会社ブログについて Supply Microchip ADC:Display ADC,Dual-Slope ADC,BCD and Binary ADC,Voltage-To-Frequency ADC

Supply Microchip ADC:Display ADC,Dual-Slope ADC,BCD and Binary ADC,Voltage-To-Frequency ADC

As a leading supplier in the electronic components sector, Shenzhen Mingjiada Electronics Co., Ltd. has specialised in distribution for many years. Adhering to the principles of ‘genuine product guarantee, rapid delivery, technical support and comprehensive service’, we provide our customers with a wide range of high-quality electronic components.

Supply Advantages

1. Reliable Quality, Genuine Products

Genuine Product Guarantee: We maintain long-term partnerships with over 500 global semiconductor brands, ensuring 100% genuine products.

Comprehensive Certification: Certified to ISO 9001 and ISO 14001, we implement strict quality control to ensure we never supply refurbished or loose new parts.

2. Extensive Stock and Extremely Fast Delivery

Extensive Stock: With dual warehouses in Shenzhen and Hong Kong, we hold over 2 million part numbers and tens of millions of items in stock, covering mainstream, niche, discontinued and hard-to-find electronic components.

Rapid Dispatch: Standard orders dispatched within 24–48 hours; urgent orders responded to within 4 hours and delivered within 1–3 days, with global delivery supported.

3. Highly Competitive Pricing and Controllable Costs

Bulk Purchasing + Global Channels: Price advantages based on purchase volume; sourcing of scarce components through global procurement; price stability.

Integrated Buy-Back Service: Optimises inventory and reduces procurement costs via an in-house buy-back system, whilst facilitating the disposal of obsolete stock.

4. Flexible Transaction Methods Suitable for a Variety of Scenarios

Small Batches/Samples: Supports split batches and loose goods transactions, suitable for R&D and pilot production.

Multi-currency/Cross-border: Supports global settlement and logistics services.

I. Display ADC

A display ADC is an integrated analogue-to-digital conversion chip with a built-in display driver. It is a derivative of the dual-slope architecture and incorporates an ADC core, decoding logic and segment drivers, enabling it to directly drive seven-segment displays and eliminating the need for an external BCD decoder chip. It serves as the core solution for portable digital meters. The Microchip TC71XX family is a typical example, including the TC7106, TC7107 and TC7129.

Principle of Operation

The underlying principle is based on dual-slope integration conversion. After quantising the sampled voltage, the chip directly generates segment drive signals for the seven-segment display internally, without the need for an MCU to perform decoding; the display can be driven to read out the measured voltage immediately upon power-up.

Key Features

1. High integration, with built-in auto-zero, polarity detection and segment code output; only an integration capacitor, reference resistor and clock components are required as peripherals;

2. 3½-digit and 4½-digit decimal display, suitable for DC voltage measurement;

3. Excellent 50Hz/60Hz power-line noise suppression; the integration window is locked to the mains cycle, providing strong common-mode interference suppression;

4. Relatively low conversion rate, typically taking several readings per second; not suitable for high-speed signal acquisition.

Typical Applications

Digital multimeters, battery voltage panel metres, temperature display units, weighing indicators.

II. Dual-Slope ADC

The dual-slope ADC is a classic architecture for integrating ADCs. Microchip’s TC7109, TC500A and TC510 all employ dual-slope or multi-slope integration schemes, making it the mainstream architecture for high-precision, low-speed measurements.

Principle of Operation

The conversion is divided into three stages: the automatic zeroing stage, the input integration stage, and the reference reverse integration stage.

1. Automatic zeroing: The integration capacitor and comparator offset voltage are automatically compensated to eliminate zero-point drift;

2. Forward integration: The input analogue voltage VIN is integrated for a fixed time T₁, and the integrator outputs a ramp voltage whose amplitude is proportional to VIN;

3. Reverse integration: The circuit switches to a precision reference voltage VREF of opposite polarity, causing the integrator to discharge in the reverse direction; the counter records the time T₂ required for the integrator output to return to zero. The count value of T₂ is proportional to the input voltage, thereby completing the analogue-to-digital conversion.

Key Features

- Outstanding immunity to power-frequency interference; the integration time is set to an integer multiple of the mains cycle, enabling the filtering out of 50/60 Hz common-mode noise;

- High accuracy and controllable temperature drift; relatively lenient requirements regarding the precision of capacitors and resistors;

- Disadvantages: Slow conversion speed; classified as a low-speed ADC; leakage current in the integrating capacitor introduces error;

Typical Applications

Precision voltmeters, weighing instruments, thermocouple temperature measurement, and bridge sensor data acquisition.

III. BCD-Output ADCs and Binary-Output ADCs

The same dual-slope ADC core can be configured for either BCD or binary code output. These two digital encoding formats are designed for different back-end systems; Microchip’s TC835 (BCD), TC850 (binary) and TC7109 all support parallel binary output.

BCD Output ADCs

BCD output ADCs provide a decimal BCD-encoded output signal, with every 4 bits representing one decimal digit. They can be directly connected to a seven-segment decoder, making them suitable for digital display systems.

- Features: The output conforms to decimal reading conventions, eliminating the need for software-based base conversion; commonly used for direct display on instruments;

- Representative model: TC835, 4½-digit BCD parallel output, with multiplexed analogue inputs;

- Limitations: The bus occupies a large number of pins and is not suitable for direct connection to an MCU for extensive data processing.

Binary Output ADC

Binary output ADCs directly output the conversion result as pure two’s complement binary (including the sign bit), facilitating reading and calculation by microcontrollers and processors.

- Features: Standard binary format, convenient for MCUs to perform mathematical operations, filtering and calibration; the TC7109 is a 12-bit binary dual-slope ADC with optional parallel or serial interfaces; the TC850 is a 15-bit + sign-bit binary multi-slope ADC;

- Limitations: When driving seven-segment displays, binary-to-BCD conversion must be performed via software or hardware;

IV. Voltage-to-Frequency ADCs

The voltage-to-frequency converter (VFC) is another indirect ADC solution. The Microchip TC9400 is a classic V/F chip; its principle involves converting the input analogue voltage into a proportional pulse frequency, with the MCU performing analogue-to-digital conversion by counting the number of pulses within a fixed gate time.

Principle of Operation

The input voltage (VIN) controls the charging and discharging of the charge pump, generating a pulse signal; the output pulse frequency (f_{OUT}) is linearly proportional to the input voltage. By counting the number of pulses within a fixed gate time, the count value corresponds to the magnitude of the input voltage.

Key Features

1. Intrinsically isolation-friendly: the pulse signal can be transmitted via optocoupler isolation, providing electrical isolation between the analogue front-end and the digital system, making it suitable for high-voltage, high-interference industrial environments;

2. Resolution can be flexibly increased by extending the gate time; the longer the gate time, the higher the resolution;

3. Simple structure and low cost per channel; the drawbacks are low conversion bandwidth and slow measurement response;

4. Capable of both V/F and F/V bidirectional conversion (TC9400).

Typical Applications

Industrial isolated signal acquisition, remote sensor transmission, pressure transmitters, and low-speed, high-precision isolated measurement.