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LM3150
SNVS561G – SEPTEMBER 2008 – REVISED SEPTEMBER 2015
LM3150 Wide-VIN Synchronous Buck Controller
1 Features
3 Description
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The LM3150 SIMPLE SWITCHER® controller is an
easy-to-use and simplified step-down power
controller capable of providing up to 12 A of output
current in a typical application. Operating with an
input voltage range of 6 V to 42 V, the LM3150
controller features an adjustable output voltage down
to 0.6 V. The switching frequency is adjustable up to
1 MHz and the synchronous architecture provides for
highly efficient designs. The LM3150 controller
employs a constant on-time (COT) architecture with a
proprietary emulated ripple mode (ERM) control that
allows for the use of low ESR output capacitors,
which reduces overall solution size and output
voltage ripple. The COT regulation architecture allows
for fast transient response and requires no loop
compensation, which reduces external component
count and reduces design complexity.
1
PowerWise™ Step-Down Controller
6-V to 42-V Wide Input Voltage Range
Adjustable Output Voltage Down to 0.6 V
Programmable Switching Frequency up to 1 MHz
No Loop Compensation Required
Fully WEBENCH® Enabled
Low External Component Count
Constant On-Time (COT) Control
Ultra-Fast Transient Response
Stable With Low ESR Capacitors
Output Voltage PreBias Startup
Valley Current Limit
Programmable Soft-Start
Create a Custom Design Using the LM3150 with
the WEBENCH Power Designer
Fault protection features such as thermal shutdown,
undervoltage lockout, overvoltage protection, shortcircuit protection, current limit, and output voltage
prebias start-up allow for a reliable and robust
solution.
2 Applications
•
•
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Telecom
Networking Equipment
Routers
Security Surveillance
Power Modules
The LM3150 concept provides for an easy-to-use
complete design using a minimum number of external
components and TI’s WEBENCH online design tool.
WEBENCH provides design support for every step of
the design process and includes features such as
external component calculation with a new MOSFET
selector, electrical simulation, thermal simulation, and
Build-It boards for prototyping.
Device Information(1)
PART NUMBER
PACKAGE
LM3150
HTSSOP (14)
BODY SIZE (NOM)
5.00 mm × 4.40 mm
(1) For all available packages, see the orderable addendum at
the end of the datasheet.
4 Typical Application Schematic
VCC
EN
CVCC
VIN
VIN
VIN
M1
HG
RON
CIN
RON
BST
LM3150
CBST
L
SS
SW
CSS
VOUT
ILIM
FB
RFB2
COUT
RLIM
SGND
LG
M2
RFB1
PGND
1
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
LM3150
SNVS561G – SEPTEMBER 2008 – REVISED SEPTEMBER 2015
www.ti.com
Table of Contents
1
2
3
4
5
6
7
8
Features ..................................................................
Applications ...........................................................
Description .............................................................
Typical Application Schematic.............................
Revision History.....................................................
Pin Configuration and Functions .........................
Specifications.........................................................
1
1
1
1
2
3
4
7.1
7.2
7.3
7.4
7.5
7.6
4
4
4
4
5
7
Absolute Maximum Ratings ......................................
ESD Ratings..............................................................
Recommended Operating Ratings............................
Thermal Information ..................................................
Electrical Characteristics...........................................
Typical Characteristics ..............................................
Detailed Description .............................................. 9
8.1 Overview ................................................................... 9
8.2 Functional Block Diagram ....................................... 10
8.3 Feature Description................................................. 10
8.4 Device Functional Modes........................................ 13
9
Application and Implementation ........................ 14
9.1 Application Information............................................ 14
9.2 Typical Application .................................................. 14
10 Power Supply Recommendations ..................... 25
11 Layout................................................................... 25
11.1 Layout Guidelines ................................................. 25
11.2 Layout Example .................................................... 26
12 Device and Documentation Support ................. 27
12.1
12.2
12.3
12.4
12.5
Documentation Support .......................................
Community Resources..........................................
Trademarks ...........................................................
Electrostatic Discharge Caution ............................
Glossary ................................................................
27
27
27
27
28
13 Mechanical, Packaging, and Orderable
Information ........................................................... 28
5 Revision History
Changes from Revision F (December 2014) to Revision G
•
Changed graphic Inductor Current to Current Limit section. ............................................................................................... 11
Changes from Revision E (November 2012) to Revision F
•
2
Page
Page
Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation
section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and
Mechanical, Packaging, and Orderable Information section ................................................................................................. 4
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SNVS561G – SEPTEMBER 2008 – REVISED SEPTEMBER 2015
6 Pin Configuration and Functions
HTSSOP PWP
14 PINS
Top View
1
PGND
VCC
2
VIN
3
LG
BST
EN
4
EP
FB
5
HG
SW
SGND
6
SS
7
SGND
ILIM
RON
14
13
12
11
10
9
8
Pin Functions
PIN
NAME
NO.
I/O
DESCRIPTION
FUNCTION
VCC
1
O
Supply Voltage for FET
Drivers
Nominally regulated to 5.95 V. Connect a 1.0-µF to 4.7-µF decoupling
capacitor from this pin to ground.
VIN
2
I
Input Supply Voltage
Supply pin to the device. Nominal input range is 6 V to 42 V.
EN
3
I
Enable
To enable the IC, apply a logic high signal to this pin greater than 1.26-V
typical or leave floating. To disable the part, ground the EN pin.
FB
4
I
Feedback
Internally connected to the regulation, overvoltage, and short-circuit
comparators. The regulation setting is 0.6 V at this pin. Connect to feedback
resistor divider between the output and ground to set the output voltage.
5,9
—
Signal Ground
Ground for all internal bias and reference circuitry. Should be connected to
PGND at a single point.
SS
6
I
Soft-Start
An internal 7.7-µA current source charges an external capacitor to provide the
soft-start function.
RON
7
I
On-time Control
An external resistor from VIN to this pin sets the high-side switch on-time.
ILIM
8
I
Current Limit
Monitors current through the low-side switch and triggers current limit
operation if the inductor valley current exceeds a user defined value that is set
by RLIM and the Sense current, ILIM-TH, sourced out of this pin during operation.
SW
10
O
Switch Node
Switch pin of controller and high-gate driver lower supply rail. A boost
capacitor is also connected between this pin and BST pin
HG
11
O
High-Side Gate Drive
Gate drive signal to the high-side NMOS switch. The high-side gate driver
voltage is supplied by the differential voltage between the BST pin and SW
pin.
BST
12
I
Connection for Bootstrap
Capacitor
High-gate driver upper supply rail. Connect a 0.33 to 0.47-µF capacitor from
SW pin to this pin. An internal diode charges the capacitor during the high-side
switch off-time. Do not connect to an external supply rail.
LG
13
O
Low-Side Gate Drive
Gate drive signal to the low-side NMOS switch. The low-side gate driver
voltage is supplied by VCC.
PGND
14
G
Power Ground
Synchronous rectifier MOSFET source connection. Tie to power ground plane.
Should be tied to SGND at a single point.
EP
—
—
Exposed Pad
Exposed die attach pad should be connected directly to SGND. Also used to
help dissipate heat out of the IC.
SGND
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7 Specifications
7.1 Absolute Maximum Ratings
over operating free-air temperature range (unless otherwise noted)
(1) (2)
MIN
MAX
UNIT
–0.3
47
V
SW to GND
–3
47
V
BST to SW
–0.3
7
V
BST to GND
–0.3
52
V
VIN, RON to GND
All Other Inputs to GND
Tstg
(1)
(2)
Storage temperature
–0.3
7
V
–65
150
°C
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings
only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended
Operating Ratings. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability.
If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/ Distributors for availability and
specifications.
7.2 ESD Ratings
V(ESD)
(1)
Electrostatic discharge
Human body model (HBM), per ANSI/ESDA/JEDEC JS-001, all pins (1)
VALUE
UNIT
±2000
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
7.3 Recommended Operating Ratings
over operating free-air temperature range (unless otherwise noted)
MIN
VIN
Junction Temperature Range (TJ)
EN
NOM
MAX
UNIT
6
42
V
−40
125
°C
0
5
V
7.4 Thermal Information
LM3150
THERMAL METRIC (1)
PWP
UNIT
14 PINS
RθJA
Junction-to-ambient thermal resistance
42.5
RθJC(top)
Junction-to-case (top) thermal resistance
28.7
RθJB
Junction-to-board thermal resistance
24.2
ψJT
Junction-to-top characterization parameter
0.9
ψJB
Junction-to-board characterization parameter
23.9
RθJC(bot)
Junction-to-case (bottom) thermal resistance
4.4
(1)
4
°C/W
For more information about traditional and new thermal metrics, see the IC Package Thermal Metrics application report, SPRA953.
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7.5 Electrical Characteristics
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
TJ = 25°C
MIN
TYP
TJ = -40°C to 125°C
MAX
MIN
TYP
MAX
UNIT
START-UP; REGULATOR, VCC
CVCC = 1 µF, 0 mA to 40
mA
VCC
5.95
5.65
6.25
V
IVCC = 2 mA, VIN = 5.5 V
40
IVCC = 30 mA, VIN = 5.5 V
330
VCC Current Limit (1)
VCC = 0V
100
65
VCC Undervoltage Lockout
Threshold (UVLO)
VCC Increasing
5.1
4.75
VCC Decreasing
475
mV
3
µs
VIN - VCC
VIN - VCC Dropout Voltage
IVCCL
VCCUVLO
VCCUVLO-HYS VCC UVLO Hysteresis
mV
mA
5.40
V
tCC-UVLO-D
VCC UVLO Filter Delay
IIN
Input Operating Current
No Switching, VFB = 1 V
3.5
5
mA
IIN-SD
Input Operating Current,
Device Shutdown
VEN = 0 V
32
55
µA
IQ-BST
Boost Pin Leakage
VBST – VSW = 6 V
2
nA
RDS-HG-Pull-Up
HG Drive Pullip OnResistance
IHG Source = 200 mA
5
Ω
RDS-HG-Pull-
HG Drive Pulldown OnResistance
IHG Sink = 200 mA
3.4
Ω
RDS-LG-Pull-Up
LG Drive Pullup OnResistance
ILG Source = 200 mA
3.4
Ω
RDS-LG-Pull-
LG Drive Pulldown OnResistance
ILG Sink = 200 mA
2
Ω
ISS
SS Pin Source Current
VSS = 0 V
7.7
ISS-DIS
SS Pin Discharge Current
Current Limit
200
ILIM-TH
Current Limit Sense Pin
Source Current
GATE DRIVE
Down
Down
SOFT-START
75
85
5.9
9.5
µA
µA
95
µA
ON/OFF TIMER
tON
ON Timer Pulse Width
tON-MIN
ON Timer Minimum Pulse
Width
tOFF
OFF Timer Minimum Pulse
Width
VIN = 10V, RON = 100 kΩ,
VFB = 0.6V
1.02
VIN = 18V, RON = 100 kΩ,
VFB = 0.6 V
0.62
VIN = 42 V, RON = 100 kΩ,
VFB = 0.6 V
0.36
See (2)
200
µs
ns
370
525
ns
1.26
V
ENABLE INPUT
VEN
EN Pin Input Threshold Trip
Point
VEN Rising
1.20
VEN-HYS
EN Pin Threshold Hysteresis
VEN Falling
120
1.14
mV
REGULATION AND OVERVOLTAGE COMPARATOR
VFB
In-Regulation Feedback
Voltage
VFB-OV
IFB
(1)
(2)
VSS > 0.6 V
0.600
0.588
0.612
V
Feedback Overvoltage
Threshold
0.720
0.690
0.748
V
Feedback Bias Current
20
nA
VCC provides self bias for the internal gate drive and control circuits. Device thermal limitations limit external loading.
See Detailed Description section for minimum on-time when using MOSFETs connected to gate drivers.
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Electrical Characteristics (continued)
over operating free-air temperature range (unless otherwise noted)
PARAMETER
TEST CONDITIONS
TJ = 25°C
MIN
TYP
TJ = -40°C to 125°C
MAX
MIN
TYP
MAX
UNIT
BOOST DIODE
Vf
Forward Voltage
IBST = 2 mA
IBST = 30 mA
0.7
1
V
THERMAL CHARACTERISTICS
TSD
6
Thermal Shutdown
Rising
165
°C
Thermal Shutdown Hysteresis Falling
15
°C
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7.6 Typical Characteristics
Figure 1. 500-kHz Full Load Transient
Figure 2. 500-kHz Partial Load Transient
Figure 3. Boost Diode Forward Voltage vs Temperature
Figure 4. ILIM-TH vs Temperature
Figure 5. Quiescent Current vs Temperature
Figure 6. Soft-Start Current vs Temperature
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Typical Characteristics (continued)
8
Figure 7. tON vs Temperature
Figure 8. tON vs Temperature
Figure 9. tON vs Temperature
Figure 10. VCC Current Limit vs Temperature
Figure 11. VCC Dropout vs Temperature
Figure 12. VCC vs Temperature
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8 Detailed Description
8.1 Overview
The LM3150 synchronous step-down controller uses a COT architecture which is a derivative of the hysteretic
control scheme. COT relies on a fixed switch on-time to regulate the output. The on-time of the high-side switch
can be set manually by adjusting the size of an external resistor (RON). To maintain a relatively constant
switching frequency as VIN varies, the LM3150 controller automatically adjusts the on-time inversely with the
input voltage. Assuming an ideal system and VIN is much greater than 1 V, the following approximations can be
made:
The on-time, tON:
K x RON
tON =
VIN
where
•
constant K = 100 pC
(1)
The RON resistance value can be calculated as follows:
VOUT
RON =
K x fS
where
•
fs is the desired switching frequency
(2)
Control is based on a comparator and the on-timer, with the output voltage feedback (FB) compared with an
internal reference of 0.6 V. If the FB level is below the reference, the high-side switch is turned on for a fixed
time, tON, which is determined by the input voltage and the resistor RON. Following this on-time, the switch
remains off for a minimum off-time, tOFF, as specified in the Electrical Characteristics table or until the FB pin
voltage is below the reference, then the switch turns on again for another on-time period. The switching will
continue in this fashion to maintain regulation. During continuous conduction mode (CCM), the switching
frequency ideally depends on duty-cycle and on-time only. In a practical application however, there is a small
delay in the time that the HG goes low and the SW node goes low that also affects the switching frequency that
is accounted for in the typical application curves. The duty-cycle and frequency can be approximated as:
tON
VOUT
= tON x fS |
D=
tON + tOFF
VIN
(3)
fS =
VOUT
K x RON
(4)
Typical COT hysteretic controllers need a significant amount of output capacitor ESR to maintain a minimum
amount of ripple at the FB pin in order to switch properly and maintain efficient regulation. The LM3150
controller, however, uses a proprietary Emulated Ripple Mode control scheme (ERM) that allows the use of low
ESR output capacitors. Not only does this reduce the need for high output capacitor ESR, but also significantly
reduces the amount of output voltage ripple seen in a typical hysteretic control scheme. The output ripple voltage
can become so low that it is comparable to voltage-mode and current-mode control schemes.
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8.2 Functional Block Diagram
EN
EN
LM3150
6V
VIN
AVDD
1 M5
6V LDO
VIN
1.20V
0.72V
0.6V
Vbias
VDD
VCC
UVLO
CIN
GND
VCC
THERMAL
SHUTDOWN
CVCC
1.20V
RON
toff
OFF TIMER
START
COMPLETE
ON TIMER
RON
Ron START
COMPLETE
BST
CBST
VDD
HG
ISS
SS
LOGIC
DrvH
LEVEL
SHIFT
DrvL
CSS
REGULATION
COMPARATOR
FB
Vref = 0.6V
PMOS
input
Zero
Current
Detect
0.72V
VFB-OV and
SHORT
CIRCUIT
PROTECTION
SGND
M1
DRIVER
L
VOUT
SW
VCC
DRIVER
LG
PGND
M2
RFB2
COUT
VDD
ILIM-TH
ILIM
0.36V
VIN
CURRENT LIMIT
COMPARATOR
RLIM
RFB1
GND
PGND
ERM CONTROL
8.3 Feature Description
8.3.1 Programming the Output Voltage
The output voltage is set by two external resistors (RFB1,RFB2). The regulated output voltage is calculated as
follows:
(RFB1 + RFB2)
VOUT = VFB x
RFB1
where
•
•
RFB2 is the top resistor connected between VOUT and FB
RFB1 is the bottom resistor connected between FB and GND
(5)
8.3.2 Regulation Comparator
The feedback voltage at FB is compared to the internal reference voltage of 0.6 V. In normal operation (the
output voltage is regulated), an on-time period is initiated when the voltage at FB falls below 0.6 V. The high-side
switch stays on for the on-time, causing the FB voltage to rise above 0.6 V. After the on-time period, the highside switch stays off until the FB voltage falls below 0.6 V.
8.3.3 Overvoltage Comparator
The overvoltage comparator is provided to protect the output from overvoltage conditions due to sudden input
line voltage changes or output loading changes. The overvoltage comparator continuously monitors the voltage
at the FB pin and compares it to a 0.72 V internal reference. If the voltage at FB rises above 0.72 V, the on-time
pulse is immediately terminated. This condition can occur if the input or the output load changes suddenly. Once
the overvoltage protection is activated, the HG and LG signals remain off until the voltage at FB pin falls below
0.72 V.
8.3.4 Current Limit
Current limit detection occurs during the off-time by monitoring the current through the low-side switch using an
external resistor, RLIM. If during the off-time the current in the low-side switch exceeds the user defined current
limit value, the next on-time cycle is immediately terminated. Current sensing is achieved by comparing the
voltage across the low side FET with the voltage across the current limit set resistor RLIM. If the voltage across
RLIM and the voltage across the low-side FET are equal then the current limit comparator will terminate the next
on-time cycle.
10
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Feature Description (continued)
The RLIM value can be approximated as follows:
'I
ICL = IOCL - L
2
ICL x RDS(ON)max
RLIM =
ILIM-TH
(6)
where
•
•
•
IOCL is the user-defined average output current limit value
RDS(ON)max is the resistance value of the low-side FET at the expected maximum FET junction temperature
ILIM-TH is an internal current supply of 85 µA typical
(7)
Figure 13 illustrates the inductor current waveform. During normal operation, the output current ripple is dictated
by the switching of the FETs. The current through the low-side switch, Ivalley, is sampled at the end of each
switching cycle and compared to the current limit, ICL, current. The valley current can be calculated as follows:
'I
Ivalley = IOUT - L
2
where
•
•
IOUT is the average output current
ΔIL is the peak-to-peak inductor ripple current
(8)
If an overload condition occurs, the current through the low-side switch will increase which will cause the current
limit comparator to trigger the logic to skip the next on-time cycle. The IC will then try to recover by checking the
valley current during each off-time. If the valley current is greater than or equal to ICL, then the IC will keep the
low-side FET on and allow the inductor current to further decay.
Throughout the whole process, regardless of the load current, the on-time of the controller will stay constant and
thereby the positive ripple current slope will remain constant. During each on-time the current ramps-up an
amount equal to:
(VIN - VOUT) x tON
'IL =
L
(9)
The valley current limit feature prevents current runaway conditions due to propagation delays or inductor
saturation because the inductor current is forced to decay following any overload conditions.
Current sensing is achieved by either a low value sense resistor in series with the low-side FET or by utilizing the
RDS(ON) of the low-side FET. The RDS(ON) sensing method is the preferred choice for a more simplified design and
lower costs. The RDS(ON) value of a FET has a positive temperature coefficient and will increase in value as the
temperature of the FET increases. The LM3150 controller will maintain a more stable current limit that is closer to
the original value that was set by the user, by positively adjusting the ILIM-TH value as the IC temperature
increases. This does not provide an exact temperature compensation but allows for a more tightly controlled
current limit when compared to traditional RDS(ON) sensing methods when the RDS(ON) value can change typically
140% from room to maximum temperature and cause other components to be over-designed. The temperature
compensated ILIM-TH is shown below where TJ is the die temperature of the LM3150 controller in Celsius:
ILIM-TH(TJ) = ILIM-TH x [1 + 3.3 x 10-3 x (TJ - 27)]
(10)
To calculate the RLIM value with temperature compensation, substitute Equation 10 into ILIM-TH in Equation 7.
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Feature Description (continued)
IPK
'I
IOCL
Inductor Current
ICL
IOUT
Normal Operation
Load Current
Increases
Current Limited
Figure 13. Inductor Current - Current Limit Operation
8.3.5 Short-Circuit Protection
The LM3150 controller will sense a short-circuit on the output by monitoring the output voltage. When the
feedback voltage has fallen below 60% of the reference voltage, Vref x 0.6 (≈ 0.36 V), short-circuit mode of
operation will start. During short-circuit operation, the SS pin is discharged and the output voltage will fall to 0 V.
The SS pin voltage, VSS, is then ramped back up at the rate determined by the SS capacitor and ISS until VSS
reaches 0.7 V. During this re-ramp phase, if the short-circuit fault is still present the output current will be equal
to the set current limit. Once the soft-start voltage reaches 0.7 V, the output voltage is sensed again and if the
VFB is still below Vref x 0.6 then the SS pin is discharged again and the cycle repeats until the short-circuit fault is
removed.
8.3.6 Soft-Start
The soft-start (SS) feature allows the regulator to gradually reach a steady-state operating point, which reduces
start-up stresses and current surges. At turnon, while VCC is below the undervoltage threshold, the SS pin is
internally grounded and VOUT is held at 0 V. The SS capacitor is used to slowly ramp VFB from 0 V to 0.6 V. By
changing the capacitor value, the duration of start-up can be changed accordingly. The start-up time can be
calculated using the following equation:
Vref x CSS
tSS =
ISS
where
•
•
•
tSS is measured in seconds
Vref = 0.6 V
ISS is the soft-start pin source current, which is typically 7.7 µA (refer to Electrical Characteristics)
(11)
An internal switch grounds the SS pin if VCC is below the undervoltage lockout threshold, if a thermal shutdown
occurs, or if the EN pin is grounded. By using an externally controlled switch, the output voltage can be shut off
by grounding the SS pin.
During startup the LM3150 controller will operate in diode emulation mode, where the low-side gate LG will turn
off and remain off when the inductor current falls to zero. Diode emulation mode will allow start-up into a prebiased output voltage. When soft-start is greater than 0.7 V, the LM3150 controller will remain in continuous
conduction mode. During diode emulation mode at current limit the low-gate will remain off when the inductor
current is off.
The soft-start time should be greater than the input voltage rise time and also satisfy the following equality to
maintain a smooth transition of the output voltage to the programmed regulation voltage during start-up.
12
tSS ≥ (VOUT x COUT) / (IOCL - IOUT)
(12)
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Feature Description (continued)
8.3.7 Thermal Protection
The LM3150 controller should be operated such that the junction temperature does not exceed the maximum
operating junction temperature. An internal thermal shutdown circuit, which activates at 165°C (typical), takes the
controller to a low-power reset state by disabling the buck switch and the on-timer, and grounding the SS pin.
This feature helps prevent catastrophic failures from accidental device overheating. When the junction
temperature falls back below 150°C the SS pin is released and device operation resumes.
8.4 Device Functional Modes
The EN pin can be activated by either leaving the pin floating due to an internal pullup resistor to VIN or by
applying a logic high signal to the EN pin of 1.26 V or greater. The LM3150 controller can be remotely shut down
by taking the EN pin below 1.02 V. Low quiescent shutdown is achieved when VEN is less than 0.4 V. During
low quiescent shutdown the internal bias circuitry is turned off.
The LM3150 controller has certain fault conditions that can trigger shutdown, such as short circuit, undervoltage
lockout, or thermal shutdown. During shutdown, the soft-start capacitor is discharged. Once the fault condition is
removed, the soft-start capacitor begins charging, allowing the part to start-up in a controlled fashion. In
conditions where there may be an open drain connection to the EN pin, it may be necessary to add a 1-nF
bypass capacitor to this pin. This will help decouple noise from the EN pin and prevent false disabling.
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9 Application and Implementation
NOTE
Information in the following applications sections is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers are
responsible for determining suitability of components for their purposes. Customers should
validate and test their design implementation to confirm system functionality.
9.1 Application Information
The LM3150 controller employs a COT architecture with ERM (emulated ripple mode) control. This allows for fast
transient response, reduction in output voltage ripple, and low external component count. A typical application of
this part is described in the following section.
9.2 Typical Application
VIN
VCC
EN
CVCC
CEN
VIN
VIN
M1
HG
RON
CBYP
RON
CIN
BST
LM3150
CBST
L
SS
SW
CSS
VOUT
COUT
ILIM
FB
RLIM
SGND
LG
CFF
M2
RFB2
PGND
RFB1
Figure 14. Design Example Schematic
9.2.1 Design Requirements
To properly size the components for the application, the designer needs the following parameters: Input voltage
range, output voltage, output current range and required switching frequency. To summarize briefly, these four
main parameters will affect the choices of component available to achieve a proper system behavior.
For the power supply, the input impedance of the supply rail should be low enough that the input current
transient does not cause drop below the UVLO value. To maintain a relatively constant switching frequency as
the input voltage varies, the LM3150 controller automatically adjusts the on-time inversely with the input voltage.
The available frequency range for a given input voltage range, is determined by the duty-cycle, D = VOUT/VIN, and
the minimum tON and tOFF times. The feedback resistor values can be calculated based on the value of required
output and feedback voltage. Regarding the output capacitor, its voltage rating must be greater than or equal to
the output voltage. Similarly, the voltage rating for the input capacitor must be greater than the input voltage to
be used in the application. Also, a feed-forward capacitor may be required for improved stability, based on the
application.
The following sections describe in detail the design requirements for a typical LM3150 application.
14
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Typical Application (continued)
9.2.2 Detailed Design Procedure
9.2.2.1 Custom Design with WEBENCH Tools
Click here to create a custom design using the LM3150 device with the WEBENCH® Power Designer.
1. Start by entering your VIN, VOUT and IOUT requirements.
2. Optimize your design for key parameters like efficiency, footprint and cost using the optimizer dial and
compare this design with other possible solutions from Texas Instruments.
3. WEBENCH Power Designer provides you with a customized schematic along with a list of materials with real
time pricing and component availability.
4. In most cases, you will also be able to:
– Run electrical simulations to see important waveforms and circuit performance,
– Run thermal simulations to understand the thermal performance of your board,
– Export your customized schematic and layout into popular CAD formats,
– Print PDF reports for the design, and share your design with colleagues.
5. Get more information about WEBENCH tools at www.ti.com/webench.
9.2.2.2 LM3150 Design Procedure
To properly size the components for the application, the designer needs the following parameters: Input voltage
range, output voltage, output current range and required switching frequency. These four main parameters will
affect the choices of component available to achieve a proper system behavior.
Table 1. Bill of Materials
DESIGNATOR
VALUE
PARAMETERS
MANUFACTURER
PART NUMBER
CBST
0.47 µF
Ceramic, X7R, 16 V, 10%
TDK
C2012X7R1C474K
CBYP
0.1 µF
Ceramic, X7R, 50 V, 10%
TDK
C2012X7R1H104K
CEN
1000 pF
Ceramic, X7R, 50 V, 10%
TDK
C1608X7R1H102K
CFF
270 pF
Ceramic, C0G, 50 V, 5%
Vishay-Bccomponents
VJ0805A271JXACW1BC
CIN1, CIN2
10 µF
Ceramic, X5R, 35 V, 20%
Taiyo Yuden
GMK325BJ106KN-T
COUT1, COUT2
150 µF
Polymer Aluminum, 6.3 V, 20%
Panasonic
EEF-UE0J151R
CSS
0.068 µF
Ceramic, 0805, 25 V, 10%
Vishay
VJ0805Y683KXXA
CVCC
4.7 µF
Ceramic, X7R, 16 V, 10%
Murata
GRM21BR71C475KA73L
L1
1.65 µH
Shielded Drum Core, 2.53 mΩ
Coilcraft
HA3778–AL
M1, M2
30 V
8 nC, RDS(ON) @4.5 V=10 mΩ
Renesas
RJK0305DPB
RFB1
4.99 kΩ
1%, 0.125 W
Vishay-Dale
CRCW08054k99FKEA
RFB2
22.6 kΩ
1%, 0.125 W
Vishay-Dale
CRCW080522k6FKEA
RLIM
1.91 kΩ
1%, 0.125 W
Vishay-Dale
CRCW08051K91FKEA
RON
56.2 kΩ
1%, 0.125 W
Vishay-Dale
CRCW080556K2FKEA
U1
LM3150
Texas Instruments
LM3150
1. Define Power Supply Operating Conditions
(a) VOUT = 3.3 V
(b) VIN-MIN = 6 V, VIN-TYP = 12 V, VIN-MAX = 24 V
(c) Typical Load Current = 12 A, Max Load Current = 15 A
(d) Soft-Start time tSS = 5 ms
2. Set Output Voltage with Feedback Resistors
VOUT
RFB2 = RFB1
-1
VFB
(13)
3.3V
-1
RFB2 = 4.99 k:
0.6V
(14)
(15)
RFB2 = 22.455 kΩ
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RFB2 = 22.6 kΩ, nearest 1% standard value.
3. Determine RON and fS
Dmin = VOUT/VIN-MAX
Dmin = 3.3V/24V = 0.137
Dmax = 3.3V / 6V = 0.55
fsmax = 0.137/ 200 ns = 687 kHz
Dmax = VOUT/VIN-MIN
tOFF = (1-0.55)/687 kHz = 654 ns
(16)
(17)
(18)
(19)
(20)
(21)
tOFF should meet the following criteria:
tOFF > tOFF-MIN + 200 ns
tOFF > 725 ns
(22)
(23)
At the maximum switching frequency of 687 kHz, which is limited by the minimum on-time, the off-time of 654
ns is less than 725 ns. Therefore the switching frequency should be reduced and meet the following criteria:
fs < (1 - D)/725 ns
fS < (1 - 0.55)/725 ns = 620 kHz
(24)
(25)
A switching frequency is arbitrarily chosen at 500 kHz which should allow for reasonable size components
and satisfies the requirements above.
fS = 500 kHz
Using fS = 500 kHz RON can be calculated as follows:
RON = [(VOUT x VIN) - VOUT] / (VIN x K x fS) + ROND
ROND = - [(VIN - 1) x (VIN x 16.5 + 100)] - 1000
ROND = - [(12 - 1) x (12 x 16.5 + 100)] -1000
ROND = -4.3 kΩ
RON = [(3.3 x 12) - 3.3] / (12 x 100 pC x 500 kHz) - 4.3 kΩ
RON = 56.2 kΩ
(26)
(27)
(28)
(29)
(30)
(31)
Next, check the desired minimum input voltage for RON using Figure 15. This design will meet the desired
minimum input voltage of 6 V.
4. Determine Inductor Required
(a) ET = (24-3.3) x (3.3/24) x (1000/500) = 5.7 V µs
(b) From the inductor nomograph a 12-A load and 5.7 V µs calculation corresponds to a L44 type of
inductor.
(c) Using the inductor designator L44 in Table 2 the Coilcraft HA3778–AL 1.65-µH inductor is chosen.
5. Determine Output Capacitance
The voltage rating on the output capacitor should be greater than or equal to the output voltage. As a rule of
thumb most capacitor manufacturers suggests not to exceed 90% of the capacitor rated voltage. In the case
of multilayer ceramics the capacitance will tend to decrease dramatically as the applied voltage is increased
towards the capacitor rated voltage. The capacitance can decrease by as much as 50% when the applied
voltage is only 30% of the rated voltage. The chosen capacitor should also be able to handle the rms current
which is equal to:
r
Irmsco = IOUT x
12
(32)
For this design the chosen ripple current ratio, r = 0.3, represents the ratio of inductor peak-to-peak current
to load current IOUT. A good starting point for ripple ratio is 0.3 but it is acceptable to choose r between 0.25
to 0.5. The nomographs in this datasheet all use 0.3 as the ripple current ratio.
0.3
Irmsco = 12 x
12
(33)
Irmsco = 1A
tON = (3.3V/12V)/500 kHz = 550 ns
(34)
(35)
Minimum output capacitance is:
16
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COmin = 70 / (fs2 x L)
COmin = 70 / (500 kHz2 x 1.65 µH) = 169 µF
(36)
(37)
The maximum ESR allowed to prevent overvoltage protection during normal operation is:
ESRmax = (80 mV x L x Af) / ET
Af = VOUT / 0.6 without a feed-forward capacitor
Af = 1 with a feed-forward capacitor
(38)
(39)
(40)
For this design a feed-forward capacitor will be used to help minimize output ripple.
ESRmax = (80 mV x 1.65 µH x 1) / 5.7 V µs
ESRmax = 23 mΩ
(41)
(42)
The minimum ESR must meet both of the following criteria:
ESRmin ≥ (15 mV x L x Af) / ET
ESRmin ≥ [ ET / (VIN - VOUT) ] x (Af / CO)
ESRmin ≥ (15 mV x 1.65 µH x 1) / 5.7 V µs = 4.3 mΩ
ESRmin ≥ [5.7 V µs / (12 - 3.3) ] x (1 / 169 µF) = 3.9 mΩ
(43)
(44)
(45)
(46)
Based on the above criteria two 150-µF polymer aluminum capacitors with a ESR = 12 mΩ each for a
effective ESR in parallel of 6 mΩ was chosen from Panasonic. The part number is EEF-UE0J101P.
6. Determine Use of Feed-Forward Capacitor
From Step 5 the capacitor chosen in ESR is small enough that we should use a feed-forward capacitor. This
is calculated from:
VOUT
RFB1 + RFB2
x
Cff =
VIN-MIN x fs
RFB1 x RFB2
Cff =
3.3V
4.99 k: + 22.6 k:
x
= 269 pF
6V x 500 kHz 4.99 k: x 22.6 k:
(47)
Let Cff = 270 pF, which is the closest next standard value.
7. MOSFET and RLIM Selection
The LM3150 controller is designed to drive N-channel MOSFETs. For a maximum input voltage of 24 V we
should choose N-channel MOSFETs with a maximum drain-source voltage, VDS, greater than 1.2 x 24 V =
28.8 V. FETs with maximum VDS of 30 V will be the first option. The combined total gate charge Qgtotal of the
high-side and low-side FET should satisfy the following:
Qgtotal ≤ IVCCL / fs
Qgtotal ≤ 65 mA / 500 kHz
Qgtotal ≤ 130 nC
(48)
(49)
(50)
Where IVCCL is the minimum current limit of VCC, over the temperature range, specified in the Electrical
Characteristics table. The MOSFET gate charge Qg is gathered from reading the VGS vs Qg curve of the
MOSFET datasheet at the VGS = 5 V for the high-side, M1, MOSFET and VGS = 6 V for the low-side, M2,
MOSFET.
The Renesas MOSFET RJK0305DPB has a gate charge of 10 nC at VGS = 5 V, and 12 nC at VGS = 6 V.
This combined gate charge for a high-side, M1, and low-side, M2, MOSFET 12 nC + 10 nC = 22 nC is less
than 130 nC calculated Qgtotal.
The calculated MOSFET power dissipation must be less than the max allowed power dissipation, Pdmax, as
specified in the MOSFET data sheet. An approximate calculation of the FET power dissipated Pd, of the
high-side and low-side FET is given by:
High-Side MOSFET
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2
Pcond = Iout x RDS(ON) x D
Psw =
8.5
6.8
1
+
x Vin x Iout x Qgd x fs x
Vcc - Vth Vth
2
Pdh = Pcond + Psw
2
Pcond = 12 x 0.01 x 0.275 = 0.396W
Psw =
8.5
6.8
1 x 12 x 12 x 1.5 nC x 500 kHz x
+
= 0.278W
6 ± 2.5 2.5
2
Pdh = 0.396 + 0.278 = 0.674W
(51)
The max power dissipation of the RJK0305DPB is rated as 45 W for a junction temperature that is 125°C
higher than the case temperature and a thermal resistance from the FET junction to case, θJC, of 2.78°C/W.
When the FET is mounted onto the PCB, the PCB will have some additional thermal resistance such that the
total system thermal resistance of the FET package and the PCB, θJA, is typically in the range of 30°C/W for
this type of FET package. The max power dissipation, Pdmax, with the FET mounted onto a PCB with a
125°C junction temperature rise above ambient temperature and θJA = 30°C/W, can be estimated by:
Pdmax = 125°C / 30°C/W = 4.1 W
(52)
The system calculated Pdh of 0.674 W is much less than the FET Pdmax of 4.1 W and therefore the
RJK0305DPB max allowable power dissipation criteria is met.
Low-Side MOSFET
Primary loss is conduction loss given by:
Pdl = Iout2 x RDS(ON) x (1-D) = 122 x 0.01 x (1-0.275) = 1 W
(53)
Pdl is also less than the Pdmax specified on the RJK0305DPB MOSFET data sheet.
However, it is not always necessary to use the same MOSFET for both the high-side and low-side. For most
applications it is necessary to choose the high-side MOSFET with the lowest gate charge and the low-side
MOSFET is chosen for the lowest allowed RDS(ON). The plateau voltage of the FET VGS vs Qg curve must be
less than VCC - 750 mV.
The current limit resistor, RLIM, is calculated by estimating the RDS(ON) of the low-side FET at the maximum
junction temperature of 100°C. By choosing to go into current limit when the average output load current is
20% higher than the output load current of 12A while the inductor ripple current ratio is 1/3 of the load current
will make ICL= 10.4 A. Then the following calculation of RLIM is:
RLIM = (10.4 x 0.014) / (75 x 10-6) = 1.9 kΩ
(54)
Let RLIM = 1.91 kΩ which is the next standard value.
8. Calculate Input Capacitance
The input capacitor should be chosen so that the voltage rating is greater than the maximum input voltage
which for this example is 24 V. Similar to the output capacitor, the voltage rating needed will depend on the
type of capacitor chosen. The input capacitor should also be able to handle the input rms current, which is a
maximum of approximately 0.5 x IOUT. For this example the rms input current is approximately 0.5 x 12 A = 6
A.
The minimum capacitance with a maximum 5% input ripple ΔVIN-MAX = (0.05 x 12) = 0.6 V:
CIN = [12 x 0.275 x (1-0.275)] / [500 kHz x 0.6] = 8 µF
(55)
To handle the large input rms current 2 ceramic capacitors are chosen at 10 µF each with a voltage rating of
50 V and case size of 1210. Each ceramic capacitor is capable of handling 3 A of rms current. A aluminum
electrolytic of 5 times the combined input capacitance, 5 x 20 µF = 100 µF, is chosen to provide input voltage
filter damping because of the low ESR ceramic input capacitors.
CBYP = 0.1µF ceramic with a voltage rating greater than maximum VIN
9. Calculate Soft-Start Capacitor
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The soft start-time should be greater than the input voltage rise time and also satisfy the following equality to
maintain a smooth transition of the output voltage to the programmed regulation voltage during startup. The
desired soft-start time, tss, of 5 ms also must satisfy the equality in Equation 12, by using the chosen
component values through the previous steps as shown below:
5 ms > (3.3V x 300 µF) / (1.2 x 12A - 12A)
5 ms > 0.412 ms
(56)
(57)
Because the desired soft-start time satisfies the equality in Equation 12, the soft start capacitor is calculated
as:
CSS = (7.7 µA x 5 ms) / 0.6V = 0.064 µF
(58)
Let CSS = 0.068 µF, which is the next closest standard value. This should be a ceramic cap with a voltage
rating greater than 10 V.
10. CVCC, CEN, and CBST
CVCC = 4.7-µF ceramic with a voltage rating greater than 10 V
CEN = 1000-pF ceramic with a voltage rating greater than 10 V
CBST = 0.47-µF ceramic with a voltage rating greater than 10 V
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9.2.2.3 Design Guide
The design guide provides the equations required to design with the LM3150 controller. WEBENCH design tool
can be used with or in place of this section for a more complete and simplified design process.
1. Define Power Supply Operating Conditions
(a) Required Output Voltage
(b) Maximum and Minimum DC Input Voltage
(c) Maximum Expected Load Current during Normal Operation
(d) Soft-Start Time
2. Set Output Voltage With Feedback Resistors
(RFB1 + RFB2)
VOUT = VFB x
RFB1
where
•
•
RFB1 is the bottom resistor
RFB2 is the top resistor
(59)
3. Determine RON and fs
The available frequency range for a given input voltage range, is determined by the duty-cycle, D = VOUT/VIN,
and the minimum tON and tOFF times as specified in the Electrical Characteristics table. The maximum
frequency is thus, fsmax = Dmin/tON-MIN. Where Dmin=VOUT/VIN-MAX, is the minimum duty-cycle. The off-time will
need to be less than the minimum off-time tOFF as specified in the Electrical Characteristics table plus any
turnoff and turnon delays of the MOSFETs which can easily add another 200 ns. The minimum off-time will
occur at maximum duty cycle Dmax and will determine if the frequency chosen will allow for the minimum
desired input voltage. The requirement for minimum off-time is tOFF= (1–Dmax)/fs ≥ (tOFF-MIN + 200 ns). If tOFF
does not meet this requirement it will be necessary to choose a smaller switching frequency fS.
Choose RON so that the switching frequency at your typical input voltage matches your fS chosen above
using the following formula:
RON = [(VOUT x VIN) - VOUT] / (VIN x K x fS) + ROND
ROND = - [(VIN - 1) x (VIN x 16.5 + 100)] - 1000
(60)
(61)
Use Figure 15 to determine if the calculated RON will allow for the minimum desired input voltage. If the
minimum desired input voltage is not met, recalculate RON for a lower switching frequency.
Figure 15. Minimum VIN vs. VOUT
IOUT = 10 A
4. Determine Inductor Required Using Figure 16
To use the nomograph in Figure 16, calculate the inductor volt-microsecond constant ET from the following
formula:
VOUT
x 1000 (V x Ps)
ET = (Vinmax ± VOUT) x
Vinmax
fS
where
20
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•
fs is in kHz units
(62)
The intersection of the Load Current and the Volt-microseconds lines on the chart below will determine which
inductors are capable for use in the design. Figure 16 shows a sample of parts that can be used. The offline
calculator tools and WEBENCH will fully calculate the requirements for the components needed for the
design.
47 P
100
90
80
70
60
50
L01
L13
L02
L14
H
L37
L25
L03
40
E À T (V À Ps)
33 P
H
L04
L16
20
L05
L17
L06
L18
L22
2
L11
L23
L12
L24
5
H
4.7 P
L29
L42
H
3.3 P
L43
2.2 P
L44
1.5 P
L32
L45
1.0 P
L33
L46
P
0.68
L34
L47
PH
0.47
L35
6
H
6.8 P
L48
H
H
H
H
P
0.33
H
L36
1
4
L41
L21
L10
H
L28
L31
3
10 P
L40
L20
L09
4
H
L27
L19
L08
15 P
L39
L30
L07
H
L26
L15
30
10
9
8
7
6
5
L38
22 P
7
8
9
10
12
MAXIMUM LOAD CURRENT (A)
Figure 16. Inductor Nomograph
Table 2. Inductor Selection Table
INDUCTOR
DESIGNATOR
INDUCTANCE (µH)
CURRENT (A)
PART NAME
VENDOR
L01
47
7-9
L02
33
L03
22
7-9
SER2817H-333KL
COILCRAFT
7-9
SER2814H-223KL
L04
COILCRAFT
15
7-9
7447709150
WURTH
L05
10
7-9
RLF12560T-100M7R5
TDK
L06
6.8
7-9
B82477-G4682-M
EPCOS
L07
4.7
7-9
B82477-G4472-M
EPCOS
L08
3.3
7-9
DR1050-3R3-R
COOPER
L09
2.2
7-9
MSS1048-222
COILCRAFT
L10
1.5
7-9
SRU1048-1R5Y
BOURNS
L11
1
7-9
DO3316P-102
COILCRAFT
L12
0.68
7-9
DO3316H-681
COILCRAFT
L13
33
9-12
L14
22
9-12
SER2918H-223
COILCRAFT
L15
15
9-12
SER2814H-153KL
COILCRAFT
L16
10
9-12
7447709100
WURTH
L17
6.8
9-12
SPT50H-652
COILCRAFT
L18
4.7
9-12
SER1360-472
COILCRAFT
L19
3.3
9-12
MSS1260-332
COILCRAFT
L20
2.2
9-12
DR1050-2R2-R
COOPER
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Table 2. Inductor Selection Table (continued)
INDUCTOR
DESIGNATOR
INDUCTANCE (µH)
CURRENT (A)
PART NAME
VENDOR
L21
1.5
9-12
DR1050-1R5-R
COOPER
L22
1
9-12
DO3316H-102
COILCRAFT
L23
0.68
9-12
L24
0.47
9-12
L25
22
12-15
SER2817H-223KL
COILCRAFT
L26
15
12-15
L27
10
12-15
SER2814L-103KL
COILCRAFT
L28
6.8
12-15
7447709006
WURTH
L29
4.7
12-15
7447709004
WURTH
L30
3.3
12-15
L31
2.2
12-15
L32
1.5
12-15
MLC1245-152
COILCRAFT
L33
1
12-15
L34
0.68
12-15
DO3316H-681
COILCRAFT
L35
0.47
12-15
L36
0.33
12-15
DR73-R33-R
COOPER
L37
22
15-
L38
15
15-
SER2817H-153KL
COILCRAFT
L39
10
15-
SER2814H-103KL
COILCRAFT
L40
6.8
15-
L41
4.7
15-
SER2013-472ML
COILCRAFT
L42
3.3
15-
SER2013-362L
COILCRAFT
L43
2.2
15-
L44
1.5
15-
HA3778–AL
COILCRAFT
L45
1
15-
B82477-G4102-M
EPCOS
L46
0.68
15-
L47
0.47
15-
L48
0.33
15-
5. Determine Output Capacitance
Typical hysteretic COT converters similar to the LM3150 controller require a certain amount of ripple that is
generated across the ESR of the output capacitor and fed back to the error comparator. Emulated Ripple
Mode control built into the LM3150 controller will recreate a similar ripple signal and thus the requirement for
output capacitor ESR will decrease compared to a typical Hysteretic COT converter. The emulated ripple is
generated by sensing the voltage signal across the low-side FET and is then compared to the FB voltage at
the error comparator input to determine when to initiate the next on-time period.
COmin = 70 / (fs2 x L)
(63)
The maximum ESR allowed to prevent overvoltage protection during normal operation is:
ESRmax = (80 mV x L x Af) / ETmin
(64)
ETmin is calculated using VIN-MIN
Af = VOUT / 0.6 if there is no feed-forward capacitor used
Af = 1 if there is a feed-forward capacitor used
The minimum ESR must meet both of the following criteria:
ESRmin ≥ (15 mV x L x Af) / ETmax
ESRmin ≥ [ ETmax / (VIN - VOUT) ] x (Af / CO)
(65)
(66)
ETmax is calculated using VIN-MAX.
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Any additional parallel capacitors should be chosen so that their effective impedance will not negatively
attenuate the output ripple voltage.
6. Determine The Use of Feed-Forward Capacitor
Certain applications may require a feed-forward capacitor for improved stability and easier selection of
available output capacitance. Use the following equation to calculate the value of Cff.
ZFB = (RFB1 x RFB2)/(RFB1 + RFB2)
Cff = VOUT/(VIN-MIN x fS x ZFB)
(67)
(68)
7. MOSFET and RLIM Selection
The high-side and low-side FETs must have a drain to source (VDS) rating of at least 1.2 x VIN.
Use the following equations to calculate the desired target value of the low-side FET RDS(ON) for current limit.
ICL x RDS(ON)max
RLIM (Tj) =
ILIM-TH (Tj)
(69)
ILIM-TH(Tj) = ILIM-TH x [1 + 3.3 x 10-3 x (Tj - 27)]
(70)
The gate drive current from VCC must not exceed the minimum current limit of VCC. The drive current from
VCC can be calculated with:
IVCCdrive = Qgtotal x fS
where
•
Qgtotal is the combined total gate charge of the high-side and low-side FETs
(71)
The plateau voltage of the FET VGS vs Qg curve, as shown in Figure 17, must be less than VCC - 750 mV.
Figure 17. Typical MOSFET Gate Charge Curve
See following design example for estimated power dissipation calculation.
8. Calculate Input Capacitance
The main parameters for the input capacitor are the voltage rating, which must be greater than or equal to
the maximum DC input voltage of the power supply, and its rms current rating. The maximum rms current is
approximately 50% of the maximum load current.
Iomax x D x (1-D)
CIN =
fs x 'VIN-MAX
where
•
ΔVIN-MAX is the maximum allowable input ripple voltage. A good starting point for the input ripple voltage is 5%
of VIN
(72)
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When using low ESR ceramic capacitors on the input of the LM3150 controller, a resonant circuit can be
formed with the impedance of the input power supply and parasitic impedance of long leads/PCB traces to
the LM3150 input capacitors. TI recommends using a damping capacitor under these circumstances, such as
aluminum electrolytic that will prevent ringing on the input. The damping capacitor should be chosen to be
approximately five times greater than the parallel ceramic capacitors combination. The total input
capacitance should be greater than 10 times the input inductance of the power supply leads/PCB trace. The
damping capacitor should also be chosen to handle its share of the rms input current which is shared
proportionately with the parallel impedance of the ceramic capacitors and aluminum electrolytic at the
LM3150 switching frequency.
The CBYP capacitor should be placed directly at the VIN pin. The recommended value is 0.1 µF.
9. Calculate Soft-Start Capacitor
ISS x tSS
CSS =
Vref
where
•
•
tss is the soft-start time in seconds
Vref = 0.6V
(73)
10. CVCC, CBST, and CEN
CVCC should be placed directly at the VCC pin with a recommended value of 1 µF to 4.7 µF. CBST creates a
voltage used to drive the gate of the high-side FET. It is charged during the SW off-time. The recommended
value for CBST is 0.47 µF. The EN bypass capacitor, CEN, recommended value is 1000 pF when driving the
EN pin from open-drain type of signal.
9.2.3 Application Curves
Figure 18. 250-kHz Efficiency vs Load
Figure 19. 500-kHz Efficiency vs Load
Figure 20. 750-kHz Efficiency vs Load
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10 Power Supply Recommendations
The LM3150 controller is designed to operate from various DC power supplies. VIN input should be protected
from reversal voltage and voltage dump over 42 volts. The impedance of the input supply rail should be low
enough that the input current transient does not cause drop below VIN UVLO level. If the input supply is
connected by using long wires, additional bulk capacitance may be required in addition to normal input capacitor.
11 Layout
11.1 Layout Guidelines
It is good practice to layout the power components first, such as the input and output capacitors, FETs, and
inductor. The first priority is to make the loop between the input capacitors and the source of the low-side FET to
be very small and tie the grounds of the low-side FET and input capacitor directly to each other and then to the
ground plane through vias. As shown in Figure 21 when the input capacitor ground is tied directly to the source
of the low-side FET, parasitic inductance in the power path, along with noise coupled into the ground plane, are
reduced.
The switch node is the next item of importance. The switch node should be made only as large as required to
handle the load current. There are fast voltage transitions occurring in the switch node at a high frequency, and if
the switch node is made too large it may act as an antennae and couple switching noise into other parts of the
circuit. For high power designs, it is recommended to use a multilayer board. The FETs are going to be the
largest heat generating devices in the design, and as such, care should be taken to remove the heat. On
multilayer boards using exposed-pad packages for the FETs such as the power-pak SO-8, vias should be used
under the FETs to the same plane on the interior layers to help dissipate the heat and cool the FETs. For the
typical single FET Power-Pak type FETs, the high-side FET DAP is VIN. The VIN plane should be copied to the
other interior layers to the bottom layer for maximum heat dissipation. Likewise, the DAP of the low-side FET is
connected to the SW node and the SW node shape should be duplicated to the other PCB layers for maximum
heat dissipation.
See the Evaluation Board application note AN-1900 (SNVA371) for an example of a typical multilayer board
layout, and the Demonstration Board Reference Design Application Note for a typical 2-layer board layout. Each
design allows for single-sided component mounting.
VIN
M1
L
M2
CIN
COUT
Figure 21. Schematic of Parasitics
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11.2 Layout Example
HG
D
G
D
S
M1
+
-
S
D
D
S
VIN
S
D
L
VOUT
CIN
xx
S
S
LG
D
COUT
D
D
G
HG
LG
xx
PGND
vias to
ground plane
M2
LM3150
Figure 22. PCB Placement of Power Stage
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12 Device and Documentation Support
12.1 Documentation Support
12.1.1 Custom Design with WEBENCH Tools
Click here to create a custom design using the LM3150 device with the WEBENCH® Power Designer.
1. Start by entering your VIN, VOUT and IOUT requirements.
2. Optimize your design for key parameters like efficiency, footprint and cost using the optimizer dial and
compare this design with other possible solutions from Texas Instruments.
3. WEBENCH Power Designer provides you with a customized schematic along with a list of materials with real
time pricing and component availability.
4. In most cases, you will also be able to:
– Run electrical simulations to see important waveforms and circuit performance,
– Run thermal simulations to understand the thermal performance of your board,
– Export your customized schematic and layout into popular CAD formats,
– Print PDF reports for the design, and share your design with colleagues.
5. Get more information about WEBENCH tools at www.ti.com/webench.
12.1.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
12.1.3 Third-Party Products Disclaimer
TI'S PUBLICATION OF INFORMATION REGARDING THIRD-PARTY PRODUCTS OR SERVICES DOES NOT
CONSTITUTE AN ENDORSEMENT REGARDING THE SUITABILITY OF SUCH PRODUCTS OR SERVICES
OR A WARRANTY, REPRESENTATION OR ENDORSEMENT OF SUCH PRODUCTS OR SERVICES, EITHER
ALONE OR IN COMBINATION WITH ANY TI PRODUCT OR SERVICE.
12.1.4 Related Documentation
For related documentation see the following:
• AN-1900 LM3150 Evaluation Boards SNVA371
12.2 Community Resources
The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective
contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of
Use.
TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration
among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help
solve problems with fellow engineers.
Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and
contact information for technical support.
12.3 Trademarks
PowerWise, E2E are trademarks of Texas Instruments.
WEBENCH, SIMPLE SWITCHER are registered trademarks of Texas Instruments.
All other trademarks are the property of their respective owners.
12.4 Electrostatic Discharge Caution
These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam
during storage or handling to prevent electrostatic damage to the MOS gates.
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12.5 Glossary
SLYZ022 — TI Glossary.
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
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PACKAGE OPTION ADDENDUM
www.ti.com
6-Feb-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
Lead/Ball Finish
MSL Peak Temp
(2)
(6)
(3)
Op Temp (°C)
Device Marking
(4/5)
LM3150MH/NOPB
ACTIVE
HTSSOP
PWP
14
94
Green (RoHS
& no Sb/Br)
SN
Level-1-260C-UNLIM
-40 to 125
LM3150
MH
LM3150MHE/NOPB
ACTIVE
HTSSOP
PWP
14
250
Green (RoHS
& no Sb/Br)
SN
Level-1-260C-UNLIM
-40 to 125
LM3150
MH
LM3150MHX/NOPB
ACTIVE
HTSSOP
PWP
14
2500
Green (RoHS
& no Sb/Br)
SN
Level-1-260C-UNLIM
-40 to 125
LM3150
MH
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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