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PDF LTC4088-2 Data sheet ( Hoja de datos )
| Número de pieza | LTC4088-2 | |
| Descripción | High Efficiency Battery Charger/USB Power Manager | |
| Fabricantes | Linear Technology | |
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LTC4088-1/LTC4088-2
High Efficiency Battery
Charger/USB Power Manager
with Regulated Output Voltage
FEATURES
n Switching Regulator Makes Optimal Use of Limited
Power Available from USB Port to Charge Battery
and Power Application
n 180mΩ Internal Ideal Diode Plus External Ideal Diode
Controller Seamlessly Provide Low Loss Power Path
When Input Power is Limited or Unavailable
n Automatic Charge Current Reduction Maintains
3.6V Minimum VOUT
n Full Featured Li-Ion/Polymer Battery Charger
n VBUS Operating Range: 4.25V to 5.5V (7V Absolute
Maximum—Transient)
n 1.2A Maximum Input Current Limit
n 1.5A Maximum Charge Current with Thermal Limiting
n Bat-TrackTM Adaptive Output Control
n Slew Control Reduces Switching EMI
n Low Profile (0.75mm)14-Lead 4mm× 3mm DFN Package
U
APPLICATIO S
n Media Players
n Digital Cameras
n GPS
n PDAs
n Smart Phones
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
PowerPath and Bat-Track are trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
Protected by U.S. Patents, including 6522118
DESCRIPTIO
The LTC®4088-1/LTC4088-2 is a high efficiency USB
PowerPathTM controller and Li-Ion/Polymer battery
charger. It includes a synchronous switching input regu-
lator, a full-featured battery charger and an ideal diode.
Designed specifically for USB applications, the
LTC4088-1/LTC4088-2’s switching regulator auto-
matically limits its input current to either 100mA, 500mA
or 1A via logic control. The LTC4088-1 powers-up with the
charger off; the LTC4088-2 powers-up with the charger on.
The switching input stage provides power to VOUT where
power sharing between the application circuit and the
battery charger is managed. Charge current is automati-
cally reduced to maintain a regulated 3.6V VOUT during
low-battery conditions. As the battery is charged, VOUT
tracks VBAT for high efficiency charging. This feature al-
lows the LTC4088-1/LTC4088-2 to provide more power to
the application and eases thermal issues in constrained
applications.
An ideal diode ensures that system power is available
from the battery when the input current limit is reached
or if the USB or wall supply is removed.
The LTC4088-1/LTC4088-2 is available in the low profile
14-Lead 4mm × 3mm × 0.75mm DFN surface mount
package.
TYPICAL APPLICATIO
High Efficiency Battery Charger/USB Power Manager
WALL
USB
10µF
3.3µH
VBUS
D0
D1
D2
SW VOUT
VOUTS
LTC4088-1/LTC4088-2 GATE
CHRG
BAT
CLPROG PROG C/X GND NTC
8.2Ω
0.1µF
2.94k
499Ω
+
Li-Ion
SYSTEM
LOAD
10µF
408812 TA01a
Switching Regulator Efficiency to
System Load (POUT/PBUS)
100
90
80
70 BAT = 4.2V
60
BAT = 3.3V
50
40
30
20
10
0
0.01
VBUS = 5V
IBAT = 0mA
10x MODE
0.1
IOUT (A)
1
408812 TA01b
40881fb
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LTC4088-1/LTC4088-2
TYPICAL PERFOR A CE CHARACTERISTICS TA = 25°C unless otherwise noted.
Ideal Diode V-I Characteristics
1.0
INTERNAL IDEAL DIODE
WITH SUPPLEMENTAL
0.8
EXTERNAL VISHAY
Si2333 PMOS
0.6
INTERNAL IDEAL
DIODE ONLY
0.4
0.2
0
0
VBUS = 0V
VBUS = 5V
0.04 0.08 0.12 0.16
FORWARD VOLTAGE (V)
0.20
408812 G01
USB Limited Battery Charge
Current vs Battery Voltage
700
600
500
VBUS = 5V
RPROG = 1k
RCLPROG = 2.94k
400
300
200
100
5x USB SETTING,
0 BATTERY CHARGER SET FOR 1A
2.7 3.0 3.3 3.6
3.9
BATTERY VOLTAGE (V)
4.2
408812 G04
PowerPath Switching Regulator
Efficiency vs Output Current
100
VBAT = 3.8V
1x MODE
90
5x, 10x MODE
80
70
60
50
40
0.01
0.1
OUTPUT CURRENT (A)
1
408812 G07
Ideal Diode Resistance
vs Battery Voltage
0.25
0.20
INTERNAL IDEAL
DIODE
0.15
0.10
INTERNAL IDEAL DIODE
WITH SUPPLEMENTAL
0.05 EXTERNAL VISHAY
Si2333 PMOS
0
2.7 3.0 3.3 3.6 3.9 4.2
BATTERY VOLTAGE (V)
408812 G02
USB Limited Battery Charge
Current vs Battery Voltage
150
125
100
VBUS = 5V
RPROG = 1k
RCLPROG = 2.94k
75
50
25
1x USB SETTING,
BATTERY CHARGER SET FOR 1A
0
2.7 3.0 3.3 3.6 3.9
BATTERY VOLTAGE (V)
4.2
408812 G05
Battery Charging Efficiency vs
Battery Voltage with No External
Load (PBAT/PBUS)
90
RCLPROG = 2.94k
RPROG = 1k
88 IOUT = 0mA
5x CHARGING
EFFICIENCY
86
1x CHARGING
84 EFFICIENCY
82
80
2.7
3.0 3.3 3.6 3.9
BATTERY VOLTAGE (V)
4.2
408812 G08
Output Voltage vs Output Current
(Battery Charger Disabled)
4.50
VBAT = 4V
VBUS = 5V
5x MODE
4.25
4.00
VBAT = 3.4V
3.75
3.50
3.25
0
200 400 600 800
OUTPUT CURRENT (mA)
1000
408812 G03
Battery Drain Current
vs Battery Voltage
25
IOUT = 0µA
20
VBUS = 0V
15
10
VBUS = 5V
5 (SUSPEND MODE)
0
2.7 3.0 3.3 3.6 3.9 4.2
BATTERY VOLTAGE (V)
408812 G06
VBUS Current vs VBUS Voltage
(Suspend)
50
IOUT = 0mA
40
30
20
10
0
12 3 456
VBUS VOLTAGE (V)
408812 G09
40881fb
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U
OPERATIO
capacitor are connected from CLPROG to GND, the voltage
on CLPROG represents the average input current of the
switching regulator. As the input current approaches the
programmed limit, CLPROG reaches 1.188V and power
delivered by the switching regulator is held constant.
Several ratios of current are available which can be set
to correspond to USB low and high power modes with a
single programming resistor.
The input current limit is programmed by various com-
binations of the D0, D1 and D2 pins as shown in Table 1.
The switching input regulator can also be deactivated
(USB Suspend).
The average input current will be limited by the CLPROG pro-
gramming resistor according to the following expression:
( )IVBUS
=
IBUSQ
+
VCLPROG
RCLPROG
•
hCLPROG + 1
where IBUSQ is the quiescent current of the LTC4088-
1/LTC4088-2, VCLPROG is the CLPROG servo voltage in
current limit, RCLPROG is the value of the programming
resistor and hCLPROG is the ratio of the measured current
at VBUS to the sample current delivered to CLPROG. Refer
to the Electrical Characteristics table for values of hCLPROG,
VCLPROG and IBUSQ. Given worst-case circuit tolerances,
the USB specification for the average input current in 1x
or 5x mode will not be violated, provided that RCLPROG is
2.94k or greater.
Table 1 shows the available settings for the D0, D1 and
D2 pins.
Table 1. Controlled Input Current Limit
4088-1 4088-2 CHARGER
D0 D1 D2 D2 STATUS
0001
Off
0010
On
0101
Off
0110
On
1001
Off
1010
On
1101
Off
1110
Off
IBUS(LIM)
100mA (1x)
100mA (1x)
500mA (5x)
500mA (5x)
1A (10x)
1A (10x)
2.5mA (Susp High)
500µA (Susp Low)
Notice that when D0 is high and D1 is low, the switching
regulator is set to a higher current limit for increased
charging and power availability at VOUT. These modes will
LTC4088-1/LTC4088-2
typically be used when there is line power available from
a wall adapter.
While not in current limit, the switching regulator’s Bat-
Track feature will set VOUT to approximately 300mV above
the voltage at BAT. However, if the voltage at BAT is below
3.3V, and the load requirement does not cause the switching
regulator to exceed its current limit, VOUT will regulate at a
fixed 3.6V as shown in Figure 2. This will allow a portable
product to run immediately when power is applied without
waiting for the battery to charge.
If the load does exceed the current limit at VBUS, VOUT
will range between the no-load voltage and slightly below
the battery voltage, indicated by the shaded region of
Figure 2.
4.5
4.2
3.9
NO LOAD
3.6
3.3
300mV
3.0
2.7
2.4
2.4 2.7 3.0 3.3 3.6 3.9 4.2
BAT (V)
408812 F02
Figure 2. VOUT vs BAT
For very low-battery voltages, the battery charger acts like
a load and, due to limited input power, its current will tend
to pull VOUT below the 3.6V “Instant On” voltage. To prevent
VOUT from falling below this level, an undervoltage circuit
automatically detects that VOUT is falling and reduces the
battery charge current as needed. This reduction ensures
that load current and voltage are always prioritized and yet
delivers as much battery charge current as possible. (See
Over Programming the Battery Charger in the Applications
Information section).
The voltage regulation loop compensation is controlled by
the capacitance on VOUT. An MLCC capacitor of 10µF is
required for loop stability. Additional capacitance beyond
this value will improve transient response.
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| Páginas | Total 24 Páginas | |
| PDF Descargar | [ Datasheet LTC4088-2.PDF ] | |
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