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PDF LT8301 Data sheet ( Hoja de datos )
| Número de pieza | LT8301 | |
| Descripción | Micropower No-Opto Isolated Flyback Converter | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
n 2.7V to 42V Input Voltage Range
n 1.2A, 65V Internal DMOS Power Switch
n Low Quiescent Current:
100µA in Sleep Mode
350µA in Active Mode
n Boundary Mode Operation at Heavy Load
n Low-Ripple Burst Mode® Operation at Light Load
n Minimum Load <0.5% (Typ) of Full Output
n VOUT Set with a Single External Resistor
n No Transformer Third Winding or Opto-Isolator
Required for Regulation
n Accurate EN/UVLO Threshold and Hysteresis
n Internal Compensation and Soft-Start
n Output Short-Circuit Protection
n 5-Lead TSOT-23 Package
APPLICATIONS
n Isolated Telecom, Automotive, Industrial, Medical
Power Supplies
n Isolated Auxiliary/Housekeeping Power Supplies
LT8301
42VIN Micropower No-Opto
Isolated Flyback Converter
with 65V/1.2A Switch
DESCRIPTION
The LT®8301 is a micropower isolated flyback converter.
By sampling the isolated output voltage directly from
the primary-side flyback waveform, the part requires no
third winding or opto-isolator for regulation. The output
voltage is programmed with a single external resistor. In-
ternal compensation and soft-start further reduce external
component count. Boundary mode operation provides a
small magnetic solution with excellent load regulation.
Low ripple Burst Mode operation maintains high efficiency
at light load while minimizing the output voltage ripple. A
1.2A, 65V DMOS power switch is integrated along with
all high voltage circuitry and control logic into a 5-lead
ThinSOT™ package.
The LT8301 operates from an input voltage range of 2.7V
to 42V and can deliver up to 6W of isolated output power.
The high level of integration and the use of boundary
and low ripple burst modes result in a simple to use, low
component count, and high efficiency application solution
for isolated power delivery.
L, LT, LTC, LTM, Linear Technology, the Linear logo and Burst Mode 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 5438499, 7463497,
and 7471522.
TYPICAL APPLICATION
VIN
2.7V TO 36V
2.7V to 36VIN/5VOUT Micropower Isolated Flyback Converter
10µF
VIN
EN/UVLO
SW
LT8301
RFB
GND
3:1
•
40µH
4.4µH
•
154k
VOUT+
5V
6mA TO 0.40A (VIN = 5V)
100µF
6mA
6mA
TO
TO
0.70A
1.00A
(VIN
(VIN
=
=
12V)
24V)
6mA TO 1.15A (VIN = 36V)
8301 TA01a VOUT–
For more information www.linear.com/LT8301
Efficiency vs Load Current
90
85
80
75
70
VIN = 5V
65
VIN = 12V
VIN = 24V
VIN = 36V
60
0 0.2 0.4 0.6 0.8 1.0 1.2
LOAD CURRENT (A)
8301 TA01b
8301f
1
1 page  
LT8301
TYPICAL PERFORMANCE CHARACTERISTICS TA = 25°C, unless otherwise noted.
EN/UVLO Enable Threshold
1.245
1.240
1.235
1.230
1.225
1.220
1.215
1.210
1.205
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8301 G10
RDS(ON)
1000
800
600
400
200
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8301 G13
Minimum Switching Frequency
20
EN/UVLO Hysteresis Current
5
4
3
2
1
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8301 G11
Switch Current Limit
1.6
1.4 MAXIMUM CURRENT LIMIT
1.2
1.0
0.8
0.6
0.4 MINIMUM CURRENT LIMIT
0.2
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8301 G14
Minimum Switch-On Time
500
RFB Regulation Current
105
104
103
102
101
100
99
98
97
96
95
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8301 G12
Maximum Switching Frequency
600
500
400
300
200
100
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8301 G15
Minimum Switch-Off Time
500
15 400 400
300 300
10
200 200
5
100 100
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8301 G16
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8301 G17
0
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8301 G18
For more information www.linear.com/LT8301
8301f
5
5 Page 
LT8301
APPLICATIONS INFORMATION
7
6
MAXIMUM
OUTPUT
CURRENT
5
4
3
N = 5:1
N = 3:1
N = 2:1
2 N = 1:1
1
0
0 10
20 30 40
INPUT VOLTAGE (V)
8301 F01
Figure 1. Output Power for 3.3V Output
7
6
MAXIMUM
OUTPUT
CURRENT
5
4
3
2
N = 3:2
N = 1:1
N = 2:3
N = 1:3
1
0
0 10
20 30 40
INPUT VOLTAGE (V)
8301 F03
Figure 3. Output Power for 12V Output
7
6
MAXIMUM
OUTPUT
CURRENT
5
4
3
2
N = 4:1
N = 3:1
N = 2:1
N = 1:1
1
0
0 10 20 30 40
INPUT VOLTAGE (V)
8301 F02
Figure 2. Output Power for 5V Output
7
6
MAXIMUM
OUTPUT
CURRENT
5
4
3
2
N = 4:5
N = 1:2
N = 1:3
N = 1:5
1
0
0 10 20 30 40
INPUT VOLTAGE (V)
8301 F04
Figure 4. Output Power for 24V Output
Primary Inductance Requirement
In addition to the primary inductance requirement for
The LT8301 obtains output voltage information from the
reflected output voltage on the SW pin. The conduction
of secondary current reflects the output voltage on the
primary SW pin. The sample-and-hold error amplifier needs
a minimum 450ns to settle and sample the reflected output
voltage. In order to ensure proper sampling, the second-
ary winding needs to conduct current for a minimum of
450ns. The following equation gives the minimum value
for primary-side magnetizing inductance:
( )
LPRI
≥
tOFF(MIN)
•NPS • VOUT
ISW(MIN)
+
VF
the minimum switch-off time, the LT8301 has minimum
switch-on time that prevents the chip from turning on
the power switch shorter than approximately 170ns. This
minimum switch-on time is mainly for leading-edge blank-
ing the initial switch turn-on current spike. If the inductor
current exceeds the desired current limit during that time,
oscillation may occur at the output as the current control
loop will lose its ability to regulate. Therefore, the following
equation relating to maximum input voltage must also be
followed in selecting primary-side magnetizing inductance:
LPRI
≥
tON(MIN) • VIN(MAX)
ISW(MIN)
tOFF(MIN) = Minimum switch-off time = 450ns
tON(MIN) = Minimum switch-on time = 170ns
ISW(MIN) = Minimum switch current limit = 290mA (typ)
8301f
For more information www.linear.com/LT8301
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LT8301.PDF ] | |
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