DATASHEET
ISL854102
Wide V
IN
1.2A Synchronous Buck Regulator
The
ISL854102
is a 1.2A synchronous buck regulator with an
input range of 3V to 40V. It provides an easy-to-use, high
efficiency, low BOM count solution for a variety of applications.
The ISL854102 integrates both high-side and low-side NMOS
FETs and features a PFM mode for improved efficiency at light
loads. This feature can be disabled if a forced PWM mode is
needed. The ISL854102 switches at a default frequency of
500kHz; however, it can also be programmed using an
external resistor from 300kHz to 2MHz. The ISL854102 has
the ability to use internal or external compensation. By
integrating both NMOS devices and providing internal
configuration options, minimal external components are
required, which reduces the BOM count and design complexity.
With a wide VIN range and reduced BOM, the ISL854102
provides an easy to implement design solution for a variety of
applications while giving superior performance. The
ISL854102 provides a very robust design for high-voltage
industrial applications and an efficient solution for battery
powered applications.
The ISL854102 is available in a small Pb-free 4mmx3mm DFN
plastic package with a full-range industrial temperature of
-40°C to +125°C.
FN8870
Rev.1.00
Mar 15, 2019
Features
• Wide input voltage range: 3V to 40V
• Synchronous operation for high efficiency
• No compensation required
• Integrated high-side and low-side NMOS devices
• Selectable PFM or forced PWM mode at light loads
• Internal fixed frequency (500kHz) or adjustable switching
frequency (300kHz to 2MHz)
• Continuous output current up to 1.2A
• Internal or external soft-start
• Minimal external components required
• Power-good and enable functions available
Applications
• Industrial control
• Medical devices
• Portable instrumentation
• Distributed power supplies
• Cloud infrastructure
Related Literature
For a full list of related documents, visit our website:
•
ISL854102
device page
100
95
90
EFFICIENCY (%)
1 SS
2
SYNC
FS 12
COMP
FB
GND
VCC
PG
EN
11
R
2
10
9
C
VCC
1µF
R
3
C
FB
85
80
75
70
65
60
55
50
0
0.1
0.2 0.3 0.4 0.5 0.6 0.7
0.8
0.9
VIN=12V
VIN=15V
VIN=24V
1
1.1
1.2
C
BOOT
100nF
V
OUT
C
OUT
10µF
L
1
22µH
3 BOOT
C
VIN
10µF
4 VIN
5 PHASE
6
PGND
INTERNAL DEFAULT PARAMETER SELECTION
OUTPUT LOAD (A)
FIGURE 1. TYPICAL APPLICATION
FIGURE 2. EFFICIENCY vs LOAD, PFM, V
OUT
= 5V, L
1
= 22µH
FN8870 Rev.1.00
Mar 15, 2019
Page 1 of 21
ISL854102
Table of Contents
Pin Configuration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pin Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Typical Application Schematics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Functional Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Thermal Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Recommended Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Efficiency Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Soft-Start. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power-Good . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PWM Control Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Light Load Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Voltage Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Protection Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Overcurrent Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Negative Current Limit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Over-Temperature Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Boot Undervoltage Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Application Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Simplifying the Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Operating Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Minimum On/Off-Time Limitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Synchronization Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Inductor Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Buck Regulator Output Capacitor Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loop Compensation Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13
13
13
13
13
14
14
14
15
15
15
15
15
15
15
15
16
16
16
16
Layout Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Package Outline Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
FN8870 Rev.1.00
Mar 15, 2019
Page 2 of 21
ISL854102
Pin Configuration
12 LD 4x3 DFN
TOP VIEW
SS 1
SYNC 2
BOOT 3
VIN 4
PHASE 5
PGND 6
GND
12 FS
11 COMP
10 FB
9
8
7
VCC
PG
EN
Pin Descriptions
PIN NUMBER
1
SYMBOL
SS
PIN DESCRIPTION
Controls the soft-start ramp time of the output. A single capacitor from the SS pin to ground determines the
output ramp rate. See
“Soft-Start” on page 13
for soft-start details. If the SS pin is tied to VCC, an internal
soft-start of 2ms is used.
Synchronization and light load operational mode selection input. Connect to logic high or VCC for PWM
mode. Connect to logic low or ground for PFM mode. Logic ground enables the IC to automatically choose
PFM or PWM operation. Connect to an external clock source for synchronization with positive edge trigger.
The sync source must be higher than the programmed IC frequency. An internal 5MΩ pull-down resistor
prevents an undefined logic state if SYNC is left floating.
Floating bootstrap supply pin for the power MOSFET gate driver. The bootstrap capacitor provides the
necessary charge to turn on the internal N-Channel MOSFET. Connect an external 100nF capacitor from this
pin to PHASE.
The input supply for the power stage of the regulator and the source for the internal linear bias regulator.
Place a minimum of 4.7µF ceramic capacitance from VIN to GND and close to the IC for decoupling.
Switch node output. It connects the switching FETs with the external output inductor.
Power ground connection. Connect directly to the system GND plane.
Regulator enable input. The regulator and bias LDO are held off when the pin is pulled to ground. When the
voltage on this pin rises above 1V, the chip is enabled. Connect this pin to VIN for automatic start-up. Do not
connect the EN pin to VCC because the LDO is controlled by EN voltage.
Open-drain, power-good output that is pulled to ground when the output voltage is below regulation limits or
during the soft-start interval. There is an internal 5MΩ internal pull-up resistor.
Output of the internal 5V linear bias regulator. Decouple to PGND with a 1µF ceramic capacitor at the pin.
Feedback pin for the regulator. FB is the inverting input to the voltage loop error amplifier. COMP is the
output of the error amplifier. The output voltage is set by an external resistor divider connected to FB. In
addition, the PWM regulator’s power-good and UVLO circuits use FB to monitor the regulator output voltage.
COMP is the output of the error amplifier. When it is tied to VCC, internal compensation is used. When only
an RC network is connected from COMP to GND, external compensation is used. See
“Loop Compensation
Design” on page 16
for more details.
Frequency selection pin. Tie to VCC for 500kHz switching frequency. Connect a resistor to GND for adjustable
frequency from 300kHz to 2MHz.
Signal ground connections. Connect to the application board GND plane with at least five vias. All voltage
levels are measured with respect to this pin. The EPAD MUST NOT float.
2
SYNC
3
BOOT
4
5
6
7
VIN
PHASE
PGND
EN
8
9
10
PG
VCC
FB
11
COMP
12
EPAD
FS
GND
FN8870 Rev.1.00
Mar 15, 2019
Page 3 of 21
ISL854102
Typical Application Schematics
1
2
SS
FS
12
11
R
2
10
C
FB
SYNC
BOOT
GND
VIN
PHASE
COMP
3
C
BOOT
100nF
C
VIN
10µF
V
OUT
C
OUT
10µF
L
1
22µH
4
5
6
FB
9
VCC
C
VCC
1µF
R
3
PG
EN
PGND
FIGURE 3. INTERNAL DEFAULT PARAMETER SELECTION
1
C
SS
2
SS
FS
12
R
FS
SYNC
3
C
BOOT
100nF
C
VIN
10µF
V
OUT
C
OUT
10µF
L
1
22µH
5
6
4
BOOT
GND
VIN
PHASE
COMP
11
R
2
10
C
FB
FB
9
VCC
C
VCC
1µF
R
3
PG
EN
R
COMP
C
COMP
PGND
FIGURE 4. USER PROGRAMMABLE PARAMETER SELECTION
TABLE 1. EXTERNAL COMPONENT SELECTION
V
OUT
(V)
12
5
3.3
2.5
1.8
L
1
(µH)
22
22
22
22
12
C
OUT
(µF)
2 x 22
47 + 22
47 + 22
47 + 22
47 + 22
R
2
(kΩ)
90.9
90.9
90.9
90.9
90.9
R
3
(kΩ)
4.75
12.4
20
28.7
45.5
C
FB
(pF)
22
27
27
27
27
R
FS
(kΩ)
115
DNP (Note
1)
DNP (Note
1)
DNP (Note
1)
DNP (Note
1)
R
COMP
(kΩ)
150
100
100
100
70
C
COMP
(pF)
470
470
470
470
470
NOTE:
1. Connect FS to VCC.
FN8870 Rev.1.00
Mar 15, 2019
Page 4 of 21
ISL854102
Functional Block Diagram
SS
EN
PG
VIN
FB
EN/SOFT-
START
FB
600mV VREF
FS
POWER-
GOOD
LOGIC
5M
VCC
BIAS
LDO
BOOT
FAULT
LOGIC
500mV/A
CURRENT SENSE
PWM
GATE
DRIVE AND
PWM DEADTIME
OSCILLATOR
PFM
CURRENT
SET
PWM/PFM
SELECT LOGIC
FB
s Q
R Q
PHASE
SYNC
5M
ZERO CURRENT
DETECTION
450mV/T SLOPE
COMPENSATION
(PWM ONLY)
150k
INTERNAL = 50µA/V
EXTERNAL = 230µA/V
PGND
INTERNAL
54pF COMPENSATION
PACKAGE
PADDLE
COMP
GND
FIGURE 5. FUNCTIONAL BLOCK DIAGRAM
Ordering Information
PART NUMBER
(Notes
3, 4)
ISL854102FRZ
ISL854102FRZ-T
ISL854102FRZ-T7A
ISL854102EVAL1Z
ISL854102DEMO1Z
ISL854102DEMO2Z
ISL854102DEMO3Z
NOTES:
2. See
TB347
for details about reel specifications.
3. These Pb-free plastic packaged products employ special Pb-free material sets, molding compounds/die attach materials, and 100% matte tin plate
plus anneal (e3 termination finish, which is RoHS compliant and compatible with both SnPb and Pb-free soldering operations). Pb-free products are
MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
4. For Moisture Sensitivity Level (MSL), see the
ISL854102
device page. For more information about MSL, see
TB363.
4102
4102
4102
PART
MARKING
TEMP. RANGE
(°C)
-40 to +125
-40 to +125
-40 to +125
TAPE AND REEL
(Units) (Note
2)
-
6k
250
PACKAGE
(RoHS Compliant)
12 Ld DFN
12 Ld DFN
12 Ld DFN
L12.4x3
L12.4x3
L12.4x3
PKG.
DWG. #
Buck regulator evaluation board
Buck regulator demonstration board (compact version)
Dual output Isolated buck converter
Dual output Isolated buck-boost converter
FN8870 Rev.1.00
Mar 15, 2019
Page 5 of 21
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