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PDF LT8580 Data sheet ( Hoja de datos )
| Número de pieza | LT8580 | |
| Descripción | Boost/SEPIC/Inverting DC/DC Converter | |
| Fabricantes | Linear | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LT8580 (archivo pdf) en la parte inferior de esta página. Total 30 Páginas | ||
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LT8580
Boost/SEPIC/Inverting
DC/DC Converter with 1A, 65V
Switch, Soft-Start and Synchronization
Features
n 1A, 65V Power Switch
n Adjustable Switching Frequency
n Single Feedback Resistor Sets VOUT
n Synchronizable to External Clock
n High Gain SHDN Pin Accepts Slowly Varying
Input Signals
n Wide Input Voltage Range: 2.55V to 40V
n Low VCESAT Switch: 400mV at 0.75A (Typical)
n Integrated Soft-Start Function
n Easily Configurable as a Boost, SEPIC, or Inverting
Converter
n User Configurable Undervoltage Lockout (UVLO)
n Pin Compatible with LT3580
n Tiny Thermally Enhanced 8-Lead 3mm × 3mm DFN
and 8-Lead MSOP Packages
Applications
n VFD Bias Supplies
n TFT-LCD Bias Supplies
n GPS Receivers
n DSL Modems
n Local Power Supply
Description
The LT®8580 is a PWM DC/DC converter containing an
internal 1A, 65V switch. The LT8580 can be configured
as either a boost, SEPIC or inverting converter.
The LT8580 has an adjustable oscillator, set by a resistor
from the RT pin to ground. Additionally, the LT8580 can be
synchronized to an external clock. The switching frequency
of the part may be free running or synchronized, and can
be set between 200kHz and 1.5MHz.
The LT8580 also features innovative SHDN pin circuitry
that allows for slowly varying input signals and an adjust-
able undervoltage lockout function.
Additional features such as frequency foldback and
soft-start are integrated. The LT8580 is available in tiny
thermally enhanced 3mm × 3mm 8-lead DFN and 8-lead
MSOP packages.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents, including 7579816.
Typical Application
1.5MHz, 5V to 12V Boost Converter
VIN 15µH
5V
10k
VOUT
12V
200mA
2.2µF
VIN SW
SHDN
LT8580
SYNC
FBX
VC
RT GND SS
130k
6.04k
56.2k
0.22µF
3.3nF
4.7µF
47pF
8580 TA01a
100
90
80
70
60
50
40
30
20
0
Efficiency and Power Loss
480
420
360
300
240
180
120
EFFICIENCY 60
POWER LOSS
0
50 100 150 200
LOAD CURRENT (mA)
8580 TA01b
For more information www.linear.com/LT8580
8580f
1
1 page  
LT8580
Typical Performance Characteristics TA = 25°C, unless otherwise specified
Oscillator Frequency During
Soft-Start
1
1/2
1/3
1/4
1/5
1/6 INVERTING
NONINVERTING
CONFIGURATIONS CONFIGURATIONS
0
0 0.2 0.4 0.6 0.8 1
FBX VOLTAGE (V)
1.2
8580 G08
Internal UVLO
2.7
2.6
2.5
2.4
2.3
2.2
2.1
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8580 G09
SHDN Pin Current
30
125°C
25°C
25 –40°C
20
15
10
5
0
0 0.25 0.5 0.75 1 1.25 1.5 1.75 2
SHDN VOLTAGE (V)
8580 G10
SHDN Pin Current
400
125°C
350 25°C
–40°C
300
250
200
150
100
50
0
0 5 10 15 20 25 30 35 40
SHDN VOLTAGE (V)
8580 G11
Active/Lockout Threshold
1.40
1.38
1.36
1.34
1.32 SHDN RISING
1.30
1.28
1.26 SHDN FALLING
1.24
1.22
1.20
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8580 G12
For more information www.linear.com/LT8580
8580f
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5 Page 
LT8580
Applications Information
provided to a load (IOUT). In order to provide adequate
load current, L should be at least:
LBOOST
>
DC • VIN
2(f)
⎛⎝⎜ILIM
−
|VOUT|
VIN
• IOUT
•h
⎞
⎟
⎠
for boost, topologies, or:
LDUAL
>
DC • VIN
2(f) ⎛⎝⎜ILIM−
VOUT
VIN
• IOUT
•h
−
IOUT
⎞
⎟
⎠
for the SEPIC and inverting topologies.
where:
LBOOST = L1 for boost topologies (see Figure 15)
LDUAL = L1 = L2 for coupled dual inductor topologies
(see Figure 16 and Figure 17)
LDUAL = L1||L2 for uncoupled dual inductor topologies
(see Figure 16 and Figure 17)
DC = switch duty cycle (see previous section)
ILIM = switch current limit, typically about 1.2A at 50%
duty cycle (see the Typical Performance Characteristics
section).
h = power conversion efficiency (typically 85% for boost
and 83% for dual inductor topologies at high currents).
f = switching frequency
IOUT = maximum load current
Negative values of L indicate that the output load current
IOUT exceeds the switch current limit capability of the
LT8580.
Avoiding Subharmonic Oscillations: The LT8580’s internal
slope compensation circuit can prevent subharmonic oscil-
lations that can occur when the duty cycle is greater than
50%, provided that the inductance exceeds a minimum
value. In applications that operate with duty cycles greater
than 50%, the inductance must be at least:
LMIN
>
VIN
1.25 • (DC − 300nS
•
f)
•
f
2 DC − 1
1− DC
LMIN = L1 for boost topologies (see Figure 15)
LMIN = L1 = L2 for coupled dual inductor topologies
(see Figure 16 and Figure 17)
LMIN = L1||L2 for uncoupled dual inductor topologies
(see Figure 16 and Figure 17)
Maximum Inductance: Excessive inductance can reduce
current ripple to levels that are difficult for the current com-
parator (A3 in the Block Diagram) to cleanly discriminate,
thus causing duty cycle jitter and/or poor regulation. The
maximum inductance can be calculated by:
LMAX
=
VIN − VCESAT
IMIN-RIPPLE
•
DC
f
where
LMIN = L1 for boost topologies (see Figure 15)
LMIN = L1 = L2 for coupled dual inductor topologies
(see Figure 16 and Figure 17)
LMIN = L1||L2 for uncoupled dual inductor topologies
(see Figure 16 and Figure 17)
IMIN(RIPPLE) = typically 80mA
Current Rating: Finally, the inductor(s) must have a rating
greater than its peak operating current to prevent inductor
saturation resulting in efficiency loss. In steady state, the
peak input inductor current (continuous conduction mode
only) is given by:
IL1-PEAK
=
|VOUT • IOUT|
VIN • h
+
VIN • DC
2 • L1• f
for the boost, uncoupled inductor SEPIC and uncoupled
inductor inverting topologies.
For more information www.linear.com/LT8580
8580f
11
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| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet LT8580.PDF ] | |
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