IR3088

IR3088 THEORY OF OPERATION

Block Diagram

The Block diagram of the IR3088 is shown in Figure 6, and specific features are discussed in the following sections.

+

-

10K

+

-

+

-

+

-

VCC

RMPIN+

RMPIN-

EAIN

ISHARE

PWMRMP

SCOMP

BIASIN

LGND

GATEH

VCCH

PGND

GATEL

CSIN+

VCCL

HOTSET

VRHOT

PHSFLT

DACIN

CSIN-

INTERNAL

CIRCUIT

BIAS

RAMP

COMPARATOR

CLOCK

PULSE

GENERATOR

SHARE

ADJUST

ERROR

AMP

RAMP

SLOPE

ADJUST

20mV

PWM

LATCH

RESET

PWM

COMPARATOR

DOMINANT

S

R

0% DUTY

CYCLE

COMPARATOR

SYSTEM

REFERENCE

VOLTAGE

X

0.91

GATE

NON-OVERLAP

COMPARATORS

CURRENT

SENSE

AMP

X34

2V

VOLTAGE

PROPORTIONAL

TO ABSOLUTE

TEMPERATURE

VRHOT

COMPARATOR

ENABLE

RAMP

DISCHARGE

CLAMP

FAULT

COMPARATOR

+

+

Figure 6. IR3088 Block Diagram

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 IR3088 0% duty cycle comparator detects this and drives both gate outputs low. This tri-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.

Thermal Monitoring (VRHOT)

The IR3088 senses its own die temperature and produces a voltage at the input of the VRHOT comparator that is

proportional to temperature. An external resistor divider connected from VBIAS to the HOTSET pin and ground can

be used to program the thermal trip point of the VRHOT comparator. 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.

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