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PDF LTC4412 Data sheet ( Hoja de datos )
| Número de pieza | LTC4412 | |
| Descripción | Low Loss PowerPath Controller | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de LTC4412 (archivo pdf) en la parte inferior de esta página. Total 14 Páginas | ||
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Features
nn Very Low Loss Replacement for Power Supply
OR’ing Diodes
nn Minimal External Components
nn Automatic Switching Between DC Sources
nn Simplifies Load Sharing with Multiple Batteries
nn Low Quiescent Current: 11µA
nn 3V to 28V AC/DC Adapter Voltage Range
nn 2.5V to 28V Battery Voltage Range
nn Reverse Battery Protection
nn Drives Almost Any Size MOSFET for Wide Range of
Current Requirements
nn MOSFET Gate Protection Clamp
nn Manual Control Input
nn Low Profile (1mm) ThinSOT™ Package
Applications
nn Cellular Phones
nn Notebook and Handheld Computers
nn Digital Cameras
nn USB-Powered Peripherals
nn Uninterruptible Power Supplies
nn Logic Controlled Power Switch
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
LTC4412
Low Loss PowerPath™
Controller in ThinSOT
Description
The LTC®4412 controls an external P-channel MOSFET to
create a near ideal diode function for power switchover
or load sharing. This permits highly efficient OR’ing of
multiple power sources for extended battery life and low
self-heating. When conducting, the voltage drop across
the MOSFET is typically 20mV. For applications with a
wall adapter or other auxiliary power source, the load is
automatically disconnected from the battery when the
auxiliary source is connected. Two or more LTC4412s
may be interconnected to allow load sharing between
multiple batteries or charging of multiple batteries from
a single charger.
The wide supply operating range supports operation
from one to six Li-Ion cells in series. The low quiescent
current (11µA typical) is independent of the load current.
The gate driver includes an internal voltage clamp for
MOSFET protection.
The STAT pin can be used to enable an auxiliary P-channel
MOSFET power switch when an auxiliary supply is
detected. This pin may also be used to indicate to a mi-
crocontroller that an auxiliary supply is connected. The
control (CTL) input enables the user to force the primary
MOSFET off and the STAT pin low.
The LTC4412 is available in a low profile (1mm) ThinSOT
package.
Typical Application
WALL
ADAPTER
INPUT
BATTERY
CELL(S)
LTC4412
VIN SENSE
GND GATE
CTL STAT
COUT
VCC
TO LOAD
470k STATUS OUTPUT
LOW WHEN WALL
4412 F01 ADAPTER PRESENT
LTC4412 vs Schottky Diode
Forward Voltage Drop
1
CONSTANT
RON
LTC4412
CONSTANT
VOLTAGE
SCHOTTKY
DIODE
Figure 1. Automatic Switchover of Load Between a Battery and a Wall Adapter
0
0.02
For more information www.linear.com/LTC4412
FORWARD VOLTAGE (V)
0.5
4412 F01b
4412fb
1
1 page  
Typical Performance Characteristics
LTC4412
VFR vs Temperature and
Supply Voltage
25
VIN = 2.5V
20 VIN = 28V
VRTO vs Temperature and
Supply Voltage
25
VIN = 28V
20
VIN = 2.5V
Normalized Quiescent Supply
Current vs Temperature
1.15
1.10
1.05
3.6V ≤ VIN ≤ 28V
1.00
15
–75
–25 25
75 125 175
TEMPERATURE (°C)
4412 G01
15
–75
–25 25
75 125 175
TEMPERATURE (°C)
4412 G02
0.95
–75
–25 25
75 125 175
TEMPERATURE (°C)
4412 G03
ILEAK vs Temperature
–0.2
–0.25
–0.3
–0.35
–0.4
–75
–25 25
75 125 175
TEMPERATURE (°C)
4412 G04
VG(ON) vs Temperature
7.05
8V ≤ VIN ≤ 28V
IGATE = 1µA
6.95
6.85
–75
–25 25
75 125 175
TEMPERATURE (°C)
4412 G05
VG(OFF) vs Temperature and IGATE
0.30
2.5V ≤ VIN ≤ 28V
0.20
0.10
0.00
–75
IGATE = –10µA
IGATE = –5µA
IGATE = 0µA
–25 25
75 125 175
TEMPERATURE (°C)
4412 G06
tG(ON) vs Temperature
106
3.6V ≤ VIN ≤ 28V
CGATE = 1nF
100
tG(OFF) vs Temperature
13.0
3.6V ≤ VIN ≤ 28V
CGATE = 1nF
12.5
IS(SNK) vs Temperature and VIN
11.5
VSTAT = VIN – 1.5V
11.0
VIN = 28V
VIN = 2.5V
10.5
94
–75
–25 25
75 125 175
TEMPERATURE (°C)
4412 G07
12.0
–75
–25 25
75 125 175
TEMPERATURE (°C)
4412 G08
For more information www.linear.com/LTC4412
10.0
–75
–25 25
75 125 175
TEMPERATURE (°C)
4412 G09
4412fb
5
5 Page 
LTC4412
typical applications
SENSE pin voltage rising above the battery voltage and
turning off the MOSFET before the Schottky diode turns
on. The factors that determine the magnitude of the voltage
droop are the auxiliary input rise time, the type of diode
used, the value of COUT and the load current.
Ideal Diode Control with a Microcontroller
Figure 4 illustrates an application circuit for microcon-
troller monitoring and control of two power sources. The
microcontroller’s analog inputs, perhaps with the aid of a
resistor voltage divider, monitors each supply input and
commands the LTC4412 through the CTL input. Back-to-
back MOSFETs are used so that the drain-source diode will
not power the load when the MOSFET is turned off (dual
MOSFETs in one package are commercially available).
With a logical low input on the CTL pin, the primary input
supplies power to the load regardless of the auxiliary
voltage. When CTL is switched high, the auxiliary input
will power the load whether or not it is higher or lower
than the primary power voltage. Once the auxiliary is
on, the primary power can be removed and the auxiliary
will continue to power the load. Only when the primary
voltage is higher than the auxiliary voltage will taking
CTL low switch back to the primary power, otherwise
the auxiliary stays connected. When the primary power
is disconnected and VIN falls below VLOAD, it will turn
on the auxiliary MOSFET if CTL is low, but VLOAD must
stay up long enough for the MOSFET to turn on. At a
minimum, COUT capacitance must be sized to hold up
VLOAD until the transition between the sets of MOSFETs
is complete. Sufficient capacitance on the load and low
or no capacitance on VIN will help ensure this. If desired,
this can be avoided by use of a capacitor on VIN to ensure
that VIN falls more slowly than VLOAD.
Load Sharing
Figure 5 illustrates an application circuit for dual battery
load sharing with automatic switchover of load from
batteries to wall adapter. Whichever battery can supply
the higher voltage will provide the load current until it is
discharged to the voltage of the other battery. The load will
then be shared between the two batteries according to the
capacity of each battery. The higher capacity battery will
provide proportionally higher current to the load. When
a wall adapter input is applied, both MOSFETs will turn
off and no load current will be drawn from the batteries.
The STAT pins provide information as to which input is
supplying the load current. This concept can be expanded
to more power inputs.
AUXILIARY POWER
SOURCE INPUT
AUXILIARY
P-CHANNEL MOSFETS
**
470k
MICROCONTROLLER
PRIMARY
P-CHANNEL MOSFETS
**
0.1µF
PRIMARY
POWER
SOURCE INPUT
1
2
LTC4412
VIN SENSE
GND GATE
6
5
3 CTL STAT 4
*DRAIN-SOURCE DIODE OF MOSFET
4412 F04
WALL
ADAPTER
INPUT
BAT1
TO LOAD
COUT
BAT2
*
1
2
LTC4412
VIN SENSE
GND GATE
6
5
3 CTL STAT 4
*
TO LOAD
COUT
VCC
470k STATUS IS HIGH
WHEN BAT1 IS
SUPPLYING
LOAD CURRENT
WHEN BOTH STATUS LINES ARE
HIGH, THEN BOTH BATTERIES ARE
SUPPLYING LOAD CURRENTS. WHEN
BOTH STATUS LINES ARE LOW THEN
WALL ADAPTER IS PRESENT
1
2
LTC4412
VIN SENSE
GND GATE
6
5
3 CTL STAT 4
VCC
470k
*DRAIN-SOURCE DIODE OF MOSFET
4412 F05
STATUS IS HIGH
WHEN BAT2 IS
SUPPLYING
LOAD CURRENT
Figure 4. Microcontroller Monitoring and Control
of Two Power Sources
Figure 5. Dual Battery Load Sharing with Automatic
Switchover of Load from Batteries to Wall Adapter
4412fb
For more information www.linear.com/LTC4412
11
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet LTC4412.PDF ] | |
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