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參數(shù)資料
| 型號： | LT3651IUHE-4.1#TRPBF |
| 廠商： | LINEAR TECHNOLOGY CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | BATTERY CHARGE CONTROLLER, 1100 kHz SWITCHING FREQ-MAX, PQCC36 |
| 封裝： | 5 X 6 MM, 0.75 MM HEIGHT, LEAD FREE, PLASTIC, QFN-36 |
| 文件頁數(shù)： | 10/22頁 |
| 文件大小： | 213K |
| 代理商： | LT3651IUHE-4.1#TRPBF |
LT3651-4.1/LT3651-4.2
18
365142fb
APPLICATIONS INFORMATION
with ground is recommended. Make Kelvin connections
to the battery and sense resistor.
Keep high current paths and transients isolated from
battery ground, to assure an accurate output voltage
reference. Effective grounding is achieved by considering
switched current in the ground plane, and careful compo-
nent placement and orientation can effectively steer these
high currents such that the battery reference does not get
corrupted. Figure 8 illustrates the high current, high speed
current loops. When the top switch is enabled (charge
loop), current flows from the input bypass capacitor (CIN)
through the switch and inductor to the battery positive
terminal. When the top switch is disabled (discharge loop),
current to the battery positive terminal is provided from
ground through the synchronous switch. In both cases,
these switched currents return to ground via the output
bypass capacitor (CBAT).
Power Considerations
The LT3651 packaging has been designed to efficiently
remove heat from the IC via the Exposed Pad on the
backside of the package, which is soldered to a copper
footprint on the PCB. This footprint should be made as
large as possible to reduce the thermal resistance of the
IC case to ambient air.
Consideration should be given for power dissipation and
overall efficiency in a LT3651 charger. A detailed analysis
is beyond the scope of the data sheet, however following
are general guidelines.
The major components of power loss are: conduction
and transition losses of the LT3651 switches; losses in
the inductor and sense resistors; and AC losses in the
decoupling capacitors. Switch conduction loss is fixed.
Transition losses are adjustable by changing switcher
frequency. Higher input voltages cause an increase in
transition losses, decreasing overall efficiency. However
transition losses are inversely proportional to switcher
oscillator frequency so lowering operating frequency
reduces these losses. But lower operating frequency
usually requires higher inductance to maintain inductor
ripple current (inversely proportional). Inductors with
larger values typically have more turns, increasing ESR
unless you increase wire diameter making them physically
larger. So there is an efficiency and board size trade-off.
Secondarily, inductor AC losses increase with frequency
and lower ripple reduces AC capacitor losses.
The following simple rules of thumb assume a charge
current of 4A and battery voltage of 3.6V, with 1MHz os-
cillator, 24mΩ sense resistor and 3.3μH/20mΩ inductor.
A 1% increase in efficiency represents a 0.2W reduction
in power loss at 85% overall efficiency. One way to do
this is to decrease resistance in the high current path. A
reduction of 0.2W at 4A requires a 12.5mΩ reduction in
resistance. This can be done by reducing inductor ESR.
It is also possible to lower the sense resistance (with a
reduction in RRNG/SS as well), with a trade-off of slightly
less accurate current accuracy. All high current board
traces should have the lowest resistance possible. Addition
of input current limit sense resistance reduces efficiency.
Charger efficiency drops approximately linearly with in-
creasing frequency all other things constant. At 15V VIN
there is a 1% improvement in efficiency for every 200kHz
reduction in frequency (100kHz to 1MHz); At 28V VIN, 1%
for every 100kHz.
Of course all of these must be experimentally confirmed
in the actual charger.
+
VIN
BOOST
SW
365142 F08
CIN
CHARGE
DISCHARGE
LT3651
CBOOST
RSENSE
CBAT
BATTERY
Figure 8
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LT3651IUHE-8.2#PBF | 制造商:Linear Technology 功能描述:Battery Charger Li-Ion 4000mA 36-Pin QFN EP 制造商:Linear Technology 功能描述:IC CHRG MGMT LI-ION/LI-POL 36QFN 制造商:Linear Technology 功能描述:DP-Battery Charger, Monolithic 4A High Voltage Li-Ion Battery Charger |
| LT3651IUHE-8.2#TRPBF | 制造商:Linear Technology 功能描述:IC CHRG MGMT LI-ION/LI-POL 36QFN 制造商:Linear Technology 功能描述:DP-Battery Charger, Monolithic 4A High Voltage Li-Ion Battery Charger |
| LT3651IUHE-8.4#PBF | 制造商:Linear Technology 功能描述:Battery Charger Li-Ion 4000mA 36-Pin QFN EP 制造商:Linear Technology 功能描述:IC CHRG MGMT LI-ION/LI-POL 36QFN 制造商:Linear Technology 功能描述:DP-Battery Charger, Monolithic 4A High Voltage Li-Ion Battery Charger |
| LT3651IUHE-8.4#TRPBF | 制造商:Linear Technology 功能描述:IC CHRG MGMT LI-ION/LI-POL 36QFN 制造商:Linear Technology 功能描述:DP-Battery Charger, Monolithic 4A High Voltage Li-Ion Battery Charger |
| LT3652 | 制造商:LINER 制造商全稱:Linear Technology 功能描述:Power Tracking 2A Battery Charger for Solar Power |
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