LT2940IDDPBF

LT2940 Power and Current Monitor FEATURES n n n n n n n n n DESCRIPTION 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. 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. 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 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 TYPICAL APPLICATION Load Monitor Alarms Above 60W ILOAD 6V TO 80V 20mΩ 2W 5V VCC 1k LATCH CMPOUT LED ON WHEN PLOAD > 60W CMPOUT CMP+ PMON VPMON = PLOAD • 20.75 mV W 24.9K kV = 1 12 kI = 20mΩ PLOAD = VLOAD • ILOAD 2940 TA01a Monitor Output Level and Load Power 2.5 + VLOAD – VPMON (V) 80V 30V 2.0 15V 10V 1.5 VLOAD = 6V 72 PLOAD (W) 96 120 0A TO 10A LOAD I– 110k I+ LED ON LT2940 V+ 10.0k V– 1.0 LED OFF 48 60W ALARM 0.5 24 GND IMON VIMON = ILOAD • 100 4.99k mV A 0 0 2 4 6 8 ILOAD (A) 10 12 14 2940 TA01b 0 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 CMPOUT CMP+ PMON IMON GND TOP VIEW 1 2 3 4 5 6 13 12 VCC 11 I+ 10 I – 9 LATCH 8 V+ 7 V– CMPOUT CMPOUT CMP+ PMON IMON GND 1 2 3 4 5 6 12 11 10 9 8 7 VCC I+ I– LATCH V+ V– DD PACKAGE 12-LEAD (3mm 3mm) PLASTIC DFN TJMAX = 125°C, θJA = 43°C/W EXPOSED PAD (PIN 13) PCB GND CONNECTION OPTIONAL MS PACKAGE 12-LEAD PLASTIC MSOP TJMAX = 125°C, θJA = 135°C/W ORDER INFORMATION LEAD FREE FINISH LT2940CDD#PBF LT2940IDD#PBF LT2940CMS#PBF LT2940IMS#PBF TAPE AND REEL LT2940CDD#TRPBF LT2940IDD#TRPBF LT2940CMS#TRPBF LT2940IMS#TRPBF PART MARKING* LDPP LDPP 2940 2940 PACKAGE DESCRIPTION 12-Lead Plastic DFN 12-Lead Plastic DFN 12-Lead Plastic MSOP 12-Lead Plastic MSOP TEMPERATURE RANGE 0°C to 70°C –40°C to 85°C 0°C to 70°C –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 SYMBOL Supply VCC ICC VCC(UVLC) ΔVCC(HYST) Voltage Sense VVSEN(OR) Voltage Sense Pin Operating Range V+ Pin and V – Pin VV VCC ≤ 12V 12V < VCC < 30V VCC ≥ 30V Voltage Sense Differential Input Voltage Range VCC < 11V (Note 5) VV = V V+ – V V – VV(CL) IVSEN ΔIVSEN Current Sense VISEN(OR) VI Current Sense Pin Operating Range I+ Pin and I – Pin Current Sense Differential Input Voltage Range (Note 6) VI = V I + – V I – Current Sense Differential Clipping Limit (Note 6) Current Sense Input Bias Current I+ Pin and I – Pin Current Sense Input Offset Current ΔIISEN = II+ – I I – Power Monitor Output Current Operating Range Power Monitor Output Current Capability VCC ≥ 12V, VPMON ≥ 0V, and V V = –9V, V I = –225mV, or V V = 9V, V I = 225mV VCC ≥ 12V, VPMON ≥ 0.5V, and V V = –9V, V I = 225mV, or V V = 9V, V I = –225mV VCC ≥ 12V, VPMON ≥ 4V, and V V = –9V, V I = 225mV, or V V = 9V, V I = –225mV V I+ = V I – l l l l l l l l l 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. PARAMETER Supply Voltage Operating Range Supply Current Supply Undervoltage Latch Clear Supply Undervoltage Hysteresis IPMON = +200μA, IIMON = +200μA (Note 2) VCC Falling VCC Rising CONDITIONS l l l l MIN 6 2 2.3 20 –0.1 –0.1 –0.1 ±(VCC – 3) ±8 ±9 –300 TYP MAX 80 UNITS V mA V mV V V V V V V 3.5 2.5 75 5 2.7 100 VCC – 3 9 18 VCC ≥ 11V VCC ≥ 12V Voltage Sense Differential Clipping Limit (Note 5) Voltage Sense Input Bias Current V+ Pin and V – Pin Voltage Sense Input Offset Current ΔIVSEN = IV+ – IV – –100 ±50 100 ±150 nA nA V V+ = V V – l 4 ±200 80 V mV VI(CL) IISEN ΔIISEN l l l ±225 75 100 ±200 125 ±800 mV μA nA Power Monitor (Note 2) IPMON(OR) IPMON(CAPA) l l ±200 900 1200 μA μA l –240 –1200 μA l –800 –1200 μA 2940f 3 LT2940 ELECTRICAL CHARACTERISTICS SYMBOL VPMON PARAMETER Power Monitor Output Compliance Voltage 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. CONDITIONS VCC ≤ 12V, IPMON ≥ 0μA 12V < VCC < 30V, IPMON ≥ 0μA VCC ≥ 30V, IPMON ≥ 0μA VCC ≤ 12V, IPMON < 0μA 12V < VCC < 30V, IPMON < 0μA VCC ≥ 30V, IPMON < 0μA l l l l l l MIN 0 0 0 0.5 0.5 0.5 TYP MAX VCC – 4.5 7.5 12 VCC – 4.5 7.5 12 UNITS V V V V V V %FS %FS %FS %FS %FS μA /V2 mV mV μA MHz μA EPMON Power Monitor Output Total Error (Note 4) |V V • V I | ≤ 0.4V2 |V V • V I | ≤ 0.4V2, 25°C < TA ≤ 85°C |V V • V I |V V • V I | ≤ 0.4V2, LT2940C | ≤ 0.4V2, LT2940I l l l l l l l ±2 ±2.5 ±2.5 ±3.5 ±5 485 500 ±40 ±2 ±6 0.5 l ±5 ±7 ±9 ±12 ±15 515 ±100 ±6 ±15 Quadrants I and III of Shaded Region in Figure 4 KPMON VV(OSP) VI(OSP) IPMON(OS) BWPMON IIMON(FS) VIMON Power Monitor Scaling Coefficient IPMON = KPMON • V V • V I Power Monitor Voltage Sense Input-Referred Offset Voltage Power Monitor Current Sense Input-Referred Offset Voltage Power Monitor Output Offset Current Power Monitor Output Bandwidth Current Monitor Output Current Operating Range Current Monitor Output Compliance Voltage VCC ≤ 12V, IIMON ≥ 0μA 12V < VCC < 30V, IIMON ≥ 0μA VCC ≥ 30V, IIMON ≥ 0μA VCC ≤ 12V, IIMON < 0μA 12V < VCC < 30V, IPMON < 0μA VCC ≥ 30V, IPMON < 0μA EIMON Current Monitor Output Total Error (Note 4) |V I | ≤ 200mV, 25°C ≤ TA ≤ 85°C |V I | ≤ 200mV, LT2940C |V I | ≤ 200mV, LT2940I 200mV < |V I | ≤ 225mV GIMON VI(OSI) BWIMON Comparator VCMP(TH) ΔVCMP(HYST) ICMP(BIAS) ICMPOUT(OL) Comparator Threshold Voltage Comparator Threshold Hysteresis Comparator Input Bias Current CMPOUT Output Low Voltage CMP+ Rising CMP+ Falling 1V ≤ VCMP+ ≤ 1.5V CMP+ High, ICMPOUT = 3mA Current Monitor Scaling, IIMON = GIMON • VI Current Monitor Current Sense Input-Referred Offset Voltage Current Monitor Output Bandwidth RIMON = 2k V I = ±200mV |V V • V I | = 0.4V2 V V = 0V V I = 0mV V V – = 0V, V I = 0mV RPMON = 2k Current Monitor (Note 2) ±200 0 0 0 0.5 0.5 0.5 ±1.5 l l l l l l l l l l l VCC – 4.5 7.5 12 VCC – 4.5 7.5 12 ±3 ±3.5 ±4 ±5 1025 ±7 ±2 ±2 ±2.5 V V V V V V %FS %FS %FS %FS μA /V mV MHz 975 1000 ±2.5 1 l l l l 1.222 –15 1.240 –35 ±100 0.2 1.258 –60 ±300 0.4 V mV nA V 2940f 4 LT2940 ELECTRICAL CHARACTERISTICS SYMBOL ICMPOUT(LK) ICMPOUT(OL) ICMPOUT(LK) tDLY VLATCH(IL) VLATCH(IO) VLATCH(IH) ILATCH(LK) ILATCH(BIAS) PARAMETER CMPOUT Leakage Current CMPOUT Output Low Voltage CMPOUT Leakage Current Comparator Propagation Delay LATCH Input Low Voltage LATCH Input Open Voltage LATCH Input High Voltage LATCH Input Allowable Leakage in Open State LATCH Input Bias Current VLATCH = 0V VLATCH = 80V 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. 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. CONDITIONS CMP+ Low, V CC = 36V, 0.4V ≤ VCMPOUT ≤ 36V MIN l l l l l l l l l l TYP ±0.15 0.2 ±0.15 0.7 MAX ±1 0.4 ±1 2 1.2 1.95 2.5 ±10 UNITS μA V μA μs V V V μA μA μA CMP+ Low, ICMPOUT = 3mA CMP+ High, VCC = 36V, 0.4V ≤ VCMPOUT ≤ 36V Output Pulling Down 0.5 1.25 2.0 0.8 1.5 2.2 –11 11 –17 17 –23 23 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. TYPICAL PERFORMANCE CHARACTERISTICS PMON Output Current vs Sense Input Voltages 800 600 EPMON (%FS) 400 –4V IPMON (μA) 200 –2V 0 –200 4V –400 –200 8V 0 VI (mV) 200 2940 G01 PMON Total Error vs Sense Input Voltages 3 2 ONE REPRESENTATIVE UNIT –2V 0V 1 0 4V –1 –2 –3 –200 VV = 8V |VV • VI| ≤ 0.4V2 TA = 25°C –100 0 VI (mV) 2940 G02 PMON Error Band vs Temperature 4 3 VV = VV+ – VV – VI = VI+ – VI – VV = –8V VCC ≥ 11V VPMON = 0.5V –4V VV = 8V EPMON (%FS) 2 1 0 –1 –2 –3 –4 –50 –8V ≤ VV ≤ 8V –200mV ≤ VI ≤ 200mV |VV • VI| ≤ 0.4V2 VCC = 80V VCC = 12V 2V 0V 2V VCC = 12V VCC = 80V –25 50 25 0 75 TEMPERATURE (°C) 100 125 100 200 2949 G03 2940f 5 LT2940 TYPICAL PERFORMANCE CHARACTERISTICS PMON Current vs Power Sense Product 1500 1000 500 IPMON (μA) 0 –500 –1000 –1500 –4 –2 0 VV • VI (V2) 2 4 2940 G04 PMON and IMON Voltage Compliance 300 200 OUTPUT CURRENT (μA) 100 0 –100 –200 –300 –5 0 5 10 15 OUTPUT VOLTAGE (V) I = –200μA VCC = 6V VCC = 12V VCC = 30V 20 2940 G05 Supply Current vs Supply Voltage 3.6 IPMON = 200μA IIMON = 200μA VCC ≥ 15V VV = 40 • VI TA = 25°C I = 200μA 3.4 3.2 ICC (mA) 3.0 2.8 2.6 2.4 0 20 40 VCC = 30V VCC = 6V VCC = 12V VPMON = 0V VPMON = 0.5V VPMON = 4V IPMON = 0μA IIMON = 0μA IPMON = –200μA IIMON = –200μA 60 VCC (V) 80 100 2940 G06 IMON Current vs Current Sense Voltage 300 200 1 100 EIMON (%FS) IIMON (μA) 0 VIMON = 0V VI = VI+ – VI – 2 IMON Total Error vs Current Sense Voltage ONE REPRESENTATIVE UNIT 3 2 1 VCC = 12V 0 VCC = 80V –1 –2 –2 –200 EIMON (%FS) IMON Error Band vs Temperature –200mV ≤ VI ≤ 200mV VI – = 12V VCC = 12V VCC = 80V 0 –1 –100 VIMON = 0.5V –200 –300 –300 OUTPUT CURRENT IS APPROXIMATELY FLAT TO ABSOLUTE MAXIMUM VOLTAGE LIMITS –200 –100 0 100 VI (mV) 200 300 2940 G07 VCC = 12V VCC = 80V 0 VI (mV) 200 2940 G08 –3 –50 –25 50 25 0 75 TEMPERATURE (°C) 100 125 2949 G09 PMON Step Response RPMON = 2k ON 2VDC BIAS CL = 8pF VCC = 12V TA = 25°C VV = ±2V VI = 200mV PMON Step Response RPMON = 2k ON 2VDC BIAS CL = 8pF VCC = 12V TA = 25°C VI = ±200mV VV = 2V VIMON 200mV/DIV IMON Step Response RIMON = 2k ON 2VDC BIAS CL = 8pF VCC = 12V TA = 25°C VI = ±200mV VIMON 200mV/DIV VIMON 200mV/DIV 500ns/DIV 2940 G10 250ns/DIV 2940 G11 250ns/DIV 2940 G12 2940f 6 LT2940 TYPICAL PERFORMANCE CHARACTERISTICS Power Supply Rejection Ratio vs Frequency 80 PMON OUTPUT SIGNAL (dBVPK) 0 PMON Input Feedthrough vs Frequency RELATIVE TO ±1VPK RPMON = 5k ON 2VDC BIAS –10 TA = 25°C –20 –30 –40 –50 –60 100 VV = ±2VPK VI = 0mV, dV = 0 VI = ±200mVPK VV = 0V, dI = 0 REJECTION RATIO (dBV) 60 IMON 40 PMON 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 10M 2940 G13 10k 100k 1M 10M FREQUENCY (Hz) 2940 G14 SEE TEST CIRCUITS FOR LOADING CONDITIONS 1k PMON Frequency Response to Voltage Sense 10 RELATIVE PMON VOLTAGE (dBVPK) I-TO-V AMP OUTPUT RELATIVE PMON VOLTAGE (dBVPK) RELATIVE TO DC GAIN 0 10 PMON Frequency Response to Current Sense RELATIVE TO DC GAIN 0 I-TO-V AMP OUTPUT –10 –10 –20 VV = ±2VPK VI = 200mVDC IPMON = ±200μAPK (NOM) TA = 25°C 1k RL = 2k –20 VV = 2VDC VI = ±200mVPK IPMON = ±200μAPK (NOM) TA = 25°C 1k RL = 2k –30 –30 RL = 5k RL = 5k –40 100 10k 100k 1M 10M FREQUENCY (Hz) 2940 G15 SEE TEST CIRCUITS FOR LOADING CONDITIONS –40 100 10k 100k 1M 10M FREQUENCY (Hz) 2940 G16 SEE TEST CIRCUITS FOR LOADING CONDITIONS IMON Frequency Response to Current Sense 10 OPEN COLLECTOR CURRENT (mA) RELATIVE IMON VOLTAGE (dBVPK) RELATIVE TO DC GAIN 0 I-TO-V AMP OUTPUT 25 Open Collector Current vs Open Collector Voltage TA = 25°C OUTPUT PULLING LOW 20 –10 15 VCC = 80V 10 VCC = 6V 5 –20 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 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. 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. 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. 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. 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. 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 VCC GND GIMON = 1000 μA V IMON + – μA KPMON = 500 2 V 5 8 7 V+ V– 4-QUADRANT MULTIPLIER + – PMON 4 CMPOUT 3 CMP+ 1.24V VCC BGAP REF AND UVLC UVLC 1 + – D CLR LE Q CMPOUT 2 9 LATCH LATCHLO THREE-STATE LATCHHI DECODE 2940 BD TEST CIRCUITS Resistor on DC Bias PMON OR IMON RL 2V 2940 TC01 I-to-V Amplifier 12V VOUT RFB 4.99k RC 499Ω VOUT Q1 2N2369 2V 2940 TC02 PMON OR IMON 2940f 9 LT2940 APPLICATIONS INFORMATION Introduction 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’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. VI = VI+ – VI– ±200mV (MAX) 11 10 I+ I– GIMON = 1000 μA V LT2940 IMON μA KPMON = 500 2 V PMON 4 ±200μA FULL-SCALE 5 ±200μA FULL-SCALE Multiplier Operation 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: V V = V V+ – V V– V I = V I+ – V I– (1a) (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 GIMON = 1000 (4) µA V (5) Both the PMON and IMON outputs reach full-scale at ±200μA. 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 + – VV = VV+ – VV – ±8V (MAX) 8 7 V + VV • VI = ±0.4V2 FULL-SCALE + – V– 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 Voltage SENSE INPUT PINS V+, V – PIN VOLTAGE LIMIT 0V to VCC – 3V at VCC ≤ 12V 0V TO 9V at 12V < VCC < 30V 0V to 18V at VCC ≥ 30V Current Power I+, I – V+, V –, I+, I – 4V to 80V* See Above Limits VI = ±200mV VV • VI = ±0.4V2 GIMON = 1000μA /V KPMON = 500μA / V2 IMON PMON IIMON = ±200μA IPMON = ±200μA Sourcing: 0V to VCC – 4.5V at VCC ≤ 7.5V 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. INPUT OPERATING RANGE VV = ±8V SCALING TO OUTPUT MONITOR OUTPUT PINS OUTPUT OPERATING RANGE OUTPUT VOLTAGE COMPLIANCE - 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. 200 IPMON = 200μA 100 VI = VI+ – VI– (mV) 100μA 50μA 25μA 12.5μA 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 (6) 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 = R1 R1 + R2 (7a) (7b) (8a) (8b) (9a) (9b) V I = IIN • kI kI = RSENSE The PMON output current is given by: IPMON = KPMON • VIN • kV • IIN • kI or IPMON = PIN • KPMON • kV • kI 50 25 12.5 0.5 1 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 5 RIMON IIMON VIMON R2 8 R1 7 V+ V– VV = VIN • R1 R1 + R2 kV = R1 R1 + R2 VI = IIN • RSENSE k I = RSENSE + – PMON 4 RPMON IPMON VPMON 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 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 and the final end-to-end scaling is given by: VIMON = IIN • GIMON • kI • RIMON (16) (15) (11) 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 V2 • 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 = IIMON − 1000 μA • VI V • 100 % 200μ A (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. 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 300 II 250 200 150 VOLTAGE SENSE CLIPPED 100 50 VI (mV) 0 –50 –100 –150 –200 –250 III –300 –12 –10 –8 CURRENT SENSE CLIPPED LIMITED BY PMON COMPLIANCE VOLTAGE SENSE CLIPPED I 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 400 CURRENT SENSE CLIPPING I 200 VOLTAGE SENSE CLIPPING IPMON = 200μA 100 VI (mV) 100μA 50μA 25μA (D) (A) GUARANTEED ACCURACY 50 LIMITED BY PMON COMPLIANCE CURRENT SENSE CLIPPED –6 –4 –2 0 VV (V) 2 4 6 8 10 IV 25 (C) GUARANTEED ACCURACY 0.5 1 2 VV (V) 4 8 2940 F05 (B) 12.5 12 16 2940 F04 Figure 4. Multiplier Operating Regions vs Sense Input Voltages. Accuracy Is Derataed in Shaded Areas 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. 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 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 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 RESET C2 10nF GND 2940 F06 R9A 20k I+ LATCH LT2940 I– 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. 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. 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. 100V MAX 30V TO 80V 5mA MAX 36V MAX R14 20k OVP OVERPOWER (OVP) GOES HIGH WHEN LOAD POWER > 40W LATCH CMPOUT CMPOUT CMP+ PMON R3 6.19k R4 13.7k VPMON GND LT2940 R12 3.9k 10% 1/8W VCC I+ RS 150mΩ 1/2W 0A TO 1.3A LOAD I– R2 140k V+ R1 10.0k V– IMON 2940 F07 kV = 1 15 SCALE = 10 W V kI = 150mΩ 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) 0A TO 4A RS 50mΩ 1W 5mA MAX I– R12 3.9k 1/8W VCC LOAD VLOGIC R14 3.9k OVP OVERPOWER (OVP) GOES HIGH WHEN SUPPLY POWER > 120W LATCH CMPOUT CMPOUT CMP+ I+ R2 140k LT2940 V+ R1 10.0k V– GND IMON 2940 TA02 PMON R3 6.19k R4 13.7k VPMON SCALE = 30 W V kV = 1 15 120W FULL-SCALE kI = 50mΩ 12.5W PWM Heat Source RS 200mΩ 3 INPUT 9.5V TO 14.5V + C1 100μF 25V Q3 2N3906 R6 10k R5 10k VCC LATCH I+ LT2940 I– V+ V– Q2 TP0610 R2 102k R1 25.5k D1 1N5819 R7* 7Ω HEATSINK Q = 12.5W CMPOUT CMPOUT CMP+ PMON GND IMON C4 4.7μF R4 15.0k 1 5 kI = 200mΩ 3 tOFF 1.7ms kV = Q1 FDS3672 2940 TA03 * 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 + R3 10k C2 22nF C1 100μF 50V VCC I– LT2940 I+ V+ – R2 102k R1 25.5k D2 27V V V+ R LM334 V– R4 680Ω PMON GND IMON D1 1N457 kV = 1 15 kI = 200mΩ 3 R5 6.8k R6 51Ω R7 3.3k C3 470pF HEATSINK Q = 30W Q1 VN2222 R8 1k R9 10k Q2 TIP129 Q3 D44VH11 R10 100Ω 10A/V R11 100mΩ 2940 TA04 Wide Input Range 10W PWM Heat Source RS 200mΩ 3 22.4V TO 72V + C1 100μF 100V Q3 2N3906 12V R6 10k R5 10k VCC LATCH I+ LT2940 I– V+ – R2 220k R1 13k D2 1N4148 12V Q2 BSS123 CMPOUT CMPOUT CMP+ PMON GND IMON V R7 50Ω 25W HEATSINK Q = 10W D1 MUR1100E D3 1N4148 C2 100nF C4 4.7μF R4 68k 13 233 kI = 200mΩ 3 tOFF 2ms kV = 2940 TA05 Q1 FDS3672 2940f 17 LT2940 TYPICAL APPLICATIONS 8V to 32V, 8W Load RS 200mΩ 8V TO 32V 12V VCC I– LT2940 V+ R1 10k LM334 V– V– I+ R3 2k R2 30k C1 100nF R 12V V+ R7 6.8Ω 10W R5 6.8k R6 10Ω R4 680Ω IMON GND PMON kV = 1 4 D1 1N457 200μA/A CURRENT MONITOR OUTPUT C4 100nF 2940 TA06 kI = 200mΩ Q1 FDB3632 Adjustable 0W to 10W Load Box with UVLO and Thermal Shutdown 10V TO 40V INPUT R2 120k V – V+ 12V R12 12k 1A/V CURRENT MONITOR OUTPUT VCC LATCH LT2940 I+ I– PMON CMPOUT CMPOUT IMON GND CMP+ R1 30k D1 1N4003 R11 33Ω C11 10nF 12V 12V R15 10k R16 10k C13 10nF 0W TO 10W ADJ 10-TURN RS 200mΩ R14 10Ω Q1 FDB3632 Q3 2N3906 R17 100Ω Q4 2N3906 R18 1k REF OA – + R19 10k + – 200mV LT1635 R13 10k ICONTROL = 50mW/μA R3B 91k UVLO R3A 13k kV = 1 5 R4 4.99k Q2 2N3904* kI = 200mΩ TEMP R10 ADJ 500Ω 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 RS1 215Ω RS2 215Ω LOAD+ CHARGER+ R1 121k V– 200mV R2 30k 1% LT1635 Q1 2N3904 12V CYCLON 2V, 4.5AH DT CELL* R12 1k 5% 1W/V R4 ±2.5W MAX 12.4k R5 4.99k VCC PMON I+ I– V+ LT2940 IMON D1 5.1V 1A/V ±1A MAX + REF – GND 2940 TA08 + OA – R6 1k 1% R7 200Ω 1% R8 1k 1% Q2 2N3904 R9 200Ω 1% RS3 200mΩ LOAD– kV = 121 = 0.8 151 kI = 200mΩ *www.hawkerpowersource.com (423) 238-5700 CHARGER– Motor Monitor with Circuit Breaker RS 25mΩ 2 12V + VCC R3 10k RESET LATCH CMPOUT CMPOUT CMP+ IMON GND PMON VIMON 6.5A/V V– I+ LT2940 V+ I– R2A 10k 1% R1 10k 1% R2B 10k 1% VPMON 100W/V C4 100nF C10 100μF 25V MUR120 GE 5BPA34KAA10B 12V, 8A PM FIELD C5 33nF R5 12.4k R4 4.99k 2940 TA09 Q1 FDB3632 1 3 kI = 25mΩ 2 OVERCURRENT TRIP = 8A kV = 2940f 19 LT2940 TYPICAL APPLICATIONS 28V Power to Frequency Converter RS 200mΩ LOAD R2 120k VCC LATCH LT2940 R5, 100k PMON CMPOUT D3 D4 CMPOUT IMON GND CMP+ Q3 LTC1440 D1 10V V+ OUT R9 1M Q1 V– C4 2.2nF GND C6 VCC 100nF VCC I+ I– V+ V– R1A 30k C7 10nF R1B 30k 28V INPUT 10V TO 40V kV = 1 5 kI = 200mΩ PMAX = 10W fOUT = 10W 1000Hz Q2 R6, 100k VCC IN + C5 1μF WIMA IN – D2 R4B 10k R4A 240k 2940 TA10 + – HYST REF CENTRAL SEMI CCLM2700 = 1N4148 OPTO-ISOLATOR = 2N7000 Secondary-Side AC Circuit Breaker T1 12.6VAC SECONDARY RS 200mΩ 3 Q5 VCC LATCH V+ R6 1k D2 1N4001 D3 5.1V C1B 220μF 25V Q6 R7 1k Q7 IMON CMP+ 1A/V 3APK 1.25A TRIP LT2940 V– I+ I– R2 120k R1 30k + C1A 220μF 25V R9 10k Q4 R10 1k RESISTIVE LOAD 2X FDS3732 Q1 VCC R11 10k R12 10k Q2 R0 10Ω D1 1N4001 Q3 CMPOUT CMPOUT + Q8 GND PMON 10W/V 30WPK kV = 30 = 1 150 5 kI = 200mΩ 3 = 2N3906 R3 15k 2940 TA11 R4 15k 2940f 20 LT2940 TYPICAL APPLICATIONS AC Power and Current Monitor T1 12.6VAC SECONDARY LOAD + D1 1N4001 R3 10Ω C1A 220μF 25V RS 200mΩ 3 VCC I+ I– V+ kV = 1 5 kI = 200mΩ 3 + D2 1N4001 C1B 220μF 25V D3 5.1V R6 1k LT2940 V– R1 30k R2 120k GND PMON IMON R4 15k R5 15k 2940 TA12 10W/V ±30WPK 1A/V ±3APK Fully Isolated AC Power and Current Monitor 117V “L” 7A 1 • 500 RS1 RS2 4.99Ω 4.99Ω VCC • T1 VCC R2A 200Ω 1% R1A 68.1Ω LOAD 15V C1 47μF 25V R12 1k R4 4.22k 1kW/ V ±853 WPK VCC I+ I– V+ D2 D4 R6 10k R5 4.99k C12 100nF D1 5.1V 10A/V ±10APK PMON LT2940 IMON V– GND 2940 TA13 •• 10.8V T2 117V C2 100nF R2B R1B 68.1Ω 200Ω 1% R7 10k D3 D5 kV = kI = 68 . 1 + 68 . 1 108 1 • = 200 + 200 + 68 . 1 + 68 . 1 1168 42 . 5 8 4 . 99 + 4 . 99 10 = 500 501 117V “N” ISOLATION BARRIER = 1N4148 T1 = MINNTRONIX 4810966R 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 R = 0.115 TYP 7 0.40 ± 0.10 12 3.00 ± 0.10 (4 SIDES) PIN 1 TOP MARK (SEE NOTE 6) 2.38 ±0.10 1.65 ± 0.10 PIN 1 NOTCH R = 0.20 OR 0.25 × 45° CHAMFER 6 0.200 REF 0.75 ± 0.05 2.25 REF 0.00 – 0.05 0.23 ± 0.05 0.45 BSC (DD12) DFN 0106 REV A 1 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 (.035 0.127 .005) 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 0.42 0.038 (.0165 .0015) TYP 0.65 (.0256) BSC 4.039 0.102 (.159 .004) (NOTE 3) 12 11 10 9 8 7 RECOMMENDED SOLDER PAD LAYOUT 0.406 0.076 (.016 .003) REF 0.254 (.010) GAUGE PLANE DETAIL “A” 0 – 6 TYP 4.90 0.152 (.193 .006) 3.00 0.102 (.118 .004) (NOTE 4) 0.53 0.152 (.021 .006) DETAIL “A” 0.18 (.007) SEATING PLANE 123456 1.10 (.043) MAX 0.86 (.034) REF 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 0.22 – 0.38 (.009 – .015) TYP 0.650 (.0256) BSC 0.1016 (.004 0.0508 .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 5V IN OUT R17 309k R16 100k R15 24.9k C19 0.1μF V+ C17 0.47μF 5V I+ RS 100mΩ S1B S2B S3B S4B LTC6943 V+ S1A S2A S3A S4A COSC CA+ CA– V– SHA 5V R18 49.9k CMPOUT PMON CT 2.2μF Q1 2N7002 GND IMON RESET VSS RESET 2940 TA14 0A TO 2A LOAD (80W MAX) R2 215k V+ CB+ CB – SHDN C16 LT3014 1μF ADJ GND VCC I– R14 20.0k – + LTC6702 V– CMP+ LT2940 CMPOUT LATCH C1 1μF R1 11.3k C18 0.1μF C20 0.1μF kV = 1 20 R13 4.99k – + GND VDD Q 12V 1024 COUNTS = 1 WATT-HOUR kI = 100mΩ CD4040 RELATED PARTS PART NUMBER LTC1966 LTC1968 LTC6101/ LTC6101HV LTC6104 LTC6106 LTC4151 LTC4215 LT4256-1/ LT4256-2 LTC4260 LTC4261 DESCRIPTION Precision Micropower Delta-Sigma RMS-to-DC Converter Precision Wide Bandwidth RMS-to-DC Converter High Voltage, High Side, Precision Current Sense Amplifiers Bidirectional High Side, Precision Current Sense Amplifier Low Cost, High Side Precision Current Sense Amplifier High Voltage I2C Current and Voltage Monitor Positive Hot Swap Controller with ADC and I2C Positive 48V Hot Swap Controllers with OpenCircuit Detect Positive High Voltage Hot Swap Controller With ADC and I2C Monitoring Negative Voltage Hot Swap Controller With ADC and I2C Monitoring COMMENTS 2.7V to 12V Supply Voltage, 170μA Supply Current 4.5V to 6V Supply Voltage, 500kHz 3dB-Error BW 4V to 60V/ 5V to 100V, Gain Configurable, SOT-23 4V to 60V, Gain Configurable, 8-Pin MSOP 2.7V to 36V, Gain Configurable, SOT23 Wide Operating Range: 7V to 80V 8-Bit ADC Monitoring Current and Voltages, Supplies from 2.9V to 15V Foldback Current Limiting, Open-Circuit and Overcurrent Fault Output, Up to 80V Supply Wide Operating Range: 8.5V to 80V Floating Topology Allows Very High Voltage Operation 2940f 24 Linear Technology Corporation (408) 432-1900 ● FAX: (408) 434-0507 ● LT 1109 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 www.linear.com © LINEAR TECHNOLOGY CORPORATION 2009