EP5348UI Datasheet, PDF (9/12 Pages) Enpirion, Inc. – 400mA Synchronous Buck Regulator with Integrated Inductor

sensing point so that it does not interfere with
the control loop operation. Excess total
capacitance on the output (Output Filter + Bulk)
can cause an over-current condition at startup.
Please see the Soft Start section under
Functional Overview for the maximum
allowable bulk capacitance on the output rail.
The output capacitor must use a X5R or X7R
or equivalent dielectric formulation. Y5V or
equivalent dielectric formulations lose
capacitance with frequency, bias, and
temperature and are not suitable for switch-
mode DC-DC converter output filter
applications.
LDO Replacement
The Enpirion EP5348UI is a suitable
replacement for inefficient LDOs and can be
used to augment the LDOs in a PMU with
minimum footprint impact. This integrated
DCDC solution offers significantly better
efficiency, and significant reduction in power
loss. The resulting improved thermals and
extended battery life helps meet Energy Star
requirements. The total solution size is 25%
smaller than a comparable LDO and half the
footprint of a comparable DCDC.
Layout Recommendations
EP5348UI
As the table below shows, EP5348UI provides
the optimal trade-off between footprint and
efficiency when compared to a traditional LDO:
VIN VOUT LOAD EFF EFF
(V) (V) (mA) DCDC LDO
PLOSS
DCDC
(mW)
5.0 1.2 400 70.4% 24.0% 202
5.0 1.8 400 76.4% 36.0% 222
5.0 2.5 400 81.6% 50.0% 225
5.0 3.3 400 87.7% 66.0% 185
3.3 1.2 400 77.1% 36.4% 143
3.3 1.8 400 83.3% 54.5% 144
3.3 2.5 400 88.2% 75.8% 134
PLOSS
LDO
(mW)
1520
1280
1000
680
840
600
320
Power Saved
(mW)
1318
1058
775
495
697
456
186
Power-Up/Down Sequencing
During power-up, ENABLE should not be
asserted before PVIN, and PVIN should not be
asserted before AVIN. The PVIN should never
be powered when AVIN is off. During power
down, the AVIN should not be powered down
before the PVIN. Tying PVIN and AVIN or all
three pins (AVIN, PVIN, ENABLE) together
during power up or power down meets these
requirements.
Pre-Bias Start-up
The EP5348UI does not support startup into a
pre-biased condition. Be sure the output
capacitors are not charged or the output of the
EP5348UI is not pre-biased when the
EP5348UI is first enabled.
Figure 4: Top PCB Layer Critical Components and
Copper for Minimum Footprint
Figure 5: Bottom PCB Layer Critical Components
(R_A, R_B, C_A) & Copper for Minimum Footprint
©Enpirion 2012 all rights reserved, E&OE
05721
9
September 12, 2012
www.enpirion.com
Rev: C