Datasheet

ManualsBrandsLINEAR TECHNOLOGY ManualsLinear ICsLinear IC - Op-amp Current sensor SO 8

LT1999-10/LT1999-20/

LT1999-50

1999fb

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 magnitude

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 common mode input

range of –5V to 80V, the LT1999 is suitable 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 minimiz-

ing power consumption.

The LT1999 is available in an 8-lead MSOP or SOP package.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. All other trademarks are the property of their respective owners.

applicaTions

Buffered Output with 3 Gain Options:

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

Gain Accuracy: 0.5% Max

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

AC CMRR > 80dB at 100kHz

Input Offset Voltage: 1.5mV Max

–3dB Bandwidth: 2MHz

Smooth, Continuous Operation Over Entire Common

Mode Range

4kV HBM Tolerant and 1kV CDM Tolerant

Low Power Shutdown <10µA

–55°C to 150°C Operating Temperature Range

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

High Side or Low Side Current Sensing

H-Bridge Motor Control

Solenoid Current Sense

High Voltage Data Acquisition

PWM Control Loops

Fuse/MOSFET Monitoring

Full Bridge Armature Current Monitor

TIME (10µs/DIV)

2.5V

OUT

(2V/DIV)

+IN

(20V/DIV)

1999 TA01b

OUT

+IN

LT1999

0.8k

160k

2µA

0.8k

SHDN

1999 TA01a

–

0.1µF

OUT

+IN

–IN

REF

SHDN

Summary of content (24 pages)

PAGE 1
LT1999-10/LT1999-20/ LT1999-50 High Voltage, Bidirectional Current Sense Amplifier Features n n n n n n n n n n n Description Buffered Output with 3 Gain Options: 10V/V, 20V/V, 50V/V Gain Accuracy: 0.5% Max Input Common Mode Voltage Range: –5V to 80V AC CMRR > 80dB at 100kHz Input Offset Voltage: 1.
PAGE 2
LT1999-10/LT1999-20/ LT1999-50 Absolute Maximum Ratings (Note 1) 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...............................................
PAGE 3
LT1999-10/LT1999-20/ LT1999-50 Order Information LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION SPECIFIED TEMPERATURE RANGE 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 LTF
PAGE 4
LT1999-10/LT1999-20/ LT1999-50 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.
PAGE 5
LT1999-10/LT1999-20/ LT1999-50 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.
PAGE 6
LT1999-10/LT1999-20/ LT1999-50 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.
PAGE 7
LT1999-10/LT1999-20/ LT1999-50 Typical Performance Characteristics Supply Current vs Input Common Mode 7 Supply Current vs Temperature 1.8 V+ = 5V 6 VSHDN = OPEN VINDIFF = 0V VCM = 12V 150°C 130°C 90°C 25°C –45°C –55°C 3.5 1.7 5 3.0 3 2 IS (mA) 2.5 4 IS (mA) IS (mA) Supply Current vs Supply Voltage 4.0 1.6 V+ = 5.5V 1.5 VCM = 12V 2.0 1.5 V+ = 4.5V 1.0 1 0.5 0 –5 5 15 25 35 45 VCM (V) 55 65 1.
PAGE 8
LT1999-10/LT1999-20/ LT1999-50 Typical Performance Characteristics Input Referred Voltage Offset vs Temperature and Gain Option 1500 Input Referred Voltage Offset vs Input Common Mode Voltage 1500 VCM = 12V 12 UNITS PLOTTED 1000 1000 500 VOSI (µV) 500 VOSI (µV) V+ = 5V TA = 25°C 12 UNITS PLOTTED 0 0 –500 –500 –1000 –1500 –55 –30 –5 LT1999-10 LT1999-20 LT1999-50 –1000 LT1999-10 LT1999-20 LT1999-50 20 45 70 95 TEMPERATURE (°C) –1500 120 145 –5 5 15 25 1999 G10 25 GAIN GAIN (dB) 135 30
PAGE 9
LT1999-10/LT1999-20/ LT1999-50 Typical Performance Characteristics VSENSE VSENSE VSENSE 4.5 VOUT 0.100 4.5 0.075 4.0 2.5 0 2.0 1.5 –0.025 OUTPUT ERROR 1.0 0.5 1999 G20 TIME (1µs/DIV) VOUT (V) 0.025 0.15 VOUT 0.10 3.0 0.05 2.5 0 –0.05 2.0 –0.050 1.5 –0.075 1.0 –0.100 0.5 OUTPUT ERROR OUTPUT ERROR (V) 3.0 0.20 3.5 0.050 OUTPUT ERROR (V) VOUT (V) 3.5 1999 G19 TIME (2µs/DIV) LT1999-20 2V Step Response Settling Time LT1999-10 2V Step Response Settling Time 4.
PAGE 10
LT1999-10/LT1999-20/ LT1999-50 Typical Performance Characteristics LT1999-10 Common Mode Rising Edge Step Response LT1999-10 Common Mode Falling Edge Step Response VCM , tRISE ≈ 20ns VOUT (0.5V/DIV) VOUT TIME (0.5µs/DIV) VCM (25V/DIV) VCM (25V/DIV) VOUT (0.5V/DIV) VCM , tFALL ≈ 20ns VOUT 1999 G25 1999 G26 TIME (0.5µs/DIV) LT1999-20 Common Mode Rising Edge Step Response LT1999-20 Common Mode Falling Edge Step Response VOUT (0.5V/DIV) VOUT TIME (0.
PAGE 11
LT1999-10/LT1999-20/ LT1999-50 Typical Performance Characteristics LT1999 Input Referred Noise Density vs Frequency Short-Circuit Current vs Temperature 1000 3.0 40 30 SINKING REF PIN VOLTAGE (V) ISC (mA) 100 10 0 –10 –20 SOURCING 0.1 1 10 FREQUENCY (kHz) 1000 10000 –5 20 45 70 95 TEMPERATURE (°C) 1999 G31 0 1.5 1.
PAGE 12
LT1999-10/LT1999-20/ LT1999-50 Pin Functions V+ (Pins 1, 4): Power Supply Voltage. Pins 1 and 4 are tied internally together. The specified range of operation 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. OUT (Pin 7): Voltage Output. VOUT = AV •(VSENSE ± VOSI), where AV is the gain, and VOSI is the input referred offset voltage.
PAGE 13
LT1999-10/LT1999-20/ LT1999-50 Block Diagram V+ 2µA V+ 4.5k V(G+IN) R +IN 2 2k 2k +IN CF 4pF 3 8 SHDN 1 2k –IN 2k + GIN – V(G–IN) 0.8k R +S RG – + AO V+ D1 OUT 7 V+ 0.8k R –S 300Ω 160k REF 6 160k R –IN V+ GND 4 5 1999 BD Figure 1. Simplified Block Diagram Test Circuit V+ LT1999 V+ 5V 2µA 1 VCM + – + – V + + – 4k 2 + – 8 V SHDN SHDN + 0.8k RG – + V+ VIN(DIFF) – 4k 3 0.8k 160k 6 V+ 5V 7 V OUT 160k 4 VREF 0.1µF 5 0.1µF 1999 F02 Figure 2.
PAGE 14
LT1999-10/LT1999-20/ LT1999-50 Applications Information 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.
PAGE 15
LT1999-10/LT1999-20/ LT1999-50 Applications Information Input Common Mode Range –2.0 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.
PAGE 16
LT1999-10/LT1999-20/ LT1999-50 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.
PAGE 17
LT1999-10/LT1999-20/ LT1999-50 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.
PAGE 18
LT1999-10/LT1999-20/ LT1999-50 Applications Information 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 5). If the fuse in Figure 5 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.
PAGE 19
LT1999-10/LT1999-20/ LT1999-50 Typical Applications Solenoid Current Monitor Bidirectional PWM Motor Monitor The solenoid of Figure 7 consists of a coil of wire in an iron case with permeable plunger that acts as a movable element. When the MOSFET turns on, the diode is reversed biased off, and current flows through RSENSE to actuate the solenoid.
PAGE 20
LT1999-10/LT1999-20/ LT1999-50 Typical Applications V+ LT1999 VS 1 2µA V+ SOLENOID V+IN + – 4k 2 + V 0.8k – + 7 VOUT 3 5V 4 4k V+ 0.8k 160k 6 VREF 160k 0.1µF 2.5V VOUT V+IN (10V/DIV) V–IN ON VSHDN RG V+ RSENSE OFF 8 SHDN VOUT (0.5V/DIV) 5V SOLENOID RELEASES SOLENOID PLUNGER PULLS IN V+IN 5 0.1µF 1999 F08a TIME (50ms/DIV) 1999 F08b Figure 8. Solenoid Current Monitor for Non-Grounded Solenoids.
PAGE 21
LT1999-10/LT1999-20/ LT1999-50 Typical Applications 5V V+ 10µF V+ LT1999-20 1 2µA SHDN + – 24V 4k 2 V+IN C4 1000µF 0.8k 80k V–IN 3 0.1µF – + 7 4k 0.8k 160k 6 160k 5V V+ 5V OUTA DIRECTION VOUT VREF 0.1µF 5 4 PWM INPUT VSHDN V+ VBRIDGE H-BRIDGE RSENSE 0.025Ω 1999 F09 24V MOTOR OUTB BRAKE INPUT GND Figure 9. Armature Current Monitor for DC Motor Applications VOUT 2.5V V+IN (20V/DIV) VOUT (2V/DIV) PWM IN V+ 8 V+IN TIME (20µs/DIV) 1999 F10 Figure 10.
PAGE 22
LT1999-10/LT1999-20/ LT1999-50 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. MS8 Package 8-Lead Plastic MSOP (Reference LTC DWG # 05-08-1660 Rev F) 3.00 ± 0.102 (.118 ± .004) (NOTE 3) 0.889 ± 0.127 (.035 ± .005) 0.254 (.010) 8 7 6 5 3.00 ± 0.102 (.118 ± .004) (NOTE 4) 4.90 ± 0.152 (.193 ± .006) DETAIL “A” 0.52 (.0205) REF 0° – 6° TYP GAUGE PLANE 5.23 (.206) MIN 3.20 – 3.45 (.126 – .136) 1 0.53 ± 0.152 (.021 ± .
PAGE 23
LT1999-10/LT1999-20/ LT1999-50 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. 4, 6 Updated Figure 4 to multicolor. 16 1999fb Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use.
PAGE 24
LT1999-10/LT1999-20/ LT1999-50 Typical Application Battery Charge Current and Load Current Monitor VOUT = 0.25V/A, Maximum Measured Current ±9.5A 0.025Ω CHARGER BAT 42V V+ 5V 2µA 1 V+IN SHDN + – 4k 2 + V 0.8k 8 VSHDN 7 VOUT 4k 3 0.8k V+ 5V 0.1µF 0.1µF 10µF 40k – + V+ V–IN 5V V+ LT1999-10 LOAD 160k + +IN VOUT 6 160k VREF – VCC VREF LTC2433-1 –IN CS SCK SDO 0.1µF 5 4 0.