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参数资料
| 型号： | SP3245EEA-L |
| 厂商： | Exar Corporation |
| 文件页数： | 4/22页 |
| 文件大小： | 0K |
| 描述： | IC TXRX RS232 28SSOP |
| 标准包装： | 46 |
| 类型： | 收发器 |
| 驱动器/接收器数： | 3/5 |
| 规程： | RS232 |
| 电源电压： | 3 V ~ 5.5 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 28-SSOP（0.209"，5.30mm 宽） |
| 供应商设备封装： | 28-SSOP |
| 包装： | 管件 |
2
Exar Corporation 48720 Kato Road, Fremont CA, 94538 50-668-707 www.exar.com
SP3244E_SP3245E_00_2509
DESCRIPTION
surface mount ceramic capacitors (such as are
widely used for power-supply decoupling) are
ideal for use on the charge pump. The charge
pumps are designed to be able to function prop-
erly with a wide range of capacitor styles and val-
ues. If polarized capacitors are used the positive
and negative terminals should be connected as
shown on the Typical Operating Circuit.
Capacitance values may be increased if operat-
ing at higher Vcc or to provide greater stability as
the capacitors age.
Auto On-Line Plus Circuitry
The SP3244E/3245E devices have the advanced
Auto On-Line Plus feature that saves power by
turning off the charge pumps and driver outputs
when the transceiver inputs are idle for more
than 30 seconds.
RS-232 signals use both positive and negative
voltages of greater than ±5V magnitude. Receiv-
ers have nominal 5kΩ impedance to ground.
Even when idle, drivers will maintain output
signal voltage creating a continuous current
flow. In low power, battery operated devices this
constant current drain can decrease battery life
significantly.
Auto On-Line Plus devices may be configured
Phase 2
VSS transfer and invert: Phase two connects
the negative terminal of C2 to the VSS stor-
age capacitor and the positive terminal of C2 to
ground. This transfers the doubled and inverted
(V–) voltage onto C3. Meanwhile, capacitor
C1 charged from VCC to prepare it for its next
phase.
Phase 3
Vdd charge store and double: Phase three is
identical to the first phase. The positive ter-
minals of capacitors C and C2 are charged
from Vcc with their negative terminals initially
connected to ground. C+ is then connected
to ground and the stored charge from C– is
superimposed onto C2–. Since C2+ is still
connected to Vcc the voltage potential across
capacitor C2 is now 2 x Vcc.
Phase 4
Vdd transfer: The fourth phase connects the
negative terminal of C2 to ground and the posi-
tive terminal of C2 to the Vdd storage capacitor.
This transfers the doubled (V+) voltage onto C4.
Meanwhile, capacitor C1 charged from Vcc to
prepare it for its next phase.
The Exar charge pump generates V+ and
V– independently from Vcc. Hence in a no–load
condition V+ and V- will be symmetrical. Older
charge pump approaches generate V+ and then
use part of that stored charge to generate V-.
Because of inherent losses the magnitude of V-
will be smaller than V+ on these older designs.
Under lightly loaded conditions the intelligent
pump oscillator maximizes efficiency by running
only as needed to maintain V+ and V–. Since
interface transceivers often spend much of their
time at idle this power-efficient innovation can
greatly reduce total power consumption. This
improvement is made possible by the indepen-
dent phase sequence of the Exar charge-pump
design.
The clock rate for the charge pump typically op-
erates at greater than 70kHz allowing the pump
to run efficiently with small 0.1μF capacitors.
Efficient operation depends on rapidly charging
and discharging C and C2, therefore capacitors
should be mounted close to the IC and have low
ESR (equivalent series resistance). Inexpensive
Receiver
5k
Ω
Reciever 5k Current path to
to emulate the behavior of devices with our
earlier Auto On-line feature. Auto On-Line
Plus puts the device into a low power mode
when driver or receiver inputs are idle and
re-awakes upon detecting signal transitions.
Auto On-Line puts the device into a low power
mode when receiver inputs are left floating and
re-awakes when receivers are driven greater
than ±2.7V magnitude by incoming RS-232
signal.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| SP3245EEA-L/TR | 功能描述:RS-232接口集成电路 1Mbps +3V to +5.5V RS-232 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: |
| SP3245EER1-L | 功能描述:RS-232接口集成电路 Transceiver with Auto On-Line Plus 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: |
| SP3245EER1-L/TR | 功能描述:RS-232接口集成电路 1Mbps +3V to +5.5V RS-232 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: |
| SP3245EEY-L | 功能描述:RS-232接口集成电路 1Mbps +3V to +5.5V RS-232 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: |
| SP3245EEY-L/TR | 功能描述:RS-232接口集成电路 1Mbps +3V to +5.5V RS-232 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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