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PDF LT1506CR-SYNC Data sheet ( Hoja de datos )
| Número de pieza | LT1506CR-SYNC | |
| Descripción | 4.5A/ 500kHz Step-Down Switching Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LT1506
4.5A, 500kHz Step-Down
Switching Regulator
FEATURES
s Constant 500kHz Switching Frequency
s Easily Synchronizable
s Operates with Input as Low as 4V
s Uses All Surface Mount Components
s Inductor Size Reduced to 1.8µH
s Saturating Switch Design: 0.07Ω
s Shutdown Current: 20µA
s Cycle-by-Cycle Current Limiting
U
APPLICATIONS
s Portable Computers
s Battery-Powered Systems
s Battery Charger
s Distributed Power
DESCRIPTION
The LT®1506 is a 500kHz monolithic buck mode switching
regulator functionally identical to the LT1374 but optimized
for lower input voltage applications. It will operate over a
4V to 15V input range compared with 5.5V to 25V for the
LT1374. A 4.5A switch is included on the die along with all
the necessary oscillator, control and logic circuitry. High
switching frequency allows a considerable reduction in the
size of external components. The topology is current mode
for fast transient response and good loop stability. Both
fixed output voltage and adjustable parts are available.
A special high speed bipolar process and new design tech-
niques achieve high efficiency at high switching frequency.
Efficiency is maintained over a wide output current range
by keeping quiescent supply current to 4mA and by utiliz-
ing a supply boost capacitor to saturate the power switch.
The LT1506 fits into standard 7-pin DD and fused lead
SO-8 packages. Full cycle-by-cycle short-circuit protection
and thermal shutdown are provided. Standard surface
mount external parts are used, including the inductor and
capacitors. There is the optional function of shutdown or
synchronization. A shutdown signal reduces supply current
to 20µA. Synchronization allows an external logic level sig-
nal to increase the internal oscillator from 580kHz to 1MHz.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATION
5V to 3.3V Down Converter
D2
1N914
INPUT
5V
10µF
C3
TO
+
50µF
CERAMIC
OPEN
OR
HIGH
= ON
C2
0.68µF
BOOST
VIN VSW
LT1506-3.3
SHDN
SENSE
GND VC
CC
1.5nF
L1
5µH OUTPUT
3.3V
4A
+
D1
MBRS330T3
C1
100µF, 10V
SOLID
TANTALUM
1506 TA01
Efficiency vs Load Current
90
VOUT = 3.3V
VIN = 5V
L = 10µH
85
80
75
70
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0
LOAD CURRENT (A)
1506 TA02
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LT1506
Frequency Foldback
500
400
SWITCHING
FREQUENCY
300
200
100
0
0
FEEDBACK PIN
CURRENT
0.5 1.0 1.5 2.0
FEEDBACK PIN VOLTAGE (V)
2.5
1506 G10
Switching Frequency
550
540
530
520
510
500
490
480
470
460
450
– 50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
1506 G11
Maximum Load Current
at VOUT = 5V
4.4
4.2
L= 10µH
4.0 L= 5µH
3.8
3.6 L= 3µH
3.4
3.2
3.0 L= 1.8µH
2.8
2.6
5
7 9 11
INPUT VOLTAGE (V)
13 15
1506 G17
Current Limit Foldback
7 FOLDBACK
CHARACTERISTICS
6
POSSIBLE UNDESIRED
CURRENT
5
STABLE POINT FOR
CURRENT SOURCE
SOURCE
LOAD
LOAD*
4 RESISTOR
LOAD
3
2
MOS LOAD
1
Maximum Load Current
at VOUT = 3.3V
4.4
L= 10µH
4.2
L= 5µH
4.0
3.8 L= 3µH
3.6
3.4
L= 1.8µH
3.2
3.0
4
6 8 10 12
INPUT VOLTAGE (V)
14
1506 G13
VC Pin Shutdown Threshold
1.4
SHUTDOWN
1.2
1.0
0.8
0.6
0
0 20 40 60 80 100
OUTPUT VOLTAGE (%)
1506 G18
0.4
–50
–25 0 25 50 75 100
JUNCTION TEMPERATURE (°C)
125
1506 G15
Kool Mµ is a registered trademark of Magnetics, Inc.
Metglas is a registered trademark of AlliedSignal Inc.
*See “More Than Just Voltage Feedback” in the Applications Information section.
Inductor Core Loss for 3.3V Output
1.0
0.1 TYPE 52
Kool Mµ®
0.01
PERMALLOY
µ = 125
Metglas®
0.001
0
24 6 8
INDUCTANCE (µH)
10
1506 G01
BOOST Pin Current
100
DUTY CYCLE = 100%
90
80
70
60
50
40
30
20
10
0
0 12 34 5
SWITCH CURRENT (A)
1506 G14
Switch Voltage Drop
500
450
125°C
400
350
25°C
300
250
– 40°C
200
150
100
50
0
01 23 4 5
SWITCH CURRENT (A)
1506 G16
5
5 Page 
LT1506
APPLICATIONS INFORMATION
Table 2
VENDOR/
PART NO.
SERIES CORE
VALUE DC CORE RESIS- MATER- HEIGHT
(µH) (Amps) TYPE TANCE(Ω) IAL (mm)
Coiltronics
CTX2-1
2 4.1 Tor 0.011 KMµ 4.2
CTX5-4
5 4.4 Tor 0.019 KMµ 6.4
CTX8-4
8 3.5 Tor 0.020 KMµ 6.4
CTX2-1P
2 3.4 Tor 0.014 52
4.2
CTX2-3P
2 4.6 Tor 0.012 52
4.8
CTX5-4P
5 3.3 Tor 0.027 52
6.4
Sumida
CDRH125
10 4.0 SC 0.025
Fer
6
CDRH125
12 3.5 SC 0.027
Fer
6
CDRH125
15 3.3 SC 0.030
Fer
6
CDRH125
18 3.0 SC 0.034
Fer
6
Coilcraft
DT3316-222 2.2
5
SC 0.035
Fer
5.1
DT3316-332 3.3
5
SC 0.040
Fer
5.1
DT3316-472 4.7
3
SC 0.045
Fer
5.1
Pulse
PE-53650
4 4.8 Tor 0.017 Fer
9.1
PE-53651
5 5.4 Tor 0.018 Fer
9.1
PE-53652
9 5.5 Tor 0.022 Fer
10
PE-53653
16 5.1 Tor 0.032
Fer
10
Dale
IHSM-4825 2.7 5.1 Open 0.034 Fer 5.6
IHSM-4825 4.7 4.0 Open 0.047 Fer 5.6
IHSM-5832 10 4.3 Open 0.053 Fer 7.1
IHSM-5832 15 3.5 Open 0.078 Fer 7.1
IHSM-7832 22 3.8 Open 0.054 Fer 7.1
Tor = Toroid
SC = Semiclosed geometry
Fer = Ferrite core material
52 = Type 52 powdered iron core material
KMµ = Kool Mµ
Output Capacitor
The output capacitor is normally chosen by its Effective
Series Resistance (ESR), because this is what determines
output ripple voltage. At 500kHz, any polarized capacitor
is essentially resistive. To get low ESR takes volume, so
physically smaller capacitors have high ESR. The ESR
range for typical LT1506 applications is 0.05Ω to 0.2Ω. A
typical output capacitor is an AVX type TPS, 100µF at 10V,
with a guaranteed ESR less than 0.1Ω. This is a “D” size
surface mount solid tantalum capacitor. TPS capacitors
are specially constructed and tested for low ESR, so they
give the lowest ESR for a given volume. The value in
microfarads is not particularly critical, and values from
22µF to greater than 500µF work well, but you cannot
cheat mother nature on ESR. If you find a tiny 22µF solid
tantalum capacitor, it will have high ESR, and output ripple
voltage will be terrible. Table 3 shows some typical solid
tantalum surface mount capacitors.
Table 3. Surface Mount Solid Tantalum Capacitor ESR
and Ripple Current
E Case Size
ESR (Max., Ω) Ripple Current (A)
AVX TPS, Sprague 593D
0.1 to 0.3
0.7 to 1.1
AVX TAJ
0.7 to 0.9
0.4
D Case Size
AVX TPS, Sprague 593D
0.1 to 0.3
0.7 to 1.1
C Case Size
AVX TPS
0.2 (typ)
0.5 (typ)
Many engineers have heard that solid tantalum capacitors
are prone to failure if they undergo high surge currents.
This is historically true, and type TPS capacitors are
specially tested for surge capability, but surge ruggedness
is not a critical issue with the output capacitor. Solid
tantalum capacitors fail during very high turn-on surges,
which do not occur at the output of regulators. High
discharge surges, such as when the regulator output is
dead shorted, do not harm the capacitors.
Unlike the input capacitor, RMS ripple current in the
output capacitor is normally low enough that ripple cur-
rent rating is not an issue. The current waveform is
triangular with a typical value of 200mARMS. The formula
to calculate this is:
Output Capacitor Ripple Current (RMS):
( ( )())(( ) )( )IRIPPLE RMS
0.29
=
VOUT
Lf
VIN − VOUT
VIN
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LT1506CR-SYNC.PDF ] | |
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