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LT2940 Power and Current Monitor FEATURES
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DESCRIPTION
The LT(R)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 x 3mm) and 12-Lead MSOP Packages
APPLICATIONS
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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 20m 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 = 20m 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
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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................................................... 0C to 70C LT2940I ................................................-40C to 85C Storage Temperature Range...................-65C to 150C Lead Temperature (Soldering, 10 sec) MSOP Package ................................................. 300C
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 = 125C, JA = 43C/W EXPOSED PAD (PIN 13) PCB GND CONNECTION OPTIONAL
MS PACKAGE 12-LEAD PLASTIC MSOP TJMAX = 125C, JA = 135C/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 0C to 70C -40C to 85C 0C to 70C -40C to 85C
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/
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LT2940 ELECTRICAL CHARACTERISTICS
SYMBOL Supply VCC ICC VCC(UVLC) VCC(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 IVSEN 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 IISEN = 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 = 25C. 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 = +200A, IIMON = +200A (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 IVSEN = IV+ - IV -
-100 50
100 150
nA nA
V V+ = V V -
l
4 200
80
V mV
VI(CL) IISEN IISEN
l l l
225 75 100 200 125 800
mV A nA
Power Monitor (Note 2) IPMON(OR) IPMON(CAPA)
l l
200 900 1200
A A
l
-240
-1200
A
l
-800
-1200
A
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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 = 25C. All specifications apply at 6V VCC 80V, unless otherwise specified.
CONDITIONS VCC 12V, IPMON 0A 12V < VCC < 30V, IPMON 0A VCC 30V, IPMON 0A VCC 12V, IPMON < 0A 12V < VCC < 30V, IPMON < 0A VCC 30V, IPMON < 0A
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 A /V2 mV mV A MHz A
EPMON
Power Monitor Output Total Error (Note 4)
|V V * V I | 0.4V2 |V V * V I | 0.4V2, 25C < TA 85C |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 0A 12V < VCC < 30V, IIMON 0A VCC 30V, IIMON 0A VCC 12V, IIMON < 0A 12V < VCC < 30V, IPMON < 0A VCC 30V, IPMON < 0A EIMON Current Monitor Output Total Error (Note 4) |V I | 200mV, 25C TA 85C |V I | 200mV, LT2940C |V I | 200mV, LT2940I 200mV < |V I | 225mV GIMON VI(OSI) BWIMON Comparator VCMP(TH) VCMP(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 A /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
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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 = 25C. 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 A V A s V V V A A A
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 200A. 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 (A) 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 = 25C -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
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LT2940 TYPICAL PERFORMANCE CHARACTERISTICS
PMON Current vs Power Sense Product
1500 1000 500 IPMON (A) 0 -500 -1000 -1500 -4 -2 0 VV * VI (V2) 2 4
2940 G04
PMON and IMON Voltage Compliance
300 200 OUTPUT CURRENT (A) 100 0 -100 -200 -300 -5 0 5 10 15 OUTPUT VOLTAGE (V) I = -200A VCC = 6V VCC = 12V VCC = 30V 20
2940 G05
Supply Current vs Supply Voltage
3.6 IPMON = 200A IIMON = 200A
VCC 15V VV = 40 * VI
TA = 25C I = 200A
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 = 0A IIMON = 0A
IPMON = -200A IIMON = -200A 60 VCC (V) 80 100
2940 G06
IMON Current vs Current Sense Voltage
300 200 1 100 EIMON (%FS) IIMON (A) 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 = 25C VV = 2V VI = 200mV
PMON Step Response
RPMON = 2k ON 2VDC BIAS CL = 8pF VCC = 12V TA = 25C VI = 200mV VV = 2V VIMON 200mV/DIV
IMON Step Response
RIMON = 2k ON 2VDC BIAS CL = 8pF VCC = 12V TA = 25C VI = 200mV
VIMON 200mV/DIV
VIMON 200mV/DIV
500ns/DIV
2940 G10
250ns/DIV
2940 G11
250ns/DIV
2940 G12
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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 = 25C -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 = 25C 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 = 200APK (NOM) TA = 25C 1k
RL = 2k
-20 VV = 2VDC VI = 200mVPK IPMON = 200APK (NOM) TA = 25C 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 = 25C OUTPUT PULLING LOW
20
-10
15 VCC = 80V 10 VCC = 6V 5
-20
RL = 2k
-30 V = 200mV I PK IIMON = 200APK (NOM) RL = 5k TA = 25C -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
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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 200A 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 200A 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 10A 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 100A of bias current in addition to having an effective 5k 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.
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LT2940 FUNCTIONAL BLOCK DIAGRAM
11 10 I+ I- 12 6 VCC GND GIMON = 1000 A V IMON
+ -
A 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 499 VOUT Q1 2N2369 2V
2940 TC02
PMON OR IMON
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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 A V LT2940 IMON A KPMON = 500 2 V PMON 4 200A FULL-SCALE 5 200A 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 A 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) A V (5) Both the PMON and IMON outputs reach full-scale at 200A. 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
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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 = 1000A /V KPMON = 500A / V2 IMON PMON IIMON = 200A IPMON = 200A 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 200A 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 = 200A 100 VI = VI+ - VI- (mV) 100A 50A 25A 12.5A
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
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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 200A, 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 200A 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: A * ( VV * VI ) IPMON - 500 V2 * 100 % EPMON = 200A (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 A * VI V * 100 % 200 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 = 200A. 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 = 200A 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 = 50A 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 = 25A 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 = 200A 100 VI (mV) 100A 50A 25A (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 = 100A 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 10A 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 150m 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 = 150m
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 50m 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 = 50m
12.5W PWM Heat Source
RS 200m 3 INPUT 9.5V TO 14.5V
+
C1 100F 25V Q3 2N3906
R6 10k R5 10k
VCC LATCH
I+ LT2940
I- V+ V-
Q2 TP0610 R2 102k R1 25.5k
D1 1N5819
R7* 7
HEATSINK Q = 12.5W
CMPOUT CMPOUT CMP+ PMON GND IMON
C4 4.7F
R4 15.0k
1 5 kI = 200m 3 tOFF 1.7ms kV = Q1 FDS3672
2940 TA03
* SEVEN 50, 5W RESISTORS IN PARALLEL. MULTIPLE UNITS FACILITATE SPREADING HEAT.
2940f
16
LT2940 TYPICAL APPLICATIONS
30W Linear Heat Source
RS 200m 3 10V TO 40V
+
R3 10k C2 22nF
C1 100F 50V VCC
I- LT2940
I+ V+
-
R2 102k R1 25.5k
D2 27V
V V+ R LM334 V- R4 680 PMON GND IMON
D1 1N457 kV = 1 15 kI = 200m 3
R5 6.8k
R6 51 R7 3.3k C3 470pF
HEATSINK Q = 30W Q1 VN2222 R8 1k R9 10k
Q2 TIP129 Q3 D44VH11 R10 100 10A/V R11 100m
2940 TA04
Wide Input Range 10W PWM Heat Source
RS 200m 3 22.4V TO 72V
+
C1 100F 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 50 25W
HEATSINK Q = 10W
D1 MUR1100E
D3 1N4148 C2 100nF
C4 4.7F
R4 68k
13 233 kI = 200m 3 tOFF 2ms kV =
2940 TA05
Q1 FDS3672
2940f
17
LT2940 TYPICAL APPLICATIONS
8V to 32V, 8W Load
RS 200m 8V TO 32V 12V VCC I- LT2940 V+ R1 10k LM334 V- V- I+ R3 2k R2 30k C1 100nF R 12V
V+
R7 6.8 10W R5 6.8k R6 10
R4 680
IMON GND PMON kV = 1 4 D1 1N457 200A/A CURRENT MONITOR OUTPUT C4 100nF
2940 TA06
kI = 200m
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 33 C11 10nF
12V 12V R15 10k R16 10k C13 10nF 0W TO 10W ADJ 10-TURN
RS 200m R14 10 Q1 FDB3632
Q3 2N3906
R17 100 Q4 2N3906 R18 1k
REF
OA
- +
R19 10k
+ -
200mV
LT1635
R13 10k
ICONTROL = 50mW/A R3B 91k UVLO R3A 13k
kV =
1 5
R4 4.99k Q2 2N3904*
kI = 200m
TEMP R10 ADJ 500
2940 TA07
*THERMAL SHUTDOWN; COUPLE TO Q1's HEAT SINK
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18
LT2940 TYPICAL APPLICATIONS
1-Cell Monitor with Bottom-Side Sense
12V C1 100nF RS1 215 RS2 215 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 200 1% R8 1k 1%
Q2 2N3904 R9 200 1% RS3 200m LOAD-
kV = 121 = 0.8 151 kI = 200m
*www.hawkerpowersource.com (423) 238-5700
CHARGER-
Motor Monitor with Circuit Breaker
RS 25m 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 100F 25V MUR120
GE 5BPA34KAA10B 12V, 8A PM FIELD
C5 33nF
R5 12.4k
R4 4.99k
2940 TA09
Q1 FDB3632
1 3 kI = 25m 2 OVERCURRENT TRIP = 8A kV =
2940f
19
LT2940 TYPICAL APPLICATIONS
28V Power to Frequency Converter
RS 200m 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 = 200m PMAX = 10W fOUT = 10W 1000Hz
Q2
R6, 100k VCC
IN + C5 1F 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 200m 3 Q5 VCC LATCH V+ R6 1k D2 1N4001 D3 5.1V C1B 220F 25V Q6 R7 1k Q7 IMON CMP+ 1A/V 3APK 1.25A TRIP LT2940 V- I+ I-
R2 120k R1 30k
+
C1A 220F 25V
R9 10k Q4 R10 1k
RESISTIVE LOAD 2X FDS3732 Q1 VCC R11 10k R12 10k Q2
R0 10
D1 1N4001
Q3
CMPOUT CMPOUT
+
Q8
GND PMON 10W/V 30WPK kV = 30 = 1 150 5 kI = 200m 3 = 2N3906
R3 15k
2940 TA11
R4 15k
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20
LT2940 TYPICAL APPLICATIONS
AC Power and Current Monitor
T1 12.6VAC SECONDARY
LOAD
+
D1 1N4001 R3 10
C1A 220F 25V
RS 200m 3
VCC
I+
I- V+ kV = 1 5 kI = 200m 3
+
D2 1N4001
C1B 220F 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 4.99 4.99 VCC
*
T1
VCC R2A 200 1% R1A 68.1 LOAD
15V C1 47F 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 68.1 200 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 x 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 x 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 O)
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 O
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 0.1F V+ C17 0.47F 5V I+ RS 100m S1B S2B S3B S4B LTC6943 V+ S1A S2A S3A S4A COSC CA+ CA- V- SHA 5V R18 49.9k CMPOUT PMON CT 2.2F Q1 2N7002 GND IMON RESET VSS RESET
2940 TA14
0A TO 2A
LOAD (80W MAX) R2 215k
V+ CB+ CB -
SHDN C16 LT3014 1F ADJ GND
VCC
I-
R14 20.0k
- +
LTC6702
V- CMP+ LT2940 CMPOUT LATCH
C1 1F
R1 11.3k
C18 0.1F
C20 0.1F kV = 1 20
R13 4.99k
- +
GND
VDD Q
12V
1024 COUNTS = 1 WATT-HOUR
kI = 100m
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, 170A 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
(c) LINEAR TECHNOLOGY CORPORATION 2009

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