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参数资料
| 型号： | SC804 |
| 厂商： | Semtech Corporation |
| 英文描述： | Fully Integrated Lithium-Ion Battery Charger System with Timer |
| 中文描述： | 完全集成的锂离子电池充电器系统的计时器 |
| 文件页数： | 2/21页 |
| 文件大小： | 548K |
| 代理商： | SC804 |
10
2007 Semtech Corp.
www.semtech.com
SC804
PRELIMINARY
POWER MANAGEMENT
Applications Information (Cont.)
NTC
COLD =
VCC × R
COLD = 0.6591 × VCC
R3 + R
COLD
work with standard thermistors available from numerous
vendors.
NTC pin voltage below VT
NTCDIS (nominally 0.6V) disables
the SC804 and resets the charge timer (with the FLTB pin
inactive). The NTC pin can be pulled down to ground by
an external n-channel FET transistor or processor GPIO to
disable or reset the SC804.
Note that the response of the SC804 to NTC pin voltage
above the high threshold and below the low threshold
is the same. Thus it is possible to congure the NTC
network with the battery pack thermistor between NTC
and VCC, and a xed resistor between NTC and ground.
This conguration may be useful if it is desired to reset the
charge timer (and the CHRGB output) when the battery
pack is removed (so the xed resistor pulls the NTC pin to
ground) while VCC is present.
Cold Temperature Offset (CTO)
The voltage applied to the CTO pin sets the NTC high
voltage (normally the cold temperature threshold) for the
NTC input. The default NTC high threshold (VT
NTCC×V
VCC)
can be selected by connecting the CTO pin to ground. If
it is desired to change this threshold, the voltage on the
CTO pin can be set between 0.5×V
VCC and 0.9×VVCC.
This feature is especially useful if a single PCB design
is needed to satisfy similar applications with different
requirements. The temperature range for normal charging
can be adjusted by adjusting resistor values on a divider
network without changing the NTC thermistor, which
is often enclosed in the battery pack. An example of a
typical application is shown in Figure 2.
NTC/CTO Design Example
The following example assumes the NTC network
conguration of Figure 2, with a xed resistor R3 connected
between NTC and VCC, and a battery NTC thermistor
RT connected between NTC and ground. The battery
temperature range over which charging is permitted is
specied to be 0°C through 40°C. The datasheet for the
selected NTC thermistor indicates that RT = 5.839k
Ω at
40°C, at RT = 26.49k
Ω at 0°C, with a dissipation constant
DC = 3mW. Designate R
HOT = 5.839kΩ and RCOLD =
26.49k
Ω.
Step 1: Select R3. For the normal (NTC thermistor to
ground) conguration, solve the NTC network voltage
divider for R3 to place the NTC voltage at 0.3×VCC when
RT = R
HOT.
or R3 = 2.333×R
HOT = 13.624kΩ exactly. The closest 1%
standard nominal value is R3 = 13.7k
Ω.
Step 2: Verify acceptable thermistor self heating. In
general, lower values of RT provide more noise immunity
for the NTC voltage, but at the expense of bias current
from the input adapter and power dissipation in the NTC
network. The dissipation constant is the power rating of
the thermistor resulting in a 1°C self heating error. The
greatest self-heating occurs at low thermistor resistance
(at high temperature).
Since temperature sensing
accuracy matters only at the charging temperature range
thresholds, self heating is assessed only at the worst case
high temperature threshold of +40°C.
For V
VCC = 5V,
the 40°C NTC network current I
NTC_HOT =
V
VCC/(R3 + RHOT) = 0.246mA.
Power dissipation in the
thermistor at this temperature, P
HOT = RHOT × (INTC_HOT)
2
=
0.38mW, for self heating of approximately 0.13°C. The
actual high temperature threshold will thus be lower by
0.13°C. This self-heating error is usually acceptable. If
it is not, then a thermistor with a greater R
HOT must be
chosen.
Step 3: Determine the desired high (cold) threshold.
Compute the NTC network resistor divider voltage, as a
function of V
VCC, at the cold temperature threshold.
Step 4: Congure CTO. If NTC
COLD is sufciently close
to the default cold threshold (VT
NTCC×V
VCC), then simply
connect CTO to ground, disabling the CTO function, to
complete the design. But in this example it is not, so the
voltage on CTO must be set to 0.6591×V
VCC. The simple
resistive voltage divider network of Figure 2 can be used
to obtain the desired CTO voltage.
0.3 × VCC =
VCC × R
HOT
R3 + R
HOT
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相关代理商/技术参数 |
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|---|---|
| SC804A | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Fully Integrated 4.4V Lithium-Ion Battery Charger System with Timer |
| SC804AMLTRT | 功能描述:IC LI-ION BATT CHARGER 16-MLPQ 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 |
| SC804EVB | 制造商:SEMTECH 制造商全称:Semtech Corporation 功能描述:Fully Integrated 4.4V Lithium-Ion Battery Charger System with Timer |
| SC804IML.TRT | 功能描述:IC LI-ION BATTERY CHRGR 16MLPQ 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 |
| SC804IMLTRT | 制造商:Semtech Corporation 功能描述:Battery Charger Li-Ion 1500mA 4.2V 16-Pin MLPQ EP T/R |
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