CN104765285A - TC485H high-voltage self-voltage-stabilizing communication chip - Google Patents

Abstract

The invention belongs to the field of semiconductors and integrated circuits, and relates to an RS-485 communication low power consumption transceiver which is an RS-485 chip special for research and development to solve the wide-range supply voltage application problem, in particular to a TC485H high-voltage self-voltage-stabilizing communication chip. The TC485H chip can work normally in a wide power supply voltage range from +4.5 V to +36 V, and a voltage stabilizer is integrated inside the TC485H chip. The chip is provided with a driver and a receiver, slew rate limitation is designed for output driving, the EMI and the signal reflection effect of the chip can be reduced, and thus error-free data transmission is achieved. The highest transmission rate of the chip is larger than 500 kbps. The static power consumption of the chip is smaller than 250 microamps. The driver has a short-circuit current limitation, outputting of the driver can be shut off through a thermal-shutdown circuit, and thermal damage is prevented. The TC485H receiver output has a failure protective characteristic, and logical high level outputting can be guaranteed when the input circuit is in an open-circuit state. The TC485H chip has receiver input impedance of a 1/8 unit load, a bus can be provided with 256 transceivers at most, and accordingly a half-duplex communication network is formed.

Description

TC485H high pressure is from voltage stabilizing communication chip

Technical field

The invention belongs to semiconductor and integrated circuit fields, specifically refer to the low-power consumption transceiver for RS-485 communication, for solving the special RS-485 chip that the application of wide-range power voltage is researched and developed.

Background technology

In fields such as Industry Control, power communication, intelligent instruments, usually easy to use, easy-to-use serial communication mode is as the means of exchanges data.Electronic Industries Association (EIA) works out in nineteen eighty-three and issues RS-485 standard, and through Telecommunications Industries Association (TIA) revision after called after TIA/EIA-485-A, be referred to as RS-485 standard habitually.RS-485 standard produces for making up the shortcomings such as RS-232 communication distance is short, speed is low.RS-485 standard specify only the electrical characteristics of balance transmitter and receiver, and does not specify connector, transmission cable and application layer communication protocol.

Summary of the invention

The technical problem to be solved in the present invention is: provide a kind of low-power consumption transceiver, to solve the special RS-485 chip of the application of wide-range power voltage and research and development.

The invention provides a kind of TC485H chip for RS-485 communication, mainly comprise voltage stabilizer, transmitter and acceptor circuit part.The Pin description of TC485H chip, is shown in Table 1.

Table 1 Pin description

TC485H chip operating voltage scope is+4.5V ~+36V.There is+5V voltage regulator module its inside, and the electric current that can continue output 50mA, for peripheral hardware, makes peripheral circuit more simple, in system application, does not need to add LDO power regulator, saves space and cost.

The output of TC485H is difference output, meets RS-485 and RS-422 standard.Time unloaded, the scope of output voltage is+0.5V ~+4.5V.The output of TC485H has an enable control line , on logic high by the difference output of enable transmitter.If for low, then transmitter exports and presents high-impedance state.About the function truth table of transmitter, be shown in Table 2.

Table 2 sending function truth table

The input of TC485H receiver is Differential Input, the existence of zero potential deviation large between the wide common mode scope permission system of-4V ~+4V.Receiver has one to receive enable pin , Low level effective.The function truth table of associated receiver, is shown in Table 3.

Table 3 receiving function truth table

Table 4-table 7 lists the absolute rating of TC485H chip, DC characteristic parameter, switching characteristic parameter and ESD and latching feature parameter respectively.

Table 4 absolute rating

Table 5 DC characteristic parameter

Table 6 switching characteristic parameter

Table 7 ESD and latching feature parameter (numerical value records at being 25 DEG C)

Pin

Parameter

Symbol

Minimum value

Representative value

Maximal value

Remarks

A、B

Human Body Model (HBM)

VHBM

±8000V

-

-

-

A、B

Machinery model (MM)

VMM

±800V

-

-

-

Other

Human Body Model (HBM)

VHBM

±4000V

-

-

-

Other

Machinery model (MM)

VMM

±400V

-

-

-

All

T ALatching current when=85 DEG C

ILAT

±150mA

-

-

-

Accompanying drawing explanation

In order to be illustrated more clearly in the embodiment of the present invention or technical scheme of the prior art, be briefly described to the accompanying drawing used required in embodiment or description of the prior art below, apparently, accompanying drawing in the following describes is only embodiments of the invention, for those of ordinary skill in the art, under the prerequisite not paying creative work, other accompanying drawing can also be obtained according to these accompanying drawings.In the accompanying drawings:

Fig. 1 is TC485H chip test circuit figure of the present invention;

Fig. 2 is a typical application circuit in conjunction with TC485H chip of the present invention;

Fig. 3 is an input voltage VCC in conjunction with TC485H chip of the present invention is the application circuit of+5V;

Fig. 4 is a recommendation circuit in conjunction with TC485H chip of the present invention;

Fig. 5 is TC485H chip package schematic diagram of the present invention.

Embodiment

Clearly understand for making the object, technical solutions and advantages of the present invention, below in conjunction with embodiment of the present invention accompanying drawing, description clear, complete is further done to the technical scheme in the embodiment of the present invention, obviously, described embodiment is the one of the embodiment of the present invention, instead of whole embodiments.Based on the embodiment in the present invention, those of ordinary skill in the art, not making the every other embodiment obtained under creative work prerequisite, belong to the scope of protection of the invention.

Fig. 1 is TC485H chip test circuit figure of the present invention, comprises the test of driver DC load, transceiver timing sequence test, the load of driver timing sequence test, receiver timing sequence test, driver transmission delay, driver enable enable with forbidding sequence testing circuit figure with forbidding sequential, receiver transmission delay and receiver;

Fig. 2 is a typical application circuit in conjunction with TC485H chip of the present invention;

Fig. 3 is an input voltage VCC in conjunction with TC485H chip of the present invention is the application circuit of+5V; The input voltage range of the VCC pin of TC485H chip is+4.5V ~+36V, describes process to VCC and VOUT if the input voltage provided is+5V, Fig. 3.

Fig. 4 is a recommendation circuit in conjunction with TC485H chip of the present invention, comprises the one-point system connection diagram recommending to require in circuit theory diagrams and PCB design.Fig. 4 (a) is the recommendation circuit of the TC485H chip that uses light-coupled isolation mode to connect, and can be embedded directly within actual RS-485 application circuit.RX485, TX485 signal of serial ports connects RO, DI pin of TC485H chip by optical coupling isolation circuit, control signal TXD_EI removes the enable pin of reception of control TC485H chip equally through optical coupling isolation circuit pin.In circuit, the speed of optocoupler will affect the communication speed of RS-485 circuit, has selected LTV-816S-TA1-D3-TX chip in Fig. 4 (a).In PCB design, should be noted that following some:

A) electric capacity of TC485H input and output, must be placed on TC485H chip pin side;

B) current-limiting resistance for the protection of AB port must be placed near pin as far as possible;

C) there is complete ground connection to apply copper below TC485H chip, ensure the integrality of applying copper ground connection;

D) power supply (VCC_485) of chip and ground (AC2) are to the cabling of electrochemical capacitor and filter capacitor, carry out connecting (referring to Fig. 4 (b)) with one-point system;

E) power lead can not only be undertaken being connected to another layer by a via hole;

F) number of vias that TopLayer and BottomLayer layer covers between copper (GND) is tried one's best many.

Fig. 5 is TC485H chip package schematic diagram of the present invention, comprises SO-8, HSO-8 and MSO-8 encapsulation.

Finally it should be noted that; the foregoing is only embodiments of the invention; not thereby the scope of the claims of the present invention is limited; every utilize instructions of the present invention and accompanying drawing content to do equivalent structure or equivalent flow process conversion; or be directly or indirectly used in other relevant technical fields, be all in like manner included in scope of patent protection of the present invention.

Claims (4)

1. be applied to a TC485H chip for RS-485 communication, mainly comprise voltage stabilizer, transmitter and acceptor circuit part.

2. TC485H chip as claimed in claim 1.Chip normally can work in the wide-range power voltage of+4.5V ~+36V, and inside is integrated with voltage stabilizer.Chip has a driver and a receiver, exports driving design slew rate restriction, makes chip can reduce EMI and signal reflex effect, realizes error-free data transmission.Chip maximum transmission rate is greater than 500kbps.

3. TC485H chip as claimed in claim 1.Chip quiescent dissipation is less than 250 μ A.Driver has short-circuit current restriction, and by Thermal shutdown circuit, driver can be exported shutoff, prevents cause thermal damage.TC485H receiver exports has fail safe characteristic, when input pull-down, can guarantee that logic high exports.

4. TC485H chip as claimed in claim 1.TC485H chip has the receiver input impedance of 1/8 unit load, and making, bus can have at most 256 transceivers, forms half-duplex operation network.