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LT2940 - Power and Current Monitor

LT2940 - Power and Current Monitor
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LT2940 1 2940f TYPICAL APPLICATION DESCRIPTION Power and Current Monitor The LT®2940 measures a high side current and a differential voltage, multiplies them and outputs a current proportional to instantaneous power. Bidirectional high side currents and bipolar voltage differences are correctly handled by the four-quadrant multiplier and push-pull output stage, which allows the LT2940 to indicate forward and reverse power fl ow. An integrated comparator with inverting and noninverting open-collector outputs makes the LT2940 a complete power level monitor. In addition, an output current proportional to the sensed high side current allows current monitoring. The current mode outputs make scaling, fi ltering and time integration as simple as selecting external resistors and/or capacitors. Load Monitor Alarms Above 60W FEATURES APPLICATIONS n Four-Quadrant Power Measurement n ±5% Power Measurement Accuracy n 4V to 80V High Side Sense, 100V Max n Current Mode Power and Current Outputs n Output Bandwidth Exceeds 500kHz n ±3% Current Measurement Accuracy n 6V to 80V Supply Range, 100V Max n Inverting and Noninverting Open-Collector Comparator Outputs n Available in 12-Pin DFN (3mm × 3mm) and 12-Lead MSOP Packages n Board Level Power and Current Monitoring n Line Card and Server Power Monitoring n Power Sense Circuit Breaker n Power Control Loops n Power/Energy Meters n Battery Charger Metering CMP+ PMON IMON CMPOUT CMPOUT LATCH V– V+ I+ I– 2940 TA01a VCC 110k + – 10.0k 0A TO 10A LED ON WHEN PLOAD > 60W PLOAD = VLOAD • ILOAD VLOAD 6V TO 80V ILOAD LT2940 GND 20mÙ 2W 5V 1k VIMON = ILOAD • 100 mV A VPMON = PLOAD • 20.75 mV W 24.9K 4.99k LOAD kV = kI = 20mÙ 1 12 ILOAD (A) PLOAD (W) 0 VPMON (V) 2.0 1.5 1.0 2 4 6 8 10 12 14 0.5 0 2.5 96 72 48 24 0 120 80V 30V 15V 10V 2940 TA01b LED ON LED OFF VLOAD= 6V 60W ALARM Monitor Output Level and Load Power L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.

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LT2940 3 2940f ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Supply VCC Supply Voltage Operating Range l 6 80 V ICC Supply Current IPMON = +200ìA, IIMON = +200ìA (Note 2) l 2 3.5 5 mA VCC(UVLC) Supply Undervoltage Latch Clear VCC Falling l 2.3 2.5 2.7 V ÄVCC(HYST) Supply Undervoltage Hysteresis VCC Rising l 20 75 100 mV Voltage Sense VVSEN(OR) Voltage Sense Pin Operating Range VCC 12V l –0.1 VCC – 3 V 12V < VCC < 30V l –0.1 9 V V+ Pin and V– Pin VCC 30V l –0.1 18 V VV Voltage Sense Differential Input Voltage Range (Note 5) VCC < 11V l ±(VCC – 3) V VV = VV+ – VV–...

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LT2940 4 2940f SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS VPMON Power Monitor Output Compliance Voltage VCC 12V, IPMON 0ìA l 0 VCC – 4.5 V 12V < VCC < 30V, IPMON 0ìA l 0 7.5 V VCC 30V, IPMON 0ìA l 0 12 V VCC 12V, IPMON < 0ìA l 0.5 VCC – 4.5 V 12V < VCC < 30V, IPMON < 0ìA l 0.5 7.5 V VCC 30V, IPMON < 0ìA l 0.5 12 V EPMON Power Monitor Output Total Error (Note 4) |VV • VI| 0.4V2 ±2 ±5 %FS |VV • VI| 0.4V2, 25°C < TA 85°C ±2.5 ±7 %FS |VV • VI| 0.4V2, LT2940C l ±2.5 ±9 %FS |VV • VI| 0.4V2, LT2940I l ±3.5 ±12 %FS Quadrants I and III of Shaded Region in Figure 4 l ±5 ±15 %FS KPMON Power Monitor...

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LT2940 5 2940f VI (mV) –200 400 600 200 0 0 200 –200 –400 800 2940 G01 VV = –8V –4V VV = VV+ – VV– VI = VI+ – VI– VCC 11V VPMON = 0.5V –2V 0V 2V 4V 8V IPMON (ìA) VI (mV) –200 1 2 0 –1 –100 0 100 200 –2 –3 3 2940 G02 VV = 8V VV = 8V –4V |VV • VI| 0.4V2 TA = 25°C –2V 0V 2V 4V EPMON (%FS) ONE REPRESENTATIVE UNIT TEMPERATURE (°C) –50 –4 EPMON (%FS) –3 –1 0 1 4 3 0 50 75 –2 2 –25 25 100 125 2949 G03 –8V VV 8V –200mV VI 200mV |VV • VI| 0.4V2 VCC = 12V VCC = 80V VCC = 80V VCC = 12V Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device....

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LT2940 6 2940f –4 –1500 –1000 –500 0 500 1500 –2 0 2940 G04 2 4 1000 VPMON = 0V VPMON = 0.5V IPMON (ìA) VV • VI (V2) VCC 15V VV = 40 • VI VPMON = 4V –5 –300 –200 –100 0 100 300 0 5 2940 G05 10 15 20 200 I = 200ìA OUTPUT CURRENT (ìA) OUTPUT VOLTAGE (V) TA = 25°C VCC = 6V VCC = 12V VCC = 30V I = –200ìA VCC = 6V VCC = 12V VCC = 30V 0 2.4 2.6 2.8 3.0 3.2 3.6 20 40 2940 G06 60 80 100 3.4 IPMON = 200ìA IIMON = 200ìA IPMON = 0ìA IIMON = 0ìA ICC (mA) VCC (V) IPMON = –200ìA IIMON = –200ìA –300 –300 –200 –100 0 100 300 –200 –100 0 100 2940 G07 200 300 200 VIMON = 0V VIMON = 0.5V IIMON (ìA) VI (mV) VI...

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LT2940 7 2940f TYPICAL PERFORMANCE CHARACTERISTICS PMON Input Feedthrough vs Frequency PMON Frequency Response to Voltage Sense PMON Frequency Response to Current Sense IMON Frequency Response to Current Sense Open Collector Current vs Open Collector Voltage Power Supply Rejection Ratio vs Frequency FREQUENCY (Hz) SEE TEST CIRCUITS FOR LOADING CONDITIONS –30 PMON OUTPUT SIGNAL (dBVPK) –10 100 100k 1M 10M –60 –50 1k 10k 0 –20 –40 2940 G14 VV = ±2VPK VI = 0mV, dV = 0 VI = ±200mVPK VV = 0V, dI = 0 RELATIVE TO ±1VPK RPMON = 5k ON 2VDC BIAS TA = 25°C FREQUENCY (Hz) SEE TEST CIRCUITS FOR LOADING...

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LT2940 8 2940f PIN FUNCTIONS CMPOUT (Pin 1): Inverting Open-Collector Comparator Output. When the LATCH pin’s state does not override the comparator, CMPOUT pulls low when CMP+ > 1.24V. The pull-down shuts off when CMP+ < 1.21V, or VCC < 2.5V or when the LATCH pin is low. CMPOUT may be pulled up to 36V maximum. Do not sink more than 22mA DC. CMPOUT (Pin 2): Noninverting Open-Collector Comparator Output. When the LATCH pin’s state does not override the comparator, CMPOUT pulls low when CMP+ < 1.21V, or VCC < 2.5V, or when the LATCH pin is low. The pull-down shuts off when CMP+ > 1.24V....

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