Unique Analog Multiplier Continuously Monitors
Instantaneous Power and Simplifies Design of
Power Control Loops
Mitchell Lee and Thomas DiGiacomo As energy consumption in electronics is increasingly scrutinized, the ability to accurately
monitor and control power becomes an important part of any system design. To measure
instantaneous power, one must simultaneously measure current and voltage and multiply
the results. While traditional analog multiplier ICs can perform continuous multiplication,
they typically lack the operating range and input sensitivity required for power monitoring
and control. The high price of the multiplier itself and the necessary additional signal
conditioning circuits make such a solution costly both in dollars and in board area.
Digital solutions, on the other hand,
can provide sensitivity and dynamic
range, but lack the ability to continuously monitor power. For instance, the
LTC4151 combines a 7V to 80V operating
voltage range, a current sense amplifier,
a MUX, and an I2C interface with a 12-bit
ADC to measure current and voltage.
Multiplication is performed in a host
processor. This makes for an accurate
power monitoring solution, but the 7.5Hz
conversion rate of the ADC limits its utility in closed loop applications, where it
is unable to respond to rapid changes.
The LT2940 power monitor solves the …
