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PDF LTM8028 Data sheet ( Hoja de datos )
| Número de pieza | LTM8028 | |
| Descripción | Low Output Noise 5A uModule Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTM8028
36VIN, UltraFast,
Low Output Noise 5A
µModule Regulator
Features
n High Performance 5A Linear Regulator with
Switching Step-Down Converter for High Efficiency
n Digitally Programmable VOUT: 0.8V to 1.8V
n Input Voltage Range: 6V to 36V
n Very Tight Tolerance Over Temperature, Line, Load
and Transient Response
n Low Output Noise: 40μVRMS (10Hz to 100kHz)
n Parallel Multiple Devices for 10A or More
n Accurate Programmable Current Limit to Allow
Asymmetric Power Sharing
n Analog Output Margining: ±10% Range
n Synchronization Input
n Stable with Low ESR Ceramic Output Capacitors
n 15mm × 15mm × 4.92mm Surface Mount
BGA Package
n SnPb or RoHS Compliant Finish
Applications
n FPGA and DSP Supplies
n High Speed I/O
n ASIC and Microprocessor Supplies
n Servers and Storage Devices
Description
The LTM®8028 is a 36VIN, 5A µModule® regulator, con-
sisting 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 incre-
ments 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 feed-
back 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 suit-
able 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.
Click to view associated TechClip Videos.
Typical Application
Low Output Noise, 1.2V, 5A µModule Regulator
VIN
9V TO 15V
10µF
150k
0.01µF
VIN
RUN
MARGA
IMAX
SS
82.5k
RT
SYNC
f = 500kHz
LTM8028
GND
LINEAR
VOUT
REGULATOR SENSEP
BKV
PGOOD
VOB VO0 VO1 VO2
+ 100µF
470µF
VOUT
1.2V
5A
137µF
VOUT
20mV/DIV
IOUT
2A/DIV
∆IOUT = 0.5A TO 5A
1µs RISE/FALL TIME
8028 TA01a
FULL LOAD
NOISE AND RIPPLE
500µV/DIV
For more information www.linear.com/LTM8028
10µs/DIV
1µs/DIV
MEASURED PER AN70, 150MHz BW
8028 TA01b
8028fb
1
1 page  
Typical Performance Characteristics
LTM8028
Input Current vs Output Current,
1.8VOUT
2500
2000
6VIN
12VIN
24VIN
36VIN
1500
1000
500
0
01 2 345
OUTPUT CURRENT (A)
8028 G10
Transient Response,
Demo Board, 1V
Input Current vs Input Voltage,
Output Shorted
1200
1000
800
600
400
200
0
0 10 20 30 40
INPUT VOLTAGE (V)
8038 G11
Transient Response,
Demo Board, 1.2V
Output Current vs Input Voltage,
Output Shorted
6.0
5.8
5.6
5.4
5.2
5.0
0
6 12 18 24 30 36
INPUT VOLTAGE (V)
8028 G12
Transient Response,
Demo Board, 1.5V
VOUT
20mV/DIV
IOUT
2A/DIV
∆IOUT
0.5A TO 5A
1µs
RISE/FALL
TIME
10µs/DIV
COUT = 100µF + 22µF + 10µF + 4.7µF
8028 G13
VOUT
20mV/DIV
IOUT
2A/DIV
∆IOUT
0.5A TO 5A
1µs
RISE/FALL
TIME
10µs/DIV
COUT = 100µF + 22µF + 10µF + 4.7µF
8028 G14
VOUT
20mV/DIV
IOUT
2A/DIV
∆IOUT
0.5A TO 5A
1µs
RISE/FALL
TIME
10µs/DIV
COUT = 100µF + 22µF + 10µF + 4.7µF
8028 G15
Transient Response,
Demo Board, 1.8V
Output Noise, 1.8VOUT
VOUT
20mV/DIV
IOUT
2A/DIV
∆IOUT
0.5A TO 5A
1µs
RISE/FALL
TIME
20µs/DIV
COUT = 100µF + 22µF + 10µF + 4.7µF
500µV/DIV
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
12VIN
Current
vs
IMAX
Voltage,
6
5
4
3
2
1
0
0 0.5 1.0 1.5 2.0
IMAX VOLTAGE (V)
8028 G18
For more information www.linear.com/LTM8028
8028fb
5
5 Page 
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
0 0 0 0.80V Z 0
0 0 Z 0.85V Z Z
0 0 1 0.90V Z Z
0 Z 0 0.95V Z Z
0 Z Z 1.00V Z 1
0 Z 1 1.05V Z 1
0 1 0 1.10V Z 1
0 1 Z 1.15V 1 X
0 1 1 1.20V 1 X
Z 0 0 1.25V 1 X
Z 0 Z 1.30V
X = Don’t Care, 0 = Low, Z = Float, 1 = High
VO0 VOUT(NOM)
1 1.35V
0 1.40V
Z 1.45V
1 1.50V
0 1.55V
Z 1.60V
1 1.65V
0 1.70V
Z 1.75V
1 1.80V
Capacitor Selection Considerations
The CIN, CBKV and COUT capacitor values in Table 1 are the
minimum recommended values for the associated oper-
ating conditions. Applying capacitor values below those
indicated in Table 1 is not recommended, and may result
in undesirable operation. Using larger values is generally
acceptable, and can yield improved dynamic response, if
it is necessary. Again, it is incumbent upon the user to
verify proper operation over the intended system’s line,
load and environmental conditions.
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
capacitance resulting in much higher output voltage ripple
than expected.
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, possi-
bly 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?
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.
For more information www.linear.com/LTM8028
8028fb
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11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LTM8028.PDF ] | |
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