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參數(shù)資料
| 型號(hào)： | LTC1734 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | Lithium-Ion Linear Battery Charger in SOT-23(鋰離子線性電池充電器（SOT-23封裝）) |
| 中文描述： | 鋰離子線性電池充電器采用SOT - 23（鋰離子線性電池充電器（采用SOT - 23封裝）） |
| 文件頁數(shù)： | 6/8頁 |
| 文件大?。?/td> | 140K |
| 代理商： | LTC1734 |
6
LTC1734
APPLICATIO
S I
N
FOR
ATIO
U
program resistor. The charge current is equal to 1000
(V
PROG
/R
PROG
) amps. This feature allows a microcontrol-
ler with an ADC to easily monitor charging current and if
desired, manually shut down the charger at the appropri-
ate time. See Figure 1 for an example. The minimum PROG
pin current is about 3
μ
A (I
PROGPU
)
Errors in the charge current monitor voltage on the PROG
pin are inversely proportional to battery current and can be
statistically approximated as follows:
One Sigma Error(%)
1 + 0.3/I
BAT
(A)
Dynamic loads on the battery will cause transients to
appear on the PROG pin. Should they cause excessive
errors in charge current monitoring, a simple RC filter as
shown in Figure 2 can be used to filter the transients. The
filter will also quiet the PROG pin to help prevent inadvert-
ent momentary entry into the manual shutdown mode.
Because the PROG pin is in a closed-loop signal path the
pole frequency must be kept high enough to maintain
adequate AC stability. This means that the maximum
resistance and capacitance presented to the PROG pin
must be limited. See the Stability section for more details.
W
U
Constant Current Source
The LTC1734 can be used as a constant current source by
disabling the voltage control loop as shown in Figure 3.
This is done by pulling the BAT pin below the preset float
voltages of 4.1V or 4.2V by grounding the BAT pin. The
program resistor will determine the output current. The
output current range is between approximately 200mA
and 700mA, depending on the maximum power rating of
the external PNP pass transistor.
External PNP Transistor
The external PNP pass transistor must have adequate
beta, low saturation voltage and sufficient power dissipa-
tion capability (including any heat sinking, if required).
To provide 700mA of charge current with the minimum
available base drive of approximately 30mA requires a
PNP beta greater than 23. If lower beta PNP transistors are
used, more base current is required from the LTC1734.
This can result in the output drive current limit being
reached, or thermal shutdown due to excessive power
dissipation. Excessive beta can affect stability (see Stabil-
ity section)
With low input voltages, the PNP saturation voltage
(V
CESAT
) becomes important. The V
CESAT
must be less
than the minimum input voltage minus the voltage drop
across the internal sense resistor minus the battery float
voltage. If the PNP transistor can not achieve the low
saturation voltage required, base current will dramatically
increase. This is to be avoided for a number of reasons:
output drive may reach current limit resulting in the
charger’s characteristics to go out of specifications,
excessive power dissipation may force the IC into thermal
shutdown, or the battery could become discharged be-
cause some of the current from the DRIVE pin could be
pulled from the battery through the forward biased collec-
tor base junction.
Figure 2. Logic Control Programming of Output Current to 0mA, 200mA, 500mA or 700mA
Figure 1. Interfacing with a Microcontroller
LTC1734
PROG
μ
C
R
PROG
ADC INPUT
1734 F01
OPEN DRAIN
OR TOTEM
POLE OUTPUT
V
IN
5V
CHARGE
CURRENT
MONITOR
CHARGE
CURRENT
MONITOR
7.5k
Q2
2N7002
CONTROL 2
FZT549
I
BAT
1734 F02
SINGLE
Li-Ion
BATTERY
10
μ
F
GND
PROG
DRIVE
BAT
2
4
6
5
LTC1734
V
CC
I
SENSE
3
1
1
μ
F
0.1
μ
F TO
0.5
μ
F
1k
OPTIONAL FILTER
3k
Q1
2N7002
CONTROL 1
CHARGE CURRENT
0
200mA
500mA
700mA
CONTROL 1
LOW
LOW
HIGH
HIGH
CONTROL 2
LOW
HIGH
LOW
HIGH
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| LTC1734ES6-4.1#TR | 功能描述:IC BATT CHRGR LI-ION LIN SOT23-6 RoHS:否 類別:集成電路 (IC) >> PMIC - 電池管理 系列:- 標(biāo)準(zhǔn)包裝:61 系列:- 功能:電源管理 電池化學(xué):鋰離子（Li-Ion）、鋰聚合物（Li-Pol） 電源電壓:4.35 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:22-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:22-DFN（6x3）裸露焊盤 包裝:管件 |
| LTC1734ES6-4.1#TRM | 功能描述:IC BATT CHRGR LI-ION LIN SOT23-6 RoHS:否 類別:集成電路 (IC) >> PMIC - 電池管理 系列:- 標(biāo)準(zhǔn)包裝:61 系列:- 功能:電源管理 電池化學(xué):鋰離子（Li-Ion）、鋰聚合物（Li-Pol） 電源電壓:4.35 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:22-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:22-DFN（6x3）裸露焊盤 包裝:管件 |
| LTC1734ES6-4.1#TRMPBF | 功能描述:IC BATT CHRGR LI-ION LIN SOT23-6 RoHS:是 類別:集成電路 (IC) >> PMIC - 電池管理 系列:- 標(biāo)準(zhǔn)包裝:61 系列:- 功能:電源管理 電池化學(xué):鋰離子（Li-Ion）、鋰聚合物（Li-Pol） 電源電壓:4.35 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:22-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:22-DFN（6x3）裸露焊盤 包裝:管件 |
| LTC1734ES6-4.1#TRPBF | 功能描述:IC BATT CHRGR LI-ION LIN SOT23-6 RoHS:是 類別:集成電路 (IC) >> PMIC - 電池管理 系列:- 標(biāo)準(zhǔn)包裝:61 系列:- 功能:電源管理 電池化學(xué):鋰離子（Li-Ion）、鋰聚合物（Li-Pol） 電源電壓:4.35 V ~ 5.5 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:22-WFDFN 裸露焊盤 供應(yīng)商設(shè)備封裝:22-DFN（6x3）裸露焊盤 包裝:管件 |
| LTC1734ES6-4.2 | 制造商:Linear Technology 功能描述:Battery Charger Li-Ion/NiCD/NiMH 200mA to 700mA 4.2V 6-Pin TSOT-23 制造商:Linear Technology 功能描述:0.9 A BATTERY CHARGE CONTROLLER, PDSO6 |
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