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LTC6103 Dual High Voltage, High Side Current Sense Amplifier FEATURES

DESCRIPTION
The LTC(R)6103 is a versatile, high voltage, high side, dual current sense amplifier. The two internal amplifiers are independent except that they share the same V- terminal. Design flexibility is provided by the excellent device characteristics: 450V maximum offset, and only 275A of current consumption (typical at 12V) for each amplifier. The LTC6103 operates on supplies from 4V to 60V. The LTC6103 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 minimal. The wide operating supply range and high accuracy make the LTC6103 ideal for an extensive variety of applications from automotive to industrial and power management. The fast response makes the LTC6103 the perfect choice for load current warnings and shutoff protection control. With very low supply current, the LTC6103 is suitable for power sensitive applications. The LTC6103 is available in an 8-lead MSOP package.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners.
Two Independent Current Sense Amplifiers Wide Supply Range: 4V to 60V, 70V Absolute Maximum Low Offset Voltage: 450V Maximum Fast Response: 1s Response Time Gain Configurable with External Resistors Low Input Bias Current: 170nA Maximum PSRR: 110dB Minimum (6V to 60V) Output Current: 1mA Maximum Low Supply Current: 275A per Amplifier, VS = 12V Specified for -40C to 125C Temperature Range Available in an 8-lead MSOP Package
APPLICATIONS

Current Shunt Measurement Battery Monitoring Remote Sensing Power Management High Voltage Level Translator
TYPICAL APPLICATION
Two 16-Bit Current Sense Channels Connected Directly to the LTC2436-1 ADC
ILOAD LOAD 8 +INA 7 -INA
-
VA+ VSENSE
+
VB+ VSENSE
Step Response
ILOAD LOAD 5
+
-
VSENSE- VSENSE- = 100mV 5.5V 5V
RIN 100 6
RIN 100 -INB
+INB
5V 1F
+-
VSA
-+
VSB 7 OUTB 2 4 5 CH0 3,8,9,10,14,15,16
6103 TA01a
2 6 CH1 LTC2436-1
1 13 12 11 TO P
IOUT = 100A TA = 25C V+ = 12V RIN = 100 ROUT = 5k VSENSE+ = V+
6103 TA01b
LTC6103
OUTA 1 4
V
-
0.5V 0V
VOUT
IOUT = 0A 500ns/DIV
ROUT 4.99k
ROUT 4.99k
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LTC6103 ABSOLUTE MAXIMUM RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW OUTA OUTB NC V- 1 2 3 4 8 7 6 5 +INA -INA -INB +INB
Total Supply Voltage (+INA/+INB to V-) ....................70V Maximum Applied Output Voltage (OUTA/OUTB) ........9V Input Current........................................................10mA Output Short-Circuit Duration (to V-)............... Indefinite Operating Temperature Range LTC6103C ............................................ -40C to 85C LTC6103I ............................................. -40C to 85C LTC6103H .......................................... -40C to 125C Specified Temperature Range (Note 2) LTC6103C ................................................ 0C to 70C LTC6103I ............................................. -40C to 85C LTC6103H .......................................... -40C to 125C Storage Temperature Range................... -65C to 150C Lead Temperature (Soldering, 10 sec) .................. 300C
MS8 PACKAGE 8-LEAD PLASTIC MSOP TJMAX = 150C, JA = 300C/W
ORDER PART NUMBER LTC6103CMS8 LTC6103IMS8 LTC6103HMS8
MS8 PART MARKING* LTCMN LTCMN LTCMN
Order Options Tape and Reel: Add #TR Lead Free: Add #PBF Lead Free Tape and Reel: Add #TRPBF Lead Free Part Marking: http://www.linear.com/leadfree/ Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
ELECTRICAL CHARACTERISTICS
SYMBOL +INA(VSA)/ +INB(VSB) VOS VOS/T IB PSRR PARAMETER Supply Voltage Range Input Offset Voltage CONDITIONS
The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. RIN = 100, ROUT = 5k, 4V +INA/+INB 60V, V- = 0V unless otherwise noted.
MIN
TYP
MAX 60
UNITS V V V V V/C nA nA dB dB dB dB V V V
4 85
VSENSE = 5mV, LTC6103 VSENSE = 5mV, LTC6103C, LTC6103I VSENSE = 5mV, LTC6103H VSENSE = 5mV RIN = 1M to -INA and -INB +INA/+INB = 6V to 60V, VSENSE = 5mV +INA/+INB = 4V to 60V, VSENSE = 5mV

450 600 700 170 245
Input Offset Voltage Drift Input Bias Current Power Supply Rejection Ratio
1.5 100 110 106 105 98 8 3 1 0 22.5 30 35 120 115
VOUT(MAX)
Maximum Output Voltage
12V +INA/+INB 60V, VSENSE = 88mV, ROUT = 10k +INA/+INB = 6V, VSENSE = 66mV, ROUT = 5k +INA/+INB = 4V, VSENSE = 55mV, ROUT = 2k VSENSE = 0V, LTC6103 VSENSE = 0V, LTC6103C, LTC6103I VSENSE = 0V, LTC6103H 6V +INA/+INB 60V, VSENSE = 110mV, ROUT = 2k +INA/+INB = 4V, VSENSE = 55mV, ROUT = 2k, Gain = 20 VSENSE = 100mV Step, 6V +INA/+INB 60V +INA/+INB = 4V (1V Output Step), ROUT = 1k IOUT = 200A, RIN = 100, ROUT = 5k IOUT = 1mA, RIN = 100, ROUT = 5k
VOUT(O)
Minimum Output Voltage (Note 3) Maximum Output Current Input Step Response (to 50% of Output Step) Signal Bandwidth
mV mV mV mA mA
IOUT(MAX) tr BW
1 0.5 1 1.5 120 140
s s kHz kHz
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LTC6103 ELECTRICAL CHARACTERISTICS
SYMBOL I+INA, I+INB PARAMETER Supply Current per Amplifier CONDITIONS +INA/+INB = 4V, IOUT = 0, RIN = 1M +INA/+INB = 6V, IOUT = 0, RIN = 1M +INA/+INB = 12V, IOUT = 0, RIN = 1M +INA/+INB = 60V, IOUT = 0, RIN = 1M LTC6103I, LTC6103C LTC6103H Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: The LTC6103C is guaranteed to meet specified performance from 0C to 70C. The LTC6103C is designed, characterized and

The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25C. RIN = 100, ROUT = 5k, 4V +INA/+INB 60V, V- = 0V unless otherwise noted.
MIN TYP 220 255 275 390 MAX 450 475 475 525 500 590 640 690 720 UNITS A A A A A A A A A
expected to meet specified performance from -40C to 85C but is not tested or QA sampled at these temperatures. LTC6103I is guaranteed to meet specified performance from -40C to 85C. The LTC6103H is guaranteed to meet specified performance from -40C to 125C. Note 3: This parameter is not tested in production and is guaranteed by the VOS test.
TYPICAL PERFORMANCE CHARACTERISTICS
Input VOS vs Temperature
200 150 INPUT OFFSET VOLTAGE (V) INPUT OFFSET VOLTAGE (V) 100 50 0 -50 -100 -150 -200 -40 -20 0 RIN = 100 ROUT = 5k VIN = 5mV 20 40 60 80 TEMPERATURE (C) 100 120
6103 G01
Input VOS vs Supply Voltage
200 150 100 50 0 -50 -100 -150 -200 0 10 20 RIN = 100 ROUT = 5k VIN = 5mV 40 50 30 VSUPPLY AT +INA OR +INB (V) 60
6103 G02
Input Sense Range
5.0 RIN = 5k 4.5 ROUT = 2.5k MAXIMUM VSENSE (V) 4.0 3.5 3.0 2.5 2.0 1.5 1.0 4 5 6 7 8 V+ (V)
6103 G03
3 REPRESENTATIVE UNITS
TA = 85C
TA = 125C
TA = 45C TA = 0C TA = -40C
9
10
11
12
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LTC6103 TYPICAL PERFORMANCE CHARACTERISTICS
VOUT Maximum vs Temperature
12 VS = 60V 10 MAXIMUM OUTPUT (V) VS = 12V MAXIMUM IOUT (mA) 8 6 VS = 6V 4 VS = 4V 2 0 -40 -20 7 6 5 4 VS = 6V 3 2 1 0 -40 -20 0.01 0 20 40 60 80 TEMPERATURE (C) 100 120
6103 G05
IOUT Maximum vs Temperature
100 VS = 12V 10 OUTPUT ERROR (%) VS = 60V
Calculated Output Error Due to Input Offset vs Input Voltage
TA = 25C GAIN =10
1
VS = 4V
0.1
0
20 40 60 80 TEMPERATURE (C)
100 120
6103 G04
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4 0.45 0.5 INPUT VOLTAGE (V)
6103 G06
Gain vs Frequency
40 35 30 GAIN (dB) 25 IOUT = 200A 20 15 10 TA = 25C 5 RIN = 100 ROUT = 5k 0 1k 100k 10k INPUT FREQUENCY (Hz) IOUT = 1mA IB (nA) 160 140
Input Bias Current vs Temperature
450 400 VS = 6V TO 100V VS = 4V SUPPLY CURRENT (A) 350 300 250 200 150 100 50 0 20 40 60 80 TEMPERATURE (C) 100 120
6103 G09
Supply Current vs Supply Voltage
TA = 125C TA = 85C TA = 70C
120 100 80 60 40 20 0 -40 -20
TA = 25C
TA = -40C TA = 0C
VIN = 0V RIN = 1M 0 20 30 10 40 50 VSUPPLY AT +INA OR +INB (V) 60
1M
6103 G08
0
6103 G10
Step Response 0mV to 10mV
V+ + V -10mV 0.5V VSENSE- V+-10mV V -20mV TA = 25C V+ = 12V RIN = 100 ROUT = 5k VSENSE+ = V+ 1V
+
Step Response 10mV to 20mV
VSENSE-
TA = 25C V+ = 12V RIN = 100 ROUT = 5k VSENSE+ = V+
0V
VOUT TIME (10s/DIV)
0.5V
VOUT TIME (10s/DIV)
6103 G11
6103 G12
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LTC6103 TYPICAL PERFORMANCE CHARACTERISTICS
Step Response 0mV to 100mV
VSENSE
-
Step Response 0mV to 100mV
V+ VSENSE
-
Step Response Rising Edge
VSENSE- VSENSE- =100mV 5.5V 5V TA = 25C V+ = 12V RIN = 100 ROUT = 5k VSENSE+ = V+ IOUT = 100A
VSENSE- =100mV 5V CLOAD = 10pF
VSENSE- =100mV
5V
CLOAD = 1000pF TA = 25C V+ = 12V RIN = 100 ROUT = 5k VSENSE+ = V+ 0V VOUT TIME (10s/DIV)
6103 G13
TA = 25C V+ = 12V CLOAD = 2200pF RIN = 100 ROUT = 5k VSENSE+ = V+
VOUT
0V
VOUT TIME (100s/DIV)
6103 G14
0.5V 0V
IOUT = 0A TIME (500ns/DIV)
6103 G15
Step Response Falling Edge
140 V+ VOUT TA = 25C V+ = 12V RIN = 100 ROUT = 5k VSENSE+ = V+ PSRR (dB) VSENSE- =100mV 120 100
PSRR vs Frequency
5.5V 5V
VS = 12V 80 VS = 4V 60 RIN = 100 40 ROUT = 5k COUT = 5pF 20 GAIN = 50 IOUTDC = 100A VINAC = 50mVP-P 0 0.1 1 10 100 1k 10k FREQUENCY (Hz)
IOUT = 0A 0.5V 0V
IOUT = 100A
TIME (500ns/DIV)
6103 G16
100k
1M
6103 G17
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LTC6103 PIN FUNCTIONS
OUTA (Pin 1): Current Output of Amplifier A. OUTA will source a current that is proportional to the sense voltage of amplifier A into an external resistor. OUTB (Pin 2): Current Output of Amplifier B. OUTB will source a current that is proportional to the sense voltage of amplifier B into an external resistor. NC (Pin 3): No Connect. V- (Pin 4): Negative Supply (or Ground for Single Supply Operation). Common to both amplifiers. +INB/VSB (Pin 5): The Positive Input of the Internal Sense Amplifier B. Must be tied to the system load end of the sense resistor. It also works as the positive supply for amplifier B. Supply current of amplifier B is drawn through this pin. The LTC6103 supply current is monitored along with the system load current. -INB (Pin 6): The Negative Input of the Internal Sense Amplifier B. The internal sense amplifier will drive -INB to the same potential as +INB. A resistor (RIN) tied from VB+ to -INB sets the output current IOUT = VSENSE/ RIN. VSENSE is the voltage developed across the external RSENSE (Figure 1). -INA (Pin 7): The Negative Input of the Internal Sense Amplifier A. The internal sense amplifier will drive -INA to the same potential as +INA. A resistor (RIN) tied from VA+ to -INA sets the output current IOUT = VSENSE/ RIN. VSENSE is the voltage developed across the external RSENSE (Figure 1). +INA/VSA (Pin 8): The Positive Input of the Internal Sense Amplifier A. Must be tied to the system load end of the sense resistor. It also works as the positive supply for amplifier A. Supply current of amplifier A is drawn through this pin. The LTC6103 supply current is monitored along with the system load current.
BLOCK DIAGRAM
VA+ ILOAD LOAD VSENSE VB+ VSENSE
-
+
RIN
+
-
ILOAD LOAD
RSENSE
RSENSE RIN 6 -INA -INB 5k 5k 5
8 +INA 5k 5k
7
+INB
ISA
+-
VSA 10V 10V OUTA 1 IOUT ROUT 4 V- 2 OUTB
-+
VSB
ISB
6103 F01
IOUT VOUT = VSENSE * ROUT
ROUT RIN
Figure 1. LTC6103 Block Diagram and Typical Connection
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LTC6103 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, (ILOAD + IS) * RSENSE/RIN, will flow through RIN. The high impedance inputs of the sense amplifier will not conduct this input current, so the current will flow through an internal MOSFET to the OUT pin. In most application cases, IS << ILOAD, so IOUT ILOAD * RSENSE/RIN. The output current can be transformed into a voltage by adding a resistor from OUT to V-. The output voltage is then VOUT = (V-) + (IOUT * ROUT).
APPLICATIONS INFORMATION
In this dual current sense device, amplifiers A and B are independent except for sharing the same V- pin. So supply voltage and component values can be chosen independently for each amplifier. 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 LTC6103. 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 larger than 50m. V 100mV RSENSE = SENSE = = 50m IPEAK 2A 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 LTC6103 has a typical input offset of 85V. If the minimum current is 20mA, a sense resistor of 4.25m will set VSENSE to 85V. 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 50m 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 1.7mA of load current. Peak dissipation is 200mW. If instead a 5m sense resistor is employed, then the effective current error is 17mA, while the peak sense voltage is reduced to 10mV at 2A, dissipating only 20mW. The low offset and corresponding large dynamic range of the LTC6103 make it more flexible than other solutions in this respect. The 85V typical offset gives 60dB of dynamic range for a sense voltage that is limited to 85mV max, and over 75dB of dynamic range for a maximum input of 500mV.
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LTC6103 APPLICATIONS INFORMATION
Sense Resistor Connection Kelvin connections should be used between the inputs (+IN and -IN) and the sense resistor 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 0.5m. 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 magnitude. A sense resistor with integrated Kelvin sense terminals will give the best results. Figure 2 illustrates the recommended method. Selection of External Input Resistor, RIN The external input resistor, RIN, controls the transconductance of the current sense circuit. Since: IOUT = VSENSE 1 , transconductance gm = RIN RIN
ILOAD LOAD V+ RSENSE
For example, if RIN = 100, then: IOUT = VSENSE 100
or IOUT = 1mA for VSENSE = 100mV. RIN should be chosen to allow the required resolution while limiting the output current. 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 maximum 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 maximum current specification allows may be used if the maximum current is limited in another way, such as with a Schottky diode across RSENSE (Figure 3a). This will reduce the high current measurement accuracy by limiting the result, while increasing the low current measurement resolution. This approach can be helpful in cases where occasional large burst currents may be ignored. It can also be used in a multi-range 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).
V+
RIN
+IN
-IN
+-
VS 1/2 OUT LTC6103 ROUT LOAD
6103 F02
V- RSENSE
6103 F03a
DSENSE
Figure 2. Kelvin Input Connection Preserves Accuracy Despite Large Load Current
Figure 3a. Shunt Diode Limits Maximum Input Voltage to Allow Better Low Input Resolution Without Overranging
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LTC6103 APPLICATIONS INFORMATION
CMPZ4697 10k M1 Si4465 ILOAD VOUT RSENSE(LO) 100m RSENSE(HI) 10m VIN 40.2k 301 8 7 301 6 LTC6103 1 2 4 7.5k BAT54C VLOGIC LOW CURRENT RANGE OUT 250mV/A 5 1.74M 2 619k HIGH CURRENT RANGE OUT 250mV/A 1 HIGH RANGE INDICATOR (ILOAD > 1.2A) 3 4 5 6 VLOGIC (3.3V TO 5V) 7
+ -
LTC1540 8 Q1 CMPT5551 4.7k
R5 7.5k
6103 F03b
(VLOGIC + 5V) VIN 60V 0A ILOAD 10A
Figure 3b. The LTC6103 Allows High-Low Current Ranging
Care should be taken when designing the printed circuit board layout to minimize input trace resistance (to Pins 5, 6, 7 and 8), especially for small RIN values. Trace resistance to the -IN terminals will increase the effective RIN value, causing a gain error. Trace resistance on +IN terminals will have an effect on offset error. These errors are described in more detail later in this data sheet. In addition, internal device resistance will add approximately 0.3 to RIN. Selection of External Output Resistor, ROUT The output resistor, ROUT, determines how the output current is converted to voltage. VOUT is simply IOUT * ROUT. In choosing an output resistor, the maximum output voltage must first be considered. If the circuit following 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, 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 *
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LTC6103 APPLICATIONS INFORMATION
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 bias current and input offset, as well as resistor matching. Ideally, the circuit output is: VOUT = VSENSE * ROUT RIN supply current can cause an output error if trace resistance between RSENSE and +IN is significant (Figure 4). EOUT(RT_+IN) = (IS * RT/RIN) * ROUT Trace resistance to the -IN pin will increase the effective RIN value, causing a gain error. In addition, internal device resistance will add approximately 0.3 to RIN. Minimizing the trace resistance is important and care should be taken in the PCB layout. Make the trace short and wide. Kelvin connection to the shunt resistor pad should be used.
V+ ILOAD LOAD RT RSENSE
VSENSE = RSENSE * ISENSE 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. Output Error, EOUT, Due to the Amplifier DC Offset Voltage, VOS EOUT( VOS) = VOS * ROUT RIN
RIN RT
+IN IS
-IN
+-
VS
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. Output Error, EOUT, Due to Bias Currents The bias current IB(+) flows into the positive input of the internal op amp. IB(-) flows into the negative input. 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 1k, then the output error is 0.1mV. Output Error, EOUT, Due to PCB Trace Resistance The LTC6103 uses the +IN pin for both the positive amplifier input and the positive supply input for the amplifier. The
1/2 LTC6103
OUT
V-
ROUT
6103 F04
Figure 4. Error Due to PCB Trace Resistance
Output Error, EOUT, Due to the Finite DC Open-Loop Gain, AOL, of the LTC6103 Amplifier This error is inconsequential as the AOL of the LTC6103 is very large. Design Example: If ISENSE range = (1A to 1mA) and: VOUT ISENSE = 3V 1A
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LTC6103 APPLICATIONS INFORMATION
If the power dissipation of the sense resistor is chosen to be less than 0.5W then: RSENSE 500mW ISENSE(MAX )2 = 500m The total power dissipated is the output dissipation plus the quiescent dissipation: PTOTAL = POUTA + POUTB + PQA + PQB At maximum supply and maximum output current, the total power dissipation can exceed 100mW. This will cause significant heating of the LTC6103 die. In order to prevent damage to the LTC6103, the maximum expected dissipation in each application should be calculated. This number can be multiplied by the JA value listed in the Package/Order Information to find the maximum expected die temperature. This must not be allowed to exceed 150C or performance may be degraded. As an example, if an LTC6103 in the MS8 package is to be run at 55V 5V supply with 0.5mA output current in both amplifiers at 80C: PQ(MAX) = IS(MAX) * V+ (MAX) * 2 = 82.8mW POUT(MAX) = IOUT * V+ (MAX) * 2 = 60mW TRISE = JA * PTOTAL(MAX) = 300C/W * (82.8mW + 60mW) 43C TMAX = TAMBIENT + TRISE = 80C + 43C = 123C TMAX must be <150C PTOTAL(MAX) 143mW and the maximum die temperature will be 123C If this same circuit must run at 125C, the maximum die temperature will exceed 150C. (Note that supply current, and therefore PQ, is proportional to temperature. Refer to the Typical Performance Characteristics.) In this condition, the maximum output current should be reduced to avoid device damage. It is important to note that the LTC6103 has been designed to provide at least 1mA to the output when required, and can deliver more depending on the conditions. Care must be taken to limit the maximum output current by proper choice of resistors 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
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VSENSE(MAX) = ISENSE(MAX) * RSENSE = 500mV Gain = VOUT(MAX ) ROUT 3V = = =6 RIN VSENSE(MAX ) 500mV
If the maximum output current, IOUT, is limited to 1mA: ROUT = RIN = 3V 3.01k (1% value) and 1mA
3k 499 (1% value) 6
The output error due to DC offset is 510V (typ) and the error due to offset current: IOS is 3k x 100nA = 300V (typical) The maximum output error can therefore reach 810V or 0.027% (-71dB) of the output full scale. Considering the system input 60dB dynamic range (ISENSE = 1mA to 1A), the 71dB performance of the LTC6103 makes this application feasible. In many applications the power dissipation of the sense resistor is of greater importance than the precision of the measurement. Designing for a VSENSE(MAX) of as low as 100mV is recommended in such cases. Output Current Limitations Due to Power Dissipation The LTC6103 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 LTC6103 due to the output signal is: POUT = (VIN- - VOUT) * IOUT Since VIN- VS, POUT (VS - VOUT) * IOUT There is also power dissipated due to the quiescent supply current: PQ = IS * VS
11
LTC6103 APPLICATIONS INFORMATION
will give a lowpass 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 = 1 2 * * ROUT * COUT 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 5). This will limit the reverse current through the LTC6103. Note that this diode will limit the low voltage performance of the LTC6103 by effectively reducing the supply voltage to the part by VD. In addition, if the output of the LTC6103 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 LTC6103's output should be connected through a resistor or Schottky diode (Figure 6). Response Time The LTC6103 is designed to exhibit fast response to inputs for the purpose of circuit protection or signal transmission. This response time will be affected by the external circuit in two ways, delay and speed. If the output current is very low and an input transient occurs, there may be an increased delay before the output voltage begins changing. This can be improved by increasing the minimum output current, either by increasing RSENSE or decreasing RIN. The effect of increased output current is illustrated in the step response curves in the Typical Performance Characteristics of this data sheet. Note that the curves are labeled with respect to the initial output currents.
V+ ILOAD LOAD 8 +IN LOAD RIN 7 -IN RSENSE
Useful Equations Input Voltage: VSENSE = ISENSE * RSENSE Voltage Gain: Current Gain: VOUT R = OUT VSENSE RIN IOUT ISENSE = RSENSE RIN
Transconductance: Transimpedance:
IOUT 1 = VSENSE RIN VOUT = RSENSE * ROUT RIN
ISENSE
Reverse Supply Protection Some applications may be tested with reverse-polarity supplies due to an expectation of this type of fault during operation. The LTC6103 is not protected internally from
V+ ILOAD RSENSE
RIN
+-
VS
+IN
-IN 1/2 OUT LTC6103 R3 TO mP V- 1 4
+-
VS 1/2 OUT LTC6103 ROUT ADC
V-
D1 ROUT
D1
6103 F05
6103 F06
Figure 5. Schottky Prevents Damage During Supply Reversal
Figure 6. Additional Resistor, R3, Protects Output During Supply Reversal
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12
LTC6103 APPLICATIONS INFORMATION
Voltage Translator Each amplifier of the LTC6103 can be used as a high voltage level translator circuit as shown in Figure 7. In this application, the LTC6103 translates a differential voltage signal riding on top of a high common mode voltage. VIN signals get converted to a current, through RIN, and then scaled down to a ground referenced voltage across ROUT. Since the VSUPPLY must be at least 4V and the maximum input voltage is 70V, this circuit can translate differential signals with up to 66V of variation in VTRANSLATE. With the dual LTC6103, half of the device can be used to monitor a high side referenced signal and the other amplifier can be used for current sensing. Output Connection Methods The outputs of the LTC6103 are current sources and may be connected to subsequent circuitry in several ways. As a dual current sense part, each output can be used independently and in differing ways if desired. For applications where the destination is local to the device, ROUT resistors may be co-located with the part to form voltage sources. It is also possible to remotely locate
-
the ROUT resistors so that the current generated output voltage drop is developed against a different ground reference point than the LTC6103 V-, such as at an ADC within another assembly. This method provides the elimination of ground drop errors from effecting the measurement. Ground differentials that are small enough to prevent conduction of the output protection zener (>8V positive or a couple hundred mV negative) can be rejected without affecting linearity. In the Typical Application, "10A Differential Output Bidirectional Monitor," the outputs are kept separate, but are treated as a differential pair. This connection allows placing ROUT resistors local to the LTC6103, and yet ground drop errors are rejected a the destination circuit as common mode voltage shift, not signal error. This connection is also shown in the application, 10A Bidirectional H-Bridge Monitor. The outputs can also be tied together to drive a single ROUT as in the Typical Application, 5A Absolute Value Bidirectional Monitor, producing an additive function. In that particular circuit the two inputs are wired oppositely form the same sense resistor, so the resulting output is an absolute value signal.
VIN
+
RIN
VTRANSLATE
+-
VS 1/2 LTC6103 VOUT ROUT
6103 F07
Figure 7. Operation as Voltage Translator
6103f
13
LTC6103 TYPICAL APPLICATIONS
10A Differential Output Bidirectional Current Monitor
10m
5A Absolute Value Bidirectional Current Monitor
20m
+
VBATT 4V < VBATT < 60V 8 +INA 7 -INA 6 -INB 5 +INB 200 200 LOAD CHARGER VBATT
+
200 200 LOAD CHARGER
8 +INA
7 -INA
6 -INB
5 +INB
+-
VSA
-+
VSB
+-
VSA
-+
VSB
LTC6103
OUTA 1 4
V- 2
OUTB
LTC6103
OUTA 1 4
V- 2
OUTB
+ -
4.99k 4.99k
6103 TA02
DIFFERENTIAL OUTPUT* 2.5V FS (+ IS CHARGE CURRENT) +OUTPUT MAY BE TAKEN SINGLE ENDED AS CHARGE CURRENT MONITOR * -OUTPUT MAY BE TAKEN SINGLE ENDED AS DISCHARGE CURRENT MONITOR OUTPUT SWING MAY BE LIMITED FOR VBATT BELOW 6V
4.99k
6103 TA03
VOUT 2.5V FS
Intelligent High Side Switch with Current Monitor
10F 63V
48V Supply Current Monitor with Isolated Output and 70V Survivability + VSENSE -
RIN -IN RSENSE +IN ISENSE LOAD
VLOGIC 47k FAULT OFF ON 3 4 2 1F 1 5
14V
VS 100 1% -IN
8 LT1910 6
RS +IN
1/2 LTC6103
OUT
VO 4.99k
V-
-+
V+
V- SUB85N06-5 VO = 49.9 * RS * IL FOR RS = 5m, VO = 2.5V AT IL = 10A (FULL SCALE) OUT
1/2 LTC6103 VLOGIC ROUT VOUT ANY OPTOISOLATOR
LOAD
IL
6103 TA06
V-
6103 TA07
N = OPTOISOLATOR CURRENT GAIN R VOUT = VLOGIC - ISENSE * SENSE * N * ROUT RIN
6103f
14
LTC6103 PACKAGE DESCRIPTION
MS8 Package 8-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1660)
0.889 0.127 (.035 .005)
5.23 (.206) MIN
3.20 - 3.45 (.126 - .136)
0.42 0.038 (.0165 .0015) TYP
0.65 (.0256) BSC
3.00 0.102 (.118 .004) (NOTE 3)
8
7 65
0.52 (.0205) REF
RECOMMENDED SOLDER PAD LAYOUT
DETAIL "A" 0 - 6 TYP 4.90 0.152 (.193 .006) 3.00 0.102 (.118 .004) (NOTE 4)
0.254 (.010) GAUGE PLANE
1 0.53 0.152 (.021 .006) DETAIL "A" 0.18 (.007) SEATING PLANE 0.22 - 0.38 (.009 - .015) TYP 1.10 (.043) MAX
23
4 0.86 (.034) REF
0.65 (.0256) NOTE: BSC 1. DIMENSIONS IN MILLIMETER/(INCH) 2. DRAWING NOT TO SCALE 3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE 5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
0.127 0.076 (.005 .003)
MSOP (MS8) 0204
6103f
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.
15
LTC6103 TYPICAL APPLICATION
10A Bidirectional H-Bridge Current Monitor
V+ 4V TO 60V 10m 200 8 +INA 7 -INA 6 -INB 10m 200 5 +INB
+-
VSA
-+
VSB
LTC6103
OUTA 1 4
V- 2
OUTB
+
4.99k
-
4.99k
DIFFERENTIAL OUTPUT 2.5V FS (MAY BE LIMITED IF V+ < 6V) 10A FS
-
PWM*
+
PWM*
6103 TA04
*USE "SIGN-MAGNITUDE" PWM FOR ACCURATE LOAD CURRENT CONTROL AND MEASUREMENT
RELATED PARTS
PART NUMBER LT1636 LT1637/LT1638 LT1639 LT1787/LT1787HV LTC1921 LT1990 LT1991 LTC2050/LTC2051 LTC2052 LTC4150 LT6100 DESCRIPTION Rail-to-Rail Input/Output, Micropower Op Amp Single/Dual/Quad, Rail-to-Rail, Micropower Op Amp COMMENTS VCM Extends 44V Above VEE, 55A Supply Current, Shutdown Function VCM Extends 44V Above VEE, 0.4V/s Slew Rate, >1MHz Bandwidth, <250A Supply Current per Amplifier 200V Transient Protection, Drives Three Optoisolators for Status 250V Common Mode, Micropower, Pin Selectable Gain = 1, 10 2.7V to 18V, Micropower, Pin Selectable Gain = -13 to 14 3V Offset, 30nV/C Drift, Input Extends Down to V- Indicates Charge Quantity and Polarity 4.1V to 48V Operation, Pin-Selectable Gain: 10, 12.5, 20, 25, 40, 50V/V High Voltage 5V to 100V Operation, SOT23 4V to 60V Operation, Gain Configurable with External Resistors
6103f
Precision, Bidirectional, High Side Current Sense Amplifier 2.7V to 60V Operation, 75V Offset, 60A Current Draw Dual -48V Supply and Fuse Monitor High Voltage, Gain Selectable Difference Amplifier Precision, Gain Selectable Difference Amplifier Single/Dual/Quad Zero-Drift Op Amp Coulomb Counter/Battery Gas Gauge Gain-Selectable High Side Current Sense Amplifier
LTC6101/LTC6101HV High Voltage, High Side Current Sense Amplifier LTC6104 High Side Bidirectional Current Sense Amplifier
16 Linear Technology Corporation
(408) 432-1900 FAX: (408) 434-0507
LT 0107 * PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
www.linear.com
(c) LINEAR TECHNOLOGY CORPORATION 2007

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