasheet - Page 19

• Manufacturer Part Number: IR3084UMTRPBF
• Description: IC CTLR XPHASE 28-MLPQ
• Manufacturer: International Rectifier
• Series: XPhase™r

Specifications of IR3084UMTRPBF

• Package / Case: 28-MLPQ
• Mounting Type: Surface Mount
• Current - Supply: 14mA
• Voltage - Supply: 9.5 V ~ 16 V
• Operating Temperature: 0°C ~ 100°C
• Applications: Processor
• Package: 28-Lead MLPQ
• Circuit: X-Phase Control IC
• Switch Freq (khz): 150kHz to 1.0MHz
• Pbf: PbF Option Available
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

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.
Remote Voltage Sensing
To compensate for impedance in the ground plane, the VOSNS− pin is used for remote ground sensing and
connects directly to the load. The VDAC voltage is referenced to VOSNS− to avoid additional error terms or
delays 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 amp without delay.
Start-up Modes
The IR3084U has a programmable soft-start function to limit the surge current during converter start-up. A
capacitor connected between the SS/DEL and LGND pins controls soft start timing, over-current protection delay,
and hiccup mode timing. A charge current of 70µA controls the positive slope of the voltage at the SS/DEL pin.
There are two types of start-up possible: VR11 and Opteron/Athlon64. In VR11 mode, the soft start circuitry will
set the voltage at the VDAC pin to the 1.1V Boot voltage and the converter’s output will slowly rise using the slew
rate set by the capacitor at the SS/DEL pin until it’s equal to the VDAC voltage. After Vcore reaches the 1.1V
Boot voltage there will be a short delay, the VID pins will be sampled, and the voltage at the VDAC pin and the
converter’s output will increase or decrease to the desired VID setting using the dynamic VID slew rate. In
Opteron/Athlon64 mode, the soft start sequence will ramp the voltage at the VDAC pin directly to the external VID
setting using the slew rate set by the capacitor at the SS/DEL pin without pausing at the 1.1V Boot voltage.
Page 19 of 47
Figure 9 - Temperature compensation of inductor DCR
IOFFSET
Control IC
AVP
Amplifier
VDAC
Error
Amplifier
+
-
-
+
RSETPT
VSETPT
EAOUT
VDRP
IIN
IIN
RDRP
RFB2
RFB
Rt
Vo
IR3084U
9/14/2005