en5335 Enpirion, en5335 Datasheet - Page 9

• Manufacturer Part Number: en5335
• Description: 3a Voltage Mode Synchronous Buck Pwm Dc-dc Converter With Integrated Inductor 3-pin Programmable Output
• Manufacturer: Enpirion

Rev 1.0 November 2006
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 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.
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
Design Considerations for Lead-Frame Based Modules
Exposed Metal on Bottom Of Package
Lead frame offers many advantages in thermal performance, in reduced electrical lead resistance,
and in overall foot print. However, they do require some special considerations.
In the assembly process lead frame construction requires that, for mechanical support, some of the
lead-frame cantilevers be exposed at the point where wire-bond or internal passives are attached.
This results in several small pads being exposed on the bottom of the package.
Only the large thermal pad and the perimeter pads are to be mechanically or electrically connected to
the PC board. The PCB top layer under the EN5335QI should be clear of any metal except for the
large thermal pad. The “grayed-out” area in Figure 4 represents the area that should be clear of any
metal (traces, vias, or planes), on the top layer of the PCB.
©Enpirion 2006 all rights reserved, E&OE
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.
Compensation
The
through the use of a type 3 compensation
network and is optimized for use with about 47µF
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
Enpirion Applications Engineering support.
9
EN5335QI
is
internally
www.enpirion.com
compensated
EN5335QI