Application Note 1767
2
AN1767.0
June 27, 2012
Features
• Complete dual low dropout regulator (LDO)
• Easy to use board for evaluation of the LDO in a target
application
• Exposed soldering pads/pins for monitoring VIN, VO1, VO2,
POR1, POR2, and CBYP
• Voltage monitoring using test pins, banana jacks and scope
jacks
• Enable jumpers for each supply, plus jumpered enable
pull-down resistors
• The board has options for:
- Changing the CPOR capacitor
- Using a logic analyser/pattern generator to monitor
enable/POR response
What is Inside
The Evaluation Kit contains:
• ISL9000A Evaluation board
• ISL9000A Data Sheet
• ISL9000A Evaluation Board Users Guide (this document)
What is Needed
The following instruments will be needed to perform testing (not
provided):
• DC 6.5V/1A Power supply
• Two Digital Voltmeters (4.5 digit or better)
• Oscilloscope
• 2 channel, 0 to 400mA electronic load
• Cables and wires
Quick Setup Guide
Step 1: Place shunts on J3 between “EN1” and HI”, on J4
between “EN1” and HI”, and on J10 (CPOR). This is the
factory default connection.
Step 2: Set the power supply to 3.8V with a 1.0A current limit
(then turn off).
Step 3: Connect the power supply between VIN and GND using
connector J2.
Step 4: Connect two voltmeter positive leads to the VO1 “kelvin”
connector (J13-1, “V1K”) and the VO2 “kelvin” connector
(J13-5, “V2K”). The meters can also be connected to the
VO power pins J2-2 and J2-4 or the banana jacks, but at
higher currents, these won’t reflect the output voltage as
accurately as the kelvin connections.
Connect the negative leads to GND J13-3. (To get the best
representation of the IC output voltage under all output
loading conditions, add a ground terminal to the GNDk
pad and connect the meter ground leads there).
Step 5: Connect a third voltmeter to the input. This can be
connected to the J2 terminal, but at higher inputs, the VIk
terminal will give the most accurate reading of the
voltage at the ISL9000A VIN pin.
Step 6: (Optional) Connect an electronic load to one or both of
the outputs. For the VO1 output, use the VO1 power
connector J2-2 (“V1P”). For the VO2 output, use the VO2
power connector J2-4 (“V2P”).
Step 7: Monitor VO1 and VO2. The voltages should reflect the
voltage of the selected part. For example, the
ISL9000AIRNJZ-EVZ
board should have 3.3V and 2.8V
outputs.
Step 8: Change the loading on each output and monitor the
output voltages
Step 9: Change the input voltage and monitor the effect on the
output voltages
For additional testing, such as load transient and line transient
response, adding the optional scope jacks will improve the
measurement, by reducing external noise. The Scope Jack part
number is included in the bill of materials as an optional
component.
If desired, banana jacks can be added to the board to facilitate
connection of the board to test equipment. Part numbers for
these optional components are included in the bill of materials.
Improved PSRR and noise specs can be obtained by replacing
the 0.01
μ
F (C3) capacitor with a 0.1
μ
F capacitor.
