LT1999IMS8-10#PBF - ANALOG DEVICES

LT1999-10/LT1999-20/

LT1999-50

Rev. E

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TYPICAL APPLICATION

FEATURES DESCRIPTION

High Voltage, Bidirectional

Current Sense Amplifier

The LT

1999 is a high speed precision current sense

amplifier, designed to monitor bidirectional currents over

a wide common mode range. The LT1999 is offered in

three gain options: 10V/V, 20V/V, and 50V/V.

The LT1999 senses current via an external resistive shunt

and generates an output voltage, indicating both mag-

nitude and direction of the sensed current. The output

voltage is referenced halfway between the supply voltage

and ground, or an external voltage can be used to set

the reference level. With a 2MHz bandwidth and a com-

mon mode input range of –5V to 80V, the LT1999 is suit-

able for monitoring currents in H-Bridge motor controls,

switching power supplies, solenoid currents, and battery

charge currents from full charge to depletion.

The LT1999 operates from an independent 5V supply and

draws 1.55mA. A shutdown mode is provided for mini-

mizing power consumption.

The LT1999 is available in an 8-lead SOP, an 8-lead MSOP

(original pinout), or an 8-lead pinout option engineered

for FMEA.

APPLICATIONS

n Buffered Output with 3 Gain Options:

10V/V, 20V/V, 50V/V

n Gain Accuracy: 0.5% Max

n Input Common Mode Voltage Range: –5V to 80V

n AC CMRR > 80dB at 100kHz

n Input Offset Voltage: 1.5mV Max

n –3dB Bandwidth: 2MHz

n Smooth, Continuous Operation Over Entire Common

Mode Range

n 4kV HBM Tolerant and 1kV CDM Tolerant

n Low Power Shutdown <10µA

n –55°C to 150°C Operating Temperature Range

n 8-Lead MSOP and 8-Lead SO (Narrow) Packages

n 8-Lead MSOP Pinout Option Engineered for FMEA

n AEC-Q100 Qualified for Automotive Applications

n High Side or Low Side Current Sensing

n H-Bridge Motor Control

n Solenoid Current Sense

n High Voltage Data Acquisition

n PWM Control Loops

n Fuse/MOSFET Monitoring

Full Bridge Armature Current Monitor

TIME (10µs/DIV)

2.5V

OUT

(2V/DIV)

V+IN (20V/DIV)

1999 TA01b

VOUT

V+IN

LT1999

0.8k

160k

2µA

0.8k

SHDN

V+

1999 TA01a

–

0.1µF

VOUT

V+IN

V–IN

VREF

VSHDN

V+

All registered trademarks and trademarks are the property of their respective owners.

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

ABSOLUTE MAXIMUM RATINGS

Differential Input Voltage

+IN to –IN (Notes 1, 3) ................................. ±60V, 10ms

+IN to GND, –IN to GND (Note 2) ............. –5.25V to 88V

Total Supply Voltage (V+ to GND) ................................ 6V

Input Voltage Pins 6 and 8 ................... V+ + 0.3V, –0.3V

Output Short-Circuit Duration (Note 4) ............ Indefinite

Operating Ambient Temperature (Note 5)

LT1999C ..............................................–40°C to 85°C

LT1999I ................................................–40°C to 85°C

LT1999H ............................................ –40°C to 125°C

LT1999MP ......................................... –55°C to 150°C

(Note 1)

ORIGINAL MSOP PINOUT

V+

+IN

–IN

V+

SHDN

OUT

REF

GND

TOP VIEW

MS8 PACKAGE

8-LEAD PLASTIC MSOP

TJMAX = 150°C, θJA = 300°C/W

MSOP PINOUT ENGINEERED FOR FMEA

+IN

–IN

V+

SHDN

OUT

REF

GND

TOP VIEW

MS8 PACKAGE

8-LEAD PLASTIC MSOP

TJMAX = 150°C, θJA = 300°C/W

TOP VIEW

SHDN

OUT

REF

GND

V+

+IN

–IN

V+

S8 PACKAGE

8-LEAD PLASTIC SO

TJMAX = 150°C, θJA = 190°C/W

PIN CONFIGURATION

ORDER INFORMATION

LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE

LT1999CMS8-10#PBF LT1999CMS8-10#TRPBF LTFPB 8-Lead Plastic MSOP 0°C to 70°C

LT1999IMS8-10#PBF LT1999IMS8-10#TRPBF LTFPB 8-Lead Plastic MSOP –40°C to 85°C

LT1999HMS8-10#PBF LT1999HMS8-10#TRPBF LTFPB 8-Lead Plastic MSOP –40°C to 125°C

LT1999MPMS8-10#PBF LT1999MPMS8-10#TRPBF LTFQP 8-Lead Plastic MSOP –55°C to 150°C

LT1999CMS8-10F#PBF LT1999CMS8-10F#TRPBF LTGVB 8-Lead MSOP FMEA Pinout 0°C to 70°C

LT1999IMS8-10F#PBF LT1999IMS8-10F#TRPBF LTGVB 8-Lead MSOP FMEA Pinout –40°C to 85°C

LT1999HMS8-10F#PBF LT1999HMS8-10F#TRPBF LTGVB 8-Lead MSOP FMEA Pinout –40°C to 125°C

LT1999MPMS8-10F#PBF LT1999MPMS8-10F#TRPBF LTGVB 8-Lead MSOP FMEA Pinout –55°C to 150°C

LT1999CS8-10#PBF LT1999CS8-10#TRPBF 199910 8-Lead Plastic SO 0°C to 70°C

LT1999IS8-10#PBF LT1999IS8-10#TRPBF 199910 8-Lead Plastic SO –40°C to 85°C

LT1999HS8-10#PBF LT1999HS8-10#TRPBF 199910 8-Lead Plastic SO –40°C to 125°C

LT1999MPS8-10#PBF LT1999MPS8-10#TRPBF 99MP10 8-Lead Plastic SO –55°C to 150°C

LT1999CMS8-20#PBF LT1999CMS8-20#TRPBF LTFNZ 8-Lead Plastic MSOP 0°C to 70°C

LT1999IMS8-20#PBF LT1999IMS8-20#TRPBF LTFNZ 8-Lead Plastic MSOP –40°C to 85°C

LT1999HMS8-20#PBF LT1999HMS8-20#TRPBF LTFNZ 8-Lead Plastic MSOP –40°C to 125°C

Specified Temperature Range (Note 6)

LT1999C .................................................. 0°C to 70°C

LT1999I ................................................–40°C to 85°C

LT1999H ............................................ –40°C to 125°C

LT1999MP ......................................... –55°C to 150°C

Junction Temperature ........................................... 150°C

Storage Temperature Range .................. –65°C to 150°C

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE

LT1999MPMS8-20#PBF LT1999MPMS8-20#TRPBF LTFQQ 8-Lead Plastic MSOP –55°C to 150°C

LT1999CMS8-20F#PBF LT1999CMS8-20F#TRPBF LTGVC 8-Lead MSOP FMEA Pinout 0°C to 70°C

LT1999IMS8-20F#PBF LT1999IMS8-20F#TRPBF LTGVC 8-Lead MSOP FMEA Pinout –40°C to 85°C

LT1999HMS8-20F#PBF LT1999HMS8-20F#TRPBF LTGVC 8-Lead MSOP FMEA Pinout –40°C to 125°C

LT1999MPMS8-20F#PBF LT1999MPMS8-20F#TRPBF LTGVC 8-Lead MSOP FMEA Pinout –55°C to 150°C

LT1999CS8-20#PBF LT1999CS8-20#TRPBF 199920 8-Lead Plastic SO 0°C to 70°C

LT1999IS8-20#PBF LT1999IS8-20#TRPBF 199920 8-Lead Plastic SO –40°C to 85°C

LT1999HS8-20#PBF LT1999HS8-20#TRPBF 199920 8-Lead Plastic SO –40°C to 125°C

LT1999MPS8-20#PBF LT1999MPS8-20#TRPBF 99MP20 8-Lead Plastic SO –55°C to 150°C

LT1999CMS8-50#PBF LT1999CMS8-50#TRPBF LTFPC 8-Lead Plastic MSOP 0°C to 70°C

LT1999IMS8-50#PBF LT1999IMS8-50#TRPBF LTFPC 8-Lead Plastic MSOP –40°C to 85°C

LT1999HMS8-50#PBF LT1999HMS8-50#TRPBF LTFPC 8-Lead Plastic MSOP –40°C to 125°C

LT1999MPMS8-50#PBF LT1999MPMS8-50#TRPBF LTFQR 8-Lead Plastic MSOP –55°C to 150°C

LT1999CMS8-50F#PBF LT1999CMS8-50F#TRPBF LTGVD 8-Lead MSOP FMEA Pinout 0°C to 70°C

LT1999IMS8-50F#PBF LT1999IMS8-50F#TRPBF LTGVD 8-Lead MSOP FMEA Pinout –40°C to 85°C

LT1999HMS8-50F#PBF LT1999HMS8-50F#TRPBF LTGVD 8-Lead MSOP FMEA Pinout –40°C to 125°C

LT1999MPMS8-50F#PBF LT1999MPMS8-50F#TRPBF LTGVD 8-Lead MSOP FMEA Pinout –55°C to 150°C

LT1999CS8-50#PBF LT1999CS8-50#TRPBF 199950 8-Lead Plastic SO 0°C to 70°C

LT1999IS8-50#PBF LT1999IS8-50#TRPBF 199950 8-Lead Plastic SO –40°C to 85°C

LT1999HS8-50#PBF LT1999HS8-50#TRPBF 199950 8-Lead Plastic SO –40°C to 125°C

LT1999MPS8-50#PBF LT1999MPS8-50#TRPBF 99MP50 8-Lead Plastic SO –55°C to 150°C

AUTOMOTIVE PRODUCTS**

LT1999HMS8-10F#WPBF LT1999HMS8-10F#WTRPBF LTGVB 8-Lead MSOP FMEA Pinout –40°C to 125°C

LT1999HMS8-20F#WPBF LT1999HMS8-20F#WTRPBF LTGVC 8-Lead MSOP FMEA Pinout –40°C to 125°C

LT1999HMS8-50F#WPBF LT1999HMS8-50F#WTRPBF LTGVD 8-Lead MSOP FMEA Pinout –40°C to 125°C

Contact the factory for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.

Tape and reel specifications. Some packages are available in 500 unit reels through designated sales channels with #TRMPBF suffix.

**Versions of this part are available with controlled manufacturing to support the quality and reliability requirements of automotive applications. These

models are designated with a #W suffix. Only the automotive grade products shown are available for use in automotive applications. Contact your

local Analog Devices account representative for specific product ordering information and to obtain the specific Automotive Reliability reports for

thesemodels.

ORDER INFORMATION

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

ELECTRICAL CHARACTERISTICS

The l denotes the specifications which apply over the full operating

temperature range, 0°C < TA < 70°C for C-grade parts, –40°C < TA < 85°C for I-grade parts, and –40°C < TA < 125°C for H-grade parts, otherwise

specifications are at TA = 25°C. V+ = 5V, GND = 0V, VCM = 12V, VREF = floating, VSHDN = floating, unless otherwise specified. See Figure2.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VSENSE Full-Scale Input Sense Voltage (Note 7)

VSENSE = V+IN – V–IN

LT1999-10

LT1999-20

LT1999-50

–0.35

–0.2

–0.08

0.35

0.2

0.08

VCM CM Input Voltage Range l–5 80 V

RIN(DIFF) Differential Input Impedance ΔVINDIFF = ±2V/Gain l6.4 8 9.6 kΩ

RINCM CM Input Impedance ΔVCM = 5.5V to 80V

ΔVCM = –5V to 4.5V

3.6

4.8

MΩ

kΩ

VOSI Input Referred Voltage Offset

–750

–1500

±500 750

1500

μV

ΔVOSI /ΔT Input Referred Voltage Offset Drift 5 μV/°C

AVGain LT1999-10

LT1999-20

LT1999-50

9.95

19.9

49.75

10.05

20.1

50.25

V/V

AV Error Gain Error ΔVOUT = ±2V l–0.5 ±0.2 0.5 %

IBInput Bias Current

I(+IN) = I(–IN)

(Note 8)

VCM > 5.5V

VCM = –5V

VSHDN = 0.5V, 0V < VCM < 80V

100

–2.35

137.5

–1.95

0.001

175

–1.5

2.5

μA

IOS Input Offset Current

IOS = I(+IN) – I(–IN)

(Note 8)

VCM > 5.5V

VCM = –5V

VSHDN = 0.5V, 0V < VCM < 80V

–1

–10

–2.5

2.5

μA

PSRR Supply Rejection Ratio V+ = 4.5V to 5.5V l68 77 dB

CMRR Sense Input Common Mode Rejection VCM = –5V to 80V

VCM = –5V to 5.5V

VCM = 12V, 7VP-P, f = 100kHz,

VCM = 0V, 7VP-P, f = 100kHz

105

120

100

enDifferential Input Referred Noise Voltage Density f = 10kHz

f = 0.1Hz to 10Hz

nV/√Hz

μVP-P

REFRR REF Pin Rejection, V+ = 5.5V

ΔVREF = 3.0V

ΔVREF = 3.25V

LT1999-10

LT1999-20

LT1999-50

RREF REF Pin Input Impedance

VSHDN = 0.5V

0.15

0.4

100

0.65

kΩ

MΩ

VREF Open Circuit Voltage

VSHDN = 0.5V

2.45

2.5

2.55

2.75

VREFR REF Pin Input Range (Note 9) LT1999-10

LT1999-20

LT1999-50

1.25

1.125

V+ – 1.25

V+ – 1.125

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

ELECTRICAL CHARACTERISTICS

The l denotes the specifications which apply over the full operating

temperature range, 0°C < TA < 70°C for C-grade parts, –40°C < TA < 85°C for I-grade parts, and –40°C < TA < 125°C for H-grade parts, otherwise

specifications are at TA = 25°C. V+ = 5V, GND = 0V, VCM = 12V, VREF = floating, VSHDN = floating, unless otherwise specified. See Figure2.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

ISHDN Pin Pull-Up Current V+ = 5.5V, VSHDN = 0V l–6 –2 μA

VIH SHDN Pin Input High lV+ – 0.5 V

VIL SHDN Pin Input Low l0.5 V

f3dB Small Signal Bandwidth LT1999-10

LT1999-20

LT1999-50

1.2

MHz

SR Slew Rate 3 V/μs

tsSettling Time due to Input Step, ΔVOUT = ±2V 0.5% Settling 2.5 μs

trCommon Mode Step Recovery Time

ΔVCM = ±50V, 20ns

(Note 10)

LT1999-10

LT1999-20

LT1999-50

0.8

1.3

μs

VSSupply Voltage (Note 11) l4.5 5 5.5 V

ISSupply Current VCM > 5.5V

VCM = –5V

V+ = 5.5V, VSHDN = 0.5V, VCM > 0V

1.55

5.8

1.9

7.1

μA

ROOutput Impedance ΔIO = ±2mA 0.15 Ω

ISRC Sourcing Output Current RLOAD = 50Ω to GND l6 31 40 mA

ISNK Sinking Output Current RLOAD = 50Ω to V+l15 26 40 mA

VOUT Swing Output High (with Respect to V+) RLOAD = 1kΩ to Mid-Supply

RLOAD = Open

125

250

125

Swing Output Low (with Respect to V–) RLOAD = 1kΩ to Mid-Supply

RLOAD = Open

250

150

400

225

tON Turn-On Time VSHDN = 0V to 5V 1 μs

tOFF Turn-Off Time VSHDN = 5V to 0V 1 μs

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

ELECTRICAL CHARACTERISTICS

The l denotes the specifications which apply over the full operating

temperature range, –55°C < TA < 150°C for MP-grade parts, otherwise specifications are at TA = 25°C. V+ = 5V, GND = 0V, VCM = 12V,

VREF = floating, VSHDN = floating, unless otherwise specified. See Figure2.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

VSENSE Full-Scale Input Sense Voltage (Note 7)

VSENSE = V+IN – V–IN

LT1999-10

LT1999-20

LT1999-50

–0.35

–0.2

–0.08

0.35

0.2

0.08

VCM CM Input Voltage Range l–5 80 V

RIN(DIFF) Differential Input Impedance ΔVINDIFF = ±2V/GAIN l6.4 8 9.6 kΩ

RINCM CM Input Impedance ΔVCM = 5.5V to 80V

ΔVCM = –5V to 4.5V

3.6

4.8

MΩ

kΩ

VOSI Input Referred Voltage Offset

–750

–2000

±500 750

2000

μV

ΔVOSI/ΔT Input Referred Voltage Offset Drift 8 μV/°C

AVGain LT1999-10

LT1999-20

LT1999-50

9.95

19.9

49.75

10.05

20.1

50.25

V/V

AV Error Gain Error ΔVOUT = ±2V l–0.5 ±0.2 0.5 %

IBInput Bias Current

I(+IN) = I(–IN)

(Note 8)

VCM > 5.5V

VCM = –5V

VSHDN = 0.5V, 0V < VCM < 80V

100

–2.35

137.5

–1.95

0.001

180

–1.5

μA

IOS Input Offset Current

IOS = I(+IN) – I(–IN)

(Note 8)

VCM > 5.5V

VCM = –5V

VSHDN = 0.5V, 0V < VCM < 80V

–1

–10

μA

PSRR Supply Rejection Ratio V+ = 4.5V to 5.5V l68 77 dB

CMRR Sense Input Common Mode Rejection VCM = –5V to 80V

VCM = –5V to 5.5V

VCM = 12V, 7VP-P, f = 100kHz,

VCM = 0V, 7VP-P, f = 100kHz

105

120

100

enDifferential Input Referred Noise Voltage Density f= 10kHz

f = 0.1Hz to 10Hz

nV/√Hz

μVP-P

REFRR REF Pin Rejection, V+ = 5.5V

ΔVREF = 2.75V

ΔVREF = 3.25V

LT1999-10

LT1999-20

LT1999-50

RREF REF Pin Input Impedance

VSHDN = 0.5V

0.15

0.4

100

0.65

kΩ

MΩ

VREF Open Circuit Voltage

VSHDN = 0.5V

2.45

0.25

2.5

2.55

2.75

VREFR REF Pin Input Range (Note 9) LT1999-10

LT1999-20

LT1999-50

1.5

1.125

V+ – 1.25

V+ – 1.125

ISHDN Pin Pull-Up Current V+ = 5.5V, VSHDN = 0V l–6 –2 μA

VIH SHDN Pin Input High lV+ – 0.5 V

VIL SHDN Pin Input Low l0.5 V

f3dB Small Signal Bandwidth LT1999-10

LT1999-20

LT1999-50

1.2

MHz

SR Slew Rate 3 V/μs

tSSettling Time Due to Input Step, ΔVOUT = ±2V 0.5% Settling 2.5 μs

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

ELECTRICAL CHARACTERISTICS

Note 1: Stresses beyond those listed underAbsolute 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: Pin 2 (+IN) and Pin 3 (–IN) are protected by ESD voltage clamps

which have asymmetric bidirectional breakdown characteristics with respect

to the GND pin (Pin 5). These pins can safely support common mode

voltages which vary from –5.25V to 88V without triggering an ESD clamp.

Note 3: Exposure to differential sense voltages exceeding the normal

operating range for extended periods of time may degrade part

performance. A heat sink may be required to keep the junction temperature

below the Absolute Maximum Rating when the inputs are stressed

differentially. The amount of power dissipated in the LT1999 due to input

overdrive can be approximated by:

DISS =V+IN −V−IN

( )

8kΩ

Note 4: A heat sink may be required to keep the junction temperature

below the absolute maximum rating.

Note 5: The LT1999C/LT1999I are guaranteed functional over the operating

temperature range –40°C to 85°C. The LT1999H is guaranteed functional

over the operating temperature range –40°C to 125°C. The LT1999MP is

guaranteed functional over the operating temperature range –55°C to 150°C.

Junction temperatures greater than 125°C will promote accelerated aging.

The LT1999 has a demonstrated typical life beyond 1000 hours at 150°C.

Note 6: The LT1999C is guaranteed to meet specified performance from

0°C to 70°C. The LT1999C is designed, characterized, and expected to

meet specified performance from –40°C to 85°C but is not tested or

QA sampled at these temperatures. The LT1999I is guaranteed to meet

specified performance from –40°C to 85°C. The LT1999H is guaranteed

to meet specified performance from –40°C to 125°C. The LT1999MP is

guaranteed to meet specified performance from –55°C to 150°C.

Note 7: Full-scale sense (VSENSE) gives indication of the maximum

differential input that can be applied with better than 0.5% gain accuracy.

Gain accuracy is degraded when the output saturates against either power

supply rail. VSENSE is verified with V+ = 5.5V, VCM = 12V, with the REF pin

set to it’s voltage range limits. The maximum VSENSE is verified with the

REF pin set to it’s minimum specified limit, verifying the gain error is less

than 0.5% at the output. The minimum VSENSE is verified with the REF pin

set to its maximum specified limit, verifying the gain error at the output is

less than 0.5%. See Note 9 for more information.

Note 8: IB is defined as the average of the input bias currents to the +IN

and –IN pins (Pins 2 and 3). A positive current indicates current flowing

into the pin. IOS is defined as the difference of the input bias currents.

IOS = I(+IN) – I(–IN)

Note 9: The REF pin voltage range is the minimum and maximum limits

that ensures the input referred voltage offset does not exceed ±3mV over

the I, C, and H temperature ranges, and ±3.5mV over the MP temperature

range.

Note 10: Common mode recovery time is defined as the time it takes the

output of the LT1999 to recover from a 50V, 20ns input common mode

voltage transition, and settle to within the DC amplifier specifications.

Note 11: Operating the LT1999 with V+ < 4.5V is possible, although the

LT1999 is not tested or specified in this condition. See the Applications

Information section.

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

trCommon Mode Step Recovery Time

ΔVCM = ±50V, 20ns

(Note 10)

LT1999-10

LT1999-20

LT1999-50

0.8

1.3

μs

VSSupply Voltage (Note 11) l4.5 5 5.5 V

ISSupply Current VCM > 5.5V

VCM = –5V

V+ = 5.5V, VSHDN = 0.5V, VCM > 0V

1.55

5.8

1.9

7.1

μA

ROOutput Impedance ΔIO = ±2mA 0.15 Ω

ISRC Sourcing Output Current RLOAD = 50Ω to GND l3 31 40 mA

ISNK Sinking Output Current RLOAD = 50Ω to V+l10 26 40 mA

VOUT Swing Output High (with Respect to V+) RLOAD = 1kΩ to Mid-Supply

RLOAD = Open

125

250

125

Swing Output Low (with Respect to V–) RLOAD = 1kΩ to Mid-Supply

RLOAD = Open

250

150

400

225

tON Turn-On Time VSHDN = 0V to 5V 1 μs

tOFF Turn-Off Time VSHDN = 5V to 0V 1 μs

The l denotes the specifications which apply over the full operating

temperature range, –55°C < TA < 150°C for MP-grade parts, otherwise specifications are at TA = 25°C. V+ = 5V, GND = 0V, VCM = 12V,

VREF = floating, VSHDN = floating, unless otherwise specified. See Figure2.

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

TYPICAL PERFORMANCE CHARACTERISTICS

Input Bias Current

vs Input Common Mode Input Bias Current vs Temperature

Input Impedance

vs Input Common Mode Voltage

VCM (V)

–5

IB (mA)

0.5

–1.0

–1.5

–0.5

–2.0 4525 65

1999 G07

75 8035155 55

V+ = 5V

TEMPERATURE (°C)

–55

IB (µA)

146

144

140

134

136

138

142

132 70

20 120

1999 G08

14545–5–30 95

VCM = 80V

VCM = 5.5V

VSHDN = OPEN

VINDIFF = 0V

V+ = 5V

VCM (V)

–5

IMPEDANCE (kΩ)

100000

10000

100

1000

14525 65

1999 G09

7535155 55

COMMON MODE INPUT

IMPEDANCE

DIFFERENTIAL INPUT IMPEDANCE

Supply Current

vs SHDN Pin Voltage

Shutdown Supply Current

vs Temperature

Shutdown Input Bias Current

vs Input Common Mode

Supply Current

vs Input Common Mode Supply Current vs Temperature Supply Current vs Supply Voltage

VCM (V)

–5

IS (mA)

04525 65

1999 G01

75 8035155 55

V+ = 5V

TEMPERATURE (°C)

–55

IS (mA)

1.8

1.7

1.5

1.6

1.4 7020 120

1999 G02

14545–5–30 95

V+ = 5.5V

V+ = 4.5V

VSHDN = OPEN

VINDIFF = 0V

VCM = 12V

SUPPLY VOLTAGE (V)

(mA)

4.0

3.0

1.0

2.0

3.5

1.5

2.5

0.5

2 4

1999 G03

51 3

VCM = 12V

150°C

130°C

90°C

25°C

–45°C

–55°C

VSHDN (V)

IS (mA)

0.1

0.001

0.01

2 4

1999 G04

51 3

TA = 25°C

TA = 150°C

TA = –55°C

V+ = 5V

VCM = 12V

TEMPERATURE (°C)

–55

IS (µA)

07020 120

1999 G05

14545–5–30 95

V+ = 5.5V

V+ = 4.5V

VSHDN = 0V

VINDIFF = 0V

VCM = 12V

VCM (V)

(nA)

1000

100

140 80

1999 G06

10020 60

V+ = 5V

VSHDN = 0V

VSENSE = 0V

TA = 70°C

TA = 90°C

TA = 150°C

TA =110°C

TA =130°C

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

TYPICAL PERFORMANCE CHARACTERISTICS

LT1999-10 Small Signal

Frequency Response

Gain Error vs Temperature

Gain Error

vs Input Common Mode Voltage

Input Referred Voltage Offset

vs Temperature and Gain Option

Input Referred Voltage Offset

vs Input Common Mode Voltage

TEMPERATURE (°C)

–55

VOSI (µV)

1500

1000

–500

–1000

500

–1500 7020 120

1999 G10

14545–5–30 95

LT1999-10

LT1999-20

LT1999-50

VCM = 12V

12 UNITS PLOTTED

VCM (V)

–5

VOSI (µV)

1500

1000

–500

–1000

500

–1500 4525 65

1999 G11

7535155 55

V+ = 5V

TA = 25°C

12 UNITS PLOTTED

LT1999-10

LT1999-20

LT1999-50

TEMPERATURE (°C)

–55

GAIN ERROR (%)

0.50

0.25

–0.25

–0.50 7020 120

1999 G15

14545–5–30 95

VCM = 12V

12 UNITS PLOTTED

LT1999-10

LT1999-20

LT1999-50

VCM (V)

–5

GAIN ERROR (%)

0.50

0.25

–0.25

–0.50 4525 65

1999 G16

7535155 55

V+ = 5V

TA = 25°C

12 UNITS PLOTTED

LT1999-10

LT1999-20

LT1999-50

FREQUENCY (kHz)

GAIN (dB)

PHASE (DEG)

–5

–10

180

–90

–135

135

–45

–180

10 1000

1999 G12

10000100

VOUT = 0.5VP-P AT 1kHz

GAIN

PHASE

LT1999-50 Small Signal

Frequency Response

LT1999-20 Small Signal

Frequency Response

FREQUENCY (kHz)

GAIN (dB)

PHASE (DEG)

–5

180

–90

–135

135

–45

GAIN

–180

10 1000

1999 G13

10000100

VOUT = 0.5VP-P AT 1kHz

PHASE

FREQUENCY (kHz)

GAIN (dB)

PHASE (DEG)

180

–90

–135

135

–45

GAIN

PHASE

–180

10 1000

1999 G14

10000100

VOUT = 0.5VP-P AT 1kHz

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

TYPICAL PERFORMANCE CHARACTERISTICS

CMRR vs FrequencyCMRR vs Frequency

FREQUENCY (kHz)

CMRR (dB)

120

100

01000

1999 G23

1000010010

VCM = 12V

V+ = 5V

TA = 25°C

6 UNITS PLOTTED

LT1999-10

LT1999-20

LT1999-50

LT1999-50 2V Step Response

Settling Time

LT1999-10 2V Step Response

Settling Time

LT1999-20 2V Step Response

Settling Time

LT1999-50 Pulse Response

TIME (2µs/DIV)

SENSE

(0.1V/DIV)

OUT

(1V/DIV)

1999 G19

VOUT

VSENSE

VOUT

TIME (1µs/DIV)

VOUT (V)

OUTPUT ERROR (V)

4.5

3.5

1.5

2.5

0.5

4.0

2.0

3.0

1.0

0.100

0.050

–0.050

–0.100

0.075

–0.025

0.025

–0.075

1999 G20

OUTPUT ERROR

VOUT

VOUT (V)

OUTPUT ERROR (V)

4.5

3.5

1.5

2.5

0.5

4.0

2.0

3.0

1.0

0.20

0.10

–0.01

–0.20

0.15

–0.05

0.05

–0.15

OUTPUT ERROR

TIME (1µs/DIV)

–1 42 6

1999 G21

7310 5 9 108

VOUT (V)

OUTPUT ERROR (V)

4.5

3.5

1.5

2.5

0.5

4.0

2.0

3.0

1.0

0.500

0.250

–0.250

–0.500

0.375

–0.125

0.125

–0.375

TIME (1µs/DIV) 1999 G22

VOUT

OUTPUT ERROR

LT1999-10 Pulse Response LT1999-20 Pulse Response

TIME (2µs/DIV)

VSENSE (0.5V/DIV)

OUT

(1V/DIV)

1999 G17

VOUT

VSENSE

TIME (2µs/DIV)

VSENSE (0.2V/DIV)

OUT

(1V/DIV)

1999 G18

VOUT

VSENSE

FREQUENCY (kHz)

CMRR (dB)

120

100

01000100

1999 G24

1000010

VCM = 0V

V+ = 5V

TA = 25°C

6 UNITS PLOTTED

LT1999-10

LT1999-20

LT1999-50

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

LT1999-10 Common Mode Rising

Edge Step Response

VOUT (0.5V/DIV)

VCM (25V/DIV)

TIME (0.5µs/DIV) 1999 G25

VCM, tRISE ≈ 20ns

VOUT

LT1999-10 Common Mode Falling

Edge Step Response

VOUT (0.5V/DIV)

VCM (25V/DIV)

TIME (0.5µs/DIV) 1999 G26

VCM, tFALL ≈ 20ns

VOUT

VOUT (0.5V/DIV)

(25V/DIV)

TIME (0.5µs/DIV) 1999 G27

VCM, tRISE ≈ 20ns

VOUT

LT1999-20 Common Mode Rising

Edge Step Response

LT1999-20 Common Mode Falling

Edge Step Response

OUT

(0.5V/DIV)

VCM (25V/DIV)

TIME (0.5µs/DIV) 1999 G28

VCM, tFALL ≈ 20ns

VOUT

TYPICAL PERFORMANCE CHARACTERISTICS

LT1999-50 Common Mode Rising

Edge Step Response

LT1999-50 Common Mode Falling

Edge Step Response

VOUT (0.5V/DIV)

VCM (25V/DIV)

TIME (0.5µs/DIV) 1999 G29

LT1999-50 Common Mode Rising Edge

Step Response

TIME (0.5 s / div)

VOUT (0.5 V / div)

VCM (25V / div)

VCM

tRISE20ns

VCM, tRISE ≈ 20ns

VOUT

VOUT (0.5V/DIV)

VCM (25V/DIV)

TIME (0.5µs/DIV) 1999 G30

VCM, tFALL ≈ 20ns

VOUT

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

TYPICAL PERFORMANCE CHARACTERISTICS

LT1999 Input Referred Noise

Density vs Frequency

FREQUENCY (kHz)

0.001 0.01 0.1

NOISE DENSITY (nV/√Hz)

1000

100

10 1000

1999 G31

10000101

TEMPERATURE (°C)

–55

ISC (mA)

–20

–40

–10

–30

7020 120

1999 G32

14545–5–30 95

SINKING

SOURCING

TEMPERATURE (°C)

–55

REF PIN VOLTAGE (V)

3.0

2.5

1.0

2.0

1.5

0.5

7020 120

1999 G33

14545–5–30 95

SHDN MODE

ACTIVE MODE

V+ = 5V

Short-Circuit Current

vs Temperature

REF Open Circuit Voltage

vs Temperature

SHDN Pin Current vs SHDN Pin

Voltage and Temperature

Turn-On/Turn-Off Time

vs SHDN Voltage

VOUT vs VSENSE

IS (1mA/DIV)

SHDN PIN VOLTAGE (5V/DIV)

TIME (1µs/DIV) 1999 G35

VSHDN

SHUTDOWN

VCM = 12V

VSENSE (V)

–0.25

VOUT (V)

–1 –0.05 0.15

1999 G36

0.25–0.15 0.05

VREF = 2.5V

LT1999-10

LT1999-20

LT1999-50

VSHDN (V)

SHDN

(µA)

–2

–4

–1

–3

2 4 5

1999 G34

1 3

TA = 150°C

TA = 25°C

TA = –55°C

V+ = 5V

VCM = 12V

VOUT vs VSENSE Over the Sense

ABSMAX Range

VSENSE (V)

–60

VOUT (V)

–1 –30 30

1999 G37

600

VOUT PHASE REVERSAL FOR VSENSE < –25V

VREF = 2.5V

LT1999-10

LT1999-20

LT1999-50

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

PIN FUNCTIONS

V+ (Pins 1, 4/Pin 4): Power Supply Voltage. Pins 1 and 4

are tied internally together. The specified range of opera-

tion is 4.5V to 5.5V, but lower supply voltages (down to

approximately 4V) is possible although the LT1999 is not

tested or characterized below 4.5V. See the Applications

Information section.

+IN (Pin 2/Pin 1): Positive Sense Input Pin.

–IN (Pin 3/Pin 2): Negative Sense Input Pin.

NC (NA/Pin 3)

GND (Pin 5/Pin 5): Ground Pin.

REF (Pin 6/Pin 6): Reference Pin Input. The REF pin

sets the output common mode level and is set halfway

between V+ and GND using a divider made of two 160k

resistors. The default open circuit potential of the REF pin

is mid-supply. It can be overdriven by an external voltage

source cable of driving 80k to a mid-supply potential (see

the Electrical Characteristics table for its specified input

voltage range).

OUT (Pin 7/Pin 7): Voltage Output. VOUT = AV•(VSENSE ±

VOSI), where AV is the gain, and VOSI is the input referred

offset voltage. The output amplifier has a low impedance

output and is designed to drive up to 200pF capacitive

loads directly. Capacitive loads exceeding 200pF should

be decoupled with an external resistor of at least 100Ω.

SHDN (Pin 8/Pin 8): Shutdown Pin. When pulled to within

0.5V of GND (Pin 5), will place the LT1999 into low power

shutdown. If the pin is left floating, an internal 2µA pull-

up current source will place the LT1999 into the active

(amplifying) state.

(LT1999-XX/LT1999-XXF)

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

SHDN

V+

160k

1999 BD

2µA

LT1999-XXF

–

0.8k

SHDN

V+

160k

1999 BD

2µA

LT1999

–

0.8k

BLOCK DIAGRAM

Figure1. Simplified Block Diagram

TEST CIRCUIT

1999 F02

0.1µF

VOUT

VIN(DIFF)

–

VCM

VREF

VSHDN

–

LT1999F

0.8k

160k

2µA

0.8k

SHDN

V+

–

0.1µF

V+

1999 F02

0.1µF

VOUT

VIN(DIFF)

–

VCM VREF

VSHDN

–

LT1999

0.8k

160k

2µA

0.8k

SHDN

V+

–

0.1µF

V+

Figure2. Test Circuit

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

The LT1999 current sense amplifier provides accurate

bidirectional monitoring of current through a user-

selected sense resistor. The voltage generated by the

current flowing in the sense resistor is amplified by a

fixed gain of 10V/V, 20V/V or 50V/V (LT1999-10, LT1999-

20, or LT1999-50 respectively) and is level shifted to the

OUT pin. The voltage difference and polarity of the OUT

pin with respect to REF (Pin 6) indicates magnitude and

direction of the current in the sense resistor.

THEORY OF OPERATION

Refer to the Block Diagram (Figure1.

Case 1: V+ < VCM < 80V

For input common mode voltages exceeding the power

supply, one can assume D1 ofFigure1 is completely off.

The sensed voltage (V

SENSE

) is applied across Pin 2 (+IN)

and Pin 3 (–IN) to matched resistors R

+IN

and R

–IN

(nomi-

nally 4k each). The opposite ends of R+IN and R–IN are

forced to equal potentials by transconductor GIN, which

convert the differentially sensed voltage into a sensed

current. The sensed current in R+IN and R–IN is combined,

level-shifted, and converted back into a voltage by trans-

resistance amplifier AO and resistor RG. Amplifier AO

provides high open loop gain to accurately convert the

sensed current back into a voltage and to drive external

loads. The theoretical output voltage is determined by

the sensed voltage (VSENSE), and the ratio of two on-chip

resistors:

VOUT −VREF =VSENSE •

where

RIN =

+IN

−IN

nominally 4k

APPLICATIONS INFORMATION

For the LT1999-10, RG is nominally 40k. For the LT1999-20,

RG is nominally 80k, and for the LT1999-50, RG is nomi-

nally 200k.

The voltage difference between the OUT pin and the REF

pin represent both polarity and magnitude of the sensed

voltage. The noninverting input of amplifier AO is biased

by a resistive 160k to 160k divider tied between V+ and

GND to set the default REF pin bias to mid-supply.

Case 2: –5V < VCM < V+

For common mode inputs which transition or are set below

the supply voltage, diode D1 will turn on and will provide a

source of current through R+S and R–S to bias the inputs

of transconductance amplifier GIN at least 2.25V above

GND. The transition is smooth and continuous; there are

negligible changes to either gain or amplifier voltage off-

set. The only difference in amplifier operation is the bias

currents provided by D1 through R+S and R–S are steered

through the input pins, otherwise amplifier operation is

identical. The inputs to transconductance amplifier GIN

are still forced to equal potentials forcing any differential

voltages appearing at the +IN and –IN pins into a dif-

ferential current. This differential current is combined,

level-shifted, and converted back into a voltage by trans-

resistance amplifier AO and Resistor RG. Resistors R+S

and R–S are trimmed to match R+IN and R–IN respectively,

to prevent common mode to differential conversion from

occurring (to the extent of the matched trim) when the

input common mode transitions below V+.

As described in case 1, the output is determined by the

sense voltage and the ratio of two on-chip resistors:

VOUT −VREF =VSENSE •

where

RIN =

+IN

−IN

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

APPLICATIONS INFORMATION

Input Common Mode Range

The LT1999 was optimized for high common mode rejec

tion. Its input stage is balanced and fully differential,

designed to amplify differential signals and reject com-

mon mode signals. There is negligible crossover distor-

tion due to sense voltage reversals. The amplifier is most

linear in the zero-sense region.

With the V+ supply configured within the specified and

tested range (4.5V < V+ < 5.5V), the LT1999’s common

mode range extends from –5V to 80V. Pushing +IN and

–IN beyond the limits specified in the Absolute Maximum

table can turn on the voltage clamps designed to protect

the +IN and –IN pins during ESD events.

It is possible to operate the LT1999 on power supplies

as low as 4V (although it is not tested or specified below

4.5V). Operating the LT1999 on supplies below 4V will

produce erratic behavior. When operating the LT1999

with supplies as low as 4V, the common mode range for

inputs which extend below GND is reduced. Refer to the

Block Diagram (Figure1). For inputs driven below V+,

diode D1 conducts. For proper operation, the input to the

transconductor V(G+IN) must be biased at approximately

2.25V above the GND pin. V(G+IN) sits on the centertap

of a voltage divider comprised of R+S and R+IN V(G–IN)

likewise sits in the middle of the voltage divider comprised

of R–S , and R–IN). The voltage on V(G+IN) input is given

by the following equation:

V(G+IN)=V+IN•

+IN

+V+−VD1

( )

•

+IN

Setting V(G

+IN

) = 2.25V, the ratio (R

+IN

) to 5, and V

equal to 0.8V (cold temperatures), a plot of the lower input

common mode range plotted against supply is shown in

Figure3.

Output Common Mode Range

The LT1999’s output common mode level is set by the

voltage on the REF pin. The REF pin sits in the middle of

a 160k to 160k voltage divider connected between V+ and

GND which sets the default open circuit potential of the

REF pin to mid-supply. It can be overdriven by an external

voltage source capable of driving 80k tied to a mid-supply

potential. See the Electrical Characteristics table for the

REF pin’s specified input voltage range.

Differential sampling of the OUT pin with respect the REF

pin provides the best noise immunity. Measurements of

the output voltage made differentially with respect to the

REF pin will provide the highest power supply and com-

mon mode rejection. Otherwise, power supply or GND

pin disturbances are divided by the REF pin’s voltage

divider and appear directly at the noninverting input of

the trans-resistance amplifier AO and are not rejected.

If not driven by a low impedance (<100Ω), the REF pin

should be filtered with at least 1nF of capacitance to a

low impedance, low noise ground plane. This external

capacitance will also provide a charge reservoir during

high frequency sampling of the REF pin by ADC inputs

attached to this pin.

Figure3. Lower Input Common Mode vs Supply Voltage

SUPPLY VOLTAGE (V)

CM(LOWER LIMIT)

(V)

–2.0

–2.5

–3.0

–4.0

–5.0

–3.5

–4.5

–5.5

–6.0 4.754.25 5.25

1999 F03

5.54.5 5

BELOW GROUND INPUT

COMMON MODE RANGE

LIMITED BY V+

SUPPLY VOLTAGE

BELOW GROUND INPUT

COMMON MODE RANGE

LIMITED BY ESD CLAMPS

TYPICAL ESD CLAMP VOLTAGE

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

APPLICATIONS INFORMATION

Shutdown Capability

If SHDN (Pin 8) is driven to within 0.5V of GND, the LT1999

is placed into a low power shutdown state in which the

part will draw about 3μA from the V+ supply. The input

pins (+IN and –IN) will draw approximately 1nA if biased

within the range of 0V to 80V (with no differential voltage

applied). If the input pins are pulled below the GND pin,

each input appears as a diode tied to GND in series with

approximately 4k of resistance. The REF pin appears as

approximately 0.4MΩ tied to a mid-supply potential. The

output appears as reverse biased diodes tied between the

output to either V+ or GND pins.

EMI Filtering and Layout Practices

An internal 1st order differential lowpass noise/EMI sup-

pression filter with a –3dB bandwidth of 10MHz (approxi-

mately 5× the LT1999’s –3dB bandwidth) is included to

help improve the LT1999’s EMI susceptibility and to assist

with the rejection of high frequency signals beyond the

bandwidth of the LT1999 that may introduce errors. The

pole is set by the following equation:

ffilt = 1/(π•(R+IN + R–IN)•CF) ≈ 10MHz

Both the resistors and capacitors have a ±15% variation

so the pole can vary by approximately ±30% over manu-

facturing process and temperature variations.

The layout for lowest EMI/noise susceptibility is achieved

by keeping short direct connections and minimizing loop

areas (see Figure4). If the user-supplied sense resistor

cannot be placed in close proximity to the LT1999, the

surface area of the loop comprising connections of +IN

to RSENSE and back to –IN should be minimized. This

requires routing PCB traces connecting +IN to RSENSE

and –IN to R

SENSE

adjacent with one another with minimal

separation. The metal traces connecting +IN to the sense

resistor and –IN to the sense resistor should match and

use the same trace width.

Bypassing the V+ pin to the GND pin with a 0.1µF capaci-

tor with short wiring connection is recommended.

Figure4. Recommended Layout

SUPPLY BYPASS

CAPACITOR

* KEEP LOOP AREA COMPRISING RSENSE, +IN AND –IN PINS

AS SMALL AS POSSIBLE.

** REF BYPASS TIED TO A LOW NOISE, LOW IMPEDANCE

SIGNAL GROUND PLANE.

† OPTIONAL 10pF CAPACITOR TO PREVENT dV/dt EDGES

ON INPUT COUPLING TO FLOATING SHDN PIN.

FROM DC SOURCE

TO LOAD

RSENSE DIFFERENTIAL

ANALOG OUT

†

1999 F03

SHDN

OUT

REF

GND

V+

+IN

–IN

V+

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

APPLICATIONS INFORMATION

The REF pin should be either driven by a low source

impedance (<100Ω) or should be bypassed with at least

1nF to a low impedance, low noise, signal ground plane

(see Figure4). Larger bypass capacitors on both V+ pins,

and the REF pin, will extend enhanced AC CMRR, and

PSRR performance to lower frequencies. Bypassing the

REF pin to a quiet ground plane filters the V+ pin or GND

pin noise that is sensed by the REF pin voltage divider and

applied to the noninverting input of output amplifier AO.

Any common I•R drops generated by pulsating ground

currents in common with the REF pin filter capacitor can

compromise the filtering performance and should be

avoided.

If the SHDN pin is not driven and is left floating, routing

a PCB trace connecting Pins 1 and 8 under the part will

act as a shield, and will help limit edge coupling from the

inputs (Pins 2 and 3) to the SHDN pin. Periodic pulses on

the inputs with fast edges may glitch the high impedance

SHDN pin, periodically putting the part into low power

shutdown. Additional precaution against this may be

taken by adding an optional small (~10pF) capacitor may

be tied between V+ (Pin 1) and Pin 8.

Finally, when connecting the LT1999 inputs to the sense

resistor, it is important to use good Kelvin sensing prac-

tices (sensing the resistor in a way that excludes PCB

trace I•R voltage drops). For sense resistors less than

1Ω, one might consider using a 4-wire sense resistor to

sense the resistive element accurately.

Selection of the Current Sense Resistor

The external sense resistor selection presents a delicate

trade-off between power dissipation in the resistor and

current measurement accuracy.

In high current applications, the user may want to mini-

mize the power dissipated in the sense resistor. The sense

resistor current will create heat and voltage loss, degrad-

ing efficiency. As a result, the sense resistor should be as

small as possible while still providing adequate dynamic

range required by the measurement. The dynamic range

is the ratio between the maximum accurately produced

signal generated by the voltage across the sense resis-

tor, and the minimum accurately reproduced signal. The

minimum accurately reproduced signal is primarily dic-

tated by the voltage offset of the LT1999. The maximum

accurately reproduced signal is dictated by the output

swing of the LT1999.

Thus the dynamic range for the LT1999 can be thought of

the maximum sense voltage divided by the input referred

voltage offset or:

Dynamic Range =

ΔV

OUT(MAX)

GAIN• V

OSI

The above equation tells us that the dynamic range is

inversely proportional to the gain of the LT1999. Thus,

if accuracy is of greater importance than efficiency or

power loss, the LT1999-10 used with the highest valued

sense resistor possible is recommended. If efficiency,

heat generated, and power loss in the resistive shunt is

the primary concern, the LT1999-50 and the lowest value

sense resistor possible is recommended. The LT1999-20

is available for applications somewhere in between these

two extremes.

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

APPLICATIONS INFORMATION

Pinout Option Engineered for FMEA (Failure Mode and

Effects Analysis)

The LT1999 family of ICs is available with an 8-lead MSOP

pinout option engineered for FMEA (Failure Mode and

Effects Analysis): (LT1999-10F, LT1999-20F and the

LT1999-50F). See Figure5 below.

The LT1999-XXF is designed to meet the most stringent

automotive requirements and to satisfactorily survive sin-

gle faults due to the most common PCB defects: 1) open

pins due to cold solder joints and 2) adjacent pin short cir-

cuits due to adjacent pin solder bridging. The No-Connect

Pin (Pin 3) has been inserted between the input pin (–IN)

and the V+ supply pin to isolate the input voltages which

may range from –5V to 80V from solder bridging to the

V+ supply (typically 5V). Pin 3 is not connected internally

to the die and should be left unconnected.

The purpose of the FMEA is to emulate single faults and

determine whether or not they are destructive and/or

lead to conditions which could damage surrounding

components. The LT1999-XXF is configured as shown

in Figure2, with an input common mode of either 12V

or 0V. Each pin is systematically shorted to its adjacent

pin (emulating solder bridging) and the resulting effects

recorded. Each pin is then opened (emulating a cold sol-

der joint) with the resulting effects recorded.

In all instances, the LT1999-XXF recovers when these

fault conditions are removed. Furthermore, the output pin

(OUT) has been verified to never exceed the pin’s nominal

output range of 0V to 5V during fault testing.

Table1 lists the behavior which results from shorting

adjacent pins and Table2 details the behavior from open-

ing any pin.

SHDN

V+

R+IN

R–IN

300Ω

4pF

0.8k

160k

1999 F05a

2µA

OUT

REF

+IN

–IN

GND

–

4.5k

Figure5. Simplified Block Diagram of the LT1999-XXF

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

APPLICATIONS INFORMATION

Table1. Behavior due to Adjacent Pin-to-Pin Shorts for the LT1999-10F, LT1999-20F, or the LT1999-50F

Adjacent Pin Short Test: (V+ = 5V, Tested at VCM = 0V, VCM = 12V, VCM = 80V)

PIN #

Adjacent Pins

Shorted

Recovery when

Fault is removed BEHAVIOR

1 – 2 +IN – –IN YES VOUT approaches the voltage on pin VREF.

2 – 3 –IN – NC YES The circuit behaves normally.

3 – 4 NC – V+ YES The circuit behaves normally.

5 – 6 GND – REF YES VOUT follows the voltage on Pin 6 or 0V.

6 – 7 REF – OUT YES VOUT approaches 5.0V

7 – 8 OUT – SHDN YES Supply Current drops by 5%.

Table2. Behavior due to open pins for the LT1999-10F, LT1999-20F, or the LT1999-50F

Open Pin Test (V+ = 5V, Tested at VCM = 0V, VCM = 12V, VCM = 80V)

PIN # Pin Opened

Recovery when

Fault is removed BEHAVIOR

1 +IN YES VOUT may go to either V+ or GND, depending on the voltage applied to –IN. Generally, for –5V< –IN< 4V,

OUT will be near 5V. For –IN > 5V, OUT will be near 0V. In the range of 4V < –IN < 5V, OUT may go to either

V+ or GND, depending on the voltage applied to –IN. The open input (+IN) is biased internal to the IC to one

diode below V+.

2 –IN YES VOUT may go to either V+ or GND, depending on the voltage applied to +IN. Generally, for –5V < +IN < 4V,

OUT will be near 0V. For +IN > 5V, OUT will be at 5V. In the range of 4V < –IN < 5V, OUT may go to either

V+ or GND, depending on the voltage applied to +IN. The open input (–IN) is biased internal to the IC to one

diode below V+.

3 NC YES The circuit behaves normally.

4 V+YES The circuit will behave as if powered off.

5 GND YES OUT, REF will float up towards 3.9V.

6 REF YES The circuit behaves normally with more broadband noise on OUT.

7 OUT YES No VOUT signal.

8SHDN YES The low power shutdown feature will not function, otherwise the circuit behaves normally in the active state.

FMEA information in this document (not limited to, but including the description of behavior under specific pin-connection conditions) is provided for

convenience only. Ultimately, the end-user is responsible for verifying proper and reliable operation in each actual application. Linear Technology assumes

no liability whatsoever with providing this information.

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

APPLICATIONS INFORMATION

VOUT

VREF

VSHDN

LT1999

0.8k

160k

2µA

0.8k

SHDN

V+

–

V+

1999 F05

0.1µF

FUSE

STEERING

DIODE

LOAD

ILOAD

RSENSE

OFFON

VOUT

V+IN

V–IN VREF

VSHDN

Figure6. Using the LT1999 to Monitor a Fuse

Fuse Monitor

The inputs can be overdriven without fear of damaging

the LT1999. This makes the LT1999 ideal for monitoring

fuses if either +IN or –IN are shorted to ground while the

other is at the full common mode supply voltage (see

Figure6). If the fuse in Figure6 opens with the +IN tied

to the positive supply, the load will pull –IN to GND. The

output will be forced to the positive V+ supply rail. If it is

desired that the output be near ground if the fuse opens,

it is a simple matter of swapping the inputs. Precautions

should be followed: First, when the inputs are stressed

differentially due to the fuse blowing open, a large voltage

drop will be placed across the +IN to –IN pins, dissipating

power in the precision on-chip input resistors. Precaution

should be taken to prevent junction temperatures from

exceeding the Absolute Maximum ratings (see Note 3 in

the Electrical Characteristics section). Secondly, if the

load is inductive, and the fuse blows open without a clamp

diode, energy stored in the inductive load will be dissi-

pated in the LT1999, which could cause damage. A simple

steering diode as shown in Figure6 will prevent this from

happening, and will protect the LT1999 from damage.

Finally, the user should be aware that in fuse monitoring

applications with the sense voltage (V

SENSE

= V

+IN

– V

–IN

)

being driven in excess of –25V, the output of the LT1999

will undergo phase reversal (seeFigure7).

Figure7. A Plot of the LT1999’s Output Voltage vs VSENSE (VSENSE = V+IN – V–IN).

In Applications Where the Sense Voltage Is Driven in Excess of –25V, the

Output of the LT1999 Will Undergo Phase Reversal

VSENSE (V)

–60

VOUT (1V/DIV)

–30–45 –15 30

1999 F06

6015 450

VOUT PHASE REVERSAL FOR VSENSE < –25V

VREF = 2.5V

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

TYPICAL APPLICATIONS

Solenoid Current Monitor

The solenoid of Figure8 consists of a coil of wire in an

iron case with permeable plunger that acts as a mov-

able element. When the MOSFET turns on, the diode is

reversed biased off, and current flows through RSENSE to

actuate the solenoid. If the MOSFET is turned off, the cur-

rent in the MOSFET is interrupted, but the energy stored

in the solenoid causes the diode to turn on and current

to freewheel in the loop consisting of the diode, RSENSE

and the solenoid.

Figure8 shows the LT1999 monitoring currents in a

ground referenced solenoid used when the coil is hard

tied to the case, and is tied to ground. Figure9 shows a

supply referenced solenoid whose coil is insulated from

the case. The LT1999 will interface equally well to either

of these two configurations.

Bidirectional PWM Motor Monitor

Pulse width modulation is commonly used to efficiently

vary the average voltage applied across a DC motor. The

H-bridge topology of Figure10 allows full 4-quadrant

control: clockwise control, counter-clockwise control,

clockwise regeneration, and counter-clockwise regen-

eration. The LT1999 in conjunction with a non-inductive

current shunt is used to monitor currents in the rotor.

The LT1999 can be used to detect stuck rotors, provide

detection of overcurrent conditions in general, or provide

current mode feedback control.

Figure11 shows a plot of the output voltage of the LT1999.

Figure8. Solenoid Current Monitor for Ground Tied Solenoid. The Common Mode

Inputs to the LT1999 Switch Between VS and One Diode Drop Below Ground

LT1999

0.8k

160k

2µA

0.8k

SHDN

V+

–

V+

TIME (50ms/DIV)

VOUT (0.5V/DIV)

V+IN (10V/DIV)

1999 F07a

1999 F07b

0.1µF

SOLENOID

RSENSE

V+IN

VSHDN

VOUT

VREF

V–IN

OFF

VOUT

V+IN

SOLENOID PLUNGER PULLS IN

SOLENOID RELEASES

2.5V

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

Figure9. Solenoid Current Monitor for Non-Grounded Solenoids. This Circuit Performs the

Same Function as Figure7 Except One End of the Solenoid Is Tied to VS. The Common Mode

Voltage of Inputs of the LT1999 Switch Between Ground and One Diode Drop Above VS

TYPICAL APPLICATIONS

LT1999

0.8k

160k

2µA

0.8k

SHDN

V+

–

V+

1999 F08a

40.1µF

2.5V

0.1µF

SOLENOID

RSENSE

VOUT

VREF

VSHDN

OFF V+

V+

V+IN

V–IN

TIME (50ms/DIV)

VOUT (0.5V/DIV)

V+IN (10V/DIV)

VOUT

V+IN

SOLENOID PLUNGER PULLS IN

SOLENOID RELEASES

1999 F08b

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

TYPICAL APPLICATIONS

Figure10. Armature Current Monitor for DC Motor Applications

Figure11. LT1999 Output Waveforms for the Circuit of Figure10

1999 F09

VBRIDGE

V+IN

V–IN

RSENSE

0.025Ω

10µF

PWM INPUT

DIRECTION

BRAKE INPUT

24V

GND

PWM IN OUTA

OUTB

1000µF

24V MOTOR

H-BRIDGE

LT1999-20

0.8k

160k

2µA

0.8k

SHDN

–

80k

V+

V+0.1µF

0.1µF

VSHDN

VOUT

VREF

V+

TIME (20µs/DIV)

VOUT (2V/DIV)

V+IN (20V/DIV)

1999 F10

VOUT

V+IN

2.5V

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

PACKAGE DESCRIPTION

MSOP (MS8) 0213 REV G

0.53 ±0.152

(.021 ±.006)

SEATING

PLANE

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

0.18

(.007)

0.254

(.010)

1.10

(.043)

MAX

0.22 – 0.38

(.009 – .015)

TYP

0.1016 ±0.0508

(.004 ±.002)

0.86

(.034)

REF

0.65

(.0256)

BSC

0° – 6° TYP

DETAIL “A”

GAUGE PLANE

1 2 34

4.90 ±0.152

(.193 ±.006)

8765

3.00 ±0.102

(.118 ±.004)

(NOTE 3)

3.00 ±0.102

(.118 ±.004)

(NOTE 4)

0.52

(.0205)

REF

5.10

(.201)

MIN

3.20 – 3.45

(.126 – .136)

0.889 ±0.127

(.035 ±.005)

RECOMMENDED SOLDER PAD LAYOUT

0.42 ± 0.038

(.0165 ±.0015)

TYP

0.65

(.0256)

BSC

MS8 Package

8-Lead Plastic MSOP

(Reference LTC DWG # 05-08-1660 Rev G)

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

.016 – .050

(0.406 – 1.270)

.010 – .020

(0.254 – 0.508)× 45°

0°– 8° TYP

.008 – .010

(0.203 – 0.254)

SO8 REV G 0212

.053 – .069

(1.346 – 1.752)

.014 – .019

(0.355 – 0.483)

TYP

.004 – .010

(0.101 – 0.254)

.050

(1.270)

BSC

1234

.150 – .157

(3.810 – 3.988)

NOTE 3

8765

.189 – .197

(4.801 – 5.004)

NOTE 3

.228 – .244

(5.791 – 6.197)

.245

MIN .160 ±.005

RECOMMENDED SOLDER PAD LAYOUT

.045 ±.005

.050 BSC

.030 ±.005

TYP

INCHES

(MILLIMETERS)

NOTE:

1. DIMENSIONS IN

2. DRAWING NOT TO SCALE

3. THESE DIMENSIONS DO NOT INCLUDE MOLD FLASH OR PROTRUSIONS.

MOLD FLASH OR PROTRUSIONS SHALL NOT EXCEED .006" (0.15mm)

4. PIN 1 CAN BE BEVEL EDGE OR A DIMPLE

S8 Package

8-Lead Plastic Small Outline (Narrow .150 Inch)

(Reference LTC DWG # 05-08-1610 Rev G)

PACKAGE DESCRIPTION

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog

Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications

subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices.

REVISION HISTORY

REV DATE DESCRIPTION PAGE NUMBER

A 5/11 Revised +IN and –IN pin descriptions in Pin Functions section 12

B 3/12 Revised Voltage Output Swing Low specification (VOUT) under a loaded condition of 1kΩ to mid-supply.

Updated Figure4 to multicolor.

4, 6

C 2/15 Addition of MSOP Pinout Option Engineered for FMEA

Correction to AV Specification for LT1999-50 from 48.75 to 49.75

Update to Pin Functions to include Pinout Option Engineered for FMEA

Addition of New Application Information "Pinout Option Engineered for FMEA"

Addition of Figure5 and Renumbering of Figures 6 to 11

Addition of Table 1 and Table2

All

18, 19

18 to 23

D 6/15 LT1999F added to Figure1 (Simplified Block Diagram)

LT1999F added to Figure2 (Test Circuit)

Additional test condition (VCM = 80) added to table 1 and table 2

Note added regarding the use of FMEA information

E 9/19 Added Automotive Grade products, updated data sheet format All

LT1999-10/LT1999-20/

LT1999-50

Rev. E

For more information www.analog.com

 ANALOG DEVICES, INC. 2010-2019

09/19

www.analog.com

TYPICAL APPLICATION

PART NUMBER DESCRIPTION COMMENTS

LT1787/

LT1787HV

Precision, Bidirectional High Side Current Sense Amplifier 2.7V to 60V Operation, 75μV Offset, 60μA Current Draw

LT6100 Gain-Selectable High Side Current Sense Amplifier 4.1V to 48V Operation, Pin-Selectable Gain:

10V/V, 12.5V/V, 20V/V, 25V/V, 40V/V, 50V/V

LTC6101/

LTC6101HV

High Voltage High Side Current Sense Amplifier 4V to 60V/5V to 100V Operation, External Resistor Set Gain, SOT23

LTC6102/

LTC6102HV

Zero Drift High Side Current Sense Amplifier 4V to 60V/5V to 100V Operation, ±10μV Offset, 1μs Step Response,

MSOP8/DFN Packages

LTC6103 Dual High Side Precision Current Sense Amplifier 4V to 60V, Gain Configurable, 8-Pin MSOP Package

LTC6104 Bidirectional, High Side Current Sense 4V to 60V, Gain Configurable, 8-Pin MSOP Package

LT6106 Low Cost, High Side Precision Current Sense Amplifier 2.7V to 36V, Gain Configurable, SOT23 Package

LT6105 Precision, Extended Input Range Current Sense Amplifier –0.3 to 44V, Gain Configurable, 8-Pin MSOP Package

LTC4150 Coulomb Counter/Battery Gas Gauge Indicates Charge Quantity and Polarity

LT1990 Precision, 100μA Gain Selectable Amplifier 2.7V to 36V Operation, CMRR > 70dB, Input Voltage = ±250V

LT1991 ±250V Input Range Difference Amplifier 2.7V to 36V Operation, 50μV Offset, CMRR > 75B, Input Voltage = ±60V

LT1637/LT1638 1.1/1.2MHz, 0.4V/μs Over-The-Top, Rail-to-Rail Input and

Output Amplifier

0.4V/μs Slew Rate, 230μA per Amplifier

RELATED PARTS

1999 TA02

5V 0.1µF

LT1999-10

0.8k

160k

2µA

0.8k

V+

–

SHDN

–

VOUT

40k

VREF

VSHDN

V+

0.1µF

CHARGER

LOAD

0.025Ω

BAT

42V

VCC VREF

0.1µF

+IN

10µF

SCK

SDO

LTC2433-1VOUT

–

–IN

0.1µF

V+IN

V–IN

Battery Charge Current and Load Current Monitor

VOUT = 0.25V/A, Maximum Measured Current ±9.5A