DATASHEET
ISL85005, ISL85005A
4.5V to 18V Input, 5A High Efficiency Synchronous Buck Regulator
The
ISL85005
and
ISL85005A
are monolithic, synchronous
buck regulators with integrated 5A, 18V high-side and low-side
FETs. These devices provide an integrated bootstrap diode for
the high-side gate driver to reduce the external parts count.
These devices also have a wide input voltage range to support
applications with input voltage from multi-cell batteries or
regulated 5V and 12V power rails.
The ISL85005 and ISL85005A regulate the output voltage
with current mode control and have an internal oscillator. The
switching frequency of the ISL85005 is internally set as
500kHz, and can be synchronized to an external clock signal
with frequency ranges from 300kHz to 2MHz. The ISL85005A
has a fixed 500kHz switching frequency.
The ISL85005 has a fixed 2.3ms soft-start, while the
ISL85005A features programmable soft-start to limit inrush
current during startup. With the SS pin floating, the soft-start
time of ISL85005A is also 2.3ms.
The ISL85005 can be configured in either forced Continuous
Conduction Mode (CCM) or Diode Emulation Mode (DEM). DEM
enables high efficiency at light-load conditions. The
ISL85005A always operates in forced CCM.
The ISL85005 and ISL85005A have built-in protections
including input UVLO protection, input and output overvoltage
protection, high-side cycle-by-cycle current limit, low-side
forward current limit and reverse current limit, and thermal
shutdown.
FN8871
Rev.2.00
May 17, 2018
Features
• 4.5V to 18V input voltage range
• Internal 5A, 18V high-side and low-side MOSFET switches
• ±1%, 0.8V feedback voltage reference
• Integrated bootstrap diode with undervoltage detection
• Current mode control with internal slope compensation
• Internal or external compensation options
• Default internally set 500kHz switching frequency
• Synchronization capability to external clock (ISL85005)
• Diode Emulation Mode (DEM) and Forced CCM (FCCM)
options (ISL85005)
• Adjustable soft-start time (ISL85005A)
• Output Power-Good (PG) indicator
• Input Undervoltage Lockout (UVLO), input and output
overvoltage protection
• High-side cycle-by-cycle current limit, low-side forward and
reverse overcurrent protection, and thermal shutdown
• Small 12-pin 3mmx4mm Dual Flat No-Lead (DFN) package
with EPAD for enhanced thermal performance
Applications
• Network and communications equipment
• Battery powered systems
• Multifunction printers
• Point-of-load regulators
• Standard 12V rail supplies
• Embedded computing systems
Related Literature
For a full list of related documents, visit our website
•
ISL85005, ISL85005A
product pages
Typical Application
95
GND = DEM; VCC = FCCM
MODE
PG
EN
R
2
C
1
1
ISL85005
V
IN
4.5V TO 18V
C
5
L
1
C
6
90
EFFICIENCY (%)
C
4
SYNC/
MODE
BOOT 12
VDD 11
VIN 10
PGND
VIN
PHASE
PHASE
9
8
7
85
80
75
70
65
60
55
50
0
1
2
3
4
5
OUTPUT CURRENT (A)
12V TO 5V
12V TO 3.3V
12V TO 1.8V
2 PG
3 EN
4 FB
C
3
R
1
5 COMP
6 AGND
V
OUT
5A MAX
C
9
C
8
FIGURE 1. ISL85005 WITH INTERNAL COMPENSATION
FIGURE 2. EFFICIENCY vs OUTPUT CURRENT
FN8871 Rev.2.00
May 17, 2018
Page 1 of 23
ISL85005, ISL85005A
Table of Contents
Typical Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Functional Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Pin Configurations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Pin Descriptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Typical Application Schematics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Thermal Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Recommended Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Typical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Typical Performance Curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Operation Initialization. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FCCM Control Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Light-Load Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Synchronization Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Enable, Soft-Start, and Disable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Voltage Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Protection Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Forward Overcurrent Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reverse Overcurrent Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Overvoltage Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input Overvoltage Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermal Overload Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Derating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Application Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Boot Undervoltage Detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Switching Regulator Output Capacitor Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Output Inductor Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input Capacitor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Loop Compensation Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15
15
15
15
16
16
16
16
16
16
16
16
16
17
17
17
18
18
19
Compensator Design Goal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
High DC Gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Layout Considerations. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Package Outline Drawing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
FN8871 Rev.2.00
May 17, 2018
Page 2 of 23
ISL85005, ISL85005A
Functional Block Diagram
1
SS (ISL85005A)
SOFT-START
CONTROL
BOOT
UVP
BOOT
12
SYNC/MODE (ISL85005)
1
VDD
11
UNDERVOLTAGE
LOCKOUT
OSCILLATOR
EN
LDO
VIN
9
10
CSA
2
PG
FAULT
MONITOR
CIRCUITS
EN
0.8V
REFERENCE
+
SLOPE
COMP
+
-
3
GATE DRIVE
CONTROL
CIRCUIT
EA
VDD
PHASE
7
8
+
THERMAL
SHUTDOWN
+
-
PGND
13
4
FB
600k
30pF
5
COMP
ZERO CROSS
DETECTOR
AND
NEGATIVE
CURRENT
LIMIT
POSITIVE
LS OCP
GND DETECTION
6
AGND
CIRCUIT
FIGURE 3. BLOCK DIAGRAM
FN8871 Rev.2.00
May 17, 2018
Page 3 of 23
ISL85005, ISL85005A
Pin Configurations
ISL85005
(12 LD 3x4 DFN)
TOP VIEW
ISL85005A
(12 LD 3x4 DFN)
TOP VIEW
SYNC/MODE
PG
EN
FB
COMP
AGND
1
2
3
4
5
6
12
11
10
9
8
7
BOOT
VDD
VIN
VIN
PHASE
PHASE
SS
PG
EN
FB
COMP
AGND
1
2
3
4
5
6
12
11
10
9
8
7
BOOT
VDD
VIN
VIN
PHASE
PHASE
PGND
(EPAD)
PGND
(EPAD)
Pin Descriptions
PIN
NUMBER
1
(ISL85005)
1
(ISL85005A)
2
PIN
NAME
SYNC/
MODE
SS
DESCRIPTION
Synchronization and mode selection input. Connect to VDD for Forced Continuous Conduction Mode (FCCM). Connect to AGND
for Diode Emulation Mode (DEM). Connect to an external function generator for synchronization with the positive edge trigger.
The internal 1MΩ pull-up resistor to VDD prevents an undefined logic state when SYNC is floating.
Soft-start input. This pin provides a programmable soft-start. When the chip is enabled, the regulated 3.5µA pull-up current
source charges a capacitor connected from SS to ground. The output voltage of the converter follows the ramping voltage on
this pin. Without the external capacitor, the default soft-start is 2.3ms.
Power-good, open-drain output. Connect a 10kΩ to 100kΩ pull-up resistor between PG and VDD or between PG and a voltage
not exceeding 5.5V. PG transitions high about 1.5ms after the switching regulator’s output voltage reaches the regulation
threshold, which is typically 85% of the regulated output voltage.
Enable input. The regulator is held off when the pin is pulled to ground. The device is enabled when the voltage on this pin rises
above 0.6V.
Feedback input. The synchronous buck regulator employs a current mode control loop. FB is the negative input to the voltage
loop error amplifier. The output voltage is set by an external resistor divider connected to FB. The output voltage can be set to
any voltage between the power rail (reduced by converter losses) and the 0.8V reference.
Compensation node. This pin is connected to the output of the error amplifier and compensates the loop. Internal
compensation meets most applications. Connect COMP to AGND to select internal compensation. Connect a compensation
network between COMP and FB to use external compensation.
The AGND terminal. Provides the return path for the core analog control circuitry within the device. Connect AGND to the board
ground plane. AGND and PGND are connected internally within the device. Do not operate the device with AGND and PGND
connected to dissimilar voltages.
Phase switch output node. Connect to the external output inductor.
Voltage supply input. The main power input for the IC. Connect to a suitable voltage supply. Place a ceramic capacitor from VIN
to PGND, close to the IC for decoupling.
Low dropout linear regulator decoupling pin. VDD is the internally generated 5V supply voltage and is derived from VIN. The
VDD powers all the internal core analog control blocks and drivers. Connect a 1µF capacitor from VDD to the board ground
plane. If VIN is between 3V to 5.5V, then connect VDD directly to VIN to improve efficiency.
Bootstrap input. A floating bootstrap supply pin for the upper power MOSFET gate driver. Connect a 0.1µF capacitor between
BOOT and PHASE.
Power ground terminal. Provides thermal relief for the package and is connected to the source of the low-side output MOSFET.
Connect PGND to the board ground plane using as many vias as possible. AGND and PGND are connected internally within the
device. Do not operate the device with AGND and PGND connected to dissimilar voltages.
PG
3
4
EN
FB
5
COMP
6
AGND
7, 8
9, 10
11
PHASE
VIN
VDD
12
(EPAD)
BOOT
PGND
FN8871 Rev.2.00
May 17, 2018
Page 4 of 23
ISL85005, ISL85005A
Ordering Information
PART NUMBER
(Notes
2, 3, 4)
ISL85005FRZ
ISL85005FRZ-T
ISL85005FRZ-TK
ISL85005FRZ-T7A
ISL85005AFRZ
ISL85005AFRZ-T
ISL85005AFRZ-TK
ISL85005AFRZ-T7A
ISL85005AEVAL1Z
ISL85005ADEMO1Z
ISL85005EVAL1Z
ISL85005DEMO1Z
NOTES:
1. Refer to
TB347
for details about reel specifications.
2. 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.
3. For Moisture Sensitivity Level (MSL), see the
ISL85005, ISL85005A
product information pages. For more information about MSL, refer to
TB363.
4. The ISL85005 is provided with a frequency synchronization input. The ISL85005A is a version of the part with programmable soft-start.
PART
MARKING
005F
005F
005F
005F
005A
005A
005A
005A
Evaluation Board
Demonstration Board
Evaluation Board
Demonstration Board
TEMP. RANGE
(°C)
-40 to +125
-40 to +125
-40 to +125
-40 to +125
-40 to +125
-40 to +125
-40 to +125
-40 to +125
OPTION
SYNC
SYNC
SYNC
SYNC
SOFT-START
SOFT-START
SOFT-START
SOFT-START
FREQUENCY
(kHz)
500
500
500
500
500
500
500
500
TAPE AND REEL
PACKAGE
(UNITS) (Note
1)
(RoHS COMPLIANT)
-
6k
1k
250
-
6k
1k
250
12 Ld DFN
12 Ld DFN
12 Ld DFN
12 Ld DFN
12 Ld DFN
12 Ld DFN
12 Ld DFN
12 Ld DFN
PKG.
DWG. #
L12.3x4
L12.3x4
L12.3x4
L12.3x4
L12.3x4
L12.3x4
L12.3x4
L12.3x4
TABLE 1. KEY DIFFERENCES BETWEEN FAMILY OF PARTS
PART NUMBER
ISL85005A
ISL85005
ISL85003
ISL85003A
INTERNAL/EXTERNAL
COMPENSATION
Yes
Yes
Yes
Yes
EXTERNAL FREQUENCY
SYNC
No
Yes
Yes
No
PROGRAMMABLE
SOFT-START
Yes
No
No
Yes
SWITCHING
FREQUENCY (kHz)
500
500
500
500
CURRENT
RATING
5A
5A
3A
3A
FN8871 Rev.2.00
May 17, 2018
Page 5 of 23
