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PDF LTC1479CG Data sheet ( Hoja de datos )
| Número de pieza | LTC1479CG | |
| Descripción | PowerPath Controller for Dual Battery Systems | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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LTC1479
PowerPath Controller
for Dual Battery Systems
FEATURES
s Complete Power Path Management for Two
Batteries, DC Power Source, Charger and Backup
s Compatible with Li-Ion, NiCd, NiMH and Lead-Acid
Battery Chemistries
s “3-Diode” Mode Ensures Powers is Available
under “Cold Start” Conditions
s All N-Channel Switching Reduces Power Losses
s Capacitor and Battery Inrush Current Limited
s “Seamless” Switching Between Power Sources
s Independent Charging and Monitoring of Two
Battery Packs
s New, Small FootpUrint, 36-Lead SSOP Package
APPLICATIONS
s Notebook Computer Power Management
s Portable Instruments
s Handheld Terminals
s Portable Medical Equipment
s Portable Industrial Control Equipment
DESCRIPTION
The LTC®1479 is the “heart” of a total power management
solution for single and dual battery notebook computers
and other portable equipment. The LTC1479 directs power
from up to two battery packs and a DC power source to the
input of the main system switching regulator. It works in
concert with related LTC power management products
(e.g. LTC1435, LT®1511, etc.) to create a total system
solution; starting from the batteries and the DC power
source, and ending at the input of each of the computer’s
complex loads. A system-provided power management
µP monitors and actively directs the LTC1479.
The LTC1479 uses low loss N-channel MOSFET switches
to direct power from three main sources. An adaptive
current limiting scheme reduces capacitor and battery
inrush current by controlling the gates of the MOSFET
switches during transitions. The LTC1479 interfaces di-
rectly to the LT1510, LT1511 and LT1620/LTC1435 bat-
tery charging circuits.
, LTC and LT are registered trademarks of Linear Technology Corporation.
PowerPath is a trademark of Linear Technology Corporation.
TYPICAL APPLICATION
Dual Battery PowerPathTM Controller System Block Diagram
AC
ADAPTER
BAT1
BAT2
DCIN
SW A/B
SW C/D
SW G
SW H
SW E/F
BATTERY CHARGER
(LT1510/LT1511/
LT1620/LTC1435)
LTC1479
PowerPath CONTROLLER
RSENSE
+
CIN
HIGH EFFICIENCY
DC/DC SWITCHING
REGULATOR
(LTC1435/LTC1438
ETC.)
BACKUP
REGULATOR
(LT1304)
STATUS &
CONTROL
POWER
MANAGEMENT
µP
1479 TA01
5V
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
LTC1479
DCIN Supply Current
350
MODE 1, DCDIV = 1.5V
300
NO OTHER POWER
TJ = 25°C
250
200
150
100
50
BAT1 Supply Current
350
MODE 5
300
NO OTHER POWER
TJ = 25°C
250
200
150
100
50
BAT2 Supply Current
350
MODE 6
300
NO OTHER POWER
TJ = 25°C
250
200
150
100
50
0
0 5 10 15 20 25 30 35
DCIN SUPPLY VOLTAGE (V)
1479 G01
0
05
10 15 20 25 30 35
BAT1 SUPPLY VOLTAGE (V)
1479 G02
0
05
10 15 20 25 30 35
BAT2 SUPPLY VOLTAGE (V)
1479 G03
VBKUP Supply Current
70
MODE 8
60
NO OTHER POWER
TJ = 25°C
50
VGG Supply Voltage
44
MODE 1
42 VDCIN = 24V
40
40 38
30 36
20 34
10 32
0
05
10 15 20 25 30 35
VBKUP SUPPLY VOLTAGE (V)
1479 G04
VCC Supply Voltage
4.0
MODE 1
3.9 VDCIN = 24V
30
– 50 – 25 0 25 50 75 100 125
JUNCTION TEMPERATURE (°C)
1479 G05
VCCP Supply Voltage
6.5
MODE 1
6.0 VDCIN = 24V
3.8 5.5
3.7 5.0
3.6 4.5
3.5 4.0
3.4 3.5
3.3
– 50 – 25 0 25 50 75 100 125
JUNCTION TEMPERATURE (°C)
1479 G06
3.0
– 50 – 25 0 25 50 75 100 125
JUNCTION TEMPERATURE (°C)
1479 G07
5
5 Page 
U
OPERATION
This scheme allows capacitors and MOSFET switches of
differing sizes and current ratings to be used in the same
system without circuit modifications.
After the transition period has passed, the VGS of both
MOSFETs in the selected switch pair rises to approxi-
mately 6V. The gate drive is set at 6V to provide ample
overdrive for logic level MOSFET switches without ex-
ceeding their maximum VGS rating.
Internal Power Supplies
Two internal supplies provide power for the control logic
and power source monitoring functions. The VCCP logic
supply is approximately 5V and provides power for the
majority of the internal logic circuitry. The VCC supply is
approximately 3.60V and provides power for the VGG
switching regulator control circuitry and the gate drivers.
The VCC supply has an undervoltage lockout circuit which
minimizes power consumption in the event of a total loss
of system power; i.e., when all available power sources fall
below approximately 4.5V.
DCIN Voltage Monitoring
The DCIN input is continuously monitored via a two
resistor ladder connected between the DCIN pin and the
DCDIV input. The input threshold is 1.215V (rising edge)
with approximately – 35mV hysteresis. The use of a defini-
tive voltage threshold ensures that the DC supply is not
only connected but “healthy” before being attached to the
DC/DC converter input.
Battery Voltage Monitoring
The LTC1479 has the ability to independently monitor both
battery packs. (Because of this, one battery pack may be
discharged as the other is being charged.)
A low-battery detector signals when the selected battery
pack has dropped to the level where a shutdown sequence
should be initiated or the other battery pack engaged.
LTC1479
Battery Charging Management Functions
The LTC1479 directly interfaces with LT1510/LT1511
battery charger circuits. Two gate drive circuits control
the two back-to-back N-channel switch pairs, SW G and
SW H, under logic (CHGSEL) control to connect the
output of the charger to the selected battery pack. Break-
before-make action ensures that current does not pass
from one battery pack to the other during switch-over of
the charger output. The CHGSEL input also simulta-
neously switches the positive terminal of the selected
battery pack to the top of the voltage feedback resistor
ladder in the charger system through the CHGMON pin.
Backup Supply Interface
Power for the LTC1479 is obtained from the backup
supply when power is unavailable from the three main
sources of power.
Interface to Companion Microprocessor
A companion µP must be used in conjunction with the
LTC1479 to provide overall control of the power manage-
ment system. The LTC1479 communicates with the µP by
means of five logic inputs and two logic outputs as
described in Table 1.
Table 1. LTC1479 µP Interface Inputs and Outputs
INPUT
ACTION
DCIN/BAT Logic High Required to Connect a Good DC Supply
BATDIS
Logic Low Disconnects the Battery from the System
BATSEL
Selects Which Battery is Connected to the System
(Logic High Selects BAT1; Logic Low Selects BAT2)
CHGSEL
Selects Which Battery is Charged and Monitored
(Logic High Selects BAT1; Logic Low Selects BAT2)
3DM Forces the Main Three Power Path Switches Into
“3-Diode Mode.” See Applications Information Section
OUTPUT
ACTION
DCINGOOD Logic High When a Good DC Supply is Present
LOBAT
Logic Low When Selected Battery Voltage is Low
11
11 Page | ||
| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LTC1479CG.PDF ] | |
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