en5366 Enpirion, en5366 Datasheet - Page 11

• Manufacturer Part Number: en5366
• Description: 6a Voltage Mode Synchronous Buck Pwm Dc-dc Converter With Integrated Inductor External Output Voltage Programming
• Manufacturer: Enpirion

September 2007
Where the soft-start time T
the soft-start capacitance C
Typically, a capacitor of around 15 nF is
recommended.
During the soft-start cycle, when the soft-start
capacitor reaches 0.75V, the output has reached
its programmed regulation range. Note that the
soft-start current source will continue to operate,
and during normal operation, the soft-start
capacitor will charge up to a final value of 2.5V.
POK Operation
The POK signal is an open drain signal from the
converter indicating the output voltage is within
the specified range. The POK signal will be a
logic high when the output voltage is within 90% -
120% of the programmed output voltage. If the
output voltage goes outside of this range, the
POK signal will be a logic low until the output
voltage has returned to within this range. In the
event of an over-voltage condition the POK
signal will go low and will remain in this condition
until the output voltage has dropped to 95% of
the programmed output voltage before returning
to the high state.
The internal POK FET is designed to tolerate up
to 4mA.
chosen to limit the current from exceeding this
value when POK is logic low.
Over-Current Protection
The current limit function is achieved by sensing
the current flowing through a 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 re-enable the
PWM operation. If the over-current condition
persists, the circuit will continue to protect the
load.
©Enpirion 2007 all rights reserved, E&OE
The pull-up resistor value should be
T
SS
= C
SS
* 75KΩ (seconds)
SS
is in seconds and
SS
is in Farads.
11
The OCP trip point is nominally set to 150% of
maximum rated load. For diagnostic purposes, it
is possible to increase the OCP trip point to
approximately 200% of the maximum rated load
by connecting a 10k Ω resistor between the
ROCP pin (pin 38) and AGND (pin 39). This is
intended for troubleshooting purposes only and
the specification is not guaranteed.
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.
Thermal Overload Protection
Thermal shutdown will disable operation when
the Junction temperature exceeds approximately
150ºC. Once the junction temperature drops by
approx 20ºC, 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 required voltage level
(V
not start-up. Circuits for hysteresis and input de-
glitch are included to ensure high noise immunity
and to prevent false tripping.
Parallel Device Operation
The EN5366QI is capable of paralleling up to a
total of four converters to provide up to 24A of
continuous current. Please refer to the Parallel
Operation Application note, available on the
Enpirion website www.enpirion.com, for details
on parallel operation.
UVLO
) for normal operation, the converter will
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EN5366QI