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參數(shù)資料
| 型號： | Si9731 |
| 廠商： | Vishay Intertechnology,Inc. |
| 英文描述： | μP Controlled Battery Charger For 1-Cell Li-ion or 1-Cell to 3-Cell NiCd/NiMH Batteries(用于1節(jié)鋰電池或1-3節(jié)鎳氫/鎳鎘電池的μP控制的電池充電器) |
| 中文描述： | 微處理器控制的電池充電器1節(jié)鋰離子電池或1節(jié)至3節(jié)鎳鎘/鎳氫電池（用于1節(jié)鋰電池或1-3節(jié)鎳氫/鎳鎘電池的微處理器控制的電池充電器） |
| 文件頁數(shù)： | 8/9頁 |
| 文件大?。?/td> | 57K |
| 代理商： | SI9731 |
Si9731
Vishay Siliconix
www.vishay.com
8
Document Number: 71321
S-02258
—
Rev. A, 28-Sep-00
Si9731 is a chemistry independent battery charger designed
for use with a system processor. For example, Si9731 can be
integrated within a cellular phone whereby the fast charge and
trickle (slow) charge modes can be software controlled by the
DSP. The device is designed to charge 1-cell Li-ion or 1-cell to
3-cell NiCd/NiMH batteries. A regulated or unregulated
external dc power source such as a wall adapter rated at
typically 4.5 V to 12 V is connected to Si9731
’
s V
CHARGER
input pin. Note that a typical low cost wall adaptor is comprised
of a transformer, bridge rectifier and a reservoir capacitor. The
wall adaptor
’
s output voltage decreases linearly with increase
in output current. When Si9731 is fast charging the battery, the
wall adaptor
’
s output voltage tracks the battery voltage plus
the voltage drop across Q1 (charging current times MOSFET
Q1
’
s r
DS(on)
, see Figure 1). The key features of Si9731 are
described below.
Since the under voltage lock out (UVLO) point of Si9731 is
2.6 V (typical) , it is essential to keep the charger voltage above
this level under all conditions, especially for fast charging of
single cell NiCd/NiMH. One simple solution is adding a
external resistor between V
BAT+
pin and the battery, which
creates extra voltage drop to elevate the charger voltage. The
value of the resistor is affected by the output V-I characteristic
of the ac charger.
Trickle Charge
The charge path is via n-channel MOSFETs Q1 or Q2 (see
applications circuit of Figure 1). Si9731 defaults to trickle (slow)
charge mode if the battery voltage is too low to power the main
processor. With the main processor unable to drive the
MAINCHARGEEN pin as well as the TRICKLECHARGEEN
pins, Q1 is turned
“
OFF
”
preventing fast charging. Meanwhile
n-channel MOSFET Q2 turns
“
ON
”
and establishes a trickle
charge path from the external power source V
CHARGER
to the
battery. The trickle charge current is set by an external current
limiting resistor, R
ext
, and is approximately I
TRICKLE
=
(V
CHARGER
- V
BAT+
)/R
ext
. Once the battery voltage charges
up to minimum battery operating voltage 3.4 V, the internal
latch is triggered and the CHARGERPOWER_ON output
changes state to wake up the processor. The processor is now
able to disable trickle charge mode by taking the
TRICKLECHARGEEN pin high while taking control of fast
charging via the MAINCHARGEEN pin.
Fast Charge
Fast charging is accomplished by the low
“
ON
”
resistance
MOSFET, Q1. The application microprocessor is able to
“
Pulse Charge
”
the battery via the MAINCHARGEREN control
input of Si9731. The processor monitors the battery voltage
via the system A/D converter and varies the pulse charging
duty cycle accordingly to maintain fast charging. Note that
even though charging current may be sufficiently high, pulse
charging with short
“
ON
”
time and long
“
OFF
”
time ensures that
heat generation due to thermal heating is reduced.
In the case of NiCd or NiMH batteries, one of several charge
termination schemes may be used to terminate charge. For
example, the processor may disable fast charging by sensing
V or dV/dt at the V
BAT+
output or by monitoring the
temperature differential
T of the battery. Following fast
charge, trickle charge may be enabled to
“
top off
”
the battery.
When charging a 1-cell Li-ion battery, fast charging will operate
in two modes, constant current mode followed by constant
voltage mode. In the constant current mode, a discharged
Li-ion battery is charged with constant current available from
the external dc source. The MOSFET pass transistor (Q1) may
be pulsed
“
ON
”
and
“
OFF
”
at varying duty cycle by the control
signal present at the MAINCHARGEEN input pin. Once the
battery voltage reaches it
’
s termination voltage of 4.1 V or
4.2 V (depending on the connection of the 4.1-V
TAP
), Si9731
may be placed in the
“
Constant Voltage
”
charging mode by
taking the CVMODE pin high . Taking CVMODE pin high
disables trickle charging and enables the internal battery
voltage divider by turning ON Q5. Then the error amplifier will
compare divided V
BAT+
voltage against an internal precision
1.3-V bandgap reference voltage (see Figure 1). The output of
the error amplifier drives the pass transistor Q1 to maintain
V
BAT+
at the regulated termination voltage. This operation is
same as a linear regulator.
True Load Disconnect
Both the fast charge FET (Q1 in Figure 1) and trickle charge
FET (Q2 in Figure 1) incorporate a floating body diode. In their
“
OFF
”
state both FETs block current bidirectionally. Note that
because of the reverse blocking switches, a Schottky diode in
series with the external V
CHARGER
power supply is not
required.
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相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| SI9731_09 | 制造商:VISHAY 制造商全稱:Vishay Siliconix 功能描述:uP Controlled Battery Charger for 1-Cell Li-ion or 1-Cell to 3-Cell NiCd/NiMH Batteries |
| SI9731DB | 功能描述:電池管理 SI9731 Demo Board RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
| SI9731DQ | 制造商:VISHAY 制造商全稱:Vishay Siliconix 功能描述:uP Controlled Battery Charger for 1-Cell Li-ion or 1-Cell to 3-Cell NiCd/NiMH Batteries |
| SI9731DQ-T1 | 功能描述:電池管理 Battery Charger RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
| SI9731DQ-T1-E3 | 功能描述:電池管理 Micro Controlled Battery Charger RoHS:否 制造商:Texas Instruments 電池類型:Li-Ion 輸出電壓:5 V 輸出電流:4.5 A 工作電源電壓:3.9 V to 17 V 最大工作溫度:+ 85 C 最小工作溫度:- 40 C 封裝 / 箱體:VQFN-24 封裝:Reel |
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