LTC6101/LTC6101HV High Voltage, High-Side Current Sense Amplifier in SOT-23 U FEATURES DESCRIPTIO ■ The LTC®6101/LTC6101HV are versatile, high voltage, high side current sense amplifiers. Design flexibility is provided by the excellent device characteristics; 300µV Max offset and only 375µA (typical at 60V) of current consumption. The LTC6101 operates on supplies from 4V to 60V and LTC6101HV operates on supplies from 5V to 100V. ■ ■ ■ ■ ■ ■ ■ ■ Supply Range: 5V to 100V, 105V Absolute Maximum (LTC6101HV) 4V to 60V, 70V Absolute Maximum (LTC6101) µV Max Low Offset Voltage: 300µ µs Response Time (0V to 2.5V on Fast Response: 1µ a 5V Output Step) Gain Configurable with 2 Resistors Low Input Bias Current: 170nA Max PSRR: 110dB Min 4V to 60V (LTC6101) 5V to 100V (LTC6101HV) Output Current: 1mA Max Low Supply Current: 250µA, VS = 14V Low Profile (1mm) SOT-23 (ThinSOTTM) Package The wide operating supply range and high accuracy make the LTC6101 ideal for a large array of applications from automotive to industrial and power management. A maximum input sense voltage of 500mV allows a wide range of currents to be monitored. The fast response makes the LTC6101 the perfect choice for load current warnings and shutoff protection control. With very low supply current, the LTC6101 is suitable for power sensitive applications. U APPLICATIO S ■ ■ ■ ■ The LTC6101 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. Low DC offset allows the use of a small shunt resistor and large gain-setting resistors. As a result, power loss in the shunt is reduced. Current Shunt Measurement Battery Monitoring Remote Sensing Power Management , LTC and LT 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. The LTC6101 is available in 5-lead SOT-23 and 8-lead MSOP packages. U TYPICAL APPLICATIO 16-Bit Resolution Unidirectional Output into LTC2433 ADC ILOAD VSENSE – RIN 100Ω 4 L O A D Step Response + VSENSE– 5V TO 105V ∆VSENSE– = 100mV 3 + – 2 5.5V 5V 5 5V 1 VOUT VOUT LTC6101HV ROUT 4.99k TA = 25°C V+ = 12V RIN = 100 ROUT = 5k VSENSE+ = V+ 1µF IOUT = 100µA TO µP LTC2433-1 0.5V 0V IOUT = 0 500ns/DIV 6101 TA01 VOUT = ROUT • VSENSE = 49.9VSENSE RIN 6101 TA01b 6101fa 1 LTC6101/LTC6101HV W W U W ABSOLUTE AXI U RATI GS (Note 1) Total Supply Voltage (V+ to V–) LTC6101 ............................................................. 70V LTC6101HV ...................................................... 105V Minimum Input Voltage (–IN Pin) ................... (V+ – 4V) Maximum Output Voltage (Out Pin) ........................... 9V Input Current ..................................................... ±10mA Output Short-Circuit Duration (to V–) ............. Indefinite Operating Temperature Range LTC6101C/LTC6101HVC .................... – 40°C to 85°C LTC6101I/LTC6101HVI ...................... – 40°C to 85°C LTC6101H/LTC6101HVH ................. – 40°C to 125°C Specified Temperature Range (Note 2) LTC6101C/LTC6101HVC ......................... 0°C to 70°C LTC6101I/LTC6101HVI ...................... – 40°C to 85°C LTC6101H/LTC6101HVH ................. – 40°C to 125°C Storage Temperature Range ................ – 65°C to 150°C Lead Temperature (Soldering, 10 sec)................. 300°C U W U PACKAGE/ORDER I FOR ATIO TOP VIEW TOP VIEW –IN NC NC OUT 1 2 3 4 8 7 6 5 OUT 1 +IN V+ NC V– 5 V+ V– 2 –IN 3 MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150°C, θJA = 300°C/ W 4 +IN S5 PACKAGE 5-LEAD PLASTIC TSOT-23 TJMAX = 150°C, θJA = 250°C/ W ORDER PART NUMBER MS8 PART MARKING* ORDER PART NUMBER S5 PART MARKING* LTC6101ACMS8 LTC6101AIMS8 LTC6101AHMS8 LTC6101HVACMS8 LTC6101HVAIMS8 LTC6101HVAHMS8 LTBSB LTBSB LTBSB LTBSX LTBSX LTBSX LTC6101BCS5 LTC6101CCS5 LTC6101BIS5 LTC6101CIS5 LTC6101BHS5 LTC6101CHS5 LTC6101HVBCS5 LTC6101HVCCS5 LTC6101HVBIS5 LTC6101HVCIS5 LTC6101HVBHS5 LTC6101HVCHS5 LTBND LTBND LTBND LTBND LTBND LTBND LTBSZ LTBSZ LTBSZ LTBSZ LTBSZ LTBSZ Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marketing: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grades and parametric grades are identified by a label on the shipping container. 6101fa 2 LTC6101/LTC6101HV ELECTRICAL CHARACTERISTICS (LTC6101) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C, RIN = 100Ω, ROUT = 10k, VSENSE+ = V+ (see Figure 1 for details), 4V ≤ VS ≤ 60V unless otherwise noted. SYMBOL PARAMETER VS Supply Voltage Range VOS Input Offset Voltage CONDITIONS MIN ● VSENSE = 5mV, Gain = 100, LTC6101A VSENSE = 5mV, Gain = 100, LTC6101AC, LTC6101AI VSENSE = 5mV, Gain = 100, LTC6101AH TYP 4 V ±85 ±300 ±450 ±535 µV µV µV ±150 ±450 ±810 µV µV ±400 ±1500 ±2500 µV µV ● VSENSE = 5mV, Gain = 100, LTC6101C ● ∆VOS/∆T Input Offset Voltage Drift VSENSE = 5mV, LTC6101A VSENSE = 5mV, LTC6101B VSENSE = 5mV, LTC6101C IB Input Bias Current RIN = 1M ±1 ±3 ±10 ● ● ● UNITS 60 ● ● VSENSE = 5mV, Gain = 100, LTC6101B MAX µV/°C µV/°C µV/°C 100 170 245 nA nA ±2 ±15 nA ● RIN = 1M ● VSENSE(MAX) Input Sense Voltage Full Scale VOS within Specification, RIN = 1k ● 500 PSRR VS = 6V to 60V, VSENSE = 5mV, Gain = 100 118 115 140 ● dB dB 110 105 133 ● dB dB 8 3 1 IOS Input Offset Current Power Supply Rejection Ratio VS = 4V to 60V, VSENSE = 5mV, Gain = 100 VOUT Maximum Output Voltage 12V ≤ VS ≤ 60V, VSENSE = 88mV VS = 6V, VSENSE = 330mV, RIN = 1k, ROUT = 10k VS = 4V, VSENSE = 550mV, RIN = 1k, ROUT = 2k ● ● ● VOUT (0) Minimum Output Voltage VSENSE = 0V, Gain = 100, LTC6101A VSENSE = 0V, Gain = 100, LTC6101AC, LTC6101AI VSENSE = 0V, Gain = 100, LTC6101AH ● ● VSENSE = 0V, Gain = 100, LTC6101B mV V V V 0 30 45 53.5 mV mV mV 0 45 81 mV mV 0 150 250 mV mV ● VSENSE = 0V, Gain = 100, LTC6101C ● IOUT Maximum Output Current 6V ≤ VS ≤ 60V, ROUT = 2k, VSENSE = 110mV, Gain = 20 VS = 4V, VSENSE = 550mV, Gain = 2, ROUT = 2k tr Input Step Response (to 2.5V on a 5V Output Step) ∆VSENSE = 100mV Transient, 6V ≤ VS ≤ 60V, Gain = 50 VS = 4V 1 1.5 µs µs BW Signal Bandwidth IOUT = 200µA, RIN = 100, ROUT = 5k IOUT = 1mA, RIN = 100, ROUT = 5k 140 200 kHz kHz IS Supply Current VS = 4V, IOUT = 0, RIN = 1M ● ● 1 0.5 mA mA 220 450 475 µA µA 240 475 525 µA µA 250 500 590 µA µA 375 640 690 720 µA µA µA ● VS = 6V, IOUT = 0, RIN = 1M ● VS = 12V, IOUT = 0, RIN = 1M ● VS = 60V, IOUT = 0, RIN = 1M LTC6101I, LTC6101C LTC6101H ● ● 6101fa 3 LTC6101/LTC6101HV ELECTRICAL CHARACTERISTICS (LTC6101HV) The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C, RIN = 100Ω, ROUT = 10k, VSENSE+ = V+ (see Figure 1 for details), 5V ≤ VS ≤ 100V unless otherwise noted. SYMBOL PARAMETER VS Supply Voltage Range VOS Input Offset Voltage CONDITIONS MIN TYP MAX 100 V VSENSE = 5mV, Gain = 100, LTC6101HVA VSENSE = 5mV, Gain = 100, LTC6101HVAC, LTC6101HVAI ● ● VSENSE = 5mV, Gain = 100, LTC6101HVAH ±85 ±300 ±450 ±535 µV µV µV VSENSE = 5mV, Gain = 100, LTC6101HVB ±150 ±450 ±810 µV µV ±400 ±1500 ±2500 µV µV ● 5 ● VSENSE = 5mV, Gain = 100, LTC6101HVC ● ∆VOS/∆T Input Offset Voltage Drift VSENSE = 5mV, LTC6101HVA VSENSE = 5mV, LTC6101HVB VSENSE = 5mV, LTC6101HVC IB Input Bias Current RIN = 1M ±1 ±3 ±10 ● ● ● UNITS µV/°C µV/°C µV/°C 100 170 245 nA nA ±2 ±15 nA ● RIN = 1M ● VSENSE(MAX) Input Sense Voltage Full Scale VOS within Specification, RIN = 1k ● 500 PSRR VS = 6V to 100V, VSENSE = 5mV, Gain = 100 140 ● 118 115 dB dB 110 105 133 ● dB dB 8 3 IOS Input Offset Current Power Supply Rejection Ratio VS = 5V to 100V, VSENSE = 5mV, Gain = 100 VOUT Maximum Output Voltage 12V ≤ VS ≤ 100V, VSENSE = 88mV 5V, VSENSE = 330mV, RIN = 1k, ROUT = 10k ● ● VOUT (0) Minimum Output Voltage VSENSE = 0V, Gain = 100, LTC6101HVA VSENSE = 0V, Gain = 100, LTC6101HVAC, LTC6101HVAI VSENSE = 0V, Gain = 100, LTC6101HVAH ● ● VSENSE = 0V, Gain = 100, LTC6101HVB mV V V 0 30 45 53.5 mV mV mV 0 45 81 mV mV 0 150 250 mV mV ● VSENSE = 0V, Gain = 100, LTC6101HVC ● IOUT Maximum Output Current 5V ≤ VS ≤ 100V, ROUT = 2k, VSENSE = 110mV, Gain = 20 tr Input Step Response (to 2.5V on a 5V Output Step) ∆VSENSE = 100mV Transient, 6V ≤ VS ≤ 100V, Gain = 50 VS = 5V 1 1.5 µs µs BW Signal Bandwidth IOUT = 200µA, RIN = 100, ROUT = 5k IOUT = 1mA, RIN = 100, ROUT = 5k 140 200 kHz kHz IS Supply Current VS = 5V, IOUT = 0, RIN = 1M ● 1 mA 200 450 475 µA µA 220 475 525 µA µA 230 500 590 µA µA 350 640 690 720 µA µA µA 350 640 690 720 µA µA µA ● VS = 6V, IOUT = 0, RIN = 1M ● VS = 12V, IOUT = 0, RIN = 1M ● VS = 60V, IOUT = 0, RIN = 1M LTC6101HVI, LTC6101HVC LTC6101HVH ● ● VS = 100V, IOUT = 0, RIN = 1M LTC6101HVI, LTC6101HVC LTC6101HVH ● ● 6101fa 4 LTC6101/LTC6101HV ELECTRICAL CHARACTERISTICS Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: The LTC6101C/LTC6101HVC are guaranteed to meet specified performance from 0°C to 70°C. The LTC6101C/LTC6101HVC are designed, characterized and expected to meet specified performance from – 40°C to 85°C but are not tested or QA sampled at these temperatures. LTC6101I/ LTC6101HVI are guaranteed to meet specified performance from – 40°C to 85°C. The LTC6101H/LTC6101HVH are guaranteed to meet specified performance from – 40°C to 125°C. U W TYPICAL PERFOR A CE CHARACTERISTICS Input VOS vs Temperature Input VOS vs Supply Voltage REPRESENTATIVE UNITS 600 TA = 0°C 0 INPUT OFFSET (µV) INPUT OFFSET (µV) 2.5 20 400 200 0 – 200 – 400 –40 TA = 45°C –60 –80 TA = 85°C A GRADE B GRADE C GRADE – 800 – 1000 –40 –20 0 RIN = 100 ROUT = 5k VIN = 5mV RIN = 100 ROUT = 5k VIN = 5mV –120 4 11 18 25 32 39 VSUPPLY (V) 46 0 60 VS = 4V 7 6 VS = 12V 8 6 VS = 6V VS = 5V 4 VS = 4V 0 20 40 60 80 TEMPERATURE (°C) 100 120 6101 G06 0 –40 –20 5 VS = 12V VS = 60V 4 3 VS = 6V 2 VS = 4V 2 2 RIN = 3k ROUT = 3k LTC6101: IOUT Maximum vs Temperature MAXIMUM IOUT (mA) MAXIMUM OUTPUT (V) VS = 6V LTC6101 LTC6101HV 6101 G05 10 4 TA = 125°C 4 10 20 30 40 50 60 70 80 90 100 VSUPPLY (V) VS = 100V 10 MAXIMUM OUTPUT (V) 53 12 VS = 60V 6 TA = 85°C 1 LTC6101HV: VOUT Maximum vs Temperature 12 0 –40 –20 TA = 70°C 6101 G02 LTC6101: VOUT Maximum vs Temperature VS = 12V TA = –40°C 0.5 6101 G01 8 TA = 0°C 1.5 TA = 125°C –140 20 40 60 80 100 120 TEMPERATURE (°C) TA = 25°C 2 TA = –40°C –20 –100 – 600 Input Sense Range 40 MAXIMUM VSENSE (V) 800 1 0 20 40 60 80 TEMPERATURE (°C) 100 120 6101 G20 0 –40 –20 0 20 40 60 80 TEMPERATURE (°C) 100 120 6101 G07 6101fa 5 LTC6101/LTC6101HV U W TYPICAL PERFOR A CE CHARACTERISTICS LTC6101HV: IOUT Maximum vs Temperature Output Error Due to Input Offset vs Input Voltage 100 7 4 VS = 6V VS = 5V 2 25 1 B GRADE 0.01 20 40 60 80 TEMPERATURE (°C) 100 120 –10 0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 INPUT VOLTAGE (V) 6101 G21 160 120 350 IB (nA) 60 40 20 0 –40 –20 600 85°C 70°C 125°C 500 300 250 25°C 200 0°C 150 –40°C 100 20 40 60 80 TEMPERATURE (°C) 100 120 0 4 8 12 16 20 24 28 32 36 40 44 48 52 56 60 SUPPLY VOLTAGE (V) –40°C 0°C 125°C 300 25°C 200 VIN = 0 RIN = 1M 0 10 20 30 40 50 60 70 80 90 100 SUPPLY VOLTAGE (V) 6101 G22 6101 G11 Step Response 0mV to 10mV Step Response 10mV to 20mV – VSENSE V+-10mV VSENSE– + V -20mV 0.5V 1V TA = 25°C V+ = 12V RIN = 100 ROUT = 5k VSENSE+ = V+ TA = 25°C V+ = 12V RIN = 100 ROUT = 5k VSENSE+ = V+ 0V 70°C 0 0 6101 G10 V+ V+-10mV 400 85°C 100 VIN = 0 RIN = 1M 50 0 SUPPLY CURRENT (µA) 400 SUPPLY CURRENT (µA) 140 80 LTC6101HV: Supply Current vs Supply Voltage 450 VS = 4V 1M 6101 G09 LTC6101: Supply Current vs Supply Voltage VS = 6V TO 100V 10k 100k FREQUENCY (Hz) 1k 6101 G08 Input Bias Current vs Temperature 100 IOUT = 200µA 10 –5 A GRADE 0 15 0 VS = 4V 0 –40 –20 20 5 C GRADE 0.1 IOUT = 1mA TA = 25°C RIN = 100 ROUT = 4.99k 30 GAIN (dB) VS = 100V 1 35 10 5 3 TA = 25°C GAIN =10 VS = 12V OUTPUT ERROR (%) MAXIMUM IOUT (mA) 6 Gain vs Frequency 40 0.5V VOUT TIME (10µs/DIV) VOUT TIME (10µs/DIV) 6101 G12 6101 G13 6101fa 6 LTC6101/LTC6101HV U W TYPICAL PERFOR A CE CHARACTERISTICS Step Response 100mV V+ V+-100mV 5V VSENSE– V+ V+-100mV CLOAD = 10pF CLOAD = 1000pF Step Response Rising Edge Step Response 100mV VSENSE– TA = 25°C V+ = 12V CLOAD = 2200pF RIN = 100 ROUT = 5k VSENSE+ = V+ 5V TA = 25°C V+ = 12V RIN = 100 ROUT = 5k VSENSE+ = V+ VSENSE– ∆VSENSE– =100mV 5.5V 5V TA = 25°C V+ = 12V RIN = 100 ROUT = 5k VSENSE+ = V+ VOUT IOUT = 100µA 0V VOUT 0.5V 0V VOUT TIME (100µs/DIV) TIME (10µs/DIV) IOUT = 0 TIME (500ns/DIV) 6101 G14 6101 G15 Step Response Falling Edge 6101 G16 PSRR vs Frequency 160 ∆VSENSE– =100mV 5.5V 5V 140 TA = 25°C V+ = 12V RIN = 100 ROUT = 5k VSENSE+ = V+ IOUT = 100µ 0.5V 0V LTC6101, V+ = 4V 120 VOUT IOUT = 0 TIME (500ns/DIV) 6101 G17 PSRR (dB) 0V 100 80 LTC6101, LTC6101HV, V+ = 12V 60 R = 100 IN ROUT = 10k 40 C OUT = 5pF GAIN = 100 LTC6101HV, 20 I V+ = 5V OUTDC = 100µA VINAC = 50mVp 0 0.1 1 10 100 1k 10k 100k FREQUENCY (Hz) 1M 6101 G19 6101fa 7 LTC6101/LTC6101HV U U U PI FU CTIO S IN+ (Pin 4): Must be tied to the system load end of the sense resistor, either directly or through a resistor. OUT (Pin 1): Current Output. OUT (Pin 1) will source a current that is proportional to the sense voltage into an external resistor. V+ (Pin 5): Positive Supply Pin. Supply current is drawn through this pin. The circuit may be configured so that the LTC6101 supply current is or is not monitored along with the system load current. To monitor only system load current, connect V+ to the more positive side of the sense resistor. To monitor the total current, including the LTC6101 current, connect V+ to the more negative side of the sense resistor. V – (Pin 2): Negative Supply (or Ground for Single-Supply Operation). IN – (Pin 3): The internal sense amplifier will drive IN– (Pin 3) to the same potential as IN+ (Pin 4). A resistor (RIN) tied from V+ to IN– sets the output current IOUT = VSENSE/RIN. VSENSE is the voltage developed across the external RSENSE (Figure 1). W BLOCK DIAGRA ILOAD – VSENSE + VBATTERY RSENSE RIN 5 V+ 10V L O A D 3 4 IN – 5k – IN + 5k + IOUT 10V OUT V– LTC6101/LTC6101HV 2 1 6101 BD VOUT = VSENSE x ROUT RIN ROUT Figure 1. LTC6101/LTC6101HV Block Diagram and Typical Connection U W U U APPLICATIO S I FOR ATIO The LTC6101 high side current sense amplifier (Figure 1) provides accurate monitoring of current through a userselected sense resistor. The sense voltage is amplified by a user-selected 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 input current, so it will flow through an internal MOSFET to the output pin. 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. 6101fa 8 LTC6101/LTC6101HV U W U U APPLICATIO S I FOR ATIO Useful Gain Configurations Gain RIN ROUT VSENSE at VOUT = 5V IOUT at VOUT = 5V 20 499 10k 250mV 500µA 50 200 10k 100mV 500µA 100 100 10k 50mV 500µA 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 reproduced signal, and is limited primarily by input DC offset of the internal amplifier of the LTC6101. In addition, RSENSE must be small enough that VSENSE does not exceed the maximum input voltage specified by the LTC6101, 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 amp is limited by the input offset. As an example, the LTC6101B 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 LTC6101 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 max, and over 70dB of dynamic range if the rated input maximum of 500mV 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 x 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 highcurrent paths, this error can be reduced by orders of magnitude. A sense resistor with integrated Kelvin sense terminals will give the best results. Figure 2 illustrates the recommended method. V+ RSENSE RIN 4 3 + – LOAD 2 5 1 VOUT LTC6101 ROUT 6101 F02 Figure 2. Kelvin Input Connection Preserves Accuracy Despite Large Load Current 6101fa 9 LTC6101/LTC6101HV U W U U APPLICATIO S I FOR ATIO Selection of External Input Resistor, RIN current measurement accuracy by limiting the result, while increasing the low current measurement resolution. 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. V+ RSENSE RIN should be chosen to allow the required resolution while limiting the output current. At low supply voltage, IOUT may be as much as 1mA. 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 max output current and power dissipation. If low sense currents must be resolved accurately in a system that has very wide dynamic range, a smaller RIN than the max current spec allows may be used if the max current is limited in another way, such as with a Schottky diode across RSENSE (Figure 3a). This will reduce the high LOAD Figure 3a. Shunt Diode Limits Maximum Input Voltage to Allow Better Low Input Resolution Without Overranging This approach can be helpful in cases where occasional large burst currents may be ignored. It can also be used in a multirange configuration where a low current circuit is added to a high current circuit (Figure 3b). Note that a comparator (LTC1540) is used to select the range, and transistor M1 limits the voltage across RSENSE LO. Care should be taken when designing the board layout for RIN, especially for small RIN values. All trace and interconnect impedances will increase the effective RIN value, causing a gain error. In addition, internal device resistance will add approximately 0.2Ω to RIN. VLOGIC (3.3V TO 5V) CMPZ4697 7 10k 3 M1 Si4465 VIN RSENSE HI 10m ILOAD VOUT 301 RSENSE LO 100m 4 + – 4 + – LTC6101 8 5 Q1 CMPT5551 40.2k 6 301 301 301 4.7k 1.74M 2 DSENSE 6101 F03a 3 4 5 2 VIN 1 3 + – 2 5 LTC1540 1 619k 1 LTC6101 HIGH RANGE INDICATOR (ILOAD > 1.2A) HIGH CURRENT RANGE OUT 250mV/A 7.5k VLOGIC BAT54C R5 7.5k (VLOGIC +5V) ≤ VIN ≤ 60V LOW CURRENT RANGE OUT 2.5V/A 0 ≤ ILOAD ≤ 10A 6101 F03b Figure 3b. Dual LTC6101s Allow High-Low Current Ranging 6101fa 10 LTC6101/LTC6101HV U W U U APPLICATIO S I FOR ATIO Selection of External Output Resistor, ROUT The output resistor, ROUT, determines how the output current is converted to voltage. VOUT is simply IOUT • ROUT. Output Error, EOUT, Due to the Amplifier DC Offset Voltage, VOS EOUT(VOS) = VOS • (ROUT/RIN) In choosing an output resistor, the max output voltage must first be considered. If the circuit that is driven by the output does not limit the output voltage, then ROUT must be chosen such that the max output voltage does not exceed the LTC6101 max output voltage rating. 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. 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 available dynamic range. The paragraph “Selection of External Current Sense Resistor” provides details. 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: The bias current IB(+) flows into the positive input of the internal op amp. IB(–) flows into the negative input. VOUT = IOUT • ROUT • RIN(DRIVEN) ROUT + RIN(DRIVEN) = IOUT • ROUT • 100 = 0.99 • IOUT • ROUT 101 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. Output Error, EOUT, Due to the Bias Currents, IB(+) and IB(–) EOUT(IBIAS) = ROUT((IB(+) • (RSENSE/RIN) – IB(–)) Since IB(+) ≈ IB(–) = IBIAS, if RSENSE << RIN then, EOUT(IBIAS) ≈ –ROUT • IBIAS For instance if IBIAS is 100nA and ROUT is 1kΩ, the output error is 0.1mV. Note that in applications where RSENSE ≈ RIN, IB(+) causes a voltage offset in RSENSE that cancels the error due to IB(–) and EOUT(IBIAS) ≈ 0. In applications where RSENSE < RIN, the bias current error can be similarly reduced if an external resistor RIN(+) = (RIN – RSENSE) is connected as shown in Figure 4 below. Under both conditions: EOUT(IBIAS) = ± ROUT • IOS; IOS = IB(+) – IB(–) V+ RIN– RSENSE RIN+ 4 3 + Ideally, the circuit output is: – LOAD VOUT R = VSENSE • OUT ; VSENSE = RSENSE • ISENSE RIN In this case, the only error is due to resistor mismatch, which provides an error in gain only. However, offset voltage, bias current and finite gain in the amplifier cause additional errors: 2 5 1 VOUT LTC6101 ROUT RIN+ = RIN– – RSENSE 6101 F04 Figure 4. Second Input R Minimizes Error Due to Input Bias Current 6101fa 11 LTC6101/LTC6101HV U W U U APPLICATIO S I FOR ATIO If the offset current, IOS, of the LTC6101 amplifier is 2nA, the 100 microvolt error above is reduced to 2 microvolts. Adding RIN+ as described will maximize the dynamic range of the circuit. For less sensitive designs, RIN+ is not necessary. Example: If an ISENSE range = (1A to 1mA) and (VOUT/ISENSE) = 3V/1A Then, from the Electrical Characteristics of the LTC6101, RSENSE ≈ VSENSE (max) / ISENSE (max) = 500mV/1A = 500mΩ Gain = ROUT/RIN = VOUT(max) / VSENSE (max) = 3V/500mV =6 If the maximum output current, IOUT, is limited to 1mA, ROUT equals 3V/1mA ≈ 3.01 kΩ (1% value) and RIN = 3kΩ/ 6 ≈ 499Ω (1% value). The output error due to DC offset is ±900µVolts (typ) and the error due to offset current, IOS is 3k x 2nA = ±6µVolts (typical), provided RIN+ = RIN–. The maximum output error can therefore reach ±906µVolts or 0.03% (–70dB) of the output full scale. Considering the system input 60dB dynamic range (ISENSE = 1mA to 1A), the 70dB performance of the LTC6101 makes this application feasible. Output Error, EOUT, Due to the Finite DC Open Loop Gain, AOL, of the LTC6101 Amplifier This errors is inconsequential as the AOL of the LTC6101 is very large. Output Current Limitations Due to Power Dissipation The LTC6101 can deliver up to 1mA continuous current to the output pin. This current flows through RIN and enters the current sense amp via the IN(–) pin. The power dissipated in the LTC6101 due to the output signal is: POUT = (V–IN – VOUT) • IOUT Since V–IN ≈ V+, POUT ≈ (V+ – VOUT) • IOUT There is also power dissipated due to the quiescent supply current: PQ = IDD • V+ The total power dissipated is the output dissipation plus the quiescent dissipation: PTOTAL = POUT + PQ At maximum supply and maximum output current, the total power dissipation can exceed 100mW. This will cause significant heating of the LTC6101 die. In order to prevent damage to the LTC6101, the maximum expected dissipation in each application should be calculated. This number can be multiplied by the θJA value listed in the package section on page 2 to find the maximum expected die temperature. This must not be allowed to exceed 150°C, or performance may be degraded. As an example, if an LTC6101 in the S5 package is to be run at 55V ±5V supply with 1mA output current at 80°C: PQ(MAX) = IDD(MAX) • V+(MAX) = 41.4mW POUT(MAX) = IOUT • V+(MAX) = 60mW TRISE = θJA • PTOTAL(MAX) TMAX = TAMBIENT + TRISE TMAX must be < 150°C PTOTAL(MAX) ≈ 96mW and the max die temp will be 104°C If this same circuit must run at 125°C, the max die temp will increase to 150°C. (Note that supply current, and therefore PQ, is proportional to temperature. Refer to Typical Performance Characteristics section.) In this condition, the maximum output current should be reduced to avoid device damage. Note that the MSOP package has a larger θJA than the S5, so additional care must be taken when operating the LTC6101A/LTC6101HVA at high temperatures and high output currents. The LTC6101HV can be used at voltages up to 105V. This additional voltage requires that more power be dissipated for a given level of current. This will further limit the allowed output current at high ambient temperatures. It is important to note that the LTC6101 has been designed to provide at least 1mA to the output when required, and can deliver more depending on the conditions. Care must 6101fa 12 LTC6101/LTC6101HV U W U U APPLICATIO S I FOR ATIO be taken to limit the maximum output current by proper choice of sense resistor and, if input fault conditions exist, external clamps. 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 ADC. This output capacitor in parallel with an output resistor will create a pole in the output response at: f –3dB = allow a wide VSENSE range, it also allows the input reference to be separate from the positive supply (Figure 5). Note that the difference between VBATT and V+ must be no more than the common mode range listed in the Electrical Characteristics table. If the maximum VSENSE is less than 500mV, the LTC6101 may monitor its own supply current, as well as that of the load (Figure 6). VBATTERY RIN RSENSE 4 3 + – V+ LOAD 2 5 1 2 • π • ROUT • COUT 1 VOUT LTC6101 ROUT Useful Equations 6101 F05 Figure 5. V+ Powered Separately from Load Supply (VBATT) Input Voltage: VSENSE = ISENSE • RSENSE Voltage Gain: Current Gain: VOUT R = OUT VSENSE RIN IOUT ISENSE Transconductance: Transimpedance: = V+ RSENSE RIN RSENSE 4 ISENSE = RSENSE • 3 + 1 IOUT = VSENSE RIN VOUT RIN LOAD 2 – 5 ROUT RIN 1 VOUT LTC6101 ROUT Input Common Mode Range 6101 F06 The inputs of the LTC6101 can function from 1.5V below the positive supply to 0.5V above it. Not only does this Figure 6. LTC6101 Supply Current Monitored with Load 6101fa 13 LTC6101/LTC6101HV U W U U APPLICATIO S I FOR ATIO Reverse Supply Protection Some applications may be tested with reverse-polarity supplies due to an expectation of this type of fault during operation. The LTC6101 is not protected internally from external reversal of supply polarity. To prevent damage that may occur during this condition, a Schottky diode should be added in series with V– (Figure 7). This will limit the reverse current through the LTC6101. Note that this diode will limit the low voltage performance of the LTC6101 by effectively reducing the supply voltage to the part by VD. In addition, if the output of the LTC6101 is wired to a device that will effectively short it to high voltage (such as through an ESD protection clamp) during a reverse supply condition, the LTC6101’s output should be connected through a resistor or Schottky diode (Figure 8). Response Time The LTC6101 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. RSENSE 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 datasheet. 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 gate of the internal output FET (Figure 1) in order to maintain the internal loop. This results in current flowing through RIN and the internal FET. This current slew rate will be determined by the amplifier and FET characteristics as well as the input resistor, RIN. 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. Using a larger ROUT will decrease the response time, since VOUT = IOUT • ROUT. Reducing RIN and increasing ROUT will both have the effect of increasing the voltage gain of the circuit. RSENSE R1 100 4 L O A D R1 100 3 + – 2 5 4 VBATT LTC6101 D1 1 L O A D 3 + – 2 LTC6101 R2 4.99k D1 6101 F07 VBATT 5 1 R3 1k ADC R2 4.99k 6101 F08 Figure 7. Schottky Prevents Damage During Supply Reversal Figure 8. Additional Resistor R3 Protects Output During Supply Reversal 6101fa 14 LTC6101/LTC6101HV U TYPICAL APPLICATIO S Bidirectional Current Sense Circuit with Separate Charge/Discharge Output IDISCHARGE ICHARGE RSENSE CHARGER RIN C 100 RIN D 100 RIN D 100 4 + – 2 L O A D RIN C 100 3 3 5 5 1 LTC6101 1 + ROUT D 4.99k 4 – + LTC6101 + VOUT D VOUT C – – VBATT 2 ROUT C 4.99k 6101 TA02 DISCHARGING: VOUT D = IDISCHARGE • RSENSE CHARGING: VOUT C = ICHARGE • RSENSE ( ( ) ROUT D WHEN IDISCHARGE ≥ 0 RIN D ) ROUT C WHEN ICHARGE ≥ 0 RIN C LTC6101 Monitors Its Own Supply Current ILOAD VS RSENSE 4 2 CMPZ4697* (10V) ISUPPLY R1 100 L O A D High-Side-Input Transimpedance Amplifier 4.75k 3 + – LASER MONITOR PHOTODIODE 4.75k 4 5 VBATT 2 iPD 10k 3 + – 5 1 LTC6101 + R2 4.99k VOUT – LTC6101 1 RL 6101 TA03 ( ) VOUT = 49.9 • RSENSE ILOAD + ISUPPLY VO VO = IPD • RL *VZ SETS PHOTODIODE BIAS VZ + 4 ≤ VS ≤ VZ + 60 6101 TA04 6101fa 15 LTC6101/LTC6101HV U TYPICAL APPLICATIO S 16-Bit Resolution Unidirectional Output into LTC2433 ADC ILOAD VSENSE – + RIN 100Ω 4 L O A D 4V TO 60V 3 + – 2 5 1µF 5V 2 VOUT 1 LTC6101 4 IN+ 1 REF+ VCC SCK LTC2433-1 ROUT 4.99k 5 IN SDD – CC FO REF– GND 3 ROUT VOUT = • VSENSE = 49.9VSENSE RIN 6 9 8 TO µP 7 10 ADC FULL-SCALE = 2.5V 6101 TA06 Intelligent High-Side Switch with Current Monitor 10µF 63V VLOGIC 14V 47k FAULT OFF ON 3 4 100Ω 1% 8 5 3 RS LT1910 LTC6101 6 2 1 100Ω 1µF 1 VO 4 4.99k 2 5 SUB85N06-5 L O A D VO = 49.9 • RS • IL IL FOR RS = 5mΩ, VO = 2.5V AT IL = 10A (FULL SCALE) 6101 TA07 6101fa 16 LTC6101/LTC6101HV U TYPICAL APPLICATIO S 48V Supply Current Monitor with Isolated Output with 105V Survivability ISENSE VSENSE + VS RIN – LOAD RSENSE 3 4 – + 5 2 V– LTC6101HV VLOGIC ROUT VOUT ANY OPTOISOLATOR V– N = OPTOISOLATOR CURRENT GAIN R VOUT = VLOGIC – ISENSE • SENSE • N • ROUT RIN 6101 TA08 Simple 500V Current Monitor DANGER! Lethal Potentials Present — Use Caution ISENSE VSENSE – 500V + RSENSE 4 L O A D 2 RIN 100Ω 3 + – DANGER!! HIGH VOLTAGE!! 5 1 LTC6101 62V CMZ59448 M1 VOUT M1 AND M2 ARE FQD3P50 TM ROUT VOUT = • VSENSE = 49.9 VSENSE RIN M2 ROUT 4.99k 2M 6101 TA09 6101fa 17 LTC6101/LTC6101HV U PACKAGE DESCRIPTIO 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 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.65 (.0256) BSC 8 7 6 5 0.52 (.0205) REF RECOMMENDED SOLDER PAD LAYOUT 0.254 (.010) 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 4.90 ± 0.152 (.193 ± .006) DETAIL “A” 0° – 6° TYP GAUGE PLANE 0.53 ± 0.152 (.021 ± .006) DETAIL “A” 1 2 3 4 1.10 (.043) MAX 0.86 (.034) REF 0.18 (.007) SEATING PLANE 0.22 – 0.38 (.009 – .015) TYP 0.65 (.0256) BSC 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 6101fa 18 LTC6101/LTC6101HV U PACKAGE DESCRIPTIO S5 Package 5-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1635) 0.62 MAX 0.95 REF 2.90 BSC (NOTE 4) 1.22 REF 1.4 MIN 3.85 MAX 2.62 REF 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 TYP 5 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3. DIMENSIONS ARE INCLUSIVE OF PLATING 4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR 5. MOLD FLASH SHALL NOT EXCEED 0.254mm 6. JEDEC PACKAGE REFERENCE IS MO-193 1.90 BSC S5 TSOT-23 0302 6101fa 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 LTC6101/LTC6101HV U TYPICAL APPLICATIO Bidirectional Current Sense Circuit with Combined Charge/Discharge Output IDISCHARGE ICHARGE RSENSE CHARGER RIN C RIN D RIN C RIN D 4 L O A D + – 2 3 3 5 5 1 LTC6101 1 + VOUT 4 – + VBATT 2 LTC6101 ROUT – 6101 TA05 DISCHARGING: VOUT = IDISCHARGE • RSENSE CHARGING: VOUT = ICHARGE • RSENSE ( ( ) ROUT WHEN IDISCHARGE ≥ 0 RIN D ) ROUT WHEN ICHARGE ≥ 0 RIN C RELATED PARTS PART NUMBER DESCRIPTION COMMENTS LT1636 Rail-to-Rail Input/Output, Micropower Op Amp VCM Extends 44V above VEE, 55µA Supply Current, Shutdown Function LT1637/LT1638/ LT1639 Single/Dual/Quad, Rail-to-Rail, Micropower Op Amp VCM Extends 44V above VEE, 0.4V/µs Slew Rate, >1MHz Bandwidth, <250µA Supply Current per Amplifier LT1787/LT1787HV Precision, Bidirectional, High Side Current Sense Amplifier 2.7V to 60V Operation, 75µV Offset, 60µA Current Draw LTC1921 Dual –48V Supply and Fuse Monitor ±200V Transient Protection, Drives Three Optoisolators for Status LT1990 High Voltage, Gain Selectable Difference Amplifier ±250V Common Mode, Micropower, Pin Selectable Gain = 1, 10 LT1991 Precision, Gain Selectable Difference Amplifier 2.7V to ±18V, Micropower, Pin Selectable Gain = –13 to 14 LTC2050/LTC2051/ LTC2052 Single/Dual/Quad Zero-Drift Op Amp 3µV Offset, 30nV/°C Drift, Input Extends Down to V– LTC4150 Coulomb Counter/Battery Gas Gauge Indicates Charge Quantity and Polarity Over-The-Top is a trademark of Linear Technology Corporation. 6101fa 20 Linear Technology Corporation LT/TP 0805 500 REV A • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com © LINEAR TECHNOLOGY CORPORATION 2005