Electronic Design


ADC Converter Chip Features Built-In USB Interface
Asahi Kaei Microsystems Semiconductor Inc.
(888) 256-7364; fax (408) 436-7591; www.akm.com

The AK5371 two-channel analog-to-digital converter (ADC) is targeted to manufacturers wishing to create USB microphones and headsets for PC and consumer telephony and voice applications. This ADC offers a built-in USB interface.

With the AK5371, the microphone can identify itself to the system and digitize the signal at the microphone rather than at the sound card. This configuration improves audio performance and enables software manufacturers to tune their programs to the capture hardware to ensure the best results. The device includes an EEPROM interface that enables OEMs to customize the Vendor Name and Product ID that appears during the USB enumeration process. There is also an integrated bias circuit that improves the analog performance of microphones. The AK5371 features a Suspend Mode that reduces current to less than 1 µA when activated. This device is fully USB-compliant, guaranteeing OEMs the best compatibility. The chip incorporates nearly all of the functions required for USB microphones, significantly reducing component count and physical space.

Available now, the AK5371 is packaged in a 48-pin LQFP. In 1000-unit quantities, this ADC costs $6.72 each.

Low-Power Eight-Channel ADCs Provide Software-Configurable Inputs
Linear Technology Corp.
(800) 4-LINEAR; fax (408) 434-6441; www.linear-tech.com

The LTC1852 and LTC1853 10-bit and 12-bit eight-channel analog-to-digital converters (ADCs) draw just 3 mW from a 3-V supply. These devices sample at up to 400 ksamples/s with a 5-V supply. Also, they feature a highly flexible multiplexer. The ADCs can be configured for different combinations of single-ended or differential inputs, two gain ranges, and unipolar or bipolar operation.

The ADCs can scan through all channels, or they can be programmed with a sequence of up to 16 unique input configurations and channels for automatic scanning. According to the company, the flexibility and ease of use of these products makes them ideal for multiplexed data acquisition and industrial process-control applications. The LTC1852 and LTC1853 offer dc accuracy of one LSB INL and DNL for precision applications. They consume 10 mW when operated at 5 V. NAP and SLEEP shutdown modes further reduce power consumption for power-sensitive applications. An internal 2.5-V reference saves board space. The ADCs are pin-compatible and come in a 48-pin TSSOP package for the commercial- and industrial-temperature ranges. While the LTC1852 begins at $5.95, the LTC1853 begins at $6.95. All pricing is for 1000-unit quantities.

Touchscreen Data Converters Offer Accuracy For Handheld Devices
Analog Devices Inc.
(800) ANALOG-D; fax (781) 937-1021; www.analog.com

The AD7843 and AD7873 are resistive touchscreen digitizers optimized for battery-powered equipment. According to the company, these devices are suited for all touchscreen devices, including PDAs, handheld devices, monitors, point-of-sale terminals, and pagers.

The pin-compatible converters integrate a 12-bit successive-approximation register (SAR) analog-to-digital converter (ADC) architecture. Low on-resistance switches are incorporated for driving touchscreens. The AD7873 features added functionality that includes an on-chip temperature sensor from −40°C to 85°C. Additional features include direct battery and touch-pressure measurement and an onboard reference of 2.5 V. The AD7873 and AD7843 consume less than 1.4 mW (maximum) with the internal reference off while operating at a throughput rate greater than 125 ksamples/s.

These devices feature improved electrostatic discharge (ESD) immunity. 10- to 12-KeV ESD protection is featured on analog inputs to prevent damage to critical internal system components. Both low-power digitizers operate from a single 2.2- to 5.25-V power supply. To extend battery life, the internal reference of the AD7873 can be shut down when not in use. Both devices include a power-down mode that significantly reduces the current consumption to less than 1 µA.

Both devices are offered in a 16-lead QSOP and a 16-lead TSSOP package. While the AD7843 costs $2.15, the AD7873 costs $2.30. All pricing is for 1000-unit quantities.

16-Bit ADC Requires Only 85 mW At 500 ksamples/s
Texas Instruments Inc.
(800) 477-8924, ext. 4500; www.ti.com

The ADS8322 is a 16-bit analog-to-digital converter (ADC) targeted at high-precision applications. It is suited for use in optical networking equipment, medical equipment (CT scanners, X-ray scanners), sonar equipment, high-speed data acquisition, and spectrum analyzers. This device consumes only 85 mW of at a full speed of 500 ksamples/s.

This 16-bit capacitor-based successive approximation register (SAR) ADC has inherent sample-and-hold. An internal 2.5-V reference is incorporated. The ADS8322 offers a full 16-bit, high-speed parallel interface. An 8-bit option is available where data is read using two read cycles and eight pins. The ADC boasts unipolar input as well as a 0- to 5-V input range. It is guaranteed over the industrial-temperature range of −40°C to 85°C. A bipolar version, the ADS8323, is scheduled for release later this year.

The ADS8322 is available in a TQFP-32 package. In 1000-unit quantities, pricing for the ADC starts at $7.50.

32-Channel ADC Module Includes Built-In Signal Conditioning
Pentek Inc.
(201) 818-5900; fax (201) 818-5904; www.pentek.com

The Model 4277 Modular Interface Extension (MIX) module features 32 individual sigma-delta (Σ-Δ) analog-to-digital converters (ADCs) with 16-bit resolution. The module features sampling rates of 200 kHz as well as built-in signal conditioning. According to the company, this commercial-off-the-shelf (COTS) ADC mo-dule offers a 200% performance improvement over existing solutions.

Each of the 32 inputs is buffered by an amplifier stage with either single-ended or differential inputs. Following the amplifier are 32 Σ-Δ ADCs, one for each input signal. The ADCs feature built-in low-pass digital filters to perform anti-aliasing. This configuration eliminates the need for separate, external low-pass filters in most applications. Signal-to-noise performance is typically 90 dB. Peak spurious components are typically better than 90 dB below full scale for signal bandwidth up to 90 kHz.

Software development tools are available for a variety of operating platforms, including Sun SPARC stations running SunOS or Solaris, PCs running Windows 95/NT, Digital Alphas running D-UNIX, and Hewlett-Packard workstations running HP-UX.

Available now, pricing for the Model 4277 starts at $5995.

650-kHz Rail-To-Rail Op Amp Operates Down To 2.7 V
Micrel Inc.
(408) 944-0800; fax (408) 944-0970; www.micrel.com

The MIC861 650-kHz rail-to-rail op amp draws only 4.6 µA. It provides a −3 dB bandwidth of 650 kHz. A 400-kHz gain-bandwidth is also featured.

The MIC861 operates from a 5-V supply down to 2.7 V. It comes in the company's Teeny SC70-5 packaging. This package is approximately one-half the size of SOT23-5 packaging. The op amp is unity gain stable. The input offset voltage is 2 mV. It features a large signal voltage gain of 83 dB. While the PSRR is 85 dB, the CMRR is 80 dB. The MIC861 features a 0.12 V/µs slew rate. According to the company, suitable applications for the MIC861 are portable equipment, cellular phone, and MP3 player applications. In 1000-unit quantities, the op amp costs $1.02 each.

Applications Guide Features EMI, RFI, And ESD Solutions
AVX Corp.
(843) 946-0414; fax (843) 946-0626; www.avxcorp.com

The "Applications Guide to EMI/RFI/ESD Solutions" booklet offers valuable information on EMI, RFI, and ESD standards and solutions for design engineers. The guide includes a comprehensive checklist of products available from the company to provide EMI reduction and ESD suppression. A selector guide flow chart assists design engineers in specifying the correct device. A recent "snapshot" of international EMI/ESD regulatory standards is also included.

This booklet provides design engineers with the top 10 pc-board EMI rules utilized in designing low-noise boards. It also explains actual proven circuit solutions for EMI reduction and ESD suppression. The guide provides theory as well as step-by-step instructions on how to solve various pc-board problems. A free copy of the "Applications Guide to EMI/RFI ESD Solutions" can be ordered by contacting the company's literature department.

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