Power monitor IC promises true readings

Device replaces previous circuits that use costly current sense amplifiers with a separate ADC, a hot-swap controller with an ADC, or an ADC with a floating ground.

The LTC4151 from Linear Technology is a high-side power monitor that measures current and input voltages from 7 to 80V.

The LTC4151 has an internal 12bit ADC to continuously measure both high side current and input voltage to give a true power reading.

The LTC4151 replaces previous circuits that use costly current sense amplifiers with a separate ADC, a hot-swap controller with an ADC, or an ADC with a floating ground.

These older implementations are in many cases limited by the ADC's input voltage range (typically 5 or 10V), are much more expensive, require more board space, and are not reliable.

The LTC4151's simple, single-chip solution is ideal for 48V telecomms equipment, advanced mezzanine cards (AMC), and blade servers used for measuring input power over a wide input range.

The device is also appropriate for power monitoring in industrial applications running at 12 or 24V.

The maximum total unadjusted error for the high-side current and voltage measurements is +/-1.25% over the -40 to +85C industrial temperature range.

A two-wire I2C-compatible interface reports the LTC4151's input power data, as well as a third low voltage input, which can be used to measure a voltage from a thermistor or a fuse.

Data can be reported continuously or in a no-latency single snapshot mode, for applications that only need to measure input power occasionally.

The LTC4151 features a dedicated shutdown pin to reduce power dissipation by 10x, while its counterpart, the LTC4151-1, features split I2C data pins with an inverted output to drive optoisolators.

The LTC4151 and LTC4151-1 are both available today in tiny MSOP-10 and 3 x 3mm DFN-10 packages, with pricing beginning at US $2.60 in 1000-piece quantities.

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