EN5330DI-T ENPIRION [Enpirion, Inc.], EN5330DI-T Datasheet - Page 7

• Manufacturer Part Number: EN5330DI-T
• Description: 3A Voltage Mode Synchronous Buck PWM DC-DC Converter
• Manufacturer: ENPIRION [Enpirion, Inc.]

Rev 1.0 – July 2005
Theory of Operation
Synchronous Buck Converter
The EN5330 is a synchronous, pin programmable
power supply with integrated power MOSFET
switches and inductor. The nominal input voltage
range is 2.5V-5.0V. The output can be set to common
voltages by connecting appropriate combinations of 3
voltage selection pins to ground. If different voltage
levels are required, provision is also made to allow
external programming. The feedback control loop is
voltage-mode and the part uses a low-noise PWM
topology. Up to 3A of output current can be drawn
from this converter. The 5MHz operating frequency
enables the use of small-size output capacitors.
The power supply also has protection features such as:
Additional features include:
Output Voltage Programming
The EN5330 output voltage is programmed using one
of two methods. Common output voltages are
achieved by tying one or more of the three Voltage
Select pins (VS0, VS1 & VS2) to ground (see Table
1). If all three are left floating, the output voltage and
over voltage thresholds are determined by the voltages
presented at the XFB and XOV pins respectively.
These voltages should be set by way of resistor
dividers between V
going to XFB and XOV (See Figure 1).
• Programmable over-current protection (to
• Thermal shutdown (to protect the converter
• Over-voltage protection that stops the PWM
• Under-voltage lockout circuit to disable the
• Soft-start circuit, limiting the in-rush current
• Power good circuit indicating whether the
protect the IC from excessive load current)
from getting too hot)
switching and turns on the lower N-MOSFET
at 120% of the programmed output voltage in
order to protect the load from an OV
condition.
converter output when the input voltage is less
than approximately 2.2V
when the converter is powered up.
output voltage is within 90%-120% of the
programmed voltage.
OUT
to AGND with the midpoint
7
It is recommended that Rb1 and Rb2 resistor values
be ~2kΩ. Use the following equation to set the
resistor Ra1 for the desired output voltage:
If over-voltage protection is desired, use the following
equation to set the resistor Ra2 for the desired OVP
trip-point:
By design, if both resistor dividers are the same, the
OV trip-point will be 20% above the nominal output
voltage.
Figure 1: External output voltage and OVP setting
Table 1: Output Voltage Select Table
* The VS0, VS1 and VS2 pins are defaulted to a ‘1’
with an internal pull-up resistor. Only connect
these pins to AGND if a ‘0’ is required. If a ‘1’ is
required, then leave the pin floating.
Ra
Ra
22µF
1
2
=
=
(
VS2*
(
Vout
** 0.8V ref only, not guaranteed performance
OVPtrip
0
0
0
0
1
1
1
1
15 nF
−
0
0
8 .
8 .
. 0
V
VS1*
−
V
AGND
PGND
SS
PVIN
AVIN
96
0
0
1
1
0
0
1
1
. 0
* )
96
V
Rb
PGND
V
VOUT
XOV
XFB
1
* )
VS0*
Rb
0
1
0
1
0
1
0
1
2
Ra2
Rb2
Output Voltage
User Selectable
EN5330
www.enpirion.com
AGND
0.8V**
1.25V
3.3V
2.5V
1.8V
1.5V
1.2V
Ra1
Rb1
V
47µF
OUT