Datasheet

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LTC6104

6104f

TYPICAL APPLICATION

FEATURES

APPLICATIONS

DESCRIPTION

High Voltage, High Side,

Bi-Directional Current

Sense Ampliﬁ er

The LTC

6104 is a versatile, high voltage, high side, bi-

directional current sense ampliﬁ er. Design ﬂ exibility is

provided by the excellent device characteristics: ±450µV

maximum offset and only 520µA of current consumption

(typical at 12V). The LTC6104 operates on supplies from

4V to 60V.

The LTC6104 monitors bi-directional current via the voltage

across an external sense resistor (shunt resistor). This

sense voltage is then translated into a ground referenced

signal. Gain is set with three external resistors and can

be separately conﬁ gured for both directions. 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 LTC6104 ideal for a wide variety of automotive, industrial

and power management applications. A maximum input

sense voltage of 500mV allows a wide range of currents

to be monitored. The fast response makes the LTC6104

the perfect choice for load current warnings and shutoff

protection control. With very low supply current, the

LTC6104 is suitable for power sensitive applications.

The LTC6104 is available in an 8-lead MSOP package.

■

Wide Supply Range: 4V to 60V with 70V Absolute

Maximum

■

Low Offset Voltage: ±450µV Maximum

■

Fast Response: 1µs Response Time

■

Gain Conﬁ gurable with External Resistors; Each

Direction is Gain Conﬁ gurable

■

Low Input Bias Current: 170nA Maximum

■

PSRR: 110dB Minimum

■

Output Current: ±1mA Maximum

■

Low Supply Current: 520µA, V

= 12V

■

Speciﬁ ed for –40°C to 125°C Temperature Range

■

Available in an 8-Lead MSOP Package

■

Current Shunt Measurement

■

Battery Monitoring

■

Remote Sensing

■

Power Management

, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

–

8 7 6

+INA

OUT

LTC6104

12V

TO µP

6104 TA01a

–INA –INB

100Ω

CHARGER/LOAD

SENSE

REF

+–

+INB

–

REF

+IN

–IN

1004-2.5

0.1µF

2.3k

LTC1286

GND

LOAD

CURRENT

MIRROR

–

CLK

OUT

2.5k

1µF

16-Bit Resolution Bi-Directional Output into LTC1286 ADC

Step Response

TIME (1µs/DIV)

1.5V

6104 G15

SENSE

–

OUT

= 100µA

OUT

= 0µA

= 25°C

= 12V

= 100Ω

OUT

= 5k

SENSE

= V

REF

= 1V

∆V

SENSE

= 100mV

Summary of content (16 pages)

PAGE 1
LTC6104 High Voltage, High Side, Bi-Directional Current Sense Amplifier DESCRIPTION FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Wide Supply Range: 4V to 60V with 70V Absolute Maximum Low Offset Voltage: ±450µV Maximum Fast Response: 1µs Response Time Gain Conﬁgurable with External Resistors; Each Direction is Gain Conﬁgurable Low Input Bias Current: 170nA Maximum PSRR: 110dB Minimum Output Current: ±1mA Maximum Low Supply Current: 520µA, VS = 12V Speciﬁed for –40°C to 125°C Temperature Range Available in an 8-Lead MSOP
PAGE 2
LTC6104 ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER INFORMATION (Note 1) Total Supply Voltage (+INB(VS) to V–) ......................70V Maximum Applied Output Voltage (OUT) ....................9V Input Current........................................................±10mA Output Short-Circuit Duration (to V–)............... Indeﬁnite Operating Temperature Range LTC6104C ............................................ –40°C to 85°C LTC6104I ............................................. –40°C to 85°C LTC6104H .....
PAGE 3
LTC6104 ELECTRICAL CHARACTERISTICS The ● denotes the speciﬁcations which apply over the full operating temperature range, otherwise speciﬁcations are at TA = 25°C. RIN = 100Ω, ROUT = 5k, 4V ≤ +INB(VS) ≤ 60V, V– = 0V, VREF = 2V for VS ≥ 6V, VREF = 0.75V for VS = 4V, unless otherwise noted. SYMBOL PARAMETER CONDITIONS IOUT(MAX) Maximum Output Current 6V ≤ VS ≤ 60V, VSENSE = ±110mV, VREF = 2V, ROUT = 1k VS = 4V, VSENSE = ±27.5mV, VREF = 0.
PAGE 4
LTC6104 TYPICAL PERFORMANCE CHARACTERISTICS Input VOS vs Temperature 50 TWO REPRESENTATIVE UNITS 60 30 40 20 0 RIN = 100Ω ROUT = 5k VIN = 5mV VOS OF INTERNAL AMPLIFIER A VOS OF INTERNAL AMPLIFIER B –40 –60 –80 –100 –40 –20 0 20 40 60 80 TEMPERATURE (°C) 10 0 –10 –20 TA = 25°C RIN = 100Ω ROUT = 5k VIN = 5mV –30 –40 VOS OF INTERNAL AMPLIFIER A VOS OF INTERNAL AMPLIFIER B 4 11 18 25 32 39 VS (V) 46 12 VS = 60V 10 4 VS = 4V 2 0 –40 –20 0 20 40 60 80 TEMPERATURE (°C) 100 120 MINIMUM OUT
PAGE 5
LTC6104 TYPICAL PERFORMANCE CHARACTERISTICS Step Response 0mV to 10mV VS Step Response 0mV to –10mV VSENSE– VS + 5mV VS + 10mV VS VS –10mV 2.5V VSENSE– VS – 5mV 2.25V 2V TA = 25°C VS = 12V RIN = 100Ω ROUT = 5k VSENSE+ = VS VREF = 2V VOUT 1.5V VOUT 1.
PAGE 6
LTC6104 TYPICAL PERFORMANCE CHARACTERISTICS Step Response Falling Edge VSENSE– 6V 5.5V Step Response Falling Edge VS + 50mV VS – 50mV 7V ∆VSENSE– = 100mV IOUT = 0µA PSRR vs Frequency 160 VSENSE– 140 VOUT 120 PSRR (dB) IOUT = –100µA 4.5V 1V 0.5V TA = 25°C VS = 12V RIN = 100Ω ROUT = 5k VSENSE+ = VS VREF = 6V VOUT 2V TA = 25°C VS = 12V RIN = 100Ω ROUT = 5k VSENSE+ = VS VREF = 4.
PAGE 7
LTC6104 BLOCK DIAGRAM – VSENSE ILOAD + RSENSE RINB 8 RINA 7 +INA 6 VS –INA 10V 5k 5k – 5k + – V+ A +INB 10V 5k + V– 5 –INB V+ B V– 10V V– OUT 1 4 6104 F01 VOUT R VOUT = VSENSE • OUT + VREF RIN ROUT + – VREF Figure 1. LTC6104 Block Diagram THEORY OF OPERATION When VSENSE is positive, an internal sense ampliﬁer loop forces –INA to have the same potential as +INA. Connecting an external resistor, RINA, in series with –INA causes a current, VSENSE/RINA, to ﬂow through RINA.
PAGE 8
LTC6104 APPLICATIONS INFORMATION 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.
PAGE 9
LTC6104 APPLICATIONS INFORMATION 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 For example, if RIN = 100Ω, then IOUT = VSENSE or 100Ω 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.
PAGE 10
LTC6104 APPLICATIONS INFORMATION From the Electrical Characteristics of the LTC6104, the output voltage range is 0.3V to 8V. If the circuit that is driven by the output limits the maximum output voltage to ≈5V, to achieve maximum dynamic range, VOUT should be 0.3V for –1mA IOUT and 5V for 1mA IOUT. ROUT = 5V – 0.3V = 2.35k, 2mA VREF = 0.3 + 5 – 0.3 = 2.65V 2 A standard 2.5V reference could be used in this example. With IOUT = ±1mA and ROUT = 2.2k, the output voltage range would equal 0.3V to 4.
PAGE 11
LTC6104 APPLICATIONS INFORMATION If the maximum output current, IOUT, is limited to 1mA, ROUT equals 3V/1mA = 3k and RIN = 3k/6 – 0.3Ω (internal device resistance) = 499.7Ω. The output error due to DC offset is ±510µV (typ) and the error due to offset current, IOS, is 3k • 100nA = 300µV(typ). The maximum output error can therefore reach ±810µV or 0.027% (–71dB) of the output full scale.
PAGE 12
LTC6104 APPLICATIONS INFORMATION the high current path, as this will increase the voltage drop and escalate this error. Output Current Limitations Due to Power Dissipation The LTC6104 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.
PAGE 13
LTC6104 APPLICATIONS INFORMATION Reverse Supply Protection Some applications may be tested with reverse-polarity supplies due to an expectation of this type of fault during operation. The LTC6104 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 6). This will limit the reverse current through the LTC6104.
PAGE 14
LTC6104 APPLICATIONS INFORMATION 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. sense ampliﬁers is furnished via the +INB pin, the input protection for both sections is referenced to this one pin. Normal operation of section A is maintained for +INA and –INA voltages within the range of 0.5V above +INB to 1.5V below +INB.
PAGE 15
LTC6104 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 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 1 0.53 ± 0.152 (.021 ± .006) DETAIL “A” 2 3 4 1.10 (.043) MAX 0.86 (.
PAGE 16
LTC6104 TYPICAL APPLICATION LTC6104 Bi-Directional Current Sense Circuit with Combined Charge/Discharge Output ICHARGE – CHARGER VSENSE + RSENSE IDISCHARGE RIN RIN 8 7 +INA ILOAD 6 –INA 5 –INB +INB + – – + A B VS VS LOAD LTC6104 CURRENT MIRROR OUT 1 + V– 4 + ROUT VOUT – + – VREF 6104 TA03 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 LT163