IR3084AMPBF International Rectifier, IR3084AMPBF Datasheet - Page 25

• Manufacturer Part Number: IR3084AMPBF
• Description: IC XPHASE CONTROL 28-MLPQ
• Manufacturer: International Rectifier
• Series: XPhase™r

Specifications of IR3084AMPBF

• Applications: Processor
• Current - Supply: 14mA
• Voltage - Supply: 9.5 V ~ 16 V
• Operating Temperature: 0°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: 28-MLPQ
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

DESIGN PROCEDURES – IR3084A and IR3086A Chipset
IR3084A EXTERNAL COMPONENTS
Oscillator Resistor Rosc
The oscillator of IR3084A generates a triangle waveform to synchronize the phase ICs, and the switching
frequency of the each phase converter equals the oscillator frequency, which is set by the external resistor R
according to the curve in Figure 13 on page 23.
VDAC Slew Rate Programming Capacitor C
The sink and source currents of the VDAC pin are set by the value of R
VDAC pin is slightly less than the source current. Therefore, the VDAC sink current (I
calculate C
The negative slew rate of VDAC (SR
(1). The resistor R
positive slew rate of the VDAC voltage (SR
calculated using Equation (3).
The VID voltage rise or fall time during startup with Boot Mode (TD4) can be calculated using either Equation
(4a) or (4b).
Where: I
page 23.
Where: I
on page 23.
Where: VDAC is the DAC voltage set by the VID pins.
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TD
TD
C
R
SR
VDAC
VDAC
VDAC
UP
4
4





to insure that the dynamic VID slew rate when Vcore decreases is not too slow.
C
I
If Boot Mode is not used then TD4 = 0.
I
SINK
I
SOURCE
SOURCE
C
I
0
C
SR
SOURCE
SOURCE
VDAC
SINK
VDAC
5 .
VDAC
I
VDAC
SINK
DOWN
is the sink current of the VDAC pin at the chosen value of R



is the source current of the VDAC pin at the chosen value of R
and I
is used to compensate/stabilize the VDAC circuit and is determined by Equation (2). The


1
3

1 .
2 .
VDAC
C
V
SINK
VDAC

10

VDAC
are the source and sink currents of the VDAC pin.
2

15

1
DOWN
1 .
V


) is programmed by the external capacitor C
UP
VDAC
) is proportional to the negative slew rate of VDAC and can be
if VDAC > 1.1V
if VDAC < 1.1V
and Resistor R
VDAC
OSC
. The sink current capability of the
OSC
as shown in Figure 17 on
SINK
OSC
VDAC
) should be used to
as shown in Figure 17
as shown in Equation
IR3084A
3/3/2009
(1)
(2)
(3)
(4a)
(4b)
OSC