MAX232芯片详解：多通道RS232接口与应用

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"该资源是一份关于MAX232芯片的详细说明书，主要针对多通道RS232接口，适合单片机初学者进行DIY项目。内容涵盖了一系列与MAX232相关的芯片，如MAX220-MAX249，以及与之相关的EIA/TIA-232E标准，同时提到了低功耗和高速率的RS-232解决方案，如MAX3222E、MAX3232E等。手册还涉及了ESD保护和自动关断功能，并提供了不同封装和温度范围的芯片选项。" 在电子通信领域，MAX232是一款广泛应用的集成电路，主要用于实现TTL电平与RS-232电平之间的转换。这是因为TTL电平（通常在0V到5V之间）与RS-232标准规定的负逻辑电平（-12V到-5V和+5V到+12V）不兼容，而MAX232芯片能够解决这个问题，使得微控制器或计算机可以与RS-232兼容的设备进行通信。 MAX232的主要特点包括： 1. **内部集成电荷泵**：MAX232内置了电荷泵电路，可以生成所需的±12V电压，这些电压用于驱动RS-232的驱动器和接收器，无需额外的电源。 2. **多通道**：MAX232通常提供两个RS-232驱动器和接收器，允许同时连接两个串行通信端口。 3. **ESD保护**：该芯片具有静电放电(ESD)保护功能，有助于防止因意外接触静电而导致的芯片损坏。 4. **低功耗**：一些MAX232变种，如MAX225，设计有低功耗特性，适用于电池供电的便携式设备。 5. **高速率**：MAX3222E、MAX3232E等高级版本支持更高的数据传输速率，可达1Mbps，适用于需要快速通信的应用。 6. **AutoShutdownTM功能**：某些型号如MAX221E具备自动关断功能，能够在无数据传输时降低功耗。此外，该说明书还会详细介绍MAX232的引脚定义、电气特性、应用电路图以及如何在实际项目中正确使用MAX232的方法，对于初学者来说是非常有价值的参考资料。不同的封装选项（如塑料DIP、窄体SO和宽体SO）和工作温度范围（从0°C到+70°C或-40°C到+85°C）适应了不同环境条件下的应用需求。通过理解MAX232的工作原理和应用，用户可以更好地理解和构建基于RS-232的串行通信系统，从而在单片机开发中实现可靠的数据传输。

MAX220–MAX249

+5V

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_______________________________________________________________________________________ 7

_______________________________________________________________

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MAX223/MAX230–MAX241

8.5

6.5

4.5 5.5

TRANSMITTER OUTPUT

VOLTAGE (V

) vs. V

7.0

8.0

MAX220-04

(V)

5.0

7.5

1 TRANSMITTER

LOADED

3 TRANS-

MITTERS

LOADED

4 TRANSMITTERS

LOADED

2 TRANSMITTERS

LOADED

= +25°C

C1–C4 = 1μF

TRANSMITTER

LOADS =

3kΩ || 2500pF

7.4

6.0

0 2500

TRANSMITTER OUTPUT VOLTAGE (V

)

vs. LOAD CAPACITANCE AT

DIFFERENT DATA RATES

6.4

6.2

7.2

7.0

MAX220-05

LOAD CAPACITANCE (pF)

(V)

15001000500 2000

6.8

6.6

160kbits/sec

80kbits/sec

20kbits/sec

= +25°C

= +5V

3 TRANSMITTERS LOADED

= 3kΩ

C1–C4 = 1μF

12.0

4.0

0 2500

TRANSMITTER SLEW RATE

vs. LOAD CAPACITANCE

6.0

5.0

11.0

9.0

10.0

MAX220-06

LOAD CAPACITANCE (pF)

SLEW RATE (V/μs)

15001000500 2000

8.0

7.0

= +25°C

= +5V

LOADED, R

= 3kΩ

C1–C4 = 1μF

1 TRANSMITTER LOADED

2 TRANSMITTERS

LOADED

3 TRANSMITTERS

LOADED

4 TRANSMITTERS

LOADED

-6.0

-9.0

4.5 5.5

TRANSMITTER OUTPUT

VOLTAGE (V

) vs. V

-8.0

-8.5

-6.5

-7.0

MAX220-07

(V)

5.0

-7.5

4 TRANS-

MITTERS

LOADED

= +25°C

C1–C4 = 1μF

TRANSMITTER

LOADS =

3kΩ || 2500pF

1 TRANS-

MITTER

LOADED

2 TRANS-

MITTERS

LOADED

3 TRANS-

MITTERS

LOADED

-6.0

-7.6

0 2500

TRANSMITTER OUTPUT VOLTAGE (V

)

vs. LOAD CAPACITANCE AT

DIFFERENT DATA RATES

-7.0

-7.2

-7.4

-6.2

-6.4

MAX220-08

LOAD CAPACITANCE (pF)

(V)

15001000500 2000

-6.6

-6.8

160kbits/sec

80kbits/sec

20Kkbits/sec

= +25°C

= +5V

3 TRANSMITTERS LOADED

= 3kΩ

C1–C4 = 1μF

-10

0 5 10 15 20 25 30 35 40 45 50

TRANSMITTER OUTPUT VOLTAGE (V+, V-)

vs. LOAD CURRENT

-2

-6

-4

-8

MAX220-09

CURRENT (mA)

V+, V- (V)

V+ AND V-

EQUALLY

LOADED

V- LOADED,

NO LOAD

ON V+

= +25°C

= +5V

C1–C4 = 1μF

ALL TRANSMITTERS UNLOADED

V+ LOADED,

NO LOAD

ON V-

*SHUTDOWN POLARITY IS REVERSED

FOR NON MAX241 PARTS

V+, V- WHEN EXITING SHUTDOWN

(1μF CAPACITORS)

MAX220-13

SHDN*

V-

V+

500ms/div

MAX220–MAX249

+5V

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RS-232

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8 _______________________________________________________________________________________

Input Logic Threshold Low

ABSOLUTE MAXIMUM RATINGS—MAX225/MAX244–MAX249

ELECTRICAL CHARACTERISTICS—MAX225/MAX244–MAX249

(MAX225, V

= 5.0V ±5%; MAX244–MAX249, V

= +5.0V ±10%, external capacitors C1–C4 = 1μF; T

= T

MIN

to T

MAX

; unless oth-

erwise noted.)

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional

operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to

absolute maximum rating conditions for extended periods may affect device reliability.

Supply Voltage (V

) ...............................................-0.3V to +6V

Input Voltages

‚ ENA, ENB, ENR, ENT, ENRA,

ENRB, ENTA, ENTB..................................-0.3V to (V

+ 0.3V)

.....................................................................................±25V

OUT

(Note 5).....................................................................±15V

OUT

........................................................-0.3V to (V

+ 0.3V)

Short Circuit (one output at a time)

OUT

to GND ............................................................Continuous

OUT

to GND............................................................Continuous

Continuous Power Dissipation (T

= +70°C)

28-Pin Wide SO (derate 12.50mW/°C above +70°C) .............1W

40-Pin Plastic DIP (derate 11.11mW/°C above +70°C) ...611mW

44-Pin PLCC (derate 13.33mW/°C above +70°C) ...........1.07W

Operating Temperature Ranges

MAX225C_ _, MAX24_C_ _ ..................................0°C to +70°C

MAX225E_ _, MAX24_E_ _ ...............................-40°C to +85°C

Storage Temperature Range .............................-65°C to +160°C

Lead Temperature (soldering,10s) (Note 6) ....................+300°C

= 0V,

OUT

= ±15V

μATables 1a–1d

±0.01 ±25

Normal operation

Shutdown

Tables 1a–1d, normal operation

All transmitter outputs loaded with 3kΩ to GND

ENA, ENB, ENT, ENTA, ENTB =

CC,

OUT

= ±15V

VRS-232 Input Hysteresis

RS-232 Input Threshold Low V

V±5 ±7.5Output Voltage Swing

Output Leakage Current (Shutdown)

±0.01 ±25

Ω300 10MV

= V+ = V- = 0V, V

OUT

= ±2V (Note 7)Transmitter Output Resistance

μA

PARAMETER

±0.05 ±0.10

MIN TYP MAX UNITS

Normal operation, outputs disabled,

Tables 1a–1d, 0V ≤ V

OUT

≤ V

, ENR_ = V

TTL/CMOS Output Leakage Current

10 30Shrinking V

OUT

= V

-2 -10Sourcing V

OUT

= GND

V3.5 V

- 0.2I

OUT

= -1.0mATTL/CMOS Output Voltage High

V0.2 0.4I

OUT

= 3.2mATTL/CMOS Output Voltage Low

kΩ357

0.2 0.5 1.0V

= 5V

1.4 0.8 V

TTL/CMOS Output Short-Circuit Current

V1.8 2.4

0.8 1.3V

= 5V

RS-232 Input Resistance

V±25RS-232 Input Voltage Operating Range

mA±7 ±30V

OUT

= 0VOutput Short-Circuit Current

kbps120 64Data Rate

CONDITIONS

= 5V

μA

±0.01 ±1

Logic Pull-Up/lnput Current

10 50

Tables 1a–1d

RS-232 Input Threshold High

V2 1.4Input Logic Threshold High

RS-232 TRANSMITTERS

RS-232 RECEIVERS

Note 5: Input voltage measured with transmitter output in a high-impedance state, shutdown, or V

= 0V.

Note 6: Maximum reflow temperature for the MAX225/MAX245/MAX246/MAX247 is +225°C.

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