KR930007332B1 - High speed insulated d/a converter used for bipolar ram - Google Patents

Abstract

This D/A converting device comprises a microprocessor (1), bipolar RAM (10) for transfering data between the a microprocessor and D/A converting device (100), address selector (20), timing adjusting circuit (30), channel decoder (40) for decoding channels, latch circuits for remembering data temperarily, photo couplers (60,61,62) for insulating D/A circuits electrically, D/A converter (70), switch (80) for adjusting sampling time, sampling holder (90), and amplifier for amplifing the analog output of each channel.

Description

High-speed Dye-type D / A Inverter Using Bipolar RAM

1 is a block diagram illustrating a conventional D / A converter.

2 is an overall circuit diagram illustrating the D / A converter of the present invention.

3 is a timing chart according to the present invention.

* Explanation of symbols for main parts of the drawings

1 microprocessor 10 bipolar ram

20: address selector 30: timing control circuit

40: channel decoder 50, 51, 52: latch circuit

60,61,62: Photocoupler 70: D / A Converter

80: sampling time adjustment switch 90: sampling holder

91: amplifier 100: D / A inverter

The present invention relates to a device for converting a digital output value of a microprocessor to an analog value, and particularly, a high speed saving type in which a conversion speed is high by using a bipolar RAM and the analog output terminal is electrically isolated from the analog circuit and the digital circuit as a multi-channel. It is about D / A change device

In the D / A converter of the related art, as illustrated in FIG. 1, the command value of the microprocessor 10 is connected to the plurality of D / As through the data terminal 11, the address terminal 12, and the interface 20. The digital value is input to the A converter 30, and the analog value amplified by the amplifier 40 is converted into a different analog value through the converter. Only D / A conversion is done by.

As described above, the conventional D / A converter uses a separate D / A converter for each analog output channel, so that the conversion gain is not the same, it is difficult to adjust, and occupies a large area of the PCB. The digital circuit is not electrically isolated, so there is a weak point due to external noise invading through the analog output terminal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a high speed isolated type D / A converter using a bipolar ram in which an analog circuit and a digital circuit are electrically insulated through a photocoupler while using one D / A converter for all analog output channels. It is.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

According to the present invention, a bipolar ram 10 which is a data transfer device between the microprocessor 1 and the D / A converter 100 and a address to be written by the microprocessor 1 at an address terminal of the bipolar ram 10 are provided. Address selector 20 for selecting whether to connect a channel address for D / A conversion, and a timing for continuously D / A-converting data values of the bipolar RAM 10 with a predetermined period and outputting them to a corresponding channel. A timing control circuit 30 for generating and controlling a signal, a channel decoder 40 for decoding a corresponding channel from an address of the timing control circuit 30, and a latch circuit for temporarily storing data when necessary ( 50, 51, 52, photocouplers 60, 61, and 62 that electrically insulate the analog and digital circuits, and D / A converters that convert digital values to analog values and output them to the corresponding channels. 70) with sample hole (Sample Hold) Sampling time adjustment switch 80 for adjusting the sampling time applied to the terminal, a sampling holder 90 for sampling and holding the D / A conversion value of each channel, and amplifying the analog output value of each channel. It consists of an amplifier 91.

In the high speed isolated type D / A converter of FIG. 2 configured as described above, the D / A conversion operation will be described according to the timing chart output from the timing control circuit of FIG.

The microprocessor 1 records the digital values to be D / A converted during program execution in the bipolar RAM 10 of the D / A converter 100 corresponding to the analog output channels, respectively, regardless of whether the D / A is converted or not. The microprocessor 1 writes data to the bipolar ram 10 according to the conversion time occurring in the timing control circuit 30 using the time when the microprocessor 1 does not access the bipolar ram 10. Only when it is in the "active low state" stops D / A conversion and causes the output address of the address selector 20 to be the RAM address designated by the microprocessor 10. If the data is not active, the address selector 20 outputs the channel address to be D / A converted by the input / output access signal IOA generated by the timing control circuit 30 to output the corresponding channel data in the bipolar RAM 10. Is output and latched to the latch circuit 50 when the digital data is in the " active low state " of the clock enable signal CEN. That is, when the timing control circuit 30 sets the clock enable signal CEN to the "active low state" for 1 mu sec, data at address 0 is latched to the latch circuit 50. In addition, the data transmitted through the photocoupler 60 is latched by the latch circuits 51 and 52, respectively, using signals OCK generated from the timing control circuit, and then addresses 0 to 11 (D _{0 to} D ₁₁ ). Data is converted into an analog value through the D / A converter 70 to put the S / F signal of the timing control circuit 30 in a "high state". When C _{0 ~} C ₇ are continuously input to the sample / hold terminal of the sampling holder 90 with 256 μsec period, only the sampling holder that receives the address is amplified through the amplifier 91 by sampling the analog output value. It will continue to print the output to.

Therefore, the D / A conversion period per channel is obtained by multiplying the number of channels by the D / A conversion time of one channel.

As described above, the invention uses one D / A converter for all analog output channels, so that the conversion gain is not only the same, gain adjustment is easy and accurate, and the PCB area can be greatly reduced when the number of channels is large. Since the circuit and the digital circuit are electrically insulated through the photocoupler, it has a strong effect on external noise invading through the analog output terminal.

Claims (1)

In the D / A converter, a bipolar RAM (10) which is a data transfer device between the microprocessor (1) and the D / A converter (100), and the microprocessor (1) at an address terminal of the bipolar RAM (10). The address selector 20 for selecting whether or not to connect the address to be recorded or the channel address for D / A conversion, and the data value of the bipolar RAM 10 are continuously D / A-converted with a predetermined period. A timing control circuit 30 for generating and controlling timing output to the corresponding channel, a channel decoder 40 for decoding the corresponding channel from an address of the timing control circuit 30, and temporarily storing data if necessary. The latch circuits 50, 51 and 52 stored therein, the photocouplers 60, 61 and 62 which electrically insulate the analog and digital circuits, and the operation of converting the digital values to analog values and outputting them to the corresponding channels. D / A Converter (70), a sampling time adjustment switch (80) for adjusting the sampling time applied to the sample hold terminal, a sampling holder (90) for sampling and holding the D / A conversion value of each channel, and an analog output value of each channel. High speed isolated type D / A converter using a bipolar RAM, characterized in that consisting of an amplifier (91) for amplifying.

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