User’s Manual
ISL854102DEMO3Z
User’s Manual: Demonstration Board
Industrial Analog and Power
Rev.0.00
Sep 2017
USER’S MANUAL
ISL854102DEMO3Z
Demonstration Board
UG137
Rev.0.00
Sep 12, 2017
1.
Overview
The ISL854102DEMO3Z board uses the ISL854102 in an isolated buck-boost configuration. The primary output is
configured to be -5V and the secondary output is +5V. The board is used to demonstrate the performance of the
ISL854102
wide V
IN
synchronous buck regulator, configured as a buck-boost converter to support an inverting
primary output and a non-inverting secondary output.
The ISL854102 is the higher current version of the family of ISL85410 (1A), ISL854102 (1.2A), and ISL85418
(0.8A), which are offered in a 4mmx3mm 12 Ld DFN package with 1mm maximum height.
1.1
Key Features
• Wide input voltage range of 3.5V to 40V
• Synchronous operation for high efficiency
• Integrated high-side and low-side NMOS devices
• Internal fixed (500kHz) or adjustable (300kHz to 2MHz) switching frequency
• Continuous output current up to 0.5A at primary output and 0.5A at secondary output
• Internal or external soft-start
• Minimal external components required
• Power-good and enable functions available
1.2
Specifications
These boards have been configured and optimized for the following operating conditions:
• V
IN
= 24V
• V
OUT_PRI
= -5V, V
OUT_SEC
= +5V
• I
MAX_PRI
= 0.5A, I
MAX_SEC
= 0.5A
• f
SW
= 500kHz
1.3
Ordering Information
Part Number
Description
ISL854102 demonstration board
ISL854102DEMO3Z
1.4
Related Literature
•
ISL854102
product page
• For a full list of related documents, visit our website
UG137 Rev.0.00
Sep 12, 2017
Page 2 of 17
ISL854102DEMO3Z
1. Overview
+
C
OUT
R
L
VOUT_SC
-
VIN
+
EN
VIN
C
IN
SYNC
COMP
VCC
-
C
VCC
VNEG
SS
FS
GND
PHASE
C
3
R
1
BOOT
FB
PG
R
2
-
VOUT_PR
C
OUT
+
ISL854102
Figure 1. Block Diagram
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Sep 12, 2017
Page 3 of 17
ISL854102DEMO3Z
2. Functional Description
2.
2.1
Functional Description
Recommended Equipment
The following materials are recommended for testing:
• 0V to 50V power supply with at least 2A source current capability
• Resistive loads capable of sinking current up to 1A
• Digital Multimeters (DMMs)
• 100MHz quad-trace oscilloscope
2.2
Quick Setup Guide
(1) Ensure that the circuit is correctly connected to the supply and loads before applying any power.
(2) Connect the bias supply to VIN, the plus terminal to VIN, and the negative return to GND.
(3) Verify that SW1 is in the ON position.
(4) Turn on the power supply.
(5) Verify the output voltage is -5V for V
NEG
and between 5.0V to 5.5V for V
OUT_SC
.
2.3
Evaluating the Other Output Voltage
The ISL854102DEMO3Z board outputs are preset to ±5V; however, output voltages can be adjusted from 0.6V to
15V. The output voltage programming resistor, R
2
, will depend on the desired output voltage of the regulator and
the value of the feedback resistor R
1
, as shown in
Equation 1.
0.6
-
R
2
=
R
1
-----------------------------
V
OUT
–
0.6
(EQ. 1)
If the output voltage desired is 0.6V, then R
1
is shorted. Note that if V
OUT
is less than 1.8V, the switching frequency
and compensation must be changed for 300kHz operation due to minimum on-time limitation. Refer to the
ISL854102
datasheet for further information.
Table 1
shows the component selection that should be used for the respective V
OUT
.
Table 1. External Component Selection
V
OUT
(V)
12
5
3.3
L
1
(µH)
47
22
22
C
5
+ C
6
(µF)
2x22
47+22
47+22
R
1
(kΩ)
90.9
90.9
90.9
R
2
(kΩ)
4.75
12.4
20
C
4
(pF)
100
220
100
R
12
(kΩ)
DNP
(Note
1)
DNP
(Note
1)
DNP
(Note
1)
R
3
(kΩ)
200
80.6
80.6
C
7
(pF)
2200
2200
2200
C
8
(pF)
100
100
100
R
15
(kΩ)
1.5
0.56
0.3
Note:
1. Connect FS to V
CC
.
2.4
Frequency Control
The ISL854102 has an FS pin that controls the frequency of operation. Programmable frequency allows for
optimization between efficiency and external component size. It also allows low frequency operation for low
V
OUTs
when minimum on-time would limit the operation otherwise. The default switching frequency is 500kHz
when FS is tied to V
CC
(R
13
= 0). By removing R
13
, the switching frequency can be changed from 300kHz
(R
14
= 340k) to 2MHz (R
14
= 32.4k). Refer to
ISL854102
datasheet for calculating the value of R
14
. Do not leave
this pin floating.
UG137 Rev.0.00
Sep 12, 2017
Page 4 of 17
ISL854102DEMO3Z
2. Functional Description
2.5
Disabling/Enabling Function
The ISL854102DEMO3Z board contains a SW1 switch that enables or disables the part, thus allowing low quiescent
current state.
Table 2
details this function.
Table 2. Switch Settings
S1
ON
OFF
Enable V
OUT
Disable V
OUT
On/Off Control
2.6
SYNC Control
The ISL854102DEMO3Z board has a SYNC pin that allows an external synchronization frequency to be applied.
The default board configuration has R
9
= 200k connected to V
CC
, which defaults to PWM operation mode and also
to the preselected switching frequency set by R
14
. See the
ISL854102
datasheet and previous section
“Frequency
Control” on page 4
for details.
2.7
Soft-Start/COMP Control
R
11
selects between internal (R
11
= 0) and external soft-start. R
8
selects between internal (R
8
= 0) and external
compensation. For applications in which repetitive restarts of the IC are required, a 350kΩ resistor in parallel to
CSS is recommended to allow its fast discharge. Refer to the pin description table of the
ISL854102
datasheet.
UG137 Rev.0.00
Sep 12, 2017
Page 5 of 17
Microcontroller MCU
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