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參數(shù)資料
| 型號： | SC804A |
| 廠商： | Semtech Corporation |
| 英文描述： | Fully Integrated 4.4V Lithium-Ion Battery Charger System with Timer |
| 中文描述： | 完全集成的4.4V鋰離子電池充電器系統(tǒng)的計時器 |
| 文件頁數(shù)： | 2/21頁 |
| 文件大小： | 550K |
| 代理商： | SC804A |
10
2005 Semtech Corp.
www.semtech.com
SC804A
PRELIMINARY
POWER MANAGEMENT
DRAFT
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 1oC 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 +40oC.
For V
VCC = 5V,
the 40oC 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 0.13oC. The
actual high temperature threshold will thus be lower by
0.13oC. 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.
or
Applications Information (Cont.)
the SC804A 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 SC804A.
Note that the response of the SC804A 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
0oC through 40oC. The datasheet for the selected NTC
thermistor indicates that RT = 5.839k
Ω at 40oC, at RT =
26.49k
Ω at 0oC, with a dissipation constant DC = 3mW.
Designate R
HOT = 5.839kΩ and RCOLD = 26.49kΩ.
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.
0.3 × VCC =
VCC × R
HOT
R3 + R
HOT
NTC
COLD =
VCC × R
COLD = 0.6591 × VCC
R3 + R
COLD
V
CTO = NTCCOLD
= 0.6591 × VCC =
VCC × R
CT2
R
CT1 + RCT2
R
CT1 = 1 0.6591 = 0.5172
R
CT2
0.6591
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| SC804EVB | Fully Integrated Lithium-Ion Battery Charger System with Timer |
| SC804IMLTRT | Fully Integrated Lithium-Ion Battery Charger System with Timer |
| SC804 | Fully Integrated Lithium-Ion Battery Charger System with Timer |
| SC805EVB | Miniature Integrated High Current Lithium-Ion Battery Charger |
| SC805IMLTRT | Miniature Integrated High Current Lithium-Ion Battery Charger |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| SC804AMLTRT | 功能描述:IC LI-ION BATT CHARGER 16-MLPQ RoHS:是 類別:集成電路 (IC) >> PMIC - 電池管理 系列:- 標準包裝:1 系列:- 功能:充電管理 電池化學:鋰離子（Li-Ion）、鋰聚合物（Li-Pol） 電源電壓:3.75 V ~ 6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SC-74A，SOT-753 供應商設備封裝:SOT-23-5 包裝:剪切帶 (CT) 產(chǎn)品目錄頁面:669 (CN2011-ZH PDF) 其它名稱:MCP73831T-2ACI/OTCT |
| SC804EVB | 制造商:SEMTECH 制造商全稱: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 類別:集成電路 (IC) >> PMIC - 電池管理 系列:- 標準包裝:1 系列:- 功能:充電管理 電池化學:鋰離子（Li-Ion）、鋰聚合物（Li-Pol） 電源電壓:3.75 V ~ 6 V 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SC-74A，SOT-753 供應商設備封裝:SOT-23-5 包裝:剪切帶 (CT) 產(chǎn)品目錄頁面:669 (CN2011-ZH PDF) 其它名稱: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 |
| SC805 | 制造商:SEMTECH 制造商全稱:Semtech Corporation 功能描述:Miniature Integrated High Current Lithium-Ion Battery Charger |
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