IR3503MTRPBF International Rectifier, IR3503MTRPBF Datasheet - Page 26

• 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

IR3503
VDAC voltage change at light load with large output capacitance. Therefore, over-voltage threshold is raised to 1.73
V from VDAC+130 mV whenever dynamic VID is detected and the difference between output voltage and VDAC is
more than 50mV, as shown in Figure 17. The over-voltage threshold is changed back to VDAC+130 mV if the
difference is smaller than 50 mV.
Open Daisy Chain Protection
IR3503 checks the daisy chain every time it powers up. It starts a daisy chain pulse on the PHSOUT pin and detects
the feedback at PHSIN pin. If no pulse comes back after 32 CLKOUT pulses, the pulse is restarted again. If the
pulse fails to come back the second time, the open daisy chain fault is registered, and SS/DEL is not allowed to
charge. The fault latch can only be reset by cycling the power to VCCL.
After powering up, the IR3503 monitors PHSIN pin for a phase input pulse equal or less than the number of phases
detected. If PHSIN pulse does not return within the number of phases in the converter, another pulse is started on
PHSOUT pin. If the second started PHSOUT pulse does not return on PHSIN, an open daisy chain fault is
registered.
Enable Input
The ENABLE pin below 0.8 V sets the Fault Latch and a voltage above 0.85 V enables the soft start of the
converter.
Thermal Monitoring (VRHOT)
A resistor divider including a thermistor at HOTSET pin sets the VRHOT threshold. The thermistor is usually placed
at the temperature sensitive region of the converter, and is linearized by a series resistor. The IR3503 compare
HOTSET pin voltage with a reference voltage of 1.6 V. The VRHOT pin is an open-collector output and should be
pulled up to a voltage source through a resistor. If the thermal trip point is reached the VRHOT output drives low.
The hysteresis of the VRHOT comparator helps eliminate toggling of VRHOT output.
The overall system must be considered when designing for OVP. In many cases the over-current protection of the
AC-DC or DC-DC converter supplying the multiphase converter will be triggered and provide effective protection
without damage as long as all PCB traces and components are sized to handle the worst-case maximum current. If
this is not possible, a fuse can be added in the input supply to the multiphase converter.
Phase Number Determination
After a daisy chain pulse is started, the IR3503 checks the timing of the input pulse at PHSIN pin to determine the
phase number. This information is used to have symmetrical phase delay between phase switching without the
need of any external component.
Single Phase Operation
In an architecture where only a single phase is needed the switching frequency is determined by the clock
frequency.
Current Share Loop Compensation
The internal compensation of current share loop ensures that crossover frequency of the current share loop is at
least one decade lower than that of the voltage loop so that the interaction between the two loops is eliminated. The
crossover frequency of current share loop
is approximately 8 kHz.
Page 26 of 39
February 12, 2010