LT6106

LT6106 36V Low Cost High Side Current Sense in a SOT-23 FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION The LT®6106 is a versatile high side current sense amplifier. 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 LT6106 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 LT6106 ideal for automotive, industrial and power management applications. The very low power supply current of the LT6106 also makes it suitable for low power and battery operated applications. , 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. 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 Operating Temperature Range: –40°C to 125°C Low Profile (1mm) ThinSOTTM Package APPLICATIONS ■ ■ ■ ■ ■ ■ Current Shunt Measurement Battery Monitoring Power Management Motor Control Lamp Monitoring Overcurrent and Fault Detection 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) LIMIT OVER TEMPERATURE 100Ω 0.02Ω +IN LOAD V– –IN 0.2 0 –0.2 –0.4 –0.6 –0.8 LIMIT OVER TEMPERATURE TYPICAL PART AT TA = 25°C LT6106 – V+ OUT 1k 6106 TA01a + VOUT 200mV/A 5A FULL SCALE RIN = 100Ω –1.0 RSENSE = 0.02Ω ROUT = 1k AV = 10 V+ = 3V –1.2 0 1 3 2 LOAD CURRENT (A) 4 5 6106 TA01b 6106fa 1 LT6106 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 4) LT6106C............................................... –40°C to 85°C LT6106H ............................................ –40°C to 125°C Specified Temperature Range (Note 4) LT6106C................................................... 0°C to 70°C LT6106H ............................................ –40°C to 125°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) TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE 0°C to 70°C –40°C to 125°C LT6106CS5#TRMPBF LT6106CS5#TRPBF LTCWK 5-Lead Plastic TSOT-23 LT6106HS5#TRMPBF LT6106HS5#TRPBF LTCWK 5-Lead Plastic TSOT-23 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. Consult LTC Marketing for information on lead based finish parts. 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 3) Output Swing High (Referred to V+) CONDITIONS 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 150 MAX 36 250 350 40 65 UNITS V μV μV μV/°C nA nA nA mA dB V 2.7 VSENSE = 5mV VSENSE = 5mV V+ = 12V, 36V ● ● ● 1 V+ = 12V, 36V (Note 2) 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 2, 7) VSENSE = 500mV, RIN = 500Ω, ROUT VSENSE = 500mV, RIN = 500Ω, ROUT VSENSE = 120mV = 10k, V+ = 12.5V = 10k, V+ = 36V ● ● ● % % V V 6106fa 2 LT6106 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) Input Step Response (to 50% of Output Step) Supply Current IOUT = 1mA, RIN = 100Ω, ROUT = 5k ΔVSENSE = 100mV Step, RIN = 100Ω, ROUT = 5k, Rising Edge V+ = 2.7V, IOUT = 0μA, (VSENSE = –5mV) V+ = 12V, IOUT = 0μA, (VSENSE = –5mV) V+ = 36V, IOUT = 0μA, (VSENSE = –5mV) 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 LT6106 must be limited to insure that the power dissipation in the LT6106 does not allow the die temperature to exceed 150°C. See the applications information section “Power Dissipation Considerations” for further information. Note 2: Guaranteed by the gain error test. Note 3: Gain error refers to the contribution of the LT6106 internal circuitry and does not include errors in the external gain setting resistors. Note 4: The LT6106C is guaranteed functional over the operating temperature range of –40°C to 85°C. The LT6106C is designed, ● ● 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. MIN TYP 12 7 ● MAX 45 65 16 22 UNITS mV mV mV mV kHz μs 200 3.5 60 65 ● 85 115 95 120 100 130 μA μA μA 70 ● characterized and expected to meet specified performance from –40°C to 85°C but is not tested or QA sampled at these temperatures. The LT6106H is guaranteed to meet specified performance from –40°C to 125°C. Note 5: The LT6106 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 LT6106 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 6106 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 400 Input Offset Voltage vs Temperature VSENSE = 5mV ROUT = 10k + AV = 100 300 V = 12V TYPICAL UNITS RIN = 100Ω 200 100 0 –100 –200 –300 INPUT OFFSET VOLTAGE (μV) 40 V+ = 12V VSENSE = 5mV RIN = 100Ω ROUT = 10k 1068 UNITS 5 10 15 20 25 30 SUPPLY VOLTAGE (V) 35 –400 –55 –25 35 65 5 95 TEMPERATURE (°C) 125 6106 G03 6106 G02 6106fa 3 LT6106 TYPICAL PERFORMANCE CHARACTERISTICS Gain Error vs Temperature 0 –0.10 –0.15 GAIN ERROR (%) –0.20 –0.25 –0.30 –0.35 –0.40 –0.45 –0.50 –0.55 VOUT = 1V IOUT = 1mA ROUT = 1k TYPICAL UNIT 15 35 55 75 95 115 130 TEMPERATURE (°C) 6106 G04 Power Supply Rejection Ratio vs Frequency 120 POWER SUPPLY REJECTION RATIO (dB) POWER SUPPLY REJECTION RATIO (dB) 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 6106 G08 Power Supply Rejection Ratio vs Frequency 120 110 100 90 80 70 60 50 40 30 20 10 0 100 VOUT = 2.5V VOUT = 5V VOUT = 10V 1k 10k 100k FREQUENCY (Hz) 1M 6106 G06 –0.05 V+ = 36V V+ = 12V V+ = 5V V+ = 2.7V V+ = 12.5V AV = 20 RIN = 100Ω ROUT = 2k V+ = 12.5V AV = 20 RIN = 500Ω ROUT = 10k –0.60 –45 –25 –5 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 6106 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 6106 G09 1k 10k 100k 1M FREQUENCY (Hz) 10M 6106 G14 Input Bias Current vs Supply Voltage 20 VSENSE = 5mV 19 RIN = 100Ω INPUT BIAS CURRENT (nA) 18 17 16 15 14 13 12 11 10 0 5 TA = –40°C TA = 25°C TA = 70°C TA = 125°C 10 15 20 25 30 35 40 45 50 SUPPLY VOLTAGE (V) 6106 G05 Step Response 0mV to 10mV (RIN = 100Ω) VSENSE 20mV/DIV VSENSE 20mV/DIV Step Response 10mV to 20mV (RIN = 100Ω) VOUT 500mV/DIV VOUT 500mV/DIV 0V AV = 100 VOUT = 0V TO 1V ROUT = 10k V+ = 12V 5μs/DIV 6106 G1 0V AV = 100 VOUT = 1V TO 2V ROUT = 10k V+ = 12V 5μs/DIV 6106 G1 6106fa 4 LT6106 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 6106 G1 0V AV = 100 5μs/DIV VOUT = 1V TO 10V ROUT = 10k V+ = 12V 6106 G1 0V AV = 20 VOUT = 1V TO 2V ROUT = 10k V+ = 12V 5μs/DIV 6106 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 6106 G16 VOUT 2V/DIV 0V AV = 20 5μs/DIV VOUT = 1V TO 10V ROUT = 10k V+ = 12V 6106 G17 0V AV = 20 5μs/DIV VOUT = 0V TO 10V ROUT = 10k V+ = 12V 6106 G18 Output Voltage Swing vs Temperature 11.10 11.05 OUTPUT VOLTAGE (V) 11.00 10.95 10.90 10.85 10.80 –50 –25 V+ = 12V AV = 100 RIN = 100Ω ROUT = 10k VSENSE = 120mV 1100 1000 900 800 VOUT (mV) 700 600 500 400 300 200 100 50 25 75 0 TEMPERATURE (°C) 100 125 0 Output Voltage vs Input Sense Voltage (0mV ≤ VSENSE ≤ 10mV) V+ = 12V AV = 100 RIN = 100Ω ROUT = 10k VOUT (mV) 220 200 180 160 140 120 100 80 60 40 20 0 1 2 3 4567 VSENSE (mV) 8 9 10 0 Output Voltage vs Input Sense Voltage (0mV ≤ VSENSE ≤ 10mV) V+ = 12V AV = 20 RIN = 500Ω ROUT = 10k 0 1 2 3 4567 VSENSE (mV) 8 9 10 6106 G07 6106 G19 6106 G20 6106fa 5 LT6106 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) 6106 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) 6106 G22 Supply Current vs Supply Voltage 120 100 SUPPLY CURRENT (μA) 80 60 40 20 0 0 5 10 TA = –40°C TA = 25°C TA = 70°C TA = 125°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 6106 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 LT6106 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 LT6106, 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. LT6106 Block Diagram and Typical Connection 6106fa 6 + V– 2 OUT 1 6106 F01 +IN 14k – IOUT VOUT = VSENSE • ROUT ROUT RIN –IN 14k LT6106 APPLICATIONS INFORMATION Introduction The LT6106 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 IOUT at VOUT = 5V 250mV 500μA 100mV 500μA 50mV 500μA VSENSE at VOUT = 2.5V IOUT at VOUT = 2.5V 125mV 500μA 50mV 500μA 25mV 500μA must be small enough that VSENSE does not exceed the maximum input voltage specified by the LT6106, 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 LT6106 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 LT6106 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 by orders of 6106fa 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 LT6106. In addition, RSENSE 7 LT6106 APPLICATIONS INFORMATION 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– LT6106 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 6106 F03 LOAD Figure 3. Shunt Diode Limits Maximum Input Voltage to Allow Better Low Input Resolution Without Overranging 8 – V+ OUT ROUT 6106 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. 6106fa LT6106 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) ⎛ ⎞ R = ROUT ⎜IB + • SENSE – IB – ⎟ RIN ⎝ ⎠ RSENSE V+ RIN– RIN+ +IN –IN LOAD V– LT6106 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 LT6106 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 LT6106 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 LT6106 due to the output signal is: POUT = (VIN– – VOUT) • IOUT Since VIN– ≅ 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 6106fa Assuming IB+ ≅ IB– = IBIAS, and RSENSE