USER’S MANUAL
AN1661
Rev 0.00
Sep 2, 2011
ISL80103EVAL2Z, ISL80102EVAL2Z
ISL80102, ISL80103 High Performance 2A and 3A LDOs Evaluation Board
User Guide
AN1661 Rev 0.00 Page 1 of 8
Sep 2, 2011
Description
The ISL80102 and ISL80103 are high performance, low
voltage, high current low dropout linear regulator specified at
2A and 3A, respectively. Rated for an input voltage from 2.2V
to 6V, these LDOs can provide outputs from 0.8V to 5V on the
adjustable version. The ISL80103EVAL2Z provides a simple
platform to evaluate performance of the ISL80102, ISL80103.
The ISL80103EVAL2Z evaluation board comes with the
adjustable output version of the IC. Jumpers are provided to
set the desired output voltage. Fixed output versions are
sampled in the accompanying kit.
The figures with operating conditions at 3A in this Application
Note are applicable only to the ISL80103. All other information
is applicable to both the ISL80102 and ISL80103.
What’s Inside
The evaluation kit contains the following:
• The ISL80103EVAL2Z
• Fixed output versions of either the ISL80102 or the
ISL80103
• The ISL80102, ISL80103 data sheet (FN6660
)
• This evaluation kit document
Required Equipment
The following equipment is recommended to perform the
tests:
• 0V to 6V power supply capable of sourcing at least 5A
• Electronic load capable of sinking up to 5A
• Digital multimeters
• 200MHz oscilloscope
Test Procedure
1) Select the desired output voltage by shorting one of the
jumpers from J1 through J6.
2) Ensure that output capacitor and Cpb are set according to
recommended values shown in Table 1.
3) Place jumper JP1 in the ‘enable’ position. It is
recommended to not leave the ENABLE pin floating.
4) Set the power supply for the desired input voltage and the
load as desired and connect them to the input and output of
the board, respectively.
5) Turn the power supply on and observe the output.
FIGURE 1. ISL80103EVAL2Z
AN1661 Rev 0.00 Page 2 of 8
Sep 2, 2011
ISL80103EVAL2Z, ISL80102EVAL2Z
Optimizing LDO Performance
Performance of the ISL80102, ISL80103 can be optimized by
following these simple guidelines.
Phase Boost Capacitor (CPB)
On the adjustable version of the ISL80102, ISL80103, phase
margin and crossover frequency can be increased by placing a
small capacitor across the top resistor in the feedback resistor
divider. Cpb and Rtop as shown in Figure 2 place a zero at
F
z
= 1/(2••R
TOP
•C
PB
)
The zero increases the crossover frequency of the LDO and
provides additional phase resulting in faster load transient
response.
Output Capacitor (COUT)
Output capacitor selection is important to achieve the desired
load transient performance. The ISL80102, ISL80103 uses state-
of-the-art internal compensation to be compatible with different
types of output capacitors, including multi-layer ceramic,
POSCAP and aluminum/tantalum electrolytic.
There is a growing trend to use very-low ESR multi-layer ceramic
capacitors (MLCC) for applications because they can support fast
load transients and also bypass very high frequency noise from
other sources. However, effective capacitance of MLCC's drops
with applied voltage, age and temperature. X7R and X5R
dielectric ceramic capacitors are strongly recommended as they
typically maintain a capacitance range within ±20% of nominal
over full operating ratings of temperature and voltage.
Table 1 gives the recommended values for output capacitor
(MLCC X5R/X7R) and C
PB
for different voltage rails.
The right selection of output capacitor and C
PB
also helps to
provide better PSRR at high frequencies.
Layout Guidelines
A good PCB layout is important to achieve expected
performance. Consideration should be taken when placing the
components and routing the trace to minimize the ground
impedance. Parasitic inductance should be kept to a minimum.
The input and output capacitors should have a good ground
connection and be placed as close to the IC as possible. The
‘SENSE’ trace in fixed voltage parts and the ‘ADJ’ trace in
adjustable voltage parts must be away from noisy planes and
traces.
ISL80102,
ISL80103
C
R
R
C
VV
ENABLE
SS
PG
C
ADJ
TOP
BOTTOM
PB
OUT
IN
IN
OUT
FIGURE 2. ISL80102, ISL80103 TYPICAL APPLICATION
TABLE 1.
V
OUT
R
TOP
R
BOTTOM
C
PB
C
OUT
5.0V 2.61kΩ 287Ω 47pF 10µF
3.3V 2.61kΩ 464Ω 47pF 10µF
2.5V 2.61kΩ 649Ω 47pF 10µF
1.8V
*
2.61kΩ 1.0kΩ 47pF 10µF
1.8V
*
2.61kΩ 1.0kΩ 82pF 22µF
1.5V 2.61kΩ 1.3kΩ 82pF 22µF
1.2V 2.61kΩ 1.87kΩ 150pF 47µF
1.0V 2.61kΩ 2.61kΩ 150pF 47µF
0.8V 2.61kΩ 4.32kΩ 150pF 47µF
NOTE: *Either option could be used depending on cost/performance
requirements