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參數(shù)資料
| 型號： | ADP3502 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | CDMA Power Management System |
| 中文描述： | CDMA的電源管理系統(tǒng) |
| 文件頁數(shù)： | 32/36頁 |
| 文件大?。?/td> | 714K |
| 代理商： | ADP3502 |
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REV. 0
–32–
ADP3502
Setting the Charge Current
The ADP3502 will control the charging operations when re-
quested by the software. It includes a complete constant current/
voltage single-cell lithium charge controller, as well as input
current monitoring for the charger and voltage regulators. The
ADP3502 will default to the lowest charge voltage of 3.50 V. To
reach final charge on standard lithium batteries, the software
must select one of the programmed values from this data sheet.
The current comparator of the ADP3502 senses the voltage
drop across an external sense resistor to control the average cur-
rent for charging a battery. The voltage drop can be adjusted
from 60 mV to 210 mV, giving a charging current limit from
300 mA to 1.05 A with a 0.2
sense resistor. For lithium
batteries, selecting the sense resistor, R
SENSE
, programs the
charge current. Use the following equation to select the current
sense resistor,
R
SENSE
. The maximum battery charge current,
I
CHGR
, must be known.
R
mV
I
SENSE
CHGR
=
210
Similarly, the end of charge current can be calculated from the
low current limit threshold of 60 mV.
I
mV
R
LOW
SENSE
=
60
CHARGER DIODE SELECTION
The diode, D3, shown in the Figure 18, is used to prevent the bat-
tery from discharging through the adapter supply. Choose a diode
with a low leakage current but with a current rating high enough
to handle the battery current and a voltage rating greater than
VBAT. The blocking diode is required for lithium battery types.
External Pass Transistor Selection
The ADP3502 drives an external PNP pass transistor. The
BASE pin drives the base of the transistor. The driver can draw
up to 35 mA from the base of the pass device. The PNP pass
transistor must meet specifications for:
Current gain
Power dissipation
Collector current
The current gain, hfe, influences the maximum output current
the circuit can deliver. The largest guaranteed output current is
given by I
CHGR
(max) = 35 mA hfe (min). To ensure proper
operation, the minimum
V
BE
the ADP3502 can provide must be
enough to turn on the PNP. The available base drive voltage
can be estimated using the following:
V
V
V
V
BE
ADAPTER
DIODE
BASE
=
–
–
where
V
ADAPTER
(min) is the minimum adapter voltage,
V
BASE
is
the base drive voltage, and
V
SENSE
is the maximum high current
limit threshold voltage. The difference between the adapter
voltage (
V
ADAPTER
) and the final battery voltage (
V
BAT
) must
exceed the voltage drop due to the blocking diode, the sense
resistor, and the saturation voltage of the PNP at the maxi-
mum charge current, where:
V
V
V
V
V
CE(SAT)
ADAPTER
DIODE
SENSE
BAT
=
–
–
–
The thermal characteristics of the PNP must be considered next.
The transistor’s rated power dissipation must exceed the actual
power dissipated in the transistor. The worst-case dissipation
can be determined using:
=
(
It should be noted that the adapter voltage could be either preregu-
lated or nonregulated. When preregulated, the difference between
the maximum and minimum adapter voltage is probably not
significant. When unregulated, the adapter voltage can have a
wide range specified. However, the maximum voltage specified
is usually with no load applied. Therefore, the worst-case power
dissipation calculation will often lead to an overspecified pass
device. In either case, it is best to determine the load character-
istics of the adapter to optimize the charger design.
P
I
DISS
CHGR
)
×
)
V
V
V
ADAPTER MAX
DIODE
BAT
–
–
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| ADP3502ASU | CDMA Power Management System |
| ADP3510 | Secondary Over-Voltage Protection for 2-4 cell in series Li-Ion/Poly (4.40V) 8-SM8 -40 to 110 |
| ADP3510ARU | Secondary Over-Voltage Protection for 2-4 cell in series Li-Ion/Poly (4.40V) 8-SM8 -40 to 110 |
| ADP3522 | GSM Power Management System |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| ADP3502ASU | 制造商:AD 制造商全稱:Analog Devices 功能描述:CDMA Power Management System |
| ADP3502ASU-REEL | 制造商:Analog Devices 功能描述:CDMA Power Management System 64-Pin TQFP T/R |
| ADP3510 | 制造商:AD 制造商全稱:Analog Devices 功能描述:CDMA Power Management System |
| ADP3510ARU | 制造商:AD 制造商全稱:Analog Devices 功能描述:CDMA Power Management System |
| ADP3510ARU-REEL7 | 制造商:Analog Devices 功能描述: |
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