LTM8027EV [Linear]
60V, 4A DC/DC Module Regulator; 60V , 4A DC / DC模块稳压器型号: | LTM8027EV |
厂家: | Linear |
描述: | 60V, 4A DC/DC Module Regulator |
文件: | 总20页 (文件大小:246K) |
中文: | 中文翻译 | 下载: | 下载PDF数据表文档文件 |
LTM8027
60V, 4A DC/DC µModule
Regulator
FEATURES
DESCRIPTION
The LTM®8027 is a complete 4A, DC/DC step-down power
supply. Included in the package are the switching control-
ler, power switches, inductor and all support components.
Operatingoveraninputvoltagerangeof4.5Vto60V(7.5V
minimum voltage to start), the LTM8027 supports output
voltages up to 24V, and a switching frequency range of
100kHz to 500kHz, each set by a single resistor. Only the
bulk input and output filter capacitors are needed to finish
the design.
n
Complete Switch Mode Power Supply
n
Wide Input Voltage Range: 4.5V to 60V
(7.5V Minimum Voltage to Start)
Wide Output Voltage Range: 2.5V to 24V
n
(See Table 2)
4A Output Current
Programmable Soft-Start
10μA Shutdown Supply Current
n
n
n
n
Selectable Switching Frequency Current Mode
Control
Up to 95% Efficiency
The low profile package (4.32mm) enables utilization of
unused space on the bottom of PC boards for high den-
sity point of load regulation. A built-in soft-start timer is
adjustable with a small capacitor.
n
n
Pb-Free (e4) RoHS Compliant Package with
Gold Pad Finish
n
Tiny, Low Profile (15mm × 15mm × 4.32mm)
TheLTM8027ispackagedinathermallyenhanced,compact
(15mm × 15mm) and low profile (4.32mm) over-molded
land grid array (LGA) package suitable for automated
assembly by standard surface mount equipment. The
LTM8027 is Pb-free and RoHS compliant.
Surface Mount LGA Package
APPLICATIONS
n
12V and 42V Automotive and Heavy Equipment
n
48V Telecom Power Supplies
L, LT, LTC, LTM, μModule, Linear Technology and the Linear logo are registered trademarks of
Linear Technology Corporation. All other trademarks are the property of their respective owners.
n
Avionics and Industrial Control Systems
Distributed Power Converters
n
TYPICAL APPLICATION
48W, 16VIN to 60VIN DC/DC μModule® Regulator
Efficiency vs Load
V
12V
4A
100
OUT
V
IN
24V
IN
V
V
OUT
IN
16V TO 60V
90
80
70
60
50
40
30
20
10
0
4.7μF
s2
1M
LTM8027
RUN
SS
BIAS1
BIAS2
AUX
22μF
s4
SYNC
RT
ADJ
GND
48.7k
56.2k
3845 TA01a
0
1
2
3
4
LOAD (A)
8027 TA01b
8027f
1
LTM8027
ABSOLUTE MAXIMUM RATINGS
PIN CONFIGURATION
(Note 1)
TOP VIEW
V Voltage................................................................65V
IN
BIAS1, BIAS2 ............................................................15V
11
10
9
V
OUT
SYNC, ADJ, R , RUN, SS Voltages..............................5V
BANK 1
T
Current Into RUN Pin (Note 2) .................................1mA
8
V
, AUX.................................................................25V
AUX
7
GND
BANK 2
OUT
BIAS1
SS
RUN
BIAS2
ADJ
6
5
4
3
2
1
Current Out of AUX ............................................. 200mA
Internal Operating Temperature
(Note 3).................................................. –40°C to 125°C
Maximum Soldering Temperature......................... 245°C
Storage Temperature Range .................. –55°C to 125°C
V
IN
BANK 3
A
B
C
D
E
F G H J K L
RT
SYNC
LGA PACKAGE
113-LEAD (15mm s 15mm s 4.32mm)
= 125°C, θ = 12.2°C/W, θ = 9.3°C/W,
T
JMAX
θ
JA
JC(TOP)
= 7.54°C/W
= 3.6°C/W, θ
JC(BOTTOM)
JBOARD
θ VALUES DETERMINED PER JESD 51-9
WEIGHT = 2.6 GRAMS
ORDER INFORMATION
LEAD FREE FINISH
LTM8027EV#PBF
LTM8027IV#PBF
LTM8027MPV#PBF
TRAY
PART MARKING
PACKAGE DESCRIPTION
INTERNAL TEMPERATURE RANGE
–40°C to 125°C
LTM8027EV#PBF
LTM8027IV#PBF
LTM8027MPV#PBF
LTM8027V
113-Lead (15mm × 15mm × 4.32mm) LGA
113-Lead (15mm × 15mm × 4.32mm) LGA
113-Lead (15mm × 15mm × 4.32mm) LGA
LTM8027V
–40°C to 125°C
LTM8027V
–55°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges.
Consult LTC Marketing for information on non-standard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
This product is only offered in trays. For more information go to: http://linear.com/packaging/
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 20V, BIAS1 = BIAS2 = 10V, RUN = 2V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
l
V
V
Input DC Voltage
(Note 5)
4.5
60
V
V
IN
Maximum Output DC Voltage
Output DC Current
Minimum Start Voltage
Line Regulation
0 < I
≤ 4A, V = 48V
24
OUT
OUT
OUT
IN
I
V
IN
≤ 60V, V
= 12V, (Note 4)
OUT
0
4
A
V
7.5
V
IN(START)
V
V
= 12V, 15V< V < 60V, I
= 4A
≤ 4A
0.2
0.2
4.6
%
%
V
ΔV /ΔV
OUT
IN
LOAD
OUT
IN
Load Regulation
= 12V, V = 24V, 0A < I
ΔV /ΔI
OUT
IN
LOAD
OUT LOAD
UVLO(RISING)
V
V
Input Undervoltage Lockout Threshold
(Rising)
(Note 5)
Input Undervoltage Lockout Threshold
(Falling)
(Note 5)
3.7
V
UVLO(FALLING)
8027f
2
LTM8027
ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 20V, BIAS1 = BIAS2 = 10V, RUN = 2V, unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
ADJ
ADJ Voltage
1.224
1.215
1.238
1.245
V
V
l
IQ
Quiescent Current into IN
V
V
= V , V = 12VDC, No Load
AUX OUT
39
9
mA
μA
VIN
BIAS1
BIAS1
BIAS
RUN
= 0V
V
BIAS1 Undervoltage Lockout (Rising)
BIAS1 Undervoltage Lockout (Falling)
6.5
6
V
V
I
Current into BIAS1
No Load
RUN = 0V
25
25
mA
μA
V
Minimum BIAS2 Voltage
Current Into BIAS2
6
1
V
μA
V
BIAS2
I
BIAS2
V
Minimum Voltage to Overdrive INTV
Regulator
8.5
BIAS(MINOV)
CC
R
Internal Feedback Resistor
RUN Enable Voltage (Rising)
RUN Enable Voltage (Falling)
Switching Frequency
499
1.4
1.2
kΩ
V
FB
V
V
RUN(RISING)
RUN(FALLING)
V
f
SW
R = 187kΩ
T
100
500
kHz
kHz
T
R = 23.7kΩ
R
SYNC Input Resistance
SYNC Voltage Threshold
Soft-Start Charging Current
40
kΩ
V
SYNC
l
V
f
= 350kHz
2.3
SYNC(TH)
SYNC
I
2
μA
SS
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.
–40°C to 125°C internal operating temperature range. The LTM8027MP
is guaranteed to meet specifications over the full –55°C to 125°C
internal operating 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 RUN pin is internally clamped to 5V
Note 3: The LTM8027E is guaranteed to meet performance specifications
from 0°C to 125°C internal operating temperature. 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 LTM8027I is guaranteed to meet specifications over the full
Note 4: The maximum continuous output current may be derated by the
LTM8027 junction temperature.
Note 5: V voltages below the start-up threshold (7.5V) are only
IN
supported when the V is externally driven above 6.5V.
CC
8027f
3
LTM8027
TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted)
Efficiency vs Load, VOUT = 2.5V
Efficiency vs Load, VOUT = 3.3V
Efficiency vs Load, VOUT = 5V
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
5V
IN
12V
IN
IN
IN
IN
IN
12V
24V
36V
48V
60V
IN
IN
IN
IN
IN
5V
24V
36V
48V
60V
IN
12V
24V
36V
IN
IN
IN
0
1
2
3
4
0
1
2
3
4
0
1
2
3
4
LOAD (A)
LOAD (A)
LOAD (A)
8027 G01
8027 G02
8027 G03
Efficiency vs Load, VOUT = 8V
Efficiency vs Load, VOUT = 12V
Efficiency vs Load, VOUT = 15V
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
12V
IN
IN
IN
IN
IN
24V
24V
24V
36V
48V
60V
IN
IN
IN
IN
IN
IN
IN
IN
36V
48V
60V
36V
48V
60V
0
1
2
3
4
0
1
2
3
4
0
1
2
3
4
LOAD (A)
LOAD (A)
LOAD (A)
8027 G04
8027 G05
8027 G06
Input Current
vs VIN Output Shorted
Efficiency vs Load, VOUT = 18V
Efficiency vs Load, VOUT = 24V
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
3000
2500
2000
1500
1000
500
24V
IN
IN
IN
IN
36V
48V
60V
36V
48V
60V
IN
IN
IN
0
0
1
2
3
4
0
1
2
3
4
0
20
30
(V)
40
50
60
10
LOAD (A)
LOAD (A)
V
IN
8027 G07
8027 G08
8027 G09
8027f
4
LTM8027
TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted)
Input Current vs Load,
VOUT = 2.5V
Input Current vs Load,
VOUT = 3.3V
Input Current vs Load,
VOUT = 5V
3500
3000
2500
2000
1800
1600
1400
1200
1000
800
3000
2500
5V
IN
12V
5V
IN
IN
12V
IN
24V
36V
48V
60V
12V
IN
IN
IN
IN
IN
24V
IN
24V
IN
36V
IN
36V
IN
48V
60V
IN
IN
2000
1500
2000
1500
1000
500
0
1000
500
0
600
400
200
0
1
2
4
0
3
3
3
0
1
2
3
3
3
4
0
1
2
3
4
LOAD (A)
LOAD (A)
LOAD (A)
8027 G10
8027 G11
8027 G43
Input Current vs Load,
VOUT = 8V
Input Current vs Load,
VOUT = 12V
Input Current vs Load,
VOUT = 15V
3500
3000
2500
2500
2000
1500
1000
500
3000
2500
24V
IN
12V
IN
24V
IN
36V
IN
24V
IN
36V
IN
48V
IN
60V
IN
36V
IN
48V
IN
60V
IN
48V
60V
IN
IN
2000
1500
2000
1500
1000
500
0
1000
500
0
0
1
2
4
1
2
0
3
0
4
0
1
2
4
LOAD (A)
LOAD (A)
LOAD (A)
8027 G12
8027 G13
8027 G14
Input Current vs Load,
VOUT = 18V
Input Current vs Load,
VOUT = 24V
Bias Current vs Load,
VOUT = 2.5V
3500
3000
2500
2000
1500
1000
500
3500
3000
2500
2000
1500
1000
500
15.50
15.00
14.50
14.00
13.50
13.00
12.50
12.00
24V
36V
48V
60V
36V
48V
60V
IN
IN
IN
IN
IN
IN
IN
36V
24V
12V
IN
IN
IN
0
0
0
1
2
3
4
0
1
2
4
2
0
1
4
LOAD (A)
LOAD (A)
LOAD (A)
8027 G15
8027 G16
8027 G17
8027f
5
LTM8027
TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted)
Bias Current vs Load,
Bias Current vs Load,
VOUT = 5V
Bias Current vs Load,
VOUT = 8V
V
OUT = 3.3V
18.0
17.5
17.0
16.5
16.0
15.5
15.0
14.5
14.0
26.0
25.5
25.0
24.5
24.0
23.5
23.0
22.5
22.0
16.0
15.5
15.0
14.5
14.0
13.5
13.0
48V
36V
24V
12V
48V
36V
24V
12V
IN
IN
IN
IN
IN
IN
IN
IN
48V
36V
24V
IN
IN
IN
2
4
1
2
3
0
0
1
3
3
3
4
2
0
1
3
3
3
4
LOAD (A)
LOAD (A)
LOAD (A)
8027 G20
8027 G18
8027 G19
Bias Current vs Load,
VOUT = 12V
Bias Current vs Load,
VOUT = 15V
Bias Current vs Load,
VOUT = 18V
45
44
43
42
41
40
39
38
37
36
35
38
37
36
35
34
33
32
31
30
29.5
29.0
28.5
28.0
27.5
27.0
26.5
26.0
25.5
25.0
48V
36V
24V
IN
IN
IN
48V
36V
24V
IN
IN
IN
48V
36V
IN
IN
0
1
2
2
4
2
4
0
1
4
0
1
3
LOAD (A)
LOAD (A)
LOAD (A)
8027 G22
8027 G21
8027 G23
Bias Current vs Load,
VOUT = 24V
Minimum VIN vs Load,
VOUT = 5V
Minimum VIN vs Load,
VOUT = 8V
6.0
5.9
5.8
5.7
5.6
5.5
5.4
5.3
5.2
5.1
5.0
10.0
9.8
9.6
9.4
9.2
9.0
8.8
8.6
8.4
8.2
8.0
46
44
42
40
38
36
34
32
48V
36V
IN
IN
0
1
2
4
0
1
2
3
4
2
0
1
4
LOAD (A)
LOAD (A)
LOAD (A)
8027 G25
8027 G26
8027 G44
8027f
6
LTM8027
TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted)
Minimum VIN vs Load,
Minimum VIN vs Load,
Minimum VIN vs Load,
V
OUT = 12V
V
OUT = 15V
V
OUT = 18V
24
23
16.0
15.5
15.0
14.5
14.0
13.5
13.0
12.5
12.0
19.0
18.5
18.0
17.5
17.0
16.5
16.0
15.5
15.0
22
21
20
19
18
2
2
0
1
2
3
4
0
1
3
3
3
4
0
1
3
4
LOAD (A)
LOAD (A)
LOAD (A)
8027 G29
8027 G27
8027 G28
Minimum VIN vs Load,
VOUT = 24V
Minimum VIN vs VOUT
,
Minimum VIN vs Load,
VOUT = –3.3V
IOUT = 4A
32
30
28
35
30
9
8
7
6
5
4
3
2
1
0
25
20
15
10
5
26
24
22
20
18
0
5
10
15
(V)
25
0
20
1
2
4
0
2
0
1
3
4
V
LOAD (A)
LOAD (A)
OUT
8027 G31
8027 G30
8027 G45
Minimum VIN vs Load,
VOUT = –5V
Minimum VIN vs Load,
VOUT = –8V
Minimum VIN vs Load,
VOUT = –12V
50
45
40
35
30
25
20
15
10
5
12
10
30
25
8
6
20
15
4
2
0
10
5
0
0
0
1
2
4
0
1
2
3
4
0
1
2
3
4
LOAD (A)
LOAD (A)
LOAD (A)
8027 G32
8027 G33
8027 G34
8027f
7
LTM8027
TYPICAL PERFORMANCE CHARACTERISTICS (TA = 25°C unless otherwise noted)
Temperature Rise vs Load,
VOUT = 2.5V
Temperature Rise vs Load,
VOUT = 3.3V
Temperature Rise vs Load,
VOUT = 5V
50
45
40
35
30
25
20
15
10
5
45
40
35
30
25
20
15
10
5
42
37
32
27
22
17
12
7
60V
IN
60V
IN
36V
IN
48V
IN
48V
IN
24V
IN
36V
IN
36V
IN
12V
IN
24V
IN
24V
IN
5V
IN
12V
IN
12V
IN
IN
5V
0
0
2
2
0
1
3
4
2
4
2
0
1
3
0
1
3
4
LOAD (A)
LOAD (A)
LOAD (A)
8027 G36
8027 G37
8027 G35
Temperature Rise vs Load,
VOUT = 8V
Temperature Rise vs Load,
VOUT = 12V
Temperature Rise vs Load,
VOUT = 15V
70
60
50
90
80
70
60
50
40
30
20
10
0
80
70
60
50
40
30
20
10
0
60V
IN
60V
IN
60V
IN
48V
IN
48V
IN
48V
IN
36V
IN
36V
IN
36V
IN
24V
IN
24V
IN
24V
IN
12V
IN
20.5V
IN
16V
IN
40
30
20
10
0
1
2
4
0
3
2
0
1
3
4
2
0
1
3
4
LOAD (A)
LOAD (A)
LOAD (A)
8027 G38
8027 G40
8027 G39
Temperature Rise vs Load,
VOUT = 18V
Temperature Rise vs Load,
VOUT = 24V
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
60V
IN
60V
IN
48V
IN
48V
IN
36V
26V
36V
IN
IN
IN
0
1
2
3
4
0
1
2
3
4
LOAD (A)
LOAD (A)
8027 G41
8027 G42
8027f
8
LTM8027
PIN FUNCTIONS
V (Bank3):TheV pinsuppliescurrenttotheLTM8027’s
GND (Bank 2): Tie these GND pins to a local ground plane
IN
IN
internal regulator and to the internal power switch. This
pin must be locally bypassed with an external, low ESR
capacitor (see Table 2).
below the LTM8027 and the circuit components.
RT (Pin B1): The RT pin is used to program the switching
frequency of the LTM8027 by connecting a resistor from
thispintoground.TheApplicationsInformationsectionof
the data sheet includes a table to determine the resistance
value based on the desired switching frequency. Minimize
capacitance at this pin.
V
(Bank 1): Power Output Pins. Apply the output filter
OUT
capacitor and the output load between these and the GND
pins.
AUX (Pin A7): Low Current Voltage Source for BIAS1and
BIAS2.Inmanydesigns,theBIASpinsaresimplyconnected
SYNC (Pin C1): The SYNC pin provides an external clock
to V . The AUX pin is internally connected to V
and
input for synchronization of the internal oscillator. The
OUT
OUT
is placed near the BIAS pins to ease printed circuit board
R resistor should be set such that the internal oscilla-
T
routing. Although this pin is internally connected to V
,
tor frequency is 10% to 25% below the external clock
frequency. If unused, the SYNC pin is connected to GND.
FormoreinformationseeOscillatorSyncintheApplication
Information section of this data sheet.
OUT
do NOT connect this pin to the load. If this pin is not tied
to BIAS1 and BIAS2, leave it floating.
BIAS1 (Pin A6): The BIAS1 pin connects to the internal
power bus. Connect to a power source greater than 8.5V.
If the output is greater than 8.5V, connect it to this pin. If
the output voltage is less, connect this to a voltage source
between 8.5V and 15V. For proper operation, connect this
pin to the same power source as BIAS2.
ADJ (Pin A2): The LTM8027 regulates its ADJ pin to 1.23V.
Connect the adjust resistor from this pin to ground. The
value of R
is given by the equation:
ADJ
R
= 613.77/(V
– 1.23)
OUT
ADJ
where R
is in kΩ.
ADJ
BIAS2 (Pin A3): Internal Biasing Power. This pin must be
connected to the same power source as BIAS1 for proper
operation. Always connect this pin to a voltage source
above 8.5V. Do not leave BIAS2 floating.
SS (Pin A5): The soft-start pin is used to program the
supply soft-start function. Use the following formula to
calculate C for a given output voltage slew rate:
SS
C
= 2μA(t /1.231V)
SS
RUN (Pin A4): Tie the RUN pin to ground to shut down the
LTM8027. Tie to 1.4V or more for normal operation. The
RUN pin is internally clamped to 5V, so when it is pulled
up, be sure to use a pull-up resistor that limits the cur-
rent in to the RUN pin to less than 1mA. If the shutdown
SS
The pin should be left unconnected when not using the
soft-start function.
feature is not used, tie this pin to the V pin through a
IN
pull-up resistor.
8027f
9
LTM8027
BLOCK DIAGRAM
V
IN
V
OUT
6.8μH
4.7pF
499k
2.2μF
RUN
SS
AUX
INTERNAL
CURRENT
MODE
CONTROLLER
CONNECTION
TO V
OUT
SYNC
BIAS1
BIAS2
INTERNAL
LINEAR
REGULATOR
INTV
CC
V
IN
GND
R
T
ADJ
8027 BD
OPERATION
The LTM8027 is a standalone nonisolated step-down
switching DC/DC power supply with an input voltage
range of 4.5V to 60V that can deliver up to 4A of output
current.Thismoduleprovidesapreciselyregulatedoutput
voltage up to 24V, programmable via one external resistor.
Given that the LTM8027 is a step-down converter, make
sure that the input voltage is high enough to support the
desiredoutputvoltageandloadcurrent. Asimplifiedblock
diagram is given above. The LTM8027 contains a current
mode controller, power switching element, power induc-
tor, power MOSFETs and a modest amount of input and
output capacitance.
The LTM8027 is a fixed frequency PWM regulator. The
switching frequency is set by simply connecting the ap-
propriate resistor from the RT pin to GND.
A linear regulator provides internal power (shown as
INTV on the Block Diagram) to the control circuitry. The
CC
bias regulator normally draws power from the V pin, but
IN
if the BIAS1and BIAS2 pins are connected to an external
voltage higher than 8.5V, bias power will be drawn from
theexternalsource(typicallytheregulatedoutputvoltage).
This improves efficiency. The RUN pin is used to enable
or place the LTM8027 in shutdown, disconnecting the
output and reducing the input current to less than 10μA.
8027f
10
LTM8027
APPLICATIONS INFORMATION
For most applications, the design process is straight
forward, summarized as follows:
inductance forms a high Q (under damped) tank circuit.
If the LTM8027 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.
1. Look at Table 2 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 ADJ
T
Input Power Requirements
3. Connect the BIAS pins as indicated.
The LTM8027 is biased using an internal linear regula-
Whilethesecomponentandconnectioncombinationshave
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.
tor to generate operational voltages from the V pin.
IN
Virtually all of the circuitry in the LTM8027 is biased via
this internal linear regulator output (INTV ). This pin is
CC
internally decoupled with a low ESR capacitor to GND.
The V regulator generates an 8V output provided there
CC
Capacitor Selection Considerations
is ample voltage on the V pin. The V regulator has
IN
CC
The C and C
capacitor values in Table 2 are the
IN
OUT
approximately 1V of dropout, and will follow the V pin
IN
minimum recommended values for the associated oper-
ating conditions. Applying capacitor values below those
indicated in Table 2 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.
with voltages below the dropout threshold.
The LTM8027 has a typical start-up requirement of V >
IN
7.5V. This assures that the onboard regulator has ample
headroom to bring INTV above its UVLO threshold.
CC
The INTV regulator can only source current, so forcing
CC
the BIAS pin above 8.5V allows use of externally derived
power for the IC. This effectively shuts down the internal
linear regulator and reduces power dissipation within the
LTM8027. Using the onboard regulator for start-up, then
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.
deriving power for V from the converter output maxi-
CC
mizes conversion efficiencies and is common practice. If
V
ismaintainedabove6.5Vusinganexternalsource,the
CC
LTM8027 can continue to operate with V as low as 4V.
IN
BIAS Power
The internal circuitry of the LTM8027 is powered by the
INTV bus, which is derived either from the afore men-
CC
Ceramic capacitors are also piezoelectric. The LTM8027’s
switching frequency depends on the load current, and
at light loads it can excite a ceramic capacitor at audio
frequencies, generating audible noise.
tioned internal linear regulator or the BIAS1 and BIAS2
pins, if it is greater than 8.5V. Since the internal linear
regulator is by nature dissipative, deriving INTV from
CC
an external source through the BIAS pins reduces the
power lost within the LTM8027 and can increase overall
system efficiency.
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LTM8027. A
ceramic input capacitor combined with trace or cable
8027f
11
LTM8027
APPLICATIONS INFORMATION
For example, suppose the LTM8027 needs to provide 5V
Operating Frequency Tradeoffs
from an input voltage source that is nominally 12V. From
The LTM8027 uses a constant frequency architecture that
can be programmed over a 100kHz to 500kHz range with
a single resistor from the RT pin to ground. The nominal
voltage on the RT pin is 1V and the current that flows from
this pin is used to charge an internal oscillator capacitor.
Table 2, the recommended R value is 162k, which cor-
T
responds to an operating frequency of 210kHz. From the
graphs in the Typical Performance Characteristics, the
typical INTV current at 12V and 210kHz is 15mA. The
CC
IN
power dissipated by the internal linear regulator at 12V
IN
The value of R for a given operating frequency can be
T
is given by the equation:
chosen from Figure 1 or Table 1.
P
= (V – 8.5) • I
IN INTVCC
INTVCC
600
500
400
300
200
100
0
or only 54mW. This has a small but probably acceptable
effect on the operating temperature of the LTM8027.
If the input rises to 60V, however, the power dissipation is
a lot higher, over 750mW. This can cause unnecessarily
high junction temperatures if the INTV regulator must
CC
dissipate this amount of power for very long.
Soft-Start
The soft-start function controls the slew rate of the power
supply output voltage during start-up. A controlled output
voltagerampminimizesoutputvoltageovershoot,reduces
0
50
100
(kΩ)
150
200
R
T
8027 F01
inrush current from the V supply, and facilitates supply
Figure 1. Timing Resistor (RT) Value
IN
sequencing.AcapacitorconnectedfromtheSSpintoGND
programs the slew rate. The capacitor is charged from an
internal 2μA current source producing a ramped voltage
that overrides the command reference to the controller,
resulting in a smooth output voltage ramp. The soft-start
circuitisdisabledoncetheSSpinvoltagehasbeencharged
to 200mV above the internal reference of 1.231V.
Table 1 lists typical resistor values for common operating
frequencies.
Table 1. RT Resistor Values vs Frequency
R (kΩ)
T
f
(kHz)
SW
187
118
100
150
200
250
300
350
400
450
500
During a V UVLO, INTV undervoltage or RUN event,
IN
CC
82.5
the SS pin voltage is discharged with a 50μA. Therefore,
the value of the SS capacitor determines how long one
of these events must be in order to completely discharge
the soft-start capacitor. In the case of an output overload
or short circuit, the SS pin voltage is clamped to a diode
drop above the ADJ pin. Once the short has been removed
63.4k
48.7k
40.2k
31.6k
27.4k
23.7k
the V pin voltage starts to recover. The soft-start circuit
ADJ
takes control of the output voltage slew rate once the
V
pin voltage has exceeded the slowly ramping SS pin
ADJ
voltage, reducing the output voltage overshoot during a
short-circuit recovery.
8027f
12
LTM8027
APPLICATIONS INFORMATION
It is recommended that the user apply the R value given
Because the LTM8027 high power converter is a power
transfer device, a voltage that is lower than expected on
the input supply could require currents that exceed the
sourcing capabilities of that supply, causing the system
to lock up in an undervoltage state. Input supply start-
up protection can be achieved by enabling the RUN pin
T
in Table 2 for the input and output operating condition.
System level or other considerations, however, may ne-
cessitateanotheroperatingfrequency.WhiletheLTM8027
is flexible enough to accommodate a wide range of oper-
ating frequencies, a haphazardly chosen one may result
in undesirable operation under certain operating or fault
conditions. A frequency that is too high can damage the
LTM8027 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.
using a resistive divider from the V supply to ground.
IN
Setting the divider output to 1.4V when that supply is at
an adequate voltage prevents an LTM8027 converter from
drawing large currents until the input supply is able to
provide the required power. 200mV of input hysteresis on
the RUN pin allows for about 15% of input supply droop
before disabling the converter.
The maximum frequency (f
) at which the LTM8027
MAX
should be allowed to switch and the minimum frequency
set resistor value that should be used for a given set of
input and output operating condition is given in Table 2
Input UVLO and RUN
The RUN pin has a precision voltage threshold with hys-
teresis which can be used as an undervoltage lockout
threshold (UVLO) for the power supply. Undervoltage
lockout keeps the LTM8027 in shutdown until the supply
input voltage is above a certain voltage programmed by
theuser.Thehysteresisvoltagepreventsnoisefromfalsely
as R
. There are additional conditions that must be
T(MIN)
satisfied if the synchronization function is used. Please
refer to the Synchronization section for details.
Output Voltage Programming
tripping UVLO. Resistors are chosen by first selecting R
(refer to Figure 2). Then:
B
The LTM8027 regulates its ADJ pin to 1.23V. Connect the
adjust resistor from this pin to ground. The value of R
ADJ
– 1.23),
is given by the equation R
= 613.77/(V
V
⎛
⎜
⎞
ADJ
OUT
IN(ON)
RA =RB •
–1
where R
is in kΩ.
⎟
ADJ
1.4V
⎝
⎠
RUN Control
whereV
istheinputvoltageatwhichtheundervoltage
IN(ON)
The LTM8027 RUN pin uses a reference threshold of
1.4V. This precision threshold allows use of the RUN pin
for both logic-level controlled applications and analog
monitoringapplicationssuchaspowersupplysequencing.
The LTM8027 operational status is primarily controlled
by a UVLO circuit on internal power source. When the
lockout is disabled and the supply turns on.
V
SUPPLY
R
R
A
B
RUN PIN
LTM8027 is enabled via the RUN pin, only the V regula-
CC
tor is enabled. Switching remains disabled until the UVLO
8027 F02
threshold is achieved at the V pin, when the remainder
CC
of the LTM8027 is enabled and switching commences.
Figure 2. Undervoltage Lockout Resistive Divider
8027f
13
LTM8027
APPLICATIONS INFORMATION
Example: Select R = 49.9k, V
= 14.5V (based upon
Hot-Plugging Safely
B
IN(ON)
a 15V minimum input voltage)
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypass capacitor of LTM8027. However, these capacitors
can cause problems if the LTM8027 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 under damped tank circuit, and the volt-
14.5V
1.4V
⎛
⎞
⎠
R = 49.9k •
–1 = 464k
⎜
⎝
⎟
A
The V turn off voltage is 15% below turn on. In the ex-
IN
ample the V
would be 12.3V. The shutdown function
IN(OFF)
can be disabled by connecting the RUN pin to the V pin
IN
through a large value pull-up resistor. This pin contains
age at the V pin of the LTM8027 can ring to twice the
a low impedance clamp at 6V, so the RUN pin will sink
IN
nominal input voltage, possibly exceeding the LTM8027’s
rating and damaging the part. If the input supply is poorly
controlledortheuserwillbepluggingtheLTM8027intoan
energizedsupply, theinputnetworkshouldbedesignedto
prevent this overshoot by introducing a damping element
into the path of current flow. This is often done by adding
an inexpensive electrolytic bulk capacitor across the input
terminals of the LTM8027. The criteria for selecting this
capacitoristhattheESRishighenoughtodamptheringing,
and the capacitance value is several times larger than the
LTM8027ceramicinputcapacitor. Thebulkcapacitordoes
not need to be located physically close to the LTM8027;
it should be located close to the application board’s input
connector, instead.
current from the pull-up resistor (R ):
PU
V – 6V
IN
IRUN
=
RPU
Because this arrangement will clamp the RUN pin to 6V,
it will violate the 5V absolute maximum voltage rating of
the pin. This is permitted, however, as long as the absolute
maximum input current rating of 1mA is not exceeded.
Input RUN pin currents of <100μA are recommended: a
1M or greater pull-up resistor is typically used for this
configuration.
Soft-Start
The desired soft-start time (t ) is programmed via the
SS
Synchronization
C
capacitor as follows:
SS
The oscillator can be synchronized to an external clock.
2µA • tSS
1.231V
CSS
=
Choose the R resistor such that the resultant frequency is
T
atleast10%belowthedesiredsynchronizationfrequency.
It is recommended that the SYNC pin be driven with a
square wave that has amplitude greater than 2.3V, pulse
width greater than 1μs and rise time less than 500ns. The
rising edge of the sync wave form triggers the discharge
of the internal oscillator capacitor.
The amount of time in which the power supply must be
under a V , V or V UVLO fault condition (t )
IN CC
SHDN
FAULT
before the SS pin voltage enters its active region is ap-
proximated by the following formula:
CSS • 0.65V
tFAULT
=
50µA
8027f
14
LTM8027
APPLICATIONS INFORMATION
PCB Layout
Use vias to connect the GND copper area to the board’s
internalgroundplanes. LiberallydistributetheseGNDvias
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 3. The LTM8027 can benefit from the heat sinking
afforded by vias that connect to internal 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.
Most of the headaches associated with PCB layout have
been alleviated or even eliminated by the high level of
integration of the LTM8027. The LTM8027 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 3
for a suggested layout.
Ensurethatthegroundingandheatsinkingareacceptable.
A few rules to keep in mind are:
1. Place the R and R resistors as close as possible to
ADJ
T
their respective pins.
Thermal Considerations
2. Place the C capacitor as close as possible to the V
IN
IN
The LTM8027 output current may need to be derated if it is
requiredtooperateinahighambienttemperatureordeliver
alargeamountofcontinuouspower.Theamountofcurrent
deratingisdependentupontheinputvoltage,outputpower
and ambient temperature. The temperature rise curves
given in the Typical Performance Characteristics section
can be used as a guide. These curves were generated by a
and GND connection of the LTM8027.
3. Place the C
capacitor as close as possible to the
OUT
V
and GND connection of the LTM8027.
OUT
4. Place the C and C
capacitors such that their
IN
OUT
ground current flow directly adjacent to or underneath
the LTM8027.
2
LTM8027 mounted to a 58cm 4-layer FR4 printed circuit
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 LTM8027.
board. Boards of other sizes and layer count can exhibit
differentthermalbehavior,soitisincumbentupontheuser
to verify proper operation over the intended system’s line,
load and environmental operating conditions.
V
OUT
C
OUT
C
OUT
GND
AUX
BIAS1
SS
RUN
C
IN
V
IN
BIAS2
R
ADJ
R
T
GND
8027 F03
SYNC
Figure 3. Suggested Layout
8027f
15
LTM8027
APPLICATIONS INFORMATION
The junction-to-air and junction-to-board thermal resis-
tances given in the Pin Configuration diagram may also
be used to estimate the LTM8027 internal temperature.
These thermal coefficients are determined per JESD 51-9
(JEDECstandard,testboardsforareaarraysurfacemount
package thermal measurements) through analysis and
physical correlation. Bear in mind that the actual thermal
resistance of the LTM8027 to the printed circuit board
depends upon the design of the circuit board.
The die temperature of the LTM8027 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
LTM8027. The bulk of the heat flow out of the LTM8027
is through the bottom of the module and the LGA pads
into the printed circuit board. Consequently a poor printed
circuit board design can cause excessive heating, result-
ing in impaired performance or reliability. Please refer to
the PCB Layout section for printed circuit board design
suggestions.
Table 2. Recommended Component Values and Configuration
(TA = 25°C. See Typical Performance Characteristics for load Conditions)
V
RANGE
(V)
V
R
f
R
f
R
MAX
IN
OUT
ADJ
OPTIMAL
OPTIMAL
MAX
(V)
3.3
5
C
C
BIAS1/BIAS2
8.5V to 15V
8.5V to 15V
8.5V to 15V
AUX
(kΩ)
(kHz)
(kΩ)
(kHz)
160
230
350
500
500
500
500
(kΩ)
IN
OUT
4.5 to 60
7.5 to 60
10.5 to 60
16 to 60
20.5 to 60
26 to 60
34 to 60
301
115
210
260
300
350
400
430
154
75.0
59.0
48.7
40.2
31.6
28.7
107
2 × 4.7μF 2220 100V 5 × 100μF 1812 6.3V
2 × 4.7μF 2220 100V 4 × 100μF 1210 6.3V
2 × 4.7μF 2220 100V 4 × 47μF 1210 10V
2 × 4.7μF 2220 100V 4 × 22μF 1210 16V
2 × 4.7μF 2220 100V 4 × 22μF 1210 16V
2 × 4.7μF 2220 100V 4 × 10μF 1812 25V
2 × 4.7μF 2220 100V 4 × 10μF 1812 25V
162
68.2
40.2
23.7
23.7
23.7
23.7
8
90.9
56.2
44.2
36.5
26.7
12
15
18
24
AUX
8.5V to 15V
8.5V to 15V
4.5 to 40
4.5 to 40
7.5 to 40
10.5 to 40
16 to 40
20.5 to 40
26 to 40
34 to 40
2.5
3.3
5
8.5V to 15V
8.5V to 15V
8.5V to 15V
8.5V to 15V
AUX
487
301
145
165
210
260
300
350
400
430
124
102
185
240
315
500
500
500
500
500
88.7
64.9
45.3
23.7
23.7
23.7
23.7
23.7
2 × 10μF 2220 50V 5 × 100μF 1812 6.3V
2 × 10μF 2220 50V 4 × 100μF 1812 6.3V
2 × 10μF 2220 50V 4 × 100μF 1210 6.3V
2 × 10μF 2220 50V 4 × 47μF 1210 10V
2 × 10μF 2220 50V 4 × 22μF 1210 16V
1 × 10μF 2220 50V 4 × 22μF 1210 16V
1 × 10μF 2220 50V 4 × 10μF 1812 25V
1 × 10μF 2220 50V 4 × 10μF 1812 25V
162
75.0
59.0
48.7
40.2
31.6
28.7
8
90.9
56.2
44.2
36.5
26.7
12
15
18
24
AUX
8.5V to 15V
8.5V to 15V
4.5 to 56
4.5 to 55
10.5 to 52
16 to 48
–3.3
–5
8.5V to 15V Above Output
8.5V to 15V Above Output
8.5V to 15V Above Output
AUX
301
162
115
190
260
300
154
90.9
59.0
48.7
155
230
350
500
115
68.2
40.2
23.7
2 × 4.7μF 2220 100V 5 × 100μF 1812 6.3V
2 × 4.7μF 2220 100V 4 × 100μF 1210 6.3V
2 × 4.7μF 2220 100V 4 × 47μF 1210 10V
2 × 4.7μF 2220 100V 4 × 22μF 1210 16V
–8
90.9
56.2
–12
8027f
16
LTM8027
TYPICAL APPLICATIONS
5V VOUT Step-Down Converter
3.3V VOUT Step-Down Converter
V
3.3V
4A
V
5V
4A
OUT
OUT
V
*
V
IN
7.5V TO 60V
IN
V
IN
V
V
V
OUT
OUT
IN
4.5V TO 40V
10μF
s2
4.7μF
s2
1M
1M
LTM8027
LTM8027
9V
9V
RUN
SS
BIAS1
BIAS2
AUX
RUN
SS
BIAS1
BIAS2
AUX
100μF
s4
100μF
s4
SYNC
RT
SYNC
RT
ADJ
ADJ
GND
GND
102k
301k
75k
162k
*RUNNING VOLTAGE. SEE APPLICATIONS
INFORMATION FOR START-UP DETAILS
3845 TA02
3845 TA03
18V VOUT Step-Down Converter
15V VOUT Step-Down Converter
V
V
OUT
OUT
V
V
15V
18V
IN
IN
V
IN
V
V
V
OUT
OUT
IN
20.5V TO 60V
26V TO 60V
3.5A
4A SURGE
3A
4A SURGE
4.7μF
s2
4.7μF
s2
1M
1M
LTM8027
LTM8027
9V
RUN
SS
BIAS1
BIAS2
AUX
RUN
SS
BIAS1
BIAS2
AUX
22μF
s4
10μF
s4
SYNC
RT
SYNC
RT
ADJ
ADJ
GND
GND
40.2k
44.2k
31.6k
36.5k
3845 TA04
3845 TA05
–12V VOUT Postitive-to-Negative Converter
V
IN
V
V
OUT
IN
20V TO 48V
4.7μF
s2
1M
LTM8027
RUN
SS
BIAS1
BIAS2
AUX
22μF
s4
SYNC
RT
ADJ
GND
56.2k
48.7k
V
–12V
3A
OUT
3845 TA07
8027f
17
LTM8027
PACKAGE DESCRIPTION
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 . 0 0 0
1 . 2 7 0
2 . 5 4 0
3 . 8 1 0
5 . 0 8 0
6 . 3 5 0
8027f
18
LTM8027
PACKAGE DESCRIPTION
Pin Assignment Table
(Arranged by Pin Number)
PIN NAME
PIN NAME
PIN NAME
GND
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
A11
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
B11
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
D1
D2
D3
D4
D5
GND
ADJ
D6
D7
D8
D9
D10
D11
E1
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
H5
H6
H7
H8
H9
H10
H11
J1
GND
BIAS2
RUN
SS
GND
GND
V
V
V
V
V
V
OUT
OUT
OUT
IN
BIAS1
AUX
GND
GND
GND
GND
RT
E2
E3
J2
IN
E4
J3
IN
E5
J5
GND
GND
GND
GND
E6
J6
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
SYNC
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
E7
J7
E8
J8
E9
V
OUT
V
OUT
V
OUT
J9
V
V
V
V
V
V
OUT
OUT
OUT
IN
E10
E11
F1
J10
J11
K1
K2
K3
K5
K6
K7
K8
K9
K10
K11
L1
GND
GND
GND
GND
GND
GND
GND
GND
F2
IN
F3
IN
F4
GND
GND
GND
GND
F5
F6
F7
F8
V
V
V
V
V
V
OUT
OUT
OUT
IN
F9
V
V
V
OUT
OUT
OUT
F10
F11
G5
G6
G7
G8
G9
G10
G11
H1
H2
H3
GND
GND
GND
GND
L2
IN
L3
IN
L5
GND
GND
GND
GND
L6
V
V
V
V
V
V
L7
OUT
OUT
OUT
IN
L8
L9
V
V
V
OUT
OUT
OUT
L10
L11
IN
IN
8027f
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.
19
LTM8027
PACKAGE PHOTOGRAPH
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTM4600
10A DC/DC μModule Regulator
Basic 10A DC/DC μModule, 15mm × 15mm × 2.8mm LGA
–55°C to 125°C Operation, 15mm × 15mm × 2.8mm LGA
LTM4600HVMPV Military Plastic 10A DC/DC μModule Regulator
LTM4601/
LTM4601A
12A DC/DC μModule with PLL, Output Tracking/
Margining and Remote Sensing
Synchronizable, PolyPhase Operation, LTM4601-1 Version has no Remote
Sensing
LTM4602
LTM4603
6A DC/DC μModule Regulator
Pin Compatible with the LTM4600
6A DC/DC μModule with PLL and Output Tracking/ Synchronizable, PolyPhase Operation, LTM4603-1 Version has no Remote
Margining and Remote Sensing
Sensing, Pin Compatible with the LTM4601
LTM4604
LTM4608
LTM8020
LTM8022
4A Low V DC/DC μModule Regulator
2.375V ≤ V ≤ 5V, 0.8V ≤ V
≤ 5V, 9mm × 15mm × 2.3mm LGA
IN
IN
OUT
OUT
8A Low V DC/DC μModule Regulator
2.375V ≤ V ≤ 5V, 0.8V ≤ V
≤ 5V, 9mm × 15mm × 2.8mm LGA
≤ 5V, 6.25mm × 6.25mm × 2.32mm LGA
IN
IN
200mA, 36V DC/DC μModule Regulator
1A, 36V DC/DC μModule Regulator
Fixed 450kHz Frequency, 1.25V ≤ V
OUT
Adjustable Frequency, 0.8V ≤ V
Pin Compatible to the LTM8023
≤ 5V, 11.25mm × 9mm × 2.82mm LGA,
OUT
LTM8023
LTM8025
2A, 36V DC/DC μModule Regulator
3A, 36V DC/DC μModule Regulator
Adjustable Frequency, 0.8V ≤ V
≤ 5V, 11.25mm × 9mm × 2.82mm LGA,
OUT
Pin Compatible to the LTM8022
0.8V ≤ V ≤ 24V, 9mm × 15mm × 4.32mm LGA
OUT
8027f
LT 1009 • PRINTED IN USA
LinearTechnology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
20
●
●
© LINEAR TECHNOLOGY CORPORATION 2009
(408) 432-1900 FAX: (408) 434-0507 www.linear.com
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