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參數(shù)資料
| 型號： | DS276 |
| 英文描述： | Low Power Transceiver Chip |
| 中文描述： | 低功耗、收發(fā)器芯片 |
| 文件頁數(shù)： | 2/11頁 |
| 文件大小： | 132K |
| 代理商： | DS276 |
DS276
2 of 11
OPERATION
Designed for the unique requirements of battery-backed systems, the DS276 provides a low-power full-or
half-duplex interface to an RS-232 serial port. Typically, a designer must use an RS-232 device which
uses system power during both negative and positive transitions of the transmit signal to the RS-232 port.
If the connector to the RS-232 port is left connected for an appreciable time after the communication
session has ended, power will statically flow into that port, draining the battery capacity. The DS276
eliminates this static current drain by stealing current from the receive line (RX
IN
) of the RS-232 port
when that line is at a negative level (marking). Since most asynchronous communication over an RS-232
connection typically remains in a marking state when data is not being sent, the DS276 will not consume
system power in this condition. Sys-tem power would only be used when positive-going transitions are
needed on the transmit RS-232 output (TX
OUT
) when data is sent. However, since synchronous
communication sessions typically exhibit a very low duty-cycle, overall system power consumption
remains low.
RECEIVER SECTION
The RX
IN
pin is the receive input for an RS-232 signal whose levels can range from
±
3 to
±
15 volts. A
negative data signal is called a mark while a positive data signal is called a space. These signals are
inverted and then level-shifted to normal +3 or +5 volt CMOS/TTL logic levels. The logic output
associated with RX
IN
is RX
OUT
which swings from V
CC
to ground. Therefore, a mark on RX
IN
produces a
logic 1 at RX
OUT
; a space produces a logic 0.
The input threshold of RX
IN
is typically around 1.8 volts with 500 millivolts of hysteresis to improve
noise rejection. Therefore, an input positive-going signal must exceed 1.8 volts to cause RX
OUT
to switch
states. A negative-going signal must now be lower than 1.3 volts (typically) to cause RX
OUT
to switch
again. An open on RX
IN
is interpreted as a mark, producing a logic 1 at RX
OUT
.
TRANSMITTER SECTION
TX
IN
is the CMOS/TTL-compatible input for data from the user system. A logic 1 at TX
IN
produces a
mark (negative data signal) at TX
OUT
while a logic 0 produces a space (positive data signal). As
mentioned earlier, the transmitter section employs a unique driver design that can use the RX
IN
line for
swinging to negative levels. RX
IN
can be connected via external circuitry to V
DRV-
to allow stored charge
to supply this voltage during marking (or idle) states. When TX
OUT
needs to transition to a positive level,
it uses the V
DRV+
power pin for this level. V
DRV+
can be a voltage supply between 3 to 12 volts, and in
many situations it can be tied directly to the V
CC
supply. It is important to note that V
DRV+
must be greater
than or equal to V
CC
at all times.
The voltage range on V
DRV+
permits the use of a 9V battery in order to provide a higher voltage level
when TX
OUT
is in a space state. When V
CC
is shut off to the DS276 and V
DRV+
is still powered (as might
happen in a battery-backed condition), only a small leakage current (about 50-100 nA) will be drawn. If
TX
OUT
is loaded during such a condition, V
DRV+
will draw current only if RX
IN
is not in a negative state.
During normal operation (V
CC
= 3 or 5 volts), V
DRV+
will draw less than 2 uA when TX
OUT
is marking. Of
course, when TX
OUT
is spacing, V
DRV+
will draw substantially more current
about 3 mA, depending
upon its voltage and the impedance that TX
OUT
sees. The TX
OUT
output is slew rate-limited to less than 30
volts/us in accordance with RS-232 specifications. In the event TX
OUT
should be inadvertently shorted to
ground, internal current-limiting circuitry prevents damage, even if continuously shorted.
RS-232 COMPATIBILITY
The intent of the DS276 is not so much to meet all the requirements of the RS-232 specification as to
offer a low-power solution that will work with most RS-232 ports with a connector length of less than 10
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| DS276+ | 功能描述:RS-232接口集成電路 RoHS:否 制造商:Exar 數(shù)據(jù)速率:52 Mbps 工作電源電壓:5 V 電源電流:300 mA 工作溫度范圍:- 40 C to + 85 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:LQFP-100 封裝: |
| DS2760 | 制造商:DALLAS 制造商全稱:Dallas Semiconductor 功能描述:High Precision Li-Ion Battery Monitor |
| DS2760AE | 功能描述:IC BATT MON LI-ION HP 16-TSSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 電池管理 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 功能:充電管理 電池化學(xué):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(yīng)商設(shè)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 |
| DS2760AE/T&R | 制造商:Maxim Integrated Products 功能描述:IC BATT MON LI-ION HP 16-TSSOP |
| DS2760AE/T&R | 功能描述:IC BATT MON LI-ION HP 16-TSSOP RoHS:否 類別:集成電路 (IC) >> PMIC - 電池管理 系列:- 標(biāo)準(zhǔn)包裝:1 系列:- 功能:充電管理 電池化學(xué):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(yīng)商設(shè)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 |
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