POWER AND LINEAR IC SOLUTIONS

Current-Sense Amplifier Offers High Accuracy Over Wide Temperature Range

As electronic systems replace and augment mechanical systems in automobiles, there is a growing need for circuits that can measure current accurately for system health and control applications. The LT6107 from Linear Technology is a high accuracy, high-side current-sense amplifier designed for use in the harsh automotive environment.

While ICs experience accelerated ageing at high temperatures, the LT6107 has been characterised for operation over a lifetime of 1000 hours at +150°C, making it attractive for under-the-hood applications. It also has full specification to operate at voltages of up to 36V at both the supply and its inputs.



The device measures the current that flows through a small shunt resistor; the designer selects this to optimise the trade-off between voltage drop (and therefore power dissipation) and current-sense resolution. Two other resistors set the gain.

Offset voltage for the LT6107 is guaranteed to be less than 400µV over the full operating temperature range and the device can accept a full-scale differential input of 500mV, resulting in a minimum dynamic range of 1250:1. Input bias current is no more than 130nA, also guaranteed over the full operating temperature range, to all intents and purposes eliminating bias current as a source of error.

The combination of its high-precision specifications and the LT6107’s flexible architecture allows an automotive system designer to achieve 1% overall accuracy or better.

By choosing a value for the sense resistor of 0.02Ω, the LT6107 can accurately measure 5A at a gain of 10. With a typical input-offset voltage of 150µV, the uncertainty caused by input offset (the dominant error source) is typically just 7.5mA, or 0.15%.

With the device’s V+ pin connected to the supply side of the shunt resistor, the supply current drawn by the LT6107 is not included in the monitored current. The designer can change this and include the current in the measured figure simply by moving the V+ connection to the load side of the shunt resistor.

The LT6107 consumes a maximum of 135µA over the temperature and voltage range, making it useful for battery operated applications. It is available in a small five-lead SOT-23 package and is pin-compatible with the company’s popular LT610x range of parts.

Features

• High-temperature high-side current amplifier
• Low profile ThinSOT-23 package
• Fully tested at -55°C, +25°C and +150°C
• Gain configured with two resistors
• Low offset voltage: 250μV maximum
• Output current: 1mA maximum
• Supply range: 2.7V to 36V, 44V absolute maximum
• Low input bias current: 40nA maximum
• PSRR: 106dB minimum
• Low supply current: typically 65μA at 12V

Applications

• Current shunt measurement
• Battery monitoring
• Power management
• Motor control
• Lamp monitoring
• Overcurrent and fault detection

For further information, to register your interest in a Free Demo Board*, or to obtain a copy of the latest Altera/LTC Development Tools Brochure, please click here

* Free demo boards are limited to current or potential Arrow customers with valid opportunities and are at the discretion of local Arrow representatives.