IR3513ZMTRPBF International Rectifier, IR3513ZMTRPBF Datasheet - Page 18

• Manufacturer Part Number: IR3513ZMTRPBF
• Description: IC CTRL XPHASE3 POL 32-MLPQ
• Manufacturer: International Rectifier
• Series: XPhase3™r

Specifications of IR3513ZMTRPBF

• Applications: Processor
• Current - Supply: 3mA
• Voltage - Supply: 8 V ~ 16 V
• Operating Temperature: 0°C ~ 125°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

Constant Over-Current Control during Soft Start
The over-current limit threshold is set by a resistor connected between OCSET and VREF pins. If the IIN pin
voltage, which is proportional to the average current plus VREF voltage, exceeds the OCSET voltage during soft
start, the constant over-current control is activated.
Figure 9 shows the constant over-current control with delay during soft start. The delay is required since over-
current conditions can occur as part of normal operation due to inrush current.
If an over-current occurs during soft start (before PG is asserted), the SS/DEL voltage is regulated by the over
current amplifier to limit the output current below the threshold set by OCSET voltage. If the over-current condition
persists after the delay time is reached, the fault latch will be set pulling the error amplifier’s output low and inhibiting
switching in the phase ICs. The SS/DEL capacitor will discharge until it reaches 0.2V and the fault latch is reset
allowing a normal soft start to occur. If an over-current condition is again encountered during the soft start cycle, the
constant over-current control actions will repeat and the converter will be in hiccup mode. The delay time is
controlled by a counter, which is triggered by the oscillator. The counter values vary with switching frequency per
phase in order to have a similar delay time for different switching frequencies.
Over-Current Hiccup Protection after Soft Start
The over current limit threshold is set by a resistor connected between OCSET and VREF pins. Figure 9 shows the
constant over-current control with delay after PG is asserted. The delay is required since over-current conditions
can occur as part of normal operation due to load transients or margin transitions.
If the IIN pin voltage, which is proportional to the average current plus VREF voltage, exceeds the OCSET voltage
after PG is asserted, it will initiate the discharge of the capacitor at SS/DEL. If the over-current condition persists
long enough for the SS/DEL capacitor to discharge below the 120mV offset of the delay comparator, the fault latch
will be set pulling the error amplifier’s output low and inhibiting switching in the phase ICs and de-asserting the PG
signal. The output current is not controlled during the delay time. The SS/DEL capacitor will discharge until it
reaches 200 mV and the fault latch is reset allowing a normal soft start to occur. If an over-current condition is
again encountered during the soft start cycle, the over-current action will repeat and the converter will be in hiccup
mode.
Page 18
ENABLE
VREF
SS/DEL
EAOUT
VOUT
VCC
PG
0.8V
3.2V
3.12V
1.4V
START DELAY
REPLACEMENT PRODUCT – IR3513ZMTRPBF
NOT RECOMMENDED FOR NEW DESIGNS
Figure 8 - Start-up sequence
SOFT START
TIME
PG DELAY TIME
NORMAL OPERATION
May 11, 2008
IR3513