|
|
PDF LT3506A Data sheet ( Hoja de datos )
| Número de pieza | LT3506A | |
| Descripción | Dual Monolithic 1.6A Step-Down Switching Regulator | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LT3506A (archivo pdf) en la parte inferior de esta página. Total 24 Páginas | ||
|
No Preview Available !
www.DataSheet4U.com
LT3506/LT3506A
Dual Monolithic 1.6A
Step-Down Switching Regulator
FEATURES
■ Wide Input Voltage Range, 3.6V to 25V
■ Two 1.6A Output Switching Regulators with Internal
Power Switches
■ Constant Switching Frequency
LT3506: 575kHz
LT3506A: 1.1MHz
■ Anti-Phase Switching Reduces Ripple
■ Accurate 0.8V Reference, ±1%
■ Independent Shutdown/Soft-Start Pins
■ Independent Power Good Indicators Ease Supply
Sequencing
■ Uses Small Inductors and Ceramic Capacitors
■ Small 16-Lead Thermally Enhanced 5mm × 4mm
DFN and TSSOP Surface Mount Packages
APPLICATIOUS
■ Disk Drives
■ DSP Power Supplies
■ Wall Transformer Regulation
■ Distributed Power Regulation
■ DSL Modems
■ Cable Modems
DESCRIPTIO
The LT®3506 is a dual current mode PWM step-down DC/DC
converter with internal 2A power switches. Both convert-
ers are synchronized to a single oscillator and run with
opposite phases, reducing input ripple current. The output
voltages are set with external resistor dividers, and each
regulator has independent shutdown and soft-start circuits.
Each regulator generates a power-good signal when its
output is in regulation, easing power supply sequencing
and interfacing with microcontrollers and DSPs.
The LT3506 switching frequency is 575kHz and the LT3506A
is 1.1MHz. These high switching frequencies allow the
use of tiny inductors and capacitors, resulting in a very
small dual 1.6A output solution. Constant frequency and
ceramic capacitors combine to produce low, predictable
output ripple voltage. With its wide input range of 3.6V to
25V, the LT3506 regulates a wide variety of power sources,
from 4-cell batteries and 5V logic rails to unregulated wall
transformers, lead acid batteries and distributed-power
supplies. Current mode PWM architecture provides fast
transient response with simple compensation components
and cycle-by-cycle current limiting. Frequency foldback
and thermal shutdown provide additional protection.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
VOUT1
1.8V
1.6A
VIN
4.5V TO 25V
4.7µH
18.7k
47µF 15k
22µF
0.22µF
1000pF
VIN1 VIN2
BOOST1 BOOST2
SW1 SW2
FB1 FB2
VC1 VC2
1/2 BAT-54A
1/2 BAT-54A
0.22µF
2200pF
6.4µH
33.2k
D1 15k
LT3506
10k D2 10.7k
PGOOD1
PGOOD2
100k
100k
1.5nF
RUN/SS1 RUN/SS2
PGOOD1
1.5nF
PGOOD2
GND
D1, D2: ON SEMI MBR5230LT3
VOUT2
3.3V
1.6A
22µF
3506 F01
100 VIN = 5V
Efficiency
90 VOUT = 3.3V
80 VOUT = 1.8V
70
60
50
0
0.5 1.0 1.5 2.0
IOUT (A)
3506 TA01b
3506afb
1 page  
www.DataSheet4U.com
LT3506/LT3506A
TYPICAL PERFOR A CE CHARACTERISTICS
IRUN/SS vs Temperature
3.0
RUN/SS Thresholds vs
Temperature
1.4
2.5 1.2
1.0
2.0 TO SWITCH
0.8
1.5
0.6
1.0 TO RUN
0.4
0.5 0.2
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3506 G12
0
–50 –25
0 25 50 75
TEMPERATURE (°C)
100 125
3506 G13
PI FU CTIO S
BOOST1 (Pin 1), BOOST2 (Pin 8): The BOOST pins are
used to provide drive voltages, higher than the input
voltage, to the internal bipolar NPN power switches. Tie
through a diode from VOUT or from VIN.
SW1 (Pin 2), SW2 (Pin 7): The SW pins are the outputs
of the internal power switches. Connect these pins to the
inductors, catch diodes and boost capacitors.
VIN1 (Pins 3, 4): The VIN1 pins supply current to the
LT3506’s internal regulator and to the internal power
switch connected to SW1. These pins must be locally
bypassed.
VIN2 (Pins 5, 6): The VIN2 pins supply current to the inter-
nal power switch connected to SW2 and must be locally
bypassed. Connect these pins directly to VIN1 unless power
for Channel 2 is coming from a different source.
RUN/SS1 (Pin 13), RUN/SS2 (Pin 12): The RUN/SS pins
are used to shut down the individual switching regula-
tors and the internal bias circuits. They also provide a
soft-start function. To shut down either regulator, pull the
RUN/SS pin to ground with an open drain or collector.
Tie a capacitor from these pins to ground to limit switch
current during start-up. If neither feature is used, leave
these pins unconnected.
PG1 (Pin 14), PG2 (Pin 11): The Power Good pins are
the open collector outputs of an internal comparator. PG
remains low until the FB pin is within 10% of the final
regulation voltage. As well as indicating output regulation,
the PG pins can be used to sequence the two switching
regulators. These pins can be left unconnected. The PG
outputs are valid when VIN is greater than 3.4V and either
of the RUN/SS pins is high. The PG comparators are
disabled in shutdown.
VC1 (Pin 15), VC2 (Pin 10): The VC pins are the outputs of
the internal error amps. The voltages on these pins control
the peak switch currents. These pins are normally used
to compensate the control loops, but can also be used to
override the loops. Pull these pins to ground with an open
drain to shut down each switching regulator.
FB1 (Pin 16), FB2 (Pin 9): The LT3506 regulates each
feedback pin to 800mV. Connect the feedback resistor
divider taps to these pins.
Exposed Pad (Pin 17): The Exposed Pad of the package
provides both electrical contact to ground and good thermal
contact to the printed circuit board. The Exposed Pad must
be soldered to the circuit board for proper operation.
3506afb
5 Page 
www.DataSheet4U.com
LT3506/LT3506A
APPLICATIO S I FOR ATIO
Finally, there must be enough capacitance for good transient
performance. The last equation gives a good starting point.
Alternatively, you can start with one of the designs in this
data sheet and experiment to get the desired performance.
This topic is covered more thoroughly in the section on
loop compensation.
For 5V and 3.3V outputs with greater than 1A output, a
22μF 6.3V ceramic capacitor (X5R or X7R) at the output
results in very low output voltage ripple and good tran-
sient response. For lower voltages, 22μF is adequate but
increasing COUT will improve transient performance. For
the LT3506A, 10μF of output capacitance is sufficient at
VOUT between 3.3V and 5V. Other types and values can be
used. The following discusses tradeoffs in output ripple
and transient performance.
The high performance (low ESR), small size and robust-
ness of ceramic capacitors make them the preferred type
for LT3506 applications. However, all ceramic capacitors
are not the same. As mentioned above, many of the
higher value capacitors use poor dielectrics with high
temperature and voltage coefficients. In particular, Y5V
and Z5U types lose a large fraction of their capacitance
with applied voltage and temperature extremes. Because
the loop stability and transient response depend on the
value of COUT, you may not be able to tolerate this loss.
Use X7R and X5R types.
You can also use electrolytic capacitors. The ESRs of most
aluminum electrolytics are too large to deliver low output
ripple. Tantalum and newer, lower ESR organic electrolytic
capacitors intended for power supply use are suitable,
and the manufacturers will specify the ESR. The choice of
capacitor value will be based on the ESR required for low
ripple. Because the volume of the capacitor determines
its ESR, both the size and the value will be larger than a
ceramic capacitor that would give similar ripple perfor-
mance. One benefit is that the larger capacitance may give
better transient response for large changes in load current.
Table 2 lists several capacitor vendors.
Table 2. Low-ESR Surface Mount Capacitors
VENDOR
TYPE
SERIES
Taiyo-Yuden
Ceramic
AVX Ceramic
Tantalum
TPS
Kemet
Tantalum
Tantalum
Organic
Aluminum
Organic
T491, T494, T495, T520
A700
Sanyo
Tantalum or Aluminum POSCAP
Organic
Panasonic
Aluminum
Organic
SP
CAP
TDK Ceramic
Catch Diode
The catch diode (D1 in Figure 2) must have a reverse volt-
age rating greater than the maximum input voltage. The
average current of the catch diode is given by:
IDAVE=IOUT(1-DCMIN)
A Schottky diode with a 1A average forward current rating
will suffice for most applications. The ON Semiconductor
MBRM120LT3 (20V) and MBRM130LT3 (30V) are good
choices; they have a tiny package with good thermal proper-
ties. Many vendors have suitable surface mount versions of
the 1N5817 (20V) and 1N5818 (30V) 1A Schottky diodes
such as the Microsemi UPS120.
Applications with large step down ratios and high output
currents may have more than 1A of average diode current.
The ON Semiconductor MBRS230LT3 or International Rec-
tifier 20BQ030 (both 2A, 30V) would be good choices.
BOOST Pin Considerations
The capacitor and diode tied to the BOOST pin generate
a voltage that is higher than the input voltage. In most
cases a 0.1μF capacitor and fast switching diode (such
as the CMDSH-3 or FMMD914) will work well. Figure 3
3506afb
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LT3506A.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LT3506 | Dual Monolithic 1.6A Step-Down Switching Regulator | Linear Technology |
| LT3506A | Dual Monolithic 1.6A Step-Down Switching Regulator | 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 |