LTM8050IY#PBF [Linear]
LTM8050 - 58V, 2A Step-Down µModule (Power Module) Regulator; Package: BGA; Pins: 70; Temperature Range: -40°C to 85°C;
| 型号： | LTM8050IY#PBF |
| 厂家： | 
Linear |
| 描述： | LTM8050 - 58V, 2A Step-Down µModule (Power Module) Regulator; Package: BGA; Pins: 70; Temperature Range: -40°C to 85°C 开关 输出元件 |
| 文件： | 总24页 (文件大小：421K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTM8050
58V, 2A Step-Down
µModule Regulator
FEATURES
DESCRIPTION
The LTM®8050 is a 58V , 2A step down µModule® (mi-
n
Wide Input Voltage Range: 3.6V to 58V
IN
(60V Absolute Maximum)
cromodule) converter. Included in the package are the
switching controller, power switches, inductor and all
support components. Operating over an input voltage
range of 3.6V to 58V, the LTM8050 supports an output
voltage range of 0.8V to 24V and a switching frequency
range of 100kHz to 2.4MHz, each set by a single resistor.
Only the bulk input and output filter capacitors are needed
to finish the design.
n
Up to 2A Output Current
n
Parallelable for Increased Output Current
0.8V to 24V Output Voltage
n
n
Adjustable Switching Frequency: 100kHz to 2.4MHz
n
Configurable as an Inverter
n
Current Mode Control
n
Programmable Soft-Start
n
9mm × 15mm × 4.92mm BGA Package
The LTM8050 is packaged in a 9mm × 15mm × 4.92mm
ball grid array (BGA) package suitable for automated
assembly by standard surface mount equipment. The
LTM8050 is available with SnPb (BGA) or RoHS compli-
ant terminal finish.
APPLICATIONS
n
Automotive Battery Regulation
n
Power for Portable Products
L, LT, LTC, LTM, Linear Technology, the Linear logo, µModule and Burst Mode are registered
trademarks of Linear Technology Corporation. All other trademarks are the property of their
respective owners.
n
Distributed Supply Regulation
n
Industrial Supplies
Click to view associated TechClip Videos.
n
Wall Transformer Regulation
TYPICAL APPLICATION
Efficiency vs Output Current, 12VOUT
92
12VOUT, 2A µModule Regulator
V
= 24V
IN
V
*
V
90
88
86
84
82
80
IN
OUT
V
V
OUT
IN
17V TO 58V
12V AT 2A
V
= 36V
IN
RUN/SS
AUX
LTM8050 BIAS
PGOOD
4.7µF
V
= 48V
IN
SHARE
RT
22µF
FB
SYNC GND
57.6k
f = 600kHz
34.8k
*RUNNING VOLTAGE RANGE. PLEASE REFER TO
APPLICATIONS INFORMATION SECTION FOR START-UP DETAILS
8050 TA01a
0
0.5
1.0
1.5
2.0
OUTPUT CURRENT (A)
8050 TA01b
8050fc
1
For more information www.linear.com/LTM8050
LTM8050
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Notes 1, 3)
TOP VIEW
V , RUN/SS Voltage.................................................60V
1
2
3
4
5
6
7
IN
V
OUT
GND
FB, RT, SHARE Voltage ...............................................5V
A
B
C
D
E
F
V
, AUX.................................................................25V
OUT
PGOOD, SYNC, BIAS.................................................25V
IN
BANK 1
BANK 2
V + BIAS.................................................................72V
Maximum Junction Temperature (Note 2) ............ 125°C
Solder Temperature............................................... 245°C
Storage Temperature............................................. 125°C
RT
G
H
J
SHARE
PGOOD
FB
AUX
BIAS
K
L
BANK 3
V
RUN/SS SYNC
BGA PACKAGE
IN
70-PIN (15mm × 9mm × 4.92mm)
T
= 125°C, θ = 24.4°C/W, θ = 11.5°C/W,
JMAX
JA
JC(BOTTOM)
θ
= 42.7°C/W, θ = 18.7°C/W
JC(TOP)
JB
θ VALUES DETERMINED PER JESD51-9, MAX OUTPUT POWER
WEIGHT = 1.8 GRAMS
ORDER INFORMATION http://www.linear.com/product/LTM8050#orderinfo
PART MARKING*
PACKAGE
MSL
TEMPERATURE RANGE
(SEE NOTE 2)
PART NUMBER
LTM8050EY#PBF
LTM8050IY#PBF
LTM8050IY
PAD OR BALL FINISH
SAC305 (RoHS)
SAC305 (RoHS)
SnPb (63/37)
DEVICE
FINISH CODE
TYPE
BGA
BGA
BGA
BGA
BGA
RATING
LTM8050Y
LTM8050Y
LTM8050Y
LTM8050Y
LTM8050Y
e1
e1
e0
e1
e0
3
3
3
3
3
–40°C to 125°C
–40°C to 125°C
–40°C to 125°C
–55°C to 125°C
–55°C to 125°C
LTM8050MPY#PBF
LTM8050MPY
SAC305 (RoHS)
SnPb (63/37)
Consult Marketing for parts specified with wider operating temperature
ranges. *Device temperature grade is indicated by a label on the shipping
container. Pad or ball finish code is per IPC/JEDEC J-STD-609.
• Recommended LGA and BGA PCB Assembly and Manufacturing
Procedures:
www.linear.com/umodule/pcbassembly
• LGA and BGA Package and Tray Drawings:
www.linear.com/packaging
• Terminal Finish Part Marking:
www.linear.com/leadfree
8050fc
2
For more information www.linear.com/LTM8050
LTM8050
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, RUN/SS = 12V, BIAS = 3V unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
Minimum Input Voltage
Output DC Voltage
3.6
V
0 < I
0 < I
≤ 2A; R Open
0.8
24
V
V
OUT
OUT
FB
≤ 2A; R = 16.9k; V = 32V
FB
IN
Output DC Current
0
2
A
Quiescent Current into V
RUN/SS = 0V
Not Switching
BIAS = 0V, Not Switching
0.01
35
120
1
µA
µA
µA
IN
60
160
Quiescent Current into BIAS
RUN/SS = 0V
0.01
82
1
0.5
120
5
µA
µA
µA
Not Switching
BIAS = 0V, Not Switching
Line Regulation
5.5V < V < 58V, I
= 1A
0.3
0.3
10
%
%
IN
OUT
Load Regulation
0A < I
0A < I
< 2A
< 2A
OUT
OUT
Output Voltage Ripple (RMS)
Switching Frequency
Voltage (at FB Pin)
mV
kHz
R = 45.3k
T
750
790
775
770
805
810
mV
mV
l
Internal Feedback Resistor
Minimum BIAS Voltage for Proper Operation
RUN/SS Pin Current
499
6
kΩ
V
2.8
10
RUN/SS = 2.5V
µA
V
RUN Input High Voltage
RUN Input Low Voltage
2.5
0.2
1
V
PGOOD Threshold (at FB Pin)
PGOOD Leakage Current
PGOOD Sink Current
V
OUT
Rising
730
0.1
mV
µA
µA
V
PGOOD = 30V
PGOOD = 0.4V
200
0.7
600
SYNC Input Low Threshold
SYNC Input High Threshold
SYNC Bias Current
f
f
= 550kHz
= 550kHz
0.5
SYNC
SYNC
V
SYNC = 0V
0.1
µA
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTM8050E is guaranteed to meet performance specifications
from 0°C to 125°C internal. Specifications over the full –40°C to
125°C internal operating temperature range are assured by design,
characterization and correlation with statistical process controls. The
LTM8050I is guaranteed to meet specifications over the full –40°C
to 125°C internal operating temperature range. The LTM8050MP is
guaranteed to meet specifications over the full –55°C to 125°C internal
operating temperature range. Note that the maximum internal temperature
is determined by specific operating conditions in conjunction with board
layout, the rated package thermal resistance and other environmental
factors.
Note 3: Unless otherwise noted, the absolute minimum voltage is zero.
8050fc
3
For more information www.linear.com/LTM8050
LTM8050
Operating conditions are per Table 1 and
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted.
Efficiency vs Output Current,
2.5VOUT
Efficiency vs Output Current,
3.3VOUT
Efficiency vs Output Current,
5VOUT
90
85
80
75
70
65
60
85
80
75
70
65
60
90
85
80
75
5V
IN
12V
IN
12V
24V
36V
48V
12V
24V
36V
48V
IN
IN
IN
IN
IN
IN
IN
IN
70
24V
IN
36V
IN
48V
IN
65
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
2.0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G01
8050 G02
8050 G03
Efficiency vs Output Current,
8VOUT
Efficiency vs Output Current,
12VOUT
Efficiency vs Output Current,
18VOUT
94
92
90
88
86
84
82
80
78
76
92
90
88
86
84
82
80
94
92
90
88
86
84
82
12V
IN
IN
IN
IN
24V
36V
48V
24V
36V
48V
IN
IN
IN
36V
48V
IN
IN
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G04
8050 G05
8050 G06
Efficiency vs Output Current,
24VOUT
Efficiency, VOUT ≤ 2V, 2A Load,
BIAS = 5V
Input Current vs Output Current
2.5VOUT
80
75
70
65
60
55
50
45
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
5V
99
97
95
93
91
89
87
85
IN
12V
24V
36V
48V
IN
IN
IN
IN
5V
IN
12V
IN
IN
IN
IN
24V
36V
48V
36V
IN
IN
48V
0
0.5
1.0
1.5
1.00
1.25
1.50
(V)
1.75
2.00
0
0.5
1.0
1.5
2.0
OUTPUT CURRENT (A)
V
OUTPUT CURRENT (A)
OUT
8050 G07
8050 G08
8050 G09
8050fc
4
For more information www.linear.com/LTM8050
LTM8050
Operating conditions are per Table 1 and
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted.
Input Current vs Output Current
3.3VOUT
Input Current vs Output Current
5VOUT
Input Current vs Output Current
8VOUT
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
1.2
1.0
0.8
0.6
0.4
0.2
0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
12V
IN
12V
IN
12V
IN
24V
IN
24V
IN
24V
IN
36V
IN
36V
IN
36V
IN
48V
IN
48V
IN
48V
IN
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
2.0
1.5
2.0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G10
8050 G11
8050 G12
Input Current vs Output Current
12VOUT
Input Current vs Output Current
18VOUT
Input Current vs Output Current
24VOUT
1.2
1.0
0.8
0.6
0.4
0.2
0
1.2
1.0
0.8
0.6
0.4
0.2
0
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
24V
36V
48V
36V
48V
36V
48V
IN
IN
IN
IN
IN
IN
IN
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
0
0.5
1.0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G13
8050 G14
8050 G15
Input Current vs VIN Output
Shorted
Output Current vs VIN Output
Shorted
BIAS Current vs Output Current
2.5VOUT BIAS = 5V
400
300
200
100
0
5
4
3
2
1
0
16
12
8
12V
IN
RT = 215k (200kHz)
24V
IN
RT = 93.1k (400kHz)
RT = 57.6k (600kHz)
RT = 33.2k (900kHz)
36V
IN
48V
IN
4
RT = 215k (200kHz)
RT = 93.1k (400kHz)
RT = 57.6k (600kHz)
RT = 33.2k (900kHz)
0
0
20
40
60
80
0
20
40
60
80
0
0.5
1.0
1.5
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
OUTPUT CURRENT (A)
8050 G18
8050 G16
8050 G16
8050fc
5
For more information www.linear.com/LTM8050
LTM8050
Operating conditions are per Table 1 and
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted.
BIAS Current vs Output Current
3.3VOUT BIAS = 5V
BIAS Current vs Output Current
5VOUT BIAS = 5V
BIAS Current vs Output Current
8VOUT BIAS = 5V
20
15
10
5
30
20
10
0
50
12V
24V
36V
48V
12V
24V
36V
48V
12V
24V
36V
48V
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
40
30
20
10
0
0
0
0.5
1.0
1.5
2.0
2.0
25
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
2.0
1.5
2.0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G19
8050 G20
8050 G21
BIAS Current vs Output Current
12VOUT BIAS = 5V
BIAS Current vs Output Current
18VOUT BIAS = 5V
BIAS Current vs Output Current
24VOUT BIAS = 5V
40
30
20
10
0
50
40
30
20
10
0
80
70
60
50
40
30
20
10
0
24V
36V
48V
36V
48V
36V
48V
IN
IN
IN
IN
IN
IN
IN
0
0.5
1.0
1.5
0
0.5
1.0
1.5
0
0.5
1.0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G22
8050 G23
8050 G24
Minimum VIN vs VOUT Maximum
Load, BIAS = 5V
Minimum VIN vs Output Current
1.8VOUT and Below, BIAS = 5V
Minimum VIN vs Output Current
2.5VOUT, BIAS = 5V
40
35
30
25
20
15
10
5
4.00
3.75
3.50
3.25
3.00
4.2
4.1
4.0
3.9
3.8
3.7
3.6
3.5
0
0
5
10
V
15
(V)
20
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUT
8050 G25
8050 G26
8050 G27
8050fc
6
For more information www.linear.com/LTM8050
LTM8050
Operating conditions are per Table 1 and
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted.
Minimum VIN vs Output Current
3.3VOUT, BIAS = VOUT
Minimum VIN vs Output Current
5VOUT, BIAS = VOUT
Minimum VIN vs Output Current
8VOUT, BIAS = VOUT
6.0
5.5
5.0
4.5
4.0
3.5
3.0
7.55
7.50
7.45
7.40
7.35
7.30
7.25
7.20
7.15
7.10
7.05
12.5
12.0
11.5
11.0
10.5
10.0
9.5
RUNNING
TO START, RUN CONTROL
TO START, RUN = V
IN
9.0
8.5
RUNNING
RUNNING
TO START, RUN CONTROL
TO START, RUN CONTROL
8.0
TO START, RUN = V
TO START, RUN = V
IN
IN
7.5
0
0.5
1.0
1.5
2.0
2.0
2.0
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
2.0
1.5
2.0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G28
8050 G29
8050 G30
Minimum VIN vs Output Current
12VOUT, BIAS = VOUT
Minimum VIN vs Output Current
18VOUT, BIAS = VOUT
Minimum VIN vs Output Current
24VOUT, BIAS = 5V
17
16
15
14
13
12
11
26
25
24
23
22
21
20
19
35
34
33
32
31
30
29
28
27
26
25
RUNNING
TO START, RUN CONTROL
TO START, RUN = V
IN
0
0.5
1.0
1.5
0
0.5
1.0
1.5
0
0.5
1.0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G31
8050 G32
8050 G33
Minimum VIN vs Output Current
–3.3VOUT, BIAS = GND
Minimum VIN vs Output Current
–5VOUT, BIAS = GND
Minimum VIN vs Output Current
–8VOUT, BIAS = GND
30
25
20
15
10
5
25
20
15
10
5
25
20
15
10
5
RUNNING
RUNNING
RUNNING
TO START, RUN CONTROL
TO START, RUN CONTROL
TO START, RUN CONTROL
TO START, RUN = V
TO START, RUN = V
TO START, RUN = V
IN
IN
IN
0
0
0
0
0.5
1.0
1.5
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G34
8050 G35
8050 G36
8050fc
7
For more information www.linear.com/LTM8050
LTM8050
Operating conditions are per Table 1 and
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted.
Minimum VIN vs Output Current
–12VOUT, BIAS = GND
Minimum VIN vs Output Current
–18VOUT, BIAS = GND
25
20
15
10
5
25
RUNNING
RUNNING
TO START, RUN CONTROL
TO START, RUN CONTROL
TO START, RUN = V
TO START, RUN = V
IN
IN
20
15
10
5
0
0
0
0.5
1.0
1.5
0
0.25
0.50
0.75
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G37
8050 G38
Minimum VIN vs Output Current
–24VOUT, BIAS = GND
Internal Temperature Rise vs
Output Current, 2.5VOUT
25
20
15
10
5
30
20
10
0
RUNNING
TO START, RUN CONTROL
TO START, RUN = V
IN
5V
IN
12V
IN
IN
IN
IN
24V
36V
48V
0
0
0.1
0.2
0.3
0.4
0.5
0
0.5
1.0
1.5
2.0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G39
8050 G40
Internal Temperature Rise vs
Output Current, 3.3VOUT
Internal Temperature Rise vs
Output Current, 5VOUT
30
20
10
0
30
20
10
0
12V
12V
IN
IN
IN
IN
IN
IN
IN
IN
24V
36V
48V
24V
36V
48V
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
2.0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G41
8050 G42
8050fc
8
For more information www.linear.com/LTM8050
LTM8050
Operating conditions are per Table 1 and
TYPICAL PERFORMANCE CHARACTERISTICS
TA = 25°C, unless otherwise noted.
Internal Temperature Rise vs
Output Current, 8VOUT
Internal Temperature Rise vs
Output Current, 12VOUT
40
30
20
10
0
40
30
20
10
0
12V
24V
36V
48V
IN
IN
IN
IN
24V
36V
48V
IN
IN
IN
0
0.5
1.0
1.5
2.0
0
0.5
1.0
1.5
2.0
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G43
8050 G44
Internal Temperature Rise vs
Output Current, 18VOUT
Internal Temperature Rise vs
Output Current, 24VOUT
50
40
30
20
10
0
40
30
20
10
0
36V
48V
58V
24V
36V
48V
IN
IN
IN
IN
IN
IN
0
0.5
1.0
1.5
0
0.5
1.0
1.5
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8050 G46
8050 G45
Soft-Start Waveform for Various
CSS Values 1A Resistive Load,
DC1723A Demo Board
Output Ripple at 2A Load,
Standard DC1723A Demo Board
C
= 0µF
SS
FREE RUNNING
(400kHz)
C
= 0.1µF
SS
1V/DIV
600kHz SYNC
800kHz SYNC
10mV/DIV
C
= 0.47µF
SS
8050 G47
8050 G48
200µs/DIV
1µs/DIV
R
= 100k
SS
REFER TO DC1723A DEMO MANUAL FOR
PROPER RIPPLE MEASUREMENT TECHNIQUE
8050fc
9
For more information www.linear.com/LTM8050
LTM8050
PIN FUNCTIONS
PACKAGE ROW AND COLUMN LABELING MAY VARY
RUN/SS (Pin L5): Pull the RUN/SS pin below 0.2V to
shut down the LTM8050. Tie to 2.5V or more for normal
operation. If the shutdown feature is not used, tie this pin
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
LAYOUT CAREFULLY.
to the V pin. RUN/SS also provides a soft-start function;
V
(Bank 1): Power Output Pins. Apply the output filter
IN
OUT
see the Applications Information section.
capacitor and the output load between these pins and
GND pins.
SYNC (Pin L6): This is the external clock synchronization
input. Ground this pin for low ripple Burst Mode operation
at low output loads. Tie to a stable voltage source greater
than 0.7V to disable Burst Mode operation. Do not leave
this pin floating. Tie to a clock source for synchroniza-
tion. Clock edges should have rise and fall times faster
than 1μs. See the Synchronization section in Applications
Information.
GND (Bank 2): Tie these GND pins to a local ground plane
below the LTM8050 and the circuit components. In most
applications, the bulk of the heat flow out of the LTM8050
is through these pads, so the printed circuit design has a
large impact on the thermal performance of the part. See
the PCB Layout and Thermal Considerations sections for
moredetails.Returnthefeedbackdivider(R )tothisnet.
FB
RT (Pin G7): The RT pin is used to program the switching
frequency of the LTM8050 by connecting a resistor from
this pin to ground. Table 2 gives the resistor values that
correspondtotheresultantswitchingfrequency.Minimize
the capacitance at this pin.
V (Bank3):TheV pinsuppliescurrenttotheLTM8050’s
IN
IN
internal regulator and to the internal power switch. This
pin must be locally bypassed with an external, low ESR
capacitor; see Table 1 for recommended values.
AUX (Pin G5): Low Current Voltage Source for BIAS. In
SHARE (Pin H7): Tie this to the SHARE pin of another
LTM8050 when paralleling the outputs. Otherwise, do
not connect.
many designs, the BIAS pin is simply connected to V
.
OUT
and is placed
The AUX pin is internally connected to V
OUT
adjacent to the BIAS pin to ease printed circuit board rout-
ing. Although this pin is internally connected to V , it
OUT
PGOOD (Pin J7): The PGOOD pin is the open-collector
outputofaninternalcomparator.PGOODremainslowuntil
the FB pin is within 10% of the final regulation voltage.
is not intended to deliver a high current, so do not draw
current from this pin to the load. If this pin is not tied to
BIAS, leave it floating.
PGOODoutputisvalidwhenV isabove3.6VandRUN/SS
IN
is high. If this function is not used, leave this pin floating.
BIAS(PinH5):TheBIASpinconnectstotheinternalpower
bus. Connect to a power source greater than 2.8V and less
than 25V. If the output is greater than 2.8V, connect this
pin there. If the output voltage is less, connect this to a
voltage source between 2.8V and 25V. Also, make sure
FB (Pin K7): The LTM8050 regulates its FB pin to 0.79V.
Connect the adjust resistor from this pin to ground. The
value of R is given by the equation R = 394.21/(V
FB
FB
OUT
– 0.79), where R is in kΩ.
FB
that BIAS + V is less than 72V.
IN
8050fc
10
For more information www.linear.com/LTM8050
LTM8050
BLOCK DIAGRAM
V
V
OUT
8.2µH
15pF
IN
499k
1%
AUX
0.2µF
4.4µF
BIAS
RUN/SS
SHARE
SYNC
CURRENT
MODE
CONTROLLER
GND
RT
PGOOD
FB
8050 BD
OPERATION
The LTM8050 is a standalone nonisolated step-down
switching DC/DC power supply that can deliver up to 2A of
outputcurrent.Thismoduleprovidesapreciselyregulated
output voltage programmable via one external resistor
from 0.8V to 24V. The input voltage range is 3.6V to 58V.
Given that the LTM8050 is a step-down converter, make
sure that the input voltage is high enough to support the
desired output voltage and load current.
To further optimize efficiency, the LTM8050 automatically
switchestoBurstMode® operationinlightloadsituations.
Between bursts, all circuitry associated with controlling
the output switch is shut down reducing the input supply
current to 50μA in a typical application.
TheoscillatorreducestheLTM8050’soperatingfrequency
when the voltage at the FB pin is low. This frequency fold-
back helps to control the output current during start-up
and overload.
As shown in the Block Diagram, the LTM8050 contains a
current mode controller, power switching element, power
inductor, power Schottky diode and a modest amount of
input and output capacitance. The LTM8050 is a fixed
frequency PWM regulator. The switching frequency is set
by simply connecting the appropriate resistor value from
the RT pin to GND.
The LTM8050 contains a power good comparator which
trips when the FB pin is at roughly 90% of its regulated
value. The PGOOD output is an open-collector transistor
that is off when the output is in regulation, allowing an
externalresistortopullthePGOODpinhigh.Powergoodis
valid when the LTM8050 is enabled and V is above 3.6V.
IN
Aninternalregulatorprovidespowertothecontrolcircuitry.
The bias regulator normally draws power from the V
The LTM8050 is equipped with a thermal shutdown that
will inhibit power switching at high junction tempera-
tures. The activation threshold of this function, however,
is above 125°C to avoid interfering with normal operation.
Thus, prolonged or repetitive operation under a condition
in which the thermal shutdown activates may damage or
impair the reliability of the device.
IN
pin, but if the BIAS pin is connected to an external volt-
age higher than 2.8V, bias power will be drawn from the
external source (typically the regulated output voltage).
This improves efficiency. The RUN/SS pin is used to place
the LTM8050 in shutdown, disconnecting the output and
reducing the input current to less than 1μA.
8050fc
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For more information www.linear.com/LTM8050
LTM8050
APPLICATIONS INFORMATION
For most applications, the design process is straight
forward, summarized as follows:
Ceramic capacitors are small, robust and have very low
ESR. However, not all ceramic capacitors are suitable.
X5R and X7R types are stable over temperature and ap-
plied voltage and give dependable service. Other types,
including Y5V and Z5U have very large temperature and
voltage coefficients of capacitance. In an application cir-
cuit they may have only a small fraction of their nominal
capacitanceresultinginmuchhigheroutputvoltageripple
than expected.
1. Look at Table 1 and find the row that has the desired
input range and output voltage.
2. Apply the recommended C , C , R and R values.
IN OUT FB
T
3. Connect BIAS as indicated.
While these component combinations have been tested
for proper operation, it is incumbent upon the user to
verify proper operation over the intended system’s line,
load and environmental conditions. Bear in mind that the
maximum output current is limited by junction tempera-
ture, therelationshipbetweentheinputandoutputvoltage
magnitude and polarity and other factors. Please refer to
the graphs in the Typical Performance Characteristics
section for guidance.
Ceramic capacitors are also piezoelectric. In Burst Mode
operation, the LTM8050’s switching frequency depends
on the load current, and can excite a ceramic capacitor
at audio frequencies, generating audible noise. Since the
LTM8050 operates at a lower current limit during Burst
Mode operation, the noise is typically very quiet to a
casual ear.
If this audible noise is unacceptable, use a high perfor-
mance electrolytic capacitor at the output. It may also be
a parallel combination of a ceramic capacitor and a low
cost electrolytic capacitor.
The maximum frequency (and attendant R value) at
T
which the LTM8050 should be allowed to switch is given
in Table 1 in the f
column, while the recommended
MAX
frequency (and R value) for optimal efficiency over the
T
given input condition is given in the f
column.
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LTM8050. A
ceramic input capacitor combined with trace or cable
inductance forms a high Q (under damped) tank circuit.
If the LTM8050 circuit is plugged into a live supply, the
input voltage can ring to twice its nominal value, possi-
bly exceeding the device’s rating. This situation is easily
avoided; see the Hot-Plugging Safely section.
OPTIMAL
There are additional conditions that must be satisfied if
the synchronization function is used. Please refer to the
Synchronization section for details.
Capacitor Selection Considerations
The C and C
capacitor values in Table 1 are the
IN
OUT
minimum recommended values for the associated oper-
ating conditions. Applying capacitor values below those
indicated in Table 1 is not recommended, and may result
in undesirable operation. Using larger values is generally
acceptable, and can yield improved dynamic response, if
it is necessary. Again, it is incumbent upon the user to
verify proper operation over the intended system’s line,
load and environmental conditions.
Frequency Selection
The LTM8050 uses a constant frequency PWM architec-
ture that can be programmed to switch from 100kHz to
2.4MHz by using a resistor tied from the RT pin to ground.
Table 2 provides a list of R resistor values and their re-
T
sultant frequencies.
8050fc
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For more information www.linear.com/LTM8050
LTM8050
APPLICATIONS INFORMATION
Table 1: Recommended Component Values and Configuration (TA = 25°C)
V
IN
RANGE
V
V
C
C
R
FB
f
R
f
R
T(MIN)
OUT
BIAS
IN
OUT
OPTIMAL
T(OPTIMAL)
MAX
3.6V to 58V
3.6V to 58V
3.6V to 58V
3.6V to 58V
3.6V to 58V
4.1V to 58V
5.3V to 58V
7.5V to 58V
10.5V to 58V
17V to 58V
24V to 58V
34V to 58V
9V to 24V
0.8V
1V
2.8V to 25V
2.8V to 25V
2.8V to 25V
2.8V to 25V
2.8V to 25V
2.8V to 25V
AUX
Open
1.87M
953k
549k
383k
226k
154k
93.1k
54.9k
34.8k
22.6k
16.5k
Open
1.87M
953k
549k
383k
226k
154k
93.1k
54.9k
34.8k
Open
1.87M
953k
549k
383k
226k
154k
93.1k
54.9k
34.8k
22.6k
Open
1.87M
953k
549k
383k
226k
154k
93.1k
54.9k
34.8k
154k
93.1k
54.9k
34.8k
22.6k
16.5k
110kHz
110kHz
125kHz
150kHz
180kHz
230kHz
280kHz
400kHz
550kHz
600kHz
760kHz
900kHz
150kHz
180kHz
230kHz
280kHz
330kHz
345kHz
425kHz
500kHz
600kHz
760kHz
100kHz
120kHz
140kHz
180kHz
220kHz
300kHz
345kHz
425kHz
550kHz
760kHz
800kHz
100kHz
100kHz
100kHz
110kHz
125kHz
180kHz
280kHz
400kHz
550kHz
600kHz
300kHz
400kHz
550kHz
600kHz
760kHz
900kHz
392k
125kHz
125kHz
150kHz
180kHz
215kHz
270kHz
330kHz
460kHz
690kHz
750kHz
850kHz
960kHz
300kHz
345kHz
400kHz
460kHz
500kHz
600kHz
650kHz
700kHz
750kHz
850kHz
200kHz
250kHz
270kHz
300kHz
350kHz
425kHz
550kHz
800kHz
1.03MHz
1.03MHz
1.03MHz
125kHz
125kHz
150kHz
180kHz
215kHz
270kHz
330kHz
460kHz
690kHz
960kHz
330kHz
460kHz
690kHz
750kHz
850kHz
960kHz
340k
340k
280k
232k
191k
150k
118k
80.6k
49.9k
44.2k
37.4k
30.1k
130k
113k
93.1k
80.6k
73.2k
57.6k
52.3k
48.7k
44.2k
36.5k
205k
162k
150k
130k
110k
88.7k
64.9k
38.3k
25.5k
25.5k
25.5k
340k
340k
280k
232k
191k
150k
118k
80.6k
49.9k
30.1k
118k
80.6k
49.9k
44.2k
37.4k
30.1k
3× 4.7µF, 2220, 100V
3× 4.7µF, 2220, 100V
2× 4.7µF, 2220, 100V
2× 4.7µF, 2220, 100V
2× 4.7µF, 2220, 100V
4.7µF, 2220, 100V
4.7µF, 2220, 100V
4.7µF, 2220, 100V
4.7µF, 2220, 100V
4.7µF, 2220, 100V
4.7µF, 2220, 100V
4.7µF, 2220, 100V
4.7µF, 1206, 25V
4.7µF, 1206, 25V
4.7µF, 1206, 25V
4.7µF, 1206, 25V
4.7µF, 1206, 25V
4.7µF, 1206, 25V
4.7µF, 1206, 25V
4.7µF, 1206, 25V
4.7µF, 1206, 25V
2.2µF, 1206, 50V
1µF, 1206, 50V
3× 220µF, 1206, 4V
3× 220µF, 1206, 4V
3× 220µF, 1206, 4V
2× 220µF, 1206, 4V
2× 220µF, 1206, 4V
220µF, 1206, 4V
220µF, 1206, 4V
100µF, 1210, 6.3V
47µF, 1210, 10V
22µF, 1210, 16V
22µF, 1812, 25V
22µF, 1812, 25V
2× 220µF, 1206, 4V
2× 220µF, 1206, 4V
2× 220µF, 1206, 4V
220µF, 1206, 4V
220µF, 1206, 4V
100µF, 1210, 6.3V
100µF, 1210, 6.3V
47µF, 1210, 10V
47µF, 1210, 10V
22µF, 1210, 16V
3× 220µF, 1206, 4V
3× 220µF, 1206, 4V
2× 220µF, 1206, 4V
2× 220µF, 1206, 4V
220µF, 1206, 4V
100µF, 1210, 6.3V
100µF, 1210, 6.3V
47µF, 1210, 10V
22µF, 1210, 16V
22µF, 1210, 16V
22µF, 1812, 25V
3× 220µF, 1206, 4V
3× 220µF, 1206, 4V
3× 220µF, 1206, 4V
2× 220µF, 1206, 4V
2× 220µF, 1206, 4V
220µF, 1206, 4V
100µF, 1210, 6.3V
100µF, 1210, 6.3V
47µF, 1210, 10V
22µF, 1210, 16V
100µF, 1210, 6.3V
100µF, 1210, 6.3V
47µF, 1210, 10V
47µF, 1210, 16V
22µF, 1812, 25V
22µF, 1812, 25V
392k
340k
280k
232k
174k
140k
93.1k
64.9k
57.6k
42.2k
33.2k
280k
232k
174k
140k
118k
113k
88.7k
73.2k
57.6k
42.2k
432k
357k
301k
232k
187k
130k
113k
88.7k
64.9k
42.2k
38.3k
432k
432k
432k
392k
340k
232k
140k
93.1k
64.9k
57.6k
130k
93.1k
64.9k
57.6k
42.2k
33.2k
1.2V
1.5V
1.8V
2.5V
3.3V
5V
AUX
8V
AUX
12V
18V
24V
0.8V
1V
AUX
2.8V to 25V
2.8V to 25V
V
IN
9V to 24V
V
IN
9V to 24V
1.2V
1.5V
1.8V
2.5V
3.3V
5V
V
IN
9V to 24V
V
IN
V
IN
V
IN
9V to 24V
9V to 24V
9V to 24V
AUX
AUX
9V to 24V
10.5V to 24V
17V to 24V
18V to 36V
18V to 36V
18V to 36V
18V to 36V
18V to 36V
18V to 36V
18V to 36V
18V to 36V
18V to 36V
18V to 36V
24V to 36V
18V to 58V
18V to 58V
18V to 58V
18V to 58V
18V to 58V
18V to 58V
18V to 58V
18V to 58V
18V to 58V
18V to 58V
2.5V to 54.7V
3.3V to 53V
3.3V to 50V
4.5V to 46V
6V to 40V
8V
AUX
12V
0.8V
1V
AUX
2.8V to 25V
2.8V to 25V
2.8V to 25V
2.8V to 25V
2.8V to 25V
2.8V to 25V
AUX
1µF, 1206, 50V
1.2V
1.5V
1.8V
2.5V
3.3V
5V
1µF, 1206, 50V
1µF, 1206, 50V
1µF, 1206, 50V
1µF, 1206, 50V
1µF, 1206, 50V
AUX
1µF, 1206, 50V
8V
AUX
2.2µF, 1206, 50V
2.2µF, 1206, 50V
2.2µF, 1206, 50V
1µF, 1206, 100V
1µF, 1206, 100V
1µF, 1206, 100V
1µF, 1206, 100V
1µF, 1206, 100V
1µF, 1206, 100V
1µF, 1206, 100V
1µF, 1206, 100V
2.2µF, 1206, 100V
2.2µF, 1206, 100V
2× 4.7µF, 2220, 100V
4.7µF, 2220, 100V
4.7µF, 2220, 100V
4.7µF, 2220, 100V
4.7µF, 2220, 100V
4.7µF, 2220, 100V
12V
18V
0.8V
1V
AUX
2.8V to 25V
2.8V to 25V
2.8V to 25V
2.8V to 25V
2.8V to 25V
2.8V to 25V
2.8V to 25V
AUX
1.2V
1.5V
1.8V
2.5V
3.3V
5V
AUX
8V
AUX
12V
–3.3V
–5V
–8V
–12V
–18V
–24V
AUX
AUX
AUX
AUX
AUX
2.8V to 25V
2.8V to 25V
10V to 34V
Note: Do not allow V + BIAS to exceed 72V.
IN
8050fc
13
For more information www.linear.com/LTM8050
LTM8050
APPLICATIONS INFORMATION
Table 2. Switching Frequency vs RT Value
factors, such as load current, input voltage, output voltage
and switching frequency, but 4V to 5V works well in many
applications.Inallcases,ensurethatthemaximumvoltage
SWITCHING FREQUENCY (MHz)
R VALUE (kΩ)
T
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1
432
215
137
93.1
73.2
57.6
51.1
38.3
33.2
32.4
24.9
20
at the BIAS pin is less than 25V and that the sum of V
IN
and BIAS is less than 72V. If BIAS power is applied from
a remote or noisy voltage source, it may be necessary to
apply a decoupling capacitor locally to the pin.
Load Sharing
Two or more LTM8050’s may be paralleled to produce
highercurrents.To dothis,tietheV ,FB,V andSHARE
IN
OUT
pins of all the paralleled LTM8050’s together. To ensure
thatparalleledmodulesstartuptogether,theRUN/SSpins
may be tied together, as well. If the RUN/SS pins are not
tied together, make sure that the same valued soft-start
capacitors are used for each module. Current sharing
can be improved by synchronizing the LTM8050s. An
example of two LTM8050s configured for load sharing is
given in the Typical Applications section. When n number
of units are connected for parallel operation and a single
feedback resistor is used for all of them, the equation for
the feedback resistor is:
1.2
1.4
1.6
1.8
2
16.2
14
11
2.2
2.4
8.06
7.15
Operating Frequency Trade-offs
It is recommended that the user apply the optimal R
T
394.21
RFB =
kΩ
value given in Table 1 for the input and output operating
condition. System level or other considerations, however,
may necessitate another operating frequency. While the
LTM8050isflexibleenoughtoaccommodateawiderange
of operating frequencies, a haphazardly chosen one may
result in undesirable operation under certain operating or
fault conditions. A frequency that is too high can reduce
efficiency, generate excessive heat or even damage the
LTM8050 if the output is overloaded or short circuited. A
frequencythatistoolowcanresultinafinaldesignthathas
too much output ripple or too large of an output capacitor.
N V
–0.79
OUT
Burst Mode Operation
To enhance efficiency at light loads, the LTM8050 auto-
matically switches to Burst Mode operation which keeps
the output capacitor charged to the proper voltage while
minimizingtheinputquiescentcurrent.DuringBurstMode
operation, the LTM8050 delivers single cycle bursts of
current to the output capacitor followed by sleep periods
wheretheoutputpowerisdeliveredtotheloadbytheoutput
capacitor. Inaddition, V andBIASquiescentcurrentsare
IN
BIAS Pin Considerations
each reduced to microamps during the sleep time. As the
load current decreases towards a no load condition, the
percentage of time that the LTM8050 operates in sleep
mode increases and the average input current is greatly
reduced, resulting in higher efficiency.
The BIAS pin is used to provide drive power for the internal
power switching stage and operate other internal circuitry.
Forproperoperation,itmustbepoweredbyatleast2.8V.If
the output voltage is programmed to 2.8V or higher, BIAS
may be simply tied to AUX. If V
is less than 2.8V, BIAS
OUT
Burst Mode operation is enabled by tying SYNC to GND.
To disable Burst Mode operation, tie SYNC to a stable
voltage above 0.7V. Do not leave the SYNC pin floating.
can be tied to V or some other voltage source. If the BIAS
IN
pin voltage is too high, the efficiency of the LTM8050 may
suffer.TheoptimumBIASvoltageisdependentuponmany
8050fc
14
For more information www.linear.com/LTM8050
LTM8050
APPLICATIONS INFORMATION
Minimum Input Voltage
Thisinturnlimitstheamountofenergythatcanbedelivered
totheloadunderfault. Duringthestart-uptime, frequency
foldback is also active to limit the energy delivered to the
potentially large output capacitance of the load.
The LTM8050 is a step-down converter, so a minimum
amount of headroom is required to keep the output in
regulation. In addition, the input voltage required to turn
on is higher than that required to run, and depends upon
whether the RUN/SS is used. As shown in the Typical
Performance Characteristics section, the minimum input
voltagetoruna3.3Voutputatlightloadisonlyabout3.6V,
Synchronization
TheinternaloscillatoroftheLTM8050canbesynchronized
byapplyinganexternal250kHzto2MHzclocktotheSYNC
pin. Do not leave this pin floating. When synchronizing
but, if RUN/SS is pulled up to V , it takes 5.5V to start.
IN
IN
theLTM8050, selectanR resistorvaluethatcorresponds
If the LTM8050 is enabled with the RUN/SS pin after V
T
IN
to an operating frequency 20% lower than the intended
synchronization frequency (see the Frequency Selection
section).
is applied, the minimum voltage to start at light loads is
lower, about 4.3V. Similar curves detailing this behavior
of the LTM8050 for other outputs are also included in the
Typical Performance Characteristics section.
Inadditiontosynchronization,theSYNCpincontrolsBurst
Mode behavior. If the SYNC pin is driven by an external
clock, or pulled up above 0.7V, the LTM8050 will not
enter Burst Mode operation, but will instead skip pulses
to maintain regulation instead.
Soft-Start
The RUN/SS pin can be used to soft-start the LTM8050,
reducing the maximum input current during start-up. The
RUN/SS pin is driven through an external RC network to
create a voltage ramp at this pin. (See Figure 1). By choos-
ing an appropriate RC time constant, the peak start-up
current can be reduced to the current that is required to
regulate the output, with no overshoot. Choose the value
of the resistor so that it can supply at least 20μA when
the RUN/SS pin reaches 2.5V. Output voltage soft-start
Shorted Input Protection
Care needs to be taken in systems where the output will
be held high when the input to the LTM8050 is absent.
This may occur in battery charging applications or in
battery backup systems where a battery or some other
supply is diode ORed with the LTM8050’s output. If the
waveforms for various values of R and C are given in
SS
SS
V pin is allowed to float and the SHDN pin is held high
IN
the Typical Performance Characteristics section.
(either by a logic signal or because it is tied to V ), then
IN
the LTM8050’s internal circuitry will pull its quiescent
current through its internal power switch. This is fine if
your system can tolerate a few milliamps in this state. If
you ground the RUN/SS pin, the input current will drop
RUN
100k
RUN/SS
to essentially zero. However, if the V pin is grounded
IN
C
SS
RUN
while the output is held high, then parasitic diodes inside
the LTM8050 can pull large currents from the output
Figure 1. Apply an RC Network to RUN/SS to Control the
Soft-Start Behavior of the LTM8050 at Power-Up
through the V pin. Figure 2 shows a circuit that will run
IN
only when the input voltage is present and that protects
against a shorted or reversed input.
Frequency Foldback
The LTM8050 is equipped with frequency foldback which
actstoreducethethermalandenergystressontheinternal
power elements during a short circuit or output overload
condition.IftheLTM8050detectsthattheoutputhasfallen
out of regulation, the switching frequency is reduced as a
function of how far the output is below the target voltage.
PCB Layout
Most of the headaches associated with PCB layout have
been alleviated or even eliminated by the high level of
integration of the LTM8050. The LTM8050 is neverthe-
less a switching power supply, and care must be taken to
8050fc
15
For more information www.linear.com/LTM8050
LTM8050
APPLICATIONS INFORMATION
AUX
PGOOD
T
V
V
OUT
V
V
OUT
IN
IN
GND
GND
RUN/SS
AUX
R
R
FB
BIAS
LTM8050
SYNC
RUN/SS
BIAS
RT
FB
SYNC GND
V
OUT
V
IN
8050 F02
Figure 2. The Input Diode Prevents a Shorted Input from
Discharging a Backup Battery Tied to the Output. It Also Protects
the Circuit from a Reversed Input. The LTM8050 Runs Only
When the Input is Present
C
C
IN
OUT
GND
minimize EMI and ensure proper operation. Even with the
high level of integration, you may fail to achieve specified
operation with a haphazard or poor layout. See Figure 3
for a suggested layout. Ensure that the grounding and
heat sinking are acceptable.
THERMAL VIAS TO GND
8050 F03
Figure 3. Layout Showing Suggested External Components, GND
Plane and Thermal Vias
might use very small via holes. It should employ more
thermal vias than a board that uses larger holes.
1. Place the R and R resistors as close as possible to
FB
T
their respective pins.
Hot-Plugging Safely
2. Place the C capacitor as close as possible to the V
IN
IN
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypass capacitor of LTM8050. However, these capacitors
can cause problems if the LTM8050 is plugged into a live
supply (see Linear Technology Application Note 88 for a
complete discussion). The low loss ceramic capacitor
combined with stray inductance in series with the power
source forms an underdamped tank circuit, and the volt-
and GND connection of the LTM8050.
3. Place the C
capacitor as close as possible to the
OUT
V
and GND connection of the LTM8050.
OUT
4. Place the C and C
capacitors such that their
OUT
IN
ground current flow directly adjacent to or underneath
the LTM8050.
5. Connect all of the GND connections to as large a copper
pour or plane area as possible on the top layer. Avoid
breaking the ground connection between the external
components and the LTM8050.
age at the V pin of the LTM8050 can ring to more than
IN
twice the nominal input voltage, possibly exceeding the
LTM8050’s rating and damaging the part. If the input
supply is poorly controlled or the user will be plugging
the LTM8050 into an energized supply, the input network
should be designed to prevent this overshoot. This can be
6. Forgoodheatsinking,useviastoconnecttheGNDcop-
per area to the board’s internal ground planes. Liberally
distributetheseGNDviastoprovidebothagoodground
connectionandthermalpathtotheinternalplanesofthe
printed circuit board. Pay attention to the location and
density of the thermal vias in Figure 3. The LTM8050
can benefit from the heat-sinking afforded by vias that
connecttointernalGNDplanesattheselocations,dueto
theirproximitytointernalpowerhandlingcomponents.
The optimum number of thermal vias depends upon
the printed circuit board design. For example, a board
accomplishedbyinstallingasmallresistorinseriestoV ,
IN
but the most popular method of controlling input voltage
overshoot is to add an electrolytic bulk capacitor to the
V net. This capacitor’s relatively high equivalent series
IN
resistance damps the circuit and eliminates the voltage
overshoot. The extra capacitor improves low frequency
ripple filtering and can slightly improve the efficiency of
the circuit, though it is likely to be the largest component
in the circuit.
8050fc
16
For more information www.linear.com/LTM8050
LTM8050
APPLICATIONS INFORMATION
Negative Output Considerations
upon the user to verify proper operation over the intended
system’sline,loadandenvironmentaloperatingconditions.
The LTM8050 may be configured to generate a negative
output voltage. Examples of this are shown in the Typical
Applications section. For very fast rising input voltages,
care must be taken to ensure that start-up does not cre-
ate excessive surge currents that may create unwanted
voltages or even damage the LTM8050.
The thermal resistance numbers listed in Page 2 of the
data sheet are based on modeling the µModule package
mounted on a test board specified per JESD51-9 (Test
Boards for Area Array Surface Mount Package Thermal
Measurements). The thermal coefficients provided in this
page are based on JESD 51-12 (Guidelines for Reporting
and Using Electronic Package Thermal Information).
Consider the circuit in Figure 4. If a step input is applied
between V and system GND, the C and C capaci-
IN
IN
OUT
tors form an AC divider network that tends to create a
Forincreasedaccuracyandfidelitytotheactualapplication,
many designers use FEA to predict thermal performance.
To that end, Page 2 of the data sheet typically gives four
thermal coefficients:
positive voltage on system V . In order to protect the
OUT
load from seeing an excessive inverted voltage, an anti-
parallel Schottky diode may be used to clamp the voltage.
Furthermore, current flowing out of the BIAS pin can have
adverse affects. To prevent this from happening, apply a
series resistor (about 200Ω) and Schottky diode between
BIAS and its voltage source.
ꢀ θ – Thermal resistance from junction to ambient
JA
ꢀ θ
– Thermal resistance from junction to the
JCbottom
bottom of the product case
ꢀ θ – Thermal resistance from junction to top of the
JCtop
product case
Thermal Considerations
The LTM8050 output current may need to be derated if
it is required to operate in a high ambient temperature or
deliver a large amount of continuous power. The amount
of current derating is dependent upon the input voltage,
output power and ambient temperature. The temperature
rise curves given in the Typical Performance Character-
istics section can be used as a guide. These curves were
ꢀ θ – Thermal resistance from junction to the printed
JB
circuit board
While the meaning of each of these coefficients may seem
to be intuitive, JEDEC has defined each to avoid confusion
and inconsistency. These definitions are given in JESD
51-12, and are quoted or paraphrased below:
2
generated by a LTM8050 mounted to a 40cm 4-layer FR4
θ
JA
is the natural convection junction-to-ambient air
printedcircuitboard. Boardsofothersizesandlayercount
can exhibit different thermal behavior, so it is incumbent
thermal resistance measured in a one cubic foot sealed
enclosure. This environment is sometimes referred to as
ADD A SERIES RESISTOR AND
DIODE TO PREVENT CURRENT
FROM FLOWING OUT OF BIAS
V
V
V
OUT
IN
IN
RUN/SS
AUX
LTM8050
INRUSH
CURRENT
ADD AN ANTI-PARALLEL
CAN CAUSE
BIAS
PGOOD
ADJ
C
C
OUT
IN
DIODE TO CLAMP POSITIVE
VOLTAGE SPIKE
A POSITIVE
TRANSIENT
SHARE
RT
ON V
OUT
SYNC GND
V
(NEGATIVE VOLTAGE)
OUT
8050 F04
Figure 4. In Negative Output Voltage Applications, Prevent Adverse Effects from Fast Rising VIN by Adding Clamp and Rectifying Diodes
8050fc
17
For more information www.linear.com/LTM8050
LTM8050
APPLICATIONS INFORMATION
stillairalthoughnaturalconvectioncausestheairtomove.
This value is determined with the part mounted to a JESD
51-9 defined test board, which does not reflect an actual
application or viable operating condition.
a specified distance from the package, using a two sided,
two layer board. This board is described in JESD 51-9.
Giventhesedefinitions,itshouldnowbeapparentthatnone
of these thermal coefficients reflects an actual physical
operating condition of a µModule converter. Thus, none
of them can be individually used to accurately predict the
thermal performance of the product. Likewise, it would
be inappropriate to attempt to use any one coefficient to
correlate to the junction temperature vs load graphs given
in the product’s data sheet. The only appropriate way to
use the coefficients is when running a detailed thermal
analysis, such as FEA, which considers all of the thermal
resistances simultaneously.
θ
is the thermal resistance between the junction
JCbottom
andbottomofthepackagewithallofthecomponentpower
dissipation flowing through the bottom of the package. In
the typical µModule converter, the bulk of the heat flows
out the bottom of the package, but there is always heat
flow out into the ambient environment. As a result, this
thermal resistance value may be useful for comparing
packages but the test conditions don’t generally match
the user’s application.
θ
isdeterminedwithnearlyallofthecomponentpower
A graphical representation of these thermal resistances
follows:
JCtop
dissipation flowing through the top of the package. As the
electricalconnectionsofthetypicalµModuleconverterare
on the bottom of the package, it is rare for an application
to operate such that most of the heat flows from the junc-
The blue resistances are contained within the µModule
converter, and the green are outside.
The die temperature of the LTM8050 must be lower than
the maximum rating of 125°C, so care should be taken in
the layout of the circuit to ensure good heat sinking of the
LTM8050. The bulk of the heat flow out of the LTM8050
is through the bottom of the μModule converter and the
LGA pads into the printed circuit board. Consequently a
poor printed circuit board design can cause excessive
heating, resulting in impaired performance or reliability.
Please refer to the PCB Layout section for printed circuit
board design suggestions.
tion to the top of the part. As in the case of θ , this
JCbottom
value may be useful for comparing packages but the test
conditions don’t generally match the user’s application.
θ
is the junction-to-board thermal resistance where
JB
almost all of the heat flows through the bottom of the
µModule converter and into the board, and is really the
sum of the θ
and the thermal resistance of the
JCbottom
bottom of the part through the solder joints and through a
portion of the board. The board temperature is measured
JUNCTION-TO-AMBIENT RESISTANCE (JESD 51-9 DEFINED BOARD)
JUNCTION-TO-CASE (TOP)
RESISTANCE
CASE (TOP)-TO-AMBIENT
RESISTANCE
JUNCTION-TO-BOARD RESISTANCE
JUNCTION
A
t
JUNCTION-TO-CASE
(BOTTOM) RESISTANCE
CASE (BOTTOM)-TO-BOARD
RESISTANCE
BOARD-TO-AMBIENT
RESISTANCE
8050 F04
µMODULE DEVICE
8050fc
18
For more information www.linear.com/LTM8050
LTM8050
TYPICAL APPLICATIONS
1.8V Step-Down Converter
V
V
OUT
1.8V AT 2A
IN
V
V
OUT
IN
3.6V TO 58V
RUN/SS
AUX
10µF
3.3V
440µF
BIAS LTM8050
SHARE
PGOOD
FB
RT
SYNC GND
232k
f = 180kHz
383k
8050 TA02
2.5V Step-Down Converter
8V Step-Down Converter
V
*
V
OUT
IN
V
*
V
V
V
OUT
IN
OUT
IN
V
V
OUT
4.1V TO 58V
2.5V AT 2A
IN
11V TO 58V
8V AT 2A
RUN/SS
AUX
RUN/SS
AUX
LTM8050 BIAS
PGOOD
4.7µF
220µF
4.7µF
3.3V
BIAS LTM8050
SHARE
PGOOD
FB
SHARE
RT
47µF
RT
FB
SYNC GND
174k
f = 230kHz
SYNC GND
64.9k
f = 550kHz
226k
54.9k
8050 TA03
*RUNNING VOLTAGE RANGE. PLEASE REFER TO
APPLICATIONS INFORMATION SECTION FOR START-UP DETAILS
8050 TA04
*RUNNING VOLTAGE RANGE. PLEASE REFER TO
APPLICATIONS INFORMATION SECTION FOR START-UP DETAILS
Minimum VIN vs Output Current
–5VOUT, BIAS = GND
–5V Negative Output Converter
25
RUNNING
TO START, RUN CONTROL
V
IN
V
V
OUT
IN
TO START, RUN = V
IN
20
15
10
5
RUN/SS
AUX
LTM8050 BIAS
PGOOD
4.7µF
SHARE
RT
47µF
FB
93.1k
f = 400kHz
SYNC GND
93.1k
V
OUT
–5V
8050 TA05
0
0
0.5
1.0
1.5
2.0
OUTPUT CURRENT (A)
8050 TA05b
8050fc
19
For more information www.linear.com/LTM8050
LTM8050
TYPICAL APPLICATIONS
Two LTM8050s in Parallel, 2.5V at 3.8A
V
*
V
OUT
2.5V AT 3.8A
IN
V
V
OUT
IN
4.1V TO 58V
RUN/SS
AUX
LTM8050 BIAS
PGOOD
3V
SHARE
RT
10µF
FB
SYNC GND
174k
230kHz
113k
OPTIONAL
SYNC
V
V
OUT
IN
RUN/SS
AUX
LTM8050 BIAS
PGOOD
300µF
SHARE
RT
10µF
FB
SYNC GND
174k
230kHz
*RUNNING VOLTAGE RANGE. PLEASE REFER TO APPLICATIONS INFORMATION
SECTION FOR START-UP DETAILS
NOTE: SYNCHRONIZE THE TWO MODULES TO AVOID BEAT FREQUENCIES,
IF NECESSARY. OTHERWISE, TIE EACH SYNC TO GND
8050 TA06
3.3V Step-Down Converter
V
*
V
OUT
3.3V AT 2A
IN
V
V
OUT
IN
5.3V TO 58V
RUN/SS
AUX
LTM8050 BIAS
PGOOD
4.7µF
SHARE
RT
220µF
FB
SYNC GND
140k
f = 280kHz
154k
8050 TA07
*RUNNING VOLTAGE RANGE. PLEASE REFER TO
APPLICATIONS INFORMATION SECTION FOR START-UP DETAILS
8050fc
20
For more information www.linear.com/LTM8050
LTM8050
PACKAGE DESCRIPTION
PACKAGE ROW AND COLUMN LABELING MAY VARY
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
LAYOUT CAREFULLY.
Pin Assignment Table
(Arranged by Pin Number)
PIN NAME
PIN NAME
PIN NAME PIN NAME
PIN NAME
E1 GND
E2 GND
E3 GND
E4 GND
E5 GND
E6 GND
E7 GND
PIN NAME
F1 GND
F2 GND
F3 GND
F4 GND
F5 GND
F6 GND
F7 GND
A1
A2
A3
A4
V
V
V
V
B1
B2
B3
B4
V
V
V
V
C1
C2
C3
C4
V
V
V
V
D1
D2
D3
D4
V
V
V
V
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
A5 GND
A6 GND
A7 GND
B5 GND
B6 GND
B7 GND
C5 GND
C6 GND
C7 GND
D5 GND
D6 GND
D7 GND
PIN NAME
PIN NAME
PIN NAME
PIN NAME
PIN NAME
G1 GND
G2 GND
G3 GND
G4 GND
G5 AUX
G6 GND
G7 RT
H1
H2
H3
H4
-
-
-
-
J1
J2
J3
J4
V
V
V
-
K1
K2
K3
K4
V
V
V
-
L1
L2
L3
L4
V
V
V
-
IN
IN
IN
IN
IN
IN
IN
IN
IN
H5 BIAS
H6 GND
J5 GND
J6 GND
K5 GND
K6 GND
L5 RUN/SS
L6 SYNC
L7 GND
H7 SHARE J7 PGOOD K7 FB
8050fc
21
For more information www.linear.com/LTM8050
LTM8050
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/product/LTM8050#packaging for the most recent package drawings.
Z
/ / b b b
Z
3 . 8 1 0
2 . 5 4 0
1 . 2 7 0
0 . 3 1 7 5
0 . 3 1 7 5
1 . 2 7 0
0 . 0 0 0
2 . 5 4 0
3 . 8 1 0
8050fc
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representa-
22
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
LTM8050
REVISION HISTORY
REV
DATE
DESCRIPTION
PAGE NUMBER
A
02/14 Add SnPb BGA package option
1, 2
B
05/14 Add TechClip Video icons
1
8
Correct Typical Performance Characteristics labels
10/16 Corrected BIAS voltage from 33V to 3.3V (top of page)
C
19
8050fc
23
For more information www.linear.com/LTM8050
LTM8050
PACKAGE PHOTO
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
Pin Compatible; Remote Sensing; PLL, Tracking and Margining, 4.5V ≤ V ≤ 28V
LTM4601/LTM4603 12A and 6A DC/DC µModule
IN
LTM4604A
LTM4606
LTM8020
4A, Low V DC/DC µModule
2.375V ≤ V ≤ 5.5V, 0.8V ≤ V
≤ 5V, 9mm × 15mm × 2.3mm LGA Package
IN
IN
OUT
Low EMI 6A, 28V DC/DC µModule
200mA, 36V DC/DC µModule
4.5V ≤ V ≤ 28V, 0.6V ≤ V
≤ 5V, 15mm × 15mm × 2.8mm LGA Package
IN
OUT
OUT
4V ≤ V ≤ 36V, 1.25V ≤ V
≤ 5V, 6.25mm × 6.25mm × 2.32mm LGA Package
IN
LTM8022/LTM8023 1A and 2A, 36V DC/DC µModule
LTM8027 60V, 4A DC/DC µModule
Pin Compatible 3.6V ≤ V ≤ 36V, 0.8V ≤ V
≤ 10V, 11.25mm × 9mm × 2.82mm LGA Package
IN
OUT
4.5V ≤ V ≤ 60V; 2.5V ≤ V
≤ 24V, 15mm × 15mm × 4.32mm LGA Package
IN
OUT
DESIGN RESOURCES
SUBJECT
DESCRIPTION
Design:
• Selector Guides
µModule Design and Manufacturing Resources
Manufacturing:
• Quick Start Guide
• PCB Design, Assembly and Manufacturing Guidelines
• Package and Board Level Reliability
• Demo Boards and Gerber Files
• Free Simulation Tools
µModule Regulator Products Search
1. Sort table of products by parameters and download the result as a spread sheet.
2. Search using the Quick Power Search parametric table.
TechClip Videos
Quick videos detailing how to bench test electrical and thermal performance of µModule products.
Digital Power System Management
Linear Technology’s family of digital power supply management ICs are highly integrated solutions that
offer essential functions, including power supply monitoring, supervision, margining and sequencing,
and feature EEPROM for storing user configurations and fault logging.
8050fc
LT 1016 REV C • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
24
(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTM8050
●
●
ꢀLINEAR TECHNOLOGY CORPORATION 2013
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