en5310 Enpirion, en5310 Datasheet - Page 6

• Manufacturer Part Number: en5310
• Description: 1a Voltage Mode Synchronous Buck Pwm Dc-dc Converter With Integrated Inductor
• Manufacturer: Enpirion

Rev 1.01 – November 2006
Theory of Operation
Synchronous Buck Converter
The
programmable power supply with integrated
power MOSFET switches and inductor. The
nominal input voltage range is 2.5-5.0V. 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 1A 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 EN5310 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
• Programmable over-current protection (to
• Thermal
• Over-voltage protection that stops the
• Under-voltage lockout circuit to disable the
• Soft-start
• Power good circuit indicating whether the
protect the IC from excessive load current)
converter from getting too hot)
PWM 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
current when the converter is powered up.
output voltage is within 90%-120% of the
programmed voltage.
EN5310
shutdown
circuit,
is
a
limiting
synchronous,
(to
protect
the
in-rush
the
pin
6
(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
XOV.
Use an appropriate resistor ratio such that the
desired output voltage across the resistor pair
causes the XFB pin to be 0.8V at the nominal
set-point. It is recommended that the resistor
values used should be in the 20K-40K range.
Contact Enpirion Applications Support for more
specific information. If Over-Voltage protection is
required, the output of a second divider to XOV
should be set such that 0.96V is present at the
desired trip point. By design, if both resistor
dividers are the same, the OV trip-point will be
20% above the nominal output voltage.
Table 1: Output Voltage Select Table
*
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.
NOTE: The VS0, VS1 and VS2 pins are defaulted to a ‘1’
OUT
V
IN
VS2*
0
0
0
0
1
1
1
1
10µF
to GND with the midpoint going to XFB and
** 0.8V ref only, not guaranteed performance
VS1*
0
0
1
1
0
0
1
1
15 nF
POK
AGND
SS
PVIN
AVIN
VS0*
0
1
0
1
0
1
0
1
PGND
VOUT
XOV
XFB
Output Voltage
3.3V
2.5V
1.8V
1.5V
1.25V
1.2V
0.8V**
User Selectable
www.enpirion.com
V
22µF
OUT