IR3503MTRPBF International Rectifier, IR3503MTRPBF Datasheet - Page 22

• Manufacturer Part Number: IR3503MTRPBF
• Description: IC CTRL XPHASE VR11.0/1 32-MLPQ
• Manufacturer: International Rectifier
• Series: XPhase3™r

Specifications of IR3503MTRPBF

• Applications: Processor
• Current - Supply: 8mA
• Voltage - Supply: 4.75 V ~ 7.5 V
• Operating Temperature: 0°C ~ 100°C
• Mounting Type: Surface Mount
• Package / Case: *
• Package: 32-Lead MLPQ
• Circuit: X-Phase Control IC
• Switch Freq (khz): 250kHz to 1.5MHz
• Pbf: PbF Option Available
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: IR3503MTRPBFTR

Figure 13 clearly explains the SHIFT functionality. The phase ICs wait for 8 PHSIN cycles after the assertion of
PSI# to start shedding the phases (and issue a down SHIFT signal). When the phases are shed, the CLK frequency
is also reduced simultaneously. The SHIFT signal is synchronized with the CLKOUT falling edge. However, on de-
assertion of PSI#, all the phases that were active before PSI# assertion will be restored immediately without any
delay. Another key feature in IR3503 is the internal programming of over-current protection (OCP). The OCP
threshold is calculated based on the number of phases in the system as given by the equation below:
Hence, the OCP threshold will be automatically adjusted based on the number of active phases in the system.
When PSI# de-assertion occurs, all the phases in the system are restored immediately without any delay which can
also be clearly observed in figure 13.
Over-Current Hiccup Protection after Soft Start
The over current limit is fixed at
current control with delay after VRRDY is asserted. The delay is required since over-current conditions can occur as
part of normal operation due to load transients or VID transitions.
If the VDRP pin voltage, which is proportional to the average current plus VDAC voltage, exceeds the over current
protection (OCP) limit after VRRDY is asserted, it will initiate the discharge of the capacitor at SS/DEL. The
magnitude of the discharge current is proportional to the voltage difference between VDRP and OCP limit and has a
maximum nominal value of 55uA. If the over-current condition persists long enough for the SS/DEL capacitor to
discharge below the 120 mV offset of the delay comparator, the fault latch will be set pulling the error amplifier’s
V
CCL
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2
OCP
1.17
Maximum
threshold
*
Number
Figure 13: SHIFT functionality
number
of
=
active
1.17
Maximum
of
phases
phases
*
Number
number
above the VDAC. Figure 14 shows the constant over-
of
active
of
phases
phases
February 12, 2010
IR3503