LTM8056MPY#PBF [Linear]
LTM8056 - 58VIN, 48Vout Buck-Boost µModule (Power Module) Regulator; Package: BGA; Pins: 121; Temperature Range: -55°C to 125°C;
| 型号： | LTM8056MPY#PBF |
| 厂家： | 
Linear |
| 描述： | LTM8056 - 58VIN, 48Vout Buck-Boost µModule (Power Module) Regulator; Package: BGA; Pins: 121; Temperature Range: -55°C to 125°C 开关 输出元件 |
| 文件： | 总28页 (文件大小：1689K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
LTM8056
58V , 48V Buck-Boost
IN
OUT
µModule Regulator
FEATURES
DESCRIPTION
The LTM®8056 is a 58V , buck-boost µModule®
n
Complete Buck-Boost Switch Mode Power Supply
IN
n
Wide Input Voltage Range: 5V to 58V
(micromodule) regulator. Included in the package are the
switchingcontroller,powerswitches,inductorandsupport
components. A resistor to set the switching frequency, a
resistor divider to set the output voltage, and input and
output capacitors are all that are needed to complete the
design. Other features such as input and output average
current regulation may be implemented with just a few
components. The LTM8056 operates over an input volt-
age range of 5V to 58V, and can regulate output voltages
between 1.2V and 48V. The SYNC input and CLKOUT
output allow easy synchronization.
n
12V/1.7A Output from 6V
IN
IN
IN
n
n
n
n
n
n
n
n
n
n
12V/3.4A Output from 12V
12V/5.4A Output from 24V
Up to 96% Efficient
Adjustable Input and Output Average Current Limits
Input and Output Current Monitors
Parallelable for Increased Output Current
Wide Output Voltage Range: 1.2V to 48V
Selectable Switching Frequency: 100kHz to 800kHz
Synchronization from 200kHz to 700kHz
15mm × 15mm × 4.92mm BGA Package
The LTM8056 is housed in a compact overmolded ball
gridarray(BGA)packagesuitableforautomatedassembly
by standard surface mount equipment. The LTM8056 is
available with SnPB or RoHS compliant terminal finish.
APPLICATIONS
n
High Power Battery-Operated Devices
Buck-Boost Selection Table
n
Industrial Control
LTM8054
LTM8055
LTM8056
n
Solar Powered Voltage Regulator
Solar Powered Battery Charging
V
V
V
(Operation)
Abs Max
36
40
40
5.4
36
40
40
8.5
58
60
60
5.5
IN
n
IN
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.
Abs Max
OUT
I
(Peak)
OUT
24V , 12V
IN
OUT
Package
15 × 11.25mm ×
3.42mm BGA
15 × 15mm × 4.92mm BGA
Pin and Function Compatible
TYPICAL APPLICATION
Max Output Current and Efficiency vs VIN
24VOUT from 7VIN to 58VIN Buck-Boost Regulator
95
94
93
92
91
90
7
6
5
4
3
2
1
V
V
I
LTM8056
V
IN
IN
OUT
V
OUT
7V TO 58V
24V
SV
IN
IN
OUT
I
33µF
35V
100k
2.2µF
100V
×3
RUN
CTL
22µF
25V
SS
CLKOUT
I
INMON
SYNC
COMP
RT
I
OUTMON
FB
5.23k
43.2k
EFFICIENCY
LL MODE
GND
MAX OUTPUT CURRENT
8056 TA01a
0
0
10
20
30
(V)
40
50
V
f
= 525kHz
IN
SW
8056 TA01b
8056fa
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For more information www.linear.com/LTM8056
LTM8056
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
TOP VIEW
V , SV , V , RUN, I , I Voltage.....................60V
IN OUT
BANK 3
IN
IN OUT
SV
V
IN
IN
FB, SYNC, CTL, MODE Voltage ...................................6V
I
, I Voltage .............................................6V
INMON OUTMON
11
10
9
LL Voltage.................................................................15V
Maximum Junction Temperature (Notes 2, 3)....... 125°C
Storage Temperature.............................. –55°C to 125°C
Peak Solder Reflow Body Temperature ................. 245°C
I
BANK 1
GND
IN
8
7
6
5
RUN
4
BANK 2
V
OUT
I
3
INMON
I
2
OUTMON
GND
1
A
B
C
D
E
F
G
H
J
K
L
IOUT
LL
RT FB SS
CLKOUT
MODE SYNC
COMP
CTL
BGA PACKAGE
121-LEAD (15mm × 15mm × 4.92mm)
T
= 125°C, θ = 16.4°C/W, θ = 5.35°C/W, θ = 15.3°C/W, θ = 5.9°C/W,
JMAX
JA
JCbottom
JCtop
JB
WEIGHT = 2.8g, θ VALUES DETERMINED PER JEDEC JESD51-9, 51-12
ORDER INFORMATION http://www.linear.com/product/LTM8056#orderinfo
PART NUMBER
BALL FINISH
PART MARKING*
PACKAGE
TYPE
MSL
TEMPERATURE RANGE
(Note 2)
RATING
DEVICE
FINISH CODE
LTM8056EY#PBF
LTM8056IY#PBF
LTM8056IY
SAC305 (RoHS)
SAC305 (RoHS)
SnPb (63/37)
LTM8056Y
LTM8056Y
LTM8056Y
LTM8056Y
LTM8056Y
e1
e1
e0
e1
e0
BGA
BGA
BGA
BGA
BGA
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
LTM8056MPY#PBF
LTM8056MPY
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
8056fa
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For more information www.linear.com/LTM8056
LTM8056
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. RUN = 1.5V unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
Minimum Input Voltage
Output DC Voltage
V
= SV
5.0
V
IN
IN
FB = V
Through 100k
1.2
48
V
V
OUT
I
= 0.1A, R = 100k/2.55k
FB
OUT
Output DC Current
V
V
= 6V, V
= 12V
OUT
OUT
1.7
4
A
A
IN
IN
= 48V, V
= 12V
Quiescent Current Into V (Tied to SV )
RUN = 0.3V (Disabled)
No Load, MODE = 0.3V (DCM)
No Load, MODE = 1.5V (FCM)
0.1
8
45
1
µA
mA
mA
IN
IN
30
100
Output Voltage Line Regulation
Output Voltage Load Regulation
Output RMS Voltage Ripple
Switching Frequency
5V < V < 58V, I
= 1A
OUT
0.5
0.5
25
%
%
IN
V
V
= 12V, 0.1A < I
< 3.5A
IN
IN
OUT
= 24V, I
= 3A
mV
OUT
R = 453k
100
800
kHz
kHz
T
R = 24.9k
T
Voltage at FB Pin
1.188
1.176
1.212
1.220
V
V
l
l
RUN Falling Threshold
RUN Hysteresis
LTM8056 Stops Switching
LTM8056 Starts Switching
LTM8056 Disabled
1.15
1.25
V
mV
V
25
RUN Low Threshold
RUN Pin Current
0.3
RUN = 1V
RUN = 1.6V
2
3
5
100
µA
nA
I
Bias Current
90
µA
mV
µA
IN
l
l
Input Current Sense Threshold (I -V )
44
56
IN IN
I
Bias Current
20
OUT
Output Current Sense Threshold (V -I
)
V
= Open
CTL
54.5
53
61.5
63
mV
mV
OUT OUT
I
I
Voltage
LTM8056 in Input Current Limit
LTM8056 in Output Current Limit
0.96
1.14
1.04
1.26
V
V
INMON
Voltage
OUTMON
CTL Input Bias Current
SS Pin Current
V
V
= 0V
22
35
µA
µA
V
CTL
= 0V
SS
CLKOUT Output High
CLKOUT Output Low
10k to GND
10k to 5V
4
0.7
0.3
V
SYNC Input Low Threshold
SYNC Input High Threshold
SYNC Bias Current
V
1.5
V
SYNC = 1V
11
µA
V
MODE Input Low Threshold
MODE Input High Threshold
0.3
1.5
V
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.
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 2: The LTM8056E 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
LTM8056I is guaranteed to meet specifications over the full –40°C
to 125°C internal operating temperature range. The LTM8056MP is
guaranteed to meet specifications over the full –55°C to 125°C internal
Note 3: The LTM8056 contains overtemperature protection that is
intended to protect the device during momentary overload conditions. The
internal temperature exceeds the maximum operating junction temperature
when the overtemperature protection is active. Continuous operation
above the specified maximum operating junction temperature may impair
device reliability.
8056fa
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For more information www.linear.com/LTM8056
LTM8056
TA = 25°C, unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
Efficiency vs Output Current
(3.3VOUT
Efficiency vs Output Current
(5VOUT
Efficiency vs Output Current
(8VOUT
)
)
)
100
80
100
80
100
80
60
60
60
5V
12V
24V
5V
12V
22V
IN
IN
IN
5V
12V
24V
IN
IN
IN
IN
IN
IN
40
40
40
0
2
4
6
0
2
4
6
0
2
4
6
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8056 G01
8056 G02
8056 G03
Efficiency vs Output Current
(12VOUT
Efficiency vs Output Current
(18VOUT
Efficiency vs Output Current
(24VOUT
)
)
)
100
90
100
90
100
95
90
85
80
75
80
80
70
7V
IN
5V
12V
6V
IN
IN
IN
IN
IN
IN
12V
24V
36V
48V
12V
IN
IN
IN
IN
IN
IN
24V
36V
24V
48V
70
0
2
4
6
0
2
4
6
0
2
4
6
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8056 G04
8056 G05
8056 G06
Efficiency vs Output Current
(36VOUT
Efficiency vs Output Current
(48VOUT
Input Current vs Output Current
(3.3VOUT
)
)
)
100
95
100
95
4
3
2
1
0
5V
12V
24V
IN
IN
IN
90
90
9V
IN
12V
13V
IN
IN
IN
IN
IN
IN
IN
IN
24V
36V
48V
24V
36V
48V
85
85
0
2
4
6
0
1
2
3
4
0
2
4
6
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8056 G07
8056 G08
8056 G09
8056fa
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For more information www.linear.com/LTM8056
LTM8056
TA = 25°C, unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
Input Current vs Output Current
(5VOUT
Input Current vs Output Current
(8VOUT
Input Current vs Output Current
(12VOUT
)
)
)
4
3
2
1
0
5
4
3
2
1
0
4
3
2
5V
12V
22V
5V
12V
24V
IN
IN
IN
IN
IN
IN
1
0
5V
IN
12V
24V
36V
IN
IN
IN
0
2
4
6
0
0
0
2
4
6
0
2
4
6
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8056 G10
8056 G11
8056 G12
Input Current vs Output Current
(18VOUT
Input Current vs Output Current
(24VOUT
Input Current vs Output Current
(36VOUT
)
)
)
5
5
5
4
3
2
1
0
4
3
2
4
3
2
9V
7V
IN
IN
12V
24V
36V
48V
12V
24V
36V
48V
IN
IN
IN
IN
IN
IN
IN
IN
6V
IN
1
0
1
0
12V
24V
48V
IN
IN
IN
0
2
4
6
2
4
6
0
2
4
6
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8056 G13
8056 G14
8056 G15
Input Current vs Output Current
(48VOUT
)
Maximum Output Current vs VIN
Maximum Output Current vs VIN
4
3
2
1
0
6
5
4
3
2
6
5
4
3
2
1
0
13V
24V
36V
48V
IN
IN
IN
IN
3.3V
12V
18V
24V
OUT
OUT
OUT
OUT
5V
8V
OUT
OUT
0
0.5 1.0 1.5 2.0 2.5 3.0
OUTPUT CURRENT (A)
3.5
10
20
30
0
20
30
40
50
V
(V)
V
(V)
IN
IN
8056 G16
8056 G17
8056 G18
8056fa
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For more information www.linear.com/LTM8056
LTM8056
TA = 25°C, unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
Temperature Rise vs Output
Temperature Rise vs Output
Current (5VOUT
Maximum Output Current vs VIN
Current (3.3VOUT
)
)
6
4
2
0
80
60
40
20
0
100
80
60
40
20
0
5V
12V
24V
5V
12V
22V
IN
IN
IN
IN
IN
IN
36V
48V
OUT
OUT
0
10
20
30
40
50
0
2
4
6
0
2
4
6
V
(V)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
IN
8056 G19
8056 G20
8056 G21
Temperature Rise vs Output
Current (8VOUT
Temperature Rise vs Output
Current (12VOUT
Temperature Rise vs Output
Current (18VOUT
)
)
)
100
80
60
40
20
0
100
80
60
40
20
0
100
80
60
40
20
0
6V
5V
IN
IN
12V
5V
12V
IN
IN
IN
IN
IN
IN
IN
IN
IN
24V
48V
12V
24V
36V
24V
0
2
4
6
0
2
4
6
0
2
4
6
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8056 G22
8056 G23
8056 G24
Temperature Rise vs Output
Temperature Rise vs Output
Temperature Rise vs Output
Current (48VOUT)
Current (24VOUT
)
Current (36VOUT
)
100
80
60
40
20
0
100
80
60
40
20
0
100
80
60
40
20
0
7V
9V
IN
IN
12V
12V
13V
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
IN
24V
36V
48V
24V
36V
48V
24V
36V
48V
0
2
4
6
0
2
4
6
0
1
2
3
4
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
OUTPUT CURRENT (A)
8056 G25
8056 G26
8056 G27
8056fa
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For more information www.linear.com/LTM8056
LTM8056
TA = 25°C, unless otherwise noted.
TYPICAL PERFORMANCE CHARACTERISTICS
Soft-Start Waveforms for Various
Maximum Output Current vs CTL
Voltage DC2154A Demo Board,48VIN
CSS Values 24VIN, 3A Resistive
Load, DC2154A Demo Board
Output Ripple, Stock DC2154A
Demo Board, 24VOUT
4
3
2
1
0
12V , 1.5A LOAD
IN
(B00ST),
C
= 22nF
SS
100mV/DIV
C
SS
= 220nF
24V , 3A LOAD
IN
(BUCK-B00ST),
100mV/DIV
V
OUT
5V/DIV
C
= 100nF
SS
48V , 3A LOAD
IN
(Buck),
100mV/DIV
8056 G30
1µs/DIV
8056 G29
500µs/DIV
0
0.4
0.7
1.1
1.4
MEASURED ACROSS C17 ON DC2154A WITH HP461
AMPLIFIER, 150MHz BANDWIDTH
CTL VOLTAGE (V)
8056 G28
PIN FUNCTIONS
GND(Bank1,PinL1):TietheseGNDpinstoalocalground
plane below the LTM8056 and the circuit components.
In most applications, the bulk of the heat flow out of the
LTM8056 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
LL (Pin F1): Light Load Indicator. This open drain pin
indicates that the output current, as sensed through the
resistor connected between V
and I , is approxi-
OUT
OUT
mately equivalent to 6mV or less. Its state is meaningful
only if a current sense resistor is applied between V
OUT
and I . This is useful to change the switching behavior
OUT
sections for more details. Return the R /R feedback
divider to this net.
of the LTM8056 in light load conditions.
FB1 FB2
SV (Pins F10, F11): Controller Power Input. Apply a
IN
V
(Bank 2): Power Output Pins. Apply output filter
separate voltage above 5V if the LTM8056 is required to
OUT
capacitors between these pins and GND pins.
operate when the main power input (V ) is below 5V.
IN
Bypass these pins with a high quality, low ESR capacitor.
V (Bank 3): Input Power. The V pin supplies current to
IN
IN
If a separate supply is not used, connect these pins to V .
IN
theLTM8056’sinternalpowerswitchesandtooneterminal
of the optional input current sense resistor. This pin must
be locally bypassed with an external, low ESR capacitor;
see Table 1 for recommended values.
CLKOUT (Pin G1): Clock Output. Use this pin as a clock
source when synchronizing other devices to the switch-
ing frequency of the LTM8056. When this function is not
used, leave this pin open.
I
(Pin D1): Output Current Sense. Tie this pin to the
OUT
output current sense resistor. The output average current
MODE (Pin G2): Switching Mode Input. The LTM8056
operates in forced continuous mode when MODE is
open, and can operate in discontinuous switching mode
when MODE is low. In discontinuous switching mode,
the LTM8056 will block reverse inductor current. This pin
is normally left open or tied to LL. This pin may be tied
to GND for the purpose of blocking reverse current if no
output sense resistor is used.
sense threshold is 58mV, so the LTM8056 will regulate
the output current to 58mV/R
, where R
is the
SENSE
SENSE
value of the output current sense resistor in ohms. The
load is powered through the sense resistor connected at
this pin. Tie this pin to V
resistor is used. Keep this pin within 0.5V of V
all conditions.
if no output current sense
OUT
under
OUT
8056fa
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For more information www.linear.com/LTM8056
LTM8056
PIN FUNCTIONS
RT (PinH1):TimingResistor.TheRT pinisusedtoprogram
the switching frequency of the LTM8056 by connecting a
resistor from this pin to ground. The range of oscillation is
100kHzto800kHz.TheApplicationsInformationsectionof
the data sheet includes a table to determine the resistance
value based on the desired switching frequency. Minimize
capacitance at this pin. A resistor to ground must be ap-
plied under all circumstances.
CTL (Pin K2): Current Sense Adjustment. Apply a voltage
below 1.2V to reduce the current limit threshold of I
Drive CTL to less than about 50mV to stop switching. The
CTL pin has an internal pull-up resistor to 2V. If not used,
leave this pin open.
.
OUT
I
(Pin L2): Output Current Monitor. This pin pro-
OUTMON
duces a voltage that is proportional to the voltage between
and I . I will equal 1.2V when V – I
OUT
V
OUT
OUT OUTMON
OUT
SYNC(PinH2):ExternalSynchronizationInput.TheSYNC
pin has an internal pull-down resistor. See the Synchroni-
zation section in Applications Information for details. Tie
this pin to GND when not used.
= 58mV. This feature is generally useful only if a current
sense resistor is applied between V and I . This is
OUT
OUT
a high impedance output. Use a buffer to drive a load.
I
(Pin L3): Input Current Monitor. This pin produces
INMON
FB (Pin J1): Output Voltage Feedback. The LTM8056
regulates the FB pin to 1.2V. Connect the FB pin to a
resistive divider between the output and GND to set the
output voltage. See Table 1 for recommended FB divider
resistor values.
a voltage that is proportional to the voltage between I
IN
and V . I
will equal 1V when I -V = 50mV. This
IN IN
IN INMON
feature is generally useful only if a current sense resistor
is applied between V and I .
IN
IN
RUN(PinL4):LTM8056Enable.RaisetheRUNpinvoltage
above1.2Vfornormaloperation. Above1.2V(typical), but
below 6V, the RUN pin input bias current is less than 1μA.
Below 1.2V and above 0.3V, the RUN pin sinks 3μA so
the user can define the hysteresis with the external resis-
tor selection. This will also reset the soft-start function.
If RUN is 0.3V or less, the LTM8056 is disabled and the
COMP (Pin J2): Compensation Pin. The LTM8056 is
equipped with internal compensation that works well with
most applications. In some cases, the performance of the
LTM8056 can be enhanced by modifying the control loop
compensation by applying a capacitor or RC network to
this pin.
SV quiescent current is below 1μA.
IN
SS (Pin K1): Soft-Start. Connect a capacitor from this pin
to GND to increase the soft-start time. Soft-start reduces
the input power source’s surge current by gradually in-
creasing the controller’s current limit. Larger values of the
soft-start capacitor result in longer soft-start times. If no
soft-start is required, leave this pin open.
I (Pin L9): Input Current Sense. Tie this pin to the input
IN
current sense resistor. The input average current sense
threshold is 50mV, so the LTM8056 will regulate the input
current to 50mV/R
, where R
is the value of the
SENSE
SENSE
input current sense resistor in ohms. Tie to V when not
IN
used.Keepthispinwithin 0.5VofV underallconditions.
IN
8056fa
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For more information www.linear.com/LTM8056
LTM8056
BLOCK DIAGRAM
V
V
IN
OUT
SV
IN
I
OUT
6.8µH
I
IN
0.2µF
0.1µF
100V
RUN
GND
2V
100k 100k
FB
SS
CLKOUT
BUCK-BOOST CONTROLLER
I
0.1µF
INMON
I
CTL
OUTMON
MODE
COMP
LL
RT
SYNC
8056 BD
8056fa
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LTM8056
OPERATION
The LTM8056 is a standalone nonisolated buck-boost
switching DC/DC power supply. The buck-boost topol-
ogy allows the LTM8056 to regulate its output voltage
for input voltages both above and below the magnitude
of the output, and the maximum output current depends
upon the input voltage. Higher input voltages yield higher
maximum output current.
Furthermore, while the LTM8056 does not require an
output sense resistor to operate, it uses information from
the sense resistor to optimize its performance. If an out-
put sense resistor is not used, the efficiency or output
ripple may degrade, especially if the current through the
integrated inductor is discontinuous. In some cases, an
output sense resistor is required to adequately protect the
LTM8056 against output overload or short-circuit.
This converter provides a precisely regulated output volt-
age programmable via an external resistor divider from
1.2V to 48V. The input voltage range is 5V to 58V, but the
A voltage less than 1.2V applied to the CTL pin reduces
the maximum output current if an output current sense
resistorisused. DriveCTLtolessthanabout50mVtostop
switching. The current flowing through the sense resistor
LTM8056 may be operated at lower input voltages if SV
IN
is powered by a voltage source above 5V. A simplified
block diagram is given on the previous page.
is reflected by the output voltage of the I
pin.
OUTMON
The LTM8056 contains a current mode controller, power
switchingelements, powerinductorandamodestamount
of input and output capacitance. The LTM8056 is a fixed
frequency PWM regulator. The switching frequency is set
by connecting the appropriate resistor value from the RT
pin to GND.
Driving the SYNC pin will synchronize the LTM8056 to an
external clock source. The CLKOUT pin sources a signal
that is the same frequency but approximately 180° out of
phase with the internal oscillator.
If more output current is required than a single LTM8056
can provide, multiple devices may be operated in parallel.
Refer to the Parallel Operation section of Applications
Information for more details.
TheoutputvoltageoftheLTM8056issetbyconnectingthe
FB pin to a resistor divider between the output and GND.
In addition to regulating its output voltage, the LTM8056
isequippedwithaveragecurrentcontrolloopsforboththe
Aninternalregulatorprovidespowertothecontrolcircuitry
and the gate driver to the power MOSFETs. This internal
input and output. Add a current sense resistor between I
regulator draws power from the SV pin. The RUN pin is
IN
IN
and V to limit the input current below some maximum
used to place the LTM8056 in shutdown, disconnecting
the output and reducing the input current to less than 1μA.
IN
value. The I
the sense resistor between I and V .
pin reflects the current flowing though
INMON
IN
IN
The LTM8056 is equipped with a thermal shutdown that
inhibits power switching at high junction temperatures.
The activation threshold of this function is above 125°C
to avoid interfering with normal operation, so prolonged
or repetitive operation under a condition in which the
thermal shutdown activates may damage or impair the
reliability of the device.
A current sense resistor between V
and I
allows
OUT
OUT
the LTM8056 to accurately regulate its output current to
a maximum value set by the value of the sense resistor.
In general, the LTM8056 should be used with an output
sense resistor to limit the maximum output current, as
buck-boost regulators are capable of delivering large cur-
rents when the output voltage is lower than the input, if
demanded.
8056fa
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LTM8056
APPLICATIONS INFORMATION
For most applications, the design process is straight for-
ward, summarized as follows:
The maximum frequency (and attendant R value) at
T
which the LTM8056 should be allowed to switch is given
in Table 1 in the f
column, while the recommended
MAX
1. Look at Table 1 and find the row that has the desired
input range and output voltage.
frequency (and R value) for optimal efficiency over the
T
given input condition is given in the f
column.
OPTIMAL
2. Apply the recommended C , C , R /R and R
There are additional conditions that must be satisfied if
the synchronization function is used. Please refer to the
Synchronization section for details.
IN OUT FB1 FB2
T
values.
3. Applytheoutputsenseresistortosettheoutputcurrent
limit. The output current is limited to 58mV/R
,
Note that Table 1 calls out both ceramic and electrolytic
output capacitors. Both of the capacitors called out in
the table must be applied to the output. The electrolytic
capacitors in Table 1 are described by voltage rating,
value and ESR. The voltage rating of the capacitor may
be increased if the application requires a higher voltage
stress derating. The LTM8056 can tolerate variation
in the ESR; other capacitors with different ESR may
be used, but the user must verify proper operation
over line, load and environmental conditions. Table 2
gives the description and part numbers of electrolytic
capacitors used in the LTM8056 development testing and
design validation.
SENSE
where R
is the value of the output current sense
SENSE
resistor in ohms.
Whilethesecomponentcombinationshavebeentestedfor
proper operation, it is incumbent upon the user to verify
properoperation over theintended system’s line, load and
environmentalconditions. Bearinmindthatthemaximum
output current is limited by junction temperature, the rela-
tionship between the input and output voltage magnitude
and other factors. Please refer to the graphs in the Typical
Performance Characteristics section for guidance.
Table 1. Recommended Component Values and Configuration (TA = 25°C)
RANGE
V
V
C
C
R /R
FB1 FB2
f
(kHz)
R
f
(kHz)
R
T(MAX)
IN
OUT
IN
OUT
OPTIMAL
T(OPTIMAL)
MAX
5V to 24V
5V to 22V
5V to 28V
5V to 41V
5.8V to 58V
7V to 58V
8.5V to 58V
3.3V
2 × 4.7µF, 50V, 0805
2 × 4.7µF, 50V, 0805
2 × 4.7µF, 50V, 0805
2 × 4.7µF, 50V, 0805
22µF, 6.3V, X5R, 0805
100k/56.2k
100k/31.6k
100k/17.4k
100k/11k
650
31.6k
800
24.9k
24.9k
24.9k
24.9k
24.9k
24.9k
24.9k
24.9k
100µF, 6V, 75mΩ, Electrolytic
5V
22µF, 6.3V, X5R, 0805
100µF, 6V, 75mΩ, Electrolytic
450
500
650
650
525
500
475
53.6k
45.3k
31.6k
31.6k
43.2k
45.3k
49.9k
800
800
800
800
800
800
800
8V
22µF, 10V, X7R, 1206
100µF, 16V, 100mΩ, Electrolytic
12V
18V
24V
36V
22µF, 25V, X5R, 0805
68µF, 16V, 200mΩ, Electrolytic
3 × 2.2µF, 100V, 1206 22µF, 25V, X5R, 0805
47µF, 25V, 900mΩ, Electrolytic
100k/6.98k
100k/5.23k
100k/3.40k
100k/2.55k
3 × 2.2µF, 100V, 1206 22µF, 25V, X5R, 0805
33µF, 35V 300mΩ, Electrolytic
3 × 2.2µF, 100V, 1206 10µF, 50V, X5R, 1206
10µF, 50V 120mΩ, Electrolytic
12.5V to 58V 48V
3 × 2.2µF, 100V, 1206 10µF, 50V, X5R, 1206
10µF, 63V 120mΩ, Electrolytic
Notes: An input bulk capacitor is required. The output capacitance uses a combination of a ceramic and electrolytic in parallel. Other combinations of
resistor values for the RFB network are acceptable.
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LTM8056
APPLICATIONS INFORMATION
Table 2. Electrolytic Caps Used in LTM8056 Testing
DESCRIPTION
MANUFACTURER
AVX
PART NUMBER
100µF, 6V, 75mΩ, Tantalum C Case
TPSC107M006R0075
TPSY107M016R0100
TPSC686M016R0200
TAJD476M025R
100µF, 16V, 100mΩ, Tantalum Y Case
68µF, 16V, 200mΩ, Tantalum C Case
47µF, 25V, 900mΩ, Tantalum D Case
33µF, 35V, 300mΩ, Tantalum D Case
10µF, 50V, 120mΩ, Aluminum 6.3 × 6mm case
10µF, 63V, 120mΩ, Aluminum 6.3 × 5.8mm case
AVX
AVX
AVX
AVX
TPSD336M035R0300
50HVP10M
Suncon
Panasonic
EEHZA1J100P
Capacitor Selection Considerations
800kHz by tying a resistor from the RT pin to ground.
Table 3 provides a list of R resistor values and their re-
T
The C and C
capacitor values in Table 1 are the
IN
OUT
sultant frequencies.
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.
Table 3. Switching Frequency vs RT Value
FREQUENCY
100
R VALUE (kΩ)
T
453
147
84.5
59
200
300
400
500
45.3
36.5
29.4
24.9
600
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.
700
800
An external resistor within the range stated in Table 3
from RT to GND is required. Even when synchronizing to
an external clock. When synchronizing the switching of
the LTM8056 to an external signal source, the frequency
range is 200kHz to 700kHz.
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LTM8056. A
ceramic input capacitor combined with trace or cable
inductance forms a high Q (underdamped) tank circuit.
If the LTM8056 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.
Operating Frequency Trade-Offs
It is recommended that the user apply the optimal R
T
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
LTM8056isflexibleenoughtoaccommodateawiderange
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
Frequency Selection
The LTM8056 uses a constant frequency PWM architec-
ture that can be programmed to switch from 100kHz to
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LTM8056
APPLICATIONS INFORMATION
LTM8056 if the output is overloaded or short circuited.
A frequency that is too low can result in a final design
that has too much output ripple or too large of an output
capacitor or is even unstable.
2. Apply a FB resistor network to the individual slaves
so that the resulting output is higher than the desired
output voltage.
3. Apply the appropriate output current sense resistors
between V
and I . If the same value is used for the
OUT
OUT
Parallel Operation
master and slave units, they will share current equally.
Two or more LTM8056s may be combined to provide
increased output current by configuring them as a mas-
ter and a slave, as shown in Figure 1. Each LTM8056 is
4. Connect the master I to the slaves’ CTL pin
OUTMON
through a unity gain buffer. The unity gain buffer is
requiredtoisolatetheoutputimpedanceoftheLTM8056
from the integrated pull-up on the CTL pins.
equipped with an I
and a CTL pin. The I
OUTMON
OUTMON
pin’s0Vto1.2Vsignalreflectsthecurrentpassingthrough
the output sense resistor, while a voltage less than 1.2V
appliedtotheCTLpinwilllimitthecurrentpassingthrough
the output sense resistor. By applying the voltage of the
5. Tie the outputs together.
Note that this configuration does not require the inputs to
be tied together, making it simple to power a single heavy
load from multiple input sources. Ensure that each input
power source has sufficient voltage and current sourcing
capability to provide the necessary power. Please refer
master’s I
pin to the slave’s CTL pin, the two units
OUTMON
will source the same current to the load, assuming each
LTM8056 output current sense resistor is the same value.
to the Maximum Output Current vs V and Input Current
IN
vs Output Current curves in the Typical Performance
Characteristics section for guidance.
OUTPUT CURRENT
SENSE RESISTOR
MASTER
TO LOAD
V
OUT
OUT
I
ParalleledLTM8056sshouldnormallybeallowedtoswitch
in discontinuous mode enabled to prevent current from
flowing from the output of one unit into another; that is,
the MODE pin should be tied to LL. In some cases, operat-
ing the master in forced continuous (MODE open) and the
slaves in discontinuous mode (MODE = LL) is desirable.
If so, current from the output can flow into the master’s
input. Please refer to Input Precaution in this section for
a discussion of this behavior.
I
OUTMON
UNITY GAIN
BUFFER
OUTPUT CURRENT
SENSE RESISTOR
CTL
V
I
OUT
OUT
SLAVE
8056 F01
Minimum Input Voltage and RUN
Figure 1. Two or More LTM8056s May Be Connected in a
Master/Slave Configuration for Increased Output Current
The LTM8056 needs a minimum of 5V for proper opera-
tion, but system parameters may dictate that the device
operate only above some higher input voltage. For ex-
The design of a master-slave configuration is straight-
forward:
ample, a LTM8056 may be used to produce 12V , but
OUT
the input power source may not be budgeted to provide
1. Apply the FB resistor network to the master, choosing
the proper values for the desired output voltage. Sug-
gested values for popular output voltages are provided
in Table 1.
enough current if the input supply voltage is below 8V.
The RUN pin has a typical falling voltage threshold of
1.2V and a typical hysteresis of 25mV. In addition, the
pin sinks 3µA below the RUN threshold. Based upon the
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LTM8056
APPLICATIONS INFORMATION
above information and the circuit shown in Figure 2, the
V rising (turn-on) threshold is:
IN
when the voltage V -I
reaches 58mV. The current
OUT OUT
limit is:
R1+R2
R2
58mV
RSENSE
V = 3µA •R1 +1.225V
IOUT(LIM)
=
(
)
IN
and the V falling turn-off threshold is:
IN
where R
is the value of the sense resistor in ohms.
SENSE
R1+R2
R2
Most applications should use an output sense resistor as
shown in Figure 3, if practical. The internal buck-boost
power stage is current limited, but is nonetheless capable
of delivering large amounts of current in an overload
condition, especially when the output voltage is much
lower than the input and the power stage is operating as
a buck converter.
V =1.2
IN
LTM8056
V
IN
R1
R2
RUN
8056 F02
LTM8056
R
SENSE
V
OUT
Figure 2. This Simple Resistor Network Sets the Minimum
Operating Input Voltage Threshold with Hysteresis
LOAD
I
OUT
8056 F03
Minimum Input Voltage and SV
IN
Figure 3. Set The LTM8056 Output Current Limit with an
External Sense Resistor
The minimum input voltage of the LTM8056 is 5V, but this
is only if V and SV are tied to the same voltage source.
IN
IN
If SV is powered from a power source at or above 5VDC,
IN
When the voltage across the output sense resistor falls
to about 1/10th of full scale, the LL pin pulls low. If there
V can be allowed to fall below 5V and the LTM8056 can
IN
still operate properly. Some examples of this are provided
is no output sense resistor, and I
is tied to V , LL
OUT
OUT
in the Typical Applications section.
will be active low. Applying an output sense resistor and
tying the LL and MODE pins together can improve perfor-
mance—see Switching Mode in this section.
Soft-Start
Soft-startreducestheinputpowersources’surgecurrents
bygraduallyincreasingthecontroller’scurrent.Asindicated
in the Block Diagram, the LTM8056 has an internal soft-
start RC network. Depending upon the load and operating
conditions, the internal network may be sufficient for the
application. To increase the soft-start time, simply add a
capacitor from SS to GND.
In high step-down voltage regulator applications, the
internal current limit can be quite high to allow proper
operation. This can potentially damage the LTM8056
in overload or short-circuit conditions. Apply an output
current sense resistor to set an appropriate current limit
to protect the LTM8056 against these fault conditions.
Output Current Limit Control (CTL)
Output Current Limit (I
)
OUT
Use the CTL input to reduce the output current limit from
thevaluesetbytheexternalsenseresistorappliedbetween
TheLTM8056featuresanaccurateaverageoutputcurrent
limitsetbyanexternalsenseresistorplacedbetweenV
as shown in Figure 3. V
connect to a differential amplifier that limits the current
OUT
internally
V
and I . The typical control range is between 0V
OUT
OUT
and I
and I
OUT
OUT
OUT
and 1.2V. The CTL pin does not directly affect the input
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LTM8056
APPLICATIONS INFORMATION
current limit. If this function is not used, leave CTL open.
Drive CTL to less than about 50mV to stop switching. The
CTL pin has an internal pull-up resistor to 2V.
Synchronization
TheLTM8056switchingfrequencycanbesynchronizedto
an external clock using the SYNC pin. Driving SYNC with
a 50% duty cycle waveform is a good choice, otherwise
maintainthedutycyclebetweenabout10%and90%.When
synchronizing, a valid resistor value (that is, a value that
results in a free-running frequency of 100kHz to 800kHz)
must be connected from RT to GND.
Input Current Limit (I )
IN
SomeapplicationsrequirethattheLTM8056drawnomore
than some predetermined current from the power source.
Current limited power sources and power sharing are two
examples.TheLTM8056featuresanaccurateinputcurrent
While an RT resistor is required for proper operation, the
value of this resistor is independent of the frequency of
the externally applied SYNC signal. Be aware, however,
that the LTM8056 will switch at the frequency prescribed
by the RT value if the SYNC signal terminates, so choose
an appropriate resistor value.
limit set by an external sense resistor placed between I
IN
andV asshowninFigure4. V andI internallyconnect
IN
IN
IN
to a differential amplifier that limits the current when the
voltage I -V reaches 50mV. The current limit is:
IN IN
50mV
RSENSE
I
=
IN(LIM)
CLKOUT
where R
is the value of the sense resistor in ohms.
SENSE
The CLKOUT signal reflects the internal switching clock of
theLTM8056.Itisphaseshiftedbyapproximately180°with
respecttotheleadingedgeoftheinternalclock.IfCLKOUT
is connected to the SYNC input of another LTM8056, the
two devices will switch about 180° out of phase.
Ifinputcurrentlimitingisnotrequired,simplytieI toV .
IN
IN
LTM8056
R
SENSE
POWER
SOURCE
V
IN
I
IN
Input Precaution
8056 F04
In applications where the output voltage is deliberately
pulled up above the set regulation voltage or the FB pin is
abruptlydriventoanewvoltage,theLTM8056mayattempt
to regulate the voltage by removing energy from the load
for a short period of time after the output is pulled up.
SincetheLTM8056isasynchronousswitchingconverter,
itdeliversthisenergytotheinput. Ifthereisnothingonthe
LTM8056 input to consume this energy, the input voltage
may rise. If the input voltage rises without intervention, it
may rise above the absolute maximum rating, damaging
the part. Carefully examine the input voltage behavior to
see if the application causes it to rise.
Figure 4. Set the LTM8056 Input Current Limit with an External
Sense Resistor
Input Current Monitor (I
)
INMON
The I
pin produces a voltage equal to approximately
INMON
20 times the voltage of I -V . Since the LTM8056 input
IN IN
current limit engages when I -V = 50mV, I
be 1V at maximum input current.
will
IN IN
INMON
Output Current Monitor (I
)
OUTMON
The I
pin produces a voltage proportional to the
OUTMON
In many cases, the system load on the LTM8056 input
bus will be sufficient to absorb the energy delivered by the
μModule regulator. The power required by other devices
will consume more than enough to make up for what
voltage of V -I . Since the LTM8056 output current
OUT OUT
limit engages when V -I
1.2V at maximum output current.
= 58mV, I
will be
OUT OUT
OUTMON
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LTM8056
APPLICATIONS INFORMATION
LOAD
the LTM8056 delivers. In cases where the LTM8056 is
the largest or only power converter, this may not be true
and some means may need to be devised to prevent the
LTM8056’s input from rising too high. Figure 5a shows a
passive crowbar circuit that will dissipate energy during
momentaryinputovervoltageconditions.Thebreak-down
voltage of the Zener diode is chosen in conjunction with
the resistor R to set the circuit’s trip point. The trip point
CURRENT
V
V
OUT
IN
LTM8056
GND
RUN
SOURCING
LOAD
10µF
–
+
EXTERNAL
REFERENCE
VOLTAGE
is typically set well above the maximum V voltage under
IN
8056 F05b
normal operating conditions. This circuit does not have
a precision threshold, and is subject to both part-to-part
and temperature variations, so it is most suitable for ap-
plications where the maximum input voltage is much less
Figure 5b. This Comparator Circuit Turns Off the LTM8056 if
the Input Rises Above a Predetermined Threshold. When the
LTM8056 Turns Off, the Energy Stored in the Internal Inductor
Will Raise VIN a Small Amount Above the Threshold
than the 60V absolute maximum. As stated earlier, this
IN
type of circuit is best suited for momentary overvoltages.
Switching Mode
Figure 5a is a crowbar circuit, which attempts to prevent
theinputvoltagefromrisingabovesomelevelbydumping
energy to GND through a power device. In some cases,
it is possible to simply turn off the LTM8056 when the
input voltage exceeds some threshold. An example of this
circuit is shown in Figure 5b. When the power source on
TheMODEpinallowstheusertoselecteitherdiscontinuous
mode or forced continuous mode switching operation. In
forcedcontinuousmode,theLTM8056willnotskipcycles,
evenwhentheinternalinductorcurrentfallstozerooreven
reverses direction. This has the advantage of operating at
thesamefixedfrequencyforallloadconditions, whichcan
be useful when designing to EMI or output noise speci-
fications. Forced continuous mode, however, uses more
current at light loads, and allows current to flow from the
load back into the input if the output is raised above the
regulation point. This reverse current can raise the input
voltage and be hazardous if the input is allowed to rise
uncontrollably. Please refer to Input Precautions in this
section for a discussion of this behavior.
the output drives V above a predetermined threshold,
IN
the comparator pulls down on the RUN pin and stops
switching in the LTM8056. When this happens, the input
capacitance needs to absorb the energy stored within the
LTM8056’s internal inductor, resulting in an additional
voltage rise. This voltage rise depends upon the input
capacitor size and how much current is flowing from the
LTM8056 output to input.
Forced continuous operation may provide improved
output regulation when the LTM8056 transitions from
buck, buck-boost or boost operating modes, especially at
lighter loads. In such a case, it can be desirable to oper-
ate in forced continuous mode except when the internal
inductor current is about to reverse. If so, apply a current
LOAD
CURRENT
V
V
OUT
IN
ZENER
DIODE
LTM8056
GND
SOURCING
LOAD
Q
R
sense resistor between V
and I
and tie the LL and
OUT
OUT
8056 F05a
MODE pins together. The LL pin is low when the current
through the output sense resistor is about one-tenth the
full-scale maximum. When the output current falls to this
level, the LL pin will pull the MODE pin down, putting the
LTM8056 in discontinuous mode, preventing reverse cur-
rent from flowing from the output to the input. In the case
Figure 5a. The MOSFET Q Dissipates Momentary Energy to
GND. The Zener Diode and Resistor Are Chosen to Ensure That
the MOSFET Turns On Above the Maximum VIN Voltage Under
Normal Operation
8056fa
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LTM8056
APPLICATIONS INFORMATION
where MODE and LL are tied together, a small capacitor
(~0.1µF) from these pins to GND may improve the light
load transient response by delaying the transition from
the discontinuous to forced continuous switching modes.
MODE may be tied to GND for the purpose of blocking
reverse current if no output current sense resistor is used.
5. Minimizethetraceresistancebetweentheoptionalinput
current sense resistor (R ) and V . Minimize the loop
IN
IN
area of the I trace and the trace from V to R .
IN
IN
IN
6. Place the C and C
capacitors such that their
OUT
IN
ground current flow directly adjacent or underneath
the LTM8056.
7. 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 LTM8056.
FB Resistor Divider and Load Regulation
The LTM8056 regulates its FB pin to 1.2V, using a resistor
divider to sense the output voltage. The location at which
the output voltage is sensed affects the load regulation.
8. Use vias to connect the GND copper area to the board’s
internal ground planes. Liberally distribute these GND
vias to provide both a good ground connection and
thermal path to the internal planes of the printed circuit
board. Pay attention to the location and density of the
thermal vias in Figure 6. The LTM8056 can benefit from
theheatsinkingaffordedbyviasthatconnecttointernal
GND planes at these locations, due to their proximity
to internal power handling components. The optimum
number of thermal vias depends upon the printed
circuit board design. For example, a board might use
very small via holes. It should employ more thermal
vias than a board that uses larger holes.
If there is a current sense resistor between V
and
OUT
I
, and the output is sensed at V , the voltage at the
OUT
OUT
load will drop by the value of the current sense resistor
multiplied by the output current. If the output voltage can
be sensed at I , the load regulation may be improved.
OUT
PCB Layout
Most of the headaches associated with PCB layout have
been alleviated or even eliminated by the high level of
integration of the LTM8056. The LTM8056 is neverthe-
less a switching power supply, and care must be taken to
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 6
for a suggested layout. Ensure that the grounding and
heat sinking are acceptable.
Hot-Plugging Safely
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypass capacitor of the LTM8056. However, these capaci-
tors can cause problems if the LTM8056 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-
A few rules to keep in mind are:
1. Place the R and R resistors as close as possible to
FB
T
their respective pins.
2. Place the C capacitor as close as possible to the V
IN
IN
and GND connection of the LTM8056.
age at the V pin of the LTM8056 can ring to more than
3. Place the C
capacitor as close as possible to the
IN
OUT
twice the nominal input voltage, possibly exceeding the
V
and GND connection of the LTM8056.
OUT
LTM8056’sratinganddamagingthepart.Iftheinputsupply
4. Minimize the trace resistance between the optional
outputcurrentsenseresistor,R ,andV . Minimize
OUT
OUT
the loop area of the I
trace and the trace from V
OUT
OUT
to R
.
OUT
8056fa
17
For more information www.linear.com/LTM8056
LTM8056
APPLICATIONS INFORMATION
ispoorlycontrolledortheLTM8056ishot-pluggedintoan
energized supply, the input network should be designed
to prevent this overshoot. This can be accomplished by
Thermal Considerations
The LTM8056 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
installing a small resistor in series with V , but the most
IN
popular method of controlling input voltage overshoot is
to add an electrolytic bulk capacitor to the V net. This
IN
capacitor’s relatively high equivalent series resistance
damps the circuit and eliminates the voltage overshoot.
The extra capacitor improves low frequency ripple filter-
ing and can slightly improve the efficiency of the circuit,
thoughitislikelytobethelargestcomponentinthecircuit.
2
generated by a LTM8056 mounted to a 58cm 4-layer FR4
printedcircuitboard. Boardsofothersizesandlayercount
C
IN
SV
IN
GND
V
IN
R
IN
GND/THERMAL VIAS
INPUT
SENSE
I
IN
C
OUT
INPUT
RUN
V
MODE SYNC
RT FB
OUT
I
OUT
LL
R
OUT
OUTPUT
SENSE
GND
I
OUT
TO V
OUT
8056 F06
Figure 6. Layout Showing Suggested External Components,
GND Plane and Thermal Vias
8056fa
18
For more information www.linear.com/LTM8056
LTM8056
APPLICATIONS INFORMATION
can exhibit different thermal behavior, so it is incumbent
upon the user to verify proper operation over the intended
system’sline,loadandenvironmentaloperatingconditions.
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.
ThethermalresistancenumberslistedinthePinConfigura-
tion of the data sheet are based on modeling the µModule
package mounted on a test board specified per JESD 51-9
(TestBoardsforAreaArraySurfaceMountPackageThermal
Measurements). Thethermalcoefficientsprovidedonthis
page are based on JESD 51-12 (Guidelines for Reporting
and Using Electronic Package Thermal Information).
θ
isdeterminedwithnearlyallofthecomponentpower
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-
Forincreasedaccuracyandfidelitytotheactualapplication,
many designers use FEA to predict thermal performance.
To that end, the Pin Configuration of the data sheet typi-
cally gives four thermal coefficients:
tion to the top of the part. As in the case of θ
, this
JCbottom
θ
JA
– Thermal resistance from junction to ambient.
value may be useful for comparing packages but the test
conditions don’t generally match the user’s application.
θ
–Thermalresistancefromjunctiontothebottom
JCbottom
of the product case.
θ
JB
is the junction-to-board thermal resistance where
almost all of the heat flows through the bottom of the
µModule converter and into the board, and is really the
θ
– Thermal resistance from junction to top of the
JCtop
product case.
sum of the θ
and the thermal resistance of the
JCbottom
θ
JB
– Thermal resistance from junction to the printed
bottom of the part through the solder joints and through a
portion of the board. The board temperature is measured
a specified distance from the package, using a 2-sided,
2-layer board. This board is described in JESD 51-9.
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:
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 versus load graphs
givenintheproduct’sdatasheet.Theonlyappropriateway
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 natural convection junction-to-ambient air
JA
thermal resistance measured in a one cubic foot sealed
enclosure. This environment is sometimes referred to as
“still air” although natural convection causes the air to
move. 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.
8056fa
19
For more information www.linear.com/LTM8056
LTM8056
APPLICATIONS INFORMATION
A graphical representation of these thermal resistances
is given in Figure 7.
LTM8056. The bulk of the heat flow out of the LTM8056
is through the bottom of the μModule converter and the
BGA 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.
The blue resistances are contained within the µModule
converter, and the green are outside.
The die temperature of the LTM8056 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
JUNCTION-TO-AMBIENT RESISTANCE (JESD 51-9 DEFINED BOARD)
JUNCTION-TO-CASE (TOP)
RESISTANCE
CASE (TOP)-TO-AMBIENT
RESISTANCE
JUNCTION-TO-BOARD RESISTANCE
JUNCTION
AMBIENT
JUNCTION-TO-CASE
(BOTTOM) RESISTANCE
CASE (BOTTOM)-TO-BOARD
BOARD-TO-AMBIENT
RESISTANCE
RESISTANCE
8056 F07
µMODULE CONVERTER
Figure 7
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20
For more information www.linear.com/LTM8056
LTM8056
TYPICAL APPLICATIONS
18VOUT Fan Power from 3VIN to 58VIN with Analog
Maximum Output Current
vs CTL Voltage 12VIN
Current Control and 2A Input Current Limiting
1.2
1.0
0.8
0.6
0.4
0.2
0
1µF
100V
SV
0.022Ω
0.05Ω
IN
V
V
LTM8056
V
IN
OUT
V
IN
OUT
18V MAX
3V TO 58V
I
I
IN
OUT
FAN
100k
2.2µF
100V
×3
RUN
COMP
SS
+
47µF
25V
CLKOUT
I
INMON
22µF
25V
SYNC
CTL
RT
I
OUTMON
FB
31.6k
6.98k
0
0.2
0.4
0.6
0.8
1
1.2
MODE LL
GND
8056 TA02a
CTL VOLTAGE (V)
8056 TA02b
f
= 650kHz
SW
DAC
FAN CONTROL
24VOUT from 9VIN to 58VIN with 1.1A Accurate Current Limit
Output Voltage vs Output Current
25
0.05Ω
V
V
LTM8056
V
IN
OUT
V
OUT
24V
IN
20
15
10
5
9V TO 58V
SV
I
IN
OUT
I
IN
100k
2.2µF
100V
×3
RUN
CTL
SS
SYNC
COMP
RT
+
33µF
35V
CLKOUT
I
INMON
22µF
25V
I
OUTMON
FB
12V
IN
43.2k
5.23k
24V
36V
48V
IN
IN
IN
MODE LL
GND
8056 TA03a
0
f
= 525kHz
SW
0
0.5
1
1.5
OUTPUT CURRENT (A)
8056 TA03b
8056fa
21
For more information www.linear.com/LTM8056
LTM8056
TYPICAL APPLICATIONS
Output Voltage vs Output Current
20
18VOUT from 18VIN to 58VIN with 2.5A Accurate Current Limit
and Output Current Monitor
18
16
14
12
10
8
0.022Ω
V
V
LTM8056
V
IN
OUT
V
IN
18V TO 58V
OUT
18V
SV
I
IN
OUT
I
IN
100k
+
2.2µF
100V
×3
47µF
25V
RUN
CTL
SS
SYNC
COMP
RT
22µF
25V
OUTPUT
CURRENT
MONITOR
6
CLKOUT
4
I
24V
36V
48V
INMON
IN
IN
IN
I
2
OUTMON
FB
31.6k
MODE LL
GND
0
6.98k
8056 TA04a
0
0.5
1
1.5
2
2.5
3
OUTPUT CURRENT (A)
8056 TA04b
f
= 650kHz
SW
NOTE: LINES ARE SUPERIMPOSED
Two LTM8056s Paralleled to Get More Output Current. The Two µModules Are
Synchronized and Switching 180° Out Of Phase
0.015Ω
V
V
LTM8056
V
IN
OUT
V
OUT
18V
IN
7V TO 58V
SV
I
IN
OUT
Output Current per Channel vs
Total Output Current
I
IN
2.2µF
100V
×4
RUN
CTL
SS
SYNC
COMP
RT
+
4
3
2
1
0
22µF
25V
47µF
25V
MASTER
SLAVE
1µF
I
INMON
I
OUTMON
30.9k
100k
FB
CLKOUT
6.98k
MODE LL
GND
LT6015
51Ω
f
= 680kHz
SW
1µF
0.015Ω
0
2
4
6
8
V
V
LTM8056
IN
OUT
TOTAL OUTPUT CURRENT (A)
SV
IN
I
8056 TA05b
OUT
NOTE: LINES ARE SUPERIMPOSED
I
IN
2.2µF
100V
×4
RUN
COMP
SS
+
CTL
CLKOUT
22µF
25V
47µF
25V
100k
SYNC
I
INMON
I
OUTMON
FB
30.9k
6.34k
RT
GND
MODE LL
8056 TA05a
8056fa
22
For more information www.linear.com/LTM8056
LTM8056
TYPICAL APPLICATIONS
Two LTM8056s Powered from Different Input Sources to Run a Single Load. Each LTM8056 Draws No More Than 1.1A from Its
Respective Power Sources, and Are Synchronized 180° Out Of Phase with Each Other
0.045Ω
V
V
LTM8056
SUPPLY 1
IN
OUT
V
OUT
6V TO 58V
18V
IN
SV
I
IN
OUT
22µF
25V
I
IN
2.2µF
100V
×3
RUN
CTL
SS
+
47µF
35V
SYNC
COMP
RT
I
INMON
I
OUTMON
FB
31.6k
100k
CLKOUT
MODE LL
GND
0.045Ω
V
V
LTM8056
IN
OUT
SUPPLY 2
6V TO 58V
IN
SV
I
OUT
IN
I
IN
2.2µF
100V
×3
22µF
25V
RUN
CTL
SS
CLKOUT
SYNC
COMP
RT
I
INMON
I
OUTMON
FB
31.6k
6.98k
GND
MODE LL
8056 TA06a
f
= 650kHz
SW
Input Current per Channel vs
Total Output Current
1.2
1.0
0.8
0.6
0.4
0.2
0
CHANNEL 1
CHANNEL 2
0
1
2
3
4
5
6
7
OUTPUT CURRENT (A)
8056 TA06b
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23
For more information www.linear.com/LTM8056
LTM8056
PACKAGE DESCRIPTION
Table 4. LTM8056 Pin Assignment (Arranged by Pin Number)
PIN ID
A1
FUNCTION
PIN ID
B1
FUNCTION
PIN ID
C1
FUNCTION
PIN ID
D1
FUNCTION
PIN ID
E1
FUNCTION
GND
PIN ID
F1
FUNCTION
LL
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
V
I
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
OUT
A2
B2
C2
D2
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
E2
GND
F2
GND
GND
GND
GND
GND
GND
GND
GND
A3
B3
C3
D3
E3
GND
F3
A4
B4
C4
D4
E4
GND
F4
A5
B5
C5
D5
E5
GND
F5
A6
B6
C6
D6
E6
GND
F6
A7
GND
GND
GND
GND
GND
B7
GND
GND
GND
GND
GND
C7
GND
GND
GND
GND
GND
D7
E7
GND
F7
A8
B8
C8
D8
E8
GND
F8
A9
B9
C9
D9
E9
GND
F9
A10
A11
B10
B11
C10
C11
D10
D11
E10
E11
GND
F10
F11
SV
IN
SV
IN
GND
PIN ID
G1
FUNCTION
CLKOUT
MODE
GND
PIN ID
H1
FUNCTION
RT
PIN ID
J1
FUNCTION
FB
PIN ID
K1
FUNCTION
SS
PIN ID
L1
FUNCTION
GND
G2
H2
SYNC
GND
J2
COMP
GND
K2
CTL
L2
I
OUTMON
G3
H3
J3
K3
GND
GND
GND
GND
GND
GND
GND
L3
I
INMON
G4
GND
H4
GND
J4
GND
K4
L4
RUN
G5
GND
H5
GND
J5
GND
K5
L5
GND
GND
GND
GND
G6
GND
H6
GND
J6
GND
K6
L6
G7
GND
H7
GND
J7
GND
K7
L7
G8
GND
H8
GND
J8
GND
K8
L8
G9
GND
H9
GND
J9
GND
K9
L9
I
IN
G10
G11
V
V
H10
H11
V
V
J10
J11
V
IN
V
IN
K10
K11
V
IN
V
IN
L10
L11
V
IN
V
IN
IN
IN
IN
IN
8056fa
24
For more information www.linear.com/LTM8056
LTM8056
PACKAGE PHOTO
8056fa
25
For more information www.linear.com/LTM8056
LTM8056
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/product/LTM8056#packaging for the most recent package drawings.
Z
/ / b b b
Z
6 . 3 5 0
5 . 0 8 0
3 . 8 1 0
2 . 5 4 0
1 . 2 7 0
0 . 3 1 7 5
0 . 3 1 7
1 . 2 7 0
0 . 0 0 0
2 . 5 4 0
3 . 8 1 0
5 . 0 8 0
6 . 3 5 0
8056fa
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For more information www.linear.com/LTM8056
LTM8056
REVISION HISTORY
REV
DATE
DESCRIPTION
PAGE NUMBER
A
11/16 Added text to I
(Pin L2)
8
1
OUTMON
Added Buck-Boost Selection Table
8056fa
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-
tion that the interconnection of its circuits as described herein will not infringe on existing patent rights.
27
LTM8056
TYPICAL APPLICATION
14.4V, 3A Lead-Acid Battery Charger Input Current Limited to 2A
Maximum Input and Output Current
vs Input Voltage
3.5
3.5
3.0
2.5
2.0
1µF
100V
3.0
2.5
2.0
OUTPUT
SV
0.018Ω
0.022Ω
IN
V
V
LTM8056
V
IN
OUT
V
IN
3V TO 58V
OUT
14.4V
I
I
IN
OUT
+
100k
47µF
25V
1.5
1.0
0.5
0
1.5
1.0
0.5
0
2.2µF
100V
×3
RUN
CTL
SS
SYNC
COMP
RT
INPUT
CLKOUT
22µF
25V
I
INMON
I
OUTMON
FB
31.6k
9.09k
0
20
40
60
MODE LL GND
8056 TA07a
INPUT VOLTAGE (V)
8056 TA07b
f
= 650kHz
SW
DESIGN RESOURCES
SUBJECT
DESCRIPTION
µModule Design and Manufacturing Resources
Design:
Manufacturing:
• Quick Start Guide/Demo Manual
• Selector Guides
• Demo Boards and Gerber Files
• Free Simulation Tools
• PCB Design, Assembly and Manufacturing Guidelines
• Package and Board Level Reliability
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.
RELATED PARTS
PART NUMBER DESCRIPTION
COMMENTS
LTM8055
LTM4605
Higher Power, Pin Compatible
8.5A, 5V ≤ V ≤ 36V
IN
Higher Power Buck-Boost (Up to 60W)
External Inductor, Synchronous Switching Buck-Boost; Up to 36V , 0.8V ≤ V
≤ 16V
IN
OUT
LTM4607
LTM4609
Higher Power Buck-Boost (Up to 60W)
Higher Power Buck-Boost (Up to 60W)
External Inductor, Synchronous Switching Buck-Boost; Up to 36V , 0.8V ≤ V
IN
OUT
OUT
≤ 24V
External Inductor, Synchronous Switching Buck-Boost; Up to 36V , 0.8V ≤ V
IN
≤ 34V
LTM8045
LTM8046
Smaller, Lower Power
Isolated, Lower Power
SEPIC and Inverting; 700mA, 6.25mm × 11.25mm × 4.92mm BGA
Flyback Topology, 550mA (5V , 24V ), UL60950, 2kVAC
OUT
IN
8056fa
LT 1116 REV A • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
28
●
●
(408)432-1900 FAX: (408) 434-0507 www.linear.com/LTM8056
LINEAR TECHNOLOGY CORPORATION 2015
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