Application Report
SNVA748 – January 2016
Maintaining Output Voltage Regulation During Automotive
Cold-Crank with LM5140 Dual Synchronous Buck
Converter
Terry Allinder
Designing electronics to operate from a 12-V car supply is challenging. The 12-V battery supply voltage
can range from 9-16V under normal operation depending on charge and load variation. However, the
transient battery voltage range can be much wider. One of these conditions is cold-crank. Cold-crank
occurs when the battery is trying to energize the starter-motor circuits on the internal combustion engine.
Traditionally, only a few critical functions were required to ride through the cold-crank. Increasing car
manufactures are making more features available through cold-cranks for a better driver experience and
safety.
The cold-crank profile is described by ISO 7637-2 (test pulse 4). Individual car manufacturers have similar
cold-crank profiles with the supply rail dropping to 3 V or lower depending on the location of the load. An
example cold-crank profile is shown in Figure 1. The actual voltage levels and time intervals are
manufacturer specific.
Supply
12 V
6V
3V
5 ms
15 ms to
40 ms
50 ms
0.5 s to 20 s
5 ms to 100 ms
time
Figure 1. A Representative (Cold-Crank) Test Profile for Car Supply with 12V Battery
To keep the safety and convenience functions such as navigation, entertainment, dashboard, LED break
lights and headlights working through drops in the battery profile, the DC-DC converter supplying these
loads must be able to maintain regulation even when the 12-V supply voltage drops below the required
output voltage.
The LM5140, a Dual Synchronous Buck controller, can maintain regulation on the 3.3V output even at
supply voltages of 3.8 V, and on the 5.0 V output it can maintain output voltage regulation with the battery
voltage dropping down to 5.5V. With an absolute maximum voltage rating of 60 V, it can survive load
dump transients with ease. In addition, the LM5140’s oscillator can switch at 2.2 MHz reducing to size of
the output inductor and filter capacitor providing small solution size. The LM5140 incorporates features to
simplify the compliance with the CISPR and Automotive EMI requirements. The LM5140 has two
selectable switching frequencies, 2.2 MHz and 440 kHz, Gate Drivers with Adaptive Slew Rate Control,
and Interleaved (180 degree output of phase) operation of the two outputs.
All trademarks are the property of their respective owners.
SNVA748 – January 2016
Submit Documentation Feedback
Maintaining Output Voltage Regulation During Automotive Cold-Crank with
LM5140 Dual Synchronous Buck Converter
Copyright © 2016, Texas Instruments Incorporated
1
www.ti.com
The LM5140 Dual Synchronous Buck converter schematic is shown in Figure 3 with an operating input
voltage range of 3.8 V to 42 V with the ability to withstand load dump transients up to 42 V. Figure 2
shows a cold-crank test condition. The converter maintains the output voltage even when the input supply
voltage drops below 3.8 V.
Figure 2. VOUT Regulated at 3.3V with VIN 3.8V for 20ms (Load 4A)
2
Maintaining Output Voltage Regulation During Automotive Cold-Crank with
LM5140 Dual Synchronous Buck Converter
Copyright © 2016, Texas Instruments Incorporated
SNVA748 – January 2016
Submit Documentation Feedback
www.ti.com
VIN
VIN 4 - 42VDC
TP8
L1
J2
VCC VIN
VCCX VDDA
VOUT2
R39
1
2
C40
47µF
4
3
1715721
VOUT1
ZX1
Assembly Note
2.2MHz 3.3V/5.0V
S1A
1
7447798360
15.0k
C39
10µF
C41
0.1µF
C7
1µF
4
S1B
C8
1µF
2
3
2
1
VIN
R34
1.0
T1
PA2756NL
VIN
C42
C43
D1
2.2µF
C12
1
1040
2.2µF
C19
2.2µF
C38
SGND
D2
C11
SGND
C23
0.1µF
R17
0
PMEG6010CEJ,115
1
1040
J5
C21
0.47µF
2.2µF
2.2µF
C28
PMEG6010CEJ,115
2.2µF
J4
2.2µF
C29
2.2µF
SGND
19
R15
17
10.0
Q1
SQJ850EP-T1-GE3
27
33pF
TP2
26
SGND
EN1
R37
C44
100k DNP82µF
VDDA
2
1
EN1
SGND
TP5
S2A
5-146261-1
1
36
SW1
SW2
LO1
LO2
LOL1
LOL2
PGND1
PGND2
U1
CS1
CS2
LM5140RHA
VOUT1
ZX3
Assembly Note
5.0V @ 5A MAX
L3
10
R29
R21
10.0
12
4
R22
14
10.0
4
Q4
SQJ850EP-T1-GE3
R25
DNP
1.40k
0.009
C31
DNP
0.1µF
R26
R27
DNP
100 DNP
100
DNPC30
1000pF
R28
49.9
C32
TP13
R30
0
C33
47µF
C34
82µF
C35
C36
82µF DNP82µF
5
PG2
7
31
EN1
EN2
40
38
SYN_IN
SYN_OUT
39
29
COMP1
COMP2
2
28
FB1
FB2
3
30
SS1
SS2
1
TP14
SGND
VOUT2
R24
DNP
1.00
SYNC_OUT
EN2
TP9
C45
DNP82µF
VDDA
EN2
R38
100k
2
5
J10
1
2
S3A
1
5-146261-1
6
R32
43.0k
3
R11
10.0k
4
R3
20.0k
C15
22pF
PG1 BIAS
SGND
C18
0.01µF
33
35
37
C20
0.01µF
C22
0.068µF
C25
47pF
C27
0.01µF
C14
0.01µF
FB1 - VDDA = 3.3V
R23
10.0k
5
S3C
3
R33
20.0k
4
PG2 BIAS
C26
0.01µF
FB2 - VDDA = 5.0V
J6
FB1 - RDIV = 3.5V
SGND
FB2 - RDIV = 5.5V
1
FB1 - GND = 5V
SGND
C16
0.068µF
2
TP11
R18
10.0k
R16
6.49k
C13
0.01µF
S3B
PG2
ILSET
TP3
S2C
R31
10.0
SGND
TP10
SGND
PG1
C37
0.1µF
33pF
VOUT2
SGND
S2B
VOUT2
MSS1038-252NLB
0
13
PG1
6
5,6,
7,8
VDDA
R20
Q3
SQJ850EP-T1-GE3
4
1,2,3
25
6
VIN
VCCX
16
VCC
VCC
8
34
R2
43.0k
HOL2
32
R1
10.0
J1
SYNC_IN
HOL1
24
VOUT1
R10
DNP
1.00
10.0
R19
5,6,
7,8
7,8
5,6,
4
9
B170-13-F
DNP
18
10.0
HO2
D4
0.1µF
R7
R8
DNP
100
100 DNP
21
R14
HO1
1,2,3
C6
23
C24
0.1µF
11
DEMB
R6
49.9
22
SGND
HB2
DAP
C5
47µF
R4
0
1,2,3
C4
82µF
D3
C3
82µF
B170-13-F
0.1µF
C2
DNP82µF
R9
DNP
1.40k
1000pF
C1
C9
DNP
C10
0.006
HB1
AGND
0
R5
TP1
15
R13
MSS1038-152NLB
20
OSC
L2
C17
0.1µF
10.0
1,2,3
VOUT1 ZX2
Assembly Note
3.3V @ 6A MAX
Q2
SQJ850EP-T1-GE3
R12
RES
4
SGND
ILSET
7,8
5,6,
SGND
SGND
FB2 - GND = 1.8V
1040
VDDA
TP6
VDDA
VDDA
1
2
3
R41
1.00k
CJS-1201TA
SGND
SGND
1
S7
4
R36
DNP
0
OSC - VDDA = 2.2MHz
OSC - GND= 460KHz
EN1
3
CJS-1201TA
SGND
EN2
S5B
2
PG1 BIAS
2
3
1
CJS-1201TA
DEMB - GND = DEMB
DEMB - VDDA = FPWM
S6A
3
0
2
ILSET
3
CJS-1201TA
R35
S9
1
SYNC_IN
S5A
SGND
S8
1
SGND
VCC
VIN
ILSET
S4
2
VIN
TP7
VDDA
SYNC_IN
SGND
1
R40
4
S6B
1.00k
PG2 BIAS
2
3
SGND
Figure 3. LM5140 2.2MHz EVM Schematic
SNVA748 – January 2016
Submit Documentation Feedback
Maintaining Output Voltage Regulation During Automotive Cold-Crank with
LM5140 Dual Synchronous Buck Converter
Copyright © 2016, Texas Instruments Incorporated
3
www.ti.com
References
ISO 7637-2: Road vehicles - Electrical disturbances from conduction and coupling -Part 2: Electrical
transient conduction along with supply lines only.
LM5140 Wide Input Range Dual Synchronous Buck Controller
Cranking Simulator Reference Design for Automotive Applications (PMP7233)
4
Maintaining Output Voltage Regulation During Automotive Cold-Crank with
LM5140 Dual Synchronous Buck Converter
Copyright © 2016, Texas Instruments Incorporated
SNVA748 – January 2016
Submit Documentation Feedback
Revision History
www.ti.com
Revision History
DATE
REVISION
NOTES
January 2016
*
Initial release.
SNVA748 – January 2016
Submit Documentation Feedback
Revision History
Copyright © 2016, Texas Instruments Incorporated
5
IMPORTANT NOTICE
Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other
changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest
issue. Buyers should obtain the latest relevant information before placing orders and should verify that such information is current and
complete. All semiconductor products (also referred to herein as “components”) are sold subject to TI’s terms and conditions of sale
supplied at the time of order acknowledgment.
TI warrants performance of its components to the specifications applicable at the time of sale, in accordance with the warranty in TI’s terms
and conditions of sale of semiconductor products. Testing and other quality control techniques are used to the extent TI deems necessary
to support this warranty. Except where mandated by applicable law, testing of all parameters of each component is not necessarily
performed.
TI assumes no liability for applications assistance or the design of Buyers’ products. Buyers are responsible for their products and
applications using TI components. To minimize the risks associated with Buyers’ products and applications, Buyers should provide
adequate design and operating safeguards.
TI does not warrant or represent that any license, either express or implied, is granted under any patent right, copyright, mask work right, or
other intellectual property right relating to any combination, machine, or process in which TI components or services are used. Information
published by TI regarding third-party products or services does not constitute a license to use such products or services or a warranty or
endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the
third party, or a license from TI under the patents or other intellectual property of TI.
Reproduction of significant portions of TI information in TI data books or data sheets is permissible only if reproduction is without alteration
and is accompanied by all associated warranties, conditions, limitations, and notices. TI is not responsible or liable for such altered
documentation. Information of third parties may be subject to additional restrictions.
Resale of TI components or services with statements different from or beyond the parameters stated by TI for that component or service
voids all express and any implied warranties for the associated TI component or service and is an unfair and deceptive business practice.
TI is not responsible or liable for any such statements.
Buyer acknowledges and agrees that it is solely responsible for compliance with all legal, regulatory and safety-related requirements
concerning its products, and any use of TI components in its applications, notwithstanding any applications-related information or support
that may be provided by TI. Buyer represents and agrees that it has all the necessary expertise to create and implement safeguards which
anticipate dangerous consequences of failures, monitor failures and their consequences, lessen the likelihood of failures that might cause
harm and take appropriate remedial actions. Buyer will fully indemnify TI and its representatives against any damages arising out of the use
of any TI components in safety-critical applications.
In some cases, TI components may be promoted specifically to facilitate safety-related applications. With such components, TI’s goal is to
help enable customers to design and create their own end-product solutions that meet applicable functional safety standards and
requirements. Nonetheless, such components are subject to these terms.
No TI components are authorized for use in FDA Class III (or similar life-critical medical equipment) unless authorized officers of the parties
have executed a special agreement specifically governing such use.
Only those TI components which TI has specifically designated as military grade or “enhanced plastic” are designed and intended for use in
military/aerospace applications or environments. Buyer acknowledges and agrees that any military or aerospace use of TI components
which have not been so designated is solely at the Buyer's risk, and that Buyer is solely responsible for compliance with all legal and
regulatory requirements in connection with such use.
TI has specifically designated certain components as meeting ISO/TS16949 requirements, mainly for automotive use. In any case of use of
non-designated products, TI will not be responsible for any failure to meet ISO/TS16949.
Products
Applications
Audio
www.ti.com/audio
Automotive and Transportation
www.ti.com/automotive
Amplifiers
amplifier.ti.com
Communications and Telecom
www.ti.com/communications
Data Converters
dataconverter.ti.com
Computers and Peripherals
www.ti.com/computers
DLP® Products
www.dlp.com
Consumer Electronics
www.ti.com/consumer-apps
DSP
dsp.ti.com
Energy and Lighting
www.ti.com/energy
Clocks and Timers
www.ti.com/clocks
Industrial
www.ti.com/industrial
Interface
interface.ti.com
Medical
www.ti.com/medical
Logic
logic.ti.com
Security
www.ti.com/security
Power Mgmt
power.ti.com
Space, Avionics and Defense
www.ti.com/space-avionics-defense
Microcontrollers
microcontroller.ti.com
Video and Imaging
www.ti.com/video
RFID
www.ti-rfid.com
OMAP Applications Processors
www.ti.com/omap
TI E2E Community
e2e.ti.com
Wireless Connectivity
www.ti.com/wirelessconnectivity
Mailing Address: Texas Instruments, Post Office Box 655303, Dallas, Texas 75265
Copyright © 2016, Texas Instruments Incorporated