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LT6105 Precision, Extended Input Range Current Sense Amplifier FEATURES
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DESCRIPTION
The LT(R)6105 is a micropower, precision current sense amplifier with a very wide input common mode range. The LT6105 monitors unidirectional current via the voltage across an external sense resistor. The input common mode range extends from -0.3V to 44V, with respect to the negative supply voltage (V -). This allows the LT6105 to operate as a high side current sense monitor or a low side current sense monitor. It also allows the LT6105 to monitor current on a negative supply voltage, as well as continuously monitor a battery from full charge to depletion. The inputs of LT6105 can withstand differential voltages up to 44V, which makes it ideal for monitoring a fuse or MOSFET switch. Gain is configured with external resistors from 1V/V to 100V/V. The input common mode rejection and power supply rejection are in excess of 100dB and the input offset voltage is less than 300V. A minimum slew rate of 2V/s ensures fast response to unexpected current changes. The LT6105 can operate from an independent power supply of 2.85V to 36V and draws only 150A. When V+ is powered down, the sense pins are biased off. This prevents loading of the monitored circuit, irrespective of the sense voltage. The LT6105 is available in a 6-lead DFN and 8-lead MSOP package.
, LT, LTC, LTM and Over-the-Top are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
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Very Wide, Over-the-Top(R), Input Common Mode Range - Extends 44V Above V - (Independent of V +) - Extends -0.3V Below V - Wide Power Supply Range: 2.85V to 36V Input Offset Voltage: 300V Maximum Gain Accuracy: 1% Max Gain Configurable with External Resistors Operating Current: 150A Slew Rate: 2V/s Sense Input Current When Powered Down: 1nA Full-Scale Output Current: 1mA Minimum Operating Temperature Range -40C to 125C Available in 2mm x 3mm DFN and 8-Lead MSOP Packages
APPLICATIONS
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High Side or Low Side Current Sensing Current Monitoring on Positive or Negative Supply Voltages Battery Monitoring Fuse/MOSFET Monitoring Automotive Power Management Portable Test/Measurement Systems
TYPICAL APPLICATION
Gain of 50 Current Sense Amplifier
SOURCE -0.3V TO 44V RIN2 VS+ 100 0.02 RIN1 100 LT6105 GAIN ERROR (%) +IN 4
Gain Error vs Input Voltage
V+ = 12V 3 VSENSE = 50mV RIN = 100 A V = 50V 2 1 0 -1 -2 -3
6105 TA01
TA = - 40C TA = 25C
+ -
V+
VOUT
VOUT = 1V/A ROUT 4.99k
-IN
VS-
TA = 125C
TA = 85C
V-
TO LOAD
2.85V TO 36V
VOUT = VS + - VS - *
(
)
ROUT R ; A V = OUT ; RIN1 = RIN 2 = RIN RIN RIN
-4 0 5 10 15 20 25 30 35 VS+ INPUT VOLTAGE (V) 40 45
6105f
6105 TA01b
1
LT6105 ABSOLUTE MAXIMUM RATINGS
(Notes 1, 2)
Differential Input Voltage (+IN - -IN) .....................44V Input Voltage V(+IN, -IN) to V - ................ -9.5V to 44V Total V+ Supply Voltage from V - ...............................36V Output Voltage ......................................V - to (V - + 36V) Output Short-Circuit Duration (Note 3) ............ Indefinite Operating Temperature Range (Note 4) LT6105C...............................................-40C to 85C LT6105I ................................................-40C to 85C LT6105H ............................................-40C to 125C
Specified Temperature Range (Note 5) LT6105C................................................... 0C to 70C LT6105I ................................................-40C to 85C LT6105H ............................................-40C to 125C Maximum Junction Temperature........................... 150C Storage Temperature Range...................-65C to 150C Lead Temperature (Soldering, 10 sec) MSOP ............................................................... 300C
PIN CONFIGURATION
TOP VIEW -IN 1 V+ 2 V- 3 7 6 +IN 5 NC 4 VOUT TOP VIEW -IN V+ NC V- 1 2 3 4 8 7 6 5 +IN NC NC VOUT
DCB PACKAGE 6-LEAD (2mm x 3mm) PLASTIC DFN TJMAX = 150C, JA = 64C/W EXPOSED PAD (PIN 7) CONNECTED TO V - (PIN 3)
MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150C, JA = 250C/W
ORDER INFORMATION
LEAD FREE FINISH LT6105CDCB#TRMPBF LT6105IDCB#TRMPBF LT6105HDCB#TRMPBF LT6105CMS8#PBF LT6105IMS8#PBF LT6105HMS8#PBF TAPE AND REEL LT6105CDCB#TRPBF LT6105IDCB#TRPBF LT6105HDCB#TRPBF LT6105CMS8#TRPBF LT6105IMS8#TRPBF LT6105HMS8#TRPBF PART MARKING* LCTF LCTF LCTF LTCTD LTCTD LTCTD PACKAGE DESCRIPTION 6-Lead (2mm x 3mm) Plastic DFN 6-Lead (2mm x 3mm) Plastic DFN 6-Lead (2mm x 3mm) Plastic DFN 8-Lead Plastic MS8 8-Lead Plastic MS8 8-Lead Plastic MS8 SPECIFIED TEMPERATURE RANGE 0C to 70C -40C to 85C -40C to 125C 0C to 70C -40C to 85C -40C to 125C
TRM = 500 pieces. *Temperature grades are identified by a label on the shipping container. Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for parts specified with wider operating temperature ranges. 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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LT6105 ELECTRICAL CHARACTERISTICS
SYMBOL VS+, VS- A V Error PARAMETER Input Voltage Range Voltage Gain Error (Note 6)
The l denotes the specifications which apply over the temperature range 0C < TA < 70C (LT6105C), otherwise specifications are at TA = 25C. V+ = 12V, V - = 0V, VS+ = 12V (see Figure 1), RIN1 = RIN2 = 100, ROUT = 5k (A V = 50), VSENSE = VS+ - VS-, unless otherwise specified. (Note 5)
CONDITIONS Guaranteed by CMRR VSENSE = 25mV to 75mV, VS+ = 12V VSENSE = 25mV to 75mV, VS+ = 0V
l l l l l l l
MIN -0.3 -0.1 -1 -1.3 -2.5 -0.3 -0.6 -0.4 -0.7 -1 -1.3 100 95 94 90 2.85 98 94 98 94
TYP
MAX 44 44
UNITS V V % % % mV mV mV mV mV mV V/C dB dB dB dB
0.1
1 1.3 2.5
VOS
Input Offset Voltage MS8 Package Input Offset Voltage DCB Package Input Offset Voltage
VSENSE = 5mV VSENSE = 5mV VSENSE = 5mV, VS+ = 0V
-0.1 -0.1 -0.3 0.5 120
0.3 0.6 0.4 0.7 1 1.3
VOS /T CMRR
Temperature Coefficient of VOS Input Common Mode Rejection Ratio VSENSE = 5mV, VS
+ = 2.8V to 44V
l l l l l l l l l l l l l l l l
VSENSE = 5mV, VS+ = -0.3V to 44V VSENSE = 5mV, VS+ = -0.1V to 44V V+ PSRR Power Supply Voltage Range Power Supply Rejection Ratio Guaranteed by PSRR VSENSE = 5mV, VS
+ = 12V, V + = 2.85V to 36V
36 120 120 15 -0.05 0.05 0.005 0.03 200 240 1.25 25 0.5 1 300 350 35 1.5
V dB dB dB dB A A A A A A A mV V mA mA
VSENSE = 5mV, VS+ = 0V, V + = 2.85V to 36V I(+IN), I(-IN) I(+IN) - I(-IN) I(+IN) + I(-IN) IS VO(MIN) VO(MAX) IOUT ISC BW tS tr SR VREV Input Current Input Offset Current Input Current (Power-Down) V + Supply Current Minimum Output Voltage Output High (Referred to V+) Maximum Output Current Short-Circuit Output Current -3dB Bandwidth Input Step Response (Note 7) Slew Rate (Note 8) Reverse Input Voltage (Referred to V -) VSENSE = 0V, VS+ = 3V VSENSE = 0V, VS+ = 0V VSENSE = 0V, VS+ = 3V VSENSE = 0V, VS+ = 0V V + = 0V, VS+ = 44V, VSENSE = 0V VSENSE = 0V, VS+ = 3V, V+ = 2.85V VSENSE = 0V, VS+ = 3V, V+ = 36V VSENSE = 0mV, VS+ = 44V, V+ = 36V VSENSE = 120mV, A V = 100, RL = 10k Guaranteed by VO(MAX) VS+ = 44V, VS- = 0V, ROUT = 0 VSENSE = 50mV, A V = 10V/V VSENSE = 5mV to 100mV VSENSE = 5mV to 150mV, A V = 50V/V, RIN = 400 I(+IN) + I(-IN) = -5mA
1 1.5 100 5 3 1.75 2.25 -12
kHz s s V/s V
Output Settling to 1% of Final Value VSENSE = 5mV to 100mV
l
-9.5
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LT6105 ELECTRICAL CHARACTERISTICS
SYMBOL VS+, VS- A V Error PARAMETER Input Voltage Range Voltage Gain Error (Note 6)
The l denotes the specifications which apply over the temperature range -40C < TA < 85C (LT6105I), otherwise specifications are at TA = 25C. V+ = 12V, V - = 0V, VS+ = 12V (see Figure 1), RIN1 = RIN2 = 100, ROUT = 5k (A V = 50), VSENSE = VS+ - VS-, unless otherwise specified. (Note 5)
CONDITIONS Guaranteed by CMRR VSENSE = 25mV to 75mV, VS+ = 12V VSENSE = 25mV to 75mV, VS+ = 0V VOS Input Offset Voltage MS8 Package Input Offset Voltage DCB Package Input Offset Voltage VOS /T CMRR Temperature Coefficient of VOS Input Common Mode Rejection Ratio VSENSE = 5mV, VS+ = 2.8V to 44V VSENSE = 5mV, VS+ = -0.3V to 44V VSENSE = 5mV, VS+ = -0.1V to 44V V+ PSRR Power Supply Voltage Range Power Supply Rejection Ratio Guaranteed by PSRR VSENSE = 5mV, VS+ = 12V, V + = 2.85V to 36V VSENSE = 5mV, VS+ = 0V, V + = 2.85V to 36V I(+IN), I(-IN) I(+IN) - I(-IN) I(+IN) + I(-IN) IS VO(MIN) VO(MAX) IOUT ISC BW tS tr SR VREV Input Current Input Offset Current Input Current (Power-Down) V + Supply Current Minimum Output Voltage Output High (Referred to V+) Maximum Output Current Short-Circuit Output Current -3dB Bandwidth Input Step Response (Note 7) Slew Rate (Note 8) Reverse Input Voltage (Referred to V -) VSENSE = 0V, VS+ = 3V VSENSE = 0V, VS+ = 0V VSENSE = 0V, VS+ = 3V VSENSE = 0V, VS+ = 0V V + = 0V, VS+ = 44V, VSENSE = 0V VSENSE = 0V, VS+ = 3V, V+ = 2.85V VSENSE = 0V, VS+ = 3V, V+ = 36V VSENSE = 0mV, VS+ = 44V, V+ = 36V VSENSE = 120mV, A V = 100, RL = 10k Guaranteed by VO(MAX) VS+ = 44V, VS- = 0V, ROUT = 0 VSENSE = 50mV, A V = 10V/V VSENSE = 5mV to 100mV VSENSE = 5mV to 150mV, A V = 50V/V, RIN = 400 I(+IN) + I(-IN) = -5mA
l l l l l l l l l l l l l l l l l l l l l l l l
MIN -0.3 -0.3 -1 -1.4 -3 -0.3 -0.65 -0.4 -0.75 -1 -1.4 100 95 94 90 2.85 98 94 98 94
TYP
MAX 44 44
UNITS V V % % % mV mV mV mV mV mV V/C dB dB dB dB
0.1
1 1.4 3
VSENSE = 5mV VSENSE = 5mV VSENSE = 5mV, VS+ = 0V
-0.1 -0.1 -0.3 0.5 120
0.3 0.65 0.4 0.75 1 1.4
36 120 120 16 -0.05 0.08 0.01 0.035 200 250 1.27 27 0.6 1 325 375 40 1.6
V dB dB dB dB A A A A A A A mV V mA mA
1 1.5 100 5 3 1.75 -9.25 2.25 -12
kHz s s V/s V
Output Settling to 1% of Final Value VSENSE = 5mV to 100mV
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LT6105 ELECTRICAL CHARACTERISTICS
SYMBOL VS+, VS- A V Error PARAMETER Input Voltage Range Voltage Gain Error (Note 6)
The l denotes the specifications which apply over the temperature range -40C < TA < 125C (LT6105H), otherwise specifications are at TA = 25C. V+ = 12V, V - = 0V, VS+ = 12V (see Figure 1), RIN1 = RIN2 = 100, ROUT = 5k (A V = 50), VSENSE = VS+ - VS-, unless otherwise specified. (Note 5)
CONDITIONS Guaranteed by CMRR VSENSE = 25mV to 75mV, VS+ = 12V VSENSE = 25mV to 75mV, VS+ = 0V VOS Input Offset Voltage MS8 Package Input Offset Voltage DCB Package Input Offset Voltage VOS /T CMRR Temperature Coefficient of VOS Input Common Mode Rejection Ratio VSENSE = 5mV, VS
+ = 2.8V to 44V
MIN
l l l l l l l l l l l l l l l l l l l l l l l
TYP
MAX 44 44
UNITS V V % % % mV mV mV mV mV mV V/C dB dB dB dB
-0.3 -0.1 -1 -1.5 -3.25 -0.3 -0.8 -0.4 -0.9 -1 -1.6 100 95 94 80 2.85 98 94 98 94 120 120 18 -0.05 0.35 0.1 0.5 240 300 1.3 1 1.5 100 5 3 1.75 2.25 -12 -0.1 -0.1 -0.3 0.5 120 0.1
1 1.5 3.25 0.3 0.8 0.4 0.9 1 1.6
VSENSE = 5mV VSENSE = 5mV VSENSE = 5mV, VS+ = 0V
VSENSE = 5mV, VS+ = -0.3V to 44V VSENSE = 5mV, VS+ = -0.1V to 44V V+ PSRR Power Supply Voltage Range Power Supply Rejection Ratio Guaranteed by PSRR VSENSE = 5mV, VS
+ = 12V, V + = 2.85V to 36V
36
V dB dB dB dB
VSENSE = 5mV, VS+ = 0V, V + = 2.85V to 36V I(+IN), I(-IN) I(+IN) - I(-IN) I(+IN) + I(-IN) IS VO(MIN) VO(MAX) IOUT ISC BW tS tr SR VREV Input Current Input Offset Current Input Current (Power-Down) V + Supply Current Minimum Output Voltage Output High (Referred to V+) Maximum Output Current Short-Circuit Output Current -3dB Bandwidth Input Step Response (Note 7) Slew Rate (Note 8) Reverse Input Voltage (Referred to V -) VSENSE = 0V, VS+ = 3V VSENSE = 0V, VS+ = 0V VSENSE = 0V, VS+ = 3V VSENSE = 0V, VS+ = 0V V + = 0V, VS+ = 44V, VSENSE = 0V VSENSE = 0V, VS+ = 3V, V+ = 2.85V VSENSE = 0V, VS+ = 3V, V+ = 36V VSENSE = 0mV, VS+ = 44V, V+ = 36V VSENSE = 120mV, A V = 100, RL = 10k Guaranteed by VO(MAX) VS+ = 44V, VS- = 0V, ROUT = 0 VSENSE = 50mV, A V = 10V/V VSENSE = 5mV to 100mV VSENSE = 5mV to 150mV, A V = 50V/V, RIN = 400 I(+IN) + I(-IN) = -5mA
30 0.8 2.5 350 450 45 1.7
A A A A A A A mV V mA mA kHz s s V/s V
Output Settling to 1% of Final Value VSENSE = 5mV to 100mV
l
-9
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LT6105 ELECTRICAL CHARACTERISTICS
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: ESD (Electrostatic Discharge) sensitive devices. Extensive use of ESD protection devices are used internal to the LT6105, however, high electrostatic discharge can damage or degrade the device. Use proper ESD handling precautions. Note 3: A heat sink may be required to keep the junction temperature below absolute maximum ratings. Note 4: The LT6105C/LT6105I are guaranteed functional over the operating temperature range of -40C to 85C. The LT6105H is guaranteed functional over the operating temperature range of -40C to 125C. Note 5: The LT6105C is guaranteed to meet specified performance from 0C to 70C. The LT6105C is designed, characterized and expected to meet specified performance from -40C to 85C but is not tested or QA sampled at these temperatures. The LT6105I is guaranteed to meet specified performance from -40C to 85C. The LT6105H is guaranteed to meet specified performance from -40C to 125C. Note 6: 0.01% tolerance external resistors are used. Note 7: tr is measured from the input to the 2.5V point on the 5V output. Note 8: Slew rate is measured on the output between 1V and 5V.
TYPICAL PERFORMANCE CHARACTERISTICS
Input Offset Voltage vs Temperature, VS+ = 12V
400 V+ = 12V 300 VSENSE = 5mV TYPICAL UNITS 200 100 0 -100 -200 -300 -400 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
6105 G01
Input Offset Voltage vs Temperature, VS+ = 0V
1000 V+ = 12V 800 VSENSE = 5mV TYPICAL UNITS 600 400 200 0 -200 -400 -600 -800 -1000 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
6105 G02
Input Offset Voltage vs Input Voltage
0.80 V+ = 12V 0.60 VSENSE = 5mV A V = 50V/V 0.40 0.20 0 -0.20 -0.40 -0.60 -0.80 -1.00 0 5 10 15 20 25 30 35 VS+ INPUT VOLTAGE (V) 40 45 TA = 85C TA = - 40C TA = 125C
INPUT OFFSET VOLTAGE (mV)
INPUT OFFSET VOLTAGE (V)
INPUT OFFSET VOLTAGE (V)
TA = 25C
6105 G03
Input Offset Voltage vs Supply Voltage, VS+ = 12V
0.8 0.6 INPUT OFFSET VOLTAGE (mV) INPUT OFFSET VOLTAGE (mV) 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 0 5 10 15 20 25 30 35 40
6105 G04
Input Offset Voltage vs Supply Voltage, VS+ = 0V
0.2 0.0 PERCENT OF UNITS (%) 25 30 35 40
6105 G05
Gain Error Distribution, VS+ = 12V
40 V+ = 12V 35 VSENSE = 50mV RIN = 100 A = 50V/V 30 V 500 SAMPLES 25 20 15 10 5
VSENSE = 5mV
VSENSE = 5mV
-0.2 -0.4 -0.6 -0.8 -1.0 -1.2 -1.4 0 5 10 15 20 TA = - 40C TA = 125C TA = 25C TA = 85C
TA = 25C TA = -40C TA = 85C TA = 125C
V+ SUPPLY VOLTAGE (V)
V+ SUPPLY VOLTAGE (V)
0 -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 0.3 0.4 0.5 GAIN ERROR (%)
6105 G06
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LT6105 TYPICAL PERFORMANCE CHARACTERISTICS
Gain Error Distribution, VS+ = 0V
45 40 PERCENT OF UNITS (%) 35 30 25 20 15 10 5 0 -2.3 -2.2 -2.1 -2.0 -1.9 -1.8 -1.7 -1.6 -1.5 -1.4 GAIN ERROR (%)
6105 G07
Gain Error vs Input Voltage
4 V+ = 12V VSENSE = 50mV 3 RIN = 100 A V = 50V 2 GAIN ERROR (%) 1 0 -1 -2 -3 -4 0 5 10 15 20 25 30 35 VS+ INPUT VOLTAGE (V) 40 45 TA = 125C TA = 85C GAIN ERROR (%) TA = - 40C TA = 25C
Gain Error vs Temperature, VS+ = 12V
0.5 V+ = 12V 0.4 VSENSE = 50mV RIN = 100 0.3 A = 50V/V V 0.2 0.1 0.0 -0.1 -0.2 -0.3 -0.4 -0.5 -50 -25 0 25 50 75 TEMPERATURE (C) 100 125
V+ = 12V VSENSE = 50mV RIN = 100 AV = 50V/V 500 SAMPLES
6105 G08
6105 G09
Gain Error vs Temperature, VS+ = 0V
0 -0.4 -0.8 GAIN ERROR (%) -1.2 -1.6 -2.0 -2.4 -2.8 -3.2 -3.6 -4.0 -50 -25 0 25 50 75 TEMPERATURE (C) 100 125 V+ = 12V VSENSE = 50mV RIN = 100 AV = 50V/V GAIN ERROR (%) 6
Gain Error vs Output Resistance
VIN = 12V 5V SENSE = 50mV 4 RIN = 100 3 AV = ROUT/RIN 2 1 0 -1 -2 -3 -4 -5 -6 0 4000 2000 6000 8000 ROUT OUTPUT RESISTANCE () 10000
6105 G11
Input Referred Voltage Error vs VSENSE, VS+ = 12V
2 INPUT REFERRED ERROR (mV) V+ = 12V RIN = 100 AV = 50V/V TA = 85C TA = 125C 0 TA = - 40C -1 TA = 25C
1
VS+ = 12V VS+ = 0V
-2 0 20 40 60 80 VSENSE (mV) 100 120
6105 G10
6105 G12
Input Referred Voltage Error vs VSENSE, VS+ = 0V
5.0 V+ = 12V 4.0 RIN = 100 AV = 50V/V 3.0 2.0 1.0 0.0 -1.0 -2.0 -3.0 -4.0 -5.0 0 20 40 60 80 VSENSE (mV) 100 120 TA = 125C TA = 85C TA = - 40C TA = 25C 100.00 10.00 INPUT BIAS CURRENT (A) 1.00 0.1 0.01 0 -0.01 -0.10 -1.00 -10.00 -100.00
Input Bias Current vs Input Voltage
V+ = 3V VSENSE = 0V RIN = 100 INPUT CURRENT (mA) TA = 125C TA = 85C TA = 25C TA = - 40C 2.0
Input Current vs Input Voltage, VSENSE = 50mV
V+ = 12V RIN = 100 1.5 A V = 50V/V I(+IN) 0.5 I(-IN) 0.0 -0.5 -1.0 -1.5 -2.0
INPUT REFERRED ERROR (mV)
1.0
0
0.5
1.5 2 2.5 1 VS+ INPUT VOLTAGE (V)
6105 G14
3
0
5
10
15 20 25 30 35 VS+ INPUT VOLTAGE (V)
40
45
6105 G13
6105 G15
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LT6105 TYPICAL PERFORMANCE CHARACTERISTICS
Input Current (V+ Powered Down) vs Input Voltage
1000 TA = 125C 100 INPUT CURRENT (nA) 10 1 0.1 0.01 TA = 25C TA = -40C V+ = 0V VSENSE = 0V 0 5 10 15 20 25 30 35 40 45 50 VS+ INPUT VOLTAGE (V)
6105 G16
Output Voltage vs VSENSE Voltage, VS+ = 12V
1.6 V+ = 3V 1.4 RIN = 100 A V = 10V/V OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 1.2 1.0 0.8 TA (25C, 85C, 125C) 0.6 0.4 0.2 0.0 -10 10 30 70 90 VSENSE (mV) 50 110 130 TA = - 40C 1.4
Output Voltage vs VSENSE Voltage, VS+ = 0V
V+ = 3V R = 100 1.2 A IN= 10V/V V 1.0 TA 0.8 (- 40C, 25C, 85C, 125C) 0.6 0.4 0.2 0.0 -10
TA = 85C
0.001 0.0001
10
30
6105 G17
70 90 50 VSENSE (mV)
110
130
6105 G18
Output Saturation Voltage vs Output Current, VS+ = 12V
2.0 OUTPUT SATURATI0N VOLTAGE (V) OUTPUT SATURATI0N VOLTAGE (V) V + = 12V 1.9 VSENSE = 0.5V RIN = 100 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 TA = 85C TA = 125C OUTPUT SATURATION VOLTAGE = V+ - V 0.01 0.10 1 OUTPUT CURRENT (mA)
OUT
Output Saturation Voltage vs Output Current, VS+ = 0.5V
OUTPUT SHORT-CIRCUIT CURRENT (mA) V + = 12V 1.3 VSENSE = 0.5V RIN = 100 1.2 1.1 1.0 TA = 85C 0.9 0.8 0.7 0.6 0.5 10
6105 G19
Output Short-Circuit Current vs Temperature
3.4 V + = 5V VS+ = 5V 3.2 V SENSE = 5V RIN = 100 3.0 2.8 2.6 2.4 2.2 2.0 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
6105 G21
1.4
TA = - 40C TA = 25C
TA = 125C
TA = - 40C
TA = 25C
OUTPUT SATURATION VOLTAGE = V+ - V 0.01 0.10 1 OUTPUT CURRENT (mA)
1.0 0.001
0.4 0.001
OUT
10
6105 G20
Supply Current vs Supply Voltage, VS+ = 12V
500 VSENSE = 0V RIN = 100 A V = 50V/V SUPPLY CURRENT (A) 500
Supply Current vs Supply Voltage, VS+ = 0V
VSENSE = 0V RIN = 100 A V = 50V/V SUPPLY CURRENT (A) 400
Supply Current vs Input Voltage
V+ = 3V VSENSE = 0V 350 RIN = 100 TA = 125C 250 200 150 100 50 TA = 85C TA = 25C TA = - 40C
400 SUPPLY CURRENT (A)
400
300
300
TA = 125C TA = 85C
300
TA = 125C TA = 85C
200
TA = 25C TA = - 40C
200
TA = 25C TA = - 40C
100
100
0 0 5 10 15 20 25 30 35 40 V+ SUPPLY VOLTAGE (V)
6105 G22
0 0 5 10 15 20 25 30 35 40 V+ SUPPLY VOLTAGE (V)
6105 G23
0 0 5 10 15 20 25 30 35 VS+ INPUT VOLTAGE (V) 40 45
6105 G24
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LT6105 TYPICAL PERFORMANCE CHARACTERISTICS
Gain vs Frequency
40 30 20 GAIN (dB) 10 0 -10 -20 -30 -40 1k 10k 100k 1M FREQUENCY (Hz) 10M
6105 G25
Common Mode Rejection Ratio vs Frequency
COMMON MODE REJECTION RATIO (dB) POWER SUPPLY REJECTION RATIO (dB) V+ = VS+ = 12V VSENSE = 50mV RIN = 100 AV = 10V/V 140 120 100 80 60 40 20 0 100 V+ = 12V VS+ = 12V RIN = 100 AV = 50V/V 160 140 120 100 80 60 40 20
Power Supply Rejection Ratio vs Frequency
VS+ = 12V V+ = 12V VSENSE = 5mV RIN = 100 AV = 10V/V
VS+ = 0V
1k
10k 100k FREQUENCY (Hz)
1M
10M
6105 G26
0 0.1
1
10 100 1k 10k FREQUENCY (Hz)
100k
1M
6105 G27
Slew Rate vs RIN
2.5 +SLEW RATE 12V VS- 100mV/DIV
Step Response VSENSE = 0V to 100mV, VS+ = 12V
0V VS- 100mV/DIV
Step Response VSENSE = 0V to 100mV, VS+ = 0V
2.0 SLEW RATE (V/s)
1.5 -SLEW RATE 1.0 V + = 12V 0.5 V + = 12V S VOUT = 7.5V A V = 50V/ V 0 0 100 200 300 400 500 600 700 800 900 1000 RIN ()
6105 G28
VOUT 500mV/DIV 0V 50s/DIV V + = 12V RIN = 1k ROUT = 10k AV = 10V/V
6105 G29
VOUT 500mV/DIV 0V 50s/DIV V + = 12V RIN = 1k ROUT = 10k AV = 10V/V
6105 G30
Step Response VSENSE = 0V to 100mV, RIN = 100
12V VS- 100mV/DIV 12V VS- 100mV/DIV
Step Response VSENSE = 0V to 100mV
11.995V VS- 100mV/DIV
Step Response VSENSE = 5mV to 100mV
5V VOUT 2V/DIV 0V 50s/DIV V + = 12V VS+ = 12V AV = 50V/ V
6105 G31
VOUT 2V/DIV 0V
VOUT 5V 2V/DIV 0V
5s/DIV V + = 12V VS+ = 12V RIN = 1k ROUT = 50k AV = 50V/ V
6105 G32
5s/DIV V+ = 12V VS+ = 12V RIN = 1k ROUT = 50k AV = 50V/ V
6105 G33
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9
LT6105 TYPICAL PERFORMANCE CHARACTERISTICS
Step Response VSENSE = 100mV to 5mV
11.995V VS- 100mV/DIV 12V VS- 10mV/DIV
Step Response VSENSE = 0V to 10mV, VS+ = 12V
0V VS- 10mV/DIV
Step Response VSENSE = 0V to 10mV, VS+ = 0V
VOUT 5V 2V/DIV 0V VOUT 200mV/DIV 0V 5s/DIV V+ = 12V VS+ = 12V RIN = 1k ROUT = 50k AV = 50V/ V
6105 G34
VOUT 200mV/DIV 0V 50s/DIV V+ = 12V RIN = 100 ROUT = 5k AV = 50V/ V
6105 G35
50s/DIV V+ = 12V RIN = 100 ROUT = 5k A V = 50V/ V
6105 G36
Step Response VSENSE = 0V to 100mV, , CL = 1000pF VS+ = 12V
12V VS- 100mV/DIV 12V VS- 10mV/DIV
Step Response VSENSE = 0V to 10mV, , CL = 1000pF VS+ = 12V
0V VS- 100mV/DIV
Step Response VSENSE = 0V to 100mV, , CL = 1000pF VS+ = 0V
VOUT 2V/DIV 0V 50s/DIV V+ = 12V RIN = 100 ROUT = 5k AV = 50V/ V CL = 1000pF
6105 G37
VOUT 200mV/DIV 0V 50s/DIV V+ = 12V RIN = 100 ROUT = 5k AV = 50V/ V CL = 1000pF
6105 G38
VOUT 2V/DIV 0V 50s/DIV V+ = 12V RIN = 100 ROUT = 5k AV = 50V/ V CL = 1000pF
6105 G39
Step Response VSENSE = 0V to 10mV, , CL = 1000pF VS+ = 0V
0V VS- 10mV/DIV 5V V+ 0V
Power Supply Start-Up Response
VOUT 200V/DIV 0V 50s/DIV V+ = 12V RIN = 100 ROUT = 5k AV = 50V/ V CL = 1000pF
6105 G40
VOUT 1V/DIV 0V
20s/DIV VS+ = 12V VSENSE = 100mV RIN = 1k AV = 10V/ V
6105 G41
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10
LT6105 PIN FUNCTIONS
(DCB/MS8)
-IN (Pin 1/Pin 1): Negative Sense Input Terminal. Negative sense voltage input will remain functional for voltages up to 44V, referred to V -. Connect -IN to an external gain-setting resistor RIN1 (RIN1 = RIN2) to set the gain. V+ (Pin 2/Pin 2): Power Supply Voltage. This pin supplies current to the amplifier and can operate from 2.85V to 36V, independent of the voltages on the -IN or +IN pins. V - (Pin 3/Pin 4): Negative Power Supply Voltage or Ground for Single Supply Operation. VOUT (Pin 4/Pin 5): Voltage Output: VOUT = A V * (VSENSE VOS)
VOS is the input offset voltage. A V is the gain set by external RIN1, RIN2, ROUT. A V = ROUT/RIN1, for RIN1 = RIN2. NC (Pin 5/Pins 3, 6, 7): Not Connected Internally. +IN (Pin 6/Pin 8): Positive Sense Input Terminal. Connecting a source to VS+ and a load to VS- will allow the LT6105 to monitor the current through RSENSE , refer to Figure 1. Connect +IN to an external gain-setting resistor RIN2 to set the gain. +IN remains functional for voltages up to 44V, referred to V -. Exposed Pad (Pin 7) DFN Only: V -. The Exposed Pad is connected to the V - pin. It should be connected to the V - trace of the PCB, or left floating.
BLOCK DIAGRAM
TO LOAD VS- VSENSE RSENSE VS+ SOURCE 0V TO 44V
RIN1 -IN
RIN2 +IN LT6105 SET RIN1 = RIN2 FOR BEST ACCURACY V(-IN) > 1.6V: VOUT = VSENSE * IF RIN1 RIN2, THEN A2 ROUT RIN2 ROUT V(-IN) < 1.6V: VOUT = VSENSE * RIN1
V+ A1
+
Q2 Q3
+ -
Q1
-
RIN1, RIN2, ROUT ARE EXTERNAL RESISTORS
V-
VOUT VOUT = VSENSE * ROUT
6105 F01
ROUT RIN
WHERE RIN = RIN1 = RIN2 AV = ROUT RIN
Figure 1. Simplified Block Diagram
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11
LT6105 APPLICATIONS INFORMATION
The LT6105 extended input range current sense amplifier (see Figure 1) provides accurate unidirectional monitoring of current through a user-selected sense resistor. The LT6105 is fully specified over a -0.3V to 44V input common mode range. A high PSRR V+ supply (2.85V to 36V) powers the current sense amplifier. The input sense voltage is level shifted from the sensed power supply to the ground reference and amplified by a user-selected gain to the output. The output voltage is directly proportional to the current flowing through the sense resistor. THEORY OF OPERATION (Refer to Figure 1) Case 1: High Input Voltage (1.6V < V-IN < 44V) Current from the source at VS+ flows through RSENSE to the load at VS-, creating a sense voltage, VSENSE. Inputs VS+ and VS- apply the sense voltage to RIN2. The opposite ends of resistors RIN1 and RIN2 are forced to be at equal potentials by the voltage gain of amplifier A2. Thus, the current through RIN2 is VSENSE/RIN2. The current through RIN2 is forced to flow through transistor Q1 and into ROUT, creating an output voltage, VOUT. Under this input operation range, amplifier A1 is kept off. The base current of Q1 has been compensated for and will not contribute to output error. The current from RIN2 flowing through resistor ROUT gives an output voltage of VOUT = VSENSE * ROUT/RIN2, producing a gain voltage of A V = VOUT /VSENSE = ROUT/RIN2. Case 2: Low Input Voltage (0V < V-IN < 1.6V) Current from the source at VS+ flows through RSENSE to the load at VS-, creating a sense voltage, VSENSE. Inputs VS+ and VS- apply the sense voltage to RIN1. The opposite ends of resistors RIN1 and RIN2 are forced to be at equal potentials by the voltage gain of amplifier A1. Thus, the collector current of Q3 will flow out of the -IN pin through RIN1. Q2 mirrors this current VSENSE/RIN1 to ROUT, creating an output voltage, VOUT. Under this input operation range, amplifier A2 is kept off. This current VSENSE/RIN1 flowing through resistor ROUT gives an output voltage of VOUT = VSENSE * ROUT /RIN1, producing a gain voltage of A V = VOUT/VSENSE = ROUT /RIN1. Selection of External Current Sense Resistor External RSENSE resistor selection is a delicate trade-off between power dissipation in the resistor and current measurement accuracy. For high current applications, the user may want to minimize the sense voltage to minimize the power dissipation in the sense resistor. The system load current will cause both heat and voltage loss in RSENSE. As a result, the sense resistor should be as small as possible while still providing the input dynamic range required by the measurement. Note that input dynamic range is the difference between the maximum input signal and the minimum accurately reproduced signal, and is limited primarily by input DC offset voltage of the internal amplifier of the LT6105. The sense resistor value will be set from the minimum signal current that can be accurately resolved by this sense amp. As an example, the LT6105 has a typical input offset of 100V. If the minimum current is 20mA, a sense resistor of 5m will set VSENSE to 100V, which is the same value as the input offset. A larger sense resistor will reduce the error due to offset by increasing the sense voltage for a given load current, but it will limit the maximum peak current for a given application. For a peak current of 2A and a maximum VSENSE of 80mV, RSENSE should not be more than 40m. The input offset causes an error equivalent to only 2.5mA of load current. Peak dissipation is 160mW. If a 20m sense resistor is employed, then the effective current error is 5mA, while the peak sense voltage is reduced to 40mV at 2A, dissipating only 80mW. The LT6105's low input offset voltage of 100V allows for high resolution while limiting the maximum sense voltages. Coupled with full scale sense voltage as large as 1V for RIN= 1k, it can achieve 80dB of dynamic range. Sense Resistor Connection Kelvin connection of the LT6105's input resistors to the sense resistor should be implemented to provide the highest accuracy in high current applications. Solder connections and PC board interconnect resistance (approximately 0.5m per square for 1oz copper) can be a large error in high current systems. A 5A application might choose
6105f
12
LT6105 APPLICATIONS INFORMATION
a 20m sense resistor to give a 100mV full-scale input to the LT6105. Input offset voltage will limit resolution to 5mA. Neglecting contact resistance at solder joints, even one square of PC board copper at each resistor end will cause an error of 5%. This error will grow proportionately higher as monitored current levels rise. Gain Setting The gain is set with three external resistors, RIN1, RIN2, ROUT. The gain, ROUT /RIN, selected can range from 1V/V to 100V/V as long as the maximum current does not exceed 1mA. Select Gain = ROUT/RIN2 for sense input voltage operation greater than 1.6V. Select gain = ROUT/RIN1 for sense input voltage operation less than 1.6V. The overall system error will depend on the resistor tolerance chosen for the application. Set RIN1= RIN2 for best accuracy across the entire input range. The total error will be gain error of the resistors plus the gain error of the LT6105 device. Output Signal Range The LT6105's output signal is developed by current through RIN2 (44V > V-IN > 1.6V) or RIN1 (0V < V-IN < 1.6V) conducted to the output resistor, ROUT. This current is VSENSE/RIN2 or VSENSE/RIN1. The sense amplifier's maximum output current before gain error begins to increase
0.80 V+ = 12V 0.60 VSENSE = 5mV A V = 50V/V 0.40 0.20 0 -0.20 -0.40 -0.60 -0.80 -1.00 0 5 10 35 VS+ INPUT VOLTAGE (V) 15 20 25 30 40 45
6105 F02
is 1mA. This allows low value output resistors to be used which helps preserve signal accuracy when the output pin is connected to other systems. For zero VSENSE, the internal circuitry gain will force VOUT to VO(MIN) referred to V -. Depending on output currents, VOUT may swing positive to within VO(MAX) referred to V + or a maximum of 36V, a limit set by internal junction breakdown. Within these constraints, an amplified, level shifted representation of RSENSE voltage is developed at VOUT. The output is well behaved driving capacitive loads. CM Input Signal Range The LT6105 has high CMRR over the full input voltage range. The minimum operation voltage of the sense amplifier inputs is 0V whether V+ is at 2.7V or 36V. The output remains accurate even when the sense inputs are driven to 44V. The graph in Figure 2 shows that VOS changes very slightly over a wide input range. Furthermore, either sense inputs VS+ and VS- can collapse to 0V without incurring any damage to the device. The LT6105 can handle differential sense voltages up to 44V. For example, VS+ = 44V and VS- = 0V can be a valid condition in a current monitoring application (Figure 3) when an overload protection fuse is blown and VS- voltage collapses to ground. Under this condition, the output of the LT6105 goes to the positive rail, VO(MAX).
TO LOAD VS- RSENSE RIN1 FUSE RIN2 VS+ C1 0.1 F DC SOURCE ( 44V)
INPUT OFFSET VOLTAGE (mV)
TA = 25C TA = - 40C TA = 125C
-IN
+IN
+
5V
V+
TA = 85C
V- OUT LT6105
6105 F03
Figure 2. Input Offset Voltage vs VS
+ Input Voltage
Figure 3. Current Monitoring of a Fuse Protected Circuit
+
OUTPUT ROUT
6105f
-
C2 0.1 F
13
LT6105 APPLICATIONS INFORMATION
There is no phase inversion. For the opposite case, when VS+ collapses to ground with VS- held up at some higher voltage potential, the output will sit at VO(MIN). The Two Input Stages Crossover Region The wide common mode input range is achieved with two input stages. These two input stages consist of a pair of matched common base PNP input transistors and a pair of common emitter PNP input transistors. As result of two input stages, there will be three distinct operating regions around the transition region as shown in the Input Bias Current vs Sense Input Voltage curve in the Typical Performance Characteristics section. The crossover voltage, the voltage where the gm of one input stage is transferred to the other, occurs at 1.6V above V-. Near this region, one input stage is shutting off while the other is turning on. Increases in temperature will cause the crossover voltage to decrease. For input operation between 1.6V and 44V, the common base PNPs are active (Q2, Q3 of Figure 1). The typical current through each input at VSENSE = 0V is 15A. The input offset voltage is 300V maximum at room temperature. For input operation between 1.6V to 0V, the other PNP is active. The current out of the inputs at VSENSE = 0V is 100nA. The input offset voltage is untrimmed and is typically 300V. Selection of External Output Resistor, ROUT The output resistor, ROUT, determines how the output current is converted to voltage. VOUT is simply IRIN * ROUT. In choosing an output resistor, the maximum output voltage must first be considered. If the following circuit is a buffer or ADC with limited input range, then ROUT must be chosen so that IOUT(MAX) * ROUT is less than the allowed maximum input range of this circuit. In addition, the output impedance is determined by ROUT. If the circuit to be driven has high input impedance, then almost any useful output impedance will be acceptable. However, if the driven circuit has relatively low input impedance, or draws spikes of current such as an ADC might do, then a lower ROUT value may be required in order to preserve the accuracy of the output. As an example, if the input impedance of the driven circuit is 100 times ROUT, then the accuracy of VOUT will be reduced by 1% since: VOUT = IOUT * ROUT * RIN(DRIVEN) ROUT + RIN(DRIVEN) 100 = 0 . 99 * IOUT * ROUT 101
= IOUT * ROUT *
Full-Scale Sense Voltage, Selection of External Input Resistor, RIN The external input resistor, RIN, controls the transconductance of the current sense circuit. Since IOUT = VSENSE /RIN, transconductance gm = 1/RIN. For example, if RIN =100, then IOUT = VSENSE /100 or IOUT = 1mA for VSENSE =100mV. RIN should be chosen to allow the required resolution while limiting the output current. The LT6105 can output more than 1mA into ROUT without introducing a significant increase in gain error. By setting RIN such that the largest expected sense voltage gives IOUT = 1mA, then the maximum output dynamic range is available. Output dynamic range is limited by both the maximum allowed output current and the maximum allowed output voltage, as well as the minimum practical output signal. If less dynamic range is required, then RIN can be increased accordingly, reducing the maximum output current and power dissipation. The LT6105's performance is optimized for values of RIN = 100 to 1k. Values outside this range may result in additional errors. The power dissipation across RIN and ROUT should not exceed the resistors' recommended ratings.
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14
LT6105 APPLICATIONS INFORMATION
Error Sources The current sense system uses an amplifier, current mirrors and external resistors to apply gain and level shifting. The output is then dependent on the matching characteristics of the current mirrors, characteristics of the amplifier such as gain and input offset, as well as matching of external resistors. Ideally, the circuit output is: R VOUT = VSENSE * OUT ; VSENSE = ISENSE * R SENSE RIN In this case, the only error is due to resistor mismatch, which provides an error in gain only. Mismatch in the internal current mirror adds to gain error but is trimmed to less than 0.3%. Offset voltage and sense input current are the main cause of any additional error. Error Due to Input Offset Voltage Dynamic range is inversely proportional to the input offset voltage. Dynamic range can be thought of as the maximum VSENSE divided by VOS. The offset voltage of the LT6105 is typically only 100V. Error Due to Sense Input Offset Current Input offset current or mismatches in input bias current will introduce an additional input offset voltage term. Typical input offset current is 0.05A. Lower values of RIN will keep this error to a minimum. For example, if RIN = 100, then the additional offset is 5V. Output Current Limitations Due to Power Dissipation The LT6105 can deliver up to 1mA continuous current to the output pin. This output current, IOUT, is the mirrored current which flows through RIN2 and enters the current sense amp via the +IN pin for V-IN > 1.6V, and exits out of -IN through RIN1 for V-IN < 1.6V. The total power dissipation due to input currents, PIN, and the dissipation due to internal mirrored currents, PQ: PTOTAL = PIN + PQ PIN = (V+IN) * IRIN2 ; V-IN > 1.6V or PIN = (V+ - (V-IN)) * IRIN1; V-IN < 1.6V Since the current exiting -IN is coming from V+, the voltage is V+ - V-IN. Taking the worst case V-IN = 0V, the above equation becomes: PIN V+ * IRIN1, for V-IN < 1.6V. The power dissipated due to internal mirrored currents: PQ = 2 * IOUT * V+ The factor of 2 is the result of internal current shifting and 1:1 mirroring. At maximum supply and maximum output current, the total power dissipation can exceed 100mW. This will cause significant heating of the LT6105 die. In order to prevent damage to the LT6105, the maximum expected dissipation in each application should be calculated. This number can be multiplied by the JA value listed in the Pin Configuration section to find the maximum expected die temperature. This must not be allowed to exceed 150C, or performance may be degraded. As an example, if an LT6105 in the MSOP package is to be run at VS+ = 44V and V+ = 36V with 1mA output current at 80C ambient: PQ(MAX) = 2 * IOUT(MAX) * V+ = PQ(MAX) = 72mW PIN(MAX) = IRIN2(MAX) * V+IN(MAX) = 44mW TRISE = JA * PTOTAL(MAX) TMAX = TAMBIENT + TRISE TMAX must be < 150C PTOTAL(MAX) = 116mW and the maximum die temperature will be 109C. If this same circuit must run at 125C ambient, the maximum die temperature will increase to 150C. Note that supply current, and therefore PQ, is proportional to temperature. Refer to the Typical Performance Characteristics section. In this condition, the maximum output current should be reduced to avoid device damage. The DCB package, on the other hand, has a lower JA and subsequently, a lower die temperature increase than the MSOP With the same condition as above, the DCB will . rise only 7.5C to 87.5C and 132.5C, respectively. It is important to note that the LT6105 has been designed to provide at least 1mA to the output when required, and can deliver more under large VSENSE conditions. Care must be taken to limit the maximum output current by proper choice of sense resistor and input resistors.
6105f
15
LT6105 APPLICATIONS INFORMATION
Output Filtering The output voltage, VOUT is simply IOUT * ZOUT. This makes filtering straightforward. Any circuit may be used which generates the required ZOUT to get the desired filter response. For example, a capacitor in parallel with ROUT will give a low pass response. This will reduce unwanted noise from the output, and may also be useful as a charge reservoir to keep the output steady while driving a switching circuit such as a mux or an ADC. This output capacitor in parallel with an output resistor will create a pole in the output response at: 1 f - 3db = 2 * * ROUT * COUT Response Time The LT6105 is designed to exhibit fast response to inputs for the purpose of circuit protection or signal transmission. This response time will be affected by the external circuit in two ways--delay and speed. If the output current is very low and an input transient occurs, there may be an increased delay before the output voltage begins changing. This can be improved by increasing the minimum output current, either by increasing RSENSE or decreasing RIN. The effect of increased output current is illustrated in the step response curves in the Typical Performance Characteristics section of this data sheet. Note that the curves are labeled with respect to the initial output currents. The speed is also affected by the external circuit. In this case, if the input changes very quickly, the internal amplifier will slew the base of the internal output PNP (Figure 1) in order to maintain the internal loop. This results in current flowing . through RIN and the internal PNP This current slew rate will be determined by the amplifier and PNP characteristics as well as the input resistor, RIN. See the Slew Rate vs RIN curve in the Typical Performance Characteristics section. Using a smaller RIN will allow the output current to increase more quickly, decreasing the response time at the output. This will also have the effect of increasing the maximum output current.
TYPICAL APPLICATIONS
Gain of 20 Current Sense Amplifier with Output Filtering
2.85V TO 36V V+
SOURCE 0V TO 44V LT6105 249 +IN
VS+ 0.039 VS-
+ -
VOUT
VOUT = 780mV/A 4.99k 0.22F
-IN 249
V TO LOAD
-
6105 TA02
6105f
16
LT6105 TYPICAL APPLICATIONS
Solenoid Monitor The large input common mode range of the LT6105 makes it suitable for monitoring currents in quarter, half and full bridge inductive load driving applications. Figure 4 shows an example of a quarter bridge. The MOSFET pulls down on the bottom of the solenoid to increase solenoid current. It lets go to decrease current, and the solenoid voltage freewheels around the Schottky diode. Current measurement waveforms are shown in Figure 5. The small glitches occur due to the action of the solenoid plunger, and this provides an opportunity for
24VDC 24V/OFF 19V/ON TP0610L 200 1% 2k 1% LT6105 1N5818
mechanical system monitoring without an independent sensor or limit switch. Figure 6 shows another solenoid driver circuit, this time with one end of the solenoid grounded and a P-channel MOSFET pulling up on the other end. In this case, the inductor freewheels around ground, imposing a negative input common mode voltage of one Schottky diode drop. This voltage may exceed the input range of the LT6105. This does not endanger the device, but it severely degrades its accuracy. In order to avoid violating the input range, pull-up resistors may be used as shown.
24VDC
1N5818
200 1% -IN 0V/OFF 5V/ON 2N7000
200 1% +IN
200 1% 24V, 3W SOLENOID
LT6105
2k 1%
-IN 5VDC V+ 5VDC V- VOUT
6105 F04
V+
VOUT = 25mV/mA 4.99k 1% V- VOUT
6105 F06
Figure 4. Simplest Form of a Solenoid Driver. The LT6105 Monitors the Current in Both On and Freewheel States. The Lowest Common Mode Voltage Is 0V, While the Highest Is 24V Plus the Forward Voltage of the Schottky Diode
VBAT = 3.6V ICPO = 200A 5V/DIV CCPO = 2.2F
Figure 6. A Similar Circuit to Figure 4, but with Solenoid Grounded, so Freewheeling Forces Inputs Negative. Providing Resistive Pull-Ups Keeps Amplifier Inputs From Falling Outside of Their Accurate Input Range
10V/DIV
2V/DIV 50ms/DIV
6105 F05
Figure 5. Current Measurement Waveforms. The Top Trace Is the MOSFET Gate with High On. The Middle Trace Is the Bottom of the Solenoid/ Inductor. The Bottom Trace Is the LT6105 Output, Representing Solenoid Current at 80mA /DIV. Glitches Are Useful Indicators of Solenoid Plunger Movement
6105f
+
1N914 +IN
-
1 1%
24V, 3W SOLENOID
1 1%
+
-
VOUT = 25mV/mA 4.99k 1%
17
LT6105 PACKAGE DESCRIPTION
DCB Package 6-Lead Plastic DFN (2mm x 3mm) (Reference LTC DWG # 05-08-1715)
0.70 0.05
3.55 0.05
1.65 0.05 (2 SIDES) PACKAGE OUTLINE
2.15 0.05
0.25 0.05 0.50 BSC 1.35 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 2.00 0.10 (2 SIDES) R = 0.115 TYP R = 0.05 TYP 0.40 0.10 4 6
3.00 0.10 (2 SIDES) PIN 1 BAR TOP MARK (SEE NOTE 6)
1.65 0.10 (2 SIDES) PIN 1 NOTCH R0.20 OR 0.25 x 45 CHAMFER 3 1
(DCB6) DFN 0405
0.200 REF
0.75 0.05
0.25 0.05 0.50 BSC
1.35 0.10 (2 SIDES) 0.00 - 0.05 BOTTOM VIEW--EXPOSED PAD
NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (TBD) 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 SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE
6105f
18
LT6105 PACKAGE DESCRIPTION
MS8 Package 8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
0.889 0.127 (.035 .005)
5.23 (.206) MIN
3.20 - 3.45 (.126 - .136)
0.42 0.038 (.0165 .0015) TYP
0.65 (.0256) BSC
3.00 0.102 (.118 .004) (NOTE 3)
8
7 65
0.52 (.0205) REF
RECOMMENDED SOLDER PAD LAYOUT
DETAIL "A" 0 - 6 TYP 4.90 0.152 (.193 .006) 3.00 0.102 (.118 .004) (NOTE 4)
0.254 (.010) GAUGE PLANE
1 0.53 0.152 (.021 .006) DETAIL "A" 0.18 (.007) SEATING PLANE 0.22 - 0.38 (.009 - .015) TYP 1.10 (.043) MAX
23
4 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
0.65 (.0256) BSC
0.127 0.076 (.005 .003)
MSOP (MS8) 0204
6105f
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.
19
LT6105 TYPICAL APPLICATION
Supply Monitoring The input common mode range of the LT6105 also makes it suitable for monitoring either positive or negative supplies. Figure 7 shows one LT6105 applied as a simple positive supply monitor, and another LT6105 as a simple negative supply monitor. Note that the schematics are practically identical and both have outputs conveniently referred to ground. The only requirement for negative supply monitoring, in addition to the usual constraints of the absolute maximum ratings, is that the negative supply to that LT6105 be at least as negative as the supply it is monitoring.
VOUT = 1V/A 4.99k 1% VOUT LT6105 V- -15V
V+
5VDC
+IN 100 1% +15V POSITIVE SUPPLY 20m + 1%
-IN 100 1% TO +15V LOAD
-
CURRENT FLOW CURRENT FLOW 20m 1%
100 1% -IN
LT6105
5VDC
V+
-15V
V- VOUT
6105 F07
Figure 7. The LT6105 Can Monitor the Current of Either Positive or Negative Supplies, Without a Schematic Change. Just Ensure That the Current Flow Is in the Correct Direction
RELATED PARTS
PART NUMBER LT1787/LT1787HV LTC4150 LT6100 LTC6101/ LTC6101HV LTC6102/ LTC6102HV LTC6103 LTC6104 LT6106 DESCRIPTION Precision, Bidirectional, High Side Current Sense Amplifier Coulomb Counter/Battery Gas Gauge Gain-Selectable High Side Current Sense Amplifier High Voltage High Side Current Sense Amplifier Zero Drift High Side Current Sense Amplifier Dual High Side Precision Current Sense Amplifier Bidirectional High Side Precision Current Sense Amplifier Low Cost, High Side Precision Current Sense Amplifier COMMENTS 2.7V to 60V Operation, 75V Offset, 60A Current Draw Indicates Charge Quantity and Polarity 4.1V to 48V Operation, Pin-Selectable Gain: 10V/V, 12.5V/V, 20V/V, 25V/V, 40V/V, 50V/V 4V to 60V/5V to 100V Operation, External Resistor Set Gain, SOT23 4V to 60V/5V to 100V Operation, 10V Offset, 1s Step Response, MSOP8 / DFN 4V to 60V, Gain Configurable, 8-Pin MSOP 4V to 60V, Gain Configurable, 8-Pin MSOP 2.7V to 36V, Gain Configurable, SOT23
6105f LT 1207 * PRINTED IN USA
20 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2007
+
+IN
-
-15V NEGATIVE SUPPLY
TO -15V LOAD 100 1%
VOUT = 1V/A 4.99k 1%

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