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參數(shù)資料
| 型號(hào)： | MAX1874EVKIT |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | MAX1874 Evaluation Kit |
| 中文描述： | MAX1874評(píng)估板 |
| 文件頁(yè)數(shù)： | 10/16頁(yè) |
| 文件大?。?/td> | 405K |
| 代理商： | MAX1874EVKIT |
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M
Detailed Description
The MAX1874 charges a single-cell Li+ battery from
either USB power sources or AC adapter sources. It
contains a complete two-input linear charger that controls
both battery charge current and voltage. In addition to
all charging functions, the MAX1874 includes voltage-
sensing and switchover circuitry that selects the active
input source. When both inputs are active, priority is
given to the AC adapter (DC). Charging current is regu-
lated with on-chip power MOSFETs, so no external
MOSFETs are required for a basic two-input charger.
Additional features such as input-voltage protection and
battery-load switching can be added with external
MOSFETs that are driven directly from MAX1874 outputs.
The MAX1874 also features a thermal regulation loop
that adjusts charging current so the die temperature
remains below +105
°
C. See the
Package Thermal
Limiting
section. This on-chip thermal control simplifies
PC board layout and allows the optimum charging rate
to be set without the thermal limits imposed by worst-
case battery and input voltage. When the MAX1874
thermal limit is reached, the charger does not shut
down but reduces charging current.
In addition to, and separate from, its internal die tem-
perature control, the MAX1874 can also monitor ambi-
ent or cell temperature with an external thermistor
connected to THRM. When the thermistor temperature
is out of range (greater than +50
°
C or less than 0
°
C),
charging stops until the temperature returns to normal.
See the
External Thermistor Monitor (THRM)
section.
Other features include a
CHG
output to indicate battery
full (when charge current tapers to a percentage of
fast-charge current).
DCOK
,
UOK
, and power-on (PON)
outputs indicate when valid power is present. These
outputs can drive overvoltage protection and power
selection MOSFETs (Figures 3, 4, and 5).
When charging is stopped or input power is removed,
battery leakage is typically 5μA. No input blocking
diodes are required to prevent battery drain.
With USB power connected, but without power at the
DC input, charge current can be set to either 500mA or
100mA through the USEL input. When power is taken
from the DC input, charge current is linearly set by the
voltage at DCI. The MAX1874 charge current can also
be DAC controlled with the output of a DAC connected
to DCI. See the
Charging Current
section.
Enable (EN)
The enable input, EN, switches the MAX1874 on or off.
With EN high, the MAX1874 is on and can begin charg-
ing. When EN is low,
UOK
,
DCOK
, PON, and REF remain
active. Charging stops when EN is low, but the chip
remains biased and continues to draw current from the
input supplies so power-monitoring outputs can remain
valid.
USB-to-Adapter Power Handoff
The MAX1874 can charge from either the USB input or
the DC input. It cannot charge from both sources at the
same time. The IC automatically selects the active input
and charges from that. If both power sources are
active, the adapter input (DC) takes precedence. Table
1 describes the switchover between DC and USB.
DC serves as the sense input for the adapter power
source. This input senses when DC is above 6.2V (maxi-
mum range is 18V) or below 4V. When it senses the DC
source is above 6.2V,
DCOK
goes high, indicating an
invalid DC input. See the
DC Power-OK (
DCOK
)
section.
When power is connected to DC, the MAX1874 requires
20ms to validate the input. Consequently, charging is
interrupted for 20ms until it is determined that input
power is good. Also, when DC power is removed while
valid USB power is present, charging is interrupted for
20ms before transferring to the USB source.
DC Power-OK (
DCOK
)
DCOK
is an active-low, open-drain output that goes low
when V
DC
is below 6.2V or above 3.5V.
DCOK
can be
used as a logic output, but is also designed to drive an
external MOSFET (Q2 in Figures 3, 4, and 5). This allows
the charger to protect the input from overvoltage up to
18V. Charging is disabled for inputs over 6.2V. An exter-
nal 1k
pullup resistor keeps
DCOK
high (external
MOSFET off) until it is certain the voltage is within the
Dual-Input, USB/AC Adapter, 1-Cell
Li+ Charger with OVP and Thermal Regulation
10
______________________________________________________________________________________
V
DC
> 18V OR V
USB
> 6.5V
4V < V
DC
< 6.2V AND
0 < V
USB
< 6.5V
4V < V
USB
< 6.5V AND
V
DC
< 4V OR V
DC
> 6.2V
USB powers device and supplies charging
current.
DCLV disconnected from DC source through
external MOSFET (Q2 Figures 3, 4, and 5).
V
DC
< 4V OR V
DC
>
6.2V, AND V
USB
< 4V
Exceeds operating input
range. Not allowed. See the
Absolute Maximum Ratings
section.
DCLV powers device
and supplies charging
current.
1)
2)
No charging
Table 1. USB and DC Input Selection
Note:
V
DC
takes precedence when both inputs are valid.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX1875AEEG | 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1875AEEG+ | 功能描述:電壓模式 PWM 控制器 Dual 180 Out PWM Step-Down RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| MAX1875AEEG+T | 功能描述:電壓模式 PWM 控制器 Dual 180 Out PWM Step-Down RoHS:否 制造商:Texas Instruments 輸出端數(shù)量:1 拓?fù)浣Y(jié)構(gòu):Buck 輸出電壓:34 V 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:4.5 V to 5.5 V 電源電流:600 uA 最大工作溫度:+ 125 C 最小工作溫度:- 40 C 封裝 / 箱體:WSON-8 封裝:Reel |
| MAX1875AEEG-T | 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
| MAX1875EEG | 功能描述:DC/DC 開(kāi)關(guān)控制器 RoHS:否 制造商:Texas Instruments 輸入電壓:6 V to 100 V 開(kāi)關(guān)頻率: 輸出電壓:1.215 V to 80 V 輸出電流:3.5 A 輸出端數(shù)量:1 最大工作溫度:+ 125 C 安裝風(fēng)格: 封裝 / 箱體:CPAK |
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