|
|
PDF LT8640-1 Data sheet ( Hoja de datos )
| Número de pieza | LT8640-1 | |
| Descripción | 5A Synchronous Step-Down Silent Switcher | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
|
Hay una vista previa y un enlace de descarga de LT8640-1 (archivo pdf) en la parte inferior de esta página. Total 28 Páginas | ||
|
No Preview Available !
LT8640/LT8640-1
42V, 5A Synchronous
Step-Down Silent Switcher
with 2.5µA Quiescent Current
Features
Description
nn Silent Switcher® Architecture
nn Ultralow EMI/EMC Emissions
nn Spread Spectrum Frequency Modulation
nn High Efficiency at High Frequency
nn Up to 96% Efficiency at 1MHz
nn Up to 95% Efficiency at 2MHz
nn Wide Input Voltage Range: 3.4V to 42V
nn 5A Maximum Continuous Output, 7A Peak
Transient Output
nn Ultralow Quiescent Current Burst Mode® Operation
nn 2.5µA IQ Regulating 12VIN to 3.3VOUT
nn Output Ripple < 10mVP-P
nn Fast Minimum Switch-On Time: 35ns
nn Low Dropout Under All Conditions: 100mV at 1A
nn Forced Continuous Mode (LT8640-1 Only)
nn Safely Tolerates Inductor Saturation in Overload
nn Adjustable and Synchronizable: 200kHz to 3MHz
nn Peak Current Mode Operation
nn Output Soft-Start and Tracking
nn Small 18-Lead 3mm × 4mm QFN
Applications
nn Automotive and Industrial Supplies
nn General Purpose Step-Down
nn GSM Power Supplies
The LT®8640/LT8640-1 step-down regulator features Silent
Switcher architecture designed to minimize EMI/EMC emis-
sions while delivering high efficiency at frequencies up to
3MHz. Assembled in a 3mm × 4mm QFN, the monolithic
construction with integrated power switches and inclusion
of all necessary circuitry yields a solution with a minimal
PCB footprint. An ultralow 2.5µA quiescent current—with
the output in full regulation—enables applications requiring
highest efficiency at very small load currents. Transient
response remains excellent and output voltage ripple is
below 10mVP-P at any load, from zero to full current.
TheLT8640/LT8640-1allowshighVINtolowVOUTconversionat
highfrequencywithafastminimumtopswitchon-timeof35ns.
Operation is safe in overload even with a saturated inductor.
Essential features are included and easy to use: An open-
drain PG pin signals when the output is in regulation. The
SYNC/MODE pin selects between Burst Mode operation,
spread spectrum mode, synchronization to an external
clock, and either pulse-skipping (LT8640) or forced
continuous mode (LT8640-1). Soft-start and tracking
functionality is accessed via the TR/SS pin. An accurate
enable threshold can be set using the EN/UV pin and a
resistor at the RT pin programs switch frequency.
L, LT, LTC, LTM, Linear Technology, the Linear logo, Silent Switcher and Burst Mode are
registered trademarks of Linear Technology Corporation. All other trademarks are the property
of their respective owners.
Typical Application
VIN
5.5V TO 42V
5V 5A Step-Down Converter
4.7µF
1µF
10nF
1µF
41.2k
VIN1 EN/UV VIN2
GND1
GND2
LT8640/
PG LT8640-1 BST
SYNC/MODE SW
TR/SS
BIAS
INTVCC
RT
FB
GND
1µF
0.1µF 3.3µH
VOUT
5V
5A
4.7pF
1M
47µF
243k
fSW = 1MHz
8640 TA01a
12VIN to 5VOUT Efficiency
100
3.00
95 2.63
90 EFFICIENCY
2.25
85 1.88
80 1.50
75 1.13
70 POWER LOSS
0.75
65
60
0.5
1MHz, L = 3.3µH
2MHz, L = 2.2µH 0.38
3MHz, L = 1µH 0
1 1.5 2 2.5 3 3.5 4 4.5 5
LOAD CURRENT (A)
8640 TA01b
For more information www.linear.com/LT8640
8640fa
1
1 page  
Typical Performance Characteristics
12VIN to 5VOUT Efficiency
vs Frequency
100
3.00
95 2.63
90 EFFICIENCY
2.25
85 1.88
80 1.50
75 1.13
70 POWER LOSS
L = WE–LHMI1040 0.75
1MHz, L = 3.3µH
65 2MHz, L = 2.2µH 0.38
60 3MHz, L = 1µH 0
0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
LOAD CURRENT (A)
8640 G01
v1s2VFIrNeqtoue3n.3cVyOUT Efficiency
100
2.80
95 2.45
90 EFFICIENCY
85
2.10
1.75
80 1.40
75
70
65
600.5
1.05
POWER LOSS
1 1.5 2 2.5
L = WE–LHMI1040 0.70
1MHz, L = 2.2μH
2MHz, L = 1μH
0.35
3
3MHz, L = 1μH
3.5 4 4.5
50
LOAD CURRENT (A)
8640 G02
LT8640/LT8640-1
Efficiency at 5VOUT
100
3.0
95 2.7
90
EFFICIENCY
85
2.4
2.1
80 1.8
75 POWER LOSS
70
1.5
1.2
65 VIN = 12V 0.9
60
VIN = 24V
VIN = 36V
0.6
55 fSW = 1MHz 0.3
50 0
0.5
1
1.5
2
L = IHLP3232DZ-01,
2.5 3 3.5 4
3.3μH
4.5
50
LOAD CURRENT (A)
8640 G03
Efficiency at 3.3VOUT
100
3.0
95 2.7
90 2.4
85
EFFICIENCY
2.1
80 1.8
75
70 POWER LOSS
1.5
1.2
65 VIN = 12V 0.9
60
VIN = 24V
VIN = 36V
0.6
55 fSW = 1MHz 0.3
50 L = IHLP3232DZ-01, 2.2μH 0
0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5
LOAD CURRENT (A)
8640 G04
Efficiency vs Frequency
96
94
92
90
88
86
84 VIN = 12V
82
VOUT = 3.3V
ILOAD = 2A
L = IHLP3232DZ-01, 4.7μH
80
0 0.5 1 1.5 2 2.5 3
SWITCHING FREQUENCY (MHz)
8640 G07
Efficiency at 5VOUT
100
90
80
70
60
50
40
30
20
10
0
0.01
fSW = 1MHz
L = IHLP3232DZ-01, 4.7μH
VIN = 12V
VIN = 24V
VIN = 36V
0.1 1 10 100 1000
LOAD CURRENT (mA)
8640 G05
Efficiency at 3.3VOUT
100
90
80
70
60
50
40
30
20
10
0
0.01
fSW = 1MHz
L = IHLP3232DZ-01, 4.7μH
VIN = 12V
VIN = 24V
VIN = 36V
0.1 1
10 100 1000
LOAD CURRENT (mA)
8640 G06
Burst Mode Operation Efficiency
vs Inductor Value
95
VIN = 12V
90
85 VIN = 24V
80
75
70
65
1
VOUT = 5V
ILOAD = 10mA
L = IHLP3232DZ-01
234567
INDUCTOR VALUE (µH)
8
8640 G08
For more information www.linear.com/LT8640
Reference Voltage
0.979
0.977
0.975
0.973
0.971
0.969
0.967
0.965
0.963
0.961
–50 –25
0 25 50 75 100 125 150
TEMPERATURE (°C)
8640 G09
8640fa
5
5 Page 
LT8640/LT8640-1
Pin Functions
BIAS (Pin 1): The internal regulator will draw current
from BIAS instead of VIN when BIAS is tied to a voltage
higher than 3.1V. For output voltages of 3.3V to 25V this
pin should be tied to VOUT. If this pin is tied to a supply
other than VOUT use a 1µF local bypass capacitor on this
pin. If no supply is available, tie to GND.
INTVCC (Pin 2): Internal 3.4V Regulator Bypass Pin. The
internal power drivers and control circuits are powered from
this voltage. INTVCC maximum output current is 20mA.
Do not load the INTVCC pin with external circuitry. INTVCC
current will be supplied from BIAS if BIAS > 3.1V, otherwise
current will be drawn from VIN. Voltage on INTVCC will
vary between 2.8V and 3.4V when BIAS is between 3.0V
and 3.6V. Decouple this pin to power ground with at least
a 1µF low ESR ceramic capacitor placed close to the IC.
BST (Pin 3): This pin is used to provide a drive voltage,
higher than the input voltage, to the topside power switch.
Place a 0.1µF boost capacitor as close as possible to the IC.
VIN1 (Pin 4): The LT8640/LT8640-1 requires two 1µF
small input bypass capacitors. One 1µF capacitor should
be placed between VIN1 and GND1. A second 1µF capacitor
should be placed between VIN2 and GND2. These capaci-
tors must be placed as close as possible to the LT8640/
LT8640-1. A third larger capacitor of 2.2µF or more should
be placed close to the LT8640/LT8640-1 with the positive
terminal connected to VIN1 and VIN2, and the negative
terminal connected to ground. See applications section
for sample layout.
GND1 (6, 7): Power Switch Ground. These pins are the
return path of the internal bottom side power switch and
must be tied together. Place the negative terminal of the
input capacitor as close to the GND1 pins as possible. Also
be sure to tie GND1 to the ground plane. See the Applica-
tions Information section for sample layout.
be sure to tie GND2 to the ground plane. See the Applica-
tions Information section for sample layout.
VIN2 (Pin 13): The LT8640/LT8640-1 requires two 1µF
small input bypass capacitors. One 1µF capacitor should
be placed between VIN1 and GND1. A second 1µF capacitor
should be placed between VIN2 and GND2. These capaci-
tors must be placed as close as possible to the LT8640/
LT8640-1. A third larger capacitor of 2.2µF or more should
be placed close to the LT8640/LT8640-1 with the posi-
tive terminal connected to VIN1 and VIN2, and the nega-
tive terminal connected to ground. See the Applications
Information section for sample layout.
EN/UV (Pin 14): The LT8640/LT8640-1 is shut down
when this pin is low and active when this pin is high. The
hysteretic threshold voltage is 1.00V going up and 0.96V
going down. Tie to VIN if the shutdown feature is not used.
An external resistor divider from VIN can be used to pro-
gram a VIN threshold below which the LT8640/LT8640-1
will shut down.
RT (Pin 15): A resistor is tied between RT and ground to
set the switching frequency.
TR/SS (Pin 16): Output Tracking and Soft-Start Pin. This
pin allows user control of output voltage ramp rate dur-
ing start-up. A TR/SS voltage below 0.97V forces the
LT8640/LT8640-1 to regulate the FB pin to equal the TR/
SS pin voltage. When TR/SS is above 0.97V, the tracking
function is disabled and the internal reference resumes
control of the error amplifier. An internal 1.9µA pull-up
current from INTVCC on this pin allows a capacitor to
program output voltage slew rate. This pin is pulled to
ground with an internal 200Ω MOSFET during shutdown
and fault conditions; use a series resistor if driving from
a low impedance output. This pin may be left floating if
the tracking function is not needed.
SW (Pins 8, 9): The SW pins are the outputs of the internal
power switches. Tie these pins together and connect them
to the inductor and boost capacitor. This node should be
kept small on the PCB for good performance and low EMI.
GND2 (10, 11): Power Switch Ground. These pins are the
return path of the internal bottom side power switch and
must be tied together. Place the negative terminal of the
input capacitor as close to the GND2 pins as possible. Also
SYNC/MODE (Pin 17, LT8640 Only): This pin programs
four different operating modes: 1) Burst Mode operation.
Tie this pin to ground for Burst Mode operation at low
output loads—this will result in ultralow quiescent current.
2) Pulse-skipping mode. This mode offers full frequency
operation down to low output loads before pulse skipping
occurs. Float this pin for pulse-skipping mode. When
floating, pin leakage currents should be <1µA. 3) Spread
8640fa
For more information www.linear.com/LT8640
11
11 Page | ||
| Páginas | Total 28 Páginas | |
| PDF Descargar | [ Datasheet LT8640-1.PDF ] | |
Hoja de datos destacado
| Número de pieza | Descripción | Fabricantes |
| LT8640-1 | 5A Synchronous Step-Down Silent Switcher | 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 |