IR3527MTRPBF International Rectifier, IR3527MTRPBF Datasheet - Page 14

• Manufacturer Part Number: IR3527MTRPBF
• Description: IC CTRL XPHASE3 DUAL 24-MLPQ
• Manufacturer: International Rectifier
• Series: XPhase3™r

Specifications of IR3527MTRPBF

• Applications: Processor
• Current - Supply: 8mA
• Voltage - Supply: 8 V ~ 28 V
• Operating Temperature: 0°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: *
• Package: 24-Lead MLPQ
• Circuit: X-Phase Phase IC
• Iout (a): 1.3A Gate Driver
• Pbf: PbF Option Available
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

IR3527
Emulated Bootstrap Diode
IR3527 integrates a PFET to emulate the bootstrap diode. An external bootstrap diode connected from VCCL
pin to BOOST pin can be added to reduce the drop across the PFET but is not needed in most applications.
PSI Mode
In order to increases the efficiency under light load condition, the IR3527 employs a power state indicator (PSI)
signal to switch off the phase IC at light load. An active low on the PSI indicates the low power state and can be
used to switch off the phase IC. Once the PSI signal is asserted, the IR3527 waits for 8 PHSIN cycles to disable
the gate drives. When the PSI signal is de-asserted again the anti-bias latch circuit ensures that the topFET is
switched on first. The maximum de-assert delay is determined by the CLKIN period.
Operation at Higher Output Voltage
The proper operation of the phase IC is ensured for output voltage up to 5.1V. Similarly, the minimum VCC for
proper operation of the phase IC is 8 V. If the condition [V
+ 35(V
-V
) + 1.4V] is violated,
CCL
DACIN
CSIN+x
CSIN-x
the current sharing performance of the phase IC is affected.
APPLICATIONS INFORMATION
IR3527 EXTERNAL COMPONENTS
Inductor Current Sensing Capacitor C
and Resistor R
CS
CS
The DC resistance of the inductor is utilized to sense the inductor current. Usually the resistor R
and
CS
capacitor C
in parallel with the inductor are chosen to match the time constant of the inductor, and therefore
CS
the voltage across the capacitor C
represents the inductor current. If the two time constants are not the
CS
same, the AC component of the capacitor voltage is different from that of the real inductor current. The time
constant mismatch does not affect the average current sharing among the multiple phases, but does affect the
current signal ISHARE as well as the output voltage during the load current transient if adaptive voltage
positioning is adopted.
Measure the inductance L and the inductor DC resistance R
. Pre-select the capacitor C
and calculate R
L
CS
CS
as follows.
L
R
L
R
(1)
CS
C
CS
Bootstrap Capacitor C
BST
Depending on the duty cycle and gate drive current of the phase IC, a capacitor in the range of 0.1uF to 1uF is
needed for the bootstrap circuit.
Decoupling Capacitors for Phase IC
A 0.1uF-1uF decoupling capacitor is required at the VCCL pin.
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.
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