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LT6100 Precision, Gain Selectable High Side Current Sense Amplifier DESCRIPTIO
The LT(R)6100 is a complete micropower, precision, high side current sense amplifier. The LT6100 monitors unidirectional currents via the voltage across an external sense resistor. Fixed gains of 10, 12.5, 20, 25, 40, 50V/V are obtained by simply strapping or floating two gain select pins. Gain accuracy is better than 0.5% for all gains. The LT6100 sense inputs have a voltage range that extends from 4.1V to 48V, and can withstand a differential voltage of the full supply. This makes it possible to monitor the voltage across a MOSFET switch or a fuse. The part can also withstand a reverse battery condition on the inputs. Input offset is a low 300V. CMRR and PSRR are in excess of 105dB, resulting in a wide dynamic range. A filter pin is provided to easily implement signal filtering with a single capacitor. The LT6100 has a separate supply input, which operates from 2.7V to 36V and draws only 60A. When VCC is powered down, the sense pins are biased off. This prevents loading of the monitored circuit, irrespective of the sense voltage. The LT6100 is available in an 8-lead DFN and MSOP package.
FEATURES

Input Offset Voltage: 300V (Max) Sense Inputs Up to 48V 0.5% Gain Accuracy Pin Selectable Gain: 10, 12.5, 20, 25, 40, 50V/V Separate Power Supply: 2.7V to 36V Operating Current: 60A Sense Input Current (VCC Powered Down): 1nA Reverse Battery Protected to - 48V Buffered Output Noise Filtering Input -40C to 125C Operating Temperature Range Available in 8-Lead DFN and MSOP Packages
APPLICATIO S

Battery Monitoring Fuse Monitoring Portable and Cellular Phones Portable Test/Measurement Systems
, LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
4.4V TO 48V SUPPLY LT6100
+ 8 VS
0A to 33A High Side Current Monitor with 12kHz Frequency Rolloff
3V
Input Offset Voltage vs VS Sense Input Voltage
1.5 VSENSE = 100mV VCC = 3V TA = 25C
VCC
A4
A2
INPUT OFFSET VOLTAGE (mV)
2
7
6
1.0 0.5 0 -0.5 -1.0 -1.5
RSENSE 3m - 1 VS VEE 4 CONFIGURED FOR GAIN = 25V/V
VOUT 5
VOUT = 2.5V ISENSE = 33A
LOAD
FIL 3 220pF
6100 TA01a
0
5
U
U
U
10 15 20 25 30 35 40 45 50 VS SENSE INPUT VOLTAGE (V)
6100 TA01b
6100f
1
LT6100
ABSOLUTE
AXI U
RATI GS
Differential Sense Voltage ..................................... 48V Total VS+, VS- to VEE ............................................... 48V Total VCC Supply Voltage from VEE ......................... 36V Output Voltage ............................... (VEE) to (VEE + 36V) Output Short-Circuit Duration (Note 3) ........ Continuous Operating Temperature Range (Note 4) LT6100C ............................................. - 40C to 85C LT6100I .............................................. - 40C to 85C LT6100H .......................................... - 40C to 125C
PACKAGE/ORDER I FOR ATIO
TOP VIEW VS - 1 VCC 2 FIL 3 VEE 4 9 8 7 6 5 VS+ A4 A2 VOUT
ORDER PART NUMBER
TOP VIEW
LT6100CDD LT6100IDD LT6100HDD DD PART MARKING* LBMW
DD PACKAGE 8-LEAD (3mm x 3mm) PLASTIC DFN
TJMAX = 125C, JA = 43C/ W EXPOSED PAD (PIN 9) IS VEE MUST BE SOLDERED TO PCB
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grades are identified by a label on the shipping container.
ELECTRICAL CHARACTERISTICS
The denotes specifications which apply over the temperature range 0C TA 70C (LT6100C), otherwise specifications are TA = 25C. VCC = 5V, VEE = 0V, VS+ = VCC + 1.4V unless otherwise specified. (Note 5)
SYMBOL VS-, VS+ VSENSE VOS PARAMETER Sense Amplifier Supply Voltage Input Sense Voltage Full Scale Input Offset Voltage (MS Package) Input Offset Voltage (DD Package) VOS TC AV Temperature Coefficient of VOS Gain, VOUT/VSENSE CONDITIONS Single Supply Operation (VCC = 2.7V) VSENSE = VS+ - VS-, VCC = 3V, AV = 10V/V VSENSE = VS+ - VS-, VCC = 5V, AV = 10V/V IOUT = 0, VCC = 5V IOUT = 0, VCC = 5V VCC = 5V (Note 6) VSENSE = 50mV to 80mV, VCC Supply = 5V, AV = 10V/V LT6100DD8

VS = 48V Output Voltage Gain Error (Note 7) VSENSE = 50mV to 80mV, VCC Supply = 5V, AV = 10, 12.5, 20, 25, 40, 50V/V LT6100DD8
VS = 48V
2
U
U
W
WW U
W
(Notes 1, 2)
Specified Temperature Range (Note 5) LT6100C ............................................. - 40C to 85C LT6100I .............................................. - 40C to 85C LT6100H .......................................... - 40C to 125C Storage Temperature Range ........................................... DFN .................................................. - 65C to 125C MSOP ............................................... - 65C to 150C Lead Temperature (Soldering, 10 sec) MSOP .............................................................. 300C
ORDER PART NUMBER
VS- 1 VCC 2 FIL 3 VEE 4 8 7 6 5 VS+ A4 A2 VOUT
LT6100CMS8 LT6100IMS8 LT6100HMS8 MS PART MARKING* LTBMV
MS8 PACKAGE 8-LEAD PLASTIC MSOP
TJMAX = 150C, JA = 250C/ W
MIN 4.1 110 300 -300 -500 -350 -550 9.95 9.94 9.90 9.9 -0.5

TYP
MAX 48
UNITS V mV mV V V V V V/C V/V V/V V/V V/V % % % %
6100f
80 80 0.5 10 10 10 10
300 500 350 550 3 10.05 10.06 10.10 10.10 0.5 0.6 1.0 1.0
-0.6 -1.0 -1.0
LT6100
ELECTRICAL CHARACTERISTICS
The denotes specifications which apply over the temperature range 0C TA 70C (LT6100C), otherwise specifications are TA = 25C. VCC = 5V, VEE = 0V, VS+ = VCC + 1.4V unless otherwise specified. (Note 5)
SYMBOL VS CMRR VCC PSRR VCC BW tS IS+(O), IS-(O) ICC(O) SR ISC VO(MIN) VO(MAX) PARAMETER VS Sense Input Common Mode Rejection Ratio VCC Supply Rejection Ratio Supply Voltage VCC Bandwidth Output Settling to 1% Final Value Sense Input Current VCC Supply Current Slew Rate Short-Circuit Current Reverse VS Supply Minimum Output Voltage Output High AV = 10V/V, fO = -3dB AV = 50V/V, fO = -3dB VSENSE = 10mV to 100mV VSENSE = 0V VSENSE = 0V, VCC = 5V VCC = 15V, VSENSE = 50mV to 300mV, AV = 50V/V

CONDITIONS VSENSE = 50mV, VCC = 2.7V, VS = 4.1V to 36V
MIN 105 100 105 100 2.7 100 20
TYP 120 120 120 120
MAX
UNITS dB dB dB dB
VSENSE = 50mV, VS = 36V, VCC = 3V to 30V
36 150 50 15 4.5 60 10 130
V kHz kHz s A A V/s V/s mA V
0.03 0.02 8 50
0.05 0.05 15 60 15 15 75 85 125 175 0.001 30 25 125 150 250 400 1
ISC+, ISC- IS = -100A VSENSE = 0V, No Load VSENSE = VS+ - VS- = -100mV, AV = 50V/V, No Load VCC = 5V, AV = 50V/V, VSENSE = 100mV, IL = 0 VSENSE = 100mV, IL = 100A VSENSE = 100mV, IL = 500A VSENSE = 100mV, IL = 1mA

mV mV mV mV mV mV A
IS+, IS- (Off) Sense Input Current (Power Down) VCC = 0V, VS = 48V, VSENSE = 0V
The denotes specifications which apply over the temperature range -40C TA 85C (LT6100I), otherwise specifications are TA = 25C. VCC = 5V, VEE = 0V, VS+ = VCC + 1.4V unless otherwise specified. (Note 5)
SYMBOL VS-, VS+ VSENSE VOS PARAMETER Sense Amplifier Supply Voltage Input Sense Voltage Full Scale Input Offset Voltage (MS Package) Input Offset Voltage (DD Package) VOS TC AV Temperature Coefficient of VOS Gain, VOUT/VSENSE CONDITIONS Single Supply Operation (VCC = 2.7V) VSENSE = VS+ - VS-, VCC = 3V, AV = 10V/V VSENSE = VS+ - VS-, VCC = 5V, AV = 10V/V IOUT = 0, VCC = 5V

MIN 4.1 110 300 -300 -550 -350 -600 9.95 9.94 9.90 9.9 -0.5 -0.6 -1.0 -1.0
TYP
MAX 48
UNITS V mV mV
80 80 0.5 10 10 10 10
300 550 350 600 3 10.05 10.06 10.10 10.10 0.5 0.6 1.0 1.0
V V V V V/C V/V V/V V/V V/V % % % %
IOUT = 0, VCC = 5V
VCC = 5V (Note 6) VSENSE = 50mV to 80mV, VCC = 5V, AV = 10V/V LT6100DD8
Output Voltage Gain Error (Note 7)
VS = 48V VSENSE = 50mV to 80mV, VCC = 5V, AV = 10, 12.5, 20, 25, 40, 50V/V LT6100DD8 VS = 48V

6100f
3
LT6100
ELECTRICAL CHARACTERISTICS
The denotes specifications which apply over the temperature range -40C TA 85C (LT6100I), otherwise specifications are TA = 25C. VCC = 5V, VEE = 0V, VS+ = VCC + 1.4V unless otherwise specified. (Note 5)
SYMBOL VS CMRR VCC PSRR VCC BW tS IS+(O), IS-(O) ICC(O) SR ISC VO(MIN) VO(MAX) PARAMETER VS Sense Input Common Mode Rejection Ratio VCC Supply Rejection Ratio Supply Voltage VCC Bandwidth Output Settling to 1% Final Value Sense Input Current Supply Current Slew Rate Short-Circuit Current Reverse VS Supply Minimum Output Voltage Output High AV = 10V/V, fO = -3dB AV = 50V/V, fO = -3dB VSENSE = 10mV to 100mV VSENSE = 0V VSENSE = 0V, V+ Supply = 5V VCC = 15V, VSENSE = 50mV to 300mV, AV = 50V/V

CONDITIONS VSENSE = 50mV, VCC = 2.7V, VS = 4.1V to 36V
MIN 105 100 105 100 2.7 100 20
TYP 120 120 120 120
MAX
UNITS dB dB dB dB
VSENSE = 50mV, VS = 36V, VCC = 3V to 30V
36 150 50 15 4.5 60 10 145
V kHz kHz s A A V/s V/s mA V
0.03 0.02 8 50
0.05 0.05 15 60 15 15 75 85 125 175 0.001 30 25 125 150 250 400 1
ISC+, ISC- IS = -100A VSENSE = 0V, No Load VSENSE = VS+ - VS- = -100mV, AV = 50V/V, No Load VCC = 5V, AV = 50V/V, VSENSE = 100mV, IL = 0 VSENSE = 100mV, IL = 100A VSENSE = 100mV, IL = 500A VSENSE = 100mV, IL = 1mA

mV mV mV mV mV mV A
IS+, IS- (Off) Sense Input Current (Power Down) VCC = 0V, VS = 48V, VSENSE = 0V
The denotes specifications which apply over the temperature range -40C TA 125C (LT6100H), otherwise specifications are TA = 25C. VCC = 5V, VEE = 0V, VS+ = VCC + 1.4V unless otherwise specified. (Note 5)
SYMBOL VS-, VS+ VSENSE VOS PARAMETER Sense Amplifier Supply Voltage Input Sense Voltage Full Scale Input Offset Voltage (MS Package) Input Offset Voltage (DD Package) VOS TC AV Temperature Coefficient of VOS Gain, VOUT/VSENSE CONDITIONS Single Supply Operation (VCC = 2.7V) VSENSE = VS - VS-, VCC = 3V, AV VSENSE = VS+ - VS-, VCC = 5V, AV IOUT = 0, VCC = 5V
+
MIN

TYP
MAX 48
UNITS V mV mV
4.1 110 300 -300 -600 -350 -650 9.95 9.94 9.90 9.9 -0.5 80 80 0.5 10 10 10 10
= 10V/V = 10V/V
300 600 350 650 5 10.05 10.06 10.10 10.10 0.5 0.6 1.0 1.0
V V V V V/C V/V V/V V/V V/V % % % %
IOUT = 0, VCC = 5V
VCC = 5V (Note 6) VSENSE = 50mV to 80mV, VCC = 5V, AV = 10V/V LT6100DD8
VS = 48V Output Voltage Gain Error (Note 7) VSENSE = 50mV to 80mV, VCC = 5V, AV = 10, 12.5, 20, 25, 40, 50V/V LT6100DD8
VS = 48V
-0.6 -1.0 -1.0
6100f
4
LT6100
ELECTRICAL CHARACTERISTICS
The denotes specifications which apply over the temperature range -40C TA 125C (LT6100H), otherwise specifications are TA = 25C. VCC = 5V, VEE = 0V, VS+ = VCC + 1.4V unless otherwise specified. (Note 5)
SYMBOL VS CMRR VCC PSRR VCC BW tS IS+(O), IS-(O) ICC(O) SR ISC VO(MIN) VO(MAX) PARAMETER VS Sense Input Common Mode Rejection Ratio VCC Supply Rejection Ratio Supply Voltage VCC Bandwidth Output Settling to 1% Final Value Sense Input Current Supply Current Slew Rate Short-Circuit Current Reverse VS Supply Minimum Output Voltage Output High AV = 10V/V, fO = -3dB AV = 50V/V, fO = -3dB VSENSE = 10mV to 100mV VSENSE = 0V VSENSE = 0V, VCC = 5V VCC = 15V, VSENSE = 50mV to 300mV, AV = 50V/V

CONDITIONS VSENSE = 50mV, VCC = 2.7V, VS = 4.1V to 36V
MIN 105 100 105 95 2.7 100 20
TYP 120 120 120 120
MAX
UNITS dB dB dB dB
VSENSE = 50mV, VS = 36V, VCC = 3V to 30V
36 150 50 15 4.5 60 10 170
V kHz kHz s A A V/s V/s mA V
0.03 0.02 8 50
0.05 0.05 15 60 15 15 75 85 125 175 0.001 35 25 140 160 250 400 1
ISC+, ISC- IS = -100A VSENSE = 0V, No Load VSENSE = VS+ - VS- = -100mV, AV = 50V/V, No Load VCC = 5V, AV = 50V/V, VSENSE = 100mV, IL = 0 VSENSE = 100mV, IL = 100A VSENSE = 100mV, IL = 500A VSENSE = 100mV, IL = 1mA

mV mV mV mV mV mV A
IS+, IS- (Off) Sense Input Current (Power Down) VCC = 0V, VS = 48V, VSENSE = 0V Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: ESD (Electrostatic Discharge) sensitive devices. Extensive use of ESD protection devices are used internal to the LT6100, 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 LT6100C/LT6100I are guaranteed functional over the operating temperature range of -40C to 85C. The LT6100H is guaranteed functional over the operating temperature range of -40C to 125C.
Note 5: The LT6100C is guaranteed to meet specified performance from 0C to 70C. The LT6100C is designed, characterized and expected to meet specified performance from -40C to 85C but is not tested or QA sampled at these temperatures. The LT6100I is guaranteed to meet specified performance from -40C to 85C. The LT6100H is guaranteed to meet specified performance from -40C to 125C. Note 6: This parameter is not 100% tested. Note 7: Gain error for AV = 12.5, 25V/V is guaranteed by other gain error test.
6100f
5
LT6100 TYPICAL PERFOR A CE CHARACTERISTICS
Input Offset Voltage vs Temperature
400 300 INPUT OFFSET VOLTAGE (V) 200 100 0 -100 9 TYPICAL UNITS VS = 6.4V VCC = 5V
1.5 1.0
INPUT OFFSET VOLTAGE (mV)
INPUT OFFSET VOLTAGE (V)
-200 -300
- 400 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
6100 G21
Output Voltage vs Sense Voltage
1.8 1.6 1.4 VS+ = 4.4V TO 48V VCC = 3V AV = 10V/V TA = -40C TO 125C TA = -40C VS > 4.6V TA = -40C VS = 4.4V
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
1.2 1.0 0.8 0.6 0.4 0.2
2.0 1.5 1.0 0.5 0
GAIN (V/V)
0 -150
-90 -30 30 90 SENSE VOLTAGE (VS+ - VS-)(mV)
Negative Sense Input Current vs Sense Voltage
12
NEGATIVE SENSE INPUT CURRENT (A)
POSITIVE SENSE INPUT CURRENT (A)
VS+ = 4.4V TO 48V VCC = 3V
TA = 125C 25 20 15 TA = -40C 10 5 0 -5 -110 110 -70 -30 30 70 SENSE VOLTAGE (VS+ - VS-) (mV)
6100 G07
OUTPUT POSITIVE SWING (mV)
10 8 6 4 2 0 TA = 125C TA = 85C TA = 25C TA = -40C
-110
30 70 110 -70 -30 SENSE VOLTAGE (VS+ - VS-) (mV)
6100 G06
6
UW
6100 G03
Input Offset Voltage vs VS+ Input Voltage
VSENSE = 100mV VCC = 3V TA = -40C TA = 25C
Input Offset Voltage vs VCC Supply Voltage
350 300 250 200 150 100 TA = 125C 50 0 TA = 85C TA = 25C TA = -40C VSENSE = 100mV VS+ = 48V
0.5 0 -0.5 -1.0 -1.5 -2.0 -2.5 -3.0 -3.5 0
TA = 125C
TA = 85C
10
20
30
40
50
6100 G01
0
5
VS+ INPUT VOLTAGE (V)
10 15 20 25 30 VCC SUPPLY VOLTAGE (V)
35
40
6100 G02
Output Voltage vs Sense Voltage
3.5 3.0 2.5 TA = -40C VS = 6.4V VS+ = 6.4V TO 48V VCC = 5V TA = -40C TO 125C
50.06
Gain vs Temperature
50.04 50.02 50.00 49.98 49.96 49.94 49.92 49.90 7 TYPICAL UNITS VSENSE = 50mV TO 80mV VS+ = 6.4V TO 48V VCC = 5V AV = 50V/V
TA = -40C VS > 6.6V
150
0
300 180 240 120 60 SENSE VOLTAGE (VS+ - VS-) (mV)
6100 G04
49.88 -40 -25 -10 5 20 35 50 65 80 95 110 125 TEMPERATURE (C)
6100 G05
Positive Sense Input Current vs Sense Voltage
35 30 VS+ = 4.4V TO 48V VCC = 3V TA = 85C TA = 25C
Output Positive Swing vs Load Current
350 300 250 200 150 TA = 25C 100 TA = -40C 50 0 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 LOAD CURRENT (mA)
6100 G08
VS+ = 6.4V VCC = 5V VSENSE = 150mV AV = 50V/V TA = 85C
TA = 125C
6100f
LT6100 TYPICAL PERFOR A CE CHARACTERISTICS
VCC Supply Current vs VS Input Voltage
200 VSENSE = 0V 180 VCC = 3V
OUTPUT IMPEDANCE ()
10k
VCC SUPPLY CURRENT (A)
160 140 120 100 80 60 40 20 0 0
TA = 125C TA = 85C TA = 25C TA = -40C
GAIN (dB)
10 30 40 20 TOTAL VS INPUT VOLTAGE (V)
CMRR vs Frequency
140 120 VS = 6.4V VCC = 5V 150 130 110 90 70 50 30 10 10 100 1k 10k FREQUENCY (Hz) 100k 1M
6100 G11
80 60 40 20 0
VCC PSRR (dB)
100
GAIN ERROR (%)
CMRR (dB)
Sense Input Current (VCC Powered Down) vs VS+
10 VS+ = VS- TA = 125C 1
TOTAL INPUT CURRENT (IS+ + IS- ) (nA)
TA = 85C 0.1
0.01
TA = 25C TA = -40C 0 10 20 30 VS+ (V) 40 50
6100 G25
0.001
UW
6100 G09
Op Amp Output Impedance vs Frequency
VS+, VS- = 6.5V VCC = 5V VEE = -5V FIL = 0V 50 40 30 20 100 G2 = 5V/V 10 G2 = 2V/V G2 = 1V/V 1 10 0 -10 -20 -30 -40
Gain vs Frequency
AV = 50 AV = 10 VS = 12.1V VCC = 10V
1k
50
0.1 1k 10k 100k 1M
6100 G23
-50 100
1k
FREQUENCY (Hz)
10k 100k FREQUENCY (Hz)
1M
10M
6100 G10
VCC PSRR vs Frequency
VS = 10V VSENSE = 100mV VCC = 5V 1
Gain Error vs VSENSE
0
-1
-2
-10 0.1
-3 1 10 100 1k 10k 100k FREQUENCY (Hz) 1M 0 50 100 150 200 VSENSE (mV)
VS+ = 6.4V VCC = 5V AV = 10V/V TA = 25C 250 300
6100 G24
6100 G12
Step Response at VSENSE = 0V to 130mV
130mV VSENSE 0V
6.5V 130mV VSENSE 0V
Step Response at VSENSE = 0V to 130mV
1.3V VOUT 0V VS = 10V AV = 10V/V CL = 0pF 50s/DIV
6100 G13
VOUT 0V VS = 10V AV = 50V/V CL = 0pF 0.2ms/DIV
6100 G14
6100f
7
LT6100 TYPICAL PERFOR A CE CHARACTERISTICS
Step Response at VSENSE = 0V to 10mV
20mV VSENSE 0V
VSENSE 20mV 0V
100mV VOUT 0V VS = 10V AV = 10V/V COUT = 0pF 50s/DIV
6100 G15
Step Response at VSENSE = 0V to 130mV
130mV VSENSE 0V 6.5V VOUT 0V VS = 10V AV = 50V/V CL = 1000pF 0.2ms/DIV
6100 G18
Step Response at VSENSE = 0V to 10mV
20mV VSENSE 0V
500mV VOUT 0V VS = 10V AV = 50V/V CL = 1000pF 50s/DIV
6100 G20
8
UW
Step Response at VSENSE = 0V to 10mV
130mV VSENSE 0V
500mV VOUT 0V VS = 10V AV = 50V/V CL = 0pF 50s/DIV
6100 G16
Step Response at VSENSE = 0V to 130mV
1.3V VOUT 0V VS = 10V AV = 10V/V COUT = 1000pF 50s/DIV
6100 G17
Step Response at VSENSE = 0V to 10mV
20mV VSENSE 0V
100mV VOUT 0V VS = 10V AV = 10V/V CL = 1000pF 50s/DIV
6100 G19
Start-Up Delay
VS+
10V 0V
1V VOUT 0V VCC = 5V 20s/DIV VSENSE = 100mV AV = 10V/V VEE = 0V
6100 G22
6100f
LT6100
PI FU CTIO S
VS - (Pin 1): Negative Sense Input Terminal. Negative sense voltage input will remain functional for voltages up to 48V. VS - is connected to an internal gain-setting resistor RG2 = 5k. VCC (Pin 2): Supply Voltage Input. This power supply pin supplies current to both current sense amplifier and op amp. FIL (Pin 3): Filter Pin. Connects to an external capacitor to roll off differential noise of the system. Pole frequency f- 3dB = 1/(2RFILC), RFIL = RE + RO = 60k. VEE (Pin 4): Negative Supply or Ground for Single Supply Operation. VOUT (Pin 5): Voltage Output Proportional to the Magnitude of the Current Flowing Through RSENSE: VOUT = AV * (VSENSE VOS) VOS is the input offset voltage. AV is the total gain of the LT6100. A2 (Pin 6): Gain Select Pin. Refer to Table 1. A4 (Pin 7): Gain Select Pin. When Pin 7 is shorted to VEE, the total gain is 40V/V. When both Pin 6 and Pin 7 are shorted to VEE, the total gain is 50V/V. When both Pin 6 and Pin 7 are opened, the total gain is 10V/V. VS+ (Pin 8): Positive Sense Input Terminal. Connecting a supply to VS+ and a load to VS- will allow the LT6100 to monitor the current through RSENSE, refer to Figure 1. VS+ is connected to an internal gain setting resistor RG1 = 5k. VS+ remains functional for voltages up to 48V.
FU CTIO AL DIAGRA
LOAD 1
-
A1 VCC 2.7V TO 36V 2
VO1 RO 50k VEE 4 3 FIL 6
R A2 7
R/3 A4
6100 F01
Figure 1. Functional Diagram
+
Q1 RE 10k
-
W
U
U
U
U
U
RSENSE
VIN (VCC + 1.4V) TO 48V 8 VS+ RG2 5k
VS- RG1 5k
+
R 25k
A2
VOUT
5
6100f
9
LT6100
APPLICATIO S I FOR ATIO
The LT6100 high side current sense amplifier (Figure 1) provides accurate unidirectional monitoring of current through a user-selected sense resistor. The LT6100 features a fully specified 4.1V to 48V input common mode range. A high PSRR VCC supply (2.7V to 36V) powers the current sense amplifier and the internal op amp circuitry. The input sense voltage is level shifted from the positive sense power supply to the ground reference and amplified by a user-selected gain to the output. The buffered output voltage is directly proportional to the current flowing through the sense resistor. Theory of Operation (Refer to Figure 1) 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 RG2. The opposite ends of resistors RG1 and RG2 are forced to be at equal potentials by the voltage gain of amplifier A1. The current through RG2 is forced to flow through transistor Q1 and is sourced to node VO1. The current from RG2 flowing through resistor RO gives a voltage gain of ten, VO1/VSENSE = RO/RG2 = 10V/V. The sense amplifier output at VO1 is amplified again by amplifier A2. The inputs of amplifier A2 can operate to ground which ensures that small sense voltage signals are detected. Amplifier A2 can be programmed to different gains via Pin 6 and Pin 7. Thus, the total gain of the system becomes AV = 10 * A2 and VOUT = VSENSE * AV. Gain Setting The LT6100 gain is set by strapping (or floating) the two gain pins (see Table 1). This feature allows the user to "zoom in" by increasing the gain for accurate measurement of low currents. AV = 10V/V * G2, G2 is the gain of op amp A2.
10
U
Table 1. Gain Set with Pin 6 and Pin 7
A2 (PIN 6) Open VEE VEE Out Open VEE A4 (PIN 7) Open Out Open VEE VEE VEE G2 1 1.25 2 2.5 4 5 AV 10 12.5 20 25 40 50
W
UU
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. The maximum sense voltage may be as large as 300mV to get maximum dynamic range. For high current applications, the user may want to minimize the sense voltage to minimize the power dissipation in the sense resistor. The LT6100's low input offset voltage of 80V allows for high resolution of low sense voltages. This allows limiting the maximum sense voltage while still providing high resolution current monitoring. Kelvin connection of the LT6100's VS+ and VS- inputs to the sense resistor should be used to provide the highest accuracy in high current applications. Solder connections and PC board interconnect resistance (approximately 0.5m per square) can be a large error in high current systems. A 5A application might choose a 20m sense resistor to give a 100mV full-scale input to the LT6100. Input offset voltage will limit resolution to 4mA. 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.
6100f
LT6100
APPLICATIO S I FOR ATIO
Noise Filtering
The LT6100 provides signal filtering via pin FIL that is internally connected to the resistors RE and RO. This pin may be used to filter the input signal entering the LT6100's internal op amp, and should be used when fast ripple current or transients flow through the sense resistor. High frequency signals above the 300kHz bandwidth of the LT6100's internal amplifier will cause errors. A capacitor connected between FIL and VEE creates a single pole low pass filter with corner frequency: f -3dB = 1/(2RFILC) where RFIL = 60k. A 220pF capacitor creates a pole at 12kHz, a good choice for many applications. Output Signal Range The LT6100's output signal is developed by current through RG2 into output resistor RO. The current is VSENSE/RG2. The sense amplifier output, VO1, is buffered by the internal op amp so that connecting the output pins to other systems will preserve signal accuracy. For zero VSENSE, internal circuit saturation with loss of accuracy occurs at the minimum VOUT swing, 15mV above VEE. VOUT may swing positive to within 0.75V of VCC or a maximum of 36V, a limit set by internal junction breakdown. Within
1.5 1.0
INPUT OFFSET VOLTAGE (mV)
0.5 0 -0.5 -1.0 -1.5 -2.0 -2.5 -3.0 -3.5 0 10
VSENSE = 100mV VCC = 3V TA = 25C
3
FIL
4
VEE LT6100
40 30 20 VS INPUT VOLTAGE (V)
50
6100 F02
Figure 2. VOS vs VS Input Voltage
Figure 3. Current Monitoring of a Fuse Protected Circuit
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these constraints, an amplified, level shifted representation of the RSENSE voltage is developed at VOUT. The output is well behaved driving capacitive loads to 1000pF. Sense Input Signal Range The LT6100 has high CMRR over the wide input voltage range of 4.1V to 48V. The minimum operation voltage of the sense amplifier input is 1.4V above VCC. The output remains accurate even when the sense inputs are driven to 48V. Figure 2 shows that VOS changes very slightly over a wide input range. Furthermore, the sense inputs VS+ and VS- can collapse to zero volts without incurring any damage to the device. The LT6100 can handle differential sense voltages up to the voltage of the sense inputs supplies. For example, VS+ = 48V 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 LT6100 goes to the positive rail, VOH. There is no phase inversion to cause an erroneous output signal. For the opposite case when VS+ collapse to ground with VS- held up at some higher voltage potential, the output will sit at VOL. If both inputs fall below the minimum CM voltage, VCC + 1.4V, the output is indeterminate but the LT6100 will not be damaged.
TO LOAD RSENSE FUSE 1 VS 2
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8 VS
+
C1 0.1F 7
DC SOURCE
+
5V
VCC
A4
C2 0.1F
A2
6
OUT
5
OUTPUT
6100 F03
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LT6100
APPLICATIO S I FOR ATIO
Low Sense Voltage Operation
Figure 4 shows the simplest circuit configuration in which the LT6100 may be used. While VOUT (output voltage) increases with positive sense current, at V SENSE = 0V, the LT6100's buffered output can only swing as low
TO LOAD RSENSE 1 VS 2
-
8 VS
+
OUTPUT VOLTAGE (V)
C1 0.1F 7
+
3V
VCC
A4
3
FIL
4
VEE LT6100
Figure 4. LT6100 Load Current Monitor
0.40 0.35
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
0.30 0.25 0.20 0.15 0.10 0.05 0 0
VS = 4.4V TO 48V VCC = 3V AV = 10V/V TA = 25C
20 25 15 SENSE VOLTAGE (VS+ - VS-) (mV)
5
10
Figure 6. Expanded View of Output Voltage vs VSENSE, AV = 10V/V
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+
-
C2 0.1F
A2
6
OUT
5
OUTPUT
6100 F04
30
6100 F06
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as VOL = 15mV. The accuracy at small sense voltages can be improved by selecting higher gain. When gain of 50V/ V is selected, as shown in Figure 7, VOUT leaves the clipped region for a positive VSENSE greater than 1mV compared to 2.5mV for gain of 10V/V (see Figure 6).
1.6 1.4 VS = 4.4V TO 48V VCC = 3V AV = 10V/V TA = 25C
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5V
1.2 1.0 0.8 0.6 0.4 0.2 0 0
30 60 120 90 SENSE VOLTAGE (VS+ - VS-) (mV)
150
6100 F05
Figure 5. Output Voltage vs VSENSE
1.8 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 0
VS = 4.4V TO 48V VCC = 3V AV = 50V/V TA = 25C
10 15 5 20 25 SENSE VOLTAGE (VS+ - VS-) (mV)
30
6100 F07
Figure 7. Expanded View of Output Voltage vs VSENSE, AV = 50V/V
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LT6100
APPLICATIO S I FOR ATIO
Power Down While Connected to a Battery
Another unique benefit of the LT6100 is that you can leave it connected to a battery even when it is denied power. When the LT6100 loses power or is intentionally powered down, its inputs remain high impedance (see Figure 8).
RSENSE TO LOAD
- LT6100 VS
VCC FIL VOUT VEE A2 A4
6100 F08
Figure 8. Input Remains Hi-Z when LT6100 is Powered Down
TYPICAL APPLICATIO
Adjust Gain Dynamically for Enhanced Range
RSENSE TO LOAD
- LT6100 VS
ISENSE FROM SOURCE VS+
5V
VCC FIL VOUT VEE A2 A4
6100 TA05
5V
VCC VEE LT6100 A2 A4
MICRO-HOTPLATE BOSTON MICROSYSTEMS MHP100S-005
2N7002 0V (GAIN = 10)
5V (GAIN = 50)
5V
M9 M3 M1 LT1991 P1 P3 P9 VDR- www.bostonmicrosystems.com
6100 TA06
+-
+
-
POWER DOWN OK VCC 3V 0V INPUTS REMAIN Hi-Z
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This is due to the implementation of Linear Technology's Over-The-Top(R) input topology at its front end. When powered down, the LT6100 inputs draw less than 1A of current.
Over-The-Top is a registered trademark of Linear Technology Corporation.
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ISENSE
VS+
+
BATTERY 4.1V TO 48V
Micro-Hotplate Voltage and Current Monitor
VDR+
10 1% IHOTPLATE
VS-
VS+
-
CURRENT MONITOR VOUT = 500mV/mA
5V
VOLTAGE MONITOR V + - VDR- VOUT = DR 10
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LT6100
PACKAGE DESCRIPTIO
3.5 0.05 1.65 0.05 2.15 0.05 (2 SIDES) PACKAGE OUTLINE 0.25 0.05 0.50 BSC 2.38 0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS R = 0.115 TYP 5 0.38 0.10 8
PIN 1 TOP MARK (NOTE 6)
(DD8) DFN 1203
0.200 REF
NOTE: 1. DRAWING TO BE MADE A JEDEC PACKAGE OUTLINE M0-229 VARIATION OF (WEED-1) 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 TOP AND BOTTOM OF PACKAGE
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DD Package 8-Lead Plastic DFN (3mm x 3mm)
(Reference LTC DWG # 05-08-1698)
0.675 0.05 3.00 0.10 (4 SIDES) 1.65 0.10 (2 SIDES) 0.75 0.05 4 0.25 0.05 2.38 0.10 (2 SIDES) BOTTOM VIEW--EXPOSED PAD 1 0.50 BSC 0.00 - 0.05
6100f
LT6100
PACKAGE DESCRIPTIO
5.23 (.206) MIN
0.42 0.038 (.0165 .0015) TYP
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
0.18 (.007) SEATING PLANE 0.22 - 0.38 (.009 - .015) TYP 0.127 0.076 (.005 .003)
MSOP (MS8) 0204
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
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.
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MS8 Package 8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
0.889 0.127 (.035 .005)
3.20 - 3.45 (.126 - .136)
0.65 (.0256) BSC
3.00 0.102 (.118 .004) (NOTE 3)
8
7 65
0.52 (.0205) REF
0.53 0.152 (.021 .006) DETAIL "A"
1 1.10 (.043) MAX
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4 0.86 (.034) REF
0.65 (.0256) BSC
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LT6100
TYPICAL APPLICATIO
VIN 3.3V TO 4.2V SINGLE Li-Ion
SHDN LED ON 4.7F 6.3V CER GND
FB VC 124k
VOUT VEE A4 A2 OPEN: 1A CLOSED: 800mA
6100 TA02
MMBT2222 8.2k 0.1F 4.99k D1: DIODES INC. D2: LUMILEDS LXML-PW09 WHITE EMITTER L1: SUMIDA CDRH6D28-3R0
Filtered Gain of 20 Current Sense
ISENSE VSUPPLY 4.4V TO 48V RSENSE VS-
Gain of 50 Current Sense
ISENSE VSUPPLY 6.4V TO 48V
LOAD
+ LT6100 VS
+ LT6100 VS
3V
VCC FIL
5V
VCC FIL
1000pF VEE A2 A4
VOUT 20 * RSENSE * ISENSE
6100 TA03
VEE
A2
-3dB AT 2.6kHz
RELATED PARTS
PART NUMBER LTC1043 LT1490/LT1491 LT1620/LT1621 LT1787 LTC6101 DESCRIPTION Dual Precision Instrumentation Switched Capacitor Building Block Dual and Quad Micropower Rail-to-Rail Input and Output Op Amps Rail-to-Rail Current Sense Amplifiers Precision Bidirectional, High Side Current Sense Amplifier High Voltage, High Side, Precision Current Sense Amplifier COMMENTS 120dB CMRR, 3V to 18V Operation 50A Amplifier, 2.7V to 40V Operation, Over-The-TopTM Inputs Accurate Output Current Programming, Battery Charging to 32V 75V VOS, 60V, 60A Operation 4V to 60V, Gain Configurable, SOT-23
Over-The-Top is a trademark of Linear Technology Corporation.
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Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 FAX: (408) 434-0507
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2005
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800mA/1A White LED Current Regulator
D2 LED L1 3H LED CURRENT WARNING! VERY BRIGHT DO NOT OBSERVE DIRECTLY D1 B130 0.030 VS+ LT6100 VS- VCC 22F 16V CER 1210 VIN VSW LT3436
RSENSE VS- LOAD A4 VOUT 50 * RSENSE * ISENSE
6100 TA04
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+
6100f LT/TP 0405 500 * PRINTED IN THE USA

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