A high-impedance state control circuit for rs-485 transceiver

A RS-485, control circuit technology, applied in electrical components, data exchange through path configuration, bus network, etc., can solve problems such as limited use scenarios, ESD voltage is difficult to reach 15,000 volts, etc., to improve ESD The effect of voltage

Active Publication Date: 2022-06-21
苏州灵天微半导体科技有限公司
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  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0003] After the output driver is enabled and turned off, the RS-485 chip must be in a high-impedance state within the voltage range specified by the agreement as -7v ~ 12v; the existing RS-485 chip usually uses CMOS output, and the negative voltage will be Causes the parasitic diode of the NMOS transistor to conduct, thereby being clamped, and a high voltage input greater than the power supply voltage will cause the parasitic diode between the drain and the N well to conduct
[0004] The current solution on the market is to connect a reverse diode to the output port to block the output port, form a connection with the parasitic diode, and block the voltage clamping; but this method makes the ESD of the two output ports of the bus A / B The voltage is difficult to reach 15,000 volts, which limits many usage scenarios

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  • A high-impedance state control circuit for rs-485 transceiver
  • A high-impedance state control circuit for rs-485 transceiver

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Embodiment Construction

[0018] In order to make the purpose, technical solution and advantages of the present invention more clear, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

[0019] When this high-impedance state control circuit is implemented, based on the common BCD process, the first PMOS transistor 5, the second PMOS transistor 7, the third PMOS transistor 8, the fourth PMOS transistor 9, the fifth PMOS transistor 10, the sixth PMOS transistor The N wells of the transistor 13 and the seventh PMOS transistor 14 are floating, blocking the clamping of the parasitic diode between the substrate and the well.

[0020] Its circuit schematic diagram, refer to Figure 1 to Figure 2 As shown, a high-impedance control circuit for an RS-485 transceiver includes an RS-485 o...

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Abstract

The invention relates to a high-impedance control circuit for an RS-485 transceiver, comprising an RS-485 output drive module and a high-impedance control module; the bus output stage of the RS-485 output drive module is electrically connected with an NPN transistor and a PNP Transistor, the high-impedance state control module is used to control when the RS-485 output drive module is enabled and closed, so that the NPN triode and the PNP triode are all cut-off; a kind of RS-485 transceiver of the present invention uses a high-impedance state control circuit , using a triode as the bus output stage, with a high-impedance control circuit composed of PMOS transistors, NMOS transistors and diodes, in the three ranges greater than 5v, 0v-5v and less than 0v, control the RS-485 transceiver when it is enabled and closed , its output presents a high-impedance state, which greatly increases the ESD voltage of the two output ports of the bus A / B, which meets the requirements of most applications.

Description

technical field [0001] The invention relates to the field of RS-485 transceivers, in particular to a high-impedance state control circuit for RS-485 transceivers. Background technique [0002] RS-485 is a standard defining the electrical characteristics of drivers and receivers in a balanced digital multipoint system, defined by the Telecommunications Industry Association and the Electronic Industries Alliance. Digital communication networks using this standard can effectively transmit signals over long distances and in environments with high electronic noise; RS-485 makes it possible to connect local networks and configure multi-drop communication links. [0003] After the output driver is enabled and turned off, the RS-485 chip must be in a high-impedance state within the voltage range specified by the agreement as -7v ~ 12v; the existing RS-485 chip usually uses CMOS output, and the negative voltage will be The parasitic diode of the NMOS tube is turned on, and thus clam...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H04B1/40H04L12/40
CPCH04B1/40H04L12/40006
Inventor 顾永兴
Owner 苏州灵天微半导体科技有限公司
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