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PDF LTM4605 Data sheet ( Hoja de datos )
| Número de pieza | LTM4605 | |
| Descripción | High Efficiency Buck-Boost DC/DC uModule | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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www.DataSheet4U.com
LTM4605
High Efficiency
Buck-Boost DC/DC µModule
FEATURES
n Single Inductor Architecture Allows VIN Above,
Below or Equal to VOUT
n Wide VIN Range: 4.5V to 20V
n Wide VOUT Range: 0.8V to 16V
n 5A DC Typical (12A DC Typical at Buck Mode)
n High Efficiency Up to 98%
n Current Mode Control
n Power Good Output Signal
n Phase-Lockable Fixed Frequency: 200kHz to 400kHz
n Ultra-Fast Transient Response
n Current Foldback Protection
n Output Overvoltage Protection
n Small, Low Profile Surface Mount LGA Package
(15mm × 15mm × 2.8mm)
APPLICATIONS
n Telecom, Servers and Networking Equipment
n Industrial and Automotive Equipment
n High Power Battery-Operated Devices
DESCRIPTION
The LTM®4605 is a high efficiency switching mode buck-
boost power supply. Included in the package are the
switching controller, power FETs, and support components.
Operating over an input voltage range of 4.5V to 20V, the
LTM4605 supports an output voltage range of 0.8V to
16V, set by a resistor. This high efficiency design delivers
up to 5A continuous current in boost mode (12A in buck
mode). Only the inductor, sense resistor, bulk input and
output capacitors are needed to finish the design.
The low profile package enables utilization of unused space
on the bottom of PC boards for high density point of load
regulation. The high switching frequency and current
mode architecture enable a very fast transient response
to line and load changes. The LTM4605 can be frequency
synchronized with an external clock to reduce undesirable
frequency harmonics.
Fault protection features include overvoltage and foldback
current protection. The DC/DC μModule™ is offered in a
small and thermally enhanced 15mm × 15mm × 2.8mm LGA
package. The LTM4605 is Pb-free and RoHS compliant.
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. Burst Mode
is a registered trademark of Linear Technology Corporation. μModule is a trademark of Linear
Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
12V/5A Buck-Boost DC/DC μModule with 4.5V to 20V Input
VIN
4.5V TO 20V
10μF
35V
ON/OFF
0.1μF
CLOCK SYNC
VIN PLLIN VOUT
FCB
RUN LTM4605
SW1
SW2
RSENSE
SENSE+
SS
SGND
SENSE–
PGND
VFB
4.7μH
6mΩ
7.15k
10μF +
35V
330μF
25V
VOUT
12V
5A
4605 TA01
Efficiency and Power Loss vs
Input Voltage
99 VOUT = 12V
98 ILOAD = 5A
f = 200kHz
97
96
95
94
93
92
91
8
7
6
5
4
3
2
1
90 0
5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20
VIN (V)
4605 TA01b
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TYPICAL PERFORMANCE CHARACTERISTICS (Refer to Figure 16)
LTM4605
Efficiency vs Load Current
6VIN to 12VOUT
100
90
80
70
60
50
40
30
20
10
0
0.01
0.1 1
LOAD CURRENT (A)
CCM
DCM
BURST
10
4605 G01
Efficiency vs Load Current
3.3μH Inductor (CCM)
100
95
90
85
80
75
70
65
60
0
18VIN TO 5VOUT
12VIN TO 5VOUT
5VIN TO 5VOUT
3 6 9 12
LOAD CURRENT (A)
4605 G04
Transient Response from
6VIN to 12VOUT
IOUT
2A/DIV
Efficiency vs Load Current
12VIN to 12VOUT
100
90
80
70
60
50
40
30
20
10
0
0.01
0.1 1
LOAD CURRENT (A)
CCM
DCM
BURST
10
4605 G02
Efficiency vs Load Current
1.5μH Inductor (CCM)
100
95
90
85
80
75
70
65
60
55
50
0
18VIN TO 3.3VOUT
12VIN TO 3.3VOUT
5VIN TO 3.3VOUT
3 6 9 12
LOAD CURRENT (A)
4605 G05
Transient Response from
12VIN to 12VOUT
IOUT
2A/DIV
Efficiency vs Load Current
18VIN to 12VOUT
95
85
75
65
55
45
35
25
15
0.01
CCM
DCM
SKIP CYCLE
0.1 1 10
LOAD CURRENT (A)
100
4605 G03
Efficiency vs Load Current
1.5μH Inductor (CCM)
100
95
90
85
80
75
70
65
60
55
50
0
18VIN TO 2.5VOUT
12VIN TO 2.5VOUT
5VIN TO 2.5VOUT
3 6 9 12
LOAD CURRENT (A)
4605 G06
Transient Response from
18VIN to 12VOUT
IOUT
2A/DIV
VOUT
200mV/DIV
VOUT
200mV/DIV
VOUT
100mV/DIV
200μs/DIV
4605 G07
LOAD STEP: 0A TO 3A AT CCM
OUTPUT CAPS: 4x 22μF CERAMIC CAPS AND
2x 180μF ELECTROLYTIC CAPS
2x 15mΩ SENSING RESISTORS
200μs/DIV
4605 G08
LOAD STEP: 0A TO 3A AT CCM
OUTPUT CAPS: 4x 22μF CERAMIC CAPS AND
2x 180μF ELECTROLYTIC CAPS
2x 15mΩ SENSING RESISTORS
200μs/DIV
4605 G09
LOAD STEP: 0A TO 4A AT CCM
OUTPUT CAPS: 4x 22μF CERAMIC CAPS AND
2x 180μF ELECTROLYTIC CAPS
2x 15mΩ SENSING RESISTORS
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LTM4605
APPLICATIONS INFORMATION
For a buck converter, the switching duty-cycle can be
estimated as:
D = VOUT
VIN
Without considering the inductor current ripple, the RMS
current of the input capacitor can be estimated as:
ICIN(RMS)
=
IOUT(MAX)
η
•
D • (1− D)
In the above equation, η is the estimated efficiency of the
power module. CIN can be a switcher-rated electrolytic
aluminum capacitor, OS-CON capacitor or high volume
ceramic capacitors. Note the capacitor ripple current rat-
ings are often based on temperature and hours of life. This
makes it advisable to properly derate the input capacitor,
or choose a capacitor rated at a higher temperature than
required. Always contact the capacitor manufacturer for
derating requirements.
Output Capacitors
In boost mode, the discontinuous current shifts from the
input to the output, so the output capacitor COUT must be
capable of reducing the output voltage ripple.
For boost and buck modes, the steady ripple due to charg-
ing and discharging the bulk capacitance is given by:
( )VRIPPLE,BOOST
=
IOUT(MAX) •
COUT
VOUT − VIN(MIN)
• VOUT • f
( )VRIPPLE,BUCK
=
VOUT
8 •L •
• VIN(MAX) − VOUT
COUT • VIN(MAX) • f2
The steady ripple due to the voltage drop across the ESR
(effective series resistance) is given by:
VESR,BUCK = ΔIL(MAX) • ESR
VESR,BOOST = IL(MAX) • ESR
The LTM4605 is designed for low output voltage ripple.
The bulk output capacitors defined as COUT are chosen
with low enough ESR to meet the output voltage ripple
and transient requirements. COUT can be a low ESR tanta-
lum capacitor, a low ESR polymer capacitor or a ceramic
capacitor. Multiple capacitors can be placed in parallel to
meet the ESR and RMS current handling requirements. The
typical capacitance is 300μF. Additional output filtering may
be required by the system designer, if further reduction of
output ripple or dynamic transient spike is required. Table
3 shows a matrix of different output voltages and output
capacitors to minimize the voltage droop and overshoot
at a current transient.
Inductor Selection
The inductor is chiefly decided by the required ripple cur-
rent and the operating frequency. The inductor current
ripple ΔIL is typically set to 20% to 40% of the maximum
inductor current. In the inductor design, the worst cases
in continuous mode are considered as follows:
( )LBOOST
≥
VIN •
VOUT(MAX)
VOUT(MAX) −
• f •IOUT(MAX)
VIN
• Ripple%
( )LBUCK
≥
VOUT •
VIN(MAX) • f
VIN(MAX) −
• IOUT(MAX)
VOUT
• Ripple%
where:
f is operating frequency, Hz
Ripple% is allowable inductor current ripple, %
VOUT(MAX) is maximum output voltage, V
VIN(MAX) is maximum input voltage, V
VOUT is output voltage, V
IOUT(MAX) is maximum output load current, A
The inductor should have low DC resistance to reduce the
I2R losses, and must be able to handle the peak inductor
current without saturation. To minimize radiated noise,
use a toroid, pot core or shielded bobbin inductor. Please
refer to Table 3 for the recommended inductors for dif-
ferent cases.
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11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LTM4605.PDF ] | |
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