LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Low Power, 130MHz, 75mA Rail-to-Rail Output Amplifiers General Description The LMH664XEP family true single supply voltage feedback amplifiers offer high speed (130MHz), low distortion (-62dBc), and exceptionally high output current (approximately 75mA) at low cost and with reduced power consumption when compared against existing devices with similar performance. Input common mode voltage range extends to 0.5V below V- and 1V from V+. Output voltage range extends to within 40mV of either supply rail, allowing wide dynamic range especially desirable in low voltage applications. The output stage is capable of approximately 75mA in order to drive heavy loads. Fast output Slew Rate (130V/s) ensures large peak-to-peak output swings can be maintained even at higher speeds, resulting in exceptional full power bandwidth of 40MHz with a 3V supply. These characteristics, along with low cost, are ideal features for a multitude of industrial and commercial applications. Careful attention has been paid to ensure device stability under all operating voltages and modes. The result is a very well behaved frequency response characteristic (0.1dB gain flatness up the 12MHz under 150 load and AV = +2) with minimal peaking (typically 2dB maximum) for any gain setting and under both heavy and light loads. This along with fast settling time (68ns) and low distortion allows the device to operate well in ADC buffer, and high frequency filter applications as well as other applications. This device family offers professional quality video performance with low DG (0.01%) and DP (0.01) characteristics. Differential Gain and Differential Phase characteristics are also well maintained under heavy loads (150) and throughout the output voltage range. The LMH664XEP family is offered in single (LMH6642EP), dual (LMH6643EP), and quad (LMH6644EP) options. See ordering information for packages offered. ENHANCED PLASTIC * Extended Temperature Performance of -40C to +85C * * * * * Baseline Control - Single Fab & Assembly Site Process Change Notification (PCN) Qualification & Reliability Data Solder (PbSn) Lead Finish is standard Enhanced Diminishing Manufacturing Sources (DMS) Support Features (VS = 5V, TA = 25C, RL = 2k, AV = +1. Typical values unless specified). n -3dB BW (AV = +1) 130MHz n Supply voltage range 2.7V to 12.8V n Slew rate (Note 11), (AV = -1) 130V/s n Supply current (no load) 2.7mA/amp n Output short circuit current +115mA/-145mA 75mA n Linear output current n Input common mode volt. 0.5V beyond V-, 1V from V+ n Output voltage swing 40mV from rails n Input voltage noise (100kHz) 17nV/ n Input current noise (100kHz) 0.9pA/ n THD (5MHz, RL = 2k, VO = 2VPP, AV = +2) -62dBc n Settling time 68ns n Fully characterized for 3V, 5V, and 5V n Overdrive recovery 100ns n Output short circuit protected (Note 14) n No output phase reversal with CMVR exceeded Applications n Selected Military Applications n Selected Avionics Applications Ordering Information PART NUMBER VID PART NUMBER NS PACKAGE NUMBER (Note 3) LMH6642MFXEP V62/04625-01 MF05A LMH6643MAXEP V62/04625-02 M08A LMH6644MAXEP V62/04625-03 M14A (Notes 1, 2) TBD TBD Note 1: For the following (Enhanced Plastic) versions, check for availability: LMH6642MAEP, LMH6642MAXEP, LMH6642MFEP, LMH6643MAEP, LMH6643MMEP, LMH6643MMXEP, LMH6644MAEP, LMH6644MTEP, LMH6644MTXEP. Parts listed with an "X" are provided in Tape & Reel and parts without an "X" are in Rails. Note 2: FOR ADDITIONAL ORDERING AND PRODUCT INFORMATION, PLEASE VISIT THE ENHANCED PLASTIC WEB SITE AT: www.national.com/ mil Note 3: Refer to package details under Physical Dimensions (c) 2004 National Semiconductor Corporation DS200894 www.national.com LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Low Power, 130MHz, 75mA Rail-to-Rail Output Amplifiers July 2004 LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Absolute Maximum Ratings (Note 4) Infrared or Convection Reflow(20 sec) 235C If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Wave Soldering Lead Temp.(10 sec) 260C ESD Tolerance Operating Ratings (Note 4) 2KV (Note 5) Supply Voltage (V+ - V-) 200V (Note 12) 2.5V VIN Differential Output Short Circuit Duration + SOT23-5 265C/W SOIC-8 190C/W 10mA MSOP-8 235C/W -65C to +150C SOIC-14 145C/W TSSOP-14 155C/W Supply Voltage (V - V ) 13.5V V+ +0.8V, V- -0.8V Input Current Storage Temperature Range -40C to +85C Package Thermal Resistance (Note 7) (JA) (Note 6), (Note 14) - Voltage at Input/Output pins 2.7V to 12.8V Junction Temperature Range (Note 7) Junction Temperature (Note 7) +150C Soldering Information 3V Electrical Characteristics Unless otherwise specified, all limits guaranteed for at TJ = 25C, V+ = 3V, V- = 0V, VCM = VO = V+/2, and RL = 2k to V+/2. Boldface limits apply at the temperature extremes. Symbol BW Parameter -3dB BW Conditions AV = +1, VOUT = 200mVPP Min (Note 9) Typ (Note 8) 80 115 19 MHz MHz AV = +2, RL = 150 to V+/2, RL = 402, VOUT = 200mVPP PBW Full Power Bandwidth AV = +1, -1dB, VOUT = 1VPP 40 en Input-Referred Voltage Noise f = 100kHz 17 f = 1kHz 48 f = 100kHz 0.90 f = 1kHz 3.3 THD Total Harmonic Distortion f = 5MHz, VO = 2VPP, AV = -1, RL = 100 to V+/2 -48 DG Differential Gain VCM = 1V, NTSC, AV = +2 RL =150 to V+/2 0.17 RL =1k to V /2 Differential Phase nV/ pA/ dBc % + DP MHz 46 0.1dB Gain Flatness Input-Referred Current Noise Units AV = +2, -1, VOUT = 200mVPP BW0.1dB in Max (Note 9) 0.03 0.05 VCM = 1V, NTSC, AV = +2 RL =150 to V+/2 deg RL =1k to V+/2 0.03 CT Rej. Cross-Talk Rejection f = 5MHz, Receiver: Rf = Rg = 510, AV = +2 47 dB TS Settling Time VO = 2VPP, 0.1%, 8pF Load, VS = 5V 68 ns SR Slew Rate (Note 11) AV = -1, VI = 2VPP VOS Input Offset Voltage TC VOS Input Offset Average Drift (Note 15) 5 IB Input Bias Current (Note 10) -1.50 -2.60 -3.25 A IOS Input Offset Current 20 800 1000 nA RIN Common Mode Input Resistance 3 M CIN Common Mode Input Capacitance 2 pF www.national.com 90 120 1 2 V/s 5 7 mV V/C (Continued) Unless otherwise specified, all limits guaranteed for at TJ = 25C, V+ = 3V, V- = 0V, VCM = VO = V+/2, and RL = 2k to V+/2. Boldface limits apply at the temperature extremes. Symbol CMVR Parameter Input Common-Mode Voltage Range Conditions Min (Note 9) CMRR 50dB Typ (Note 8) Max (Note 9) -0.5 -0.2 -0.1 1.8 1.6 2.0 CMRR Common Mode Rejection Ratio VCM Stepped from 0V to 1.5V 72 95 AVOL Large Signal Voltage Gain VO = 0.5V to 2.5V RL = 2k to V+/2 80 75 96 VO = 0.5V to 2.5V RL = 150 to V+/2 74 70 82 RL = 2k to V+/2, VID = 200mV 2.90 2.98 RL = 150 to V+/2, VID = 200mV 2.80 2.93 VO ISC Output Swing High dB V RL = 2k to V+/2, VID = -200mV 25 75 + 75 150 Output Short Circuit Current Sourcing to V+/2 VID = 200mV (Note 13) 50 35 95 Sinking to V+/2 VID = -200mV (Note 13) 55 40 110 IOUT Output Current VOUT = 0.5V from either supply +PSRR Positive Power Supply Rejection Ratio V+ = 3.0V to 3.5V, VCM = 1.5V IS Supply Current (per channel) No Load 75 V dB Output Swing Low RL = 150 to V /2, VID = -200mV Units mV mA 65 mA 85 dB 2.70 4.00 4.50 mA 5V Electrical Characteristics Unless otherwise specified, all limits guaranteed for at TJ = 25C, V+ = 5V, V- = 0V, VCM = VO = V+/2, and RL = 2k to V+/2. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions BW -3dB BW AV = +1, VOUT = 200mVPP Min (Note 9) Typ (Note 8) 90 120 15 MHz MHz AV = +2, RL = 150 to V+/2, Rf = 402, VOUT = 200mVPP PBW Full Power Bandwidth AV = +1, -1dB, VOUT = 2VPP 22 en Input-Referred Voltage Noise f = 100kHz 17 f = 1kHz 48 f = 100kHz 0.90 f = 1kHz 3.3 THD Total Harmonic Distortion f = 5MHz, VO = 2VPP, AV = +2 -60 DG Differential Gain NTSC, AV = +2 RL =150 to V+/2 0.16 RL =1k to V+/2 0.05 NTSC, AV = +2 RL =150 to V+/2 0.05 DP Differential Phase MHz 46 0.1dB Gain Flatness Input-Referred Current Noise Units AV = +2, -1, VOUT = 200mVPP BW0.1dB in Max (Note 9) + RL =1k to V /2 nV/ pA/ dBc % deg 0.01 CT Rej. Cross-Talk Rejection f = 5MHz, Receiver: Rf = Rg = 510, AV = +2 47 dB TS Settling Time VO = 2VPP, 0.1%, 8pF Load 68 ns 3 www.national.com LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic 3V Electrical Characteristics LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic 5V Electrical Characteristics (Continued) Unless otherwise specified, all limits guaranteed for at TJ = 25C, V+ = 5V, V- = 0V, VCM = VO = V+/2, and RL = 2k to V+/2. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions SR Slew Rate (Note 11) AV = -1, VI = 2VPP VOS Input Offset Voltage Min (Note 9) Typ (Note 8) 95 125 1 Input Offset Average Drift (Note 15) Input Bias Current (Note 10) IOS Input Offset Current RIN Common Mode Input Resistance 3 CIN Common Mode Input Capacitance 2 CMVR Input Common-Mode Voltage Range CMRR 50dB V/C A 20 800 1000 nA -0.5 3.8 3.6 4.0 72 95 VCM Stepped from 0V to 3.5V AVOL Large Signal Voltage Gain VO = 0.5V to 4.50V RL = 2k to V+/2 86 82 98 VO = 0.5V to 4.25V RL = 150 to V+/2 76 72 82 RL = 2k to V+/2, VID = 200mV 4.90 4.98 RL = 150 to V+/2, VID = 200mV 4.65 4.90 M pF -0.2 -0.1 dB V RL = 2k to V+/2, VID = -200mV 25 100 + 100 150 Output Short Circuit Current Sourcing to V+/2 VID = 200mV (Note 13) 55 40 115 Sinking to V+/2 VID = -200mV (Note 13) 70 55 140 IOUT Output Current VO = 0.5V from either supply +PSRR Positive Power Supply Rejection Ratio V+ = 4.0V to 6V IS Supply Current (per channel) No Load mV mA 70 79 V dB Output Swing Low RL = 150 to V /2, VID = -200mV mV -1.70 Common Mode Rejection Ratio ISC 5 7 -2.60 -3.25 CMRR Output Swing High Units V/s 5 TC VOS IB VO Max (Note 9) mA dB 90 2.70 4.25 5.00 mA 5V Electrical Characteristics Unless otherwise specified, all limits guaranteed for at TJ = 25C, V+ = 5V, V- = -5V, VCM = VO = 0V and RL = 2k to ground. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions BW -3dB BW AV = +1, VOUT = 200mVPP Min (Note 9) Typ (Note 8) 95 130 Units MHz AV = +2, -1, VOUT = 200mVPP 46 12 MHz MHz BW0.1dB 0.1dB Gain Flatness AV = +2, RL = 150 to V+/2, Rf = 806, VOUT = 200mVPP PBW Full Power Bandwidth AV = +1, -1dB, VOUT = 2VPP 24 en Input-Referred Voltage Noise f = 100kHz 17 f = 1kHz 48 www.national.com Max (Note 9) 4 nV/ (Continued) Unless otherwise specified, all limits guaranteed for at TJ = 25C, V+ = 5V, V- = -5V, VCM = VO = 0V and RL = 2k to ground. Boldface limits apply at the temperature extremes. Symbol Parameter Conditions Min (Note 9) Typ (Note 8) in Input-Referred Current Noise f = 100kHz 0.90 f = 1kHz 3.3 THD Total Harmonic Distortion f = 5MHz, VO = 2VPP, AV = +2 -62 DG Differential Gain NTSC, AV = +2 RL =150 to V+/2 0.15 + DP Differential Phase RL =1k to V /2 0.01 NTSC, AV = +2 RL =150 to V+/2 0.04 RL =1k to V+/2 0.01 CT Rej. Cross-Talk Rejection f = 5MHz, Receiver: Rf = Rg = 510, AV = +2 47 TS Settling Time VO = 2VPP, 0.1%, 8pF Load, VS = 5V 68 SR Slew Rate (Note 11) AV = -1, VI = 2VPP VOS Input Offset Voltage 100 1 Input Offset Average Drift (Note 15) Input Bias Current (Note 10) IOS Input Offset Current RIN Common Mode Input Resistance 3 CIN Common Mode Input Capacitance 2 CMVR Input Common-Mode Voltage Range deg dB ns V/s 5 7 CMRR 50dB V/C A 20 800 1000 nA -5.5 3.8 3.6 4.0 74 95 VCM Stepped from -5V to 3.5V AVOL Large Signal Voltage Gain VO = -4.5V to 4.5V, RL = 2k 88 84 96 VO = -4.0V to 4.0V, RL = 150 78 74 82 M pF -5.2 -5.1 dB RL = 2k, VID = 200mV 4.90 4.96 RL = 150, VID = 200mV 4.65 4.80 Output Swing Low RL = 2k, VID = -200mV -4.96 -4.90 RL = 150, VID = -200mV -4.80 -4.65 Output Short Circuit Current Sourcing to Ground VID = 200mV (Note 13) 60 35 115 Sinking to Ground VID = -200mV (Note 13) 85 65 145 VO = 0.5V from either supply + V Power Supply Rejection Ratio (V , V ) = (4.5V, -4.5V) to (5.5V, -5.5V) 75 IS Supply Current (per channel) No Load 78 mA dB 90 2.70 5 V mA - PSRR V dB Output Swing High Output Current mV -1.60 Common Mode Rejection Ratio IOUT % -2.60 -3.25 CMRR ISC dBc 5 TC VOS Units pA/ 135 IB VO Max (Note 9) 4.50 5.50 mA www.national.com LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic 5V Electrical Characteristics LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic 5V Electrical Characteristics (Continued) Note 4: 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 5: Human body model, 1.5k in series with 100pF. Note 6: Applies to both single-supply and split-supply operation. Continuous short circuit operation at elevated ambient temperature can result in exceeding the maximum allowed junction temperature of 150C. Note 7: The maximum power dissipation is a function of TJ(MAX), JA, and TA. 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 8: Typical values represent the most likely parametric norm. Note 9: All limits are guaranteed by testing or statistical analysis. Note 10: Positive current corresponds to current flowing into the device. Note 11: Slew rate is the average of the rising and falling slew rates. Note 12: Machine Model, 0 in series with 200pF. Note 13: Short circuit test is a momentary test. See Note 14. Note 14: Output short circuit duration is infinite for VS < 6V at room temperature and below. For VS > 6V, allowable short circuit duration is 1.5ms. Note 15: Offset voltage average drift determined by dividing the change in VOS at temperature extremes by the total temperature change. Connection Diagrams SOIC-8 and MSOP-8 (LMH6643) SOT23-5 (LMH6642) SOIC-8 (LMH6642) 20089461 Top View 20089462 Top View 20089463 Top View SOIC-14 and TSSOP-14 (LMH6644) 20089468 Top View www.national.com 6 At TJ = 25C, V+ = +5, V- = -5V, RF = RL = 2k. Unless oth- erwise specified. Closed Loop Frequency Response for Various Supplies Closed Loop Gain vs. Frequency for Various Gain 20089457 20089451 Closed Loop Frequency Response for Various Temperature Closed Loop Gain vs. Frequency for Various Gain 20089450 20089435 Closed Loop Frequency Response for Various Temperature Closed Loop Gain vs. Frequency for Various Supplies 20089448 20089434 7 www.national.com LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Typical Performance Characteristics LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Typical Performance Characteristics At TJ = 25C, V+ = +5, V- = -5V, RF = RL = 2k. Unless otherwise specified. (Continued) Closed Loop Small Signal Frequency Response for Various Supplies Large Signal Frequency Response 20089446 20089447 0.1dB Gain Flatness for Various Supplies Closed Loop Frequency Response for Various Supplies 20089444 20089445 VOUT (VPP) for THD < 0.5% VOUT (VPP) for THD < 0.5% 20089409 www.national.com 20089408 8 otherwise specified. (Continued) VOUT (VPP) for THD < 0.5% Open Loop Gain/Phase for Various Temperature 20089432 20089410 Open Loop Gain/Phase for Various Temperature HD2 (dBc) vs. Output Swing 20089433 20089414 HD3 (dBc) vs. Output Swing HD2 vs. Output Swing 20089404 20089415 9 www.national.com LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Typical Performance Characteristics At TJ = 25C, V+ = +5, V- = -5V, RF = RL = 2k. Unless LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Typical Performance Characteristics At TJ = 25C, V+ = +5, V- = -5V, RF = RL = 2k. Unless otherwise specified. (Continued) HD3 vs. Output Swing THD (dBc) vs. Output Swing 20089405 20089406 Settling Time vs. Input Step Amplitude (Output Slew and Settle Time) Input Noise vs. Frequency 20089412 20089413 + - VOUT from V vs. ISOURCE VOUT from V vs. ISINK 20089418 www.national.com 20089419 10 otherwise specified. (Continued) VOUT from V+ vs. ISOURCE VOUT from V- vs. ISINK 20089416 20089417 Swing vs. VS Short Circuit Current (to VS/2) vs. VS 20089429 20089431 Output Sinking Saturation Voltage vs. IOUT Output Sourcing Saturation Voltage vs. IOUT 20089420 20089401 11 www.national.com LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Typical Performance Characteristics At TJ = 25C, V+ = +5, V- = -5V, RF = RL = 2k. Unless LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Typical Performance Characteristics At TJ = 25C, V+ = +5, V- = -5V, RF = RL = 2k. Unless otherwise specified. (Continued) Closed Loop Output Impedance vs. Frequency AV = +1 PSRR vs. Frequency 20089402 20089403 Crosstalk Rejection vs. Frequency (Output to Output) CMRR vs. Frequency 20089407 20089411 VOS vs. VOUT (Typical Unit) VOS vs. VCM (Typical Unit) 20089427 20089430 www.national.com 12 otherwise specified. (Continued) VOS vs. VS (for 3 Representative Units) VOS vs. VS (for 3 Representative Units) 20089422 20089423 VOS vs. VS (for 3 Representative Units) IB vs. VS 20089425 20089424 IOS vs. VS IS vs. VCM 20089428 20089426 13 www.national.com LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Typical Performance Characteristics At TJ = 25C, V+ = +5, V- = -5V, RF = RL = 2k. Unless LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Typical Performance Characteristics At TJ = 25C, V+ = +5, V- = -5V, RF = RL = 2k. Unless otherwise specified. (Continued) IS vs. VS Small Signal Step Response 20089453 20089421 Large Signal Step Response Large Signal Step Response 20089441 20089439 Small Signal Step Response Small Signal Step Response 20089456 www.national.com 20089436 14 otherwise specified. (Continued) Small Signal Step Response Small Signal Step Response 20089452 20089438 Large Signal Step Response Large Signal Step Response 20089437 20089454 Large Signal Step Response 20089460 15 www.national.com LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Typical Performance Characteristics At TJ = 25C, V+ = +5, V- = -5V, RF = RL = 2k. Unless LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic This device family was designed to avoid output phase reversal. With input overdrive, the output is kept near supply rail (or as closed to it as mandated by the closed loop gain setting and the input voltage). See Figure 1: Application Notes CIRCUIT DESCRIPTION The LMH664XEP family is 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 (8GHz) even under low supply voltage (2.7V) and low bias current. * A class A-B "turn-around" stage with improved noise, offset, and reduced power dissipation compared to similar speed devices (patent pending). * Common Emitter push-push output stage capable of 75mA output current (at 0.5V from the supply rails) while consuming only 2.7mA of total supply current per channel. This architecture allows output to reach within millivolts of either supply rail. * Consistent performance from any supply voltage (3V10V) with little variation with supply voltage for the most important specifications (e.g. BW, SR, IOUT, etc.) * Significant power saving (40%) compared to competitive devices on the market with similar performance. 20089442 FIGURE 1. Input and Output Shown with CMVR Exceeded Application Hints This Op Amp family is a drop-in replacement for the AD805X family of high speed Op Amps in most applications. In addition, the LMH664XEP will typically save about 40% on power dissipation, due to lower supply current, when compared to competition. All AD805X family's guaranteed parameters are included in the list of LMH664XEP guaranteed specifications in order to ensure equal or better level of performance. However, as in most high performance parts, due to subtleties of applications, it is strongly recommended that the performance of the part to be evaluated is tested under actual operating conditions to ensure full compliance to all specifications. With 3V supplies and a common mode input voltage range that extends 0.5V below V-, the LMH664XEP find applications in low voltage/low power applications. Even with 3V supplies, the -3dB BW (@ AV = +1) is typically 115MHz with a tested limit of 80MHz. Production testing guarantees that process variations with not compromise speed. High frequency response is exceptionally stable confining the typical -3dB BW over the industrial temperature range to 2.5%. As can be seen from the typical performance plots, the LMH664XEP output current capability (75mA) is enhanced compared to AD805X. This enhancement, increases the output load range, adding to the LMH664XEP's versatility. Because of the LMH664XEP's high output current capability attention should be given to device junction temperature in order not to exceed the Absolute Maximum Rating. www.national.com However, if the input voltage range of -0.5V to 1V from V+ is exceeded by more than a diode drop, the internal ESD protection diodes will start to conduct.The current in the diodes should be kept at or below 10mA. Output overdrive recovery time is less than 100ns as can be seen from Figure 2 plot: 20089443 FIGURE 2. Overload Recovery Waveform 16 Amp input capacitance and Q1 equivalent collector capacitance together (CIN) will cause additional phase shift to the signal fed back to the inverting node. Cf will function as a zero in the feedback path counter-acting the effect of the CIN and acting to stabilized the circuit. By proper selection of Cf such that the Op Amp open loop gain is equal to the inverse of the feedback factor at that frequency, the response is optimized with a theoretical 45 phase margin. (Continued) SINGLE SUPPLY, LOW POWER PHOTODIODE AMPLIFIER The circuit shown in Figure 3 is used to amplify the current from a photo-diode into a voltage output. In this circuit, the emphasis is on achieving high bandwidth and the transimpedance gain setting is kept relatively low. Because of its high slew rate limit and high speed, the LMH664XEP family lends itself well to such an application. This circuit achieves approximately 1V/mA of transimpedance gain and capable of handling up to 1mApp from the photodiode. Q1, in a common base configuration, isolates the high capacitance of the photodiode (Cd) from the Op Amp input in order to maximize speed. Input is AC coupled through C1 to ease biasing and allow single supply operation. With 5V single supply, the device input/output is shifted to near half supply using a voltage divider from VCC. Note that Q1 collector does not have any voltage swing and the Miller effect is minimized. D1, tied to Q1 base, is for temperature compensation of Q1's bias point. Q1 collector current was set to be large enough to handle the peak-to-peak photodiode excitation and not too large to shift the U1 output too far from mid-supply. No matter how low an Rf is selected, there is a need for Cf in order to stabilize the circuit. The reason for this is that the Op (1) where GBWP is the Gain Bandwidth Product of the Op Amp Optimized as such, the I-V converter will have a theoretical pole, fp, at: (2) With Op Amp input capacitance of 3pF and an estimate for Q1 output capacitance of about 3pF as well, CIN = 6pF. From the typical performance plots, LMH6642EP/6643EP family GBWP is approximately 57MHz. Therefore, with Rf = 1k, from Equation 1 and 2 above. Cf = 4.1pF, and fp = 39MHz 20089464 FIGURE 3. Single Supply Photodiode I-V Converter 17 www.national.com LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Application Notes LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Application Notes output pins. Parasitic capacitances on these nodes to ground will cause frequency response peaking and possible circuit oscillations (see Application Note OA-15 for more information). National Semiconductor suggests the following evaluation boards as a guide for high frequency layout and as an aid in device testing and characterization: (Continued) For this example, optimum Cf was empirically determined to be around 5pF. This time domain response is shown in Figure 4 below showing about 9ns rise/fall times, corresponding to about 39MHz for fp. The overall supply current from the +5V supply is around 5mA with no load. Device Package Evaluation Board PN LMH6642MF SOT23-5 CLC730068 CLC730027 LMH6642MF 8-Pin SOIC LMH6643MA 8-Pin SOIC CLC730036 LMH6643MA 8-Pin MSOP CLC730123 LMH6644MA 14-Pin SOIC CLC730031 LMH6644MA 14-Pin TSSOP CLC730131 These free evaluation boards are shipped when a device sample request is placed with National Semiconductor. Another important parameter in working with high speed/ high performance amplifiers, is the component values selection. Choosing external resistors that are large in value will effect the closed loop behavior of the stage because of the interaction of these resistors with parasitic capacitances. These capacitors could be inherent to the device or a byproduct of the board layout and component placement. Either way, keeping the resistor values lower, will diminish this interaction to a large extent. On the other hand, choosing very low value resistors could load down nodes and will contribute to higher overall power dissipation. 20089465 FIGURE 4. Converter Step Response (1VPP, 20 ns/DIV) PRINTED CIRCUIT BOARD LAYOUT AND COMPONENT VALUES SECTIONS Generally, a good high frequency layout will keep power supply and ground traces away from the inverting input and www.national.com 18 LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Physical Dimensions inches (millimeters) unless otherwise noted 5-Pin SOT23 NS Package Number MF05A 8-Pin SOIC NS Package Number M08A 19 www.national.com LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Physical Dimensions inches (millimeters) unless otherwise noted (Continued) 8-Pin MSOP NS Package Number MUA08A 14-Pin SOIC NS Package Number M14A www.national.com 20 inches (millimeters) unless otherwise noted (Continued) 14-Pin TSSOP NS Package Number MTC14 LIFE SUPPORT POLICY NATIONAL'S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant into the body, or (b) support or sustain life, and whose failure to perform when properly used in accordance with instructions for use provided in the labeling, can be reasonably expected to result in a significant injury to the user. 2. A critical component is any component of a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system, or to affect its safety or effectiveness. BANNED SUBSTANCE COMPLIANCE National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ``Banned Substances'' as defined in CSP-9-111S2. National Semiconductor Americas Customer Support Center Email: new.feedback@nsc.com Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Customer Support Center Fax: +49 (0) 180-530 85 86 Email: europe.support@nsc.com Deutsch Tel: +49 (0) 69 9508 6208 English Tel: +44 (0) 870 24 0 2171 Francais Tel: +33 (0) 1 41 91 8790 National Semiconductor Asia Pacific Customer Support Center Email: ap.support@nsc.com National Semiconductor Japan Customer Support Center Fax: 81-3-5639-7507 Email: jpn.feedback@nsc.com Tel: 81-3-5639-7560 National does not assume any responsibility for use of any circuitry described, no circuit patent licenses are implied and National reserves the right at any time without notice to change said circuitry and specifications. LMH6642EP/LMH6643EP/LMH6644EP Enhanced Plastic Low Power, 130MHz, 75mA Rail-to-Rail Output Amplifiers Physical Dimensions