LMH6611/LMH6612 Single Supply 345 MHz Rail-to-Rail Output Amplifiers General Description Features The LMH6611 (single, with shutdown) and LMH6612 (dual) are 345 MHz rail-to-rail output amplifiers consuming just 3.2 mA of quiescent current per channel and designed to deliver high performance in power conscious single supply systems. The LMH6611 and LMH6612 have precision trimmed input offset voltages with low noise and low distortion performance as required for high accuracy video, test and measurement, and communication applications. The LMH6611 and LMH6612 are members of the PowerWise family and have an exceptional power-to-performance ratio. With a trimmed input offset voltage of 0.022 mV and a high open loop gain of 103 dB the LMH6611 and LMH6612 meet the requirements of DC sensitive high speed applications such as low pass filtering in baseband I and Q radio channels. These specifications combined with a 0.01% settling time of and better than 102 dBc 100 ns, a low noise of 10 nV/ SFDR at 100 kHz make these amplifiers particularly suited to driving 10, 12 and 14-bit high speed ADCs. The 45 MHz 0.1 dB bandwidth (AV = 2) driving 2 VPP into 150 allows the amplifiers to be used as output drivers in 1080i and 720p HDTV applications. The input common mode range extends from 200 mV below the negative supply rail up to 1.2V from the positive rail. On a single 5V supply with a ground terminated 150 load the output swings to within 49 mV of the ground, while a mid-rail terminated 1 k load will swing to 77 mV of either rail. The amplifiers will operate on a 2.7V to 11V single supply or 1.35V to 5.5V split supply. The LMH6611 single is available in 6-Pin TSOT23 and has an independent active low disable pin which reduces the supply current to 120 A. The LMH6612 is available in 8-Pin SOIC. Both the LMH6611 and LMH6612 are available in -40C to +125C extended industrial temperature grade. VS = 5V, RL = 1 k, TA = 25C and AV = +1, unless otherwise specified. 2.7V to 11V Operating voltage range 3.2 mA Supply current per channel 345 MHz Small signal bandwidth 103 dB Open loop gain 0.750 mV Input offset voltage (limit at 25C) 460 V/s Slew rate 45 MHz 0.1 dB bandwidth 67 ns Settling time to 0.1% 100 ns Settling time to 0.01% 102 dBc SFDR (f = 100 kHz, AV = 2, VOUT = 2 VPP) 10 nV/Hz Low voltage noise 100 mA Output current -0.2V to 3.8V CMVR Rail-to-Rail output -40C to +125C temperature range Applications ADC driver DAC buffer Active filters High speed sensor amplifier Current sense amplifier 1080i and 720p analog video amplifier STB, TV video amplifier Video switching and muxing Typical Application 30033629 WEBENCH(R) is a registered trademark of National Semiconductor Corporation. (c) 2010 National Semiconductor Corporation 300336 www.national.com LMH6611/LMH6612 Single Supply 345 MHz Rail-to-Rail Output Amplifiers January 26, 2010 LMH6611/LMH6612 Supply Voltage (VS = V+ - V-) Junction Temperature (Note 3) Absolute Maximum Ratings (Note 1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Operating Ratings V+ 12V 150C max (Note 1) Supply Voltage (VS = - Ambient Temperature Range (Note 3) ESD Tolerance (Note 2) Human Body Model For input pins only For all other pins Machine Model Charge Device Model V-) 2.7V to 11V -40C to +125C Package Thermal Resistance (JA) 6-Pin TSOT23 8-Pin SOIC 2000V 2000V 200V 1000V 231C/W 160C/W +3V Electrical Characteristics Unless otherwise specified, all limits are guaranteed for TJ = +25C, V+ = 3V, V- = 0V, VS = V+ - V-, DISABLE = 3V, VCM = VO = V+/2, AV = +1, RF = 0, when AV +1 then RF = 560, RL = 1 k. Boldface limits apply at temperature extremes. (Note 4) Symbol Parameter Condition Min (Note 8) Typ (Note 7) Max (Note 8) Units Frequency Domain Response SSBW GBW LSBW -3 dB Bandwidth Small Signal AV = 1, RL = 1 k, VOUT = 0.2 VPP 305 AV = 2, -1, RL = 1 k, VOUT = 0.2 VPP 115 Gain Bandwidth (LMH6611) AV = 10, RF = 2 k, RG = 221, RL = 1 k, VOUT = 0.2 VPP Gain Bandwidth (LMH6612) AV = 10, RF = 2 k, RG = 221, RL = 1 k, VOUT = 0.2 VPP 130 -3 dB Bandwidth Large Signal AV = 1, RL = 1 k, VOUT = 1.5 VPP 90 AV = -1, RL = 150, VOUT = 2 VPP 85 115 MHz 135 Peak Peaking AV = 1 1.0 0.1 dBBW 0.1 dB Bandwidth AV = 1, VOUT = 0.5 VPP, RL = 1 k 33 AV = 2, VOUT = 0.5 VPP, RL = 1 k 65 RF = RG = 560 MHz MHz dB MHz AV = 2, VOUT = 1.5 VPP, RL = 150, 47 RF = RG = 510 DG Differential Gain AV = 2, 4.43 MHz, 0.6V < VOUT < 2V, 0.03 % 0.06 deg RL = 150 to V+/2 DP Differential Phase AV = 2, 4.43 MHz, 0.6V < VOUT < 2V, RL = 150 to V+/2 Time Domain Response tr/tf Rise & Fall Time 1.5V Step, AV = 1 2.8 ns SR Slew Rate 2V Step, AV = 1 330 V/s ts_0.1 0.1% Settling Time 2V Step, AV = -1 74 ts_0.01 0.01% Settling Time 2V Step, AV = -1 116 fC = 100 kHz, AV = -1, VOUT= 2 VPP 109 fC = 1 MHz, AV = -1, VOUT = 2 VPP 97 ns Noise and Distortion Performance SFDR Spurious Free Dynamic Range dBc fC = 5 MHz, AV = -1, VOUT = 2 VPP 80 en Input Voltage Noise f = 100 kHz 10 nV/ in Input Current Noise f = 100 kHz 2 pA/ CT Crosstalk (LMH6612) f = 5 MHz, VIN = 2 VPP 71 www.national.com 2 dB Parameter Condition Min (Note 8) Typ (Note 7) Max (Note 8) Units Input, DC Performance VOS Input Offset Voltage (LMH6611) VCM = 0.5V 0.022 0.600 1.0 Input Offset Voltage (LMH6612) VCM = 0.5V -0.015 0.750 1.3 mV V/C TCVOS Input Offset Voltage Average Drift (Note 5) 0.1 IB Input Bias Current -5.9 -10.1 -11.1 A IO Input Offset Current 0.01 0.5 0.7 A CIN Input Capacitance 2.5 RIN Input Resistance CMVR Input Voltage Range DC, CMRR 76 dB CMRR Common Mode Rejection Ratio VCM Stepped from -0.1V to 1.7V 79 98 AOL Open Loop Gain RL = 1 k, VOUT = 2.7V to 0.3V 89 101 RL = 150, VOUT = 2.5V to 0.5V 78 85 VCM = 0.5V pF 6 -0.2 M 1.8 V dB dB Output DC Characteristics VO Output Swing High (LMH6611) (Voltage from V+ Supply Rail) Output Swing Low (LMH6611) (Voltage from V- Supply Rail) Output Swing High (LMH6612) (Voltage from V+ Supply Rail) Output Swing Low (LMH6612) (Voltage from V- Supply Rail) RL = 1 k to V+/2 59 72 76 RL = 150 to V+/2 133 169 182 RL = 1 k to V+/2 59 74 80 RL = 150 to V+/2 133 171 188 RL = 150 to V- 42 52 56 RL = 1 k to V+/2 58 68 73 RL = 150 to V+/2 131 157 172 RL = 1 k to V+/2 61 71 79 RL = 150 to V+/2 139 168 187 RL = 150 to V- 43 51 56 mV IOUT Linear Output Current VOUT = V+/2 (Note 6) 70 mA RO Output Resistance f = 1 MHz 0.07 0.001 A Enable Pin Operation Enable High Voltage Threshold Enabled (Note 9) Enable Pin High Current VDISABLE = 3V Enable Low Voltage Threshold Disabled (Note 9) Enable Pin Low Current VDISABLE = 0V 2.0 V 1.0 V 0.8 A ton Turn-On Time 18 ns toff Turn-Off Time 50 ns 3 www.national.com LMH6611/LMH6612 Symbol LMH6611/LMH6612 Symbol Parameter Condition Min (Note 8) Typ (Note 7) Max (Note 8) Units Power Supply Performance PSRR Power Supply Rejection Ratio DC, VCM = 0.5V, VS = 2.7V to 11V IS Supply Current (LMH6611) ISD 81 96 dB RL = 3.0 3.4 3.8 Supply Current (LMH6612) (per channel) RL = 2.95 3.45 3.9 Disable Shutdown Current (LMH6611) DISABLE = 0V 101 132 mA A +5V Electrical Characteristics Unless otherwise specified, all limits are guaranteed for TJ = +25C, V+ = 5V, V- = 0V, VS = V+ - V-, DISABLE = 5V, VCM = VO = V+/2, AV = +1, RF = 0, when AV +1 then RF = 560, RL = 1 k. Boldface limits apply at temperature extremes. Symbol Parameter Condition Min (Note 8) Typ (Note 7) Max (Note 8) Units Frequency Domain Response SSBW GBW LSBW -3 dB Bandwidth Small Signal AV = 1, RL = 1 k, VOUT = 0.2 VPP 345 AV = 2, -1, RL = 1 k, VOUT = 0.2 VPP 112 Gain Bandwidth (LMH6611) AV = 10, RF = 2 k, RG = 221, RL = 1 k, VOUT = 0.2 VPP Gain Bandwidth (LMH6612) AV = 10, RF = 2 k, RG = 221, RL = 1 k, VOUT = 0.2 VPP 130 -3 dB Bandwidth Large Signal AV = 1, RL = 1 k, VOUT = 2 VPP 77 AV = 2, RL = 150, VOUT = 2 VPP 85 115 MHz 135 Peak Peaking AV = 1 0.3 0.1 dBBW 0.1 dB Bandwidth AV = 1, VOUT = 0.5 VPP, RL = 1 k 45 AV = 2, VOUT = 0.5 VPP, RL = 1 k 68 RF = RG = 680 MHz MHz dB MHz AV = 2, VOUT = 2 VPP, RL = 150, 45 RF = RG = 665 DG Differential Gain AV = 2, 4.43 MHz, 0.6V < VOUT < 2V, 0.05 % 0.06 deg RL = 150 to V+/2 DP Differential Phase AV = 2, 4.43 MHz, 0.6V < VOUT < 2V, RL = 150 to V+/2 Time Domain Response tr/tf Rise & Fall Time 2V Step, AV = 1 3.6 ns SR Slew Rate 2V Step, AV = 1 460 V/s ts_0.1 0.1% Settling Time 2V Step, AV = -1 67 ts_0.01 0.01% Settling Time 2V Step, AV = -1 100 fC = 100 kHz, AV = 2, VOUT = 2 VPP 102 fC = 1 MHz, AV = 2, VOUT = 2 VPP 96 fC = 5 MHz, AV = 2, VO = 2 VPP 82 ns Distortion and Noise Performance SFDR Spurious Free Dynamic Range dBc en Input Voltage Noise f = 100 kHz 10 nV/ in Input Current Noise f = 100 kHz 2 pA/ CT Crosstalk (LMH6612) f = 5 MHz, VIN = 2 VPP 71 www.national.com 4 dB Parameter Condition Min (Note 8) Typ (Note 7) Max (Note 8) Units Input, DC Performance VOS Input Offset Voltage (LMH6611) VCM = 0.5V 0.013 0.600 1.0 Input Offset Voltage (LMH6612) VCM = 0.5V 0.022 0.750 1.3 TCVOS Input Offset Voltage Average Drift (Note 5) 0.1 IB Input Bias Current VCM = 0.5V -6.3 -10.1 -11.1 A IO Input Offset Current 0.01 0.5 0.7 A CIN Input Capacitance 2.5 pF RIN Input Resistance 6 M CMVR Input Voltage Range DC, CMRR 78 dB CMRR Common Mode Rejection Ratio VCM Stepped from -0.1V to 3.7V 81 98 AOL Open Loop Gain RL = 1 k, VOUT = 4.6V to 0.4V 92 103 RL = 150, VOUT = 4.4V to 0.6V 80 86 -0.2 mV V/C 3.8 V dB dB Output DC Characteristics VO Output Swing High (LMH6611) (Voltage from V+ Supply Rail) Output Swing Low (LMH6611) (Voltage from V- Supply Rail) Output Swing High (LMH6612) (Voltage from V+ Supply Rail) Output Swing Low (LMH6612) (Voltage from V- Supply Rail) RL = 1 k to V+/2 76 90 93 RL =150 to V+/2 195 239 256 RL = 1 k to V+/2 74 92 98 RL =150 to V+/2 193 243 265 RL = 150 to V- 48 60 64 RL = 1 k to V+/2 75 86 91 RL =150 to V+/2 195 223 241 RL = 1 k to V+/2 77 88 98 RL =150 to V+/2 202 234 261 RL = 150 to V- 49 58 64 mV IOUT Linear Output Current VOUT = V+/2 (Note 6) 100 mA RO Output Resistance f = 1 MHz 0.07 1.2 A Enable Pin Operation Enable High Voltage Threshold Enabled (Note 9) Enable Pin High Current VDISABLE = 5V Enable Low Voltage Threshold Disabled (Note 9) Enable Pin Low Current VDISABLE = 0V 3.0 V 2.0 V 2.8 A ton Turn-On Time 20 ns toff Turn-Off Time 60 ns 5 www.national.com LMH6611/LMH6612 Symbol LMH6611/LMH6612 Symbol Parameter Condition Min (Note 8) Typ (Note 7) Max (Note 8) Units Power Supply Performance PSRR Power Supply Rejection Ratio DC, VCM = 0.5V, VS = 2.7V to 11V IS Supply Current (LMH6611) ISD 81 96 dB RL = 3.2 3.6 4.0 Supply Current (LMH6612) (per channel) RL = 3.2 3.7 4.25 Disable Shutdown Current (LMH6611) DISABLE = 0V 120 162 mA A 5V Electrical Characteristics Unless otherwise specified, all limits are guaranteed for TJ = +25C, V+ = 5V, V- = -5V, VS = V+ - V-, DISABLE = 5V, VCM = VO = 0V, AV = +1, RF = 0, when AV +1 then RF = 560, RL = 1 k. Boldface limits apply at temperature extremes. Symbol Parameter Condition Min (Note 8) Typ (Note 7) Max (Note 8) Units Frequency Domain Response SSBW GBW LSBW -3 dB Bandwidth Small Signal AV = 1, RL = 1 k, VOUT = 0.2 VPP 365 AV = 2, -1, RL = 1 k, VOUT = 0.2 VPP 110 Gain Bandwidth (LMH6611) AV = 10, RF = 2 k, RG = 221, RL = 1 k, VOUT = 0.2 VPP Gain Bandwidth (LMH6612) AV = 10, RF = 2 k, RG = 221, RL = 1 k, VOUT = 0.2 VPP 130 -3 dB Bandwidth Large Signal AV = 1, RL = 1 k, VOUT = 2 VPP 85 AV = 2, RL = 150, VOUT = 2 VPP 87 115 MHz 135 Peak Peaking AV = 1 0.1 dBBW 0.1 dB Bandwidth AV = 1, VOUT = 0.5 VPP, RL = 1 k 0.01 92 AV = 2, VOUT = 0.5 VPP, RL = 1 k 65 RF = RG = 750 MHz MHz dB MHz AV = 2, VOUT = 2 VPP, RL = 150, 45 RF = RG = 680 DG Differential Gain AV = 2, 4.43 MHz, 0.6V < VOUT < 2V, 0.05 % 0.05 deg RL = 150 to V+/2 DP Differential Phase AV = 2, 4.43 MHz, 0.6V < VOUT < 2V, RL = 150 to V+/2 Time Domain Response tr/tf Rise & Fall Time 2V Step, AV = 1 3.5 ns SR Slew Rate 2V Step, AV = 1 460 V/s ts_0.1 0.1% Settling Time 2V Step, AV = -1 60 ts_0.01 0.01% Settling Time 2V Step, AV = -1 100 fC = 100 kHz, AV = 2, VOUT = 2 VPP 102 fC = 1 MHz, AV = 2, VOUT = 2 VPP 100 fC = 5 MHz, AV = 2, VOUT = 2 VPP 81 ns Noise and Distortion Performance SFDR Spurious Free Dynamic Range dBc en Input Voltage Noise f = 100 kHz 10 nV/ in Input Current Noise f = 100 kHz 2 pA/ CT Crosstalk (LMH6612) f = 5 MHz, VIN = 2 VPP 71 www.national.com 6 dB Parameter Condition Min (Note 8) Typ (Note 7) Max (Note 8) Units Input DC Performance VOS Input Offset Voltage (LMH6611) VCM = -4.5V 0.074 0.600 1.1 Input Offset Voltage (LMH6612) VCM = -4.5V 0.095 0.750 1.4 TCVOS Input Offset Voltage Average Drift (Note 5) 0.4 IB Input Bias Current VCM = -4.5V -6.5 -10.1 -11.1 A IO Input Offset Current 0.01 0.5 0.7 A CIN Input Capacitance 2.5 pF RIN Input Resistance 6 M CMVR Input Voltage Range DC, CMRR 81 dB CMRR Common Mode Rejection Ratio VCM Stepped from -5.1V to 3.7V 81 98 AOL Open Loop Gain RL = 1 k, VOUT = +4.6V to -4.6V 96 103 RL = 150, VOUT = +4.3V to -4.3V 80 87 -5.2 mV V/C 3.8 V dB dB Output DC Characteristics VO Output Swing High (LMH6611) (Voltage from V+ Supply Rail) Output Swing Low (LMH6611) (Voltage from V- Supply Rail) Output Swing High (LMH6612) (Voltage from V+ Supply Rail) Output Swing Low (LMH6612) (Voltage from V- Supply Rail) RL = 1 k to GND 107 125 130 RL = 150 to GND 339 402 433 RL = 1 k to GND 103 123 132 RL = 150 to GND 332 404 445 RL = 150 to V- 54 70 74 RL = 1 k to GND 107 118 125 RL = 150 to GND 340 375 407 RL = 1 k to GND 108 120 135 RL = 150 to GND 348 389 434 RL = 150 to V- 56 66 74 mV IOUT Linear Output Current VOUT = GND (Note 6) 120 mA RO Output Resistance f = 1 MHz 0.07 17.0 A Enable Pin Operation Enable High Voltage Threshold Enabled (Note 9) Enable Pin High Current VDISABLE = +5V Enable Low Voltage Threshold Disabled (Note 9) Enable Pin Low Current VDISABLE = -5V 0.5 V -0.5 V 18.6 A ton Turn-On Time 19 ns toff Turn-Off Time 60 ns 7 www.national.com LMH6611/LMH6612 Symbol LMH6611/LMH6612 Symbol Parameter Condition Min (Note 8) Typ (Note 7) Max (Note 8) Units Power Supply Performance PSRR Power Supply Rejection Ratio DC, VCM = -4.5V, VS = 2.7V to 11V IS Supply Current (LMH6611) ISD 81 96 dB RL = 3.3 3.8 4.4 Supply Current (LMH6612) (per channel) RL = 3.45 4.05 4.85 Disable Shutdown Current (LMH6611) DISABLE = -5V 160 212 mA A Note 1: 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 guaranteed. For guaranteed specifications and the test conditions, see the Electrical Characteristics. Note 2: 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). Note 3: The maximum power dissipation is a function of TJ(MAX), JA. The maximum allowable power dissipation at any ambient temperature is PD = (TJ(MAX)) - TA)/ JA. All numbers apply for packages soldered directly onto a PC Board. Note 4: Boldface limits apply to temperature range of -40C to 125C Note 5: Voltage average drift is determined by dividing the change in VOS by temperature change. Note 6: Do not short circuit the output. Continuous source or sink currents larger than the IOUT typical are not recommended as they may damage the part. Note 7: 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 guaranteed on shipped production material. Note 8: Limits are 100% production tested at 25C. Limits over the operating temperature range are guaranteed through correlations using the Statistical Quality Control (SQC) method. Note 9: This parameter is guaranteed by design and/or characterization and is not tested in production. Connection Diagrams 6-Pin TSOT23 8-Pin SOIC 30033601 Top View 30033678 Top View Ordering Information Package Part Number 6-Pin TSOT23 LMH6611MKE Package Marking Transport Media AX4A 250 Units Tape and Reel LMH6611MK 1k Units Tape and Reel LMH6611MKX 8-Pin SOIC www.national.com LMH6612MA LMH6612MAX NSC Drawing MK06A 3k Units Tape and Reel 95 Rail/Units LMH6612MA 2.5k Units Tape and Reel 8 M08A At TJ = 25C, AV = +1 (RF = 0), otherwise RF = 560 for Closed Loop Frequency Response for Various Supplies Closed Loop Frequency Response for Various Supplies 30033624 30033625 Closed Loop Frequency Response for Various Supplies Closed Loop Frequency Response for Various Supplies (Gain = +2) 30033604 30033605 Closed Loop Gain vs. Frequency for Various Temperatures Closed Loop Gain vs. Frequency for Various Temperatures 30033654 30033655 9 www.national.com LMH6611/LMH6612 Typical Performance Characteristics AV +1, unless otherwise specified. LMH6611/LMH6612 Closed Loop Gain vs. Frequency for Various Gains Large Signal Frequency Response 30033630 30033623 Large Signal Frequency Response 0.1 dB Gain Flatness for Various Supplies 30033626 30033631 0.1 dB Gain Flatness for Various Supplies 0.1 dB Gain Flatness for Various Supplies 30033606 30033627 www.national.com 10 0.1 dB Gain Flatness for Various Supplies (Gain = +2) 30033675 30033607 Small Signal Frequency Response with Various Capacitive Load Small Signal Frequency Response with Capacitive Load and Various RISO 30033608 30033609 HD2 and HD3 vs. Frequency and Supply Voltage HD2 and HD3 vs. Frequency and Load 30033653 30033650 11 www.national.com LMH6611/LMH6612 0.1 dB Gain Flatness for Various Supplies LMH6611/LMH6612 HD2 and HD3 vs. Common Mode Voltage HD2 and HD3 vs. Common Mode Voltage 30033677 30033681 HD2 vs. Frequency and Gain HD3 vs. Frequency and Gain 30033651 30033652 Open Loop Gain and Phase HD2 vs. Output Swing 30033682 30033676 www.national.com 12 LMH6611/LMH6612 HD3 vs. Output Swing HD2 vs. Output Swing 30033683 30033693 HD2 vs. Output Swing HD3 vs. Output Swing 30033694 30033684 HD3 vs. Output Swing Settling Time vs. Input Step Amplitude 30033686 30033685 13 www.national.com LMH6611/LMH6612 Settling Time vs. Input Step Amplitude Input Noise vs. Frequency 30033687 30033674 VOS vs. VOUT VOS vs. VOUT 30033661 30033668 VOS vs. VCM VOS vs. VS 30033660 www.national.com 30033658 14 LMH6611/LMH6612 VOS vs. IOUT VOS Distribution 30033669 30033672 IB vs. VS IS vs. VS 30033657 30033659 VOUT vs. VS VOUT vs. VS 30033690 30033691 15 www.national.com LMH6611/LMH6612 VOUT vs. VS Closed Loop Output Impedance vs. Frequency AV = +1 30033696 30033671 Circuit for Positive (+) PSRR Measurement +PSRR vs. Frequency 30033688 30033633 Circuit for Negative (-) PSRR Measurement -PSRR vs. Frequency 30033689 30033634 www.national.com 16 LMH6611/LMH6612 CMRR vs. Frequency Crosstalk vs. Frequency 30033632 30033697 Small Signal Step Response Small Signal Step Response 30033610 30033611 Small Signal Step Response Small Signal Step Response 30033612 30033614 17 www.national.com LMH6611/LMH6612 Small Signal Step Response Small Signal Step Response 30033615 30033616 Small Signal Step Response Small Signal Step Response 30033617 30033618 Small Signal Step Response Large Signal Step Response 30033619 www.national.com 30033613 18 LMH6611/LMH6612 Large Signal Step Response Overload Recovery Response 30033620 30033621 IS vs. VDISABLE 30033656 19 www.national.com LMH6611/LMH6612 Application Information The LMH6611 and LMH6612 are based on National Semiconductor's proprietary VIP10 dielectrically isolated bipolar process. This device family architecture features the following: * Complimentary bipolar devices with exceptionally high ft (8 GHz) even under low supply voltage (2.7V) and low bias current. * Common emitter push-push output stage. This architecture allows the output to reach within millivolts of either supply rail. * Consistent performance with little variation from any supply voltage (2.7V - 11V) for the most important specifications (e.g. BW, SR, IOUT.) * Significant power saving compared to competitive devices on the market with similar performance. With 3V supplies and a common mode input voltage range that extends beyond either supply rail, the LMH6611 is well suited to many low voltage/low power applications. Even with 3V supplies, the -3 dB BW (at AV = +1) is typically 305 MHz. The LMH6611 and LMH6612 are designed to avoid output phase reversal. With input overdrive, the output is kept near the supply rail (or as close to it as mandated by the closed loop gain setting and the input voltage). Figure 1 shows the input and output voltage when the input voltage significantly exceeds the supply voltages. 30033639 FIGURE 2. Input Equivalent Circuit During Shutdown When the LMH6611 is shutdown, there may be current flow through the internal diodes shown, caused by input potential, if present. This current may flow through the external feedback resistor and result in an apparent output signal. In most shutdown applications the presence of this output is inconsequential. However, if the output is "forced" by another device, the other device will need to conduct the current described in order to maintain the output potential. To keep the output at or near ground during shutdown when there is no other device to hold the output low, a switch using a transistor can be used to shunt the output to ground. SELECTION OF RF AND EFFECT ON STABILITY AND PEAKING The peaking of the LMH6611 depends on the value of the RF. From the graph shown in Figure 3, as the RF value increases, the peaking increases. For AV = 2, at RF = 1 k, the -3 dB bandwidth is 113 MHz and peaking is about 0.6 dB whereas at RF = 665, the -3 dB bandwidth is about 110 MHz and peaking is 0 dB. RF and the input capacitance form a pole in the amplifier's response. If the time constant is too big, it will cause peaking and ringing. Except for AV = 1 when RF should be 0, across all other gain settings it is recommended that RF remain between 500 and 1 k to ensure optimum performance. 30033622 FIGURE 1. Input and Output Shown with CMVR Exceeded If the input voltage range is exceeded by more than a diode drop beyond either rail, the internal ESD protection diodes will start to conduct. The current flow in these ESD diodes should be externally limited. SHUTDOWN CAPABILITY AND TURN ON/OFF BEHAVIOR The LMH6611 can be shutdown by connecting the DISABLE pin to a voltage 0.5V below the supply midpoint which will reduce the supply current to typically 120 A. The DISABLE pin is "active low" and can be connected through a resistor to V+ or left floating for normal operation. Shutdown is guaranteed when the DISABLE pin is 0.5V below the supply midpoint at any operating supply voltage and temperature. Typical turn on time is 20 ns and the turn off time is 60 ns. In the shutdown mode, essentially all internal device biasing is turned off in order to minimize supply current flow and the output goes into high impedance mode. During shutdown, the input stage has an equivalent circuit as shown in Figure 2. www.national.com 30033692 FIGURE 3. Closed Loop Gain vs. Frequency and RF = RG 20 f -3 dB (MHz) 665 110 0 1000 113 0.6 quired to drive the input of the ADC. To minimize the droop in the input voltage, external shunt capacitance (CL) should be about ten times larger than the internal input capacitance of the ADC and external series resistance (RL) should be large enough to maintain the phase delay at the output of the op amp and hence maintain the stability (See Figure 4) . Most applications benefit from the inclusion of a series isolation resistor connected between the op amp output and ADC input. This series resistor helps to limit the output current of the op amp. The value chosen for this series resistor is very important, as a higher value will increase the load impedance seen by the op amp and improve the total harmonic distortion (THD) performance of the op amp; however, the ADC prefers a low impedance source driving it. Thus, the optimum value for this series resistor must be found so that it will offer the best performance in terms of THD, SNR and SFDR of the combined op amp and ADC. Peaking (dB) MINIMIZING NOISE and an input curWith a low input voltage noise of 10 nV/ rent noise of 2 pA the LMH6611 and LMH6612 are suitable for high accuracy applications. Still being able to reduce the frequency band of operation of the various noise sources (i.e. op amp noise voltage, resistor thermal noise, input noise current) can further improve the noise performance of a system. In a non-inverting amplifier configuration inserting a capacitor, CG, in series with the gain setting resistor, RG, will reduce the gain of the circuit below frequency, f = 1/2RGCG. This can be set to reduce the contribution of noise from the 1/f region. Alternatively applying a feedback capacitor, CF, in parallel with the feedback resistor, RF, will introduce a pole into your system at f = 1/2RFCF and create a low pass filter. This filter can be set to reduce high frequency noise and harmonics. Finally remember to keep resistor values as small as possible for a given application in order to reduce resistor thermal noise. Important Specifications of Op Amp and ADC When interfacing an ADC with an op amp it is imperative to understand the specifications that are important to get the expected performance results. Modern ADC AC specifications such as THD, SNR, settling time and SFDR are critical for filtering, test and measurement, video and reconstruction applications. The high performance op amp's settling time, THD, and noise performance must be better than that of the ADC it is driving to maintain the proper system accuracy with minimal or no error. Some system applications require low THD, low SFDR and wide dynamic range (SNR), whereas some system applications require high SNR and they may sacrifice THD and SFDR to focus on the noise performance. Noise is a very important specification for both the op amp and the ADC. There are three main sources of noise that contribute to the overall performance of the ADC: Quantization noise, noise generated by the ADC itself (particularly at higher frequencies) and the noise generated by the application circuit. The impedance of the input source affects the noise performance of the op amp. Theoretically, an ADC's signal to noise ratio (SNR) can be found from the equation: POWER SUPPLY BYPASS Since the LMH6611 and LMH6612 are wide bandwidth amplifiers, proper power supply bypassing is critical for optimum performance. Improper power supply bypassing can result in large overshoot, ringing or oscillation. 0.1 F capacitors should be connected from the supply pins, V+ and V-, to ground, as close to the device as is practical. Additionally, a 10 F electrolytic capacitor should be connected from both supply pins to ground reasonably close to the device. Finally, near the device a 0.1 F ceramic capacitor between the supplies will provide the best harmonic distortion performance. INTERFACING HIGH PERFORMANCE OP AMPS WITH ADCs These amplifiers are designed for ease of use in a wide range of applications requiring high speed, low supply current, low noise, and the ability to drive complex ADC and video loads. The source that drives the modern high resolution analog-todigital converters (ADCs) sees a high frequency AC load and a DC load of a few hundred ohms or more. Thus, a high performance op amp with high input impedance of a few mega ohms and low output impedance would be an ideal choice as an input ADC driver. The LMH6611/LMH6612 have the low output impedance of 0.07 at f = 1 MHz. The ADC driver acts as a buffer and a low pass filter to reduce the overall system noise. To utilize the full dynamic range of the ADC, the ADC input has to be driven to full scale input voltage. As signals travel through the traces of a printed circuit board (PCB) and long cables, system noise accumulates in the signals and a differential ADC rejects any signals noise that appears as a common mode voltage. There are a couple of advantages to using differential signals rather than singleended signals. First, differential signals double the dynamic range of the ADC and second, they offer better harmonic distortion performance. There are several ways to produce differential signals from a dual op amp configuration. One method is to utilize the single-ended to differential conversion technique and the other is the differential to differential conversion technique. The first method requires a single input source and the second method requires differential input source. A real world input source can have non-ideal impedance thus the buffer amplifier, with very low output impedance, is re- SNR (in dB) = 6.02*N+1.72 where N is the resolution of the ADC. For example, according to this equation a 12-bit ADC has an SNR of 74 dB. However, the practical SNR number would be about 72 dB. In order to achieve better SNR, the ADC driver noise should be as small as possible. The LMH6611/LMH6612 have the low voltage noise of only 10 nV/ . The combined settling time of the op amp and the ADC must be within 1 LSB. The 0.01% settling time of the LMH6611/ LMH6612 is 100 ns. The ADC driver's THD should be inherently lower than that of the ADC. The LMH6611/LMH6612 have an SFDR of 96 dBc at 2 VPP output and 1 MHz input frequency. Signal to Noise and Distortion (SINAD) is a parameter which is the combination of the SNR and THD specifications. SINAD is defined as the RMS value of the output signal to the RMS value of all of the other spectral components below half the clock frequency, including harmonics but excluding DC. It can be calculated from SNR and THD according to the equation: 21 www.national.com LMH6611/LMH6612 RF = RG LMH6611/LMH6612 uration is preferred over the non-inverting configuration, as it offers more linear output response. Table 1 shows the performance data of the LMH6611 combined with the ADC121S101. The ADC driver's cutoff frequency of 500 kHz is found from the equation: Because SINAD compares all undesired frequency components with the input frequency, it is an overall measure of an ADC's dynamic performance. The following sections will discuss the three different ADC driver architectures in detail. SINGLE TO SINGLE ADC DRIVER This architecture has a single-ended input source connected to the input of the op amp and the single-ended output of the op amp is then fed to the single-ended input of the ADC. The low noise of only 10 nV/ and a wide bandwidth of 345 MHz make the LMH6611 an excellent choice for driving the 12-bit ADC121S101 500 KSPS to 1 MSPS ADC, which has a successive approximation architecture with internal sample and hold circuits. Figure 2 shows the schematic of the LMH6611 in a 2nd order multiple-feedback with gain of -1 (inverting) configuration, driving an ADC121S101. The inverting config- The op amp's gain is set by the equation: 30033629 FIGURE 4. Single to Single ADC Driver TABLE 1. Performance of the LMH6611 Combined with the ADC121S101 Amplifier Output/ADC Input SINAD SNR THD SFDR (dB) 4 70.2 (dB) (dB) (dBc) 71.6 -75.7 77.6 * * When the op amp and the ADC are using the same supply, it is important that both devices are well bypassed. A 0.1 F ceramic capacitor and a 10 F tantalum capacitor should be located as close as possible to each supply pin. A sample layout is shown in Figure 5. The 0.1 F capacitors (C13 and C6) and the 10 F capacitors (C11 and C5) are located very close to the supply pins of the LMH6611 and the ADC121S101. The following are recommendations for the design of PCB layout in order to obtain the optimum high frequency performance: www.national.com * * * 22 ENOB Notes 11.4 ADC121S101 @ f = 200 kHz Place ADC and amplifier as close together as possible. Put the supply bypassing capacitors as close as possible to the device (<1"). Utilize surface mount instead of through-hole components and ground and power planes. Keep the traces short where possible. Use terminated transmission lines for long traces. LMH6611/LMH6612 30033640 FIGURE 5. LMH6611 and ADC121S101 Layout up at the non-inverting inputs of both op amps U1 and U2. This configuration produces differential 2.5 VPP output signals, when the single-ended input signal of 0 to VREF is AC coupled into the non-inverting terminal of the op amp and each non-inverting terminal of the op amp is biased at the midscale of 2.5V. The two output RC anti-aliasing filters are used between both the outputs of U1 and U2 and the input of the ADC121S625 to minimize the effect of undesired high frequency noise coming from the input source. Each RC filter has the cutoff frequency of approximately 22 MHz. SINGLE-ENDED TO DIFFERENTIAL ADC DRIVER The single-ended to differential ADC driver in Figure 3 utilizes an LMH6612 dual op amp to buffer a single-ended source to drive an ADC with differential inputs. One of the op amps is configured as a unity gain buffer that drives the inverting (IN-) input of the op amp U2 and non-inverting (IN+) input of the ADC121S625. U2 inverts the input signal and drives the inverting input of the ADC121S625. The ADC driver is configured for a gain of +2 to reduce the noise without sacrificing THD performance. The common mode voltage of 2.5V is set 30033680 FIGURE 6. Single-Ended to Differential ADC Driver 23 www.national.com LMH6611/LMH6612 The performance of the LMH6612 with the ADC121S625 is shown in Table 2. TABLE 2. Performance of the LMH6612 Combined with the ADC121S625 Amplifier Output/ADC Input SINAD SNR THD SFDR (dB) (dB) (dB) (dBc) 2.5 68.8 69 -81.5 75.1 ENOB Notes 11.2 ADC121S625 @ f = 20 kHz single ADC drivers. Each output from these drivers goes to a separate input of the differential ADC. Here, each single to single ADC driver uses the same components and is configured for a gain of -1 (inverting). DIFFERENTIAL TO DIFFERENTIAL ADC DRIVER The LMH6612 dual op amp can be configured as a differential to differential ADC driver to buffer a differential source to a differential input ADC as shown in Figure 7. The differential to differential ADC driver can be formed using two single to 30033642 FIGURE 7. Differential to Differential ADC Driver www.national.com 24 ADC, the maximum input of 2.5 VPP is applied to the ADC input. Figure 8 shows the FFT plot of the LMH6612 and ADC121S625 combination tested at f = 20 kHz input frequency. TABLE 3. Performance of the LMH6612 Combined with the ADC121S625 Amplifier Output/ADC Input SINAD SNR THD SFDR (dB) (dB) (dB) (dBc) ENOB Notes 2.5 72.2 72.3 -87.7 92.1 11.7 ADC121S625 @ f = 20 kHz 2.5 72.2 72.2 -87.8 90.8 11.7 ADC121S625 @ f = 200 kHz 30033673 FIGURE 8. The FFT Plot of Differential to Differential ADC Driver 25 www.national.com LMH6611/LMH6612 The following table summarizes the performance of the LMH6612 combined with the ADC121S625 at two different frequencies. In order to utilize the full dynamic range of the LMH6611/LMH6612 DC LEVEL SHIFTING Often a signal must be both amplified and level shifted while using a single supply for the op amp. The circuit in Figure 9 can do both of these tasks. The procedure for specifying the resistor values is as follows. 1. Determine the input voltage. 2. Calculate the input voltage midpoint, VINMID = VINMIN + (VINMAX - VINMIN)/2. 3. Determine the output voltage needed. 4. Calculate the output voltage midpoint, VOUTMID = VOUTMIN + (VOUTMAX - VOUTMIN)/2. 5. Calculate the gain needed, gain = (VOUTMAX - VOUTMIN)/ (VINMAX - VINMIN) 6. Calculate the amount the voltage needs to be shifted from input to output, VOUT = VOUTMID - gain x VINMID. 7. Set the supply voltage to be used. 8. Calculate the noise gain, noise gain = gain + VOUT/VS. 9. Set RF. 10. Calculate R1, R1 = RF/gain. 11. Calculate R2, R2 = RF/(noise gain-gain). 12. Calculate RG, RG= RF/(noise gain - 1). Check that both the VIN and VOUT are within the voltage ranges of the LMH6611. 30033648 FIGURE 9. DC Level Shifting The following example is for a VIN of 0V to 1V with a VOUT of 2V to 4V. 1. VIN = 0V to 1V 2. VINMID = 0V + (1V - 0V)/2 = 0.5V 3. VOUT = 2V to 4V 4. VOUTMID = 2V + (4V - 2V)/2 = 3V 5. Gain = (4V - 2V)/(1V - 0V) = 2 6. VOUT = 3V - 2 x 0.5V = 2 7. For the example the supply voltage will be +5V. 8. Noise gain = 2 + 2/5V = 2.4 9. RF = 2 k 10. R1 = 2 k/2 = 1 k 11. R2 = 2 k/(2.4-2) = 5 k 12. RG = 2 k/(2.4 - 1) = 1.43 k of +1 and a -3 dB point of 1 MHz. Values can be determined by using the WEBENCH(R) Active Filter Designer found at www.amplifiers.national.com. 4th ORDER MULTIPLE FEEDBACK LOW-PASS FILTER Figure 10 shows the LMH6612 used as the amplifier in a multiple feedback low pass filter. This filter is set up to have a gain 30033628 FIGURE 10. 4th Order Multiple Feedback Low-Pass Filter www.national.com 26 (1) (2) 30033665 30033641 FIGURE 13. Bode Plot of Noise Gain Intersecting with Op Amp Open Loop Gain FIGURE 11. Current Sense Amplifier TRANSIMPEDANCE AMPLIFIER By definition, a photodiode produces either a current or voltage output from exposure to a light source. A Transimpedance Amplifier (TIA) is utilized to convert this low-level current to a usable voltage signal. The TIA often will need to be compensated to insure proper operation. Figure 13 shows the bode plot of the noise gain intersecting the op amp open loop gain. With larger values of gain, CT and RF create a zero in the transfer function. At higher frequencies the circuit can become unstable due to excess phase shift around the loop. A pole at fP in the noise gain function is created by placing a feedback capacitor (CF) across RF. The noise gain slope is flattened by choosing an appropriate value of CF for optimum performance. Theoretical expressions for calculating the optimum value of CF and the expected -3 dB bandwidth are: (3) (4) Equation 4 indicates that the -3 dB bandwidth of the TIA is inversely proportional to the feedback resistor. Therefore, if the bandwidth is important then the best approach would be to have a moderate transimpedance gain stage followed by a broadband voltage gain stage. Table 4 shows the measurement results of the LMH6611 with different photodiodes having various capacitances (CPD) and a feedback resistance (RF) of 1 k. 30033662 FIGURE 12. Photodiode Modeled with Capacitance Elements Figure 12 shows the LMH6611 modeled with photodiode and the internal op amp capacitances. The LMH6611 allows circuit operation of a low intensity light due to its low input bias 27 www.national.com LMH6611/LMH6612 current by using larger values of gain (RF). The total capacitance (CT) on the inverting terminal of the op amp includes the photodiode capacitance (C PD) and the input capacitance of the op amp (CIN). This total capacitance (CT) plays an important role in the stability of the circuit. The noise gain of this circuit determines the stability and is defined by: CURRENT SENSE AMPLIFIER AND OPTIMIZING ACCURACY IN PRECESION APPLICATIONS With it's rail-to-rail output capability, low VOS, and low IB the LMH6611 is an ideal choice for a current sense amplifier application. Figure 11 shows the schematic of the LMH6611 set up in a low-side sense configuration which provides a conversion gain of 2V/A. Voltage error due to VOS can be calculated to be VOS x (1 + RF/RG) or 0.6 mV x 21 = 12.6 mV. Voltage error due to IO is I O x R F or 0.5 A x 1 k = 0.5 mV. Hence worst case total voltage error is 12.6 mV + 0.5 mV or 13.1 mV which translates into a current error of 13.1 mV/(2 V/ A) = 6.55 mA. This circuit employs DC source resistance matching at the two input terminals in order to minimize the output DC error caused by input bias current. Another technique to reduce output offset in a non-inverting amplifier configuration is to introduce a DC offset current into the inverting input of the amplifier. To ensure minimal impact on frequency response be sure to inject the DC offset current through large resistors. Conversely if optimizing an inverting amplifier configuration simply apply offset adjustment to the non-inverting input. LMH6611/LMH6612 TABLE 4. TIA (Figure 1) Compensation and Performance Results CPD CT CF CAL CF USED f -3 dB CAL f -3 dB MEAS Peaking (pF) 22 (pF) (pF) (pF) (MHz) (MHz) (dB) 24 5.42 5.6 29.3 27.1 0.5 47 49 7.75 8 20.5 21 0.5 100 102 11.15 12 14.2 15.2 0.5 222 224 20.39 18 9.6 10.7 0.5 330 332 20.2 22 7.9 9 0.8 Note: GBWP = 130 MHz CT = CPD + CIN CIN = 2 pF VS = 2.5V Figure 14 shows the frequency response for the various photodiodes in Table 4. noise voltage, feedback resistor thermal noise, input noise current, photodiode noise current) do not all operate over the same frequency band. Therefore, when the noise at the output is calculated, this should be taken into account. The op amp noise voltage will be gained up in the region between the noise gain's zero and pole (fZ and fP in Figure 13). The higher the values of RF and CT, the sooner the noise gain peaking starts and therefore its contribution to the total output noise will be larger. It is advantageous to minimize CIN by proper choice of op amp or by applying a reverse bias across the diode but this will be at the expense of excess dark current and noise. EVALUATION BOARD National Semiconductor provides the following evaluation board as a guide for high frequency layout and as an aid in device testing and characterization. Many of the datasheet plots were measured with this board: Device LMH6611MK 30033635 Board Part # LMH730216 This evaluation board can be shipped when a device sample request is placed with National Semiconductor. FIGURE 14. Frequency Response for Various Photodiode and Feedback Capacitors When analyzing the noise at the output of the TIA, it is important to note that the various noise sources (i.e. op amp www.national.com Package TSOT23 28 LMH6611/LMH6612 Physical Dimensions inches (millimeters) unless otherwise noted 6-Pin TSOT23 NS Package Number MK06A 8-Pin SOIC NS Package Number M08A 29 www.national.com LMH6611/LMH6612 Single Supply 345 MHz Rail-to-Rail Output Amplifiers For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Design Support Amplifiers www.national.com/amplifiers WEBENCH(R) Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage References www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Applications & Markets www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise(R) Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagicTM www.national.com/solarmagic PLL/VCO www.national.com/wireless www.national.com/training PowerWise(R) Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION ("NATIONAL") PRODUCTS. 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