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參數(shù)資料
| 型號(hào)： | LTC1731-4.2 |
| 廠商： | Linear Technology Corporation |
| 英文描述： | Lithium-Ion Linear Battery Charger Controller(4.2V鋰離子線性電池充電器) |
| 中文描述： | 鋰離子線性電池充電控制器（4.2V的鋰離子線性電池充電器） |
| 文件頁(yè)數(shù)： | 6/8頁(yè) |
| 文件大?。?/td> | 154K |
| 代理商： | LTC1731-4.2 |
6
LTC1731-4.2
threshold voltage. The DRV pin will then be pulled up to
V
CC
and turn off the external P-channel MOSFET. The
internal timer is reset in the shutdown mode.
Programming Charge Current
The formula for the battery charge current (see Block
Diagram) is:
I
BAT
= (I
PROG
)(800
/R
SENSE
)
= (2.457V/R
PROG
)(800
/R
SENSE
)
where R
PROG
is the total resistance from the PROG pin to
ground.
For example, if 0.5A charge current is needed, select a
value for R
SENSE
that will drop 100mV at the maximum
charge current. R
SENSE
= 0.1V/0.5A = 0.2
, then calculate:
R
PROG
= (2.457V/500mA)(800
/0.2
) = 19.656k
For best stability over temperature and time, 1% resistors
are recommended. The closest 1% resistor value is 19.6k.
Programming the Timer
The programmable timer is used to terminate the charge.
The length of the timer is programmed by an external
capacitor at the TIMER pin. The total charge time is:
Time = (3 Hours)(C
TIMER
/0.1
μ
F)
The timer starts when the input voltage greater than 4.1V
is applied and the program resistor is connected to ground.
After a time-out occurs, the CHRG output will turn into a
high impedance state to indicate that the charging has
stopped. Connecting the TIMER pin to V
CC
disables the
timer and also puts the charger into a constant-current
mode. To only disable the timer function, short the TIMER
pin to GND.
CHRG Status Output Pin
When the charge cycle starts, the CHRG pin is pulled down
to ground by an internal N-channel MOSFET that can drive
an LED. When the battery current drops to 10% of the full-
scale current (
C
/10), the N-channel MOSFET is turned off
and a weak 100
μ
A current source to ground is connected
to the CHRG pin. After a time-out occurs, the pin will go
into a high impedance state. By using two different value
pull-up resistors, a microprocessor can detect three states
APPLICATIO
S I
N
FOR
ATIO
U
W
U
from this pin (charging,
C
/10 and stop charging). See
Figure 1.
When the LTC1731-4.2 is in charge mode, the CHRG pin
is pulled down by an internal N-channel MOSFET. To de-
tect this mode, force the digital output pin, OUT, high and
measure the voltage at the CHRG pin. The N-channel
MOSFET will pull the pin low even with a 1k pull-up resis-
tor. Once the charge current drops to 10% of the full-scale
current (
C
/10), the N-channel MOSFET is turned off and a
100
μ
A current source is connected to the CHRG pin. The
IN pin will then be pulled high by the 1k pull-up. By forcing
the OUT pin into a high impedance state, the current
source will pull the pin low through the 100k resistor.
When the internal timer has expired, the CHRG pin will
change to high impedance state and the 100k resistor will
then pull the pin high to indicate the charging has stopped.
End of Charge (C/10)
The LTC1731-4.2 includes a comparator to monitor the
charge current to detect an end-of-charge condition. When
the battery current falls below 10% of full scale, the
comparator trips and turns off the N-channel MOSFET at
the CHRG pin and switches in a 100
μ
A current source to
ground. After an internal time delay of 300ms, this state is
then latched. This delay will help prevent false triggering
due to transient currents. The end-of-charge comparator
is disabled in trickle charge mode.
Gate Drive
Typically the LTC1731-4.2 controls an external P-channel
MOSFET to supply current to the battery. The DRV pin is
internally clamped to 6.5V below V
CC
. This feature allows
low voltage P-channel MOSFETs with gate to source
breakdown voltage rated at 8V to be used.
1k
100k
CHRG
1731 F01
V
CC
LTC1731-4.2
V
+
V
DD
OUT
μ
PROCESSOR
IN
2
7
Figure 1. Microprocessor Interface
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| LTC1731EMS8-4.1 | 功能描述:IC CTRLR BATT CHRGR LI-ION 8MSOP 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 |
| LTC1731EMS8-4.1#PBF | 功能描述:IC CTRLR BATT CHRGR LI-ION 8MSOP 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 |
| LTC1731EMS8-4.1#TR | 功能描述:IC CTRLR BATT CHRGR LI-ION 8MSOP 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 |
| LTC1731EMS8-4.1#TRPBF | 功能描述:IC CTRLR BATT CHRGR LI-ION 8MSOP 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 |
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