LT6107

LT6107 High Temperature High Side Current Sense Amp in SOT-23 FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION The LT®6107 is a versatile high side current sense amplifier designed for operation over a wide temperature range. Design flexibility is provided by the excellent device characteristics: 250μV maximum offset and 40nA maximum input bias current. Gain for each device is set by two resistors and allows for accuracy better than 1%. The LT6107 monitors current via the voltage across an external sense resistor (shunt resistor). Internal circuitry converts input voltage to output current, allowing for a small sense signal on a high common mode voltage to be translated into a ground referenced signal. The low DC offset allows for monitoring very small sense voltages. As a result, a small valued shunt resistor can be used, which minimizes the power loss in the shunt. The wide 2.7V to 44V input voltage range, high accuracy and wide operating temperature range make the LT6107 ideal for automotive, industrial and power management applications. The very low power supply current of the LT6107 also makes it suitable for low power and battery operated applications. For applications not requiring the wide temperature range, see the LT6106. Fully Tested at –55°C, 25°C and 150°C Gain Configurable with Two Resistors Low Offset Voltage: 250μV Maximum Output Current: 1mA Maximum Supply Range: 2.7V to 36V, 44V Absolute Maximum Low Input Bias Current: 40nA Maximum PSRR: 106dB Minimum Low Supply Current: 65μA Typical, V+ = 12V Low Profile (1mm) ThinSOTTM Package APPLICATIONS ■ ■ ■ ■ ■ ■ Current Shunt Measurement Battery Monitoring Power Management Motor Control Lamp Monitoring Overcurrent and Fault Detection , LT, LTC and LTM are registered trademarks of Linear Technology Corporation. ThinSOT is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATION 3V to 36V, 5A Current Sense with AV = 10 3V TO 36V Measurement Accuracy vs Load Current 0.6 0.4 ACCURACY (% OF FULL SCALE) 100Ω 0.02Ω +IN LOAD V– –IN 0.2 0 –0.2 –0.4 –0.6 –0.8 –1.0 5A FULL SCALE RSENSE = 0.02 ROUT = 1k AV = 10 RIN = 100 V+ = 3V 0 1 3 2 LOAD CURRENT (A) 4 5 6107 TA01b TYPICAL PART, TA = 25°C LT6107 – V+ OUT 1k 6107 TA01a + VOUT 200mV/A –1.2 6107fb 1 LT6107 ABSOLUTE MAXIMUM RATINGS Supply Voltage (V+ to V–)..........................................44V Input Voltage (+IN to V–) ............................................ V+ (–IN to V–) ............................................ V+ Input Current........................................................–10mA Output Short-Circuit Duration .......................... Indefinite Operating Temperature Range (Note 2) ............................................. –55°C to 150°C Specified Temperature Range (Note 2) ............................................. –55°C to 150°C Storage Temperature Range................... –65°C to 150°C Lead Temperature (Soldering, 10 sec) .................. 300°C (Note 1) PIN CONFIGURATION TOP VIEW OUT 1 V– 2 –IN 3 4 +IN 5 V+ S5 PACKAGE 5-LEAD PLASTIC TSOT-23 TJMAX = 150°C, θJA = 250°C/W ORDER INFORMATION Lead Free Finish TAPE AND REEL (MINI) LT6107MPS5#TRMPBF TAPE AND REEL LT6107MPS5#TRPBF PART MARKING LTDGZ PACKAGE DESCRIPTION 5-Lead Plastic TSOT-23 TEMPERATURE RANGE –55°C to 150°C TEMPERATURE RANGE –55°C to 150°C Lead Based Finish TAPE AND REEL (MINI) TAPE AND REEL PART MARKING PACKAGE DESCRIPTION LT6107MPS5#TRM LT6107MPS5#TR LTDGZ 5-Lead Plastic TSOT-23 TRM = 500 pieces. 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/ ELECTRICAL CHARACTERISTICS SYMBOL V+ VOS ΔVOS/ΔT IB IOS IOUT PSRR VSENSE(MAX) AV Error VOUT(HIGH) PARAMETER Supply Voltage Range Input Offset Voltage Input Offset Voltage Drift Input Bias Current (+IN) Input Offset Current Maximum Output Current Power Supply Rejection Ratio Input Sense Voltage Full Scale Gain Error (Note 4) Output Swing High (Referred to V+) The ● denotes the specifications which apply over the full specified operating temperature range, otherwise specifications are at TA = 25°C. V+ = 12V, V+ = VSENSE+, RIN = 100Ω, ROUT = 10k, Gain = 100 unless otherwise noted. (Note 6) CONDITIONS ● MIN 2.7 TYP 150 MAX 36 250 400 40 130 UNITS V μV μV μV/°C nA nA nA mA dB V VSENSE = 5mV VSENSE = 5mV V+ = 12V, 36V ● ● ● 1 V+ = 12V, 36V (Note 3) V+ = 2.7V to 36V, V SENSE = 5mV 1 ● ● ● ● ● ● 1 106 0.5 –0.65 –0.45 –0.25 –0.14 0 0.1 1.2 1.4 RIN = 500Ω (Notes 3, 7) VSENSE = 500mV, RIN = 500Ω, ROUT = 10k, V+ = 12.5V VSENSE = 500mV, RIN = 500Ω, ROUT = 10k, V+ = 36V VSENSE = 120mV % % V V 6107fb 2 LT6107 ELECTRICAL CHARACTERISTICS SYMBOL PARAMETER Minimum Output Voltage (Note 5) CONDITIONS VSENSE = 0mV, RIN = 100Ω, ROUT = 10k VSENSE = 0mV, RIN = 500Ω, ROUT = 10k, V+ = 12V, 36V BW tr IS Signal Bandwidth (–3dB) IOUT = 1mA, RIN = 100Ω, ROUT = 5k ● The ● denotes the specifications which apply over the full specified operating temperature range, otherwise specifications are at TA = 25°C. V+ = 12V, V+ = VSENSE+, RIN = 100Ω, ROUT = 10k, Gain = 100 unless otherwise noted. (Note 6) MIN TYP 12 7 ● MAX 45 85 16 40 UNITS mV mV mV mV kHz μs 200 3.5 60 ● Input Step Response (to 50% of ΔVSENSE = 100mV Step, RIN = 100Ω, ROUT = 5k, Output Step) Rising Edge Supply Current V+ = 2.7V, IOUT = 0μA, (VSENSE = – 5mV) V+ = 12V, IOUT = 0μA, (VSENSE = – 5mV) V+ = 36V, IOUT = 0μA, (VSENSE = – 5mV) 85 120 95 125 100 135 μA μA μA 65 ● 70 ● 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. In addition to the Absolute Maximum Ratings, the output current of the LT6107 must be limited to insure that the power dissipation in the LT6107 does not allow the die temperature to exceed 150°C. See the applications information section “Power Dissipation Considerations” for further information. Note 2: Junction temperatures greater than 125°C will promote accelerated aging. The LT6107 has demonstrated typical life beyond 1000 hours at 150°C. Note 3: Guaranteed by the gain error test. Note 4: Gain error refers to the contribution of the LT6107 internal circuitry and does not include errors in the external gain setting resistors. Note 5: The LT6107 output is an open collector current source. The minimum output voltage scales directly with the ratio ROUT/10k. Note 6: VSENSE+ is the voltage at the high side of the sense resistor, RSENSE. See Figure 1. Note 7: VSENSE(MAX) is the maximum sense voltage for which the Electrical Characteristics will apply. Higher voltages can affect performance but will not damage the part provided that the output current of the LT6107 does not exceed the allowable power dissipation as described in Note 1. TYPICAL PERFORMANCE CHARACTERISTICS VOS Distribution CHANGE IN INPUT OFFSET VOLTAGE (μV) 16 14 PERCENT OF UNITS (%) 12 10 8 6 4 2 0 –200 –120 120 –40 0 40 INPUT OFFSET VOLTAGE (μV) 200 6107 G23 Input Offset Voltage vs Supply Voltage 70 60 50 40 30 20 10 0 –10 –20 –30 –40 –50 –60 –70 0 VSENSE = 5mV RIN = 100Ω ROUT = 10k TYPICAL UNITS 600 500 INPUT OFFSET VOLTAGE (μV) 400 300 200 100 0 Input Offset Voltage vs Temperature VSENSE = 5mV V+ = 12V RIN = 100Ω ROUT = 10k AV = 100 TYPICAL UNITS V+ = 12V VSENSE = 5mV RIN = 100Ω ROUT = 10k 1068 UNITS –100 –200 –300 5 10 15 20 25 30 SUPPLY VOLTAGE (V) 35 40 –400 –55 –35 –15 5 25 45 65 85 105 125 145 165 TEMPERATURE (°C) 6107 G03 6107 G02 6107fb 3 LT6107 TYPICAL PERFORMANCE CHARACTERISTICS Gain Error vs Temperature 0.00 –0.05 –0.10 GAIN ERROR (%) –0.15 –0.20 –0.25 –0.30 –0.35 V+ = 2.7V V+ = 12V V+ = 5V V+ = 36V POWER SUPPLY REJECTION RATIO (dB) 120 110 100 90 80 70 60 50 40 30 20 10 0 100 VOUT = 0.5V VOUT = 1V VOUT = 2V 1k 10k 100k FREQUENCY (Hz) 1M 6107 G08 Power Supply Rejection Ratio vs Frequency POWER SUPPLY REJECTION RATIO (dB) V+ = 12.5V AV = 20 RIN = 100Ω ROUT = 2k 120 110 100 90 80 70 60 50 40 30 20 10 Power Supply Rejection Ratio vs Frequency V+ = 12.5V AV = 20 RIN = 500Ω ROUT = 10k VOUT = 1V –0.40 IOUT = 1mA ROUT = 1k –0.45 –60 –40 –20 0 20 40 60 80 100 120 140 160 180 TEMPERATURE (°C) 6107 G04 0 100 VOUT = 2.5V VOUT = 5V VOUT = 10V 1k 10k 100k FREQUENCY (Hz) 1M 6107 G06 Gain Error Distribution 24 22 20 PERCENT OF UNITS (%) 18 16 14 12 10 8 6 4 2 0 –0.60 –0.48 –0.36 –0.24 GAIN ERROR (%) –0.12 0 6107 G24 Gain vs Frequency 45 40 35 30 25 20 15 10 5 0 –5 –10 –15 –20 –25 –30 1k V+ = 12.5V VOUT = 10V VOUT = 2.5V AV = 100 RIN = 100Ω ROUT = 10k GAIN (dB) 45 40 35 30 25 20 15 10 5 0 –5 –10 –15 –20 –25 –30 Gain vs Frequency VOUT = 10V VOUT = 2.5V V+ = 12.5V AV = 20 RIN = 500Ω ROUT = 10k V+ = 12.5V VSENSE = 500mV RIN = 500Ω ROUT = 10k 11,072 UNITS TA = 25°C GAIN (dB) 10k 100k 1M FREQUENCY (Hz) 10M 6107 G09 1k 10k 100k 1M FREQUENCY (Hz) 10M 6107 G14 Input Bias Current vs Supply Voltage 300 280 260 240 220 200 180 160 140 120 100 80 60 40 20 0 0 VSENSE = 5mV RIN = 100Ω VSENSE 20mV/DIV Step Response 0mV to 10mV (RIN = 100Ω) VSENSE 20mV/DIV Step Response 10mV to 20mV (RIN = 100Ω) INPUT BIAS CURRENT (nA) TA = –55°C TA = –40°C TA = 25°C TA = 70°C TA = 125°C TA = 150°C TA = 175°C VOUT 500mV/DIV VOUT 500mV/DIV 0V AV = 100 VOUT = 0V TO 1V ROUT = 10k V+ = 12V 5μs/DIV 6107 G10 0V AV = 100 VOUT = 1V TO 2V ROUT = 10k V+ = 12V 5μs/DIV 6107 G11 5 10 15 20 25 30 35 40 45 50 SUPPLY VOLTAGE (V) 6107 G05 6107fb 4 LT6107 TYPICAL PERFORMANCE CHARACTERISTICS Step Response 0mV to 100mV (RIN = 100Ω) VSENSE 200mV/DIV VSENSE 200mV/DIV Step Response 10mV to 100mV (RIN = 100Ω) VSENSE 100mV/DIV Step Response 50mV to 100mV (RIN = 500Ω) VOUT 2V/DIV VOUT 2V/DIV VOUT 500mV/DIV 0V AV = 100 5μs/DIV VOUT = 0V TO 10V ROUT = 10k V+ = 12V 6107 G12 0V AV = 100 5μs/DIV VOUT = 1V TO 10V ROUT = 10k V+ = 12V 6107 G13 0V AV = 20 VOUT = 1V TO 2V ROUT = 10k V+ = 12V 5μs/DIV 6107 G15 Step Response 0mV to 50mV (RIN = 500Ω) VSENSE 100mV/DIV VSENSE 1V/DIV Step Response 50mV to 500mV (RIN = 500Ω) VSENSE 1V/DIV Step Response 0mV to 500mV (RIN = 500Ω) VOUT 2V/DIV VOUT 500mV/DIV 0V AV = 20 VOUT = 0V TO 1V ROUT = 10k V+ = 12V 5μs/DIV 6107 G16 VOUT 2V/DIV 0V AV = 20 5μs/DIV VOUT = 1V TO 10V ROUT = 10k V+ = 12V 6107 G17 0V AV = 20 5μs/DIV VOUT = 0V TO 10V ROUT = 10k V+ = 12V 6107 G18 Output Voltage Swing vs Temperature 11.15 11.10 OUTPUT VOLTAGE (V) 11.05 11.00 10.95 10.90 10.85 10.80 –60 –40 –20 0 20 40 60 80 100 120 140 160 180 TEMPERATURE (°C) 6107 G07 Output Voltage vs Input Sense Voltage (0mV ≤ VSENSE ≤ 10mV) 1100 1000 900 800 VOUT (mV) 700 600 500 400 300 200 100 0 0 1 2 3 4567 VSENSE (mV) 8 9 10 V+ = 12V AV = 100 RIN = 100Ω ROUT = 10k VOUT (mV) 220 200 180 160 140 120 100 80 60 40 20 0 Output Voltage vs Input Sense Voltage (0mV ≤ VSENSE ≤ 10mV) V+ = 12V AV = 20 RIN = 500Ω ROUT = 10k V+ = 12V AV = 100 RIN = 100Ω ROUT = 10k VSENSE = 120mV 0 1 2 3 4567 VSENSE (mV) 8 9 10 6107 G19 6107 G20 6107fb 5 LT6107 TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage vs Input Sense Voltage (0mV ≤ VSENSE ≤ 200mV) 12 10 8 VOUT (V) VOUT (V) 6 4 2 0 0 20 40 60 80 100 120 140 160 180 200 VSENSE (mV) 6107 G21 Output Voltage vs Input Sense Voltage (0mV ≤ VSENSE ≤ 1V) 12 10 8 6 4 2 0 0 100 200 300 400 500 600 700 800 900 1000 VSENSE (mV) 6107 G22 Supply Current vs Supply Voltage 120 100 SUPPLY CURRENT (μA) 80 60 40 20 0 0 5 10 TA = –55°C TA = –40°C TA = 25°C TA = 70°C TA = 125°C TA = 150°C TA = 175°C 15 20 25 30 35 SUPPLY VOLTAGE (V) 40 45 V+ = 12V AV = 100 RIN = 100Ω ROUT = 10k V+ = 12V AV = 20 RIN = 500Ω ROUT = 10k 6107 G01 PIN FUNCTIONS OUT (Pin 1): Current Output. OUT will source a current that is proportional to the sense voltage into an external resistor. V– (Pin 2): Normally Connected to Ground. –IN (Pin 3): The internal sense amplifier will drive –IN to the same potential as +IN. A resistor (RIN) tied from V+ to –IN sets the output current IOUT = VSENSE /RIN. VSENSE is the voltage developed across RSENSE. +IN (Pin 4): Must be tied to the system load end of the sense resistor, either directly or through a resistor. V+ (Pin 5): Positive Supply Pin. The V+ pin should be connected directly to either side of the sense resistor, RSENSE. Supply current is drawn through this pin. The circuit may be configured so that the LT6107 supply current is or is not monitored along with the system load current. To monitor only the system load current, connect V+ to the more positive side of the sense resistor. To monitor the total current, including that of the LT6107, connect V+ to the more negative side of the sense resistor. BLOCK DIAGRAM ILOAD – VSENSE RSENSE + 5 RIN V+ VBATTERY L O A D 3 4 Figure 1. LT6107 Block Diagram and Typical Connection 6107fb 6 + V– 2 OUT 1 6107 F01 +IN 14k – IOUT VOUT = VSENSE • ROUT ROUT RIN –IN 14k LT6107 APPLICATIONS INFORMATION Introduction The LT6107 high side current sense amplifier (Figure 1) provides accurate monitoring of current through a user-selected sense resistor. The sense voltage is amplified by a userselected gain and level shifted from the positive power supply to a ground-referred output. The output signal is analog and may be used as is, or processed with an output filter. Theory of Operation An internal sense amplifier loop forces –IN to have the same potential as +IN. Connecting an external resistor, RIN, between –IN and V+ forces a potential across RIN that is the same as the sense voltage across RSENSE. A corresponding current, VSENSE /RIN, will flow through RIN. The high impedance inputs of the sense amplifier will not conduct this current, so it will flow through an internal PNP to the output pin as IOUT. The output current can be transformed into a voltage by adding a resistor from OUT to V–. The output voltage is then VO = V– + IOUT • ROUT. Table 1. Useful Gain Configurations GAIN 20 50 100 GAIN 20 50 100 RIN 499Ω 200Ω 100Ω RIN 249Ω 100Ω 50Ω ROUT 10k 10k 10k ROUT 5k 5k 5k VSENSE at VOUT = 5V 250mV 100mV 50mV VSENSE at VOUT = 125mV 50mV 25mV IOUT at VOUT = 5V 500μA 500μA 500μA IOUT at VOUT = 2.5V 500μA 500μA 500μA must be small enough that VSENSE does not exceed the maximum input voltage specified by the LT6107, even under peak load conditions. As an example, an application may require that the maximum sense voltage be 100mV. If this application is expected to draw 2A at peak load, RSENSE should be no more than 50mΩ. Once the maximum RSENSE value is determined, the minimum sense resistor value will be set by the resolution or dynamic range required. The minimum signal that can be accurately represented by this sense amplifier is limited by the input offset. As an example, the LT6107 has a typical input offset of 150μV. If the minimum current is 20mA, a sense resistor of 7.5mΩ will set VSENSE to 150μV. This 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. Choosing a 50mΩ RSENSE will maximize the dynamic range and provide a system that has 100mV across the sense resistor at peak load (2A), while input offset causes an error equivalent to only 3mA of load current. Peak dissipation is 200mW. If a 5mΩ sense resistor is employed, then the effective current error is 30mA, while the peak sense voltage is reduced to 10mV at 2A, dissipating only 20mW. The low offset and corresponding large dynamic range of the LT6107 make it more flexible than other solutions in this respect. The 150μV typical offset gives 60dB of dynamic range for a sense voltage that is limited to 150mV maximum, and over 70dB of dynamic range if the rated input maximum of 0.5V is allowed. Sense Resistor Connection Kelvin connection of the –IN and +IN inputs to the sense resistor should be used in all but the lowest power applications. Solder connections and PC board interconnections that carry high current can cause significant error in measurement due to their relatively large resistances. One 10mm × 10mm square trace of one-ounce copper is approximately 0.5mΩ. A 1mV error can be caused by as little as 2A flowing through this small interconnect. This will cause a 1% error in a 100mV signal. A 10A load current in the same interconnect will cause a 5% error for the same 100mV signal. By isolating the sense traces from the high current paths, this error can be reduced 6107fb Selection of External Current Sense Resistor The external sense resistor, RSENSE, has a significant effect on the function of a current sensing system and must be chosen with care. First, the power dissipation in the resistor should be considered. 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 measured signal, and is limited primarily by input DC offset of the internal amplifier of the LT6107. In addition, RSENSE 7 LT6107 APPLICATIONS INFORMATION by orders of magnitude. A sense resistor with integrated Kelvin sense terminals will give the best results. Figure 2 illustrates the recommended method. V + This approach can be helpful in cases where occasional bursts of high currents can be ignored. Care should be taken when designing the board layout for RIN, especially for small RIN values. All trace and interconnect resistances will increase the effective RIN value, causing a gain error. Selection of External Output Resistor, ROUT RSENSE RIN +IN –IN LOAD V– LT6107 Figure 2. Kelvin Input Connection Preserves Accuracy with Large Load Currents Selection of External Input Resistor, RIN RIN should be chosen to allow the required resolution while limiting the output current to 1mA. In addition, the maximum value for RIN is 500Ω. 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. If low sense currents must be resolved accurately in a system that has a very wide dynamic range, a smaller RIN than the maximum current spec allows may be used if the maximum current is limited in another way, such as with a Schottky diode across RSENSE (Figure 3). This will reduce the high current measurement accuracy by limiting the result, while increasing the low current measurement resolution. V+ RSENSE 6107 F03 LOAD Figure 3. Shunt Diode Limits Maximum Input Voltage to Allow Better Low Input Resolution Without Overranging 8 – V+ OUT ROUT 6107 F02 + The output resistor, ROUT, determines how the output current is converted to voltage. VOUT is simply IOUT • ROUT. VOUT 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 enough 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 • Error Sources The current sense system uses an amplifier and resistors to apply gain and level shift the result. The output is then dependent on the characteristics of the amplifier, such as gain and input offset, as well as resistor matching. Ideally, the circuit output is: ROUT ; VSENSE = RSENSE • ISENSE RIN DSENSE VOUT = VSENSE • In this case, the only error is due to resistor mismatch, which provides an error in gain only. However, offset voltage and bias current cause additional errors. 6107fb LT6107 APPLICATIONS INFORMATION Output Error Due to the Amplifier DC Offset Voltage, VOS R EOUT( VOS) = VOS • OUT RIN The DC offset voltage of the amplifier adds directly to the value of the sense voltage, VSENSE. This is the dominant error of the system and it limits the low end of the dynamic range. The paragraph “Selection of External Current Sense Resistor” provides details. Output Error Due to the Bias Currents, IB+ and IB– The bias current IB+ flows into the positive input of the internal op amp. IB – flows into the negative input. EOUT(IBIAS) = ROUT IB + R • SENSE – IB – RIN RSENSE V+ RIN– RIN+ +IN –IN LOAD V– LT6107 RIN+ = RIN– – RSENSE Figure 4. Second Input R Minimizes Error Due to Input Bias Current Minimum Output Voltage The curves of the Output Voltage vs Input Sense Voltage show the behavior of the LT6107 with low input sense voltages. When VSENSE = 0V, the output voltage will always be slightly positive, the result of input offset voltages and of a small amount of quiescent current (0.7μA to 1.2μA) flowing through the output device. The minimum output voltage in the Electrical Characteristics table include both these effects. Power Dissipation Considerations The power dissipated by the LT6107 will cause a small increase in the die temperature. This rise in junction temperature can be calculated if the output current and the supply current are known. The power dissipated in the LT6107 due to the output signal is: POUT = (V–IN – VOUT) • IOUT Since V–IN ≅ V+, POUT ≅ (V+ – VOUT) • IOUT The power dissipated due to the quiescent supply current is: PQ = IS • (V+ – V–) The total power dissipated is the output dissipation plus the quiescent dissipation: PTOTAL = POUT + PQ The junction temperature is given by: TJ = TA + θJA • PTOTAL At the maximum operating supply voltage of 36V and the maximum guaranteed output current of 1mA, the total 6107fb Assuming IB+ ≅ IB – = IBIAS, and RSENSE