Click here to ask an associate for production status of specific part numbers.
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost
Converters
General Description
Benefits and Features
The MAX25239/MAX25240 are small, synchronous, buckboost converters with integrated H-bridge switches. These
ICs provide a fixed-output regulation voltage and an externally adjustable output voltage in the 3V to 20V range
with an input voltage above, below, or equal to the output
regulation voltage. The IC has typical 8.2A and 10A input
current limit options and can support continuous load currents up to 6A depending on the input-to-output voltage
ratio and operating frequency. It also has a wide input voltage range of 2V to 36V.
● Meets Stringent Automotive Quality and Reliability
Requirements
• 2V to 36V Operating Input Voltage Range Allows
Operation in Cold-Crank Conditions
• Tolerates Input Transients up to 42V
• EN Pin Compatible up to 42V
• 8.2A/10A Typical Input Current Limit
• Fixed and Adjustable Output Voltage Options
• -40°C to +125°C Grade 1 Automotive Temperature
Range
The MAX25239/MAX25240 have three switching frequency options: 2.1MHz, 400kHz, and 200kHz. The 2.1MHz
high switching frequency allows small external components and reduced output ripple, and guarantees no AM
band interference, while the 400kHz or 200kHz switching
frequency offers better efficiency and relieves the power
consumption concern. The SYNC input allows three operation modes: skip mode with ultra-low quiescent current,
forced fixed-frequency PWM operation, and synchronization to an external clock. The IC also includes spreadspectrum frequency modulation to minimize EMI interference.
● AEC-Q100 Qualified High Integration and Thermally
Enhanced Package Reduces BOM Cost and Board
Space
• Integrated FETs H-Bridge Architecture
• 2.1MHz/400kHz/200kHz Switching Frequency
Options
• Phase-Locked Loop (PLL) Frequency
Synchronization
• Thermally Enhanced, 22-Pin FC2QFN Package
The MAX25239/MAX25240 feature a power-OK (POK) indicator, undervoltage lockout, overvoltage protection, cycle-by-cycle current limit, and thermal shutdown. The ICs
are available in a small, 4.25mm x 4.25mm x 0.75mm,
22-pin FC2QFN package.
Applications
● ADAS ECU
● Infotainment Systems
● Low Quiescent Current Meets Stringent OEM Current
Requirements
• 95μA Quiescent Current in Standby Mode
• 10μA Maximum Shutdown Current
● Reduced EMI Emissions at Switching Frequency
• Spread-Spectrum Function Enabled/Disabled by
SPS Pin
● Protection Features Improve System Reliability
• Supply Undervoltage Lockout and Thermal
Protection
• Output PGOOD Indicator, Overvoltage, and ShortCircuit Protection
● Body Electronics
● Start-Stop Systems
● Point-of-Load Power Supplies
Ordering Information appears at end of data sheet.
19-101236; Rev 10; 6/23
© 2023 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners.
One Analog Way, Wilmington, MA 01887 U.S.A. | Tel: 781.329.4700 | © 2023 Analog Devices, Inc. All rights reserved.
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Simplified Block Diagram
SUP
PGOOD
MAX25239
MAX25240
OUT
UVLO VIN
POK
SHDN
PREREGULATOR
PGOOD
LOGIC
BANDGAP
AND
REFERENCES
FEEDBACKSELECT
LOGIC
FB
VCC
VIN_UVLO
1.8V VCC
REGULATOR
VBG
BST1
HS1
HS1
DRIVER
VFB
EAMP
VOVP_TH
COMP
LS1
DL1
PWM
COMP
PGND1
CLK
PLL/
OSCILLATOR
CONTROL
LOGIC
SLOPE COMP
∑
OUT
ICS
EXTERNAL
CLOCK
fSYNCSELECT
LOGIC
LX1
LS1 VCC
DRIVER
OVP
COMP
VCCS
SPREADSPECTRUM
ON/OFF
SYNCOUT
SYNC*
SUP
BST1_REFRESH
DH1
SOFT-START
SPS
BST1_REFRESH
VCC
THSD
AGND
VCC_UVLO
n
OTP
ICSLIM
IZX
VTH_REF
SUPPLY
SWITCHOVER
VTH_REF
UVLO VCC
ICSLIM
ILIM
COMP
ICS
BK_CS
BST2_REFRESH
HS2
DRIVER
BST2_REFRESH
HS2
DH2
FPWM/SKIP MODE
BST2
OUT
LX2
VIN_UVLO
VVCC_UVLO
IN
EN
EN
COMP
VCC
POK
LS2
DRIVER
LS2
DL2
SHDN
PGND2
POK
THSD
IZX
COMP
IZX
BST_CS
* SYNC CAN BE PROGRAMMED TO SYNCOUT. CONTACT ANALOG DEVICES FOR OPTIONS.
www.analog.com
Analog Devices | 2
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
TABLE OF CONTENTS
General Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Benefits and Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Simplified Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Package Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
22 FC2QFN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Typical Operating Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Pin Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
MAX25239/MAX25240 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Pin Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Detailed Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
H-Bridge Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Buck Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Boost Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Buck-Boost Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Linear Regulator Output (VCC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Soft-Start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Current-Limit/Hiccup Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Power-Good Output (PGOOD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Synchronization Input (SYNC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
System Enable (EN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Spread-Spectrum Option (SPS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Thermal Shutdown Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Applications Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Inductor Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Maximum Output Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Input Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Output Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Output Voltage Setting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Error Amplifier Compensation Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
PCB Layout Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Typical Application Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Ordering Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Revision History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
www.analog.com
Analog Devices | 3
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
LIST OF FIGURES
Figure 1. Output Voltage External Adjustment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 2. Compensation Network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Figure 3. 2.1MHz Application Circuit: ILIM = 8.2A, VOUT = 5V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Figure 4. 400kHz Application Circuit: ILIM = 10A, VOUT = 5V . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
www.analog.com
Analog Devices | 4
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Absolute Maximum Ratings
SUP, EN to AGND .................................................. -0.3V to +42V
LX1 to PGND1 .............................................. -0.3V to VSUP+0.3V
LX2 to PGND2 .............................................. -0.3V to VOUT+0.3V
OUT to AGND......................................................... -0.3V to +28V
BST1 to LX1, BST2 to LX2 .................................... -0.3V to +2.2V
BST1 to PGND1 ..................................................... -0.3V to +44V
BST2 to PGND2 ..................................................... -0.3V to +30V
VCC , SPS to AGND ............................................. -0.3V to +2.2V
COMP, FB to AGND ..................................... -0.3V to VVCC+0.3V
PGND_ to AGND ................................................... -0.3V to +0.3V
SYNC, PGOOD to AGND ......................................... -0.3V to +6V
ESD Protection
Human Body Model ........................................................... ±2kV
Machine Model ................................................................±100V
Continuous Power Dissipation (TA = +70°C, derate 30mW/°C
above +70°C) ..................................................................2404mW
Operating Junction Temperature ........................-40°C to +150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (Soldering 10s) .................................. +300°C
Soldering Temperature (reflow) ........................................ +260°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the
device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for
extended periods may affect device reliability.
Package Information
22 FC2QFN
Package Code
F224A4FY+1
Outline Number
21-100399
Land Pattern Number
90-100137
4-LAYER JEDEC BOARD
4-LAYER EV KIT
BOARD
Junction-to-Ambient Thermal Resistance (θJA)
33.3°C/W
22.4°C/W
Junction-to-Case (Top) Thermal Resistance (θJCt)
6.8°C/W
—
Junction-to-Case (Bottom) Thermal Resistance (θJCb)
6.4°C/W
7.5°C/W
Junction-to-Board Thermal Resistance (θJB)
7.6°C/W
9.6°C/W
Junction-to-Top Thermal Characterization Parameter (ΨJT)
3.3°C/W
3.3°C/W
Junction-to-Bottom Thermal Characterization Parameter (ΨJB)
8.5°C/W
9.4°C/W
THERMAL PARAMETERS
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages.
Note that a “+”, “#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different
suffix character, but the drawing pertains to the package regardless of RoHS status.
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a
four-layer board. For detailed information on package thermal considerations, refer to www.maximintegrated.com/
thermal-tutorial.
Electrical Characteristics
(VSUP = VEN = 14V, TJ = -40°C to +150°C, unless otherwise noted. Typical values are at TA = +25°C. Note 1 and Note 2.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
36
V
10
μA
SUP INPUT SUPPLY
SUP Voltage Range
VSUP
Shutdown Supply
Current
ISUP_SHUTDO
Standby Supply Current
ISUP_STANDB
SUP Undervoltage
Lockout
www.analog.com
Initial start up
4.5
VEN = 0V, TA = +25°C
5
VEN = VSUP, VOUT = 5V, no load,
VSYNC = 0V
95
VUVLO_RISE
VSUP rising
4.2
VUVLO_FALL
VSUP falling
WN
Y
μA
4.45
1.9
V
Analog Devices | 5
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Electrical Characteristics (continued)
(VSUP = VEN = 14V, TJ = -40°C to +150°C, unless otherwise noted. Typical values are at TA = +25°C. Note 1 and Note 2.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
VCC REGULATOR
VCC Output Voltage
VCC Undervoltage
Lockout
VVCC
VSUP > 3.5V, IVCC = 1mA to 50mA
1.8
V
VVCC falling
1.6
V
VVCC hysteresis, Note 3
100
mV
IVCC_SC
VCC shorted to AGND
50
mA
VOUT_5V
VFB = VVCC
4.9
5.0
5.1
VOUT_11P5
VFB = VVCC
11.27
11.5
11.73
VUVLO_VCC
VUVLO_VCC_H
YS
VCC Short-Circuit
Current Limit
BUCK-BOOST CONVERTER
Fixed Output Voltage
Soft-Start Ramp Time
tSOFT_START
Auto Retry Time
tAUTO
Minimum ON Time
tON_MIN
Dead Time
Auto retry time after an output short
condition is detected
V
2.5
ms
5
ms
In buck mode, fSW = 2.1MHz
100
In buck mode, fSW = 400kHz, Note 3
125
ns
tDEAD
Note 3
3
ns
LX1, LX2 Rise Time
tLX_RISE
Note 3
1.5
ns
LX1, LX2 Fall Time
tLX_FALL
Note 3
3
ns
VVCC = 1.8V, IDSON = 0.2A
20
POWER MOSFET
DMOS On-Resistance
RDSON_DMOS
LX1 Leakage Current
ILX1_LKG
LX2 Leakage Current
ILX2_LKG
35
mΩ
VEN = 0V, VSUP = VLX1 = 36V,
TA = +25°C
5
μA
VEN = 0V, VLX2 = 12V, TA = +25°C
5
μA
CURRENT SENSE
10A, Note 4
Current Limit
ILIM
8
10
12
8.2A
6.8
8.2
9.5
12A, Note 5
10
12
14
0.786
0.800
0.814
V
0.02
1
μA
A
ERROR AMPLIFIER
Regulated Feedback
Voltage
Feedback Leakage
Current
Transconductance (from
FB to COMP)
VFB
IFB_LKG
gM
VFB = 0.8V, TA = +25°C
VFB = 0.8V, VVCC = 1.8V
85
100
115
μS
400kHz option
350
400
450
kHz
1.9
2.1
2.3
MHz
SWITCHING FREQUENCY
PWM Switching
Frequency
SYNC External Clock
Input
Spread Spectrum
www.analog.com
fSW
fSYNC
SPS
2.1MHz option
Minimum sync
pulse of 100ns
400kHz option
280
520
kHz
2.1MHz option
1.5
2.7
MHz
±6
%
Analog Devices | 6
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Electrical Characteristics (continued)
(VSUP = VEN = 14V, TJ = -40°C to +150°C, unless otherwise noted. Typical values are at TA = +25°C. Note 1 and Note 2.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
106
108
110
%
OUTPUT MONITORS
Output Overvoltage
Threshold
VOUT_OVP
Output Overvoltage
Hysteresis
VOUT_OVP_H
PGOOD Threshold
VPGOOD_TH
PGOOD Output Low
Voltage
Detected with respect to VFB rising
3
YS
VPGOOD_LOW
%
% of VOUT, VOUT rising
92
94
96
% of VOUT, VOUT falling
91
93
95
ISINK = 1mA
PGOOD Leakage
Current
IPGOOD_LKG
VPGOOD = 5.5V, TA = +25°C
PGOOD Debounce
Time
tPGOOD_DB
Fault detection, rising and falling
%
0.2
V
1
μA
40
μs
LOGIC INPUTS (EN, SYNC, SPS)
Input High Level
VHIGH
Voltage rising
Input Low Level
VLOW
Voltage falling
1.3
V
Input Leakage Current
(EN, SPS)
IIN_LEAK
TA = +25°C
Input Leakage Current
(SYNC)
IIN_LEAK
TA = +25°C, SYNC = 1.8V, EN = high
20
0.5
V
1
μA
50
μA
THERMAL SHUTDOWN
Thermal Shutdown
Threshold
TSHDN
Note 3
175
°C
Thermal Shutdown
Hysteresis
TSHDN_HYS
Note 3
20
°C
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
All units are 100% production tested at +25°C. All temperature limits are guaranteed by design and characterization.
The device is designed for continuous operation up to TJ = +125°C for 95,000 hours and TJ = +150°C for 5,000 hours.
Guaranteed by design, not production tested.
Boost mode current limit.
Output short-circuit not allowed, see the Ordering Information table specifications for further details.
www.analog.com
Analog Devices | 7
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Typical Operating Characteristics
(TA=+25°C, unless otherwise noted.)
www.analog.com
Analog Devices | 8
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Typical Operating Characteristics (continued)
(TA=+25°C, unless otherwise noted.)
www.analog.com
Analog Devices | 9
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Typical Operating Characteristics (continued)
(TA=+25°C, unless otherwise noted.)
www.analog.com
Analog Devices | 10
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Typical Operating Characteristics (continued)
(TA=+25°C, unless otherwise noted.)
www.analog.com
Analog Devices | 11
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Pin Configuration
MAX25239/MAX25240
AGND
VCC
PGOOD
SYNC
SPS
COMP
FB
EN
TOP VIEW
22
21
20
19
18
17
16
15
BST1
1
SUP
MAX25239
MAX25240
2
13
OUT
SUP
3
12
OUT
NC
4
11
NC
PGND1
5
10
PGND2
PGND1
6
9
PGND2
7
8
LX2
BST2
LX1
14
22-PIN FC2QFN
4.25mm x 4.25mm
Pin Description
PIN
NAME
FUNCTION
1
BST1
Bootstrap Capacitor Connection for Switching Node LX1. Connect a 0.1μF ceramic capacitor
between LX1 and BST1.
2, 3
SUP
Power Supply of the Buck-Boost Converter and Internal VCC LDO Regulator. Bypass SUP to
PGND1 with a 4.7μF or larger ceramic capacitor.
4
NC
5, 6
PGND1
7
LX1
Buck-Boost Converter Switching Node 1. Connect LX1 to one side of the power inductor.
8
LX2
Buck-Boost Converter Switching Node 2. Connect LX2 to the other side of the power inductor.
9, 10
PGND2
Not Connected
Power Ground Connection for Buck Low-Side FET LS1. Connect PGND1 and PGND2 together to
power ground.
Power Ground Connection for Boost Low-Side FET LS2. Connect PGND1 and PGND2 together to
power ground.
11
NC
12, 13
OUT
Buck-Boost Converter Output.
14
BST2
Bootstrap Capacitor Connection for Switching Node LX2. Connect a 0.1μF ceramic capacitor
between LX2 and BST2.
15
EN
www.analog.com
Not Connected
High-Voltage-Tolerant Enable Input. Drive EN high to enable buck-boost converter.
Analog Devices | 12
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Pin Description (continued)
PIN
NAME
16
FB
17
COMP
18
SPS
19
SYNC
FUNCTION
Feedback Input. Connect FB to a resistor-divider between OUT and AGND to set the desired
output voltage in the range of 3V to 20V. Connect FB to VCC for the fixed output voltage option.
Error Amplifier Output. Connect an RC compensation network between COMP and AGND to
stabilize the control loop.
Spread-Spectrum (SPS) Function Enable Input. Connect SPS high to enable SPS function and low
to disable SPS function.
External Clock Synchronization and Skip/PWM Mode Control Input. Connect SYNC to AGND to
enable skip mode. Connect SYNC to VCC to enable PWM mode. Connect SYNC to a valid
external clock to synchronize the buck-boost converter switching frequency to external clock.
Open-Drain Power-Good Indicator. Pull up PGOOD with an external resistor to VCC or a positive
voltage lower than 5.5V to correctly indicate the OUT voltage status. PGOOD asserts low when the
OUT voltage falls below 93% (typ) of its regulation voltage. PGOOD becomes high impedance
when the OUT voltage rises above 94% (typ) of its regulation voltage. PGOOD is also in low during
soft-start and in shutdown.
20
PGOOD
21
VCC
Internal 1.8V Regulator Output. Bypass VCC to ground with a minimum 4.7μF ceramic capacitor.
22
AGND
Analog Ground. Connect AGND, PGND1, and PGND2 together at a single point in a star-ground
connection.
www.analog.com
Analog Devices | 13
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Detailed Description
The MAX25239/MAX25240 is a small, synchronous buck-boost converter family with integrated high-side and low-side
switches. The IC is designed to deliver up to 6.0A with input voltages from +2.0V to +36V while using only 95µA quiescent
current at no load. The MAX25239/MAX25240 family provides an accurate output voltage of ±2% within the normal
operation input range. Voltage quality can be monitored by observing the PGOOD signal.
The MAX25239/MAX25240 offers fixed output voltages and programmable output voltages in the range of 3V to
20V. Frequency is fixed with 200kHz, 400kHz, and 2.1MHz options. The 2.1MHz frequency allows for small external
components and reduced output ripple, and guarantees no AM interference. The IC automatically enters skip mode
at light loads with a low quiescent current of 95µA at no load. It can operate with ±6% spread-spectrum frequency
modulation designed to minimize EMI radiated emissions.
H-Bridge Operation
The MAX25239/MAX25240 H-bridge configuration is shown in the Simplified Block Diagram. The H-bridge consists of
the four switches HS1, LS1, HS2, and LS2. Switches HS1 and LS1 are in series with the input voltage, and switches HS2
and LS2 are connected to the output. The inductor is connected between LX1 and LX2. There are three operation modes
depending on the ratio of the input and output voltage: buck mode, boost mode, and buck-boost mode.
Buck Mode
When the input voltage is much higher than the output voltage, the MAX25239/MAX25240 operate in pure buck mode. In
this mode, switch HS2 is always on and switch LS2 is always off, while the switches HS1 and LS1 switch at the switching
frequency. The IC uses an peak-current-mode control scheme to determine the ON pulse width for the switches HS1 and
LS1. The switches HS1 and LS1 will alternate, behaving like a synchronous buck converter.
Boost Mode
When the input voltage is much lower than the output voltage, the MAX25239/MAX25240 operate in pure boost mode. In
this boost configuration, the switch HS1 is always on and the switch LS1 is always off, while the switches HS2 and LS2
are operating at the switching frequency. The MAX25240 uses an peak-current-mode control scheme to determine the
ON pulse width for the switches HS2 and LS2. The switches HS2 and LS2 switch as a synchronous boost converter.
Buck-Boost Mode
With the input voltage close to the output voltage, the MAX25239/MAX25240 operate in buck-boost mode. During the
buck-boost transition region, all four switches are turned on/off at the switching frequency as needed to maintain high
efficiency and regulated output voltage in the transition region.
Linear Regulator Output (VCC)
The devices include a 1.8V linear regulator (VCC) that provides power to the internal circuit blocks. Connect a 4.7μF
(min) ceramic capacitor from VCC to GND. During startup, the bias regulator draws power from the input and switches
over to the output after the startup is complete. For output voltages less than 1.8V, the bias regulator is always supplied
from the input.
Soft-Start
The MAX25239/MAX25240 include a 2.5ms soft-start time. Soft-start time limits startup inrush current by forcing the
output voltage to ramp up towards its regulation point. The soft-start ramp rate is set at 2.5ms.
Current-Limit/Hiccup Mode
The devices feature a current limit that protects the device against short-circuit and overload conditions at the output.
In the event of a short-circuit or overload condition, the high-side MOSFET remains on until the inductor current
reaches the high-side MOSFET’s current-limit threshold. The converter then turns on the low-side MOSFET to allow the
inductor current to ramp down. Once the inductor current crosses below the low-side MOSFET current-limit threshold,
the converter turns on the high-side MOSFET again. This cycle repeats until the short-circuit or overload condition is
removed.
www.analog.com
Analog Devices | 14
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
If the device reaches the current limit with an output voltage below 50% of the target, hiccup mode is enabled and the
output turns off for 5ms, then the IC attempts to power up through soft-start again.
Power-Good Output (PGOOD)
The devices feature an open-drain power-good indicator (PGOOD). The PGOOD asserts low when the output voltage
drops below the 93% (typ) falling threshold. The PGOOD deasserts when the output voltage rises above the 94% (typ)
rising threshold. Connect PGOOD to the output or external I/O voltage with a pullup resistor.
Synchronization Input (SYNC)
The SYNC pin is a logic-level input used for operating mode selection and frequency control. Connecting SYNC to VCC
or to an external clock enables forced fixed-frequency (FPWM) operation. Connecting SYNC to GND enables automatic
skip-mode operation for better light load efficiency. The external clock frequency at SYNC can be higher or lower than
the internal clock by 20%. The devices synchronize to the external clock in two cycles. When the external clock signal at
SYNC is absent for more than two clock cycles, the devices use the internal clock.
System Enable (EN)
An enable control input (EN) activates the devices from their low-power shutdown mode. EN is compatible with inputs
from the automotive battery level down to 1.8V. EN turns on the internal linear (VCC) regulator. Once VCC is above the
internal lockout threshold (VUVLO_VCC = 1.7V (typ)), the converter activates and the output voltage ramps up with the
programmed soft-start time.
A logic-low at EN shuts down the device. During shutdown, the VCC regulator and gate drivers turn off. Shutdown is the
lowest power state and reduces the quiescent current to 5μA (typ). Drive EN high to bring the device out of shutdown.
Spread-Spectrum Option (SPS)
When the SPS pin is tied high, the operating frequency is varied ±6% centered on the switching frequency.
The internal spread spectrum is disabled if the devices are synchronized to an external clock. However, the devices do
not filter the external clock on the SYNC pin and pass any modulation (including spread spectrum) present driving the
external clock.
Thermal Shutdown Protection
Thermal shutdown protects the device from excessive operating temperature. When the junction temperature exceeds
+175°C, the sensor shuts down the converter, allowing the IC to cool. The sensor turns the IC on again after the junction
temperature cools by 20°C. Thermal shutdown only disables the power switching, The VCC regulator and IC logic remain
active during thermal shutdown.
www.analog.com
Analog Devices | 15
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Applications Information
Inductor Selection
Design of the inductor is a compromise between the size, efficiency, control, bandwidth, and stability of the converter.
For a buck-boost application, selecting the right value of inductor becomes even more critical due to the presence of
right-half-plane (RHP) zero in boost and buck-boost mode. A larger inductance value would reduce RMS current loss
in MOSFETs, core, and winding losses in the inductor. On the other hand, it slows the control loop and reduces the
frequency of the RHP zero, which can cause stability concerns.
Start the selection of the inductor based on the inductor peak-to-peak current ripple as a percentage of the maximum
inductor current in buck and boost modes of operation using Equations 1, 2, and 3. Typically, 40% ripple of the maximum
inductor current is a good compromise between speed and efficiency.
Equation 1:
(VIN_MAX − VOUT) × VOUT
LBUCK = f
SW × ∆ ILP − P × VIN_MAX
where:
VIN_MAX = maximum input voltage
VOUT = output voltage
∆ILP-P = peak-to-peak current ripple of the inductor
fsw = switching frequency
Equation 2:
(VOUT_MAX − VIN) × VIN
LBOOST = f
SW × ∆ ILP − P × VOUT_MAX
where:
VIN = input voltage
VOUT_MAX = maximum output voltage
Select the larger of LBUCK and LBOOST as the final value of inductance L. Once the final value of inductance L is
selected, calculate the actual peak inductor current using Equations 3 and choose an inductor with saturation current
≈20% more than the peak inductor current and the low DC resistance (DCR).
Equation 3:
IL
VOUT × IOUT
= V
+
PEAK
IN_MIN × η
VIN_MIN × (1 −
VIN_MIN
VOUT
)
L × fSW × 2
where:
VIN_MIN = minimum input voltage
IOUT = output current
η = power conversion efficiency
L = inductor value
Maximum Output Current
The MAX25239/MAX25240 sense the peak inductor current to limit the output current. The maximum output current is
determined by the operating conditions and component selection that impact peak inductor current. At a heavy load and
high output voltage, thermal limitations impact the output current capability. Use θJA to estimate the junction temperature
at specific operating conditions to determine whether the device will trigger thermal shutdown.
www.analog.com
Analog Devices | 16
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Input Capacitor
The input capacitor reduces peak currents drawn from the power source and reduces noise and voltage ripple on the
input caused by the circuit switching. For operation in buck mode, the input capacitor sees high discontinuous input
current. Both the equivalent series resistance (ESR) and capacitance of the input capacitors cause the peak-to-peak
voltage ripple, calculated in Equation 4.
Equation 4:
(1 −
VOUT
VOUT
△ VIN = (1 − V ) × IOUT × ESR +
IN
VIN
) × IOUT × VOUT
fSW × VIN × CIN
where:
ESR = equivalent series resistance of the input capacitor
IOUT = output current
CIN = capacitance of the input capacitor
With the given maximum input voltage ripple, the input capacitance is calculated as in Equation 5.
Equation 5:
(1 −
VOUT
VIN
) × IOUT × VOUT
CIN = (V × △ V − (V − V
IN
IN
IN
OUT) × IOUT × ESR) × fSW
The selected input capacitor should be designed to handle the input RMS current of the input capacitor calculated by
Equation 6.
Equation 6:
ICIN
RMS
=
IOUTx√VOUTx(VIN − VOUT)
VIN
where:
ICINRMS = RMS current flowing through the input capacitor
The maximum input RMS current occurs at VIN = 2 x VOUT in Equation 7.
Equation 7:
ICIN
RMS(MAX)
=
IOUT
2
Select the input capacitors that can handle the given RMS current as the RMS current flowing through the capacitor’s
ESR will produce power loss to make the temperature rise. Ceramic capacitors are recommended for their low ESR, ESL,
small size, and high current ripple capability to bypass the pulsing ripple current, which helps reduce the peak-to-peak
voltage ripple at the input voltage and electromagnetic interference (EMI).
Output Capacitor
In boost mode, the output capacitors see high discontinuous ripple current. Both equivalent series resistance (ESR) and
capacitance of the output capacitors cause the voltage ripple, as calculated in Equation 8.
Equation 8:
△ VOUT =
VOUT × IOUT × ESR
VIN × η
+
IOUT × (1 −
VIN
)
VOUT
fSW × COUT
where:
ESR = equivalent series resistance of the output capacitor
COUT = capacitance of the output capacitor
www.analog.com
Analog Devices | 17
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
With the given maximum voltage ripple, the output capacitance is calculated as shown in Equation 9.
Equation 9:
(VOUT − VIN) × VIN × IOUT × η
COUT = ( △ V
OUT × VIN × η − VOUT × IOUT × ESR) × VOUT × fSW
When the input voltage reaches the minimum value, and the output voltage reaches the maximum value, the output
voltage is the largest.
Meanwhile the output capacitance is selected to satisfy the load transient requirements. During a load step, the output
current changes almost instantaneously, whereas the inductor is slow to react. During this transition time, the load-charge
requirements are supplied by the output capacitors, which causes an undershoot in the output voltage. Select a capacitor
based on the maximum allowable undershoot on the output voltage. Typically, the worst-case response from a load
transient is in boost mode. The output capacitance for the allowable undershoot is calculated under the load transient in
boost mode, as in Equation 10:
Equation 10:
△ IOUT
COUT = 2 × π × △ V
OUTUS × fC
where:
fC = crossover frequency
∆IOUT = transient load step
∆VOUTUS = maximum allowable undershoot
Select the larger output capacitance of Equation 9 and Equation 10 as the final value of the output capacitance COUT
that can handle the given RMS current at the operating frequency. Ceramic capacitors are recommended for their low
ESR, ESL, small size, and high current ripple capability to bypass the pulsing ripple current, which helps reduce the
peak-to-peak voltage ripple at the output voltage and electromagnetic interference (EMI). The RMS ripple current of the
output capacitors is calculated in Equation 11:
Equation 11:
ICOUT
RMS
= IOUT ×
√
VOUT − VIN
VIN
Output Voltage Setting
Connect FB to VCC to enable the fixed output voltage set by a preset internal resistive voltage-divider connected between
the feedback pin (FB) and AGND. To externally adjust the output voltage between 3V and 20V, connect a resistive
voltage-divider from the output (OUT) to FB to AGND, as shown in Figure 1. Calculate RFB1 and RFB2 using Equation
12.
Equation 12:
VOUT
RFB1 = RFB2[( V
) -1 ]
FB
where:
VFB = 0.8V (typ)
RFB2 < 50kΩ, can be typically set to 10kΩ
www.analog.com
Analog Devices | 18
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
VOUT
MAX25239
MAX25240
RFB1
FB
RFB2
Figure 1. Output Voltage External Adjustment
Error Amplifier Compensation Design
The MAX25240 converter uses an internal transconductance error amplifier, with its inverting input and output terminals
available to the user for external frequency compensation (see Figure 2).
The controller uses a peak current-mode-controlled architecture that regulates the output voltage by forcing the required
current through the external inductor. Current-mode control splits the double pole in the feedback loop caused by the
inductor and output capacitor into two single poles. One of the poles is moved to a high frequency outside the typical
bandwidth of the converter, making it a single-pole system. This makes compensation easy with just Type II required to
compensate the loop. In boost mode, an extra right half-plane (RHP) zero is introduced by the power stage that adds
extra phase delay in the control loop. To avoid any significant effect of the RHP zero on the converter stability, the
compensation is designed such that the bandwidth is approximately 1/5 of the worst-case RHP zero frequency.
The design of external compensation requires some iterations to reach an optimized design. Care must be taken while
designing the compensation for working in deep-boost mode and heavy load (VIN-MIN), as the RHP zero frequency
decreases.
A convenient way to design compensation for both buck and boost modes is to design the compensation at minimum
input voltage and heavy load (deep-boost mode). At this operating point, RHP zero is at its lowest frequency. Design the
compensation to achieve a bandwidth of 1/5 or lower of the RHP zero frequency to avoid significant effect of the RHP
zero on the converter stability. The closed-loop gain of the converter would be a combination of the power-stage gain of
the converter and error-amplifier gain, where the power stage’s pole and zero are calculated in Equation 13.
Equation 13:
1
fPBOOST = π × R
LOAD × COUT
1
fZESR = 2 × π × ESR × C
OUT
fZRHP =
RLOAD × (1 − D)2
2×π×L
where the error amplifier's pole and zero are calculated in Equation 14:
Equation 14:
1
1
fP1EA = 2 × π × (R + R ) × C ≈ 2 × π × R × C , ifREA > > RC
EA
C
C
EA
C
1
fP2EA = 2 × π × R × C
C
P
1
fZEA = 2 × π × R × C
C
C
where REA is the output impedance of the transconductance error amplifier with the value of approximately 5MΩ. ESR is
the equivalent series resistance of the output capacitors. RLOAD is the load resistance.
The target bandwidth for the closed-loop converter is selected to be 1/5 of the RHP zero. The zero of the error amplifier
www.analog.com
Analog Devices | 19
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
should be placed well below the bandwidth to give enough phase boost at the crossover frequency fC. Typically, the
zero of the transconductance error amplifier is placed close to the low-frequency pole fPBOOST of the power stage. The
second pole fP2EA of the transconductance error amplifier is placed close to the RHP zero of the power stage. In such a
case, the resistor RC and capacitors CC, CP of the compensation network are calculated using Equation 15.
Equation 15:
RC =
CC =
2 × π × Ri × COUT × VOUT × fC
(1 − D) × Gm × VREF
RLOAD × COUT
2 × RC
1
CP = 2 × π × R × f
C ZRHP
where:
Ri = 50mΩ current-sensing resistor
GM = 100μA/V gain of the transconductance error amplifier
fC = selected crossover frequency
VREF = 0.8V reference of the feedback voltage
The internal compensation network is shown in Figure 2.
VOUT
RFB1
VFB
GM
VCOMP
RFB2
RC
REA
VREF = 0.8V
CP
CC
Figure 2. Compensation Network
PCB Layout Guidelines
Careful PCB layout is critical to achieve low switching losses and clean, stable operation. Use a multilayer board
whenever possible for better noise immunity and power dissipation. Follow these guidelines for good PCB layout:
1. Place ceramic bypass capacitors close to the input and output pins to minimize high frequency current loops. This
improves efficiency and helps minimize radiated emissions.
2. Place VCC bypass capacitors close to the IC between the VCC and AGND pins.
3. Orient the input and output capacitors to minimize the distance between their ground connections.
4. Isolate the power ground from the analog ground whenever possible. Connect the power ground to the analog
ground with a star-ground connection at the AGND pin. This keeps the ground-current loops to a minimum. In cases
where only one ground is used, adequate isolation between the analog return signals and high-power signals must
be maintained.
5. Minimize trace inductance between the LX pins and BST capacitors, placing ceramic bootstrap capacitors as close
www.analog.com
Analog Devices | 20
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
as possible to the BST1 and BST2 pins.
6. Isolate the power components and high-current path from the sensitive analog circuitry in the compensation and
feedback loops. This is essential to prevent noise coupling into the analog signals.
7. Keep the high-current paths short, especially at the ground terminals. This practice is essential for stable, jitter-free
operation. The high-current path (composed of an input capacitor, high-side FET, inductor, and output capacitor)
should be as short as possible.
8. Keep the power traces and load connections short and wide. This practice is essential for high efficiency. Use thick
copper PCBs (2oz vs. 1oz) to enhance full-load efficiency and thermal dissipation.
9. The analog signal lines should be routed away from the high-frequency planes. This ensures the integrity of sensitive
signals feeding back into the device.
10. Place compensation components as close to the COMP pin as possible.
Typical Application Circuits
L
2.2µH
CBST2
0.1µF
CBST1
0.1µF
BST1
VBAT
LX1
LX2
BST2
SUP
VOUT
OUT
CIN
2 x 4.7µF
COUT
4x22µF
VCC
CVCC
4.7µF
MAX25239
FB
COMP
RC
SYNC
SPS
CF
EN
CC
PGOOD
AGND
PGND1
PGND2
Figure 3. 2.1MHz Application Circuit: ILIM = 8.2A, VOUT = 5V
www.analog.com
Analog Devices | 21
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Typical Application Circuits (continued)
L
4.7µH
CBST2
0.1µF
CBST1
0.1µF
BST1
VBAT
LX1
LX2
BST2
SUP
VOUT
OUT
COUT
4 x 22µF
CIN
2 x 4.7µF
VCC
CVCC
4.7µF
COMP
MAX25240
FB
RC
SYNC
SPS
CF
EN
CC
PGOOD
AGND
PGND1
PGND2
Figure 4. 400kHz Application Circuit: ILIM = 10A, VOUT = 5V
www.analog.com
Analog Devices | 22
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Ordering Information
CURRENT LIMIT
ILIM (A)
FIXED VOUT
OPTIONS (V) **
ADJ
VOUT (V)
SWITCHING
FREQUENCY (kHz)
MAX25239AFFA/VY+
8.2
5
6.5
2100
PART NUMBER
/V denotes an automotive-qualified part.
+ Denotes a lead(Pb)-free/RoHS-compliant package.
T Denotes tape-and-reel.
* Future product—contact factory for availability.
^ 18V max operating VIN, 5A max average IOUT.
** Contact factory for options that include:
• Fixed VOUT options from 3V to 15V
• SYNC input or output
• PGOOD assertion time delay options of 5ms and 10ms
www.analog.com
Analog Devices | 23
MAX25239/MAX25240
Automotive 2V to 36V, 6A Buck-Boost Converters
Revision History
REVISION
NUMBER
REVISION
DATE
0
11/21
Initial release
—
1
1/22
Updated Ordering Information table
23
2
2/22
Updated Ordering Information table
23
3
2/22
Updated Ordering Information table
23
4
3/22
Updated Ordering Information table
23
5
4/22
Updated Ordering Information table
23
6
7/22
Updated Ordering Information table
7
9/22
Updated Electrical Characteristics and Ordering Information table
8
12/22
Updated Ordering Information table
23
9
4/23
Updated Ordering Information table
23
10
6/23
Updated Package Information Thermal Parameters, Detailed Description,
Applications Information, and Figure 4
DESCRIPTION
PAGES
CHANGED
23
6, 23
5, 14, 18, 22
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is
assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may
result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of
their respective owners.
w w w . a n a l o g . c o m
Analog Devices | 24
工商网监
湘ICP备2023018690号
