Sample & Buy Product Folder Support & Community Tools & Software Technical Documents LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 LMP8350 Ultra-Low Distortion Fully-Differential Precision ADC Driver With Selectable Power Modes 1 Features 3 Description • • • • • • • • • • • • • • • • The LMP8350 device is an ultra low distortion fullydifferential amplifier designed for driving highperformance precision analog-to-digital converters (ADC). As part of the PowerWise™ family, a unique mode enable pin allows the user to choose from three different operating modes, trading power consumption for dynamic performance. 1 Differential Input and Output Tri-Level Power Settings with Shutdown Ultra Low HD2/HD3 and THD+N Distortion Adjustable Output Common-Mode Level Fully-Balanced Differential Architecture Single- or Dual-Supply Operation Operating Voltage Range 4.5 V to 12 V Supply Current 3 mA to 13 mA Total THD+N at 1 KHz 0.000097% HD2 / HD3 Distortion at 1 KHz < –124 dBc Bandwidth 118 mHz Settling to 0.1% 20 ns Low Offset Drift 0.4 µV/°C Offset Voltage 80 µV Voltage Noise 4.6 nV/Hz Operating Temperature Range −40°C to +85°C The high power mode is optimized for highest AC performance. The low noise, wide bandwidth, and fast slew rate make the LMP8350 ideal for driving 24bit ADCs with input sampling rates of 10 MHz or less. The medium power mode is optimized for precision DC performance, and can be used to drive 24-bit ADCs with input sampling rates of 6 MHz or less. The low power mode is a trade-off between AC performance and quiescent current for powersensitive applications. The disable mode fully shuts down the amplifier for further standby power savings. The fully differential architecture of this device allows for easy implementation of a single-ended to fullydifferential output conversion. Driving a 3-Vpp, 1-kHz output sine wave with the amplifier powered by ±3.3V rails in high power mode yields 0.000098% THD+N. 2 Applications • • • High-Resolution Differential ADC Drivers Portable Instrumentation Precision Line Drivers The LMP8350 is part of the LMP™ precision amplifier family, and is offered in the 8-pin SOIC package, with an operating temperature range of −40°C to +85°C. Device Information(1) PART NUMBER LMP8350 PACKAGE SOIC (8) BODY SIZE (NOM) 3.91 mm × 4.90 mm (1) For all available packages, see the orderable addendum at the end of the data sheet. Typical Application +VREF +V +V VREFP VA VIO +V RF1 RO1 RG1 VINN CS - + VOCM + VINP CS LMP8350 SCLK 24 Bit A/D RO2 VINP + RG2 - VINN SDI SDO MicroController VREFN AGND DGND RF2 1 An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications, intellectual property matters and other important disclaimers. PRODUCTION DATA. LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com Table of Contents 1 2 3 4 5 6 Features .................................................................. Applications ........................................................... Description ............................................................. Revision History..................................................... Pin Configuration and Functions ......................... Specifications......................................................... 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 7 1 1 1 2 3 3 Absolute Maximum Ratings ...................................... 3 ESD Ratings.............................................................. 4 Recommended Operating Conditions....................... 4 Thermal Information .................................................. 4 10-V Electrical Characteristics .................................. 5 6.6-V Electrical Characteristics ................................. 8 5-V Electrical Characteristics .................................. 11 Typical Characteristics ............................................ 14 Detailed Description ............................................ 19 7.1 Overview ................................................................. 19 7.2 Functional Block Diagram ....................................... 19 7.3 Feature Description................................................. 19 7.4 Device Functional Modes........................................ 20 8 Application and Implementation ........................ 22 8.1 Application Information............................................ 22 8.2 Typical Application ................................................. 25 9 Power Supply Recommendations...................... 27 9.1 Power Supply and VOCM Bypassing ....................... 27 10 Layout................................................................... 28 10.1 10.2 10.3 10.4 Layout Guidelines ................................................. Layout Example .................................................... Power Dissipation ................................................. Evaluation Board................................................... 28 28 29 29 11 Device and Documentation Support ................. 30 11.1 11.2 11.3 11.4 11.5 Documentation Support ....................................... Community Resources.......................................... Trademarks ........................................................... Electrostatic Discharge Caution ............................ Glossary ................................................................ 30 30 30 30 30 12 Mechanical, Packaging, and Orderable Information ........................................................... 30 4 Revision History NOTE: Page numbers for previous revisions may differ from page numbers in the current version. Changes from Revision B (March 2013) to Revision C • Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section. ................................................................................................ 1 Changes from Revision A (March 2013) to Revision B • 2 Page Page Changed layout of National Data Sheet to TI format ........................................................................................................... 29 Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 5 Pin Configuration and Functions D Package 8-Pin SOIC Top View 1 -IN 8 - 2 VOCM V+ +OUT + +IN 7 3 6 4 5 EN V- -OUT Pin Functions PIN NO. NAME I/O DESCRIPTION 1 –IN I Inverting Input 2 VOCM I Output common-mode voltage set input. Sets output common mode voltage equal to the applied VOCM pin voltage. 3 V+ I Positive power supply voltage 4 +OUT O Noninverting output 5 –OUT O Inverting output 6 V– I Negative power supply voltage 7 EN I Enable and power select input. Applied voltage sets power level or shutdown mode. 8 +IN I Noninverting Input 6 Specifications 6.1 Absolute Maximum Ratings (1) (2) (3) MIN MAX UNIT –0.3 12.9 V (V+) + 0.3 (V–) – 0.3 V 1 mA 150 °C 150 °C Output short circuit duration See V+ relative to V– IN+, IN–, OUT, EN and VOCM pins Input current Junction temperature (5) −65 Storage temperature, Tstg (1) (2) (3) (4) (5) (4) Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device reliability. If Military/Aerospace specified devices are required, please contact the TI Sales Office/ Distributors for availability and specifications. For soldering specifications: SNOA549 The short circuit test is a momentary test which applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can exceed the maximum allowable junction temperature of 150°C. Positive number (+) is sourcing, negative number (–) is sinking. The maximum power dissipation is a function of TJ(MAX), θJA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) – TA)/ θJA. All numbers apply for packages soldered directly onto a PC Board. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 3 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com 6.2 ESD Ratings VALUE V(ESD) (1) (2) (3) Electrostatic discharge Human body model (HBM), per ANSI/ESDA/JEDEC JS-001 (1) (2) ±2500 Charged-device model (CDM), per JEDEC specification JESD22-C101 (3) ±1250 Machine Model ±200 UNIT V JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process. Manufacturing with less than 500-V HBM is possible with the necessary precautions. Human Body Model, applicable std. MIL-STD-883, Method 3015.7. Machine Model, applicable std. JESD22-A115-A (ESD MM std. of JEDEC). Field-Induced Charge-Device Model, applicable std. JESD22-C101-C (ESD FICDM std. of JEDEC). JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process. 6.3 Recommended Operating Conditions (1) See MIN MAX Temperature range (TA) –40 85 °C Supply voltage (VS = V+ – V–) 4.5 12 V (1) UNIT Absolute Maximum Ratings indicate limits beyond which damage to the device may occur. Operating Ratings indicate conditions for which the device is intended to be functional, but specific performance is not ensured. For ensured specifications and the test conditions, see the Electrical Characteristics Tables. 6.4 Thermal Information LMP8350 THERMAL METRIC (1) D (SOIC) UNIT 8 PINS RθJA (1) (2) 4 Junction-to-ambient thermal resistance (2) 150 °C/W For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application report, SPRA953. The maximum power dissipation is a function of TJ(MAX), θJA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX) – TA)/ θJA. All numbers apply for packages soldered directly onto a PC Board. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 6.5 10-V Electrical Characteristics Unless otherwise specified, all limits are ensured for TA = 25°C, Avcl = +1, RF = RG = 1 kΩ, Fully differential input, VS = +10 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted. (1) TEST CONDITIONS (2) PARAMETER MIN (3) TYP (4) MAX (3) UNIT 10-V DC CHARACTERISTICS TA = 25°C High power Input offset voltage (RTI) VOS ±0.6 At the temperature extremes TA = 25°C Mid power ±0.08 At the temperature extremes ±0.1 At the temperature extremes ±0.5 Low power ±0.4 Input bias current TA = 25°C Mid power Low power AVOL Open-loop gain CMVR CMRR Common-mode voltage range (6) Common-mode rejection ratio 2 2.1 TA = 25°C 2.7 At the temperature extremes 3.2 TA = 25°C 3.5 At the temperature extremes 65 90 Mid power 72 130 Low power 74 114 HP at CMRR ≥ 73 dB 1.2 8.8 MP at CMRR ≥ 83 dB 1.2 8.8 LP at CMRR ≥ 77 dB 1.2 8.8 DC, VOCM = 0,VID = 0, ΔVcm = ±0.2 V, High power 75 90 Medium power 84 130 Low power 79 114 Differential input resistance VCM = mid-supply 0.48 Differential input capacitance VCM = mid-supply 1 High power Mid power Low power (1) (2) (3) (4) (5) (6) μA 3.7 High power CIND Output swing (single-ended) μV/°C At the temperature extremes ZIND VO ±2.5 ±0.8 Input offset voltage vs.temperature (5) Mid power High power IB mV ±2.52 High power TCVOS ±2 ±2.03 TA = 25°C Low power ±4 ±4.05 dB V dB MΩ pF Low Swing 0.86 0.75 9.14 High Swing 0.86 9.25 9.14 Low Swing 0.85 0.74 9.15 High Swing 0.85 9.26 9.15 Low Swing 0.86 0.81 9.14 High Swing 0.86 9.19 9.14 V Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of the device such that TJ = TA. No ensured specification of parametric performance is indicated in the electrical tables under conditions of internal self-heating where TJ > TA For annotation brevity, “HP”=High Power, “MP”=Medium Power, “LP” =Low Power, “DIS”=Disabled or shut down, “SE”=Single Ended Mode, “DM”=Differential Mode. See Table 1 in Applications section for power setting details. It is also assumed RG = RG1 = RG2 Limits are 100% production tested at 25°C. Limits over the operating temperature range are ensured through correlations using the Statistical Quality Control (SQC) method. Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will also depend on the application and configuration. The typical values are not tested and are not ensured on shipped production material. Drift Determined by dividing the change in parameter at temperature extremes by the total temperature change. Value is the worst case of TaMIN to 25°C and 25°C to TaMAX. At amplifier inputs. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 5 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com 10-V Electrical Characteristics (continued) Unless otherwise specified, all limits are ensured for TA = 25°C, Avcl = +1, RF = RG = 1 kΩ, Fully differential input, VS = +10 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted.(1) TEST CONDITIONS (2) PARAMETER Output shorted to midsupply (7) High power ISHORT Short-circuit current Medium power Low power PSRR Power supply rejection ratio VS ±10% Supply current TYP (4) Low Swing –36 -65 High Swing 75 108 Low Swing -26 -48 High Swing 60 85 Low Swing -6 -20 High Swing 15 107 Mid power 118 Low power 124 TA = 25°C 15 At the temperature extremes TA = 25°C VEN = 6.25 (8) TA = 25°C PD Power-down mode At the temperature extremes Shutdown current Enable time dB 18 10 TA = 25°C mA 4 5 < 1.65 0.75 At the temperature extremes Enable pin current ten mA 11 3 Disable voltage threshold (8) UNIT 20 8 At the temperature extremes VEN = 3.75 (8) MAX (3) 36 High power VEN = 8.75 (8) IS MIN (3) V 0.9 0.95 100 High power 15 Mid power 20 Low power 40 High power 118 Mid power 87 Low power 31 High power 507 Mid power 393 Low power 178 mA μA ns 10-V AC CHARACTERISTICS SSBW SR Small signal bandwidth 200 mVp-p differential Slew rate 2 Vp-p differential (9) High power trise tfall ts en (7) (8) (9) 6 Rise time 2 Vp-p differential Fall time 2 Vp-p differential 0.1% settling time 2 Vp-p Input referred voltage noise at 10 KHz MHz V/μs 3 Mid power 3.9 Low power 9.7 High power 2.8 Mid power 3.8 Low power 9.6 2-V step, CL = 20 pF High power 20 Mid power 25 Low power 38 High power 4.6 Mid power 4.8 Low power 8 ns ns ns nV/√Hz The short circuit test is a momentary test which applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can exceed the maximum allowable junction temperature of 150°C. Positive number (+) is sourcing, negative number (–) is sinking. Enable voltage is referred to V– (negative supply voltage). Slew Rate is the average of the rising and falling edges. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 10-V Electrical Characteristics (continued) Unless otherwise specified, all limits are ensured for TA = 25°C, Avcl = +1, RF = RG = 1 kΩ, Fully differential input, VS = +10 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted.(1) TEST CONDITIONS (2) PARAMETER In THD+N Input referred current noise at 10 KHz Total harmonic distortion + noise 3 Vp-p at 1 KHz 2nd harmonic distortion 3 Vp-p, 1 KHz HD2 2nd harmonic distortion 6 Vp-p, 1 KHz 3rd harmonic distortion 3 Vp-p, 1 KHz HD3 3rd harmonic distortion 6 Vp-p, 1 KHz MIN (3) TYP (4) f = 10 kHz High power 1.7 Mid power 1.1 Low power 0.6 High power 0.000097% Mid power 0.000109% Low power 0.000185% High power –124.7 Mid power –122.8 Low power –117.2 High power –118.9 Mid power –117.6 Low power –114.7 High power –139.9 Mid power –141.9 Low power –133.3 High power –129.5 Mid power –132.4 Low power –129.4 High power 4.8 MAX (3) UNIT pA/√Hz –116 dBc dBc –126 dBc dBc 10-V VOCM INPUT CHARACTERISTICS VOCM small signal bandwidth 200 mVp-p Mid power 2.4 Low power 0.64 High power ±1.62 Mid power ±0.23 Low power ±0.43 VOCM gain VOCM offset voltage 1 VOCM voltage range All power levels VOCM input resistance All power levels Low Swing 1.8 High Swing 8.2 Low Swing 30 High Swing mid-supply Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 MHz V/V mV V KΩ 7 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com 6.6 6.6-V Electrical Characteristics Unless otherwise specified, all limits are ensured for TA = 25°C, Avcl = +1, RF = RG = 1 kΩ, Fully differential input, VS = +6.6 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted. (1) TEST CONDITIONS (2) PARAMETER MIN (3) TYP (4) MAX (3) UNIT 6.6-V DC CHARACTERISTICS TA = 25°C High power Input offset voltage (RTI) VOS S Input offset voltage vs.temperature (5) IB Input bias current ±0.1 At the temperature extremes ±0.1 At the temperature extremes ±0.7 Mid power ±0.5 Low power ±0.4 Low power ±2.5 μV/°C TA = 25°C 1.4 At the temperature extremes 2.4 TA = 25°C 2.5 At the temperature extremes 3.0 TA = 25°C 3.5 At the temperature extremes 65 70 Mid power 73 76 Low power 72 75 HP at CMRR ≥ 68 dB 1.2 5.4 CMVR Common-mode voltage range (6) MP at CMRR ≥ 63 dB 1.2 5.4 LP at CMRR ≥ 79 dB 1.2 5.4 DC, VOCM = 0,VID = 0, ΔVcm = ±0.2 V High power 70 85 Mid power 86 117 Low power 81 Open-loop gain CMRR Common-mode rejection ratio ZIND Differential input resistance VCM = mid-supply CIND Differential input capacitance VCM = mid-supply High power VO Output swing (single-ended) Mid power Low power (1) (2) (3) (4) (5) (6) 8 μA 3.7 High power AVOL mV ±2.52 High power Mid power ±2.8 ±2.83 TA = 25°C High power ±3.5 ±3.54 TA = 25°C Mid power Low power TCVO ±0.3 At the temperature extremes dB V dB 113 0.48 MΩ 1 pF Low Swing 0.84 0.77 5.76 High Swing 0.84 5.83 5.76 Low Swing 0.82 0.75 5.78 High Swing 0.82 5.83 5.78 Low Swing 0.83 0.77 5.77 High Swing 0.83 5.83 5.77 V Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of the device such that TJ = TA. No ensured specification of parametric performance is indicated in the electrical tables under conditions of internal self-heating where TJ > TA For annotation brevity, “HP”=High Power, “MP”=Medium Power, “LP” =Low Power, “DIS”=Disabled or shut down, “SE”=Single Ended Mode, “DM”=Differential Mode. See Table 1 in Applications section for power setting details. It is also assumed RG = RG1 = RG2 Limits are 100% production tested at 25°C. Limits over the operating temperature range are ensured through correlations using the Statistical Quality Control (SQC) method. Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will also depend on the application and configuration. The typical values are not tested and are not ensured on shipped production material. Drift Determined by dividing the change in parameter at temperature extremes by the total temperature change. Value is the worst case of TaMIN to 25°C and 25°C to TaMAX. At amplifier inputs. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 6.6-V Electrical Characteristics (continued) Unless otherwise specified, all limits are ensured for TA = 25°C, Avcl = +1, RF = RG = 1 kΩ, Fully differential input, VS = +6.6 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted.(1) TEST CONDITIONS (2) PARAMETER Output shorted to mid-supply (7) High power ISHORT Short-circuit current Mid power Low power PSRR Power supply rejection ratio VS ±10% Supply current TYP (4) Low Swing –30 –49 High Swing 54 83 Low Swing –19 –35 High Swing 40 64 Low Swing –6 –15 High Swing 15 111 Mid power 117 Low power 127 VEN = 4.125 (8) VEN = 2.475 (8) TA = 25°C TA = 25°C ten Power-down mode Enable time Shutdown current mA dB 16 9 10 2 At the temperature extremes TA = 25°C UNIT 18 7 At the temperature extremes Disable voltage threshold (8) PD 14 At the temperature extremes TA = 25°C MAX (3) 27 High power VEN = 5.775 (8) IS MIN (3) mA 3 4 <1.225 0.55 At the temperature extremes V 0.65 0.7 Enable pin current 40 High power 18 Mid power 22 Low power 43 High power 116 Mid power 85 Low power 29 High power 488 Mid power 376 Low power 166 High power 3.1 mA μA ns 6.6-V AC CHARACTERISTICS Small signal bandwidth SSBW 200 mVp-p differential SR trise tfall ts (7) (8) (9) Slew rate 2 Vp-p differential (9) Rise time 2 Vp-p differential Fall time 2 Vp-p differential 0.1% settling time 2 Vp-p Mid power 4.2 Low power 10.4 High power 3.0 Mid power 4.0 Low power 10.3 2-V step, CL = 20 pF High power 19 Mid power 25 Low power 43 MHz V/μs ns ns ns The short circuit test is a momentary test which applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can exceed the maximum allowable junction temperature of 150°C. Positive number (+) is sourcing, negative number (–) is sinking. Enable voltage is referred to V- (negative supply voltage). Slew Rate is the average of the rising and falling edges. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 9 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com 6.6-V Electrical Characteristics (continued) Unless otherwise specified, all limits are ensured for TA = 25°C, Avcl = +1, RF = RG = 1 kΩ, Fully differential input, VS = +6.6 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted.(1) TEST CONDITIONS (2) PARAMETER en In THD+ N Input referred voltage noise at 10KHz Input referred current noise at 10KHz Total harmonic distortion + noise 3 Vp-p at 1 KHz 2nd harmonic distortion 3 Vp-p, 1 KHz HD2 2nd harmonic distortion 6 Vp-p, 1 KHz 3rd harmonic distortion 3 Vp-p, 1 KHz HD3 3rd harmonic distortion 6Vp-p, 1KHz MIN (3) TYP (4) High power 4.5 Mid power 4.8 Low power 8 High power 1.7 Mid power 1.2 Low power 0.6 High power 0.000098 % Mid power 0.00011% Low power 0.000089 % High power –124.7 Mid power –122.8 Low power –117.2 High power –118.9 Mid power –117.6 Low power –114.7 High power –139.9 Mid power -141.9 Low power –133.3 High power –121.4 Mid power –125.3 Low power –124.5 High power 4.5 Mid power 2.2 Low power 0.6 MAX (3) UNIT nV/√Hz pA/√Hz dBc dBc dBc dBc 6.6-V VOCM INPUT CHARACTERISTICS VOCM small signal bandwidth 200mVp-p VOCM gain VOCM offset voltage 10 1 High power ±0.97 Mid power ±0.43 Low power ±0.89 VOCM voltage range All power levels VOCM input resistance All power levels Low Swing 1.2 High Swing 5.4 Low Swing 30 High Swing mid-supply Submit Documentation Feedback MHz V/V mV V KΩ Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 6.7 5-V Electrical Characteristics Unless otherwise specified, all limits are ensured for TA = 25°C, Avcl = +1, RF= RG = 1 kΩ, Fully differential input, VS = +5 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted. (1) PARAMETER TEST CONDITIONS MIN (2) TYP (3) MAX (2) ±0.2 ±3.2 UNIT 5-V DC CHARACTERISTICS High power Input offset voltage (RTI) VOS S Input offset voltage vs.temperature (4) Mid power Input bias current Open-loop gain CMRR Common-mode rejection ratio ±0.7 Mid power ±0.5 Low power ±0.4 At the temperature extremes 1.6 TA = 25°C 2.5 At the temperature extremes 3.0 TA = 25°C 3.5 68 Mid power 71 75 68 75 1.15 3.85 MP at CMRR ≥ 86 dB 1.15 3.85 LP at CMRR ≥ 80 dB 1.15 3.85 DC, VOCM = 0,VID = 0, ΔVcm = ±0.2 V High power 63 79 Mid power 87 114 Low power 82 Differential input capacitance VCM = mid-supply High power Mid power Low power (1) (2) (3) (4) (5) dB HP at CMRR ≥ 60 dB CIND μA 3.7 63 VCM = mid-supply Output swing (single-ended) μV/°C 1.5 At the temperature extremes Differential input resistance VO ±2.0 TA = 25°C High power ZIND mV ±2.3 High power Low power CMVR Common-mode voltage range (5) ±0.1 At the temperature extremes Mid power ±2.0 ±2.3 TA = 25°C Low power AVOL ±3.6 ±0.1 At the temperature extremes High power IB At the temperature extremes TA = 25°C Low power TCVO TA = 25°C V dB 114 0.48 MΩ 1 pF Low Swing 0.82 0.77 4.18 High Swing 0.82 4.23 4.18 Low Swing 0.82 0.75 4.18 High Swing 0.82 4.25 4.18 Low Swing 0.83 0.77 4.17 High Swing 0.83 4.23 4.17 V Electrical Table values apply only for factory testing conditions at the temperature indicated. Factory testing conditions result in very limited self-heating of the device such that TJ = TA. No ensured specification of parametric performance is indicated in the electrical tables under conditions of internal self-heating where TJ > TA Limits are 100% production tested at 25°C. Limits over the operating temperature range are ensured through correlations using the Statistical Quality Control (SQC) method. Typical values represent the most likely parametric norm as determined at the time of characterization. Actual typical values may vary over time and will also depend on the application and configuration. The typical values are not tested and are not ensured on shipped production material. Drift Determined by dividing the change in parameter at temperature extremes by the total temperature change. Value is the worst case of TaMIN to 25°C and 25°C to TaMAX. At amplifier inputs. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 11 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com 5-V Electrical Characteristics (continued) Unless otherwise specified, all limits are ensured for TA = 25°C, Avcl = +1, RF= RG = 1 kΩ, Fully differential input, VS = +5 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted.(1) PARAMETER Output shorted to mid-supply (6) High power ISHORT Short-circuit current Mid power Low power PSRR Power supply rejection ratio VS ±10% Supply current TYP (3) Low Swing –25 –42 High Swing 44 72 Low Swing –16 –31 High Swing 34 57 Low Swing –5 –13 High Swing 12 117 Mid power 120 Low power 111 VEN = 3.125 (7) VEN = 1.875 (7) TA = 25°C 13 At the temperature extremes TA = 25°C At the temperature extremes PD ten Power-down mode Enable time Shutdown current mA dB 15 9 10 2 At the temperature extremes Disable voltage threshold (7) mA 3 4 <1.025 TA = 25°C UNIT 17 7 TA = 25°C MAX (2) 23 High power VEN = 4.375 (7) IS MIN (2) TEST CONDITIONS 0.50 At the temperature extremes V 0.85 0.90 Enable pin current 15 High power 20 Mid power 22 Low power 50 High power 114.5 mA μA ns 5-V AC CHARACTERISTICS Small signal bandwidth SSBW 200 mVp-p differential SR trIse tfall ts (6) (7) (8) 12 Slew rate 2 Vp-p differential (8) Rise time 2 Vp-p differential Fall time 2 Vp-p differential 0.1% settling time 2 Vp-p Mid power 84 Low power 28 High power 476 Mid power 366 Low power 160 High power 3.2 Mid power 4.3 Low power 10.8 High power 3.1 Mid power 4.1 Low power 10.7 2-V step, CL = 20 pF High power 19 Mid power 24 Low power 48 MHz V/μs ns ns ns The short circuit test is a momentary test which applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can exceed the maximum allowable junction temperature of 150°C. Positive number (+) is sourcing, negative number (–) is sinking. Enable voltage is referred to V- (negative supply voltage). Slew Rate is the average of the rising and falling edges. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 5-V Electrical Characteristics (continued) Unless otherwise specified, all limits are ensured for TA = 25°C, Avcl = +1, RF= RG = 1 kΩ, Fully differential input, VS = +5 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted.(1) PARAMETER en In THD+ N HD2 HD3 Input referred voltage noise Input referred current noise Total harmonic distortion + noise 3 Vp-p at 1 KHz 2nd harmonic distortion 3 Vp-p, 1 KHz 3rd harmonic distortion 3 Vp-p, 1 KHz TEST CONDITIONS MIN (2) TYP (3) f = 10 kHz High power 4.5 Mid power 4.8 Low power 8 f = 10 kHz High power 1.8 Mid power 1.2 Low power 0.6 High power 0.000107 % Mid power 0.000114 % Low power 0.000192 % High power –125.3 Mid power –122.6 Low power –117.0 High power –125.5 Mid power –130.0 Low power –128.7 High power 4.4 MAX (2) UNIT nV/√Hz pA/√Hz dBc dBc 5-V VOCM INPUT CHARACTERISTICS VOCM small signal bandwidth 200 mVp-p Mid power 2.2 Low power 0.56 VOCM gain VOCM offset voltage 1 High power ±0.46 Mid power ±0.53 Low power ±0.11 VOCM voltage range All power levels VOCM input resistance All power levels Low Swing 1.15 High Swing 3.85 Low Swing 30 High Swing midsupply Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 MHz V/V mV V KΩ 13 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com 6.8 Typical Characteristics 3 3 0 0 HP VOCMGAIN (dB) DIFFERENTIAL GAIN (dB) Unless otherwise specified, TA = 25°C, Avcl = +1, RF=RG = 1 kΩ, fully differential input, VS = +10 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted. -3 -6 HP -9 Avcl = +1 Vout = 200mVp-p Differential -12 -15 1M MP ûVocm = 200mVp-p LP LP -15 1G 10k 100k 1M 10M FREQUENCY (Hz) 100M Figure 2. VOCM Frequency Response at 10 V 3 3 0 0 HP VOCMGAIN (dB) DIFFERENTIAL GAIN (dB) -9 -12 10M 100M FREQUENCY (Hz) -3 -6 HP -9 -3 -6 -9 MP -12 Avcl = +1 Vout = 200mVp-p Differential -15 1M MP -12 ûVocm = 200mVp-p LP LP -15 10M 100M FREQUENCY (Hz) 1G Figure 3. Frequency Response at 6.6 V 10k 100k 1M 10M FREQUENCY (Hz) 100M Figure 4. VOCM Frequency Response at 6.6 V 3 3 0 0 HP VOCMGAIN (dB) DIFFERENTIAL GAIN (dB) -6 MP Figure 1. Frequency Response at 10 V -3 -6 HP -9 -12 Avcl = +1 Vout = 200mVp-p Differential -15 1M -3 -6 -12 ûVocm = 200mVpp LP 10M 100M FREQUENCY (Hz) MP -9 MP LP -15 1G Figure 5. Frequency Response at 5 V 14 -3 10k 100k 1M 10M FREQUENCY (Hz) 100M Figure 6. VOCM Frequency Response at 5 V Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 Typical Characteristics (continued) Unless otherwise specified, TA = 25°C, Avcl = +1, RF=RG = 1 kΩ, fully differential input, VS = +10 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted. -40 -40 f = 1KHz f = 1KHz -60 DISTORTION (dBc) DISTORTION (dBc) -60 -80 -100 HD2 -120 HD3 -140 -80 -100 HD2 -120 -140 HD3 -160 -160 0 2 4 6 8 10 12 14 16 18 DIFFERENTIAL OUTPUT (Vpp) 0 Figure 7. Distortion at 10 V, High Power 12 Figure 8. Distortion at 6.6 V, High Power -40 -40 f = 1KHz f = 1KHz -60 DISTORTION (dBc) -60 DISTORTION (dBc) 2 4 6 8 10 DIFFERENTIAL OUTPUT (Vpp) -80 -100 HD2 -120 -140 -80 -100 HD2 -120 -140 HD3 HD3 -160 -160 0 2 4 6 8 10 12 14 16 18 DIFFERENTIAL OUTPUT (Vpp) 0 Figure 9. Distortion at 10 V, Mid Power 12 Figure 10. Distortion at 6.6 V, Mid Power -40 -40 f = 1KHz f = 1KHz -60 DISTORTION (dBc) -60 DISTORTION (dBc) 2 4 6 8 10 DIFFERENTIAL OUTPUT (Vpp) -80 -100 HD2 -120 -140 -80 -100 HD2 -120 -140 HD3 -160 HD3 -160 0 2 4 6 8 10 12 14 16 18 DIFFERENTIAL OUTPUT (Vpp) Figure 11. Distortion at 10 V, Low Power 0 2 4 6 8 10 DIFFERENTIAL OUTPUT (Vpp) 12 Figure 12. Distortion at 6.6 V, Low Power Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 15 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com Typical Characteristics (continued) Unless otherwise specified, TA = 25°C, Avcl = +1, RF=RG = 1 kΩ, fully differential input, VS = +10 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted. 1 -40 f = 1 kHz BW = 22 kHz f = 1KHz 0.1 -80 THD+N (%) DISTORTION (dBc) -60 HD3 -100 LP 0.01 HP 0.001 -120 -140 0.00001 HD2 -160 0 1 2 3 4 5 6 7 DIFFERENTIAL OUTPUT (Vpp) MP 0.000001 0 8 2 10 12 14 16 18 20 1 f = 1 kHz BW = 22 kHz f = 1KHz -60 0.1 -80 THD+N (%) DISTORTION (dBc) 8 DIFFERENTIAL OUTPUT (Vp-p) -40 -100 HD2 LP 0.01 HP 0.001 -120 -140 0.0001 HD3 -160 0 1 2 3 4 5 6 7 DIFFERENTIAL OUTPUT (Vpp) MP 0.00001 0 8 2 4 6 8 10 12 DIFFERENTIAL OUTPUT (Vp-p) Figure 16. THD+N at 6.6 V Figure 15. Distortion at 5 V, Mid Power -40 1 f = 1 kHz BW = 22 kHz f = 1KHz -60 0.1 -80 THD+N (%) DISTORTION (dBc) 6 Figure 14. THD+N at 10 V Figure 13. Distortion at 5 V, High Power -100 HD2 -120 -140 0 1 2 3 4 5 6 7 DIFFERENTIAL OUTPUT (Vpp) 0.01 HP LP 0.001 MP 0.0001 HD3 -160 8 0.00001 0 1 2 3 4 5 6 7 8 9 10 DIFFERENTIAL OUTPUT (Vp-p) Figure 17. Distortion at 5 V, Low Power 16 4 Submit Documentation Feedback Figure 18. THD+N at 5 V Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 Typical Characteristics (continued) Unless otherwise specified, TA = 25°C, Avcl = +1, RF=RG = 1 kΩ, fully differential input, VS = +10 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted. 100 100 HP CURRENT NOISE (S$¥+]) VOLTAGE NOISE (Q9¥+]) HP MP 10 LP Differential Out Referred to Input 1 MP 10 LP 1 Differential Out Referred to Input 0.1 1 10 100 1k 10k FREQUENCY (Hz) 100k 1 Figure 19. Voltage Noise at 10 V 10 100 HP HP CURRENT NOISE (S$¥+]) VOLTAGE NOISE (Q9¥+]) 100k Figure 20. Current Noise at 10 V 100 LP 10 MP Differential Out Referred to Input 1 MP 10 LP 1 Differential Out Referred to Input 0.1 1 10 100 1k 10k FREQUENCY (Hz) 100k 1 Figure 21. Voltage Noise at 6.6 V 10 100 1k 10k FREQUENCY (Hz) 100k Figure 22. Current Noise at 6.6 V 100 100 HP HP CURRENT NOISE (S$¥+]) VOLTAGE NOISE (Q9¥+]) 100 1k 10k FREQUENCY (Hz) MP 10 LP Differential Out Referred to Input 1 MP 10 LP 1 Differential Out Referred to Input 0.1 1 10 100 1k 10k FREQUENCY (Hz) 100k Figure 23. Voltage Noise at 5 V 1 10 100 1k 10k FREQUENCY (Hz) 100k Figure 24. Current Noise at 5 V Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 17 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com Typical Characteristics (continued) Unless otherwise specified, TA = 25°C, Avcl = +1, RF=RG = 1 kΩ, fully differential input, VS = +10 V, RL = 2 kΩ//20 pF differentially, Input CMR and VOCM = mid-supply and HP mode unless otherwise noted. 1.5 MP HP DIFFERENTIAL OUTPUT (Vpp) DIFFERENTIAL OUTPUT (Vpp) 1.5 1.0 0.5 0.0 -0.5 LP -1.0 MP -1.5 0 40 0.5 0.0 -0.5 LP -1.0 MP -1.5 80 120 TIME (ns) 160 MP HP 1.0 200 0 Figure 25. Pulse Response at 10 V 40 80 120 TIME (ns) 160 200 Figure 26. Pulse Response at 6.6 V DIFFERENTIAL OUTPUT (Vpp) 1.5 HP MP 1.0 0.5 0.0 -0.5 LP -1.0 -1.5 MP 0 20 40 60 80 100 120 140 160 180 200 TIME (ns) Figure 27. Pulse Response at 5 V 18 Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 7 Detailed Description 7.1 Overview The LMP8350 is a fully-differential voltage feedback amplifier designed to drive precision differential ADC converters. The LMP8350, though fully integrated for ultimate balance and distortion performance, functionally provides three channels. Two of these channels are the V+ and V− signal path channels, which function similarly to inverting mode operational amplifiers and are the primary signal paths. The third channel is the common-mode (VOCM) feedback circuit. This is the circuit that sets the output common mode as well as driving the V+ and V− outputs to be equal magnitude and opposite phase, even when only one of the two input channels is driven. The common-mode feedback circuit allows for single-ended to differential operation. The output common-mode voltage is set by applying the appropriate voltage to the VOCM pin. 7.2 Functional Block Diagram V+ EN IN+ Vocm IN- + Vocm OUT+ OUT- V- 7.3 Feature Description 7.3.1 Full Bandwidth Limitations Although the LMP8350 has a unity gain bandwidth of over 200 MHz, it is primarily intended for lower sample rate, high-precision ADCs with baseband analog input signal bandwidths in the DC to <1 MHz range (not to be confused with sampling rate). The high open-loop bandwidth of the LMP8350 is used to provide ultra low distortion and fast settling times. Maximum power bandwidth is limited by the internal output common-mode feedback path, which is limited to 1 MHz to 5 MHz. Operation with input signals above 1 MHz with near full output swings can cause random shifts in the output common mode and possible AC instabilities. For this reason, the LMP8350 is not intended to be used wide bandwidth (> 1 MHz) signal paths. Single-ended inputs rely on the common-mode signal path and will have a bandwidth limited to that of the internal common-mode buffer. 7.3.2 ESD Protection The LMP8350 is protected against electrostatic discharge (ESD) on all pins. The LMP8350 will survive 2000-V human body model and 200-V machine model events. Under normal operation, the ESD diodes have no effect on circuit performance. There are occasions, however, when the ESD diodes will be evident. If the LMP8350 is driven by a large signal while the device is powered down the ESD diodes will conduct. The current that flows through the ESD diodes will either exit the chip through the supply pins or will flow through the device, hence it is possible to power up a chip with a large signal applied to the input pins. Using the shutdown mode is one way to conserve power and still prevent unexpected operation. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 19 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com 7.4 Device Functional Modes 7.4.1 Enable Pin and Power Mode Selection The LMP8350 is equipped with a four-level enable (EN) pin to select one of three power modes or shutdown. These modes are selected by applying the appropriate voltage to the EN pin. Each power level has a corresponding performance level. The high power mode will have the best overall BW and distortion performance, but at the cost of higher supply current and some DC accuracy. The low power mode has the lowest supply current, but with a noticeable loss of AC performance and output drive capabilities. The mid-power mode provides the best balance of AC and precision DC specifications. In disable mode, the amplifier is shutdown and the output stage goes into a high impedance state. Table 1 summarizes these performance trade-offs. Table 1. Performance vs. Power Mode Summary MODE High Med Low VS –3dB BW (MHz) HD2 (dBc) NOISE (nV/Hz) SR (V/µS) TYP VOS (mV) 10 118 –124.7 4.6 507 0.6 6.6 116 –124.7 4.5 488 0.3 5 114 –125.5 4.5 476 0.2 10 87 –122.8 4.8 393 0.08 6.6 85 –122.8 4.8 376 0.1 5 84 –122.6 4.8 366 0.1 10 31 –117.2 8 178 0.1 6.6 29 –117.2 8 166 0.1 5 28 –117 8 160 0.1 To set the mode, internally the voltage at the EN pin is compared against the total supply voltage (VS) and sets the current consumption as shown in the table below. The EN pin voltage is referenced to the V- pin. Table 2. Enable Pin Mode Selection VEN (VS = V+ - V-) POWER MODE VEN AT 10 V VEN AT 6.6 V VEN AT 5 V IS mA 7/8 × VS High 8.75 5.775 4.375 13 to 15 5/8 × VS Med 6.25 4.125 3.125 7 to 9 3/8 × VS Low 3.75 2.475 1.875 2 to 3 1/8 × VS Disable 1.25 0.825 0.625 <1 The enable pin should not be allowed to float. If the enable pin is not used it can be tied to V+ to select the high power mode or set with two resistors. Each power setting has a ±400-mV tolerance at each level, though TI recommends to keep the set voltage within the center of the range as performance may vary near the transition zones. During shutdown, both outputs are in a high impedance state, so the feedback and gain set resistors will then set the input and output impedance of the circuit. For this reason input to output isolation will be poor in the disabled state. The voltage at the EN pin can be generated with a resistive voltage divider or a buffer connected to a voltage source or a DAC. Figure 34 shows how to generate EN voltage with a resistive voltage divider. 20 Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 Values of RA and RB can be calculated to achieve the voltages in Table 2, however their sum should be below 50 kΩ to keep the voltage at the enable pin stable. Recommended values for RA and RB are given in Table 3. Table 3. Recommended RA and RB for Mode Selection MODE 10 V 6.6 V 5V VEN High Power RA = 0 RB = inf RA = 0 RB = inf RA = 0 RB = inf > 7/8 VS Mid Power RA = 18 K RB = 30 K RA = 18 K RB = 30 K RA = 18 K RB = 30 K 5/8 VS Low Power RA = 33 K RB = 18 K RA = 33 K RB = 18 K RA = 33 K RB = 18 K 3/8 VS Shutdown RA = Inf RB = 0 RA = Inf RB = 0 RA = Inf RB = 0 < 1/8 VS 7.4.2 VOCM Pin and Output Common-Mode Setting Output common-mode voltage is set by the VOCM pin. Both outputs will be offset in the same direction (phase) by an amount equal to the applied VOCM voltage. The VOCM pin, if left unconnected, will self-bias to mid-supply. Two internal 60-kΩ resistors set this midpoint. These resistors are shown in Figure 28. + V 60 k: Internal Circuitry VOCM Input 60 k: V - Figure 28. VOCM Internal Bias Circuit The equivalent resistance looking into the VOCM pin will look like 30 kΩ to mid-supply, plus about ±700 nA for internal base currents (which scales with power mode and supply current). If left floating, the VOCM input should be bypassed to ground with a 0.1-µF ceramic capacitor. If a different output common-mode voltage is desired, the VOCM pin should be driven by a clean, low impedance source to override the internal divider resistors. The VOCM pin should be bypassed to ground with a 0.1-µF ceramic capacitor. It should be noted that any signal or noise-coupling into the VOCM will be passed as commonmode noise and may result in the loss of dynamic range, degraded CMRR, degraded balance and higher distortion. The VOCM pin is primarily intended as a DC bias path and is not intended for use as a signal path. For applications that can tolerate slight shifts in the VOCMvoltage over temperature, it is also possible to use a single resistor to program the VOCM voltage by paralleling one of the internal resistors to change the ratio. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 21 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com 8 Application and Implementation NOTE Information in the following applications sections is not part of the TI component specification, and TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining suitability of components for their purposes. Customers should validate and test their design implementation to confirm system functionality. 8.1 Application Information 8.1.1 Fully-Differential Operation The LMP8350 will perform best when used with split supplies and in a fully-differential configuration. See Figure 29 for recommend circuits. RF1 RO RG1 + VI a CL VOCM RL VO RG2 RO RF2 EN Figure 29. Typical Fully-Differential Application The circuit shown in Figure 29 is a typical fully-differential application as might be used to drive a Sigma Delta ADC. In this circuit, closed-loop gain is calculated by Equation 1: (AV) = VOUT/ VIN = RF/RG where • RF=RF1=RF2 and RG=RG1=RG2 (1) For all the applications in this data sheet , VIN is presumed to be the voltage presented to the circuit by the signal source. For differential signals this will be the difference of the signals on each input (which will be double the magnitude of each individual signal), while in single-ended inputs it will just be the driven input signal. When fed with a differential signal, the LMP8350 provides excellent distortion, balance and common-mode rejection, provided the resistors RF, RG and any input termination resistors (RT) are well-matched and strict symmetry is observed in board layout. With a DC CMRR of over 80 dB, the DC and low frequency CMRR of most circuits will be dominated by the external resistor matching and board trace resistance. At low distortion levels, board layout symmetry and supply bypassing become a factor as well. It is assumed throughout this document that RF1 = RF2 and RG1 = RG2 for maximum channel symmetry Precision resistors of at least 0.1% accuracy or better are recommended and careful board layout will also be required for optimum performance. Operation with RF feedback resistors as low as 300 Ω is possible in the high and medium power modes. This will slightly improve the noise and bandwidth results. However, feedback resistors with RF values of less than 1 KΩ should be avoided in the low power mode due to the reduced output drive current capabilities. If low value resistors (< 300 Ω) must be used in the low power mode, the maximum output swing will need to be limited. The resistors RO help keep the amplifier stable when presented with a load CL, as is common when driving an analog to digital converter (ADC). 22 Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 Application Information (continued) 1000 100: TWISTED PAIR 50: 500 + 2 VPP a VOCM 500 2 VPP 50: 1000 GAIN = 2 EN Figure 30. Fully-Differential Cable Driver With up to 15 VPP differential output voltage swing and 80 mA of linear drive current, the LMP8350 makes an excellent precision cable driver as shown in Figure 30. The LMP8350 is also suitable for driving differential cables from a single-ended source. 8.1.2 Single Supply Operation As shown in Figure 31, the input common-mode voltage is less than the output common voltage. It is set by current flowing through the feedback network from the device output. The input common-mode voltage range places constraints on gain settings. The input common-mode voltage is calculated in Equation 2. Possible solutions to this limitation include AC coupling the input signal, using split power supplies and limiting stage gain. AC coupling with single-supply is shown in Figure 32. VICM= Input common-mode voltage = (V+IN + V−IN)/2. (2) RF RO VO1 RG RS VI1 + VI a CL VOCM RT RL VO RG VI2 VO2 RM RO RF EN *VCM = VO1 + VO2 2 *BY DESIGN VICM = VOCM * (RG + RM) (RG + RM + RF) =a VOCM 1 + AV WHERE RM << RG Figure 31. Relating AV to Input/Output Common-Mode Voltages In Figure 31 the differential closed loop gain is = AV= RF/RG. NOTE In single-ended to differential operation VIN is measured single ended while VOUT is measured differentially. This means that gain is really one-half, or 6 dB, less when measured on either of the output pins separately. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 23 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com Application Information (continued) RF RO VO1 VI1 RG RS + VI a RT RL CL VOCM VO RG VI2 RM VO2 RO RF EN *VCM = VICM = VOCM VO1 + VO2 2 *BY DESIGN VICM = VI1 + VI2 2 Figure 32. AC Coupled for Single-Supply Operation 8.1.3 Driving Analog to Digital Converters Analog to digital converters (ADC) present challenging load conditions. They typically have high impedance inputs with large and often variable capacitive components. As well, there are usually current spikes associated with switched capacitor or sample and hold circuits. Figure 33 shows a typical circuit for driving an ADC. The two resistors serve to isolate the capacitive loading of the ADC from the amplifier and ensure stability. In addition, the resistors form part of a lowpass filter which helps to provide anti alias and noise reduction functions. The CS capacitor helps to smooth the current spikes associated with the internal switching circuits of the ADC and also are a key component in the lowpass filtering of the ADC input. The capacitor should be a low distortion capacitor, such as an NPO, to avoid causing significant distortion terms. In the circuit of Figure 33, the cutoff frequency of the filter is calculated by Equation 3. This should be slightly less than the sampling frequency. 1 / (2 × π × (RISO1 + RISO2) × (CS + CCONVERTER)) (3) NOTE The ADC input capacitance must be factored into the frequency response of the input filter. Also as shown in Figure 33, the input capacitance to many ADCs is variable based on the clock cycle. For lower-speed, precision ADC's, the external cap is generally sized to ten times the internal sampling capacitor value. See the data sheet for your particular ADC for details. RF1 RISO1 RG1 + VI a VOCM CS - A/D 8-18 pF RG2 RISO2 RF2 VREF EN LOW IMPEDANCE VOLTAGE REFERENCE Figure 33. Driving an ADC 24 Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 Application Information (continued) The amplifier and ADC muist be located as close together as possible. Both devices require that the filter components be in close proximity to them. The amplifier needs to have minimal parasitic loading on the output traces, and the ADC is sensitive to high-frequency noise that may couple in on its input lines. Some high performance ADCs have an input stage that has a bandwidth of several times its sample rate. The sampling process results in all input signals presented to the input stage mixing down into the Nyquist range (DC to Fs/2). See AN-236 (SNAA079) for more details on the subsampling process and the requirements this imposes on the filtering necessary in your system. 8.1.4 Capacitive Drive As noted in the Driving Analog to Digital Converters section, capacitive loads should be isolated from the amplifier output with small valued resistors. This is particularly the case when the load has a resistive component that is 500 Ω or higher. A typical ADC has capacitive components of around 8 to 18 pF, and the resistive component could be 1000 Ω or higher. If driving a transmission line, such as a twisted pair, using matching resistors will be sufficient to isolate any subsequent capacitance. 8.2 Typical Application Figure 34 shows a typical application where an LMP8350 is used to produce a differential signal from a singleended source. RF RO RG RS VI + a RT RL CL VOCM VO RG RM RO RF EN SET RM = RT||RS 1 - 1 RIN § ¨¨ © § 1 ¨ © RS RIN = RG RF § 1- ¨ 2 * (R F + RG) © § ¨¨ © SET RT = Figure 34. Single-Ended in Differential Out 8.2.1 Design Requirements Compared to a differential input, using a single-ended input will reduce gain by 1/2, so that the closed-loop gain will be calculated by Equation 4: Gain = Av = 0.5 × RF / RG (4) In single-ended input operation the output common-mode voltage is set by the VOCM pin. Also, In this mode the common-mode feedback circuit must recreate the signal that is not present on the unused differential input pin. The common-mode feedback circuit is responsible for ensuring balanced output with a single-ended input. Balance error is defined as the amount of input signal that couples into the output common mode. It is measured as the undesired output common-mode swing divided by the signal on the input. Balance error can be caused by either a channel to channel gain error, or phase error. Either condition will produce a common-mode shift. The overall bandwidth is limited due to the VOCM buffer bandwidth limitations in this configuration. Supply and VOCM pin bypassing are also critical in this mode of operation. 8.2.2 Detailed Design Procedure For a single-ended input differential output configuration Figure 34, component value selection is dictated by the gain and input resistance desired. Figure 35 shows the OUT+ and OUT– relative to the single ended voltage signal input +. Depending on the feedback resistor values, the amplitude gain of the OUT+ and OUT– will vary. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 25 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com Typical Application (continued) 8.2.3 Application Curve Voltage VA OUT+ OUTV+ VIN 0 Time -VIN -VA Figure 35. Single-Ended In Differential Out Amplitude vs Time Waveform 26 Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 9 Power Supply Recommendations 9.1 Power Supply and VOCM Bypassing The LMP8350 requires supply bypassing capacitors as shown in Figure 36 and Figure 37 for fastest settling time and overall stability. + V 0.01 PF 10 PF + VOCM 0.1 PF 0.1 PF 0.01 PF 10 PF V - Figure 36. Split-Supply Bypassing Capacitors The 0.01-µF and 0.1-µF capacitors should be leadless surface mount (SMT) ceramic capacitors and should be no more than 3 mm from the supply pins. The SMT capacitors should be connected directly to a ground plane. Thin traces or small vias will reduce the effectiveness of bypass capacitors. V + 0.01 PF 0.1 PF 10 PF + VOCM 0.1 PF Figure 37. Single-Supply Bypassing Capacitors Also shown in Figure 36 and Figure 37 is a capacitor from the VOCM pin to ground. The VOCM pin sets the output common-mode voltage. Any noise on this input is transferred directly to the output. The VOCM pin should be bypassed even if the pin in not used. There is an internal resistive divider on chip to set the output commonmode voltage to the midpoint of the supply pins. The impedance looking into this pin is approximately 30 kΩ. If a different output common-mode voltage is desired drive this pin with a clean, accurate voltage reference. Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 27 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com 10 Layout 10.1 Layout Guidelines While the main signal path frequencies may be fairly low, the ultra low distortion and settling time specifications rely on wide internal bandwidths. Precautions usually taken for high-speed amplifiers should be followed to maintain the best settling times and lowest distortion specifications. In order to get maximum benefit from the differential circuit architecture, board layout and component selection is very critical. The circuit board should have low a inductance ground plane and well bypassed broad supply lines. External components should be leadless surface mount types. The feedback network and output matching resistors should be composed of short traces and precision resistors (0.1%). The output matching resistors should be placed within 3-4 mm of the amplifier as should the supply bypass capacitors. The LMP8350 is sensitive to parasitic capacitances on the outputs. Ground and power plane metal should be removed from beneath the amplifier and from beneath RF and RG. With any differential signal path symmetry is very important. Even small amounts of asymmetry will contribute to distortion and balance errors. Special attention should be paid to where the bypass capacitors are grounded, as this also affects settling and distortion performance. The LMH730154 evaluation board is an example of good layout techniques. Evaluation boards are available for purchase through the product folder on TI’s website. 10.2 Layout Example 2 VOUT- 2 GND 2 GND 1 VSS 1 VSS 2 VSS 1 VCC 1 + 1 - 2 VOUT+ 5 VOUT- 4 VOUT+ 6 VSS 3 VCC 7 VCC 2 8 + 1 - 2 GND 1 VCC 1 VCC 2 GND 2 + 1 VI NP 1 VINN 2 - Figure 38. Layout Example 28 Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 LMP8350 www.ti.com SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 10.3 Power Dissipation The LMP8350 is optimized for maximum performance in the small form factor of the standard SOIC package, and is essentially a dual-channel amplifier. To ensure maximum output drive and highest performance, thermal shutdown is not provided. Therefore, it is of utmost importance to make sure that the TJMAX of 150°C is never exceeded due to the overall power dissipation. Follow these steps to determine the Maximum power dissipation for the LMP8350: 1. Calculate the quiescent (no-load) power using Equation 5 (Be sure to include any current through the feedback network if VOCM is not mid-rail.): PAMP = ICC× (VS) where VS = V+ – V−. • (5) 2. Calculate the RMS power dissipated in each of the output stages using Equation 6: PD (rms) = rms ((VS – V+OUT) × I+OUT) + rms ((VS − V−OUT) × I−OUT) where • VOUT and IOUT are the voltage and the current measured at the output pins of the differential amplifier as if they were single ended amplifiers and VS is the total supply voltage. (6) 3. Calculate the total RMS power: PT = PAMP + PD. The maximum power that the LMP8350 package can dissipate at a given temperature can be derived from Equation 7: PMAX = (150° – TAMB)/ θJA where • • TAMB = Ambient temperature (°C) and θJA = Thermal resistance, from junction to ambient, for a given package (°C/W). For the SOIC package θJA is 150°C/W. (7) NOTE If VOCM is not 0 V then there will be quiescent current flowing in the feedback network. This current should be included in the thermal calculations and added into the quiescent power dissipation of the amplifier. 10.4 Evaluation Board Generally, a good high-frequency layout will keep power supply and ground traces away from the inverting input and output pins. Parasitic capacitances on these nodes to ground will cause frequency response peaking and possible circuit oscillations (see Application Note OA-15 (SNOA367) for more information). Texas Instruments suggests the following evaluation boards in Table 4 as a guide for high-frequency layout and as an aid in device testing and characterization: Table 4. Evaluation Board Guide DEVICE PACKAGE EVALUATION BOARD PART NUMBER LMP8350MA SOIC LMH730154 Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 29 LMP8350 SNOSB80C – FEBRUARY 2011 – REVISED OCTOBER 2015 www.ti.com 11 Device and Documentation Support 11.1 Documentation Support 11.1.1 Related Documentation For related documentation, see the following: • Absolute Maximum Ratings for Soldering, SNOA549 • AN-236 An Introduction to the Sampling Theorem, SNAA079 • OA-15 Frequent Faux Pas in Applying Wideband Current Feedback Amplifiers, SNOA367 11.2 Community Resources The following links connect to TI community resources. Linked contents are provided "AS IS" by the respective contributors. They do not constitute TI specifications and do not necessarily reflect TI's views; see TI's Terms of Use. TI E2E™ Online Community TI's Engineer-to-Engineer (E2E) Community. Created to foster collaboration among engineers. At e2e.ti.com, you can ask questions, share knowledge, explore ideas and help solve problems with fellow engineers. Design Support TI's Design Support Quickly find helpful E2E forums along with design support tools and contact information for technical support. 11.3 Trademarks LMP, E2E are trademarks of Texas Instruments. PowerWise is a trademark of National Semiconductor Corporation. All other trademarks are the property of their respective owners. 11.4 Electrostatic Discharge Caution These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. 11.5 Glossary SLYZ022 — TI Glossary. This glossary lists and explains terms, acronyms, and definitions. 12 Mechanical, Packaging, and Orderable Information The following pages include mechanical, packaging, and orderable information. This information is the most current data available for the designated devices. This data is subject to change without notice and revision of this document. For browser-based versions of this data sheet, refer to the left-hand navigation. 30 Submit Documentation Feedback Copyright © 2011–2015, Texas Instruments Incorporated Product Folder Links: LMP8350 PACKAGE OPTION ADDENDUM www.ti.com 18-Sep-2015 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (°C) Device Marking (4/5) LMP8350MA/NOPB ACTIVE SOIC D 8 95 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 85 LMP83 50MA LMP8350MAX/NOPB ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM -40 to 85 LMP83 50MA (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) Eco Plan - The planned eco-friendly classification: Pb-Free (RoHS), Pb-Free (RoHS Exempt), or Green (RoHS & no Sb/Br) - please check http://www.ti.com/productcontent for the latest availability information and additional product content details. TBD: The Pb-Free/Green conversion plan has not been defined. Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes. Pb-Free (RoHS Exempt): This component has a RoHS exemption for either 1) lead-based flip-chip solder bumps used between the die and package, or 2) lead-based die adhesive used between the die and leadframe. The component is otherwise considered Pb-Free (RoHS compatible) as defined above. Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. 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Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 18-Sep-2015 TAPE AND REEL INFORMATION *All dimensions are nominal Device LMP8350MAX/NOPB Package Package Pins Type Drawing SOIC D 8 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2500 330.0 12.4 Pack Materials-Page 1 6.5 B0 (mm) K0 (mm) P1 (mm) 5.4 2.0 8.0 W Pin1 (mm) Quadrant 12.0 Q1 PACKAGE MATERIALS INFORMATION www.ti.com 18-Sep-2015 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LMP8350MAX/NOPB SOIC D 8 2500 367.0 367.0 35.0 Pack Materials-Page 2 IMPORTANT NOTICE Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. 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