LT2940 Power and Current Monitor FEATURES n n n n n n n n n DESCRIPTION Four-Quadrant Power Measurement ±5% Power Measurement Accuracy 4V to 80V High Side Sense, 100V Max Current Mode Power and Current Outputs Output Bandwidth Exceeds 500kHz ±3% Current Measurement Accuracy 6V to 80V Supply Range, 100V Max Inverting and Noninverting Open-Collector Comparator Outputs Available in 12-Pin DFN (3mm × 3mm) and 12-Lead MSOP Packages 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 flow. 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, filtering and time integration as simple as selecting external resistors and/or capacitors. APPLICATIONS n n n n n n Board Level Power and Current Monitoring Line Card and Server Power Monitoring Power Sense Circuit Breaker Power Control Loops Power/Energy Meters Battery Charger Metering 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. TYPICAL APPLICATION Load Monitor Alarms Above 60W ILOAD Monitor Output Level and Load Power 2.5 0A TO 10A 6V TO 80V 20mΩ 2W VCC 110k CMPOUT LED ON WHEN PLOAD > 60W I– LATCH V+ LT2940 CMPOUT 1.5 72 LED OFF 48 1.0 60W ALARM 0.5 V– GND VLOAD = 6V LED ON 10.0k CMP+ PMON 96 10V PLOAD (W) 1k I+ 15V 2.0 VPMON (V) 5V 30V + VLOAD – LOAD 120 80V 24 IMON VPMON = PLOAD • 20.75 mV W VIMON = ILOAD • 100 24.9K mV A 4.99k 0 0 0 2 4 6 8 ILOAD (A) 10 12 14 2940 TA01b kV = 1 12 kI = 20mΩ PLOAD = VLOAD • ILOAD 2940 TA01a 2940f 1 LT2940 ABSOLUTE MAXIMUM RATINGS (Notes 1, 2) VCC , I+, I– , LATCH .................................... –0.3V to 100V V+, V– , CMP+ ............................................. –0.3V to 36V Voltage Sense (V+ – V– ) .........................................±36V Current Sense (I+ – I– ) ............................................±36V PMON, IMON (Note 3) ...... –0.3V to VCC + 1V, Up to 16V CMPOUT, CMPOUT .................................... –0.3V to 36V CMPOUT, CMPOUT DC Output Current ..................22mA Operating Temperature Range LT2940C................................................... 0°C to 70°C LT2940I ................................................–40°C to 85°C Storage Temperature Range...................–65°C to 150°C Lead Temperature (Soldering, 10 sec) MSOP Package ................................................. 300°C PIN CONFIGURATION TOP VIEW CMPOUT TOP VIEW 12 VCC 1 CMPOUT 2 11 CMP+ 3 10 I – PMON 4 9 LATCH IMON 5 8 V+ GND 6 7 V– 13 CMPOUT CMPOUT CMP+ PMON IMON GND I+ 1 2 3 4 5 6 12 11 10 9 8 7 VCC I+ I– LATCH V+ V– MS PACKAGE 12-LEAD PLASTIC MSOP DD PACKAGE 12-LEAD (3mm s 3mm) PLASTIC DFN TJMAX = 125°C, θJA = 135°C/W TJMAX = 125°C, θJA = 43°C/W EXPOSED PAD (PIN 13) PCB GND CONNECTION OPTIONAL ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE LT2940CDD#PBF LT2940CDD#TRPBF LDPP 12-Lead Plastic DFN 0°C to 70°C LT2940IDD#PBF LT2940IDD#TRPBF LDPP 12-Lead Plastic DFN –40°C to 85°C LT2940CMS#PBF LT2940CMS#TRPBF 2940 12-Lead Plastic MSOP 0°C to 70°C LT2940IMS#PBF LT2940IMS#TRPBF 2940 12-Lead Plastic MSOP –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ 2940f 2 LT2940 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. All specifications apply at 6V ≤ VCC ≤ 80V, unless otherwise specified. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS Supply l 6 IPMON = +200μA, IIMON = +200μA (Note 2) l 2 Supply Undervoltage Latch Clear VCC Falling l Supply Undervoltage Hysteresis VCC Rising Voltage Sense Pin Operating Range VCC Supply Voltage Operating Range 80 V ICC Supply Current 3.5 5 mA VCC(UVLC) 2.3 2.5 2.7 V ΔVCC(HYST) l 20 75 100 mV VCC ≤ 12V l –0.1 VCC – 3 V 12V < VCC < 30V l –0.1 9 V VCC ≥ 30V l –0.1 18 V Voltage Sense Differential Input Voltage Range VCC < 11V (Note 5) l ±(VCC – 3) V Voltage Sense VVSEN(OR) V+ Pin and V – Pin VV VV = V V+ – V V – VCC ≥ 11V l ±8 V VV(CL) Voltage Sense Differential Clipping Limit (Note 5) VCC ≥ 12V l ±9 V IVSEN Voltage Sense Input Bias Current V+ Pin and V – Pin l –300 ΔIVSEN Voltage Sense Input Offset Current ΔIVSEN = IV+ – IV – V V+ = V V – l –100 100 nA ±50 ±150 nA 80 V Current Sense VISEN(OR) Current Sense Pin Operating Range I+ Pin and I – Pin l 4 VI Current Sense Differential Input Voltage Range (Note 6) VI = V I + – V I – l ±200 mV VI(CL) Current Sense Differential Clipping Limit (Note 6) l ±225 mV IISEN Current Sense Input Bias Current I+ Pin and I – Pin l 75 ΔIISEN Current Sense Input Offset Current ΔIISEN = II+ – I I – V I+ = V I – l 100 125 μA ±200 ±800 nA Power Monitor (Note 2) IPMON(OR) Power Monitor Output Current Operating Range IPMON(CAPA) Power Monitor Output Current Capability l ±200 VCC ≥ 12V, VPMON ≥ 0V, and V V = –9V, V I = –225mV, or V V = 9V, V I = 225mV l 900 1200 μA VCC ≥ 12V, VPMON ≥ 0.5V, and V V = –9V, V I = 225mV, or V V = 9V, V I = –225mV l –240 –1200 μA VCC ≥ 12V, VPMON ≥ 4V, and V V = –9V, V I = 225mV, or V V = 9V, V I = –225mV l –800 –1200 μA μA 2940f 3 LT2940 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. All specifications apply at 6V ≤ VCC ≤ 80V, unless otherwise specified. SYMBOL VPMON EPMON PARAMETER Power Monitor Output Compliance Voltage Power Monitor Output Total Error (Note 4) CONDITIONS MIN TYP MAX UNITS VCC ≤ 12V, IPMON ≥ 0μA l 0 VCC – 4.5 V 12V < VCC < 30V, IPMON ≥ 0μA l 0 7.5 V VCC ≥ 30V, IPMON ≥ 0μA l 0 12 V VCC ≤ 12V, IPMON < 0μA l 0.5 VCC – 4.5 V 12V < VCC < 30V, IPMON < 0μA l 0.5 7.5 V VCC ≥ 30V, IPMON < 0μA l 0.5 |V V • V I | ≤ 0.4V2 |V V • V I | ≤ 0.4V2, 25°C < TA ≤ 85°C 12 V ±2 ±5 %FS ±2.5 ±7 %FS |V V • V I | ≤ 0.4V2, LT2940C l ±2.5 ±9 %FS |V V • V I | ≤ 0.4V2, LT2940I l ±3.5 ±12 %FS Quadrants I and III of Shaded Region in Figure 4 l ±5 ±15 %FS 500 515 μA /V2 KPMON Power Monitor Scaling Coefficient IPMON = KPMON • V V • V I |V V • V I | = 0.4V2 l VV(OSP) Power Monitor Voltage Sense Input-Referred Offset Voltage V V = 0V l ±40 ±100 mV VI(OSP) Power Monitor Current Sense Input-Referred Offset Voltage V I = 0mV l ±2 ±6 mV IPMON(OS) Power Monitor Output Offset Current V V – = 0V, V I = 0mV l ±6 ±15 μA BWPMON Power Monitor Output Bandwidth RPMON = 2k 485 0.5 MHz Current Monitor (Note 2) IIMON(FS) Current Monitor Output Current Operating Range VIMON Current Monitor Output Compliance Voltage EIMON Current Monitor Output Total Error (Note 4) l ±200 VCC ≤ 12V, IIMON ≥ 0μA l 0 VCC – 4.5 V 12V < VCC < 30V, IIMON ≥ 0μA l 0 7.5 V VCC ≥ 30V, IIMON ≥ 0μA l 0 12 V VCC ≤ 12V, IIMON < 0μA l 0.5 VCC – 4.5 V 12V < VCC < 30V, IPMON < 0μA l 0.5 7.5 V VCC ≥ 30V, IPMON < 0μA l 0.5 12 V ±1.5 ±3 %FS |V I | ≤ 200mV, 25°C ≤ TA ≤ 85°C μA |V I | ≤ 200mV, LT2940C l ±2 ±3.5 %FS |V I | ≤ 200mV, LT2940I l ±2 ±4 %FS 200mV < |V I | ≤ 225mV l V I = ±200mV l 975 ±2.5 ±5 %FS 1000 1025 μA /V ±2.5 ±7 GIMON Current Monitor Scaling, IIMON = GIMON • VI VI(OSI) Current Monitor Current Sense Input-Referred Offset Voltage BWIMON Current Monitor Output Bandwidth RIMON = 2k Comparator Threshold Voltage CMP+ Rising l 1.222 ΔVCMP(HYST) Comparator Threshold Hysteresis CMP+ Falling l –15 –35 –60 mV ICMP(BIAS) Comparator Input Bias Current 1V ≤ VCMP+ ≤ 1.5V l ±100 ±300 nA CMPOUT Output Low Voltage CMP+ High, ICMPOUT = 3mA l 0.2 0.4 V l 1 mV MHz Comparator VCMP(TH) ICMPOUT(OL) 1.240 1.258 V 2940f 4 LT2940 ELECTRICAL CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. All specifications apply at 6V ≤ VCC ≤ 80V, unless otherwise specified. SYMBOL PARAMETER CONDITIONS ICMPOUT(LK) CMPOUT Leakage Current CMP+ Low, V CC = 36V, 0.4V ≤ VCMPOUT ≤ 36V l MIN TYP MAX ICMPOUT(OL) CMPOUT Output Low Voltage CMP+ Low, ICMPOUT = 3mA ICMPOUT(LK) CMPOUT Leakage Current CMP+ High, VCC = 36V, 0.4V ≤ VCMPOUT ≤ 36V tDLY Comparator Propagation Delay Output Pulling Down l VLATCH(IL) LATCH Input Low Voltage l 0.5 VLATCH(IO) LATCH Input Open Voltage l 1.25 VLATCH(IH) LATCH Input High Voltage l 2.0 ILATCH(LK) LATCH Input Allowable Leakage in Open State l ILATCH(BIAS) LATCH Input Bias Current UNITS ±0.15 ±1 l 0.2 0.4 V l ±0.15 ±1 μA 0.7 2 μs 0.8 1.2 V 1.5 1.95 V 2.2 2.5 V ±10 μA μA VLATCH = 0V l –11 –17 –23 μA VLATCH = 80V l 11 17 23 μA Note 3: The LT2940 may safely drive its own PMON and IMON output voltages above the absolute maximum ratings. Do not apply any external source that drives the voltage above absolute maximum. Note 4: Full-scale equals ±200μA. Note 5: V+ and V – pin voltages must each fall within the voltage sense pin operating range specification. Note 6: I+ and I – pin voltages must each fall within the current sense pin operating range specification. Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: All currents into pins are positive, and all voltages are referenced to GND unless otherwise noted. Current sourced by the PMON pin or the IMON pin is defined as positive; current sunk as negative. TYPICAL PERFORMANCE CHARACTERISTICS 800 VV = VV+ – VV – VI = VI+ – VI – PMON Total Error vs Sense Input Voltages 3 VCC ≥ 11V VPMON = 0.5V 2 600 200 –2V 0 0V 2V –400 –200 –2V 1 3 –4V VV = 8V 2V 0 4V –2 VI (mV) 200 2940 G01 –3 –200 |VV • VI| ≤ 0.4V2 TA = 25°C –100 1 0 –8V ≤ VV ≤ 8V –200mV ≤ VI ≤ 200mV |VV • VI| ≤ 0.4V2 0 100 200 VI (mV) 2940 G02 VCC = 12V –1 VCC = 12V –2 VV = 8V 8V 0 VCC = 80V 2 –1 –200 4V ONE REPRESENTATIVE UNIT 0V VV = –8V EPMON (%FS) IPMON (μA) 400 –4V PMON Error Band vs Temperature 4 EPMON (%FS) PMON Output Current vs Sense Input Voltages –3 –4 –50 VCC = 80V –25 50 25 0 75 TEMPERATURE (°C) 100 125 2949 G03 2940f 5 LT2940 TYPICAL PERFORMANCE CHARACTERISTICS 1500 PMON and IMON Voltage Compliance 300 VCC ≥ 15V VV = 40 • VI 500 IPMON (μA) TA = 25°C I = 200μA 200 OUTPUT CURRENT (μA) 1000 VPMON = 0V 0 VPMON = 0.5V VPMON = 4V –500 –1000 Supply Current vs Supply Voltage 3.6 100 VCC = 30V VCC = 6V 0 VCC = 12V I = –200μA –300 –2 0 VV • VI (V2) 2 4 –5 0 5 10 15 OUTPUT VOLTAGE (V) 2940 G04 2.6 VCC = 30V IPMON = –200μA IIMON = –200μA 2.4 20 0 20 2940 G05 IMON Current vs Current Sense Voltage 300 IPMON = 0μA IIMON = 0μA 3.0 2.8 VCC = 6V VCC = 12V –4 3.2 –100 –200 –1500 IPMON = 200μA IIMON = 200μA 3.4 ICC (mA) PMON Current vs Power Sense Product IMON Total Error vs Current Sense Voltage 2 VI = VI+ – VI – 40 60 VCC (V) ONE REPRESENTATIVE UNIT 2 –200mV ≤ VI ≤ 200mV VI – = 12V VCC = 12V 1 1 VCC = 12V 0 VCC = 80V –100 VIMON = 0.5V OUTPUT CURRENT IS APPROXIMATELY FLAT TO ABSOLUTE MAXIMUM VOLTAGE LIMITS –200 –300 –300 –200 –100 0 100 VI (mV) 200 EIMON (%FS) EIMON (%FS) IIMON (μA) 100 VIMON = 0V VCC = 80V 0 –1 VCC = 12V –1 VCC = 80V –2 300 100 2940 G06 IMON Error Band vs Temperature 3 200 0 80 –2 –200 0 VI (mV) 2940 G07 200 –3 –50 2940 G08 –25 50 25 0 75 TEMPERATURE (°C) 100 125 2949 G09 PMON Step Response PMON Step Response IMON Step Response RPMON = 2k ON 2VDC BIAS CL = 8pF VCC = 12V TA = 25°C VV = ±2V VI = 200mV RPMON = 2k ON 2VDC BIAS CL = 8pF VCC = 12V TA = 25°C VI = ±200mV VV = 2V RIMON = 2k ON 2VDC BIAS CL = 8pF VCC = 12V TA = 25°C VI = ±200mV VIMON 200mV/DIV VIMON 200mV/DIV VIMON 200mV/DIV 500ns/DIV 2940 G10 250ns/DIV 2940 G11 250ns/DIV 2940 G12 2940f 6 LT2940 TYPICAL PERFORMANCE CHARACTERISTICS PMON Input Feedthrough vs Frequency Power Supply Rejection Ratio vs Frequency 0 PMON OUTPUT SIGNAL (dBVPK) REJECTION RATIO (dBV) 80 60 IMON PMON 40 20 V = 12V CC RPMON = 5k ON 2VDC BIAS RIMON = 5k ON 2VDC BIAS TA = 25°C 0 100 1k 10k 100k FREQUENCY (Hz) 1M RELATIVE TO ±1VPK RPMON = 5k ON 2VDC BIAS –10 TA = 25°C –20 –30 VV = ±2VPK VI = 0mV, dV = 0 –40 VI = ±200mVPK VV = 0V, dI = 0 –50 –60 100 10k 100k 1M 10M FREQUENCY (Hz) 2940 G14 SEE TEST CIRCUITS FOR LOADING CONDITIONS 10M 2940 G13 PMON Frequency Response to Voltage Sense PMON Frequency Response to Current Sense 10 RELATIVE TO DC GAIN 0 I-TO-V AMP OUTPUT –10 –20 RL = 2k VV = ±2VPK VI = 200mVDC IPMON = ±200μAPK (NOM) TA = 25°C –40 100 RELATIVE PMON VOLTAGE (dBVPK) RELATIVE PMON VOLTAGE (dBVPK) 10 –30 RELATIVE TO DC GAIN 0 –20 –30 I-TO-V AMP OUTPUT –10 RL = 2k –30 V = ±200mV I PK IIMON = ±200μAPK (NOM) RL = 5k TA = 25°C –40 100 1k 10k 100k 1M 10M FREQUENCY (Hz) 2940 G17 SEE TEST CIRCUITS FOR LOADING CONDITIONS 25 OPEN COLLECTOR CURRENT (mA) RELATIVE IMON VOLTAGE (dBVPK) RL = 5k 1k Open Collector Current vs Open Collector Voltage 10 –20 VV = 2VDC VI = ±200mVPK IPMON = ±200μAPK (NOM) TA = 25°C 10k 100k 1M 10M FREQUENCY (Hz) 2940 G16 SEE TEST CIRCUITS FOR LOADING CONDITIONS IMON Frequency Response to Current Sense RELATIVE TO DC GAIN RL = 2k –40 100 1k I-TO-V AMP OUTPUT –10 RL = 5k 10k 100k 1M 10M FREQUENCY (Hz) 2940 G15 SEE TEST CIRCUITS FOR LOADING CONDITIONS 0 1k TA = 25°C OUTPUT PULLING LOW 20 15 VCC = 80V 10 VCC = 6V 5 0 0.1 10 1 OPEN COLLECTOR VOLTAGE (V) 100 2940 G18 2940f 7 LT2940 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. V+, V – (Pins 8, 7): Voltage Sense Inputs. The voltage difference between these pins is the voltage input factor to the power calculation multiplier. The difference may be positive or negative, but both pin voltages must be at or above GND – 100mV. The input differential voltage range is ±8V. Do not exceed 36V on either pin. 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. CMPOUT may be pulled up to 36V maximum. Do not sink more than 22mA DC. LATCH (Pin 9): Comparator Mode Input. Conditions at this three-state input pin control the comparator’s behavior. When LATCH is open, the comparator’s outputs track its input conditions (with hysteresis). When LATCH is held above 2.5V, the comparator’s outputs latch when CMP+ exceeds 1.24V (CMPOUT open, CMPOUT pull-down). While LATCH ≤ 0.5V or VCC < 2.5V, the comparator’s outputs clear (CMPOUT pull-down, CMPOUT open) regardless of the CMP+ pin voltage. The LATCH pin high impedance input state tolerates ±10μA of leakage current. Bypass this pin to GND to compensate for high dV/dt on adjacent pins. Do not exceed 100V on this pin. CMP+ (Pin 3): Positive Comparator Input. The integrated comparator resolves to high when the pin voltage exceeds the 1.24V internal reference. The comparator input has 35mV of negative hysteresis, which makes its falling trip point approximately 1.21V. Do not exceed 36V. Tie CMP+ to GND if unused. PMON (Pin 4): Proportional-to-Power Monitor Output. This push-pull output sources or sinks a current proportional to the product of the voltage sense and current sense inputs. A resistor from PMON to GND creates a positive voltage when the power product is positive. The full-scale output of ±200μA is generated for a sense input product of ±0.4V2. Do not exceed VCC + 1V, up to 16V maximum. Tie PMON to GND if unused. IMON (Pin 5): Proportional-to-Current Monitor Output. This push-pull output sources or sinks a current proportional to the voltage at the current sense input, which is typically generated by a sense resistor that measures a current. A resistor from IMON to GND creates a positive voltage when the sensed current is positive. The full-scale output of ±200μA is generated by a current sense input of ±200mV. Do not exceed VCC + 1V, up to 16V maximum. Tie IMON to GND if unused. GND (Pin 6): Device Ground. I+, I– (Pins 11, 10): Current Sense Inputs. The voltage difference at these pins represents the current input factor to the power calculation multiplier and to the current scaler. The difference may be positive or negative, but both pin voltages must be at least 4V and no more than 80V above GND, completely independent of the VCC voltage. Both pins sink approximately 100μA of bias current in addition to having an effective 5kΩ shunt between them. The input differential voltage range is ±200mV. Do not exceed ±36V differentially or 100V on either pin. VCC (Pin 12): Voltage Supply. The voltage supply operating range is 6V to 80V. When operating with VCC > 15V, package heating can be reduced by adding an external series dropping resistor. Bypass this pin to GND to improve supply rejection at frequencies above 10kHz as needed. Do not exceed 100V on this pin. Exposed Pad (Pin 13 in DFN Package): The exposed pad may be left open or connected to device ground. For best thermal performance, the exposed pad must be soldered to the PCB. 2940f 8 LT2940 FUNCTIONAL BLOCK DIAGRAM 11 10 I+ I– 12 6 GIMON = 1000 VCC μA V + GND IMON 5 – μA KPMON = 500 2 V 8 7 V+ + PMON 4 V– – 4-QUADRANT MULTIPLIER 3 CMP+ 1.24V VCC 9 LATCH BGAP REF AND UVLC UVLC + – CMPOUT D CLR 1 Q CMPOUT LE 2 LATCHLO THREE-STATE LATCHHI DECODE 2940 BD TEST CIRCUITS Resistor on DC Bias I-to-V Amplifier 12V PMON OR IMON VOUT RL PMON OR IMON RFB 4.99k RC 499Ω VOUT 2V 2940 TC01 Q1 2N2369 2V 2940 TC02 2940f 9 LT2940 APPLICATIONS INFORMATION Introduction Multiplier Operation The LT2940 power and current monitor brings together circuits necessary to measure, monitor and control power. In circuits where voltage is constant, power is directly proportional to current. The LT2940 enables power monitoring and control in applications where both the current and the voltage may be variable due to supply voltage uncertainty, component parametric changes, transient conditions, time-varying signals, and so forth. The LT2940 power and current monitor contains a fourquadrant multiplier designed to measure the voltage and current of a generator or load, and output signals proportional to power and current. Figure 1 shows a signal path block diagram. The operating ranges of the voltage sense and current sense inputs are included. To simplify the notation, the differential input voltages are defined as: The LT2940’s four-quadrant multiplier calculates instantaneous power from its voltage sense and current sense inputs. Its output driver sources and sinks current proportional to power (magnitude and direction), which affords flexible voltage scaling, simple filtering and, into a reference, bipolar signals. Its onboard comparator is the final piece required for integrated power monitoring. In addition, the LT2940 provides a proportional-to-current output that allows for equally straightforward scaling, filtering and monitoring of the sensed current. Please note: although standard convention defines currents as positive going into a pin (as is generally the case in the Electrical Characteristics table), the opposite is true of the PMON and IMON pins. Throughout this data sheet the power and current monitor output currents are defined positive coming out of PMON and IMON, respectively. Adopting this convention lets positive voltage differences at the current and voltage sense pins yield positive currents sourced from PMON and IMON that can be scaled to positive ground referenced voltages with a resistor. V V = V V+ – V V– (1a) V I = V I+ – V I– (1b) The full scale output of the multiplier core is ±0.4V2, which the PMON output driver converts to current through a scale factor of KPMON. (2) IPMON = KPMON • V V • V I µA K PMON = 500 V2 (3) The voltage across the current sense input pins is converted to a current by the IMON output driver through the scale factor of GIMON. IIMON = GIMON • VI (4) µA V (5) Both the PMON and IMON outputs reach full-scale at ±200μA. GIMON = 1000 The headroom and compliance limits for the input and output pins are summarized in Table 1 for easy reference. It is important to note that the current sense inputs, I+ and I–, operate over a 4V to 80V range completely independent of the LT2940’s supply pin, VCC. Note also that the inputs accept signals of either polarity, and that the VI = VI+ – VI– ±200mV (MAX) 11 10 I+ I– + GIMON = 1000 μA V IMON – VV = VV+ – VV – ±8V (MAX) 8 7 V + V– VV • VI = ±0.4V2 FULL-SCALE LT2940 + 5 ±200μA FULL-SCALE 4 ±200μA FULL-SCALE μA KPMON = 500 2 V PMON – 2940 F01 Figure 1. LT2940 Signal Path Diagram 2940f 10 LT2940 APPLICATIONS INFORMATION Table 1. LT2940 Essential Operating Parameters to Achieve Specified Accuracy (VCC Operating Range = 6V to 80V) PARAMETER SENSE INPUT PINS Voltage V+, V – PIN VOLTAGE LIMIT INPUT OPERATING RANGE SCALING TO OUTPUT MONITOR OUTPUT PINS OUTPUT OPERATING RANGE OUTPUT VOLTAGE COMPLIANCE 0V to VCC – 3V at VCC ≤ 12V VV = ±8V - - - - 0V TO 9V at 12V < VCC < 30V 0V to 18V at VCC ≥ 30V Current I+, I – 4V to 80V* VI = ±200mV GIMON = 1000μA /V IMON IIMON = ±200μA Sourcing: 0V to VCC – 4.5V at VCC ≤ 7.5V Power V+, V –, I+, I – See Above Limits VV • VI = ±0.4V2 KPMON = 500μA / V2 PMON IPMON = ±200μA 0V to 7.5V at 12V < VCC < 30V 0V to 12V at VCC ≥ 30V Sinking: As Above, Except Minimum is 0.5V * The current sense range is completely independent of the supply voltage. PMON and IMON outputs are capable of indicating forward and reverse flow of power and current, provided they are advantageously biased. The multiplier core full-scale product of ±0.4V2 may be reached over a range of voltage and current inputs, as shown in Figure 2. For example, voltage sense and current sense combinations of 8V and 50mV, 4V and 100mV, and 2V and 200mV each multiply to 0.4V2, and thus produce 200μA at PMON. This arrangement allows the core to operate at full-scale, and therefore at best accuracy, over a 4:1 range of current and voltage, a readily appreciated feature when monitoring power in variable supply applications. Essential Design Equations A few equations are needed to calculate input scaling factors and achieve a desired output. Consider the basic application in Figure 3, where the power PIN is to be measured as the product of voltage VIN and current IIN: PIN = VIN • IIN The actual measured quantities VIN and IIN are scaled to be level-compatible with the LT2940. In this basic application, a simple resistive voltage divider scales VIN, and a sense resistor scales IIN. V V = VIN • kV kV = 200 IPMON = 200μA VI = VI+ – VI– (mV) 100 100μA 25μA 12.5μA 25 1 (7b) V I = IIN • kI (8a) kI = RSENSE (8b) IPMON = KPMON • VIN • kV • IIN • kI (9a) IPMON = PIN • KPMON • kV • kI (9b) or 12.5 0.5 R1 R1 + R2 (7a) The PMON output current is given by: 50μA 50 (6) 2 VV = VV+ – VV – (V) 4 8 2940 F02 Figure 2. PMON Output Current as a Function of Sense Input Voltages The output current may be positive (sourcing) or negative (sinking) depending on the signs of VIN, kV, IIN, and kI. Provided that the magnitudes of VV and VI do not exceed 8V and 200mV as shown in Figure 2, at 2940f 11 LT2940 APPLICATIONS INFORMATION IIN PIN = VIN • IIN VIN RSENSE LOAD 11 10 I+ I– LT2940 + IMON – R2 8 R1 7 V+ V– IIMON 5 VIMON RIMON VV = VIN • R1 R1 mk V = R1 + R2 R1 + R2 VI = IIN • RSENSE mk I = RSENSE + PMON IPMON 4 – VPMON RPMON 2940 F03 Figure 3. Basic Power Sensing Application Showing Derivation of kV and kI the full-scale output current of ±200μA, the achievable full-scale power is: 0 . 4V 2 PIN(FS) = k V • kI (10) In some applications the PMON output is converted to a voltage by a load resistor: VPMON = IPMON • RPMON (11) The complete end-to-end scaling is then given by: VPMON = PIN • KPMON • kV • kI • RPMON (12) The current monitor output current at IMON is found by combining Equations 4 and 8a: IIMON = IIN • GIMON • kI (13) The output current may be positive (sourcing) or negative (sinking) depending on the signs of IIN and kI. Provided that the magnitude of VI does not exceed 200mV, at the full-scale output current of ±200μA the achievable fullscale input current is: 0 . 2V IIN(FS) = kI (14) If IMON current is converted to a voltage by a load resistor, then: VIMON = IIMON • RIMON (15) Accuracy The principal accuracies of the power and current monitor outputs are characterized as absolute percentages of fullscale output currents, using the nominal values of scaling parameters. The total error of the IPMON output, EPMON, is typically ±2%, and is defined as: µA • ( VV • VI ) IPMON − 500 2 V • 100 % EPMON = 200µA (17) Contributors to the power output accuracy such as the scaling (KPMON), the output offset (IPMON(OS)), and the voltage and current sense input offsets (VV(OSP) and VI(OSP)), are separately specified at key conditions and may be totaled using the root sum-of-squares (RSS) method. The total error of the IIMON output, EIMON, is typically ±1.5%, and is defined as: EIMON = μA • VI V • 100 % 200μ A IIMON − 1000 (18) Contributors to the current output accuracy such as the scaling (GIMON) and the current sense input offset (VI(OSI)) are separately specified at key conditions. Here again, use the RSS method of totaling errors. and the final end-to-end scaling is given by: VIMON = IIN • GIMON • kI • RIMON (16) 2940f 12 LT2940 APPLICATIONS INFORMATION Multiplier Operating Regions The operating regions of the four-quadrant multiplier are illustrated in Figure 4. Note that while Figure 2’s axes employed logarithmic (octave) scales to allow constant-power trajectories to be straight lines, Figure 4’s axes are linear to better accommodate negative inputs. Constant-power trajectories are thus arcs. The heavy line circumscribing the guaranteed accuracy region is limited both by the product of the sense inputs (the curved edges) and by each sense input’s differential range (the straight edges). The maximum product that realizes the specified accuracy is VV • VI = ±0.4V2, and it produces nominally full-scale output currents of IPMON = ±200μA. At the same time, the voltage and current sense inputs must not exceed ±8V and ±200mV, respectively. In the shaded functional region, multiplying occurs but the output current accuracy is derated as specified in the Electrical Characteristics section. The shaded functional region offers headroom beyond the guaranteed range in all quadrants, and excellent sourcing current operation beyond the standard +0.4V2 sense product limit in quadrants I and III. In quadrants II and IV, the PMON current is limited by compliance range, so accuracy is not specified. See the Electrical Characteristics and Typical Performance Characteristics sections for operation in these regions. Inputs beyond those ranges, and out to the absolute maximum ratings, are clipped internally. Range and Accuracy Considerations The LT2940’s performance and operating range may best be exploited by letting the broad application category steer design direction. Constant-power applications comprise power level alarm circuits, whether tripping a circuit breaker, activating auxiliary circuits, or simply raising an alarm, and single-level power servo loops. In such applications, accuracy is best when the full-scale output current of the LT2940 represents the power level of interest, i.e., the IPMON = 200μA load line (A) on Figure 5. Spans of voltage or current up to 4:1 naturally fit into the operating range of the LT2940. Special constant-power applications are the same types of circuits (level measuring, servos) with additional restrictions. If operating within the guaranteed accuracy region of Figure 4 is important over voltage or current spans wider than 4:1, let a PMON current less than full-scale represent the power level. For example, the load line (B) of IPMON = 50μA in Figure 5 covers a span of 16:1 (VV = 8V to 0.5V and VI = 200mV to 12.5mV). Note that operating along line (C), IPMON = 25μA allows a span of 32:1, but the channel offsets reduce the value of doing so. Operating 300 II 250 –150 100 –250 100μA 25μA (C) IV 12.5 –4 –2 0 VV (V) 2 4 6 8 (D) 25 CURRENT SENSE CLIPPED –6 (A) 50μA 50 LIMITED BY PMON COMPLIANCE –200 III –300 –12 –10 –8 IPMON = 200μA VI (mV) VI (mV) –100 GUARANTEED ACCURACY VOLTAGE SENSE CLIPPING –50 I 200 VOLTAGE SENSE CLIPPED 0 VOLTAGE SENSE CLIPPED 150 50 CURRENT SENSE CLIPPING LIMITED BY PMON COMPLIANCE 200 100 400 I CURRENT SENSE CLIPPED 10 12 2940 F04 Figure 4. Multiplier Operating Regions vs Sense Input Voltages. Accuracy Is Derataed in Shaded Areas (B) GUARANTEED ACCURACY 0.5 1 4 2 VV (V) 16 8 2940 F05 Figure 5. Various Constant-Power Curves in Quadrant I 2940f 13 LT2940 APPLICATIONS INFORMATION below full-scale also affords scaling flexibility. Line (D) along IPMON = 100μA covers a 4:1 range like (A), but the maximum VI is 100mV, which reduces voltage drop and dissipation in the sense resistor. Variable power applications comprise power measuring, whether battery charging, energy metering or motor monitoring, variable load-boxes, and other circuits where the significant metric is not a single value, and voltage and current may be independent of each other. Design in this case requires mapping the LT2940’s sense ranges to cover the maximum voltage and the maximum current, while considering whether the power represented is at, above, or below full-scale IPMON. For example, setting it at full-scale puts all values in the accurate range, setting it above puts more accuracy in nominal power levels and less accuracy in perhaps rarely encountered high levels, and setting below might afford flexibility to lower dissipation in the current sense resistor. similar way, a capacitor load on IMON produces a voltage proportional to charge that can be used to create a coulomb counter. Comparator Function The LT2940’s integrated comparator features an internal fixed reference, complementary open-collector outputs and configurable latching. A rising voltage at the CMP+ pin is compared to the internal 1.24V threshold. 35mV (typical) negative hysteresis provides glitch protection and makes falling inputs trip the comparator at about 1.21V. The comparator result drives the open-collector CMPOUT and CMPOUT pins which, when pulling down, sink at least 3mA down to 0.4V. See the Typical Performance Characteristics for more information. Complementary comparator outputs save external components in some applications. The CMPOUT and CMPOUT pins may be pulled up externally to 36V maximum. Comparator Latching Output Filtering and Integration Lowpass filtering the output power or current signal is as simple as adding a capacitor in parallel with the output voltage scaling resistor at PMON or IMON. For example, adding 1nF in parallel with the PMON load resistor on the front page application creates a lowpass corner frequency of approximately 6.4kHz on the power monitor voltage. Loaded by only a capacitor, the PMON pin voltage is proportional to the time-integral of power, which is energy. The integrating watt-hour meter application shown on the back page takes advantage of this convenience. In a The LATCH pin controls the behavior of the comparator outputs. When the LATCH pin is open, the comparator output latch is transparent. Leakage currents up to ±10μA will not change the decoded state of the LATCH pin. Internal circuits weakly drive the pin to about 1.5V. Adding a 10nF capacitor between LATCH and GND protects against high dV/dt on adjacent pins and traces. Where more than 30V and long inductive leads will be connected to LATCH, damp potentially damaging ringing with a circuit like that shown in Figure 6. 4V TO 80V R9B 49.9k LONG WIRE R9A 20k I+ RESET I– LATCH LT2940 C2 10nF GND 2940 F06 Figure 6. LATCH Pin Protective Damping 2940f 14 LT2940 APPLICATIONS INFORMATION When the LATCH pin voltage exceeds 2.5V, the next high result from the comparator also enables the comparator latch. The CMPOUT pin goes open (high), and the CMPOUT pin sinks current (low) regardless of the changes to the CMP+ level until the latch is cleared. Latch activation is level sensitive, not edge sensitive, so if CMP+ > 1.24V when LATCH is brought above 2.5V, the comparator result is high, and the latch is set immediately. The LATCH pin voltage may be taken safely to 80V regardless of the VCC pin voltage. Thermal Considerations If operating at high supply voltages, do not ignore package dissipation. At 80V the dissipation could reach 400mW; more if IMON or PMON current exceeds full-scale. Package thermal resistance is shown in the Pin Configuration section. Package dissipation can be reduced by simply adding a dropping resistor in series with the VCC pin, as shown in Figure 7. The operating range of the current sense input pins I+ and I– , which extends to 80V independent of VCC, make this possible. The voltage ranges of the V+, V– , PMON and IMON pins are, however, limited by VCC. Consult Table 1 during design. Operating an open-collector output pin with simultaneously large current and large voltage bias also contributes to package heating and must be avoided. The latch is released and the comparator reports a low when LATCH ≤ 0.5V or when VCC < 2.3V regardless of the CMP+ pin voltage. In this state, the CMPOUT pin sinks current (low), while the CMPOUT pin goes open (high). As with latching, clearing is level-sensitive: comparator outputs react to the input signal as soon as LATCH ≥ 1.25V and VCC > 2.7V. RS 100V MAX 0A TO 1.3A 30V TO 80V 5mA MAX 36V MAX R14 20k OVP OVERPOWER (OVP) GOES HIGH WHEN LOAD POWER > 40W kV = 1 15 kI = 150mΩ I– R2 140k LATCH V+ LT2940 R1 10.0k CMPOUT CMP+ V– PMON R3 6.19k I+ VCC CMPOUT LOAD 150mΩ 1/2W R12 3.9k 10% 1/8W GND IMON 2940 F07 R4 13.7k VPMON SCALE = 10 W V 40W FULL-SCALE Figure 7. Supply Resistor Reduces Package Heating by Reducing VCC Voltage 2940f 15 LT2940 TYPICAL APPLICATIONS 120W Supply Monitor Includes ICC of LT2940 SUPPLY 30V TO 80V 100V (MAX) RS 0A TO 4A LOAD 50mΩ 1W VLOGIC I+ R14 3.9k R12 3.9k 1/8W 5mA MAX I– VCC R2 140k LATCH OVP CMPOUT OVERPOWER (OVP) GOES HIGH WHEN SUPPLY POWER > 120W V+ LT2940 R1 10.0k CMPOUT CMP+ V– PMON R3 6.19k IMON GND 2940 TA02 R4 13.7k VPMON SCALE = 30 W V kV = 120W FULL-SCALE 1 15 kI = 50mΩ 12.5W PWM Heat Source RS 200mΩ 3 INPUT 9.5V TO 14.5V + C1 100μF 25V R6 10k Q3 2N3906 I+ VCC I– LT2940 R5 10k LATCH V+ CMPOUT CMPOUT D1 1N5819 Q2 TP0610 V– R7* 7Ω HEATSINK Q = 12.5W R2 102k R1 25.5k CMP+ PMON GND IMON C4 4.7μF R4 15.0k 2940 TA03 1 5 kI = 200mΩ 3 tOFF z1.7ms kV = Q1 FDS3672 * SEVEN 50Ω, 5W RESISTORS IN PARALLEL. MULTIPLE UNITS FACILITATE SPREADING HEAT. 2940f 16 LT2940 TYPICAL APPLICATIONS 30W Linear Heat Source RS 200mΩ 3 10V TO 40V + C1 100μF 50V R3 10k VCC I+ R2 102k LT2940 C2 22nF D2 27V I– V+ V R1 25.5k – V+ R PMON GND IMON LM334 V– R4 680Ω R5 6.8k D1 1N457 HEATSINK Q = 30W R6 51Ω Q1 VN2222 R8 1k R7 3.3k C3 470pF kV = 1 15 kI = 200mΩ 3 Q2 TIP129 R9 10k Q3 D44VH11 R10 100Ω 10A/V R11 100mΩ 2940 TA04 Wide Input Range 10W PWM Heat Source RS 200mΩ 3 22.4V TO 72V + 12V C1 100μF 100V R6 10k Q3 2N3906 R5 10k I+ VCC I– LT2940 LATCH V+ CMPOUT CMPOUT V CMP+ – R2 220k D2 1N4148 12V R1 13k Q2 BSS123 R7 50Ω 25W HEATSINK Q = 10W D1 MUR1100E D3 1N4148 PMON GND IMON C4 4.7μF 2940 TA05 R4 68k 13 233 kI = 200mΩ 3 tOFF z2ms kV = C2 100nF Q1 FDS3672 2940f 17 LT2940 TYPICAL APPLICATIONS 8V to 32V, 8W Load 12V RS 200mΩ 8V TO 32V R3 2k 12V VCC I– I+ R2 30k LT2940 C1 100nF V+ V+ R1 10k LM334 V– R7 6.8Ω 10W R V– R4 680Ω R5 6.8k IMON GND PMON kV = D1 1N457 1 4 200μA/A CURRENT MONITOR OUTPUT kI = 200mΩ R6 10Ω Q1 FDB3632 C4 100nF 2940 TA06 Adjustable 0W to 10W Load Box with UVLO and Thermal Shutdown 10V TO 40V INPUT R2 120k V – V+ 12V VCC LATCH 12V R15 10k R16 10k C13 10nF R13 10k I+ I– PMON CMPOUT CMPOUT IMON GND CMP+ R4 4.99k TEMP R10 ADJ 500Ω D1 1N4003 12V LT2940 R12 12k 1A/V CURRENT MONITOR OUTPUT R1 30k R11 33Ω C11 10nF Q2 2N3904* RS 200mΩ R14 10Ω Q3 2N3906 Q1 FDB3632 ICONTROL = 50mW/μA R3B 91k UVLO R3A 13k 0W TO 10W ADJ 10-TURN R17 100Ω – + OA Q4 2N3906 R18 1k kV = R19 10k + – 200mV REF LT1635 1 5 kI = 200mΩ 2940 TA07 *THERMAL SHUTDOWN; COUPLE TO Q1’s HEAT SINK 2940f 18 LT2940 TYPICAL APPLICATIONS 1-Cell Monitor with Bottom-Side Sense 12V C1 100nF R12 1k 5% RS1 215Ω 1W/V R4 ±2.5W MAX 12.4k RS2 215Ω I+ VCC R2 30k 1% R1 121k LT2940 V– IMON D1 5.1V CHARGER+ V+ PMON R5 4.99k LOAD+ I– CYCLON 2V, 4.5AH DT CELL* LT1635 1A/V ±1A MAX + REF – 200mV Q1 2N3904 12V + OA – GND Q2 2N3904 2940 TA08 R6 1k 1% kV = 121 = 0.8 151 R7 200Ω 1% R9 200Ω 1% R8 1k 1% RS3 200mΩ kI = 200mΩ LOAD– CHARGER– *www.hawkerpowersource.com (423) 238-5700 Motor Monitor with Circuit Breaker RS 25mΩ 2 12V + I+ VCC I– LT2940 R3 10k RESET LATCH V+ CMPOUT CMPOUT V– CMP+ IMON GND PMON VIMON 6.5A/V 2940 TA09 C5 33nF R5 12.4k R4 4.99k C10 100μF 25V R2A 10k 1% R1 10k 1% MUR120 GE 5BPA34KAA10B 12V, 8A PM FIELD R2B 10k 1% VPMON 100W/V C4 100nF 1 3 kI = 25mΩ 2 OVERCURRENT TRIP = 8A kV = Q1 FDB3632 2940f 19 LT2940 TYPICAL APPLICATIONS 28V Power to Frequency Converter RS 200mΩ 28V INPUT 10V TO 40V LOAD R2 120k kV = 1 5 kI = 200mΩ I+ VCC V+ V– PMAX = 10W fOUT = LATCH 10W 1000Hz LT2940 R1B 30k Q2 R5, 100k CMPOUT PMON C7 10nF R1A 30k I– VCC D3 D4 R6, 100k CMPOUT VCC IMON GND CMP+ Q3 IN + C5 1μF WIMA IN – D2 D1 10V LTC1440 + – V+ C6 VCC 100nF OUT HYST REF = 1N4148 OPTO-ISOLATOR Q1 R4B 10k R4A 240k CENTRAL SEMI CCLM2700 R9 1M V– = 2N7000 GND C4 2.2nF 2940 TA10 Secondary-Side AC Circuit Breaker T1 + R0 10Ω C1A 220μF 25V R2 120k 12.6VAC SECONDARY R9 10k R1 30k RS 200mΩ 3 Q4 RESISTIVE LOAD 2X FDS3732 Q1 D1 1N4001 I+ VCC VCC I– LATCH R11 10k V+ R6 1k D3 5.1V D2 1N4001 Q2 Q5 R10 1k Q6 R7 1k Q7 LT2940 V– IMON CMPOUT CMP+ GND PMON Q3 R12 10k CMPOUT + C1B 220μF 25V Q8 R3 15k 1A/V 3APK 1.25A TRIP R4 15k 10W/V 30WPK kV = 30 = 1 150 5 kI = 200mΩ 3 = 2N3906 2940 TA11 2940f 20 LT2940 TYPICAL APPLICATIONS AC Power and Current Monitor T1 12.6VAC SECONDARY + RS 200mΩ 3 C1A 220μF 25V D1 1N4001 R3 10Ω VCC + LOAD I+ I– V+ C1B 220μF 25V V– D3 5.1V D2 1N4001 kV = 1 5 kI = 200mΩ 3 R1 30k LT2940 R2 120k R6 1k GND PMON 2940 TA12 IMON R4 15k 10W/V ±30WPK R5 15k 1A/V ±3APK Fully Isolated AC Power and Current Monitor 7A 1 • 117V “L” • T1 500 RS1 RS2 4.99Ω 4.99Ω VCC VCC 15V C1 47μF 25V R12 1k R4 4.22k 1kW/ V ±853 WPK R5 4.99k C12 100nF D1 5.1V VCC I+ I– D2 D4 V+ R1A 68.1Ω PMON LT2940 C2 100nF IMON R2B R1B 68.1Ω 200Ω 1% V– 10A/V ±10APK GND D3 D5 R7 10k 2940 TA13 kV = 68 . 1 + 68 . 1 108 1 • = 200 + 200 + 68 . 1 + 68 . 1 1168 42 . 5 8 LOAD R2A 200Ω 1% R6 10k • • 10.8V 117V T2 117V “N” ISOLATION BARRIER = 1N4148 T1 = MINNTRONIX 4810966R kI = 4 . 99 + 4 . 99 10 = 500 501 T2 = 1168:108 POTENTIAL TRANSFORMER IN CONSTRUCTING THIS CIRCUIT, THE CUSTOMER AGREES THAT, IN ADDITION TO THE TERMS AND CONDITIONS ON LINEAR TECHNOLOGY CORPORATION’S (LTC) PURCHASE ORDER DOCUMENTS, LTC AND ANY OF ITS EMPLOYEES, AGENTS, REPRESENTATIVES AND CONTRACTORS SHALL HAVE NO LIABILITY, UNDER CONTRACT, TORT OR ANY OTHER LEGAL OR EQUITABLE THEORY OF RECOVERY, TO CUSTOMER OR ANY OF ITS EMPLOYEES, AGENTS, REPRESENTATIVES OR CONTRACTORS, FOR ANY PERSONAL INJURY, PROPERTY DAMAGE, OR ANY OTHER CLAIM (INCLUDING WITHOUT LIMITATION, FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES) RESULTING FROM ANY USE OF THIS CIRCUIT, UNDER ANY CONDITIONS, FORESEEABLE OR OTHERWISE. CUSTOMER ALSO SHALL INDEMNIFY LTC AND ANY OF ITS EMPLOYEES, AGENTS, REPRESENTATIVES AND CONTRACTORS AGAINST ANY AND ALL LIABILITY, DAMAGES, COSTS AND EXPENSES, INCLUDING ATTORNEY’S FEES, ARISING FROM ANY THIRD PARTY CLAIMS FOR PERSONAL INJURY, PROPERTY DAMAGE, OR ANY OTHER CLAIM (INCLUDING WITHOUT LIMITATION, FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES) RESULTING FROM ANY USE OF THIS CIRCUIT, UNDER ANY CONDITIONS, FORESEEABLE OR OTHERWISE. 2940f 21 LT2940 PACKAGE DESCRIPTION DD Package 12-Lead Plastic DFN (3mm × 3mm) (Reference LTC DWG # 05-08-1725 Rev A) 0.70 ±0.05 3.50 ±0.05 2.10 ±0.05 2.38 ±0.05 1.65 ±0.05 PACKAGE OUTLINE 0.25 ± 0.05 0.45 BSC 2.25 REF RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 3.00 ±0.10 (4 SIDES) R = 0.115 TYP 7 0.40 ± 0.10 12 2.38 ±0.10 1.65 ± 0.10 PIN 1 NOTCH R = 0.20 OR 0.25 × 45° CHAMFER PIN 1 TOP MARK (SEE NOTE 6) 6 0.200 REF 1 0.23 ± 0.05 0.45 BSC 0.75 ±0.05 2.25 REF (DD12) DFN 0106 REV A 0.00 – 0.05 BOTTOM VIEW—EXPOSED PAD NOTE: 1. DRAWING IS NOT A JEDEC PACKAGE OUTLINE 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5. EXPOSED PAD AND TIE BARS SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 2940f 22 LT2940 PACKAGE DESCRIPTION MS Package 12-Lead Plastic MSOP (Reference LTC DWG # 05-08-1668 Rev Ø) 0.889 p 0.127 (.035 p .005) 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 4.039 p 0.102 (.159 p .004) (NOTE 3) 0.65 (.0256) BSC 0.42 p 0.038 (.0165 p .0015) TYP 0.406 p 0.076 (.016 p .003) REF 12 11 10 9 8 7 RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) DETAIL “A” 3.00 p 0.102 (.118 p .004) (NOTE 4) 4.90 p 0.152 (.193 p .006) 0o – 6o TYP GAUGE PLANE 0.53 p 0.152 (.021 p .006) 1 2 3 4 5 6 1.10 (.043) MAX DETAIL “A” 0.18 (.007) 0.86 (.034) REF SEATING PLANE 0.22 – 0.38 (.009 – .015) TYP 0.650 (.0256) BSC NOTE: 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX 0.1016 p 0.0508 (.004 p .002) MSOP (MS12) 1107 REV Ø Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 2940f 23 LT2940 TYPICAL APPLICATION Integrating Watt-Hour Meter 6V TO 80V 0A TO 2A LOAD (80W MAX) 5V IN 5V OUT SHDN C16 LT3014 1μF ADJ GND R17 309k C17 0.47μF VCC I+ C19 0.1μF C20 0.1μF V+ S1B S2B S3B S4B I– R2 215k CB+ CB – LTC6943 R16 100k V+ R15 24.9k kV = RS 100mΩ V+ V– – + R14 20.0k CMP+ LT2940 LTC6702 1 20 V– SHA R18 49.9k GND Q1 2N7002 12V Q RESET VSS IMON kI = 100mΩ CT 2.2μF C18 0.1μF VDD F CMPOUT PMON R1 11.3k CA– 5V LATCH GND C1 1μF CA+ CMPOUT – + R13 4.99k S1A S2A S3A S4A COSC 1024 COUNTS = 1 WATT-HOUR CD4040 RESET 2940 TA14 RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LTC1966 Precision Micropower Delta-Sigma RMS-to-DC Converter 2.7V to 12V Supply Voltage, 170μA Supply Current LTC1968 Precision Wide Bandwidth RMS-to-DC Converter 4.5V to 6V Supply Voltage, 500kHz 3dB-Error BW LTC6101/ LTC6101HV High Voltage, High Side, Precision Current Sense Amplifiers 4V to 60V/ 5V to 100V, Gain Configurable, SOT-23 LTC6104 Bidirectional High Side, Precision Current Sense Amplifier 4V to 60V, Gain Configurable, 8-Pin MSOP LTC6106 Low Cost, High Side Precision Current Sense Amplifier 2.7V to 36V, Gain Configurable, SOT23 LTC4151 High Voltage I2C Current and Voltage Monitor Wide Operating Range: 7V to 80V LTC4215 Positive Hot Swap Controller with ADC and I2C 8-Bit ADC Monitoring Current and Voltages, Supplies from 2.9V to 15V LT4256-1/ LT4256-2 Positive 48V Hot Swap Controllers with OpenCircuit Detect Foldback Current Limiting, Open-Circuit and Overcurrent Fault Output, Up to 80V Supply LTC4260 Positive High Voltage Hot Swap Controller With ADC and I2C Monitoring Wide Operating Range: 8.5V to 80V LTC4261 Negative Voltage Hot Swap Controller With ADC and I2C Monitoring Floating Topology Allows Very High Voltage Operation 2940f 24 Linear Technology Corporation LT 1109 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2009