9

FN6280.1

August 7, 2006

The OCP circuit does not directly detect the DC load current

leaving the converter. The OCP circuit detects the peak of

positive-flowing output inductor current. The low-side

positive output inductor current when the high-side MOSFET

is off. The inductor current develops a negative voltage

measured shortly after the LG gate-driver output goes high.

zero volts with respect to the GND pin. The negative voltage

across the PHASE and GND pins is nulled by the voltage

on a PWM pulse before 20µs has elapsed, the timer will be

written as:

Where:

overcurrent setpoint

the ISEN pin

pin that will activate the OCP circuit

Overvoltage Protection

When an OVP fault is detected, the PGOOD pin will pull

down to 60

Ω and latch-off the converter. The OVP fault will

remain latched until the EN pin has been pulled below the

The OVP fault detection circuit triggers after the voltage

across the FB and GND pins has increased above the rising

latched-off in response to an OVP fault, the LG gate-driver

output will retain the ability to toggle the low-side MOSFET

on and off, in response to the output voltage transversing the

Undervoltage Protection

When a UVP fault is detected, the PGOOD pin will pull down

to 95

Ω and latch-off the converter. The fault will remain

latched until the EN pin has been pulled below the falling EN

detection circuit triggers after the voltage across the FB and

Over-Temperature

When the temperature of the ISL6269B increases above the

state that suspends the PWM , forcing the LG and UG

gate-driver outputs low. The status of the PGOOD pin does

not change nor does the converter latch-off. The PWM

remains suspended until the IC temperature falls below the

operation resumes. The OTP state can be reset if the EN pin

V

during OTP. It is likely that the IC will detect an UVP fault

because in the absence of PWM, the output voltage

converter. The UVP fault will remain latched until the EN pin

has been pulled below the falling EN threshold voltage

I

•

I

()

•

=

(EQ. 3)

(EQ. 4)

R

SEN

I

FL

I

PP

2

---------

+

⎝⎠

⎛⎞

OC

SP

•

r

DS on

()

•

I

OC

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=

ISL6269B