EN5335QI Просмотр технического описания (PDF) - Altera Corporation
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EN5335QI Datasheet PDF : 15 Pages
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EN5335QI
Over-Current Protection
The current limit function is achieved by sensing
the current flowing through the sense P-
MOSFET. When the sensed current exceeds the
current limit, both NFET and PFET switches are
turned off. If the over-current condition is
removed, the over-current protection circuit will
enable the PWM operation. This circuit is
designed to provide high noise immunity.
The nominal over current trip point is set to 4.5A.
It is possible to increase the over-current set
point by about 50% by connecting a 7.5k
resistor between ROCP (pin 27) and GND. The
typical voltage at the ROCP pin is 0.75V.
Thermal Overload Protection
Thermal shutdown will disable operation once
the Junction temperature exceeds approximately
150ºC. Once the junction temperature drops by
approx 25ºC, the converter will re-start with a
normal soft-start.
Input Under-voltage Lock-out
Circuitry is provided to ensure that when the
input voltage is below the specified voltage
range, the converter will not start-up. Circuits for
hysteresis, input de-glitch and output leading
edge blanking are included to ensure high noise
immunity and prevent false tripping.
In some cases, such as the start-up of FPGA
devices, it is desirable to blank the over-current
protection feature. In order to disable over-
current protection, the ROCP pin should be tied
to any voltage between 2.5V and PVIN.
Over-Voltage Protection
When the output voltage exceeds 120% of the
programmed output voltage, the PWM operation
stops, the lower N-MOSFET is turned on and the
POK signal goes low. When the output voltage
drops below 95% of the programmed output
voltage, normal PWM operation resumes and
POK returns to its high state.
Compensation
The EN5335QI is internally compensated
through the use of a type 3 compensation
network and is optimized for use with about 50μF
of output capacitance and will provide excellent
loop bandwidth and transient performance for
most applications. (See the section on Capacitor
Selection for details on recommended capacitor
types.) Voltage mode operation provides high
noise immunity at light load.
In some cases modifications to the compensation
may be required. For more information, contact
Altera Power Applications support.
00846
10
October 11, 2013
www.altera.com/enpirion
Rev J
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