SLLS348O June   1999  – June 2015 MAX3221

PRODUCTION DATA.  

  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Pin Configuration and Functions
  6. Specifications
    1. 6.1  Absolute Maximum Ratings
    2. 6.2  ESD Ratings
    3. 6.3  Recommended Operating Conditions
    4. 6.4  Thermal Information
    5. 6.5  Electrical Characteristics - Power
    6. 6.6  Electrical Characteristics - Driver
    7. 6.7  Electrical Characteristics - Receiver
    8. 6.8  Electrical Characteristics - Status
    9. 6.9  Switching Characteristics - Driver
    10. 6.10 Switching Characteristics - Receiver
    11. 6.11 Switching Characteristics - Status
    12. 6.12 Typical Characteristics
  7. Parameter Measurement Information
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Power
      2. 8.3.2 RS232 Driver
      3. 8.3.3 RS232 Receiver
      4. 8.3.4 RS232 Status
    4. 8.4 Device Functional Modes
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
      3. 9.2.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Community Resources
    2. 12.2 Trademarks
    3. 12.3 Electrostatic Discharge Caution
    4. 12.4 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

封装选项

请参考 PDF 数据表获取器件具体的封装图。

机械数据 (封装 | 引脚)
  • DB|16
  • PW|16
散热焊盘机械数据 (封装 | 引脚)
订购信息

8 Detailed Description

8.1 Overview

The MAX3221 device is a one-driver and one-receiver RS-232 interface device. All RS-232 inputs and outputs are protected to ±15 kV using the Human Body Model. The charge pump requires only four small 0.1-μF capacitors for operation from a 3.3-V supply. The MAX3221 is capable of running at data rates up to 250 kbps, while maintaining RS-232-compliant output levels.

Automatic power-down can be disabled when FORCEON and FORCEOFF are high. With automatic power-down plus enabled, the device activates automatically when a valid signal is applied to any receiver input. The device can automatically power down the driver to save power when the RIN input is unpowered.

INVALID is high (valid data) if receiver input voltage is greater than 2.7 V or less than –2.7 V, or has been between –0.3 V and 0.3 V for less than 30 μs. INVALID is low (invalid data) if receiver input voltages are between –0.3 V and 0.3 V for more than 30 μs. Refer to Figure 7 for receiver input levels.

8.2 Functional Block Diagram

MAX3221 max3221_mini.gif

8.3 Feature Description

8.3.1 Power

The power block increases, inverts, and regulates voltage at V+ and V- pins using a charge pump that requires four external capacitors. Auto-power-down feature for driver is controlled by FORCEON and FORCEOFF inputs. Receiver is controlled by EN input. See Table 1 and Table 2

When MAX3221 is unpowered, it can be safely connected to an active remote RS232 device.

8.3.2 RS232 Driver

One driver interfaces standard logic level to RS232 levels. DIN input must be valid high or low.

8.3.3 RS232 Receiver

One receiver interfaces RS232 levels to standard logic levels. An open input will result in a high output on ROUT. RIN input includes an internal standard RS232 load. A logic high input on the EN pin will shutdown the receiver output.

8.3.4 RS232 Status

The INVALID output goes low when RIN input is unpowered for more than 30 μs. The INVALID output goes high when receiver has a valid input. The INVALID output is active when Vcc is powered irregardless of FORCEON and FORCEOFF inputs (see Table 3).

8.4 Device Functional Modes

Table 1, Table 2, and Table 3 show the behavior of the driver, receiver, and INVALID(activelow) features under all possible relevant combinations of inputs.

Table 1. Driver(1)

INPUTS OUTPUT DRIVER STATUS
DIN FORCEON FORCEOFF VALID RIN RS-232
LEVEL
DOUT
X X L X Z Powered off
L H H X H Normal operation with
automatic power down disabled
H H H X L
L L H Yes H Normal operation with
automatic power down enabled
H L H Yes L
L L H No Z Powered off by
automatic power down feature
H L H No Z
(1) H = high level, L = low level, X = irrelevant, Z = high impedance, Yes = |RIN| > 2.7 V, No = |RIN| <0.3 V

Table 2. Receiver(1)

INPUTS OUTPUT RECEIVER STATUS
RIN EN VALID RIN RS-232
LEVEL
ROUT
X H X Z Output off
L L X H Normal operation
H L X L
Open L No H
(1) H = high level, L = low level, X = irrelevant, Z = high impedance (off), Open = input disconnected or connected driver off

Table 3. INVALID(1)

INPUTS OUTPUT
RIN FORCEON FORCEOFF EN INVALID
L X X X H
H X X X H
Open X X X L
(1) H = high level, L = low level, X = irrelevant, Z = high impedance (off), Open = input disconnected or connected driver off
MAX3221 logic_lls348.gifLogic Diagram