ISL85003EVAL2Z, ISL85003AEVAL2Z
Evaluation Board User Guide
AN1930 Rev.1.00
Page 1 of 5
Aug 28, 2014
AN1930
Rev.1.00
Aug 28, 2014
USER’S MANUAL
Description
The ISL85003 and ISL85003A kits are intended for use for
point-of-load applications sourcing from 4.5V to 18V. The kits
are used to demonstrate the performance of the ISL85003
and ISL85003A, low quiescent current high efficiency
synchronous buck regulators.
The ISL85003 and ISL85003A are offered in a 4x3mm dual flat
no lead (DFN) package.
Specifications
The boards are designed to operate at the following operating
conditions:
• Input voltage range from 4.5V to 18V
• Resistor programmable output voltage from 0.8V,
±
1%
• Up to 3A output current
• Current mode control
- DCM/CCM
- Internal or external compensation options
- 500kHz switching frequency option
- External synchronization up to 2MHz on ISL85003
• Adjustable soft-start time on the ISL85003A
• Operating junction temperature range: -40°C to +125°C
Quick Setup Guide
1. Ensure that the circuit is correctly connected to the supply
and loads prior to applying any power.
2. Connect the bias supply to VIN, the plus terminal to VIN (P4)
and the negative return to PGND (P5).
3. Connect the output load to V0, the plus terminal to V0 (P8)
and the negative return to PGND (P9).
4. Verify that the position is PWM or PFM for SW2.
5. Verify that the position is ON for SW1.
6. Turn on the power supply.
7. Verify the output voltage is 5V for VO.
Recommended Equipment
The following materials are recommended to perform testing:
• 0V to 25V power supply with at least 10A source current
capability
• Electronic loads capable of sinking current up to 7A
• Digital multimeters (DMMs)
• 100MHz quad-trace oscilloscope
• Signal generator
Key Board Features
• Small, compact design
• Switch selectable EN (enabled/disabled)
• Switch selectable MODE (auto-DCM/forced-PWM)
• Connectors and test points for easy probing
References
•
ISL85003
,
ISL85003A
datasheet
Evaluating the Other Output
Voltage
The ISL85003 and ISL85003A kit outputs are preset to 5V for
V
OUT
; however, the output voltages are programmed using an
external resistor divider that scales the feedback relative to the
internal reference voltage. The output voltage programming
resistor, R
2
, will depend on the value chosen for the feedback
resistor, R
1
, and the desired regulator output voltage, V
OUT
.
The value for the feedback resistor R
1
is typically between
10k
Ω
and 400k
Ω
as shown in
Equation 1
.
If the output voltage desired is 0.8V, then R
2
is left
unpopulated. R
1
is still required to set the low frequency pole
of the modulator compensation.
Switch Control
The ISL85003 and ISL85003A evaluation boards contain SW1
and SW2 for various controls of the ISL85003 and ISL85003A
circuitries.
Table 1
details this function.
Ordering Information
PART NUMBER
DESCRIPTION
ISL85003EVAL2Z
Evaluation Board for ISL85003FRZ and
ISL85003AFRZ
TABLE 1. SWITCH SETTINGS
SW1
ENABLE
FUNCTION
1
OFF
Disable V0
3
ON
Enable V0
SW2
MODE
FUNCTION
1
DCM
Force DCM
3
PWM
Fixed PWM frequency at light load
R
2
R
1
0.8V
V
OUT
0.8V
–
-------------------------------
=
(EQ. 1)
