LINER LTM8028 36vin, ultrafast, low output noise 5a module regulator Datasheet

LTM8028
36VIN, UltraFast,
Low Output Noise 5A
µModule Regulator
Features
n
n
n
n
n
n
n
n
n
n
n
n
Description
High Performance 5A Linear Regulator with
Switching Step-Down Converter for High Efficiency
Digitally Programmable VOUT: 0.8V to 1.8V
Input Voltage Range: 6V to 36V
Very Tight Tolerance Over Temperature, Line, Load
and Transient Response
Low Output Noise: 40μVRMS (10Hz to 100kHz)
Parallel Multiple Devices for 10A or More
Accurate Programmable Current Limit to Allow
Asymmetric Power Sharing
Analog Output Margining: ±10% Range
Synchronization Input
Stable with Low ESR Ceramic Output Capacitors
15mm × 15mm × 4.92mm Surface Mount
BGA Package
SnPb or RoHS Compliant Finish
Applications
n
n
n
n
The LTM®8028 is a 36VIN, 5A µModule® regulator, consisting of an UltraFast™ 5A linear regulator preceded by a
high efficiency switching regulator. In addition to providing
tight output regulation, the linear regulator automatically
controls the output voltage of the switcher to provide
optimal efficiency and headroom for dynamic response.
The output voltage is digitally selectable in 50mV increments over a 0.8V to 1.8V range. An analog margining
function allows the user to adjust system output voltage
over a continuous ±10% range, and a single-ended feedback sense line may be used to mitigate IR drops due to
parasitic resistance.
The LTM8028 is packaged in a compact (15mm × 15mm ×
4.92mm) overmolded ball grid array (BGA) package suitable for automated assembly by standard surface mount
equipment. The LTM8028 is available with SnPb (BGA) or
RoHS compliant terminal finish.
L, LT, LTC, LTM, µModule, Linear Technology and the Linear logo are registered trademarks
and UltraFast is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners.
FPGA and DSP Supplies
High Speed I/O
ASIC and Microprocessor Supplies
Servers and Storage Devices
Click to view associated TechClip Videos.
Typical Application
Low Output Noise, 1.2V, 5A µModule Regulator
VIN
9V TO 15V
LTM8028
VIN
150k
10µF
0.01µF
RUN
MARGA
IMAX
BKV
SS
82.5k
RT
f = 500kHz
VOUT
1.2V
5A
VOUT
LINEAR
REGULATOR SENSEP
PGOOD
SYNC
GND
VOB VO0 VO1 VO2
137µF
+
VOUT
20mV/DIV
IOUT
2A/DIV
∆IOUT = 0.5A TO 5A
1µs RISE/FALL TIME
10µs/DIV
100µF
470µF
8028 TA01a
FULL LOAD
NOISE AND RIPPLE
500µV/DIV
1µs/DIV
MEASURED PER AN70, 150MHz BW
8028 TA01b
8028fb
For more information www.linear.com/LTM8028
1
LTM8028
Absolute Maximum Ratings
Pin Configuration
(Notes 1, 4)
TOP VIEW
VIN.............................................................................40V
VOUT.............................................................................3V
RUN, SS, SYNC ...........................................................6V
Current Into RUN...................................................100μA
VOB, VO0, VO1, VO2, TEST,
PGOOD, SENSEP, MARGA............................................4V
RT, BKV, IMAX..............................................................3V
Maximum Operating Junction Temperature
(Note 2).................................................................. 125°C
Peak Solder Reflow Body Temperature.................. 245°C
Maximum Storage Temperature............................. 125°C
11
BANK 1
10
SENSEP
TEST
PGOOD
VO1
VOB
MARGA
VO0
VO2
BANK 2
VOUT
BKV
9
8
7
BANK 3
6
GND
5
4
3
2
SS SYNC
1
BANK 4
VIN
IMAX RT RUN
A
B
C
D
E
F
G
H
J
K
L
BGA PACKAGE
114 PADS (15mm × 15mm × 4.92mm)
TJMAX = 125°C, θJA = 17.7°C/W,
θJB = 6.0°C/W, θJCtop = 15°C/W,
θJCbottom = 6.0°C/W
θ VALUES DETERMINED PER JEDEC 51-9, 51-12
WEIGHT = 1.8 GRAMS
Order Information
PART NUMBER
PAD OR BALL FINISH
PART MARKING*
DEVICE
FINISH CODE
PACKAGE
TYPE
MSL
RATING
TEMPERATURE RANGE
(Note 2)
LTM8028EY#PBF
SAC305 (RoHS)
LTM8028Y
e1
BGA
3
–40°C to 125°C
LTM8028IY#PBF
SAC305 (RoHS)
LTM8028Y
e1
BGA
3
–40°C to 125°C
LTM8028IY
SnPb (63/37)
LTM8028Y
e0
BGA
3
–40°C to 125°C
LTM8028MPY#PBF
SAC305 (RoHS)
LTM8028Y
e1
BGA
3
–55°C to 125°C
LTM8028MPY
SnPb (63/37)
LTM8028Y
e0
BGA
3
–55°C to 125°C
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
• Pb-free and Non-Pb-free Part Markings:
www.linear.com/leadfree
• LGA and BGA Package and Tray Drawings:
www.linear.com/packaging
Electrical Characteristics
The l denotes the specifications which apply over the full internal
operating temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, RUN = 3V unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN
TYP
Minimum Input Voltage
Output DC Voltage
Output DC Current
l
l
l
l
l
VOUT = 1.8V
0.788
0.985
1.182
1.477
1.773
0.8
1.0
1.2
1.5
1.8
MAX
UNITS
6
V
0.812
1.015
1.218
1.523
1.827
V
V
V
V
V
5
A
8028fb
2
For more information www.linear.com/LTM8028
LTM8028
Electrical Characteristics
The l denotes the specifications which apply over the full internal
operating temperature range, otherwise specifications are at TA = 25°C. VIN = 12V, RUN = 3V unless otherwise noted. (Note 2)
PARAMETER
CONDITIONS
MIN
Quiescent Current Into VIN
RUN = 0V
No load
Line Regulation
6V < VIN < 36V, IOUT = 10mA
Load Regulation
0.01A < IOUT < 5A, VOUT = 0.8V, BKV = 1.05V, RUN = 0V
TYP
MAX
1
35
mV
–1.5
–3
–5.5
mV
mV
–2
–4
–7.5
mV
mV
–2
–4
–7.5
mV
mV
–2.5
–5
–9
mV
mV
–3
–7
–13
mV
mV
l
l
0.01A < IOUT < 5A, VOUT = 1.2V, BKV = 1.45V, RUN = 0V
l
0.01A < IOUT < 5A, VOUT = 1.5V, BKV = 1.75V, RUN = 0V
l
0.01A < IOUT < 5A, VOUT = 1.8V, BKV = 2.05V, RUN = 0V
µA
mA
1
l
0.01A < IOUT < 5A, VOUT = 1.0V, BKV = 1.25V, RUN = 0V
UNITS
l
Sense Pin Current
VOUT = 0.8V
VOUT = 1.8V
50
300
µA
µA
Switching Frequency
RT = 40.2k
RT = 200k
1000
200
kHz
kHz
RUN Pin Current
RUN = 1.45V
5.5
µA
RUN Threshold Voltage (Falling)
l
1.49
RUN Input Hysteresis
IMAX Pin Current
IMAX = 0.75V
IMAX Current Limit Accuracy
IMAX = 1.5V
IMAX = 0.75V
1.55
130
mV
µA
6.1
3.6
11
SYNC Input Threshold
fSYNC = 500kHz
SYNC Bias Current
SYNC = 0V
0.6
VOB Voltage
VOB = 3.3V
l
VOx Input High Threshold
VOB = 3.3V
l
3.05
VOx Input Z Range
VOB = 3.3V
l
0.75
A
A
µA
1.3
V
1
µA
3.3
VOx Input Low Threshold
V
125
5.0
2.20
SS Pin Current
1.61
V
0.25
V
V
2.4
V
VOx Input Current High
40
µA
VOx Input Current Low
40
µA
MARGA Pin Current
MARGA = 0V
3.5
μA
PGOOD Threshold
VOUT(NOMINAL) = 1.0V, VOUT Rising
VOUT(NOMINAL) = 1.0V, VOUT Falling
0.9
0.85
V
V
Output Voltage Noise (Note 3)
VOUT = 1.8V, COUT = 137µF, 5A Load, BW = 10Hz to 100kHz
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The LTM8028E 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 LTM8028I is guaranteed to meet specifications over the full –40°C
to 125°C internal operating temperature range. The LTM8028MP is
40
µVRMS
guaranteed to meet specifications over the full –55°C to 125°C internal
operating temperature range. Note that the maximum internal temperature
is determined by specific operating conditions in conjunction with board
layout, the rated package thermal resistance and other environmental
factors.
Note 3: Guaranteed by design, characterization and correlation with
statistical process controls.
Note 4: Unless otherwise stated, the absolute minimum voltage is zero.
8028fb
For more information www.linear.com/LTM8028
3
LTM8028
Typical Performance Characteristics
Power Loss vs Output Current,
1VOUT
3
2
36VIN
24VIN
12VIN
6VIN
1
0
0
1
3
4
2
OUTPUT CURRENT (A)
5
5
4
4
POWER LOSS (W)
POWER LOSS (W)
POWER LOSS (W)
4
3
2
36VIN
24VIN
12VIN
6VIN
1
0
5
0
1
3
4
2
OUTPUT CURRENT (A)
8028 G01
2
36VIN
24VIN
12VIN
6VIN
1
3
4
2
OUTPUT CURRENT (A)
2
0
5
36VIN
24VIN
12VIN
6VIN
0
1
3
4
2
OUTPUT CURRENT (A)
1400
800
600
400
200
1
2
4
3
OUTPUT CURRENT (A)
600
400
0
5
5
8028 G07
0
1
2
3
8026 G06
Input Current vs Output Current,
1.5VOUT
2000
1600
1000
800
600
1400
1200
1000
800
600
400
400
200
200
0
1
3
2
OUTPUT CURRENT (A)
6VIN
12VIN
24VIN
36VIN
1800
1200
0
5
4
OUTPUT CURRENT (A)
6VIN
12VIN
24VIN
36VIN
1600
1000
0
800
200
INPUT CURRENT (mA)
1200
1000
Input Current vs Output Current,
1.2VOUT
1800
5
6VIN
12VIN
24VIN
36VIN
8028 G05
INPUT CURRENT (mA)
INPUT CURRENT (mA)
1400
3
4
2
OUTPUT CURRENT (A)
8028 G03
1200
1
6VIN
12VIN
24VIN
36VIN
1
Input Current vs Output Current,
0.8VOUT
3
Input Current vs Output Current,
1VOUT
1600
0
1400
8028 G04
0
0
5
4
POWER LOSS (W)
POWER LOSS (W)
4
3
36VIN
24VIN
12VIN
6VIN
1
5
0
2
Power Loss vs Output Current,
1.8VOUT
5
1
3
8028 G02
Power Loss vs Output Current,
1.5VOUT
0
Power Loss vs Output Current,
1.2VOUT
INPUT CURRENT (mA)
5
Power Loss vs Output Current,
0.8VOUT
5
4
8028 G08
0
0
1
3
4
2
OUTPUT CURRENT (A)
5
8028 G09
8028fb
4
For more information www.linear.com/LTM8028
LTM8028
Typical Performance Characteristics
6.0
1000
1000
500
5.8
OUTPUT CURRENT (A)
1500
0
Output Current vs Input Voltage,
Output Shorted
1200
6VIN
12VIN
24VIN
36VIN
2000
INPUT CURRENT (mA)
Input Current vs Input Voltage,
Output Shorted
INPUT CURRENT (mA)
2500
Input Current vs Output Current,
1.8VOUT
800
600
400
1
3
4
2
OUTPUT CURRENT (A)
5
0
0
10
20
30
INPUT VOLTAGE (V)
8028 G10
10µs/DIV
COUT = 100µF + 22µF + 10µF + 4.7µF
5.0
40
0
12
18
24
INPUT VOLTAGE (V)
30
Transient Response,
Demo Board, 1.5V
VOUT
20mV/DIV
VOUT
20mV/DIV
IOUT
2A/DIV
∆IOUT
0.5A TO 5A
1µs
RISE/FALL
TIME
IOUT
2A/DIV
∆IOUT
0.5A TO 5A
1µs
RISE/FALL
TIME
Transient Response,
Demo Board, 1.8V
10µs/DIV
COUT = 100µF + 22µF + 10µF + 4.7µF
36
8028 G12
Transient Response,
Demo Board, 1.2V
8028 G13
6
8038 G11
Transient Response,
Demo Board, 1V
VOUT
20mV/DIV
IOUT
2A/DIV
∆IOUT
0.5A TO 5A
1µs
RISE/FALL
TIME
5.4
5.2
200
0
5.6
8028 G14
10µs/DIV
COUT = 100µF + 22µF + 10µF + 4.7µF
8028 G15
Output Current vs IMAX Voltage,
12VIN
Output Noise, 1.8VOUT
6
VOUT
20mV/DIV
500µV/DIV
20µs/DIV
COUT = 100µF + 22µF + 10µF + 4.7µF
8028 G16
1µs/DIV
MEASURED WITH HP461A AMPLIFIER
(150MHz BW) AT J5 BNC CONNECTOR
ON DC1738 DEMO BOARD
fSW = 500kHz
COUT = 137µF
5A LOAD
8028 G17
OUTPUT CURRENT (A)
IOUT
2A/DIV
∆IOUT
0.5A TO 5A
1µs
RISE/FALL
TIME
5
4
3
2
1
0
0
0.5
1.0
1.5
IMAX VOLTAGE (V)
2.0
8028 G18
8028fb
For more information www.linear.com/LTM8028
5
LTM8028
Typical Performance Characteristics
Temperature Rise
vs Output Current, 0.8VOUT
TEMPERATURE RISE (°C)
5
0
–5
60
50
50
40
30
20
36VIN
24VIN
12VIN
6VIN
10
–10
–15
60
0.3
0.6
0.9
MARGA VOLTAGE (V)
0
0
1.2
0
1
8028 G19
20
60
50
50
50
TEMPERATURE RISE (°C)
60
20
36VIN
24VIN
12VIN
6VIN
10
0
0
1
2
3
4
OUTPUT CURRENT (A)
40
30
20
36VIN
24VIN
12VIN
6VIN
10
5
0
0
1
40
30
20
36VIN
24VIN
12VIN
6VIN
0
0
1
2
3
4
OUTPUT CURRENT (A)
8028 G23
Output Noise Spectral Density
5
2
3
4
OUTPUT CURRENT (A)
10
5
2
3
4
OUTPUT CURRENT (A)
8028 G22
5
8028 G24
Soft-Start Waveform vs CSS
10
CSS = OPEN
1
CSS = 10nF
CSS = 100nF
500mV/DIV
µV/√Hz
1
Temperature Rise
vs Output Current, 1.8VOUT
60
30
0
8028 G21
Temperature Rise
vs Output Current, 1.5VOUT
40
36VIN
24VIN
12VIN
6VIN
8028 G20
Temperature Rise
vs Output Current, 1.2VOUT
TEMPERATURE RISE (°C)
30
0
5
2
3
4
OUTPUT CURRENT (A)
40
10
TEMPERATURE RISE (°C)
VOUT CHANGE (%)
10
Temperature Rise
vs Output Current, 1VOUT
TEMPERATURE RISE (°C)
15
Output Voltage Change vs MARGA
Voltage, 1VOUT
CSS = 47nF
0.1
0.01
0.001
2ms/DIV
VIN = 12V
5A RESISTIVE LOAD
COUT = 4.7µF + 10µF + 22µF
CBKV = 100µF + 470µF
COUT = 137µF
VOUT = 1.8V
IOUT = 5A
VIN = 12V
10
100
1k
10k
FREQUENCY (Hz)
100k
8028 G26
1M
8028 G25
8028fb
6
For more information www.linear.com/LTM8028
LTM8028
Pin Functions
VOUT (Bank 1): Power Output Pins. Apply the output filter
capacitor and the output load between these and the GND
pins.
BKV (Bank 2): Buck Regulator Output. Apply the step-down
regulator’s bulk capacitance here (refer to Table 1). Do not
connect this to the load. Do not drive a voltage into BKV.
GND (Bank 3): Tie these GND pins to a local ground plane
below the LTM8028 and the circuit components. In most
applications, the bulk of the heat flow out of the LTM8028
is through these pads, so the printed circuit design has a
large impact on the thermal performance of the part. See
the PCB Layout and Thermal Considerations sections for
more details.
VIN (Bank 4): The VIN pin supplies current to the LTM8028’s
internal regulator and to the internal power switch. This
pin must be locally bypassed with an external, low ESR
capacitor; see Table 1 for recommended values.
VO0, VO1, VO2 (Pin A6, Pin B6, Pin A5): Output Voltage
Select. These three-state pins combine to select a nominal
output voltage from 0.8V to 1.8V in increments of 50mV. See
Table 2 in the Applications Information section that defines
the VO2, VO1 and VO0 settings versus VOUT.
MARGA (Pin A7): Analog Margining: This pin margins the
output voltage over a continuous analog range of ±10%.
Tying this pin to GND adjusts output voltage by –10%.
Driving this pin to 1.2V adjusts output voltage by 10%. A
voltage source or a voltage output DAC is ideal for driving
this pin. If the MARGA function is not used, either float
this pin or terminate with a 1nF capacitor to GND.
TEST (Pin A8): Factory Test. Leave this pin open.
SENSEP (Pin A9): Kelvin Sense for VOUT. The SENSEP
pin is the inverting input to the error amplifier. Optimum
regulation is obtained when the SENSEP pin is connected
to the VOUT pins of the regulator. In critical applications, the
resistance of PCB traces between the regulator and the load
can cause small voltage drops, creating a load regulation
error at the point of load. Connecting the SENSEP pin at
the load instead of directly to VOUT eliminates this voltage
error. The SENSEP pin input bias current depends on the
selected output voltage. SENSEP pin input current varies
from 50μA typically at VOUT = 0.8V to 300μA typically at
VOUT = 1.8V. SENSEP must be connected to VOUT, either
locally or remotely.
VOB (Pin B5): Bias for VO0, VO1, VO2. This is a 3.3V source
to conveniently pull up the VO0, VO1, VO2 pins, if desired.
If not used, leave this pin floating.
PGOOD (Pin B7): Power Good. Open drain signal that will
be high impedance if:
• The output rises above 90% of the target voltage
• The output stays above 85% of target voltage
• The output linear regulator does not overheat
Please see the Application Information section for more
details. If not used, tie PGOOD to GND.
IMAX (Pin D1): Sets the Maximum Output Current. Connect a resistor/ NTC thermistor network to the IMAX pin
to reduce the maximum regulated output current of the
LTM8028 in response to temperature. This pin is internally
pulled up to 2V through a 10k resistor, and the control
voltage range is 0V to 1.5V.
SS (Pin D2): The Soft-Start Pin. Place an external capacitor
to ground to limit the regulated current during start-up
conditions. The soft-start pin has an 11μA charging current.
RT (Pin E1): The RT pin is used to program the switching
frequency of the LTM8028’s buck regulator by connecting a resistor from this pin to ground. The Applications
Information section of the data sheet includes a table
to determine the resistance value based on the desired
switching frequency. When using the SYNC function,
set the frequency to be 20% lower than the SYNC pulse
frequency. Do not leave this pin open.
8028fb
For more information www.linear.com/LTM8028
7
LTM8028
Pin Functions
SYNC (Pin E2): Frequency Synchronization Pin. This pin
allows the switching frequency to be synchronized to an
external clock. The RT resistor should be chosen to operate the internal clock at 20% slower than the SYNC pulse
frequency. This pin should be grounded when not in use.
Do not leave this pin floating. When laying out the board,
avoid noise coupling to or from the SYNC trace. See the
Synchronization section in Applications Information.
RUN (Pin F1): The RUN pin acts as an enable pin and
turns off the internal circuitry at 1.55V. The pin does not
have any pull-up or pull-down, requiring a voltage bias for
normal part operation. The RUN pin is internally clamped,
so it may be pulled up to a voltage source that is higher
than the absolute maximum voltage of 6V, provided the
pin current does not exceed 100μA.
Block Diagram
2.2µH
VIN
0.2µF
BKV
VOUT
10Ω
SENSEP
10µF
5A LINEAR
REGULATOR
TEST
MARGA
PGOOD
RUN
SYNC
IMAX
INPUT-OUTPUT
CONTROL
CURRENT
MODE
CONTROLLER
SS
RT
VIN
INTERNAL
POWER
VOB
GND
VO2
VO1
VO0
8028 BD
8028fb
8
For more information www.linear.com/LTM8028
LTM8028
Operation
Current generation FPGA and ASIC processors place
stringent demands on the power supplies that power the
core, I/O and transceiver channels. Power supplies that
power these processors have demanding output voltage
specifications, especially at low voltages, where they
require tight tolerances, small transient response excursions, low noise and high bandwidth to achieve the lowest
bit-error rates. This can be accomplished with some high
performance linear regulators, but this can be inefficient
for high current and step-down ratios.
The LTM8028 is a 5A high efficiency, UltraFast transient
response linear regulator. It integrates a buck regulator with
a high performance linear regulator, providing a precisely
regulated output voltage digitally programmable from 0.8V
to 1.8V. As shown in the Block Diagram, the LTM8028
contains a current mode controller, power switches,
power inductor, linear regulator, and a modest amount
of capacitance. To achieve high efficiency, the integrated
buck regulator is automatically controlled (Input-Output
Control on the Block Diagram) to produce the optimal
voltage headroom to balance efficiency, tight regulation
and transient response at the linear regulator output.
Figure 1 is a composite graph of the LTM8028’s power
loss compared to the theoretical power loss of a traditional
linear regulator. Note that the power loss (left hand Y axis)
is plotted on the log scale. For 1.2VOUT at 5A and 24VIN
60
1000
55
50
100
45
TEMPERATURE RISE
10
40
POWER LOSS
TEMPERATURE RISE (°C)
POWER LOSS (W)
TRADITIONAL LINEAR
REGULATOR POWER LOSS
35
0
0
10
20
30
INPUT VOLTAGE (V)
40
30
8028 F01
Figure 1. This Graph Shows the Full Load Power Loss and
Temperature Rise of the LTM8028 over a Range of Input
Voltages. Compare These Numbers to a Traditional Linear
Regulator Powering the Same Load an Operating Condition.
Note the Log Scale for Power Loss.
the LTM8028 only loses 4W, while the traditional linear
regulator theoretically dissipates over 110W.
The LTM8028 switching buck converter utilizes fixedfrequency, forced continuous current mode control to
regulate its output voltage. This means that the switching
regulator will stay in fixed frequency operation even as the
LTM8028 output current falls to zero. The LTM8028 has
an analog control pin, IMAX, to set the maximum allowable current output of the LTM8028. The analog control
range of IMAX is from 0V to 1.5V. The RUN pin functions
as a precision shutdown pin. When the voltage at the RUN
pin is lower than 1.55V, switching is terminated. Below
this threshold, the RUN pin sinks 5.5µA. This current can
be used with a resistor between RUN and VIN to set the
hysteresis. During start-up, the SS pin is held low until the
part is enabled, after which the capacitor at the soft-start
pin is charged with an 11μA current source. The switching
frequency is determined by a resistor at the RT pin. The
LTM8028 may also be synchronized to an external clock
through the use of the SYNC pin.
The output linear regulator supplies up to 5A of output
current with a typical dropout voltage of 85mV. Its high
bandwidth provides UltraFast transient response using low
ESR ceramic output capacitors, saving bulk capacitance,
PCB area and cost. The output voltage for the LTM8028
is digitally selectable in 50mV increments over a 0.8V to
1.8V range, and analog margining function allows the user
to adjust system output voltage over a continuous ±10%
range. It also features a remote sense pin for accurate
regulation at the load, and a PGOOD circuit that indicates
whether the output is in or out of regulation or if an internal
fault has occurred.
The LTM8028 is equipped with a thermal shutdown to
protect the device during momentary overload conditions.
It is set above the 125°C absolute maximum internal temperature rating to avoid interfering with normal specified
operation, so internal device temperatures will exceed
the absolute maximum rating when the overtemperature
protection is active. So, continuous or repeated activation
of the thermal shutdown may impair device reliability.
During thermal shutdown, all switching is terminated and
the SS pin is driven low.
8028fb
For more information www.linear.com/LTM8028
9
LTM8028
Applications Information
For most applications, the design process is straight
forward, summarized as follows:
1. Look at Table 1 and find the row that has the desired
input range and output voltage.
2. Apply 10μF to VIN and the recommended RT value
(RT(OPTIMAL) in Table 1). Lower RT values (resulting in
a higher operating frequency) may be used to reduce
the output ripple. Do not use values below RT(MIN).
3. Apply a parallel combination of a 100μF ceramic and
a 470μF electrolytic to BKV. The Sanyo OS-CON 6SEPC470M or United Chemi-Con APXF6R3ARA471MH80G
work well for the electrolytic capacitor, but other devices
with an ESR about 10mΩ may be used.
4. Apply a minimum of 37μF to VOUT. As shown in Table 1,
this is usually a parallel combination of 4.7μF, 10μF and
22μF capacitors.
5. Apply an additional 100µF capacitor to VOUT if very
small (2%) transient response is required.
While these component combinations have been tested
for proper operation, it is incumbent upon the user to
verify proper operation over the intended system’s line,
load and environmental conditions. Bear in mind that the
maximum output current is limited by junction temperature, the relationship between the input and output voltage
magnitude and polarity and other factors. Please refer to
the graphs in the Typical Performance Characteristics
section for guidance.
The maximum frequency (and attendant RT value) at
which the LTM8028 should be allowed to switch is given
in Table 1 in the fMAX column, while the recommended
frequency (and RT value) for optimal efficiency over the
given input condition is given in the fOPTIMAL column.
There are additional conditions that must be satisfied if
the synchronization function is used. Please refer to the
Synchronization section for details.
Programming Output Voltage
Three tri-level input pins, VO2, VO1 and VO0, select the value
of output voltage. Table 2 illustrates the 3-bit digital wordto-output voltage resulting from setting these pins high,
low or allowing them to float. These pins may be tied high
or low by either pin-strapping them to VOB or driving them
Table 1: Recommended Component Values and Configuration (TA = 25°C)
VIN
6V to 36V
6V to 36V
6V to 36V
6V to 36V
6V to 36V
9V to 15V
9V to 15V
9V to 15V
9V to 15V
9V to 15V
18V to 36V
18V to 36V
18V to 36V
18V to 36V
18V to 36V
VOUT
0.8V
1.0V
1.2V
1.5V
1.8V
0.8V
1.0V
1.2V
1.5V
1.8V
0.8V
1.0V
1.2V
1.5V
1.8V
CIN:
CBKV:
COUT:
COUT (Optional):
Note: An input bulk capacitor is required.
10
fOPTIMAL
RT(OPTIMAL)
200kHz
200k
250kHz
165k
250kHz
165k
250kHz
165k
315kHz
133k
250kHz
165k
280kHz
150k
300kHz
143k
315kHz
133k
350kHz
118k
200kHz
200k
250kHz
165k
250kHz
165k
250kHz
165k
315kHz
133k
10µF, 50V, 1210
100µF, 6.3V, 1210 + 470µF, 6.3V Low ESR Electrolytic
4.7µF, 4V, 0603 + 10µF, 10V, 0805 + 22µF, 10V, 0805
100µF, 6.3V, 1210
fMAX
250kHz
280kHz
315kHz
333kHz
385kHz
650kHz
750kHz
800kHz
1MHz
1MHz
250kHz
280kHz
315kHz
333kHz
385kHz
RT(MIN)
165k
150k
133k
127k
107k
61.9k
53.6k
49.9k
40.2k
40.2k
165k
150k
133k
127k
107k
8028fb
For more information www.linear.com/LTM8028
LTM8028
Applications Information
with digital ports. Pins that float may either actually float
or require logic that has Hi-Z output capability. This allows
the output voltage to be dynamically changed if necessary.
The output voltage is selectable from a minimum of 0.8V
to a maximum of 1.8V in increments of 50mV.
Table 2. VO2 to VO0 Setting vs Output Voltage
VO2
VO1
VO0
VOUT(NOM)
VO2
VO1
VO0
VOUT(NOM)
0
0
0
0.80V
Z
0
1
1.35V
0
0
Z
0.85V
Z
Z
0
1.40V
0
0
1
0.90V
Z
Z
Z
1.45V
0
Z
0
0.95V
Z
Z
1
1.50V
0
Z
Z
1.00V
Z
1
0
1.55V
0
Z
1
1.05V
Z
1
Z
1.60V
0
1
0
1.10V
Z
1
1
1.65V
0
1
Z
1.15V
1
X
0
1.70V
0
1
1
1.20V
1
X
Z
1.75V
Z
0
0
1.25V
1
X
1
1.80V
Z
0
Z
1.30V
The output capacitance for BKV given in Table 1 specifies
an electrolytic capacitor. Ceramic capacitors may also be
used in the application, but it may be necessary to use
more of them. Many high value ceramic capacitors have
a large voltage coefficient, so the actual capacitance of
the component at the desired operating voltage may be
only a fraction of the specified value. Also, the very low
ESR of ceramic capacitors may necessitate an additional
capacitor for acceptable stability margin.
A final precaution regarding ceramic capacitors concerns
the maximum input voltage rating of the LTM8028. A
ceramic input capacitor combined with trace or cable
inductance forms a high Q (under damped) tank circuit.
If the LTM8028 circuit is plugged into a live supply, the
input voltage can ring to twice its nominal value, possibly exceeding the device’s rating. This situation is easily
avoided; see the Hot-Plugging Safely section.
Why Do Multiple, Small Value Output Capacitors
Connected in Parallel Work Better?
X = Don’t Care, 0 = Low, Z = Float, 1 = High
Capacitor Selection Considerations
The CIN, CBKV and COUT capacitor values in Table 1 are the
minimum recommended values for the associated operating 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.
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 applied voltage and give dependable service. Other types,
including Y5V and Z5U have very large temperature and
voltage coefficients of capacitance. In an application circuit they may have only a small fraction of their nominal
capacitance resulting in much higher output voltage ripple
than expected.
The parasitic series inductance (ESL) and resistance
(ESR) of a capacitor can have a detrimental impact on the
transient and ripple/noise response of a linear regulator.
Employing a number of capacitors in parallel will reduce
this parasitic impedance and improve the performance of
the linear regulator. In addition, PCB vias can add significant
inductance, so the fundamental decoupling capacitors must
be mounted on the same copper plane as the LTM8028.
The most area efficient parallel capacitor combination is
a graduated 4/2/1 scale capacitances of the same case
size, such as the 37μF combination in Table 1, made up
of 22μF, 10μF and 4.7μF capacitors in parallel. Capacitors
with small case sizes have larger ESR, while those with
larger case sizes have larger ESL. As seen in Table 1, the
optimum case size is 0805, followed by a larger, fourth
bulk energy capacitor, case sized 1210. In general, the
large fourth capacitor is required only if very tight transient
response is required.
8028fb
For more information www.linear.com/LTM8028
11
LTM8028
Applications Information
Output Voltage Margining
The LTM8028’s analog margining pin, MARGA, provides a
continuous output voltage adjustment range of ±10%. It
margins VOUT by adjusting the internal 600mV reference
voltage up and down. Driving MARGA with 600mV to
1.2V provides 0% to 10% of adjustment. Driving MARGA
with 600mV to 0V provides 0% to –10% of adjustment.
If unused, allow MARGA to float or bypass this pin with
a 1nF capacitor to GND. Note that the analog margining
function does not adjust the PGOOD threshold. Therefore,
negative analog margining may trip the PGOOD comparator
and toggle the PGOOD flag.
Power Good
PGOOD pin is an open-drain NMOS digital output that actively pulls low if any one of these fault modes is detected:
• VOUT is less than 90% of VOUT(NOMINAL) on the rising
edge of VOUT.
• VOUT drops below 85% of VOUT(NOMINAL) for more than
25μs.
• Internal faults such as loss of internal housekeeping
voltage regulation, reverse-current on the power switch
and excessive temperature.
SENSEP and Load Regulation
The LTM8028 provides a Kelvin sense pin for VOUT, allowing
the application to correct for parasitic package and PCB
IR drops. If the load is far from the LTM8028, running a
separate line from SENSEP to the remote load will correct
for IR voltage drops and improve load regulation. SENSEP
is the only voltage feedback that the LTM8028 uses to
regulate the output, so it must be connected to VOUT, either
locally or at the load. In some systems, a loss of feedback
signal equates to a loss of output control, potentially
damaging the load. If the SENSEP signal is inadvertently
disconnected from the load, internal safety circuits in the
LTM8028 prevent the output from running away. This also
limits the amount of correction to about 0.2V.
Bear in mind that the linear regulator of the LTM8028
is a high bandwidth power device. If the load is very far
from the LTM8028, the parasitic impedance of the remote
connection may interfere with the internal control loop
and adversely affect stability. If SENSEP is connected to
a remote load, the user must evaluate the load regulation
and dynamic load response of the LTM8028.
Short-Circuit and Overload Recovery
Like many IC power regulators, the internal linear regulator
has safe operating area (SOA) protection. The safe area
protection decreases current limit as input-to-output voltage increases and keeps the power transistor inside a safe
operating region for all values of input-to-output voltage
up to the absolute maximum voltage rating.
Under maximum ILOAD and maximum VIN-VOUT conditions,
the internal linear regulator’s power dissipation peaks at
about 1.5W. If ambient temperature is high enough, die
junction temperature will exceed the 125°C maximum
operating temperature. If this occurs, the LTM8028 relies
on two additional thermal safety features. At about 145°C,
the device is designed to make the PGOOD output pull
low providing an early warning of an impending thermal
shutdown condition. At 165°C typically, the LTM8028 is
designed to engage its thermal shutdown and the output
is turned off until the IC temperature falls below the
thermal hysteresis limit. The SOA protection decreases
current limit as the in-to-out voltage increases and keeps
the power dissipation at safe levels for all values of inputto-output voltage.
8028fb
12
For more information www.linear.com/LTM8028
LTM8028
Applications Information
Reverse Voltage
Switching Frequency Synchronization
The LTM8028 incorporates a circuit that detects if BKV
decreases below VOUT. If this voltage condition is detected,
internal circuitry turns off the drive to the internal linear
regulator’s pass transistor, thereby turning off the output.
This circuit’s intent is to limit and prevent back-feed current
from VOUT to VIN if the input voltage collapses due to a
fault or overload condition. Do not apply a voltage to BKV.
The nominal switching frequency of the LTM8028 is
determined by the resistor from the RT pin to GND and
may be set from 200kHz to 1MHz. The internal oscillator
may also be synchronized to an external clock through
the SYNC pin. The external clock applied to the SYNC pin
must have a logic low below 0.25V and a logic high greater
than 1.25V. The input frequency must be 20% higher than
the frequency determined by the resistor at the RT pin.
The duty cycle of the input signal needs to be greater than
10% and less than 90%. Input signals outside of these
specified parameters will cause erratic switching behavior
and subharmonic oscillations. When synchronizing to an
external clock, please be aware that there will be a fixed
delay from the input clock edge to the edge of switch. The
SYNC pin must be tied to GND if the synchronization to an
external clock is not required. When SYNC is grounded,
the switching frequency is determined by the resistor at
the RT pin.
Programming Switching Frequency
The LTM8028 has an operational switching frequency range
between 200kHz and 1MHz. This frequency is programmed
with an external resistor from the RT pin to ground. Do
not leave this pin open under any condition. The RT pin
is also current limited to 60μA. See Table 3 for resistor
values and the corresponding switching frequencies.
Table 3. RT Resistor Values and Their Resultant Switching
Frequencies
SWITCHING FREQUENCY (MHz)
1
0.750
0.5
0.3
0.2
RT (kΩ)
40.2
53.6
82.5
143
200
Switching Frequency Trade-Offs
It is recommended that the user apply the optimal RT value
given in Table 1 for the input and output operating condition. System level or other considerations, however, may
necessitate another operating frequency. A higher switching
frequency, for example, will yield a smaller output ripple,
while a lower frequency will reduce power loss. Switching too fast, however, can generate excessive heat and
even possibly damage the LTM8028 in fault conditions.
Switching too slow can result in a final design that has too
much output capacitance or sub-harmonic oscillations that
cause excessive ripple. In all cases, stay below the stated
maximum frequency (fMAX) given in Table 1.
Soft-Start
The soft-start function controls the slew rate of the power
supply output voltage during start-up. A controlled output
voltage ramp minimizes output voltage overshoot, reduces
inrush current from the VIN supply, and facilitates supply
sequencing. A capacitor connected from the SS pin to
GND programs the slew rate. The capacitor is charged
from an internal 11μA current source to produce a ramped
output voltage.
Maximum Output Current Adjust
To adjust the regulated load current, an analog voltage
is applied to the IMAX pin. Varying the voltage between
0V and 1.5V adjusts the maximum current between the
minimum and the maximum current, 5.6A typical. Above
1.5V, the control voltage has little effect on the regulated
inductor current. A graph of the output current versus IMAX
voltage is given in the Typical Performance Characteristics
8028fb
For more information www.linear.com/LTM8028
13
LTM8028
Applications Information
section. There is a 10k resistor internally connected from
a 2V reference to the IMAX pin, so the current limit can
be set as shown in Figure 2 with the following equation:
RIMAX =
10 •IMAX
kΩ
7.467 –IMAX
LTM8028
IMAX
LTM8028 when the RUN pin voltage falls to 1.55V. There
is also an internal current source that provides 5.5μA of
pull-down current to program additional UVLO hysteresis.
For RUN rising, the current source is sinking 5.5µA until
RUN = 1.68V, after which it turns off. For RUN falling, the
current source is off until the RUN = 1.55V, after which it
sinks 5.5µA. The following equations determine the voltage
divider resistors for programming the falling UVLO voltage
and rising enable voltage (VENA) as configured in Figure 3.
 1.55 •R2 
R1= 
 UVLO – 1.55 
RIMAX
8028 F02
Figure 2. Setting The Output Current Limit, IMAX
Thermal Shutdown
At about 145°C, the LTM8028 is designed to make the
PGOOD output pull low providing an early warning of
an impending thermal shutdown condition. At 165°C
typically, the LTM8028 is designed to engage its thermal
shutdown, discharge the soft-start capacitor and turn off
the output until the internal temperature falls below the
thermal hysteresis limit. When the part has cooled, the part
automatically restarts. Note that this thermal shutdown is
set to engage at temperatures above the 125°C absolute
maximum internal operating rating to ensure that it does
not interfere with functionality in the specified operating
range. This means that internal temperatures will exceed the
125°C absolute maximum rating when the overtemperature
protection is active, so repeated or prolonged operation
under these conditions may impair the device’s reliability.
UVLO and Shutdown
The LTM8028 has an internal UVLO that terminates switching, resets all logic, and discharges the soft-start capacitor
for input voltages below 4.2V. The LTM8028 also has a
precision RUN function that enables switching when the
voltage at the RUN pin rises to 1.68V and shuts down the
R2 =
VENA – 1.084 •UVLO
5.5µA
VIN
LTM8028
VIN
R2
RUN
R1
8028 F03
Figure 3. UVLO Configuration
The RUN pin has an absolute maximum voltage of 6V.
To accommodate the largest range of applications, there
is an internal Zener diode that clamps this pin, so that it
can be pulled up to a voltage higher than 6V through a
resistor that limits the current to less than 100µA. For
applications where the supply range is greater than 4:1,
size R2 greater than 375k.
PCB Layout
Most of the headaches associated with PCB layout have
been alleviated or even eliminated by the high level of
integration of the LTM8028. The LTM8028 is nevertheless a switching power supply, and care must be taken to
8028fb
14
For more information www.linear.com/LTM8028
LTM8028
Applications Information
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 4
for a suggested layout. Ensure that the grounding and
heat sinking are acceptable.
A few rules to keep in mind are:
1. Place the RT resistor as close as possible to its respective pins.
2. Place the CIN capacitor as close as possible to the VIN
and GND connection of the LTM8028.
3. Place the COUT capacitors as close as possible to the
VOUT and GND connection of the LTM8028.
4. Place the CIN, CBKV and COUT capacitors such that their
ground current flow directly adjacent or underneath the
LTM8028.
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 LTM8028.
6. 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 4. The LTM8028 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.
GND
COUT
CBKV
BKV
VOUT
SENSEP
TEST
MARGA
PGOOD
VO0
(OUTPUT IS
VO1
SET TO 1.55V)
VO2
VOB
GND
SS SYNC
IMAX RT RUN
GND
THERMAL VIAS
VIN
CIN
8028 F04
Figure 4. Layout Showing Suggested External Components, GND Plane and Thermal Vias
8028fb
For more information www.linear.com/LTM8028
15
LTM8028
Applications Information
Load Sharing
Hot-Plugging Safely
Each LTM8028 features an accurate current limit that enables the use of multiple devices to power a load heavier
than 5A. This is accomplished by simply tying the VOUT
terminals of the LTM8028s together, and set the outputs of
the parallel units to the same voltage. There is no need to
power the μModule regulators from the same power supply.
That is, the application can use multiple LTM8028s, each
powered from separate input voltage rails and contribute
a different amount of current to the load as dictated by the
programmed current limit. Keep in mind that the paralleled
LTM8028s will not share current equally. In most cases, one
LTM8028 will provide almost all the load until its current
limit is reached, and then the other unit or units will start
to provide current. This might be an unacceptable operating condition in other power regulators, but the accurate
current loop of the LTM8028 controls the electrical and
thermal performance of each individual μModule regulator.
This prevents the oscillations, thermal runaway and other
issues that other regulators might suffer. An example of
two LTM8028s connected in parallel to deliver 1.8V at
10A, while powered from two disparate power sources,
is given in the Typical Applications section. A graph of the
output current delivered from each μModule regulator is
given below in Figure 5.
The small size, robustness and low impedance of ceramic
capacitors make them an attractive option for the input
bypass capacitor of LTM8028. However, these capacitors
can cause problems if the LTM8028 is plugged into a live
input supply (see 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 voltage at the VIN pin
of the LTM8028 can ring to more than twice the nominal
input voltage, possibly exceeding the LTM8028’s rating
and damaging the part. If the input supply is poorly controlled or the user will be plugging the LTM8028 into an
energized supply, the input network should be designed
to prevent this overshoot. This can be accomplished by
installing a small resistor in series to VIN, but the most
popular method of controlling input voltage overshoot is
to add an electrolytic bulk capacitor to the VIN net. This
capacitor’s relatively high equivalent series resistance
damps the circuit and eliminates the voltage overshoot.
The extra capacitor improves low frequency ripple filtering and can slightly improve the efficiency of the circuit,
though it is physically large.
CURRENT DELIVERED BY LTM8028s (A)
6
5
4
3
2
1
0
1
2
4
6
8
TOTAL LOAD CURRENT (A)
10
8028 F05
Figure 5. In Most Cases Where Paralleled LTM8028s are
Used, One µModule Will Deliver All of The Load Current Until
Its Current Limit Is Reached, Then The Other Unit(s) Will
Provide Current. The Tightly Controlled Output Current Prevents
Oscillations and Thermal Runaway Observed In Other Types of
Regulators
8028fb
16
For more information www.linear.com/LTM8028
LTM8028
Applications Information
Thermal Considerations
The LTM8028 relies on two thermal safety features. At about
145°C, the device is designed to pull the PGOOD output
low providing an early warning of an impending thermal
shutdown condition. At 165°C typically, the LTM8028 is
designed to engage its thermal shutdown and the output is
turned off until the IC temperature falls below the thermal
hysteresis limit. Note that these temperature thresholds
are above the 125°C absolute maximum rating to avoid
interfering with normal operation. Thus, prolonged or
repetitive operation under a condition in which the thermal
shutdown activates may damage or impair the reliability
of the device.
The LTM8028 output current may need to be derated if it
is required to operate in a high ambient temperature. 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
Characteristics section can be used as a guide. These curves
were generated by the LTM8028 mounted to a 58cm2
4-layer FR4 printed circuit board. Boards of other sizes
and layer count can exhibit different thermal behavior, so
it is incumbent upon the user to verify proper operation
over the intended system’s line, load and environmental
operating conditions.
For increased accuracy and fidelity to the actual application,
many designers use finite element analysis (FEA) to predict
thermal performance. To that end, the Pin Configuration
of the data sheet typically gives four thermal coefficients:
θJA – Thermal resistance from junction to ambient
θJCbottom – Thermal resistance from junction to the bottom
of the product case
θJCtop – Thermal resistance from junction to top of the
product case
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:
θJA is the natural convection junction-to-ambient air
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.
θJCbottom is the junction-to-board thermal resistance with
all of the component power dissipation flowing through the
bottom of the package. In the typical µModule regulator,
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.
θJCtop is determined with nearly all of the component power
dissipation flowing through the top of the package. As the
electrical connections of the typical µModule regulator are
on the bottom of the package, it is rare for an application
to operate such that most of the heat flows from the junction to the top of the part. As in the case of θJCbottom, this
value may be useful for comparing packages but the test
conditions don’t generally match the user’s application.
θJB is the junction-to-board thermal resistance where
almost all of the heat flows through the bottom of the
µModule regulator and into the board, and is really the
sum of the θJCbottom and the thermal resistance of the
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.
θJBoard – Thermal resistance from junction to the printed
circuit board.
8028fb
For more information www.linear.com/LTM8028
17
LTM8028
Applications Information
Given these definitions, it should now be apparent that none
of these thermal coefficients reflects an actual physical
operating condition of a µModule regulator. Thus, none
of them can be individually used to accurately predict the
thermal performance of the product. Likewise, it would
be inappropriate to attempt to use any one coefficient to
correlate to the junction temperature vs load graphs given
in the product’s data sheet. The only appropriate way to
use the coefficients is when running a detailed thermal
analysis, such as FEA, which considers all of the thermal
resistances simultaneously.
A graphical representation of these thermal resistances
is given in Figure 6:
The blue resistances are contained within the µModule
regulator, and the green are outside.
The die temperature of the LTM8028 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
LTM8028. The bulk of the heat flow out of the LTM8028
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, resulting in impaired performance or reliability. Please refer to
the PCB Layout section for printed circuit board design
suggestions.
JUNCTION-TO-AMBIENT RESISTANCE (JESD 51-9 DEFINED BOARD)
CASE (TOP)-TO-AMBIENT
RESISTANCE
JUNCTION-TO-CASE (TOP)
RESISTANCE
JUNCTION-TO-BOARD RESISTANCE
JUNCTION
AMBIENT
JUNCTION-TO-CASE
CASE (BOTTOM)-TO-BOARD
(BOTTOM) RESISTANCE
RESISTANCE
BOARD-TO-AMBIENT
RESISTANCE
8028 F06
µMODULE DEVICE
Figure 6. Thermal Model of µModule
Typical Applications
Transient Response from 0.5A to 5A, 1µs
Load Current Rise and Fall Time, 12VIN
1V at 5A Regulator with 2% Transient Response
VIN
6V TO 36V
LTM8028
VIN
402k
10µF
0.01µF
RUN
MARGA
IMAX
BKV
SS
165k
RT
VOUT
1V
5A
VOUT
LINEAR
REGULATOR SENSEP
PGOOD
SYNC
GND
VOB VO0 VO1 VO2
137µF*
+
100µF
LOAD
CURRENT
2A/DIV
VOUT
20mV/DIV
470µF
8028 TA02
1µs/DIV
8028 TA03
*137µF = 4.7µF + 10µF + 22µF +100µF IN PARALLEL
8028fb
18
For more information www.linear.com/LTM8028
LTM8028
Typical Applications
Output Voltage vs Current
1.8V Regulator with 3.5A Current Limit
2.0
1.8
10µF
VIN
402k
10k
VOUT
LINEAR
REGULATOR SENSEP
RUN
MARGA
IMAX
RT
1.6
BKV
SS
0.01µF 133k
VOUT
1.8V
3.5A
OUTPUT VOLTAGE (V)
VIN
6V TO 36V
LTM8028
PGOOD
GND
SYNC
37µF*
VOB VO0 VO1 VO2
+
100µF
1.4
1.2
1.0
0.8
0.6
0.4
470µF
0.2
8028 TA04
0
*37µF = 4.7µF + 10µF + 22µF IN PARALLEL
0
2
1
3
OUTPUT CURRENT (A)
4
8028 TA05
1.8V, 10A with Two LTM8028s Powered from Two Different Sources Each µModule Regulator
Is Limited to Provide a Maximum of 5A
VIN
24V
10µF
LTM8028
VIN
402k
20.5k
RUN
MARGA
BKV
IMAX
SS
0.01µF 133k
VIN
12V
10µF
RT
PGOOD
SYNC
20.5k
GND
LTM8028
VIN
150k
RUN
MARGA
VOB VO0 VO1 VO2
+
100µF
330µF
BKV
IMAX
RT
17µF*
VOUT
LINEAR
REGULATOR SENSEP
SS
0.01µF 133k
VOUT
1.8V
10A
VOUT
LINEAR
REGULATOR SENSEP
PGOOD
SYNC
GND
VOB VO0 VO1 VO2
17µF*
+
100µF
330µF
8028 TA06
*17µF = 2.2µF + 4.7µF + 10µF IN PARALLEL
8028fb
For more information www.linear.com/LTM8028
19
LTM8028
Typical Applications
Low Noise LTM8028 Powering 16-Bit, 125Msps ADC
VIN
6V TO 36V
LTM8028
VIN
402k
10µF
0.01µF
RUN
MARGA
IMAX
BKV
SS
133k
RT
VOUT
1.8V
5A
VOUT
LINEAR
REGULATOR SENSEP
PGOOD
GND
SYNC
VOB VO0 VO1 VO2
VDD
AIN+
137µF*
+
LTC®2185 ADC
AIN–
100µF
470µF
OVDD
ENC+ ENC– GND
1.8V
0V
8028 TA08a
*137µF = 4.7µF + 10µF + 22µF + 100µF IN PARALLEL
32k-Point FFT, fIN = 70.3MHz, –1dBFS, 100Msps
0
–10
–20
MAGNITUDE (dBFS)
–30
–40
–50
–60
–70
–80
–90
–100
–110
–120
0
10
30
20
FREQUENCY (MHz)
40
50
8028 TA08b
8028fb
20
For more information www.linear.com/LTM8028
LTM8028
Package Description
Table 3. Pin Assignment Table
(Arranged by Pin Number)
PIN
A1
A2
A3
A4
A5
A6
A7
A8
A9
A10
A11
NAME
GND
GND
GND
GND
VO2
VO0
MARGA
TEST
SENSEP
VOUT
VOUT
PIN
B1
B2
B3
B4
B5
B6
B7
B8
B9
B10
B11
NAME
GND
GND
GND
GND
VOB
VO1
PGOOD
GND
GND
VOUT
VOUT
PIN
C1
C2
C3
C4
C5
C6
C7
C8
C9
C10
C11
NAME
GND
GND
GND
GND
GND
GND
GND
GND
GND
VOUT
VOUT
PIN
D1
D2
D3
D4
D5
D6
D7
D8
D9
D10
D11
NAME
IMAX
SS
GND
GND
GND
GND
GND
GND
GND
VOUT
VOUT
PIN
E1
E2
E3
E4
E5
E6
E7
E8
E9
E10
E11
NAME
RT
SYNC
GND
GND
GND
GND
GND
GND
GND
VOUT
VOUT
PIN
G1
G2
G3
G4
G5
G6
G7
G8
G9
G10
G11
NAME
–
–
–
GND
GND
GND
GND
GND
GND
GND
GND
PIN
H1
H2
H3
H4
H5
H6
H7
H8
H9
H10
H11
NAME
VIN
VIN
–
GND
GND
GND
GND
GND
GND
GND
GND
PIN
J1
J2
J3
J4
J5
J6
J7
J8
J9
J10
J11
NAME
VIN
VIN
–
GND
GND
GND
GND
GND
BKV
BKV
BKV
PIN
K1
K2
K3
K4
K5
K6
K7
K8
K9
K10
K11
NAM
VIN
VIN
–
GND
GND
GND
GND
GND
BKV
BKV
BKV
PIN
L1
L2
L3
L4
L5
L6
L7
L8
L9
L10
L11
NAME
VIN
VIN
–
GND
GND
GND
GND
GND
BKV
BKV
BKV
PIN
F1
F2
F3
F4
F5
F6
F7
F8
F9
F10
D11
NAME
RUN
GND
GND
GND
GND
GND
GND
GND
GND
VOUT
VOUT
Package Photo
8028fb
For more information www.linear.com/LTM8028
21
aaa Z
0.630 ±0.025 Ø 114x
E
2.540
SUGGESTED PCB LAYOUT
TOP VIEW
2.540
PACKAGE TOP VIEW
1.270
4
0.000
PAD “A1”
CORNER
1.270
22
Y
For more information www.linear.com/LTM8028
6.350
5.080
3.810
2.540
1.270
0.000
1.270
2.540
3.810
5.080
6.350
X
D
3.95 – 4.05
aaa Z
SYMBOL
A
A1
A2
b
b1
D
E
e
F
G
aaa
bbb
ccc
ddd
eee
NOM
4.92
0.60
4.32
0.75
0.63
15.0
15.0
1.27
12.70
12.70
DIMENSIONS
0.15
0.10
0.20
0.30
0.15
MAX
5.12
0.70
4.42
0.90
0.66
NOTES
DETAIL B
PACKAGE SIDE VIEW
TOTAL NUMBER OF BALLS: 114
MIN
4.72
0.50
4.22
0.60
0.60
DETAIL A
b1
0.27 – 0.37
SUBSTRATE
A1
ddd M Z X Y
eee M Z
DETAIL B
MOLD
CAP
ccc Z
A2
A
Z
(Reference LTC DWG # 05-08-1894 Rev A)
Øb (114 PLACES)
// bbb Z
BGA Package
114-Lead (15mm × 15mm × 4.92mm)
F
e
b
b
10
9
7
G
6
5
e
4
PACKAGE BOTTOM VIEW
8
3
2
1
DETAILS OF PAD #1 IDENTIFIER ARE OPTIONAL,
BUT MUST BE LOCATED WITHIN THE ZONE INDICATED.
THE PAD #1 IDENTIFIER MAY BE EITHER A MOLD OR
MARKED FEATURE
4
TRAY PIN 1
BEVEL
COMPONENT
PIN “A1”
7
!
PACKAGE IN TRAY LOADING ORIENTATION
LTMXXXXXX
µModule
PAD 1
BGA 114 1112 REV A
3
7
SEE NOTES
SEE NOTES
L
K
J
H
G
F
E
D
C
B
A
PACKAGE ROW AND COLUMN LABELING MAY VARY
AMONG µModule PRODUCTS. REVIEW EACH PACKAGE
LAYOUT CAREFULLY
6. THE TOTAL NUMBER OF PADS: 114
5. PRIMARY DATUM -Z- IS SEATING PLANE
LAND DESIGNATION PER JESD MO-222, SPP-010
3
2. ALL DIMENSIONS ARE IN MILLIMETERS
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME Y14.5M-1994
11
DETAIL A
LTM8028
Package Description
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
8028fb
6.350
5.080
3.810
3.810
5.080
6.350
LTM8028
Revision History
REV
DATE
DESCRIPTION
PAGE NUMBER
A
2/14
Added SnPb BGA package option
B
5/14
1, 2
SYNC Input Threshold MIN: from 0.8V to 0.6V; MAX: from 1.2V to 1.3V
3
Add PGOOD description
7
8028fb
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 representation that the interconnection
of its circuits
as described
herein will not infringe on existing patent rights.
For more
information
www.linear.com/LTM8028
23
LTM8028
Typical Application
1V at 5A Regulator
VIN
6V TO 36V
LTM8028
VIN
402k
10µF
0.01µF
RUN
MARGA
IMAX
BKV
SS
165k
RT
VOUT
1V
5A
VOUT
LINEAR
REGULATOR SENSEP
PGOOD
SYNC
GND
VOB VO0 VO1 VO2
37µF*
+
100µF
470µF
8028 TA07
*37µF = 4.7µF + 10µF + 22µF IN PARALLEL
Related Parts
PART NUMBER
DESCRIPTION
COMMENTS
LTM8032
Step-Down µModule Regulator, EN55022B Compliant
3.6V ≤ VIN ≤ 36V, 0.8V ≤ VOUT ≤ 10V, 2A
LTM4613
Step-Down µModule Regulator, EN55022B Compliant
5V ≤ VIN ≤ 36V, 3.3V ≤ VOUT ≤ 15V, 8A
LTM8027
60V, 4A Step-Down µModule Regulator
4.5V ≤ VIN ≤ 60V, 2.5V ≤ VOUT ≤ 24V, 4A
LTM8048
Isolated µModule Converter
725V Isolation, 3.1V ≤ VIN ≤ 32V, 1.2V ≤ VOUT ≤ 12V, 300mA
LTM4615
Triple Output Step-Down µModule Regulator
2.375V ≤ VIN ≤ 5.5V, 0.8V ≤ VOUT ≤ 5.5V, 4A, 4A, 1.5A
LTM4620
Dual 13A, Single 26A Step-Down µModule Regulator
4.5V ≤ VIN ≤ 16V, 0.6V ≤ VOUT ≤ 2.5V, Up to 100A Current Sharing
8028fb
24
Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LTM8028
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LTM8028
LT 0614 REV B • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 2013