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参数资料
| 型号： | LTC1734ES6-4.1#TR |
| 厂商： | Linear Technology |
| 文件页数： | 9/12页 |
| 文件大小： | 0K |
| 描述： | IC BATT CHRGR LI-ION LIN SOT23-6 |
| 标准包装： | 2,500 |
| 功能： | 充电管理 |
| 电池化学： | 锂离子，镍镉，镍氢 |
| 电源电压： | 4.55 V ~ 8 V |
| 工作温度： | -40°C ~ 85°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | SOT-23-6 细型，TSOT-23-6 |
| 供应商设备封装： | TSOT-23-6 |
| 包装： | 带卷 (TR) |
| 其它名称： | LTC1734ES6-4.1TR |
LTC1734
APPLICATIO N S I N FOR M ATIO N
Monitoring Charge Current
The voltage on the PROG pin indicates the charge current
as a proportion of the maximum current set by the
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 charge 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.
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 can be between approximately 50mA
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
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 AC stability (see
Stability section)
With low supply voltages, the PNP saturation voltage
(V CESAT ) becomes important. The V CESAT must be less
than the minimum supply voltage minus the maximum
voltage drop across the internal sense resistor and bond
wires (0.1 ? ) and battery float voltage. If the PNP transis-
tor 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 because some of the current from the
DRIVE pin could be pulled from the battery through the
forward biased collector base junction.
For example, to program a charge current of 500mA with
a minimum supply voltage of 4.75V, the minimum operat-
ing V CE is:
V CE(MIN) (V) = 4.75 – (0.5)(0.1) – 4.2 = 0.5V
The actual battery charge current (I BAT ) is slightly smaller
than the expected charge current because the charger
senses the emitter current and the battery charge current
will be reduced by the base current. In terms of β (I C /I B ),
I BAT can be calculated as follows:
I BAT (A) = 1000 ? I PROG [ β /( β + 1)]
If β = 50, then I BAT is 2% low. If desired, the 2% loss can
be compensated for by increasing I PROG by 2%.
Another important factor to consider when choosing the
PNP pass transistor is the power handling capability. The
transistor’s data sheet will usually give the maximum rated
power dissipation at a given ambient temperature with a
power derating for elevated temperature operation. The
maximum power dissipation of the PNP when charging is:
P D(MAX) (W) = I BAT (V DD(MAX) – V BAT(MIN) )
V DD(MAX) is the maximum supply voltage and V BAT(MIN) is
the minimum battery voltage when discharged.
PNP beta greater than 23. If lower beta PNP transistors are
9
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相关代理商/技术参数 |
参数描述 |
|---|---|
| LTC1734LES6-4.2 | 制造商:Linear Technology 功能描述:Battery Charger Li-Ion/NiCD/NiMH 50mA to 180mA 4.2V 6-Pin TSOT-23 |
| LTC1734LES6-4.2#PBF | 制造商:Linear Technology 功能描述:Battery Charger Li-Ion/NiCD/NiMH 50mA to 180mA 4.2V 6-Pin TSOT-23 |
| LTC1734LES6-4.2#TR | 功能描述:IC CHARGER BATT CONSTV/I SOT23-6 RoHS:否 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:61 系列:- 功能:电源管理 电池化学:锂离子（Li-Ion）、锂聚合物（Li-Pol） 电源电压:4.35 V ~ 5.5 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:22-WFDFN 裸露焊盘 供应商设备封装:22-DFN（6x3）裸露焊盘 包装:管件 |
| LTC1734LES6-4.2#TRM | 功能描述:IC CHARGER BATT LIN LI-ION SOT23 RoHS:否 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:2,000 系列:Impedance Track™ 功能:燃料，电量检测计/监控器 电池化学:锂离子（Li-Ion） 电源电压:2.4 V ~ 2.6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:20-TSSOP（0.173"，4.40mm 宽） 供应商设备封装:20-TSSOP 包装:带卷 (TR) 产品目录页面:1020 (CN2011-ZH PDF) 配用:BQ27350EVM-ND - BQ27350EVM 其它名称:296-21665-2 |
| LTC1734LES6-4.2#TRMPBF | 功能描述:IC CHARGER BATT LIN LI-ION SOT23 RoHS:是 类别:集成电路 (IC) >> PMIC - 电池管理 系列:- 标准包装:1 系列:- 功能:充电管理 电池化学:锂离子（Li-Ion）、锂聚合物（Li-Pol） 电源电压:3.75 V ~ 6 V 工作温度:-40°C ~ 85°C 安装类型:表面贴装 封装/外壳:SC-74A，SOT-753 供应商设备封装:SOT-23-5 包装:剪切带 (CT) 产品目录页面:669 (CN2011-ZH PDF) 其它名称:MCP73831T-2ACI/OTCT |
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