|
|
PDF LT3959 Data sheet ( Hoja de datos )
| Número de pieza | LT3959 | |
| Descripción | Wide Input Voltage Range Boost/SEPIC/Inverting Converter | |
| Fabricantes | Linear | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LT3959 (archivo pdf) en la parte inferior de esta página. Total 26 Páginas | ||
|
No Preview Available !
LT3959
Features
Wide Input Voltage Range
Boost/SEPIC/Inverting Converter
with 6A, 40V Switch
Description
n Wide VIN Range: 1.6V (2.5V Start-Up) to 40V
n Positive or Negative Output Voltage Programming
with a Single Feedback Pin
n PGOOD Output Voltage Status Report
n Internal 6A/40V Power Switch
n Programmable Soft-Start
n Programmable Operating Frequency (100kHz to 1MHz)
with One External Resistor
n Synchronizable to an External Clock
n Low Shutdown Current < 1µA
n INTVCC Regulator Supplied from VIN or DRIVE
n Programmable Input Undervoltage Lockout with
Hysteresis
n Thermally Enhanced QFN (5mm × 6mm) and TSSOP
Packages
Applications
n Automotive
n Telecom
n Industrial
The LT®3959 is a wide input range, current mode, DC/DC
controller which is capable of regulating either positive or
negative output voltages from a single feedback pin. It can
be configured as a boost, SEPIC or inverting converter.
It features an internal low side N-channel MOSFET rated
for 6A at 40V and driven from an internal regulated sup-
ply provided from VIN or DRIVE. The fixed frequency,
current-mode architecture results in stable operation over
a wide range of supply and output voltages. The operating
frequency of LT3959 can be set over a 100kHz to 1MHz
range with an external resistor, or can be synchronized
to an external clock using the SYNC pin.
The LT3959 features soft-start and frequency foldback
functions to limit inductor current during start-up and
output short-circuit. A window comparator on the FBX
pin reports via the PGOOD pin, providing output voltage
status indication.
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
ThinSOT are trademarks of Linear Technology Corporation. All other trademarks are the
property of their respective owners. Protected by U.S. Patents, including 7825665.
Typical Application
2.5V to 24V Input, 12V Output SEPIC Converter
Excellent for Automotive 12V Post Regulator
VIN
2.5V TO
24V
4.7µF
L1A 50V
CIN
22µF
50V
×2
150k
124k
121k
VIN
EN_UVLO
LT3959
SW
GND
L1B
27.4k
300kHz
TIE TO SGND
IF NOT USED
PGOOD
SYNC
DRIVE
RT
SS FBX
VC SGND GNDK INTVCC
105K
0.1µF 7.5k
22nF
15.8K
4.7µF
COUT
47µF
16V
×2
VOUT
12V
500mA AT VIN = 2.5V
1.5A AT VIN > 8V
3959 TA01a
For more information www.linear.com/LT3959
Efficiency vs Output Current
100
VIN = 12V
95
90
85
80
75
70
65
60
0 200 400 600 800 1000
OUTPUT CURRENT (mA)
3959 TA01b
3959fa
1
1 page  
LT3959
Typical Performance Characteristics TA = 25°C, unless otherwise noted.
FBX Positive Regulation Voltage
vs Temperature
1.62
FBX Negative Regulation Voltage
vs Temperature
–0.78
1.61 –0.79
1.60 –0.80
1.59 –0.81
1.58
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3959 G01
Dynamic Quiescent Current
vs Switching Frequency
25 DRIVE = 6V
20
15
IQ (DRIVE)
10
5
IQ (VIN)
0
0 200 400 600 800 1000
SWITCHING FREQUENCY (kHz)
3959 G04
Switching Frequency
vs Temperature
350
325
300
275
250
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3959 G07
–0.82
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3959 G02
RT vs Switching Frequency
100
90
80
70
60
50
40
30
20
10
0
0 100 200 300 400 500 600 700 800 900 1000
SWITCHING FREQUENCY (kHz)
3959 G05
SW Current Limit vs Temperature
7.6
7.4
7.2
7.0
6.8
6.6
6.4
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3959 G08
For more information www.linear.com/LT3959
Quiescent Current
vs Temperature
2.4
IQ (DRIVE)
2.0
1.6
VIN = 12V
1.2 DRIVE = 6V
0.8
0.4 IQ (VIN)
0.0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3959 G03
Normalized Switching Frequency
vs FBX Voltage
120
100
80
60
40
20
0
–0.8 –0.4
0 0.4 0.8
FBX VOLTAGE (V)
1.2 1.6
3959 G06
SW Current Limit vs Duty Cycle
8.0
7.5
7.0
6.5
6.0
5.5
5.0
0
20 40 60 80
DUTY CYCLE (%)
100
3959 G09
3959fa
5
5 Page 
LT3959
Applications Information
Duty Cycle Consideration
Switching duty cycle is a key variable defining converter
operation. As such, its limits must be considered. Minimum
on-time is the smallest time duration that the LT3959 is
capable of turning on the internal power MOSFET. This time
is generally about 150ns (typical) (see Minimum On-Time
in the Electrical Characteristics table). In each switching
cycle, the LT3959 keeps the power switch off for at least
150ns (typical) (see Minimum Off-Time in the Electrical
Characteristics table).
The minimum on-time and minimum off-time and the
switching frequency define the minimum and maximum
switching duty cycles a converter is able to generate:
Minimum duty cycle = minimum on-time • frequency
Maximum duty cycle = 1 – (minimum off-time • frequency)
Programming the Output Voltage
The output voltage (VOUT) is set by a resistor divider, as
shown in Figure 1. The positive VOUT and negative VOUT
are set by the following equations:
VOUT(POSITIVE)
=
1.6V
•
1+
R2
R1
VOUT(NEGATIVE)
=
–0.8V
•
1+
R2
R1
The resistors R1 and R2 are typically chosen so that the
error caused by the current flowing into the FBX pin dur-
ing normal operation is less than 1% (this translates to a
maximum value of R1 at about 121k).
Soft-Start
The LT3959 contains several features to limit peak switch
currents and output voltage (VOUT) overshoot during
start-up or recovery from a fault condition. The primary
purpose of these features is to prevent damage to external
components or the load.
High peak switch currents during start-up may occur in
switching regulators. Since VOUT is far from its final value,
the feedback loop is saturated and the regulator tries to
charge the output capacitor as quickly as possible, resulting
in large peak currents. A large surge current may cause
inductor saturation or power switch failure.
LT3959 addresses this mechanism with the SS pin. As
shown in Figure 1, the SS pin reduces the internal power
MOSFET current by pulling down the VC pin through Q2.
In this way the SS allows the output capacitor to charge
gradually toward its final value while limiting the start-up
peak currents.
Besides start-up, soft-start can also be triggered by
INTVCC undervoltage lockout and/or thermal lockout, which
causes the LT3959 to stop switching immediately. The SS
pin will be discharged by Q3. When all faults are cleared
and the SS pin has been discharged below 0.2V, a 10µA
current source IS2 starts charging the SS pin, initiating a
soft-start operation.
The soft-start interval is set by the soft-start capacitor
selection according to the equation:
TSS
=
CSS
•
1.25V
10µA
FBX Frequency Foldback
When VOUT is very low during start-up or a short-circuit
fault on the output, the switching regulator must operate
at low duty cycles to maintain the power switch current
within the current limit range, since the inductor current
decay rate is very low during switch off time. The minimum
on-time limitation may prevent the switcher from attaining
a sufficiently low duty cycle at the programmed switching
frequency. So, the switch current will keep increasing
through each switch cycle, exceeding the programmed
current limit. To prevent the switch peak currents from
exceeding the programmed value, the LT3959 contains
a frequency foldback function to reduce the switching
frequency when the FBX voltage is low (see the Normal-
ized Switching Frequency vs FBX graph in the Typical
Performance Characteristics section).
For more information www.linear.com/LT3959
3959fa
11
11 Page | ||
| Páginas | Total 26 Páginas | |
| PDF Descargar | [ Datasheet LT3959.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LT3952 | 60V LED Driver | Linear |
| LT3954 | 40V IN LED Converter |  Linear Technology |
| LT3955 | LED Converter | Linear |
| LT3956 | Constant-Current and Constant-Voltage Converter | Linear Technology |
| Número de pieza | Descripción | Fabricantes |
| SLA6805M | High Voltage 3 phase Motor Driver IC. |
 Sanken |
| SDC1742 | 12- and 14-Bit Hybrid Synchro / Resolver-to-Digital Converters. |
 Analog Devices |
|
DataSheet.es es una pagina web que funciona como un repositorio de manuales o hoja de datos de muchos de los productos más populares, |
| DataSheet.es | 2020 | Privacy Policy | Contacto | Buscar |