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Avago markets 1G? input impedance optical isolation amplifiers

Posted: 12 Jul 2012 ?? ?Print Version ?Bookmark and Share

Keywords:Optical Isolation Amplifiers? sigma-delta modulation? motor drives? renewable energy systems.?

Avago Technologies has announced a new family of optically-isolated voltage sensors, which it says is the industry's first series of optical isolation amplifiers based on sigma-delta modulation specifically optimized for voltage sensing.

The ACPL-C87B, C87A and C870 provide designers with a 2V input range and high 1G? input impedance. The new sensors are targeted for applications that include sensing voltages in electronic power conversion systems commonly found in motor drives, switching power supplies and renewable energy systems as well as sensor interfaces such as NTC thermistor isolation in IGBT modules.

The ACPL-C87A (1% gain tolerance) and ACPL-C870 (3% gain tolerance) are recommended for general applications. On the other hand, the ACPL-C87B (0.5% gain tolerance) can be used in high-precision applications such as renewable energy inverters where it is important to accurately track the fluctuating (due to changing sun conditions) DC bus voltage, and for high-performance servo and motor drives.

The voltage sensors features a 1V/V unity gain with low gain drift of -35ppm/?C. Nonlinearity is kept to within 0.1% max. The voltage sensors include an active high shutdown pin that reduces the IDD1 current to only 15?A during standby, which makes the sensors well-suited for battery-powered and other power-sensitive applications.

The high 1G? input impedance simplifies the resistor network design by allowing higher-value resistors to be used to scale the voltage. As a result, it reduces loading power losses thus achieving better system efficiency.

Avago's optical isolation amplifiers use advanced Sigma-Delta modulation technology and chopper-stabilized amplifiers to provide accurate, safe and reliable current and voltage sensing. Differential outputs on the new devices provide unequalled isolation-mode noise rejection, low offsets, high gain accuracy and stability, and wide signal bandwidth of 100kHz.

The built-in reinforced safety insulation and high CMR (common mode rejection) performance prevents erroneous voltage measurements and ensures reliable operation in noisy environments. The optically-isolated voltage sensors have a 15kV/?s common-mode transient immunity.

Safety approvals include CSA and IEC/EN/DIN EN60747-5-5 with a VIORM of 1230Vpeak. The sensors are UL recognized with 5000Vrms for 1 min per UL1577. The ACPL-C87x voltage sensors are housed in stretched 8-lead SO-8 plastic packages with 8mm creepage and clearance that meet worldwide regulatory safety standards. The sensors also have a wide operating temperature range of -40 to 105C.

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