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参数资料
| 型号： | DS275S |
| 元件分类： | RS-232 |
| 英文描述： | 5V High-Speed RS-232 Transceivers with 0.1uF Capacitors |
| 中文描述： | 5V的高速RS - 232收发器与0.1uF电容 |
| 文件页数： | 3/8页 |
| 文件大小： | 126K |
| 代理商： | DS275S |
DS275
3 of 8
volts, and in many situations it can be tied directly to the +5 volt 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 9-volt 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 DS275 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
=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
upon its voltage and the impedance that TX
OUT
sees.
=
about 3 mA, depending
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 DS275 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
feet. As a prime example, the DS275 will not meet the RS-232 requirement that the signal levels be at
least
±
5 volts minimum when terminated by a 3 k
=
load and V
DRV
= +5 volts. Typically a voltage of 4
volts will be present at TX
OUT
when spacing. However, since most RS-232 receivers will correctly
interpret any voltage over 2 volts as a space, there will be no problem transmitting data.
APPLICATIONS INFORMATION
The DS275 is designed as a low-cost, RS-232-E interface expressly tailored for the unique requirements
of battery-operated handheld products. As shown in the electrical specifications, the DS275 draws
exceptionally low operating and static current. During normal operation when data from the handheld
system is sent from the TX
OUT
output, the DS275 only draws significant V
DRV
current when TX
OUT
transitions positively (spacing). This current flows primarily into the RS-232 receiver’s 3-7 k
=
load at the
other end of the attaching cable. When TX
OUT
is marking (a negative data signal), the V
DRV
current falls
dramatically since the negative voltage is provided by the transmit signal from the other end of the cable.
This represents a large reduction in overall operating current, since typical RS-232 interface chips use
charge-pump circuits to establish both positive and negative levels at the transmit driver output.
To obtain the lowest power consumption from the DS275, observe the following guidelines. First, to
minimize V
DRV
current when connected to an RS-232 port, always maintain TX
IN
at a logic 1 when data is
not being transmitted (idle state). This will force TX
OUT
into the marking state, minimizing V
DRV
current.
Second, V
DRV
current will drop to less than 100 nA when V
CC
is grounded. Therefore, if V
DRV
is tied
directly to the system battery, the logic +5 volts can be turned off to achieve the lowest possible power
state.
FULL-DUPLEX OPERATION
The DS275 is intended primarily for half-duplex operation; that is, RX
IN
should remain idle in the
marking state when transmitting data out TX
OUT
and visa versa. However, the part can be operated full-
duplex with most RS-232-E serial ports since signals swinging between 0 and +5V will usually be
correctly interpreted by an RS-232-E receiver device. The 5-volt swing occurs when TX
OUT
attempts to
swing negative while RX
IN
is at a positive voltage, which turns on an internal weak pulldown to ground
for the TX
OUT
driver’s negative reference. So, transmit mark signals at TX
OUT
may have voltage jumps
from some negative value (corresponding to RX
IN
marking) to approximately ground. One possible
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相关代理商/技术参数 |
参数描述 |
|---|---|
| DS275S/T&R | 制造商:Maxim Integrated Products 功能描述:IC TXRX LINE-PWR RS232 IND 8SOIC |
| DS275S/T&R | 功能描述:RS-232接口集成电路 RoHS:否 制造商:Exar 数据速率:52 Mbps 工作电源电压:5 V 电源电流:300 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:LQFP-100 封装: |
| DS275S+ | 功能描述:RS-232接口集成电路 Line-Powered RS-232 Transceiver Chip RoHS:否 制造商:Exar 数据速率:52 Mbps 工作电源电压:5 V 电源电流:300 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:LQFP-100 封装: |
| DS275S+T&R | 制造商:Maxim Integrated Products 功能描述:IC TXRX LINE-PWR RS232 8-SOIC |
| DS275S+T&R | 功能描述:RS-232接口集成电路 Line-Powered RS-232 Transceiver Chip RoHS:否 制造商:Exar 数据速率:52 Mbps 工作电源电压:5 V 电源电流:300 mA 工作温度范围:- 40 C to + 85 C 安装风格:SMD/SMT 封装 / 箱体:LQFP-100 封装: |
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