参数资料
| 型号： | MAX221EAE+T |
| 厂商： | Maxim Integrated Products |
| 文件页数： | 5/8页 |
| 文件大小： | 0K |
| 描述： | IC TXRX RS-232 5V 16-SSOP |
| 产品培训模块： | Lead (SnPb) Finish for COTS Obsolescence Mitigation Program |
| 标准包装： | 2,000 |
| 类型： | 收发器 |
| 驱动器/接收器数： | 1/1 |
| 规程： | RS232 |
| 电源电压： | 4.5 V ~ 5.5 V |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 16-SSOP（0.209"，5.30mm 宽） |
| 供应商设备封装： | 16-SSOP |
| 包装： | 带卷 (TR) |
MAX221
+5V, 1A, Single RS-232 Transceiver
with AutoShutdown
_______________________________________________________________________________________
5
_______________Detailed Description
Dual Charge-Pump Voltage Converter
The MAX221’s internal power supply consists of a dual
charge pump that provides a positive output voltage
(doubling charge pump) and a negative voltage (invert-
ing charge pump) from a single +5V supply. The
charge pumps operate in continuous mode. Each
charge pump requires a flying capacitor (C1, C2) and a
reservoir capacitor (C3, C4) to generate the V+ and V-
supplies.
RS-232 Transmitter
The transmitter is an inverting level translator that con-
verts CMOS-logic levels to 5.0V EIA/TIA-232 levels. It
guarantees a 250kbps data rate with worst-case loads
of 3k
in parallel with 1000pF.
When FORCEOFF is driven to ground, or when the
AutoShutdown circuitry senses invalid voltage levels on
the receiver input, the transmitter is disabled and the out-
put is forced into a high-impedance state. The transmitter
input does not have a pull-up resistor.
RS-232 Receiver
The MAX221’s receiver converts RS-232 signals to
CMOS-logic output levels. The receiver has an inverting
three-state output and can be active or inactive. In shut-
down (FORCEOFF = low) or in AutoShutdown, the
receiver is active (Table 1). Drive EN high to place the
receiver in a high-impedance state. The receiver is high
impedance when the MAX221 is in shutdown (FORCE-
OFF = low).
The MAX221’s INVALID output is pulled low when no
valid RS-232 signal level is detected on the receiver
input. INVALID is functional in any mode (Figures 2
and 3).
AutoShutdown
The MAX221 achieves 1A supply current with Maxim’s
AutoShutdown feature, which operates when FORCEON
is low and FORCEOFF is high. When the device senses
no valid signal levels on the receiver input for 30s, the
on-board charge pump and driver are shut off, reducing
supply current to 1A. This occurs if the RS-232 cable is
disconnected or the connected peripheral transmitter is
turned off. The MAX221 turns on again when a valid
level is applied to the RS-232 receiver input. As a result,
the system saves power without changes to the existing
BIOS or operating system.
Table 1 and Figure 2c summarize the MAX221 operat-
ing modes. FORCEON and FORCEOFF override
AutoShutdown. When neither control is asserted, the
device selects between these states automatically,
based on the receiver input level. Figures 2a, 2b, and
3a depict valid and invalid RS-232 receiver levels.
Figure 3 shows the input levels and timing diagram for
AutoShutdown operation.
A device or another system with AutoShutdown con-
nected to the MAX221 may need time to wake up.
Figure 4 shows a circuit that forces the transmitter on
for 100ms, allowing enough time for the other system to
realize that the MAX221 is awake. If the other system
transmits valid RS-232 signals within that time, the RS-
232 ports on both systems remain enabled.
When shut down, the device’s charge pumps are off,
V+ is pulled to VCC, V- is pulled to ground, and the
transmitter output is high impedance. The time required
to exit shutdown is typically 100s (Figure 3b).
Software-Controlled Shutdown
For direct software control, use INVALID to indicate a
DTR or Ring Indicator signal. Connect FORCEOFF and
FORCEON together to disable AutoShutdown so the
line acts like a SHDN input.
MAX221
FORCEON
EN
12
1
ROUT
9
FORCEOFF
16
10
GND
14
TIN
11
C2-
6
C2+
5
C1-
4
C1+
2
ISHDN
RIN 8
TOUT 13
V-
7
V+
3
VCC
C4
0.1
F
0.1
F
C1
0.1
F
C2
0.1
F
CBYPASS
+5V
TO POWER-
MANAGEMENT
UNIT
5k
3k
INVALID
C3
0.1
F
15
Figure 1. Shutdown Current Test Circuit
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相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX221ECAE | 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: |
| MAX221ECAE+ | 功能描述:RS-232接口集成电路 15kV ESD-Protected 5V 1uA RS-232 Trx 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: |
| MAX221ECAE+ | 制造商:Maxim Integrated Products 功能描述:SEMICONDUCTOR ((NW)) |
| MAX221ECAE+T | 功能描述:RS-232接口集成电路 15kV ESD-Protected 5V 1uA RS-232 Trx 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: |
| MAX221ECAE-T | 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: |
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