Audio Connectivity

The Automotive Audio Bus^® (A²B^®) is an innovative technology that reduces system cost, weight, and design complexity by distributing audio and control data, together with clock and power over a single, low-cost, unshielded twisted pair cable. The AD2425W is an enhanced A²B transceiver offering an expanded feature set while retaining complete compatibility with existing AD241x devices. The AD2425W is fully configurable supporting both master and slave functionality.

The AD2425W is targeted for use in wiring intensive applications where reducing the weight or complexity of existing cable harnesses is a primary system design objective. These applications include Premium Audio Systems, Active Noise Cancellation, and In-Car Communications.

Applications

• Automotive audio communication link
• Active noise cancellation
• Microphone arrays for hands free and in car communication

The Automotive Audio Bus^® (A2B^®) is an innovative technology that reduces system cost, weight, and design complexity by distributing audio and control data, together with clock and power over a single, low-cost, unshielded twisted pair cable. The AD2421W is an enhanced A²B transceiver offering an expanded feature set while retaining complete compatibility with existing AD240x devices. The AD2421W is the lowest cost A²B transceiver supporting slave operation as an end-point only.

The AD2421W is targeted for use in microphone connectivity applications such as Beam Forming Arrays, Active Noise Cancellation, and In-Car Communications.

Applications

• Automotive audio communication link
• Active noise cancellation
• Microphone arrays for hands free and in car communication

The Automotive Audio Bus^® (A²B^®) is an innovative technology that reduces system cost, weight, and design complexity by distributing audio and control data, together with clock and power over a single, low-cost, unshielded twisted pair cable. The AD2422W is an enhanced A²B transceiver offering an expanded feature set while retaining complete compatibility with existing AD240x devices. The AD2422W is a feature and cost reduced member (supporting slave operation only) of the A²B family specifically targeting connectivity to PDM-output microphones and sensors.

The AD2422W is targeted for use in microphone connectivity applications such as Beam Forming Arrays, Active Noise Cancellation, and In-Car Communications.

Applications

• Automotive audio communication link
• Active noise cancellation
• Microphone arrays for hands free and in car communication

Lithium ion (Li-Ion) battery stacks contain a large number of individual cells that must be monitored correctly in order to enhance the battery efficiency and prolong the battery life. The 6-channel AD7280A devices in the circuit shown in Figure 1 act as the primary monitor providing accurate measurement data to the Battery Management Controller (BMC).

The AD7280A contains an internal ±3 ppm reference that allows a cell voltage measurement accuracy of ±1.6 mV. The ADC resolution is 12 bits and allows conversion of up to 48 cells within 7 μs.

The AD7280A, which resides on the high voltage side of the Battery Management System (BMS) has a daisy-chain interface, which allows up to eight AD7280A’s to be stacked together and allows for 48 Li-Ion cell voltages to be monitored. Adjacent AD7280A's in the stack can communicate directly, passing data up and down the stack without the need for isolation. The AD7280A master device on the bottom of the stack uses the SPI interface to communicate with the BMC, and it is only at this point that high voltage galvanic isolation is required in order to protect the low-voltage side of the BMS. The ADuM1201 digital isolator and the ADuM5401 isolator with integrated dc-to-dc converter combine to provide the required six channels of isolation in a compact and cost effective solution.

Figure 1. AD7280A Daisy-Chain Configuration Circuit with Isolation (Simplified Schematic: All Connections and Decoupling Not Shown)

The circuit shown in Figure 1 uses the ADF4350 synthesizer with an integrated VCO and an external PLL to minimize spurious outputs by isolating the PLL synthesizer circuitry from the VCO circuit.

The PLL circuit shown in Figure 1 uses a 13 GHz Fractional-N synthesizer, wideband active loop filter and VCO, and has a phase settling time of less than 5 μs to within 5° for a 200 MHz frequency jump.

The performance is achieved using an active loop filter with 2.4 MHz bandwidth. This wide bandwidth loop filter is achievable because of the ADF4159 phase-frequency detector (PFD) maximum frequency of 110 MHz; and the AD8065 op amp high gain-bandwidth product of 145 MHz.

The AD8065 op amp used in the active filter can operate on a 24 V supply voltage that allows control of most wideband VCOs having tuning voltages from 0 V to 18 V.

Figure 1. Block Diagram of ADF4159, AD8065 Active Loop Filter, and 11.4 GHz to 12.8 GHz VCO. (Simplified Schematic: All Connections and Decoupling Not Shown)

The AD5933 and AD5934 are high precision impedance converter system solutions that combine an on-chipprogrammable frequency generator with a 12-bit, 1 MSPS (AD5933) or 250 kSPS (AD5934) analog-to-digital converter (ADC). The tunable frequency generator allows an external complex impedance to be excited with a known frequency.

The circuit shown in Figure 1 yields accurate impedance measurements extending from the low ohm range to several hundred kΩ and also optimizes the overall accuracy of the AD5933/AD5934.

Figure 1. Optimized Signal Chain for Impedance Measurement Accuracy (Simplified Schematic, All Connections and Decoupling Not Shown)

This circuit uses the ADuC7060 or the ADuC7061 precision analog microcontroller in an accurate thermocouple temperature monitoring application. The ADuC7060/ ADuC7061 integrate dual 24-bit sigma-delta (Σ-Δ) analog-to-digital converters (ADCs), dual programmable current sources, a 14-bit digital-to-analog converter (DAC), and a 1.2 V internal reference, as well as an ARM7 core, 32 kB flash, 4 kB SRAM, and various digital peripherals such as UART, timers, serial peripheral interface (SPI), and I2C interfaces.

In the circuit, the ADuC7060/ ADuC7061 are connected to a thermocouple and a 100 Ω platinum resistance temperature detector (RTD). The RTD is used for cold junction compensation. As an extra option, the ADT7311 digital temperature sensor can be used to measure the cold junction temperature instead of the RTD.

In the source code, an ADC sampling rate of 4 Hz was chosen. When the ADC input programmable gain amplifier (PGA) is configured for a gain of 32, the noise-free code resolution of the ADuC7060/ ADuC7061 is greater than 18 bits.

The single edge nibble transmission (SENT) interface to the host is implemented by using a timer to control a digital output pin. This digital output pin is then level shifted externally to 5 V using an external NPN transistor. An EMC filter is provided on the SENT output circuit as recommended in Section 6.3.1 of the SENT protocol (SAE J2716 Standard). The data is measured as falling edge to falling edge, and the duration of each pulse is related to the number of system clock ticks. The system clock rate is determined by measuring the SYNC pulse. The SYNC pulse is transmitted at the start of every packet. More details are provided in the SENT Interface section. 

The circuit shown in Figure 1 combines the  AD5755-1 (quad channel voltage and current output DAC with dynamic power control) and the AD5700-1 HART modem, to give a completely isolated multiplexed HART^®1 analog output solution. Power can be provided either from the transformer isolated power circuit provided on the board (±13 V and +5.2 V outputs, dependent on the load current) or from external power supplies connected to terminal blocks. This circuit is suitable for use in programmable logic controllers (PLCs) and distributed control system (DCS) modules that require multiple HART-compatible 4 mA to 20 mA current outputs, along with unipolar or bipolar voltage outputs. External transient protection circuitry is also included, which is important for applications located in harsh industrial environments.

The AD5755-1 DAC is software configurable and allows the user to easily program the required output ranges and dc-to-dc converter settings used for dynamic power control. It allows access to all of the internal control registers, including the slew rate control register, which is important for applications using HART communication.

The AD5700-1 is the lowest power and smallest footprint HART-compliant IC modem in the industry. It operates as a HART frequency shift keying (FSK) half-duplex modem and integrates all of the necessary signal detection, modulating, demodulating, and signal generation functions. It contains a 0.5% precision internal oscillator, thus reducing board space requirements and cost. The AD5700-1 uses a standard UART interface.

Digital isolation is provided using the quad and dual channel ADuM3481/ADuM3210 digital isolator components based on Analog Devices, Inc., iCoupler^® technology. The use of iCoupler technology reduces the need for the additional external compo-nents often required in solutions based on optoisolators. An external transformer is used to transfer power across the isolation barrier.

The ADG759 provides multiplexing capability, enabling HART communication, across the four analog output channels. The ADG759 switches one of four differential inputs to a common differential output as determined by the 2-bit binary address lines A0 and A1. When disabled, all channels are switched off. Bypass links are included to provide the flexibility to bypass the multiplexer.

Lithium ion (Li-Ion) battery stacks contain a large number of individual cells that must be monitored correctly in order to enhance the battery efficiency, prolong the battery life, and ensure safety. The 6-channel AD7280A devices in the circuit shown in Figure 1 act as the primary monitor providing accurate voltage measurement data to the System Demonstration Platform (SDP-B) evaluation board, and the 6-channel AD8280 devices act as the secondary monitor and protection system. Both devices can operate from a single wide supply range of 8 V to 30 V and operate over the industrial temperature range of −40°C to +105°C.

The circuit shown in Figure 1 is a flexible current transmitter that converts the differential voltage output from a pressure sensor to a 4 mA-to-20 mA current output.

The circuit is optimized for a wide variety of bridge-based voltage or current driven pressure sensors, utilizes only five active devices, and has a total unadjusted error of less than 1%. The power supply voltage can range from 7 V to 36 V depending on the component and sensor driver configuration.

The input of the circuit is protected for ESD and voltages beyond the supply rail, making it ideal for industrial applications.

Figure 1. Pressure Sensor Signal Conditioning Circuit with 4 mA-to-20 mA Output (Shown in Sensor Voltage Drive Mode) (Simplified Schematic: All Connections and Decoupling Not Shown)

The circuit shown in Figure 1 is a configurable 4 mA-to-20 mA loop-powered transmitter based on an industry-leading micropower instrumentation amplifier. Total unadjusted error is less than 1%. It can be configured with a single switch as either a transmitter (Figure 1) that converts a differential input voltage into a current output, or as a receiver (Figure 5) that converts a 4 mA-to-20 mA current input to a voltage output.

Figure 1. Robust Loop Powered Configurable Transmitter Circuit with 4 mA-to-20 mA Output

The design is optimized for precision, low noise and low power industrial process control applications. The circuit can accept 0 V to 5V or 0 V to 10 V input range as a transmitter. As a receiver it can provide 0.2 V to 2.3 V or 0.2 V to 4.8 V output range compatible with ADCs using 2.5 V or 5 V references. The supply voltage can range from 12 V to 36 V as a transmitter and 7 V to 36 V as a receiver.

Since the circuit is configurable, a single hardware design can be used as a backup for both transmitter and receiver at the same time, minimizing customer inventory requirements.

The circuit shown in Figure 1 is a single-supply, low power battery operated, portable gas detector using an electrochemical sensor. The Alphasense CO-AX Carbon Monoxide sensor is used in the example.

Electrochemical sensors offer several advantages for instruments that detect or measure the concentration of many toxic gases. Most sensors are gas specific and have usable resolutions under one part per million (ppm) of gas concentration. They operate with very small amounts of current, making them well-suited for portable, battery powered instruments.

The circuit shown in Figure 1 uses the ADA4505-2, dual micro-power amplifier, which has a maximum input bias current of 2 pA at room temperature and consumes only 10 μA per amplifier. In addition, the ADR291 precision, low noise, micropower reference consumes only 12 μA and establishes the 2.5 V common-mode pseudo-ground reference voltage.

Figure 1. Low Power Gas Detector Circuit

The circuit shown in Figure 1 is a robust and flexible loop-powered current transmitter that converts the differential voltage output from a pressure sensor to a 4 mA-to-20 mA current output.

The design is optimized for a wide variety of bridge based voltage or current driven pressure sensors, utilizes only four active devices, and has a total unadjusted error of less than 1%. The loop supply voltage can range from 12 V to 36 V.

The input of the circuit is protected for ESD and voltages beyond the supply rail, making it ideal for industrial applications.

Figure 1. Robust Loop Powered Pressure Sensor Signal Conditioning Circuit with 4 mA-to-20 mA Output (Shown in Sensor Voltage Drive Mode) Simplified Schematic: All Connections and Decoupling Not Shown

The circuit in Figure 1 shows a digital-to-analog video converter paired with a low cost, low power, fully integrated reconstruction video filter with output short-to-battery (STB) protection, ideal for CVBS video transmission in harsh infotainment environments such as automotive applications. Although many video encoders (video DACs), such as the ADV7391, can drive a video load directly, it is often beneficial to use a video driver at the output of a video encoder for power savings, filtering, line driving, and overvoltage circuit protection. The main purpose of a video driver, typically configured as an active filter (also known as a reconstruction filter), is twofold: it blocks the higher frequency components (above the Nyquist frequency) that were introduced into the video signal as part of the sampling process, and it provides gain to drive the external 75 Ω cable to the video display.

Designers of infotainment and other video systems, such as rearview cameras and rear-seat entertainment systems, are likely to use this circuit to transmit video for the reasons previously stated. However, a third pressing design issue centers on the robustness. The ADA4432-1 and ADA4433-1 provide analog video designers with integrated ICs that offer crucial overvoltage protection, hardened ESD tolerance, along with excellent video specification, low power consumption, and wire diagnostic features.

The ADA4432-1 and ADA4433-1 are fully integrated, single-ended and differential video reconstruction filters, respectively. They combine overvoltage protection (STB protection) up to 18 V on the outputs, with low power consumption and a wire diagnostic capability. Wire diagnostics are provided by way of a logic output that is activated when a fault condition is present. The ADA4432-1 and ADA4433-1 feature a high-order filter with a −3 dB cutoff frequency of 10 MHz and 45 dB of rejection at 27 MHz.

The combination of STB protection and robust ESD tolerance allows the ADA4432-1 and ADA4433-1 to provide superior protection in the hostile environments.

The ADV7391, and ADA4432-1 are fully automotive qualified, which makes both products ideal for infotainment and visionbased safety systems for automotive applications. The ADV7391, ADA4432-1, and the ADA4433-1 are available in a very small LFCSP package ideal for small footprint applications.

Figure 1. Low Cost, Fully Integrated Reconstruction Filter using the ADA4432-1 (All Connections and Decoupling Not Shown)