EP5348UI Datasheet, PDF (8/12 Pages) Enpirion, Inc. – 400mA Synchronous Buck Regulator with Integrated Inductor

MOSFET which is compared to a reference
current. When this level is exceeded the P-
FET is turned off and the N-FET is turned on,
pulling V_OUT low. This condition is maintained
for approximately 0.5mS and then a normal
soft start is initiated. If the over current
condition still persists, this cycle will repeat.
Under Voltage Lockout
During initial power up an under voltage
lockout circuit will hold-off the switching
circuitry until the input voltage reaches a
sufficient level to ensure proper operation. If
the voltage drops below the UVLO threshold,
the lockout circuitry will disable the switching.
Hysteresis is included to prevent chattering
between states.
EP5348UI
Enable
The ENABLE pin provides a means to shut
down the converter or enable normal
operation. A logic low will disable the
converter and cause it to shut down. A logic
high will enable the converter into normal
operation.
NOTE: The ENABLE pin must not be left
floating.
Thermal Shutdown
When excessive power is dissipated in the
chip, the junction temperature rises. Once the
junction temperature exceeds the thermal
shutdown threshold, the thermal shutdown
circuit turns off the converter output voltage
thus allowing the device to cool. When the
junction temperature decreases by 15C°, the
device will go through the normal startup
process.
Application Information
Output Voltage Programming
A 5pF MLCC capacitor C_A is also required in
parallel with R_A for compensation.
V_IN
C_IN
2.2µF
0603
0.1µF
C_AVIN
PVIN
VOUT
AVIN
EP5348
C_A
R_A
ENABLE
VFB
AGND PGND
R_B
V_OUT
C_OUT
10µF
0603
Input Filter Capacitor
C_{IN_MIN} = 2.2µF 0603 case size or larger.
The input capacitor must use a X5R or X7R or
equivalent dielectric formulation. Y5V or
equivalent dielectric formulations lose
capacitance with frequency, bias, and with
temperature, and are not suitable for switch-
mode DC-DC converter input filter applications.
Figure 3: Typical Application Circuit
Output Filter Capacitor
The EP5348UI uses a simple resistor divider to
program the output voltage.
Referring to Figure 3, use 200 kΩ, 1% or better
for the upper resistor (R_A). The value of the
bottom resistor (R_B) in kΩ is given as:
R_B
=
VFB * R_A
(V_OUT −VFB)
VFB = 0.6V nominal
C_{OUT_MIN} = 10uF 0603 + 2.2uF 0603 MLCC
when 4.5V ≤ V_IN ≤ 5.5V, AND I_OUT > 300mA.
C_{OUT_MIN} = 10uF 0603 MLCC for all other use
cases. However, ripple performance can
always be improved by adding a second 2.2uF
or 1uF output capacitor for any operating
condition.
V_OUT has to be sensed at the last output filter
capacitor next to the EP5348UI. Any additional
bulk capacitance for load decoupling and
byass has to be far enough from the V_OUT
©Enpirion 2012 all rights reserved, E&OE
05721
8
September 12, 2012
www.enpirion.com
Rev: C