True Analog Power and Current Monitoring 4-Quadrant Multiplication Handles Bidirectional Currents and Bipolar Voltages The LT®2940 is a power and current monitor for 4V to 80V systems that brings together the necessary circuits to accurately measure, monitor and control power. Unlike traditional power monitors that rely on data converters and multiplying registers to calculate power, the LT2940 uses a true 4-quadrant analog multiplier for continuous results with 500kHz bandwidth, ideal for use in many pulsed, chopped AC and control applications. Features 4-Quadrant Power Measurement ±5% Power Measurement Accuracy 4V to 80V High-Side Sense, 100V Max Current Mode Power and Current Outputs 500kHz Bandwidth ±3% Current Measurement Accuracy 6V to 80V Supply Range, 100V Max Inverting and Noninverting Open-Collector Comparator Outputs Available in 12-Pin 3mm × 3mm DFN and 12-Lead MSOP Packages PMON Output Current vs Sense Input Voltages n 800 n VV = VV+ – VV – VI = VI+ – VI – n n 600 VCC ≥ 11V VPMON = 0.5V n 400 –4V n n n Applications n n n n n n n Board Level Power and Current Monitoring Line Card and Server Power Monitoring Power Sense Circuit Breaker MOSFET Power Monitoring Power/Energy Meters Battery Charger Metering Power Control Loops IPMON (µA) n VV = –8V 200 –2V 0 –200 0V 2V 4V 8V –400 –200 L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. 0 VI (mV) 200 Application Ideas RS 25mΩ 2 12V + VCC I + LT2940 R3 RESET 10k LATCH I – 10k 1% V+ CMPOUT V– IMON GND PMON VIMON 6.5A/ V 12.4k 33nF GE 5BPA34KAA10B 12V, 8A PM FIELD 10k 1% CMP+ The LT2940 monitors a 12V, 8A motor, with a MOSFET serving as a circuit breaker in case the current exceeds the specified value. If tripped, a reset command at the latch input pin re-enables the motor. Motor input power is monitored at the PMON output. MUR120 10k 1% CMPOUT Motor Monitor with Circuit Breaker 100µF 25V VPMON 100W/V 100nF 4.99k FDB3632 50mΩ 10.8V TO 43.2V 34W MAX Hot Swap Controller with Power Limiting 100nF Input power is accurately limited to 34W over a 4:1 input voltage range. The LT2940 measures the power, while the LT4256-1 high voltage Hot Swap™ controller acts as the limiting element. 10Ω 10Ω 56Ω 1µF 22k VCC 100Ω SENSE GATE 100nF LT4256-1 FB TIMER 13k 2N3904 GND I+ OVP CMPOUT 6.19k 3.9k 1/8W I– VCC LT2940 GND 140k The LT2940 monitors a 30V to 80V supply rail, including its own supply current. The PMON output is scaled at 30W/V, the IMON output at 1A/V. The comparator output trips when power exceeds 120W. 10.0k CMP+ 13.7k 16k CMP+ V– V+ CMPOUT PMON LT2940 Supply Power and Current Monitor LATCH OVERPOWER (OVP) GOES HIGH WHEN SUPPLY POWER > 120W 100nF LOAD 50mΩ 1W VLOGIC I– IMON V+ 7.5k RS 0A TO 4A I+ VCC PMON 56k 2N3904 1.5k 3.9k 10nF 100Ω ON 100nF OUTPUT 100µF 150Ω 100nF SUPPLY 30V TO 80V IRF540 V– GND VPMON 30W/V IMON 20k VIMON 1A/V www.linear.com/2940 n 1-800-4-LINEAR 0610A