Datasheet

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LT6106

6106fa

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

36V Low Cost High Side

Current Sense in a SOT-23

The LT

6106 is a versatile high side current sense ampli-

ﬁ er. Design ﬂ exibility is provided by the excellent device

characteristics: 250μV maximum offset and 40nA maxi-

mum 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.

■

Gain Conﬁ gurable 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 Proﬁ le (1mm) ThinSOT

Package

■

Current Shunt Measurement

■

Battery Monitoring

■

Power Management

■

Motor Control

■

Lamp Monitoring

■

Overcurrent and Fault Detection

LT6106

OUT

200mV/A

6106 TA01a

100Ω

3V TO 36V

LOAD

0.02Ω

–

OUT

–IN+IN

3V to 36V, 5A Current Sense with A

= 10

, 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.

Measurement Accuracy vs Load Current

LOAD CURRENT (A)

–1.2

ACCURACY (% OF FULL SCALE)

–1.0

–0.6

–0.4

–0.2

0.6

6106 TA01b

–0.8

0.2

0.4

LIMIT OVER TEMPERATURE

TYPICAL PART AT T

= 25°C

5A FULL SCALE

SENSE

= 0.02Ω

= 10

= 100Ω

OUT

= 1k

= 3V

Summary of content (12 pages)

PAGE 1
LT6106 36V Low Cost High Side Current Sense in a SOT-23 FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTION Gain Conﬁgurable with Two Resistors Low Offset Voltage: 250μV Maximum Output Current: 1mA Maximum Supply Range: 2.
PAGE 2
LT6106 ABSOLUTE MAXIMUM RATINGS PIN CONFIGURATION (Note 1) 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...............................................
PAGE 3
LT6106 ELECTRICAL CHARACTERISTICS 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.
PAGE 4
LT6106 TYPICAL PERFORMANCE CHARACTERISTICS Power Supply Rejection Ratio vs Frequency 120 110 –0.10 V+ = 36V –0.15 V+ = 12V –0.20 V+ = 5V –0.25 –0.30 V+ = 2.7V –0.35 –0.40 –0.45 VOUT = 1V IOUT = 1mA ROUT = 1k TYPICAL UNIT –0.50 –0.55 –0.60 –45 –25 –5 V+ = 12.5V AV = 20 RIN = 100Ω ROUT = 2k 100 90 80 70 60 50 40 30 20 10 0 100 15 35 55 75 95 115 130 TEMPERATURE (°C) VOUT = 0.5V VOUT = 1V VOUT = 2V 1k 10k 100k FREQUENCY (Hz) Gain Error Distribution 16 14 12 10 8 6 4 2 0 –0.60 –0.48 –0.
PAGE 5
LT6106 TYPICAL PERFORMANCE CHARACTERISTICS Step Response 0mV to 100mV (RIN = 100Ω) Step Response 10mV to 100mV (RIN = 100Ω) Step Response 50mV to 100mV (RIN = 500Ω) VSENSE 200mV/DIV VSENSE 200mV/DIV VSENSE 100mV/DIV VOUT 2V/DIV VOUT 2V/DIV VOUT 500mV/DIV 0V 0V 0V 6106 G1 AV = 100 5μs/DIV VOUT = 0V TO 10V ROUT = 10k V+ = 12V 6106 G1 AV = 100 5μs/DIV VOUT = 1V TO 10V ROUT = 10k V+ = 12V Step Response 0mV to 50mV (RIN = 500Ω) AV = 20 VOUT = 1V TO 2V ROUT = 10k V+ = 12V Step Response 50mV to 5
PAGE 6
LT6106 TYPICAL PERFORMANCE CHARACTERISTICS Output Voltage vs Input Sense Voltage (0mV ≤ VSENSE ≤ 1V) 12 12 V+ = 12V AV = 100 RIN = 100Ω ROUT = 10k 10 AV = 20 RIN = 500Ω ROUT = 10k 10 100 8 VOUT (V) 8 VOUT (V) Supply Current vs Supply Voltage 120 V+ = 12V SUPPLY CURRENT (μA) Output Voltage vs Input Sense Voltage (0mV ≤ VSENSE ≤ 200mV) 6 6 4 4 2 2 0 40 TA = –40°C TA = 25°C TA = 70°C TA = 125°C 0 0 100 200 300 400 500 600 700 800 900 1000 VSENSE (mV) 20 40 60 80 100 120 140 160 180 200
PAGE 7
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.
PAGE 8
LT6106 APPLICATIONS INFORMATION magnitude. A sense resistor with integrated Kelvin sense terminals will give the best results. Figure 2 illustrates the recommended method. + V RSENSE RIN +IN 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.
PAGE 9
LT6106 APPLICATIONS INFORMATION V+ 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.
PAGE 10
LT6106 APPLICATIONS INFORMATION power dissipation is 41mW. This amount of power dissipation will result in a 10°C rise in junction temperature above the ambient temperature. It is important to note that the LT6106 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 sense resistor and RIN– and, if input fault conditions exist, external clamps.
PAGE 11
LT6106 APPLICATIONS INFORMATION In addition, if the output of the LT6106 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 LT6106’s output should be connected through a resistor or Schottky diode (Figure 7). Response Time The photos in the Typical Performance Characteristics show the response of the LT6106 to a variety of input conditions and values of RIN.
PAGE 12
LT6106 TYPICAL APPLICATION Simple 400V Current Monitor DANGER! Lethal Potentials Present — Use Caution ISENSE VSENSE – 400V + RSENSE +IN L O A D V– –IN + – RIN 100Ω DANGER!! HIGH VOLTAGE!! V+ OUT LT6106 12V CMPZ12L M1 VOUT M1 AND M2 ARE FQD3P50 ROUT VOUT = • VSENSE = 49.9 VSENSE RIN M2 ROUT 4.