en5366 Enpirion, en5366 Datasheet - Page 9

• 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
Theory of Operation
Synchronous Buck Converter
The EN5366 is a synchronous, programmable
power supply with integrated power MOSFET
switches and integrated inductor. The nominal
input voltage range is 2.4-5.5V. The output
voltage is programmed using an external resistor
divider network. The feedback control loop is a
type III voltage-mode and the part uses a low-
noise PWM topology. Up to 6A of continuous
output current can be drawn from this converter.
The 5MHz operating frequency enables the use
of small-size input and output capacitors.
The power supply has the following protection
features:
Additional features include:
Output Voltage Programming
The EN5366 output voltage is programmed using
a simple resistor divider network. Figure 4 shows
the resistor divider configuration.
The EN5366 output voltage and over voltage
thresholds are determined by the voltages
presented at the XFB and XOV pins respectively.
These voltages are set by way of resistor dividers
between V
to XFB and XOV.
©Enpirion 2007 all rights reserved, E&OE
• Programmable over-current protection (to
• Short Circuit protection.
• Thermal shutdown with hysteresis.
• Programmable over-voltage protection.
• Under-voltage lockout circuit to disable the
• Soft-start circuit, to limit the in-rush current
• Power
protect the IC from excessive load
current).
converter output when the input voltage is
less than approximately 2.2V
when the converter is powered up.
whether the output voltage is between
90% of nominal V
point.
OUT
and AGND with the midpoint going
good
circuit
OUT
and the OVP trip
(POK)
indicating
9
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 4. V
Input Capacitor Selection
The EN5366QI requires between 40-80uF of
input capacitance. Low ESR ceramic capacitors
are required with X5R or X7R dielectric
formulation.
formulations must not be used as these lose
capacitance with frequency, temperature and
bias voltage.
In some applications, lower value ceramic
capacitors maybe needed in parallel with the
larger capacitors in order to provide high
frequency decoupling.
Ra
Ra
V
IN
1
2
=
=
47µF
(
(
C
Vout
OVPtrip
SS
OUT
PVIN
AGND
AVIN
−
SS
. 0
and OVP resistor divider networks.
. 0
75
75
. 0
−
V
Y5V
90
V
. 0
POK
V
* )
90
V
Rb
PGND
VOUT
* )
XOV
XFB
or
1
Rb
equivalent
2
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R
R
a2
b2
R
R
b1
a1
EN5366QI
dielectric
47µF
V
OUT