IR3086AM International Rectifier, IR3086AM Datasheet - Page 11

• Manufacturer Part Number: IR3086AM
• Description: XPHASE Phase IC with OVP with fault overtemp detect. The IR3086AM Phase IC combined with an IR XPhase TM Control IC provides a full featured and flexible way to implement power solutions for the latest high performance CPUs and ASICs.
• Manufacturer: International Rectifier

Specifications of IR3086AM

• Package: 20-Lead MLPQ
• Circuit: X-Phase Phase IC
• Iout (a): 2.5A Gate Driver
• Pbf: PbF Option Available

IR3086A THEORY OF OPERATION
Block Diagram
The Block diagram of the IR3086A is shown in Fig. 6, and specific features are discussed in the following sections.
Tri-State Gate Drivers
The gate drivers can deliver up to 3A peak current. An adaptive non-overlap circuit monitors the voltage on the
GATEH and GATEL pins to prevent MOSFET shoot-through current while minimizing body diode conduction.
An Enable signal is provided by the Control IC to the Phase IC without the addition of a dedicated signal line. The
Error Amplifier output of the Control IC drives low in response to any fault condition such as input under voltage or
output overload. The IR3086A Body Braking
state operation prevents negative inductor current and negative output voltage during power-down.
The Gate Drivers revert to a high impedance “off” state if VCCL and VCCH supply voltages are below the normal
operating range. An 80kΩ resistor is connected across the GATEH/GATEL and PGND pins to prevent the
GATEH/GATEL voltage from rising due to leakage or other causes under these conditions.
Over Voltage Protection (OVP)
The IR3086A includes over-voltage protection that turns on the low side MOSFET to protect the load in the event of
a shorted high-side MOSFET or connection of the converter output to an excessive output voltage. A comparator
monitors the voltage at the CSIN- pin which is usually connected directly to the converter output. If the voltage
exceeds the DACIN voltage plus 125mV typical (100mV minimum and 160mV maximum) the GATEL pin drives
high. The OVP circuit overrides the normal PWM operation and will fully turn-on the low side MOSFET within
approximately 150ns. The low side MOSFET will remain ON until the over-voltage condition ceases.
PWMRMP
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RMPIN+
RMPIN-
SCOMP
ISHARE
HOTSET
BIASIN
VRHOT
EAIN
LGND
RAMP
SLOPE
ADJUST
RAMP
COMPARATOR
BIASIN
10K
+
-
SYSTEM
REFERENCE
VOLTAGE
VDAC
VRHOT
COMPARATOR
+
-
SCOMP
CLOCK
PULSE
GENERATOR
+
-
SHARE
ADJUST
ERROR
AMP
+
-
20mV
VOLTAGE
PROPORTIONAL
TO ABSOLUTE
TEMPERATURE
RAMP
DISCHARGE
CLAMP
ENABLE
ENABLE
Figure 6 – IR3086A Block Diagram
PWM
COMPARATOR
+
-
-
+
TM
+
VDAC
VDAC
comparator detects this and drives both gate outputs low. This tri-
+
X
0.91
BODY BRAKING
COMPARATOR
PWM
LATCH
DOMINANT
S
RESET
R
+
-
CURRENT
SENSE
AMP
X34
+
-
OVP
COMPARATOR
GATE
NON-OVERLAP
COMPARATORS
-
+
-
+
125mV
+
-
+
-
+
-
FAULT
COMPARATOR
2V
IR3086A
INTERNAL
CIRCUIT
BIAS
VCC
2/13/09
VCCH
GATEH
VCCL
GATEL
PGND
VCC
DACIN
CSIN+
CSIN-
PHSFLT