www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 FEATURES D Unity Gain Stability D Low Voltage Noise D D D D D D APPLICATIONS D D D D D − 3 nV/√Hz High Slew Rate: 1000 V/µs Low Distortion − −92 dBc THD at 30 MHz Wide Bandwidth: 1.4 GHz Supply Voltages − +5 V, ±5 V, +12 V, +15 V Power Down Functionality (THS4275) Evaluation Module Available High Linearity ADC Preamplifier Wireless Communication Receivers Differential to Single-Ended Conversion DAC Output Buffer Active Filtering THS4271 NC IN− IN+ VS− DESCRIPTION The THS4271 and THS4275 are low-noise, high slew rate, unity gain stable voltage feedback amplifiers designed to run from supply voltages as low as 5 V and as high as 15 V. The THS4275 offers the same performance as the THS4271 with the addition of power down capability. The combination of low-noise, high slew rate, wide bandwidth, low distortion, and unity gain stability make the THS4271 and THS4275 high performance devices across multiple ac specifications. + VI 49.9 Ω THS4271 _ −5 V 249 Ω 249 Ω VO 3 6 4 5 NC VS+ VOUT NC DESCRIPTION THS4211 1-GHz voltage feedback amplifier THS4503 Wideband fully differential amplifier THS3202 Dual, wideband current feedback amplifier Harmonic and Intermodulation Distortion − dB 50 Ω 7 DEVICE Low-Noise, Low-Distortion, Wideband Application Circuit +5 V 8 2 RELATED DEVICES Designers using the THS4271 are rewarded with higher dynamic range over a wider frequency band without the stability concerns of decompensated amplifiers. The devices are available in SOIC, MSOP with PowerPAD, and leadless MSOP with PowerPAD packages. 50 Ω Source 1 HARMONIC AND INTERMODULATION DISTORTION vs FREQUENCY −40 Gain = 2 Rf = 249 Ω RL = 150 Ω VO = 2 VPP VS = ±5 V −50 −60 IMD3 200 kHz Tone Spacing VO = 2 VPP Envelope −70 −80 HD2 −90 HD3 −100 1 10 f − Frequency − MHz 100 NOTE: Power supply decoupling capacitors not shown Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. PowerPAD is a trademark of Texas Instruments. !" #$%&'()* %$)*+!)" !),$-'+*!$) $) .-$#&%*" !) '$-( *+) $)( .+"( $, #(/(0$.'()*1 ( "*+*&" $, (+% #(/!%( !" !)#!%+*(# $) *( .+2(3"4 ".(%!,5!)2 !*" (0(%*-!%+0 %+-+%*(-!"*!%"1 Copyright 2002 − 2004, Texas Instruments Incorporated www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 ABSOLUTE MAXIMUM RATINGS over operating free-air temperature range unless otherwise noted(1) UNIT 16.5 V Supply voltage, VS ±VS Input voltage, VI ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. 100 mA Output current, IO Continuous power dissipation See Dissipation Rating Table PACKAGE DISSIPATION RATINGS 150°C Maximum junction temperature, TJ Maximum junction temperature, continuous operation, long term reliability TJ (2) PACKAGE θJC (°C/W) θJA(1) (°C/W) D (8 pin) 38.3 DGN (8 pin)(3) 4.7 125°C −65°C to 150°C Storage temperature range, Tstg Lead temperature 1,6 mm (1/16 inch) from case for 10 seconds ESD ratings: This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage. 300°C HBM 3000 V CDM 1500 V MM 1000 V (1) The absolute maximum temperature under any condition is limited by the constraints of the silicon process. Stresses above these ratings may cause permanent damage. Exposure to absolute maximum conditions for extended periods may degrade device reliability. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those specified is not implied. (2) The maximum junction temperature for continuous operation is limited by package constraints. Operation above this temperature may result in reduced reliability and/or lifetime of the device. POWER RATING(2) 97.5 TA ≤ 25°C 1.02 W TA = 85°C 410 mW 58.4 1.71 W 685 mW DGK (8 pin) 54.2 260 385 mW 154 mW DRB (8 pin)(3) 5 45.8 2.18 W 873 mW (1) This data was taken using the JEDEC standard High-K test PCB. (2) Power rating is determined with a junction temperature of 125°C. This is the point where distortion starts to substantially increase. Thermal management of the final PCB should strive to keep the junction temperature at or below 125°C for best performance and long term reliability. (3) The THS4271/5 may incorporate a PowerPAD on the underside of the chip. This acts as a heat sink and must be connected to a thermally dissipative plane for proper power dissipation. Failure to do so may result in exceeding the maximum junction temperature which could permanently damage the device. See TI technical briefs SLMA002 and SLMA004 for more information about utilizing the PowerPAD thermally enhanced package. RECOMMENDED OPERATING CONDITIONS Supply voltage, (VS+ and VS−) MIN MAX Dual supply ±2.5 ±7.5 Single supply 5 15 VS− + 1.4 VS+ − 1.4 Input common-mode voltage range UNIT V V PACKAGING/ORDERING INFORMATION ORDERABLE PACKAGE AND NUMBER PLASTIC SMALL OUTLINE (D) (1) LEADLESS MSOP 8 (2) (DRB) PLASTIC MSOP (1) PowerPAD (DGN) THS4271D THS4271DRBT THS4271DGN THS4271DR THS4271DRBR THS4271DGNR THS4275D THS4275DRBT THS4275DGN THS4275DR THS4275DRBR THS4275DGNR PLASTIC MSOP (1) PACKAGE MARKING (DGK) PACKAGE MARKING THS4271DGK BFQ THS4271DGKR BEY THS4275DGK BFR THS4275DGKR BJD (1) All packages are available taped and reeled. The R suffix standard quantity is 2500 (e.g., THS4271DGNR). (2) All packages are available taped and reeled. The R suffix standard quantity is 3000. The T suffix standard quantity is 250 (e.g., THS4271DRBT). 2 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 PIN ASSIGNMENTS (TOP VIEW) D, DRB, DGN, DGK (TOP VIEW) D, DRB, DGN, DGK THS4271 NC IN− IN+ VS− 1 8 2 7 3 6 4 5 THS4275 NC VS+ VOUT NC REF IN− IN+ VS− 1 8 2 7 3 6 4 5 PD VS+ VOUT NC NC − No internal connection ELECTRICAL CHARACTERISTICS VS = ±5 V RF = 249 Ω, RL = 499 Ω, G = +2, unless otherwise noted. TYP PARAMETER TEST CONDITIONS 25°C OVER TEMPERATURE 25°C 0°C TO 70°C −40°C TO 85°C UNITS MIN/ TYP/ MAX AC PERFORMANCE G = 1, VO = 100 mVPP, RL = 150 Ω 1.4 GHz Typ G = −1, VO = 100 mVPP 400 MHz Typ G = 2, VO = 100 mVPP 390 MHz Typ G = 5, VO = 100 mVPP 85 MHz Typ G = 10, VO = 100 mVPP 40 MHz Typ 0.1 dB flat bandwidth G = 1, VO = 100 mVPP, RL = 150 Ω 200 MHz Typ Gain bandwidth product G > 10, f = 1 MHz 400 MHz Typ Full-power bandwidth G = −1, VO = 2 Vp 80 MHz Typ G = 1, VO = 2 V Step 950 V/µs Typ G = −1, VO = 2 V Step 1000 V/µs Typ Settling time to 0.1% G = −1, VO = 4 V Step 25 ns Typ Settling time to 0.01% G = −1, VO = 4 V Step 38 ns Typ Harmonic distortion G = 1, VO = 1 VPP, f = 30 MHz Second harmonic distortion RL = 150 Ω RL = 499 Ω −92 dBc Typ −80 dBc Typ Third harmonic distortion RL = 150 Ω RL = 499 Ω −95 dBc Typ −95 dBc Typ Harmonic distortion G = 2, VO = 2 VPP, f = 30 MHz Second harmonic distortion RL = 150 Ω RL = 499 Ω −65 dBc Typ −70 dBc Typ Third harmonic distortion RL = 150 Ω RL = 499 Ω −80 dBc Typ −90 dBc Typ Third order intermodulation (IMD3) G = 2, VO = 2 VPP, RL = 150 Ω, f = 70 MHz −60 dBc Typ Third order output intercept (OIP3) G = 2, VO = 2 VPP, RL = 150 Ω, f = 70 MHz 35 dBm Typ Differential gain (NTSC, PAL) G = 2, RL = 150 Ω, 0.007% Differential phase (NTSC, PAL) G = 2, RL = 150 Ω, 0.004 _ Typ Input voltage noise f = 1 MHz 3 nV/√Hz Typ Input current noise f = 1 MHz 3 pA√Hz Typ Small signal bandwidth Slew rate Typ 3 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 ELECTRICAL CHARACTERISTICS VS = ±5 V (continued) RF = 249 Ω, RL = 499 Ω, G = +2, unless otherwise noted. TYP PARAMETER TEST CONDITIONS OVER TEMPERATURE −40°C to 85°C MIN/ TYP/ MAX 25°C 25°C 0°C to 70°C 75 65 60 60 dB Min 5 10 12 12 mV Max ±10 ±10 µV/°C Typ Max UNITS DC PERFORMANCE Open-loop voltage gain (AOL) Input offset voltage Average offset voltage drift Input bias current Average bias current drift Input offset current Average offset current drift VO = ± 50 mV, RL = 499 Ω VCM = 0 V VCM = 0 V VCM = 0 V 6 VCM = 0 V VCM = 0 V 1 15 6 VCM = 0 V 18 18 µA ±10 ±10 nA/°C Typ 8 8 µA Max ±10 ±10 nA/°C Typ INPUT CHARACTERISTICS Common-mode input range Input resistance VCM = ± 2 V Common-mode Input capacitance Common-mode / differential Common-mode rejection ratio ±4 ±3.6 ±3.5 ±3.5 V Min 72 67 65 65 dB Min 5 MΩ Typ 0.4/0.8 pF Typ OUTPUT CHARACTERISTIC8 Output voltage swing G = +2 ±4 ±3.8 ±3.7 ±3.7 V Min Output current (sourcing) 160 120 110 110 mA Min Output current (sinking) RL = 10 Ω RL = 10 Ω 80 60 50 50 mA Min Output impedance f = 1 MHz 0.1 Ω Typ POWER SUPPLY Specified operating voltage ±5 ±7.5 ±7.5 ±7.5 V Max Maximum quiescent current 22 24 27 28 mA Max Minimum quiescent current 22 20 18 15 mA Min 85 75 70 70 dB Min 75 65 60 60 dB Min Power supply rejection (+PSRR) Power supply rejection (−PSRR) VS+ = 5.5 V to 4.5 V, VS− = 5 V VS+ = 5 V, VS− = −5.5 V to −4.5 V POWER-DOWN CHARACTERISTICS (THS4275 only) Power-down voltage level(1) Power-down quiescent current REF = 0 V, or VS− Enable REF+1.8 V Min Power down REF+1 V Max REF = VS+ or Floating Enable REF−1 V Min V Max PD = Ref +1.0 V, Ref = 0 V Power down 875 REF−1.7 1000 1100 1200 µA Max PD = Ref −1.7 V, Ref = VS+ 650 800 900 1000 µA Max Turnon time delay(t(ON)) 50% of final supply current value 4 µs Typ Turnoff time delay (t(OFF)) 50% of final supply current value 3 µs Typ Input impedance f = 1 MHz 4 GΩ Typ 200 kΩ Typ Output impedance (1) For detail information on the power-down circuit, see the powerdown section in the application information of this data sheet. 4 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 ELECTRICAL CHARACTERISTICS VS = 5 V RF = 249 Ω, RL = 499 Ω, G = +2, unless otherwise noted TYP PARAMETER TEST CONDITIONS 25°C OVER TEMPERATURE 25°C 0°C to 70°C −40°C to 85°C UNITS MIN/ TYP/ MAX AC PERFORMANCE Small signal bandwidth G = 1, VO = 100 mVPP, RL = 150 Ω 1.2 GHz Typ G = −1, VO = 100 mVPP 380 MHz Typ G = 2, VO = 100 mVPP 360 MHz Typ G = 5, VO = 100 mVPP 80 MHz Typ G = 10, VO = 100 mVPP 35 MHz Typ 0.1-dB flat bandwidth G = 1, VO = 100 mVPP, RL = 150 Ω 120 MHz Typ Gain bandwidth product G > 10 , f = 1 MHz 350 MHz Typ Full-power bandwidth G = −1, VO = 2 Vp 60 MHz Typ G = 1, VO = 2 V Step 700 V/µs Typ G = −1, VO = 2 V Step 750 V/µs Typ Settling time to 0.1% G = −1, VO = 2 V Step 18 ns Typ Settling time to 0.01% G = −1, VO = 2 V Step 66 ns Typ Harmonic distortion G = 1, VO = 1 VPP, f = 30 MHz Second harmonic distortion RL = 150 Ω RL = 499 Ω −75 dBc Typ −72 dBc Typ Third harmonic distortion RL = 150 Ω RL = 499 Ω −70 dBc Typ −70 dBc Typ Third order intermodulation (IMD3) G = 2, VO = 1 VPP, RL = 150 Ω, f = 70 MHz −65 dBc Typ Third order output intercept (OIP3) G = 2, VO = 1 VPP, RL = 150 Ω, f = 70 MHz 32 dBm Typ Input voltage noise f = 1 MHz 3 nV/√Hz Typ Input current noise f = 10 MHz 3 pA/√Hz Typ VO = ± 50 mV, RL = 499 Ω VCM = VS/2 68 63 60 60 dB Min 5 10 12 12 mV Max VCM = VS/2 VCM = VS/2 ±10 ±10 µV/°C Typ 6 15 18 18 µA Max VCM = VS/2 VCM = VS/2 ±10 ±10 nA/°C Typ 1 6 8 8 µA Max ±10 ±10 nA/°C Typ Slew rate DC PERFORMANCE Open-loop voltage gain (AOL) Input offset voltage Average offset voltage drift Input bias current Average bias current drift Input offset current Average offset current drift VCM = VS/2 INPUT CHARACTERISTICS Common-mode input range 1/4 1.3/3.7 1.4/3.6 1.5/3.5 V Min 72 67 65 65 dB Min Input resistance VCM = ± 0.5 V, VO = 2.5 V Common-mode 5 MΩ Typ Input capacitance Common-mode / differential 0.4/0.8 pF Typ Output voltage swing G = +2 1.2/3.8 1.4/3.6 1.5/3.5 1.5/3.5 V Min Output current (sourcing) 120 100 90 90 mA Min Output current (sinking) RL = 10 Ω RL = 10 Ω 65 50 40 40 mA Min Output impedance f = 1 MHz 0.1 Ω Typ Common-mode rejection ratio OUTPUT CHARACTERISTICS 5 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 ELECTRICAL CHARACTERISTICS VS = 5 V (continued) RF = 249 Ω, RL = 499 Ω, G = +2, unless otherwise noted TYP PARAMETER OVER TEMPERATURE UNITS MIN/ TYP/ MAX 15 V Max 27 mA Max 16 14 mA Min 75 62 62 dB Min 65 60 60 dB Min REF+1.8 V Min Power-down REF+1 V Max Enable REF−1 V Min REF−1.7 V Max TEST CONDITIONS 25°C 25°C 0°C to 70°C Specified operating voltage 5 15 15 Maximum quiescent current 20 22 25 Minimum quiescent current 20 18 85 75 −40°C to 85°C POWER SUPPLY Power supply rejection (+PSRR) Power supply rejection (−PSRR) VS+ = 5.5 V to 4.5 V, VS− = 0 V VS+ = 5 V, VS− = −0.5 V to 0.5 V POWER-DOWN CHARACTERISTICS (THS4275 Only) Enable REF = 0 V, or VS− Power-down voltage level(1) REF = VS+ or Floating Power-down quiescent current Power-down PD = Ref +1.0 V, Ref = 0 V 650 800 900 1000 µA Max PD = Ref −1.7 V, Ref = VS+ 650 800 900 1000 µA Max µs Typ Turnon time delay(t(ON)) 50% of final value 4 Turnoff time delay (t(OFF)) 50% of final value 3 µs Typ Input impedance f = 1 MHz 6 GΩ Typ 100 kΩ Typ Output impedance (1) For detail information on the power-down circuit, see the powerdown section in the application information of this data sheet. 6 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 TYPICAL CHARACTERISTICS Table of Graphs (±5 V) FIGURE Small signal unity gain frequency response 1 Small signal frequency response 2 0.1-dB gain flatness frequency response 3 Large signal frequency response 4 Slew rate vs Output voltage 5 Harmonic distortion vs Frequency Harmonic distortion vs Output voltage swing 6, 7, 8, 9 10, 11, 12, 13 Third order intermodulation distortion vs Frequency 14, 16 Third order intercept point vs Frequency 15, 17 Voltage and current noise vs Frequency 18 Differential gain vs Number of loads 19 Differential phase vs Number of loads 20 Settling time 21 Quiescent current vs Supply voltage 22 Output voltage vs Load resistance 23 Frequency response vs Capacitive load 24 Open-loop gain and phase vs Frequency 25 Open-loop gain vs Case temperature 26 Rejection ratios vs Frequency 27 Rejection ratios vs Case temperature 28 Common-mode rejection ratio vs Input common-mode range 29 Input offset voltage vs Case temperature 30 Input bias and offset current vs Case temperature 31 Small signal transient response 32 Large signal transient response 33 Overdrive recovery 34 Closed-loop output impedance vs Frequency 35 Power-down quiescent current vs Supply voltage 36 Power-down output impedance vs Frequency 37 Turnon and turnoff delay times 38 7 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 TYPICAL CHARACTERISTICS Table of Graphs (5 V) FIGURE Small signal unity gain frequency response 39 Small signal frequency response 40 0.1-dB gain flatness frequency response 41 Large signal frequency response 42 Slew rate vs Output voltage 43 Harmonic distortion vs Frequency 44, 45, 46, 47 Harmonic distortion vs Output voltage swing 48, 49, 50, 51 Third order intermodulation distortion vs Frequency 52, 54 Third order intercept point vs Frequency 53, 55 Voltage and current noise vs Frequency 56 Settling time 57 Quiescent current vs Supply voltage 58 Output voltage vs Load resistance 59 Frequency response vs Capacitive load 60 Open-loop gain and phase vs Frequency 61 Open-loop gain vs Case temperature 62 Rejection ratios vs Frequency 63 Rejection ratios vs Case temperature 64 Common-mode rejection ratio vs Input common-mode range 65 Input offset voltage vs Case temperature 66 Input bias and offset current vs Case temperature 67 Small signal transient response 68 Large signal transient response 69 Overdrive recovery 70 Closed-loop output impedance vs Frequency 71 Power-down quiescent current vs Supply voltage 72 Power-down output impedance vs Frequency 73 Turnon and turnoff delay times 74 8 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 TYPICAL CHARACTERISTICS (±5 V GRAPHS) SMALL SIGNAL UNITY GAIN FREQUENCY RESPONSE 18 1 0 −1 −2 −4 100 k 1M 10 M 1G 100 M 16 Gain = 5 14 RL = 499 Ω Rf = 249 Ω VO = 100 mVPP VS = ±5 V 12 10 8 6 Gain = 2 4 2 0 Gain = −1 −2 −4 100 k 1M −3 10 G 0 Gain = 10 f − Frequency − Hz Figure 1 10 M 100 M f − Frequency − Hz RL = 499 Ω Rf = 249 Ω VO = 1 VPP VS = ±5 V 6 Rise 600 400 Gain = −1 RL = 499 Ω Rf = 249 Ω VS = ±5 V 1G 0 f − Frequency − Hz Figure 4 Harmonic Distortion − dBc HD3, RL = 499Ω −80 HD3, RL = 150Ω HD2, RL = 499Ω 0.5 1 1.5 2 2.5 3 3.5 4 4.5 Figure 7 1 5 10 f − Frequency − MHz 100 100 Figure 6 HARMONIC DISTORTION vs FREQUENCY −50 Gain = 2 Rf = 249 Ω VO = 1 VPP VS = ±5 V −60 −70 HD3, RL = 499Ω HD3, RL = 150Ω −80 HD2, RL = 499Ω HD2, RL = 150Ω −90 −100 −100 10 f − Frequency − MHz HD2, RL = 150Ω HD2, RL = 499Ω −90 −50 HD2, RL = 150Ω 1 −80 HARMONIC DISTORTION vs FREQUENCY Gain = 1 VO = 2 VPP VS = ±5 V −90 HD3, RL = 499Ω HD3, RL = 150Ω Figure 5 −50 −70 −70 VO − Output Voltage − V HARMONIC DISTORTION vs FREQUENCY 1G Gain = 1 VO = 1 VPP VS = ±5 V −60 Harmonic Distortion − dBc 100 M 100 M −100 0 10 M 10 M HARMONIC DISTORTION vs FREQUENCY 800 200 1M 1M −50 2 −60 Gain = 1 RL = 150 Ω VO = 100 mVPP VS = ±5 V Figure 3 Gain = 2 0 100 k −0.7 f − Frequency − Hz Harmonic Distortion − dBc SR − Slew Rate − V/ µ s 14 4 −0.6 −1 100 k 1G 1000 Gain = 5 8 −0.5 Fall Gain = 10 10 −0.4 −0.9 1200 12 −0.3 −0.8 20 16 −0.2 SLEW RATE vs OUTPUT VOLTAGE 22 18 −0.1 Figure 2 LARGE SIGNAL FREQUENCY RESPONSE Large Signal Gain − dB Small Signal Gain − dB 2 20 Small Signal Gain − dB Small Signal Gain − dB 0.1 22 Gain = 1 RL = 150 Ω VO = 100 mVPP VS = ±5 V 3 Harmonic Distortion − dBc 0.1 dB GAIN FLATNESS FREQUENCY RESPONSE SMALL SIGNAL FREQUENCY RESPONSE 4 Gain = 2 Rf = 249 Ω VO = 2 VPP VS = ±5 V HD3, RL = 499Ω −60 −70 HD2, RL = 499Ω HD3, RL = 150Ω −80 HD2, RL = 150Ω −90 −100 1 10 f − Frequency − MHz Figure 8 100 1 10 f − Frequency − MHz 100 Figure 9 9 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 −50 −50 −60 −70 Harmonic Distortion − dBc Gain = 1 f= 8 MHz VS = ±5 V HD3, RL = 150Ω HD3, RL = 499Ω −80 HD2, RL = 499Ω HD2, RL = 150Ω −90 −60 Gain = 1 f= 32 MHz VS = ±5 V −70 HD2, RL = 150Ω Gain = 2 Rf = 249 Ω f = 8 MHz VS = ±5 V HD2, RL = 499Ω −60 Harmonic Distortion − dBc −50 Harmonic Distortion − dBc HARMONIC DISTORTION vs OUTPUT VOLTAGE SWING HARMONIC DISTORTION vs OUTPUT VOLTAGE SWING HARMONIC DISTORTION vs OUTPUT VOLTAGE SWING HD3, RL = 150Ω −80 −90 HD3, RL = 499Ω −70 HD2, RL = 499Ω HD3, RL = 150Ω −80 HD2, RL = 150Ω −90 HD3, RL = 499Ω −100 −100 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 VO − Output Voltage Swing − VPP 1 2 3 4 VO − Output Voltage Swing − VPP Figure 10 HD3, RL = 150Ω −90 HD3, RL = 499Ω −100 0 1 2 3 4 VO − Output Voltage Swing − VPP 5 −40 55 Gain = 1 RL = 150 Ω VS = ±5 V 200 kHz Tone Spacing −50 −60 −70 VO = 2 VPP −80 −90 VO = 1 VPP −100 10 35 30 0 20 40 60 f − Frequency − MHz 50 −60 VO = 2 VPP −70 −80 VO = 1 VPP −90 −100 10 100 100 VO = 2 VPP 45 40 Gain = 2 RL = 150 Ω VS = ±5 V 200 kHz Tone Spacing VO = 1 VPP 35 30 0 20 40 60 f − Frequency − MHz Figure 17 80 100 Hz Gain = 2 RL = 150 Ω VS = ±5 V 200 kHz Tone Spacing 100 VOLTAGE AND CURRENT NOISE vs FREQUENCY Vn − Voltage Noise − nV/ −40 80 Figure 15 THIRD ORDER OUTPUT INTERCEPT POINT vs FREQUENCY Third-Order Output Intersept Point − dBm Third-Order Intermodulation Distortion − dBc VO = 1 VPP 40 Figure 14 f − Frequency − MHz 10 VO = 2 VPP 45 f − Frequency − MHz THIRD ORDER INTERMODULATION DISTORTION vs FREQUENCY Figure 16 Gain = 1 RL = 150 Ω VS = ±5 V 200 kHz Tone Spacing 50 100 Figure 13 −50 THIRD ORDER OUTPUT INTERCEPT POINT vs FREQUENCY Hz −80 Third-Order Intermodulation Distortion − dBc Harmonic Distortion − dBc −70 5 Figure 12 THIRD ORDER INTERMODULATION DISTORTION vs FREQUENCY Gain = 2 Rf = 249 Ω f = 32 MHz HD2, RL = 499Ω VS = ±5 V HD2, RL = 150Ω −60 0.5 1 1.5 2 2.5 3 3.5 4 4.5 VO − Output Voltage Swing − VPP Figure 11 HARMONIC DISTORTION vs OUTPUT VOLTAGE SWING −50 0 5 Third-Order Output Intersept Point − dBm 0 100 Vn 10 10 In 1 100 1k 10 k 100 k 1M f − Frequency − Hz Figure 18 10 M I n − Current Noise − pA/ −100 1 100 M www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 DIFFERENTIAL GAIN vs NUMBER OF LOADS DIFFERENTIAL PHASE vs NUMBER OF LOADS 0.015 Differential Phase − 0.020 ° NTSC 0.010 Rising Edge Gain = 2 Rf = 1.3 kΩ VS = ±5 V 40 IRE − NTSC and Pal Worst Case ±100 IRE Ramp 0.09 0.08 0.07 2 VO − Output Voltage − V Gain = 2 Rf = 1.3 kΩ VS = ±5 V 40 IRE − NTSC and Pal Worst Case ±100 IRE Ramp 0.025 Differential Gain − % SETTLING TIME 3 0.10 0.030 0.06 0.05 PAL 0.04 0.03 NTSC 0.005 Gain = −1 RL = 499 Ω Rf = 249 Ω f= 1 MHz VS = ±5 V 0 −1 Falling Edge −2 0.02 PAL 1 0.01 −3 0 0 1 2 3 4 5 6 7 0 8 0 Number of Loads − 150 Ω 1 2 4 5 6 7 0 8 0.5 4 VO − Output Voltage − V TA = 25°C 20 TA = −40°C 15 10 5 0 VS = ±5 V TA = −40 to 85°C 3 2 Normalized Gain − dB 25 1 0 −1 −2 4 4.5 10 5 VS − Supply Voltage − ±V 100 1k RL − Load Resistance − Ω Figure 22 Gain 85 20 80 40 60 40 80 30 100 Phase 120 10 140 0 160 100 k 1M 10 M f − Frequency − Hz Figure 25 10 M 100 M 180 1G 100 M Capacitive Load − Hz Figure 24 REJECTION RATIOS vs FREQUENCY 100 VS = ±5 V 90 Phase − ° Open-Loop Gain − dB 0 50 −10 10 k RL = 499 Ω VS =±5 V −3 1M 10 k TA = −40°C TA = 25°C PSRR+ 80 Rejection Ratios − dB VS = ±5 V 20 −2 OPEN-LOOP GAIN vs CASE TEMPERATURE Open-Loop Gain − dB 80 60 R(ISO) = 10 Ω CL = 50 pF −1.5 Figure 23 OPEN-LOOP GAIN AND PHASE vs FREQUENCY 70 R(ISO) = 15 Ω CL = 100 pF −1 −2.5 −5 0 R(ISO) = 25 Ω CL = 10 pF −0.5 −3 −4 3.5 25 FREQUENCY RESPONSE vs CAPACITIVE LOAD 5 TA = 85°C 3 20 Figure 21 OUTPUT VOLTAGE vs LOAD RESISTANCE 30 2.5 10 15 t − Time − ns Figure 20 QUIESCENT CURRENT vs SUPPLY VOLTAGE 2 5 Number of Loads − 150 Ω Figure 19 Quiescent Current − mA 3 75 70 TA = 85°C 65 60 70 PSRR− 60 50 CMRR 40 30 20 55 50 10 0 2.5 3 3.5 4 Case Temperature − °C Figure 26 4.5 5 10 k 100 k 1M 10 M f − Frequency − Hz 100 M Figure 27 11 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 REJECTION RATIOS vs CASE TEMPERATURE PSRR+ 80 60 CMMR 40 20 0 −40−30−20−100 10 20 30 40 50 60 70 80 90 80 70 60 50 40 VS = ±5 V TA = 25°C 30 20 −6 −4 −2 8 0 2 4 0 −40−30−20−10 0 10 20 30 40 50 60 70 80 90 6 TC − Case Temperature − °C Figure 30 SMALL SIGNAL TRANSIENT RESPONSE 1.17 LARGE SIGNAL TRANSIENT RESPONSE 0.3 1.5 0.2 1 IIB− 6 IOS 1.15 1.14 5 IIB+ 4 1.13 3 1.12 2 1.11 1 1.1 0.1 0 Gain = −1 RL = 499 Ω Rf = 249 Ω tr/tf = 300 ps VS = ±5 V −0.1 −0.2 0 Gain = −1 RL = 499 Ω Rf = 249 Ω tr/tf = 300 ps VS = ±5 V −0.5 −1.5 0 2 4 TC − Case Temperature − °C 6 8 10 12 14 16 0 2 t − Time − ns Figure 31 Figure 32 OVERDRIVE RECOVERY 3 2.5 4 2 3 1.5 2 1 1 0.5 0 0 −1 −0.5 −2 −1 −3 −1.5 −4 −2 −5 −2.5 −3 −6 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 t − Time − µs 1 100 Gain = 1 RL = 499 Ω PIN = −1 dBm VS = ±5 V 10 1 0.1 0.01 0.001 100 k 6 8 10 12 14 t − Time − ns 16 18 POWER-DOWN QUIESCENT CURRENT vs SUPPLY VOLTAGE 1200 1000 VI − Input Voltage − V Closed-Loop Output Impedance − Ω VS = ±5 V 4 Figure 33 CLOSED-LOOP OUTPUT IMPEDANCE vs FREQUENCY 6 Figure 34 0.5 −1 −0.3 1.09 0 −40−30−20−10 0 10 20 30 40 50 60 70 80 90 5 VO − Output Voltage − V 1.16 VO − Output Voltage − V VS = ±5 V I OS − Input Offset Current − µ A I IB − Input Bias Current − µ A 1 Figure 29 INPUT BIAS AND OFFSET CURRENT vs CASE TEMPERATURE Single-Ended Output Voltage − V VS = ±5 V 2 Input Common-Mode Range − V Figure 28 12 VS = 5 V 3 0 Case Temperature − °C 7 4 10 Power-down Quiescent Current − µ A Rejection Ratios − dB PSRR− 90 VOS − Input Offset Voltage − mV VS = ±5 V 5 100 CMRR − Common-Mode Rejection Ratio − dB 120 100 INPUT OFFSET VOLTAGE vs CASE TEMPERATURE COMMON-MODE REJECTION RATIO vs INPUT COMMON-MODE RANGE TA = 85°C 1000 TA = 25°C 800 TA = −40°C 600 400 200 0 1M 10 M 100 M f − Frequency − Hz Figure 35 1G 2.5 3 3.5 4 4.5 VS − Supply Voltage − ±V Figure 36 5 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 TURNON AND TURNOFF TIMES DELAY TIME Input Gain = 1 RL = 150 Ω VIN = 1 dBm VS = ±5 V I O− Output Current Level − mV Power-down Output Impedance − Ω 100 k 6.5 45 1M 10 k 100 40 5 35 3.5 30 2 25 0.5 20 −1 15 10 0.5 Gain = −1 RL = 150 Ω VS = ±5 V 0 1 100 k 1M 10 M 100 M f − Frequency − Hz Figure 37 1G V I − Input Voltage Level − V POWER-DOWN OUTPUT IMPEDANCE vs FREQUENCY 0 10 20 30 40 50 60 70 t − Time − µs Figure 38 13 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 TYPICAL CHARACTERISTICS (5 V GRAPHS) SMALL SIGNAL UNITY GAIN FREQUENCY RESPONSE 3 22 16 −1 −2 1M 10 M 100 M 1G Gain = 5 14 RL = 499 Ω Rf = 249 Ω VO = 100 mVPP VS = 5 V 12 10 8 6 Gain = 2 4 2 −3 −4 100 k 0 Gain = −1 −2 −4 100 k 1M 10 G f − Frequency − Hz Figure 39 RL = 499 Ω Rf = 249 Ω VO = 1 VPP VS = 5 V −0.6 −0.7 Gain = 2 Gain = 1 RL = 150 Ω VO = 100 mVPP VS = 5 V 1M 10 M 100 M 1G f − Frequency − Hz Figure 41 HARMONIC DISTORTION vs FREQUENCY −50 800 700 600 Fall Rise 500 400 300 200 Gain = 1 VO = 1 VPP RL = 150 Ω VS = 5 V −60 −70 −80 HD3 HD2 −90 100 2 −100 0 0 100 k 1M 10 M 100 M 0 1G f − Frequency − Hz Figure 42 0.5 1 1.5 2 VO − Output Voltage −V 1 2.5 HARMONIC DISTORTION vs FREQUENCY 0 −50 −30 −40 −50 HD3 −60 −70 HD2 −80 −60 −70 −80 HD3 −90 HD2 −20 −30 −40 −50 −70 −90 −100 f − Frequency − MHz Figure 45 100 −100 1 10 f − Frequency − MHz Figure 46 100 HD3 −80 −100 10 HD2 −60 −90 1 Gain = 2 Rf = 249 Ω RL = 150 Ω VO = 2 VPP VS = 5 V −10 Gain = 2 Rf = 249 Ω RL = 249 Ω VO = 1 VPP VS = 5 V Harmonic Distortion − dBc −20 Harmonic Distortion − dBc Gain = 1 VO = 2 VPP RL = 150 Ω VS = 5 V 100 Figure 44 HARMONIC DISTORTION vs FREQUENCY 0 −10 10 f − Frequency − MHz Figure 43 HARMONIC DISTORTION vs FREQUENCY Harmonic Distortion − dBc −0.5 −1 100 k 1G 6 4 14 10 M 100 M f − Frequency − Hz Harmonic Distortion − dBc SR − Slew Rate − V/ µ s Large Signal Gain − dB Gain = 5 8 −0.4 −0.9 Gain = 1 RL = 499 Ω Rf = 249 Ω VS = 5 V 900 18 10 −0.3 −0.8 1000 Gain = 10 12 −0.2 SLEW RATE vs OUTPUT VOLTAGE 22 20 0 −0.1 Figure 40 LARGE SIGNAL FREQUENCY RESPONSE 14 Small Signal Gain − dB 0 0.1 Gain = 10 18 Small Signal Gain − dB Small Signal Gain − dB 1 0.2 20 Gain = 1 RL = 150 Ω VO = 100 mVPP VS = 5 V 2 16 0.1 dB GAIN FLATNESS FREQUENCY RESPONSE SMALL SIGNAL FREQUENCY RESPONSE 1 10 f − Frequency − MHz Figure 47 100 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 −50 HD3, RL = 499Ω HD3, RL = 150Ω −80 HD2, RL = 499Ω −90 −60 HD3, RL = 150Ω −70 HD2, RL = 150Ω −80 HD2, RL = 499Ω −80 HD2, RL = 499Ω −90 −100 −100 1 1.5 2 2.5 0 VO − Output Voltage Swing − VPP 0.5 1 1.5 2 VO − Output Voltage Swing − VPP Figure 48 Third-Order Intermodulation Distortion − dBc HD2, RL = 150Ω HD3, RL = 499Ω −70 HD2, RL = 499Ω −80 −90 −100 0 0.5 1 1.5 2 VO − Output Voltage Swing − VPP −40 45 Gain = 1 RL = 150 Ω VO = 1 VPP VS = 5 V 200 kHz Tone Spacing −50 −60 −70 −80 −90 −100 10 2.5 100 Gain = 1 RL = 150 Ω VO = 1 VPP VS = 5 V 200 kHz Tone Spacing 25 20 0 20 Third-Order Output Intersept Point − dBm −70 −80 −90 100 60 80 VOLTAGE AND CURRENT NOISE vs FREQUENCY 100 Gain = 2 RL = 150 Ω VO = 2 VPP VS = 5 V 200 kHz Tone Spacing 40 35 30 25 0 20 40 100 Figure 53 45 Gain = 2 RL = 150 Ω VO = 2 VPP VS = 5 V 200 kHz Tone Spacing 40 f − Frequency − MHz THIRD ORDER OUTPUT INTERCEPT POINT vs FREQUENCY −40 −100 10 30 Figure 52 THIRD ORDER INTERMODULATION DISTORTION vs FREQUENCY −60 35 f − Frequency − MHz Figure 51 −50 40 60 f − Frequency − MHz f − Frequency − MHz Figure 54 Figure 55 80 100 Hz −60 THIRD ORDER OUTPUT INTERCEPT POINT vs FREQUENCY Vn − Voltage Noise − nV/ −50 HD3, RL = 150Ω 2.5 Figure 50 THIRD ORDER INTERMODULATION DISTORTION vs FREQUENCY −30 −40 0.5 1 1.5 2 VO − Output Voltage Swing − VPP Figure 49 HARMONIC DISTORTION vs OUTPUT VOLTAGE SWING Gain = 2 Rf = 249 Ω f = 32 MHz VS = 5 V 0 2.5 Third-Order Output Intersept Point − dBm 0.5 HD2, RL = 150Ω −70 HD3, RL = 499Ω −100 Harmonic Distortion − dBc −60 HD3, RL = 150Ω −90 HD2, RL = 150Ω 0 Gain = 2 Rf = 249 Ω f = 8 MHz VS = 5 V Hz −70 HD3, RL = 499Ω 100 Vn 10 10 In 1 100 1k 10 k 100 k 1M 10 M I n − Current Noise − pA/ −60 Gain = 1 f= 32 MHz VS = 5 V Harmonic Distortion − dBc Gain = 1 f= 8 MHz VS = 5 V Harmonic Distortion − dBc Harmonic Distortion − dBc −50 −40 −50 Third-Order Intermodulation Distortion − dBc HARMONIC DISTORTION vs OUTPUT VOLTAGE SWING HARMONIC DISTORTION vs OUTPUT VOLTAGE SWING HARMONIC DISTORTION vs OUTPUT VOLTAGE SWING 1 100 M f − Frequency − Hz Figure 56 15 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 OUTPUT VOLTAGE vs LOAD RESISTANCE QUIESCENT CURRENT vs SUPPLY VOLTAGE SETTLING TIME 2 30 1.5 TA = 85°C 1.5 Rising Edge 25 Gain = −1 RL = 499 Ω Rf = 249 Ω f= 1 MHz VS = 5 V 0.5 0 −0.5 Falling Edge TA = 25°C 20 TA = −40°C 15 10 5 −1 6 8 2.5 3 Figure 57 4.5 −0.5 R(ISO) = 25 Ω, CL = 10 pF −1 R(ISO) = 15 Ω, CL = 50 pF −1.5 R(ISO) = 10 Ω, CL = 100 pF −2 RL = 499 Ω VS = 5 V −3 10 100 80 30 100 Phase 120 TA = 85°C 65 60 0 160 55 −10 10 k 180 50 10 M 100 M 1G 2.5 3 120 VS = 5 V PSRR+ Rejection Ratios − dB 100 PSRR− 60 CMRR 40 30 PSRR− 80 60 CMMR 40 20 20 VS = 5 V 100 k 1M 10 M f − Frequency − Hz 100 M 0 −40−30−20−100 10 20 30 40 50 60 70 80 90 Case Temperature − °C Figure 64 4 4.5 5 Figure 62 REJECTION RATIOS vs CASE TEMPERATURE PSRR+ 3.5 Case Temperature − °C Figure 61 90 16 70 140 1M TA = 25°C 75 10 100 k TA = −40°C f − Frequency − Hz 100 Figure 63 80 40 40 REJECTION RATIOS vs FREQUENCY 0 10 k 85 20 60 20 10 k OPEN-LOOP GAIN vs CASE TEMPERATURE 50 Figure 60 10 100 1k RL − Load Resistance − Ω Figure 59 Gain Capacitive Load − MHz 50 10 5 0 60 Open-Loop Gain − dB Frequency Response − dB 4 VS = 5 V 70 0 Rejection Ratios − dB 3.5 80 70 −1 OPEN-LOOP GAIN AND PHASE vs FREQUENCY 0.5 80 −0.5 Figure 58 FREQUENCY RESPONSE vs CAPACITIVE LOAD 1 0 VS − Supply Voltage − ±V t − Time − ns −2.5 VS = 5 V TA = −40 to 85°C 0.5 −2 2 10 12 14 16 18 20 22 24 Phase − ° 4 Open-Loop Gain − dB 0 2 1 −1.5 0 COMMON-MODE REJECTION RATIO vs INPUT COMMON-MODE RANGE CMRR − Common-Mode Rejection Ratio − dB −1.5 VO − Output Voltage − V Quiescent Current − mA VO − Output Voltage − V 1 100 VS = 5 V 90 80 70 60 50 40 30 20 10 0 0 1 2 3 4 5 Input Common-Mode Voltage Range − V Figure 65 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 INPUT BIAS AND OFFSET CURRENT vs CASE TEMPERATURE 5 8 I IB − Input Bias Current − µ A 3 VS = ±5 V 2 1 6 4 1.14 1.13 3 1.12 2 1.11 1 1.1 Gain = −1 RL = 499 Ω Rf = 249 Ω tr/tf = 300 ps VS = 5 V 1.5 6 7 8 9 2 1 1 0.5 0 0 −1 −0.5 −2 −1 10 11 −1.5 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Power-down Output Impedance − Ω TA = 25°C TA = −40°C 600 400 200 2.5 3 3.5 4 4.5 VS − Supply Voltage − ±V Figure 72 5 16 1 0.1 0.01 0.001 100 k 1M 10 M 100 M 1G Figure 71 6.5 45 Gain = 1 RL = 150 Ω PIN = −1 dBm VS = 5 V Input 10 k 100 40 5 35 3.5 30 2 25 0.5 20 −1 15 10 0.5 Gain = −1 RL = 150 Ω VS = 5 V 0 0 14 f − Frequency − Hz 1M 800 12 POWER-DOWN OUTPUT IMPEDANCE vs TURNON AND TURNOFF TIMES DELAY TIME FREQUENCY 1200 TA = 85°C 10 10 Figure 70 POWER-DOWN QUIESCENT CURRENT vs SUPPLY VOLTAGE 8 Gain = 1 RL = 499 Ω VIN = 1 dBm VS = 5 V 100 t − Time − µs Figure 69 6 1000 VS = 5 V t − Time − ns 1000 4 CLOSED-LOOP OUTPUT IMPEDANCE vs FREQUENCY −3 −1.5 5 2 1 100 k 10 M 100 M 1M f − Frequency − Hz Figure 73 1G V I − Input Voltage Level − V 0 3 4 0 t − Time − ns VI − Input Voltage − V Closed-Loop Output Impedance − Ω 0.5 2 −0.2 OVERDRIVE RECOVERY Single-Ended Output Voltage − V 1 1 Gain = −1 RL = 499 Ω Rf = 249 Ω tr/tf = 300 ps VS = 5 V −0.1 Figure 68 3 0 0 Figure 67 1.5 −1 0.1 TC − Case Temperature − °C LARGE SIGNAL TRANSIENT RESPONSE −0.5 0.2 −0.3 1.09 −40−30−20−10 0 10 20 30 40 50 60 70 80 90 Figure 66 VO − Output Voltage − V 1.15 IIB+ TC − Case Temperature − °C Power-down Quiescent Current − µ A IOS 5 0 0 −40−30−20−10 0 10 20 30 40 50 60 70 80 90 1.16 IIB− I O− Output Current Level − mV VOS − Input Offset Voltage − mV 7 VS = 5 V 0.3 1.17 VS = 5 V 4 SMALL SIGNAL TRANSIENT RESPONSE I OS − Input Offset Current − µ A VO − Output Voltage − V INPUT OFFSET VOLTAGE vs CASE TEMPERATURE 0 10 20 30 40 50 60 70 t − Time − µs Figure 74 17 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 APPLICATION INFORMATION HIGH-SPEED OPERATIONAL AMPLIFIERS The THS4271 and the THS4275 operational amplifiers set new performance levels, combining low distortion, high slew rates, low noise, and a unity-gain bandwidth in excess of 1 GHz. To achieve the full performance of the amplifier, careful attention must be paid to printed-circuit board layout and component selection. The THS4275 provides a power-down mode, providing the ability to save power when the amplifier is inactive. A reference pin is provided to allow the user the flexibility to control the threshold levels of the power-down control pin. Applications Section Contents D D D D D D D D D D D D D D D D D D Wideband, Noninverting Operation Wideband, Inverting Gain Operation Single Supply Operation Saving Power With Power-Down Functionality and Setting Threshold Levels With the Reference Pin Power Supply Decoupling Techniques and Recommendations Using the THS4271 as a DAC Output Buffer Driving an ADC With the THS4271 Active Filtering With the THS4271 Building a Low-Noise Receiver With the THS4271 Linearity: Definitions, Terminology, Circuit Techniques and Design Tradeoffs An Abbreviated Analysis of Noise in Amplifiers Driving Capacitive Loads Printed Circuit Board Layout Techniques for Optimal Performance Power Dissipation and Thermal Considerations Performance vs Package Options Evaluation Fixtures, Spice Models, and Applications Support Additional Reference Material Mechanical Package Drawings WIDEBAND, NONINVERTING OPERATION The THS4271 and the THS4275 are unity gain stable 1.4-GHz voltage feedback operational amplifiers, with and without power-down capability, designed to operate from a single 5-V to 15-V power supply. Figure 75 is the noninverting gain configuration of 2 V/V used to demonstrate the typical performance curves. Most of the curves were characterized using signal sources with 18 50-Ω source impedance, and with measurement equipment presenting a 50-Ω load impedance. In Figure 75, the 49.9-Ω shunt resistor at the VIN terminal matches the source impedance of the test generator. The total 499-Ω load at the output, combined with the 498-Ω total feedback network load, presents the THS4271 and THS4275 with an effective output load of 249 Ω for the circuit of Figure 75. Voltage feedback amplifiers, unlike current feedback designs, can use a wide range of resistors values to set their gain with minimal impact on their stability and frequency response. Larger-valued resistors decrease the loading effect of the feedback network on the output of the amplifier, but this enhancement comes at the expense of additional noise and potentially lower bandwidth. Feedback resistor values between 249 Ω and 1 kΩ are recommended for most situations. 5 V +V S + 100 pF 50 Ω Source 0.1 µF 6.8 µF + VI VO THS4271 49.9 Ω _ Rf 249 Ω 499 Ω 249 Ω Rg 0.1 µF 6.8 µF 100 pF −5 V + −VS Figure 75. Wideband, Noninverting Gain Configuration WIDEBAND, INVERTING GAIN OPERATION Since the THS4271 and THS4275 are general-purpose, wideband voltage-feedback amplifiers, several familiar operational amplifier applications circuits are available to the designer. Figure 76 shows a typical inverting configuration where the input and output impedances and noise gain from Figure 75 are retained in an inverting circuit configuration. Inverting operation is one of the more common requirements and offers several performance benefits. The inverting configuration shows improved slew rates and distortion due to the pseudo-static voltage maintained on the inverting input. www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 5 V +V S + 100 pF 0.1 µF 6.8 µF + RT 130 Ω CT 0.1 µF 50 Ω Source VI VO THS4271 _ 499 Ω Rg Rf 249 Ω RM 61.9 Ω 249 Ω 0.1 µF 100 pF −5 V The last major consideration in inverting amplifier design is setting the bias current cancellation resistor on the noninverting input. If the resistance is set equal to the total dc resistance looking out of the inverting terminal, the output dc error, due to the input bias currents, is reduced to (input offset current) multiplied by Rf in Figure 76, the dc source impedance looking out of the inverting terminal is 249 Ω || (249 Ω + 27.7 Ω) = 130 Ω. To reduce the additional high-frequency noise introduced by the resistor at the noninverting input, and power-supply feedback, RT is bypassed with a capacitor to ground. 6.8 µF + −VS Figure 76. Wideband, Inverting Gain Configuration In the inverting configuration, some key design considerations must be noted. One is that the gain resistor (Rg) becomes part of the signal channel input impedance. If the input impedance matching is desired (which is beneficial whenever the signal is coupled through a cable, twisted pair, long PC board trace, or other transmission line conductors), Rg may be set equal to the required termination value and Rf adjusted to give the desired gain. However, care must be taken when dealing with low inverting gains, as the resultant feedback resistor value can present a significant load to the amplifier output. For an inverting gain of 2, setting Rg to 49.9 Ω for input matching eliminates the need for RM but requires a 100-Ω feedback resistor. This has an advantage of the noise gain becoming equal to 2 for a 50-Ω source impedance—the same as the noninverting circuit in Figure 75. However, the amplifier output now sees the 100-Ω feedback resistor in parallel with the external load. To eliminate this excessive loading, it is preferable to increase both Rg and Rf, values, as shown in Figure 76, and then achieve the input matching impedance with a third resistor (RM) to ground. The total input impedance becomes the parallel combination of Rg and RM. The next major consideration is that the signal source impedance becomes part of the noise gain equation and hence influences the bandwidth. For example, the RM value combines in parallel with the external 50-Ω source impedance (at high frequencies), yielding an effective source impedance of 50 Ω || 61.9 Ω = 27.7 Ω. This impedance is then added in series with Rg for calculating the noise gain. The result is 1.9 for Figure 76, as opposed to the 1.8 if RM is eliminated. The bandwidth is lower for the gain of –2 circuit, Figure 76, (NG=+1.9) than for the gain of +2 circuit in Figure 75. SINGLE SUPPLY OPERATION The THS4271 is designed to operate from a single 5-V to 15-V power supply. When operating from a single power supply, care must be taken to ensure the input signal and amplifier are biased appropriately to allow for the maximum output voltage swing. The circuits shown in Figure 77 demonstrate methods to configure an amplifier in a manner conducive for single supply operation. +VS 50 Ω Source + VI 49.9 Ω RT THS4271 VO _ 499 Ω +VS 2 Rf Rg 249 Ω +VS 2 249 Ω Rf 249 Ω 50 Ω Source VI 61.9 Ω +VS 2 VS Rg 249 Ω RT _ THS4271 + VO 499 Ω +VS 2 Figure 77. DC-Coupled Single Supply Operation Saving Power With Power-Down Functionality and Setting Threshold Levels With the Reference Pin The THS4275 features a power-down pin (PD) which lowers the quiescent current from 22 mA down to 700 µA, ideal for reducing system power. The power-down pin of the amplifiers defaults to the positive supply voltage in the absence of an applied voltage, putting the amplifier in the power-on mode of operation. To turn off the amplifier in an effort to conserve power, the power-down pin can be driven towards the 19 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 negative rail. The threshold voltages for power-on and power-down are relative to the supply rails and given in the specification tables. Above the Enable Threshold Voltage, the device is on. Below the Disable Threshold Voltage, the device is off. Behavior in between these threshold voltages is not specified. Note that this power-down functionality is just that; the amplifier consumes less power in power-down mode. The power-down mode is not intended to provide a highimpedance output. In other words, the power-down functionality is not intended to allow use as a 3-state bus driver. When in power-down mode, the impedance looking back into the output of the amplifier is dominated by the feedback and gain setting resistors, but the output impedance of the device itself varies depending on the voltage applied to the outputs. The time delays associated with turning the device on and off are specified as the time it takes for the amplifier to reach 50% of the nominal quiescent current. The time delays are on the order of microseconds because the amplifier moves in and out of the linear mode of operation in these transitions. Power-Down Reference Pin Operation In addition to the power-down pin, the THS4275 also features a reference pin (REF) which allows the user to control the enable or disable power-down voltage levels applied to the PD pin. Operation of the reference pin as it relates to the power-down pin is described below. In most split-supply applications, the reference pin is connected to ground. In some cases, the user may want to connect it to the negative or positive supply rail. In either case, the user needs to be aware of the voltage level thresholds that apply to the power-down pin. The tables below show examples and illustrate the relationship between the reference voltage and the power-down thresholds. Note that in order to maintain these threshold levels, the reference pin can be any voltage between Vs− or GND up to Vs/2 (midrail). POWER-DOWN THRESHOLD VOLTAGE LEVELS (REF > MIDRAIL) SUPPLY VOLTAGE (V) ±5 5 REFERENCE PIN VOLTAGE (V) ENABLE LEVEL (V) DISABLE LEVEL (V) GND ≥ 1.8 ≤1 −2.5 ≥ −0.7 ≤ −1.5 −5 ≥ −3.2 ≤ −4 GND ≥ 1.8 ≤1 1 ≥ 2.8 ≤2 2.5 ≥ 4.3 ≤ 3.5 In the above table, the threshold levels are derived by the following equations: REF + 1.8 V for enable REF + 1 V for disable 20 ENABLE LEVEL (V) DISABLE LEVEL (V) Floating or 5 ≥4 ≤ 3.3 2.5 ≥ 1.5 ≤ 0.8 ±5 1 ≥0 ≤ −0.7 Floating or 5 ≥ 3.3 ≤ 3.3 4 ≥3 ≤ 2.3 3.5 ≥ 2.5 ≤ 1.8 5 In the above table, the threshold levels are derived by the following equations: REF − 1 V for enable REF − 1.7 V for disable Note that in order to maintain these threshold levels, the reference pin can be any voltage between (Vs+/2) + 1 V to Vs+. The recommended mode of operation is to tie the reference pin to midrail, thus setting the threshold levels to midrail +1 V and midrail +1.8 V. NO. OF CHANNELS PACKAGES Single (8-pin) THS4275D, THS4275DGN, and THS4275DRB Power Supply Decoupling Techniques and Recommendations Power supply decoupling is a critical aspect of any high-performance amplifier design process. Careful decoupling provides higher quality ac performance (most notably improved distortion performance). The following guidelines ensure the highest level of performance. 1. Place decoupling capacitors as close to the power supply inputs as possible, with the goal of minimizing the inductance of the path from ground to the power supply. 2. Placement priority should put the smallest valued capacitors closest to the device. 3. Use of solid power and ground planes is recommended to reduce the inductance along power supply return current paths, with the exception of the areas underneath the input and output pins. 4. Recommended values for power supply decoupling include a bulk decoupling capacitor (6.8 to 22 µF), a mid-range decoupling capacitor (0.1 µF) and a high frequency decoupling capacitor (1000 pF) for each supply. A 100-pF capacitor can be used across the supplies as well for extremely high frequency return currents, but often is not required. POWER-DOWN THRESHOLD VOLTAGE LEVELS (REF ≤ MIDRAIL) SUPPLY VOLTAGE (V) REFERENCE PIN VOLTAGE (V) www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 APPLICATION CIRCUITS Driving an Analog-to-Digital Converter With the THS4271 The THS4271 can be used to drive high-performance analog-to-digital converters. Two example circuits are presented below. The first circuit uses a wideband transformer to convert a single-ended input signal into a differential signal. The differential signal is then amplified and filtered by two THS4271 amplifiers. This circuit provides low intermodulation distortion, suppressed even-order distortion, 14 dB of voltage gain, a 50-Ω input impedance, and a single-pole filter at 100 MHz. For applications without signal content at dc, this method of driving ADCs can be very useful. Where dc information content is required, the THS4500 family of fully differential amplifiers may be applicable. _ −5 V 249 Ω 24.9 Ω ADS5422 22 pF 49.9 Ω RT RISO 0.1 µF THS4271 _ −5 V IN 68 pf 16.5 Ω ADS807 12-Bit, CM 53 Msps IN Rf 1.82 kΩ 249 Ω 0.1 µF 249 Ω Rg NOTE: For best performance, high-speed ADCs should be driven differentially. See the THS4500 family of devices for more information. Figure 79. Driving an ADC With a Single-Ended Input 100 Ω 3.3 V 3.3 V 14-Bit, 62 Msps 22 pF 249 Ω 100 Ω 100 Ω 24.9 Ω 249 Ω _ THS4271 VCM + VI Two example circuits are presented here showing the THS4271 buffering the output of a digital-to-analog converter. The first circuit performs a differential to single-ended conversion with the THS4271 configured as a difference amplifier. The difference amplifier can double as the termination mechanism for the DAC outputs as well. + THS4271 50 Ω (1:4 Ω) Source 1:2 100 Ω +5 V Using the THS4271 as a DAC Output Buffer 5V VCM 50 Ω Source + +5 V DAC5675 14-Bit, 400 MSps 249 Ω 124 Ω _ 49.9 Ω RF THS4271 + 249 Ω −5 V 249 Ω LO Figure 78. A Linear, Low Noise, High Gain ADC Preamplifier The second circuit depicts single-ended ADC drive. While not recommended for optimum performance using converters with differential inputs, satisfactory performance can sometimes be achieved with single-ended input drive. An example circuit is shown here for reference. Figure 80. Differential to Single-Ended Conversion of a High-Speed DAC Output For cases where a differential signaling path is desirable, a pair of THS4271 amplifiers can be used as output buffers. The circuit depicts differential drive into a mixer’s IF inputs, coupled with additional signal gain and filtering. 21 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 100 Ω THS4271 VI+ + 3.3 V 3.3 V + 49.9 Ω VO+ _ _ 100 Ω 100 Ω CF 1 nF 249 Ω 499 Ω 1 nF IF+ DAC5675 249 Ω 100 Ω 249 Ω 14-Bit, 400 MSps 249 Ω 49.9 Ω 249 Ω 49.9 Ω 100 Ω 249 Ω RF(out) _ 49.9 Ω IF− 1 nF 1 nF _ VI− CF VO− 100 Ω + Figure 83. A High Input Impedance, Low Noise, Differential Receiver + THS4271 Figure 81. Differential Mixer Drive Circuit Using the DAC5675 and the THS4271 A modification on this circuit to include a difference amplifier turns this circuit into a high-speed instrumentation amplifier, as shown in Figure 84. 100 Ω Active Filtering With the THS4271 + VI− Rg2 Rf2 Rg2 THS4271 THS4271 _ High-frequency active filtering with the THS4271 is achievable due to the amplifier’s high slew-rate, wide bandwidth, and voltage feedback architecture. Several options are available for high-pass, low-pass, bandpass, and bandstop filters of varying orders. A simple two-pole low pass filter is presented here as an example, with two poles at 100 MHz. Rf1 Rg1 _ THS4271 100 Ω 6.8 pF _ Rf1 49.9 Ω VO + 49.9 Ω + Rf2 VI+ 50 Ω Source 249 Ω VI 249 Ω 61.9 Ω Figure 84. A High-Speed Instrumentation Amplifier 5V _ 49.9 Ω THS4271 + VO 33 pF ǒ Ǔ ǒ Ǔ R f2 2R f1 ǒ VO + 1 1 ) V i)–V i–Ǔ 2 Rg1 Rg2 (1) −5 V Figure 82. A Two-Pole Active Filter With Two Poles Between 90 MHz and 100 MHz A Low-Noise Receiver With the THS4271 A combination of two THS4271 amplifiers can create a high-speed, low-distortion, low-noise differential receiver circuit as depicted in Figure 83. With both amplifiers operating in the noninverting mode of operation, the circuit presents a high load impedance to the source. The designer has the option of controlling the impedance through termination resistors if a matched termination impedance is desired. 22 THEORY AND GUIDELINES Distortion Performance The THS4271 provides excellent distortion performance into a 150-Ω load. Relative to alternative solutions, it provides exceptional performance into lighter loads, as well as exceptional performance on a single 5-V supply. Generally, until the fundamental signal reaches very high frequency or power levels, the 2nd harmonic dominates the total harmonic distortion with a negligible 3rd harmonic component. Focusing then on the 2nd harmonic, increasing the load impedance improves distortion www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 directly. The total load includes the feedback network; in the noninverting configuration (Figure 75) this is the sum of Rf and Rg, while in the inverting configuration (Figure 76), only Rf needs to be included in parallel with the actual load. LINEARITY: DEFINITIONS, TERMINOLOGY, CIRCUIT TECHNIQUES, AND DESIGN TRADEOFFS The THS4271 features excellent distortion performance for monolithic operational amplifiers. This section focuses on the fundamentals of distortion, circuit techniques for reducing nonlinearity, and methods for equating distortion of operational amplifiers to desired linearity specifications in RF receiver chains. Amplifiers are generally thought of as linear devices. The output of an amplifier is a linearly scaled version of the input signal applied to it. However, amplifier transfer functions are nonlinear. Minimizing amplifier nonlinearity is a primary design goal in many applications. Intercept points are specifications long used as key design criteria in the RF communications world as a metric for the intermodulation distortion performance of a device in the signal chain (e.g., amplifiers, mixers, etc.). Use of the intercept point, rather than strictly the intermodulation distortion, allows simpler system-level calculations. Intercept points, like noise figures, can be easily cascaded back and forth through a signal chain to determine the overall receiver chain’s intermodulation distortion performance. The relationship between intermodulation distortion and intercept point is depicted in Figure 85 and Figure 86. Power PO 1X OIP3 PO IMD3 ∆fc = fc − f1 ∆fc = f2 − fc 3X IMD3 = PS − PO Figure 86 Due to the intercept point’s ease of use in system level calculations for receiver chains, it has become the specification of choice for guiding distortion-related design decisions. Traditionally, these systems use primarily class-A, single-ended RF amplifiers as gain blocks. These RF amplifiers are typically designed to operate in a 50-Ω environment. Giving intercept points in dBm, implies an associated impedance (50 Ω). However, with an operational amplifier, the output does not require termination as an RF amplifier would. Because closed-loop amplifiers deliver signals to their outputs regardless of the impedance present, it is important to comprehend this when evaluating the intercept point of an operational amplifier. The THS4271 yields optimum distortion performance when loaded with 150 Ω to 1 kΩ, very similar to the input impedance of an analog-to-digital converter over its input frequency band. The discontinuity between open-loop, class-A amplifiers and closed-loop, class-AB amplifiers becomes apparent when comparing the intercept points of the two types of devices. Equations 1 and 2 gives the definition of an intercept point, relative to the intermodulation distortion. PS f1 fc f2 PIN (dBm) PS OIP 3 + P O ) fc − 3∆f IIP3 As a result, terminating the input of the ADC to 50 Ω can actually be detrimental to systems performance. PO PS POUT (dBm) fc + 3∆f f − Frequency − MHz Figure 85 ǒ P O + 10 log ǒŤIMD2 ŤǓ where 3 Ǔ V 2P 2RL 0.001 (2) (3) NOTE: PO is the output power of a single tone, RL is the load resistance, and VP is the peak voltage for a single tone. 23 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 NOISE ANALYSIS Driving Capacitive Loads High slew rate, unity gain stable, voltage-feedback operational amplifiers usually achieve their slew rate at the expense of a higher input noise voltage. The 3 nV/√Hz input voltage noise for the THS4271 and THS4275 is, however, much lower than comparable amplifiers. The input-referred voltage noise, and the two input-referred current noise terms (3 pA/√Hz), combine to give low output noise under a wide variety of operating conditions. Figure 87 shows the amplifier noise analysis model with all the noise terms included. In this model, all noise terms are taken to be noise voltage or current density terms in either nV/√Hz or pA/√Hz. One of the most demanding, and yet very common, load conditions for an op amp is capacitive loading. Often, the capacitive load is the input of an A/D converter, including additional external capacitance, which may be recommended to improve A/D linearity. A high-speed, high open-loop gain amplifier like the THS4271 can be very susceptible to decreased stability and closed-loop response peaking when a capacitive load is placed directly on the output pin. When the amplifier’s open-loop output resistance is considered, this capacitive load introduces an additional pole in the signal path that can decrease the phase margin. When the primary considerations are frequency response flatness, pulse response fidelity, or distortion, the simplest and most effective solution is to isolate the capacitive load from the feedback loop by inserting a series isolation resistor between the amplifier output and the capacitive load. This does not eliminate the pole from the loop response, but rather shifts it and adds a zero at a higher frequency. The additional zero acts to cancel the phase lag from the capacitive load pole, thus increasing the phase margin and improving stability. THS4271/THS4275 ENI + RS IBN ERS 4kTRS 4kT Rg EO _ Rf Rg IBI ERF 4kTRf The Typical Characteristics show the recommended isolation resistor vs capacitive load and the resulting frequency response at the load. Parasitic capacitive loads Figure 87. Noise Analysis Model greater than 2 pF can begin to degrade the performance of the THS4271. Long PC board traces, unmatched The total output shot noise voltage can be computed as the cables, and connections to multiple devices can easily square of all square output noise voltage contributors. cause this value to be exceeded. Always consider this Equation 3 shows the general form for the output noise effect carefully, and add the recommended series resistor voltage using the terms shown in Figure 87: as close as possible to the THS4271 output pin (see Board (4) 2 2 Layout Guidelines). EO + ENI 2 ) ǒIBNRSǓ ) 4kTR S NG 2 ) ǒIBIRfǓ ) 4kTRfNG 4kT = 1.6E−20J at 290K Ǹǒ Ǔ Dividing this expression by the noise gain (NG=(1+ Rf/Rg)) gives the equivalent input-referred spot noise voltage at the noninverting input, as shown in Equation 4: EO + Ǹ E NI 2 ǒ Ǔ ) 4kTR NG 2 I R ) ǒI BNRSǓ ) 4kTR S ) BI f NG 2 f Evaluation of these two equations for the circuit and component values shown in Figure 75 will give a total output spot noise voltage of 12.2 nV/√Hz and a total equivalent input spot noise voltage of 6.2 nV/√Hz. This includes the noise added by the resistors. This total input-referred spot noise voltage is not much higher than the 3 nV/√Hz specification for the amplifier voltage noise alone. 24 The criterion for setting this R(ISO) resistor is a maximum bandwidth, flat frequency response at the load. For a gain of +2, the frequency response at the output pin is already slightly peaked without the capacitive load, requiring (5) relatively high values of R(ISO) to flatten the response at the load. Increasing the noise gain also reduces the peaking. www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 FREQUENCY RESPONSE vs CAPACITIVE LOAD Again, keep their leads and PC board trace length as short as possible. Never use wire-wound type resistors in a high frequency application. Since the output pin and inverting input pin are the most sensitive to parasitic capacitance, always position the feedback and series output resistor, if any, as close as possible to the output pin. Other network components, such as noninverting input-termination resistors, should also be placed close to the package. Where double-side component mounting is allowed, place the feedback resistor directly under the package on the other side of the board between the output and inverting input pins. Even with a low parasitic capacitance shunting the external resistors, excessively high resistor values can create significant time constants that can degrade performance. Good axial metal-film or surface-mount resistors have approximately 0.2 pF in shunt with the resistor. For resistor values > 2 kΩ, this parasitic capacitance can add a pole and/or a zero below 400-MHz that can effect circuit operation. Keep resistor values as low as possible, consistent with load driving considerations. A good starting point for design is to set the Rf to 249-Ω for low-gain, noninverting applications. Doing this automatically keeps the resistor noise terms low, and minimizes the effect of their parasitic capacitance. 0.5 Normalized Gain − dB 0 −0.5 −1 −1.5 R(ISO) = 25 Ω CL = 10 pF R(ISO) = 15 Ω CL = 100 pF R(ISO) = 10 Ω CL = 50 pF −2 −2.5 RL = 499 Ω VS =±5 V −3 1M 10 M 100 M f − Frequency − Hz Figure 88. Isolation Resistor Diagram BOARD LAYOUT Achieving optimum performance with a high frequency amplifier like the THS4271 requires careful attention to board layout parasitics and external component types. Recommendations that optimize performance include: 1. Minimize parasitic capacitance to any ac ground for all of the signal I/O pins. Parasitic capacitance on the output and inverting input pins can cause instability: on the noninverting input, it can react with the source impedance to cause unintentional band limiting. To reduce unwanted capacitance, a window around the signal I/O pins should be opened in all of the ground and power planes around those pins. Otherwise, ground and power planes should be unbroken elsewhere on the board. 2. Minimize the distance (< 0.25”) from the power supply pins to high frequency 0.1-µF de-coupling capacitors. At the device pins, the ground and power plane layout should not be in close proximity to the signal I/O pins. Avoid narrow power and ground traces to minimize inductance between the pins and the decoupling capacitors. The power supply connections should always be decoupled with these capacitors. Larger (2.2-µF to 6.8-µF) decoupling capacitors, effective at lower frequency, should also be used on the main supply pins. These may be placed somewhat farther from the device and may be shared among several devices in the same area of the PC board. 3. Careful selection and placement of external components preserves the high frequency performance of the THS4271. Resistors should be a very low reactance type. Surface-mount resistors work best and allow a tighter overall layout. Metal-film and carbon composition, axially-leaded resistors can also provide good high frequency performance. 4. Connections to other wideband devices on the board may be made with short direct traces or through onboard transmission lines. For short connections, consider the trace and the input to the next device as a lumped capacitive load. Relatively wide traces (50 mils to 100 mils) should be used, preferably with ground and power planes opened up around them. Estimate the total capacitive load and set RISO from the plot of recommended RISO vs capacitive load. Low parasitic capacitive loads (<4 pF) may not need an R(ISO), since the THS4271 is nominally compensated to operate with a 2-pF parasitic load. Higher parasitic capacitive loads without an R(ISO) are allowed as the signal gain increases (increasing the unloaded phase margin). If a long trace is required, and the 6-dB signal loss intrinsic to a doubly-terminated transmission line is acceptable, implement a matched impedance transmission line using microstrip or stripline techniques (consult an ECL design handbook for microstrip and stripline layout techniques). A 50-Ω environment is normally not necessary onboard, and in fact, a higher impedance environment improves distortion as shown in the distortion versus load plots. With a characteristic board trace impedance defined based on board material and trace dimensions, a matching series resistor into the trace from the output of the THS4271 is used as well as a terminating shunt resistor at the input of the destination device. Remember also that the terminating impedance is the 25 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 parallel combination of the shunt resistor and the input impedance of the destination device: this total effective impedance should be set to match the trace impedance. If the 6-dB attenuation of a doubly terminated transmission line is unacceptable, a long trace can be series-terminated at the source end only. Treat the trace as a capacitive load in this case and set the series resistor value as shown in the plot of R(ISO) vs capacitive load. This does not preserve signal integrity or a doubly-terminated line. If the input impedance of the destination device is low, there is some signal attenuation due to the voltage divider formed by the series output into the terminating impedance. DIE Side View (a) Thermal Pad DIE End View (b) Bottom View (c) Figure 89. Views of Thermally Enhanced Package Although there are many ways to properly heatsink the PowerPAD package, the following steps illustrate the recommended approach. ÓÓÓ ÓÓÓ ÓÓ ÓÓÓ ÓÓÓÓÓÓ ÓÓ ÓÓÓÓÓ ÓÓÓ ÓÓ Single or Dual 5. Socketing a high speed part like the THS4271 is not recommended. The additional lead length and pin-to-pin capacitance introduced by the socket can create a troublesome parasitic network which can make it almost impossible to achieve a smooth, stable frequency response. Best results are obtained by soldering the THS4271 onto the board. 68 Mils x 70 Mils (Via diameter = 13mils) Figure 90. PowerPAD PCB Etch and Via Pattern PowerPAD PCB LAYOUT CONSIDERATIONS PowerPAD DESIGN CONSIDERATIONS 1. Prepare the PCB with a top side etch pattern as shown in Figure 90. There should be etch for the leads as well as etch for the thermal pad. The THS4271 and THS4275 are available in a thermally-enhanced PowerPAD family of packages. These packages are constructed using a downset leadframe upon which the die is mounted [see Figure 89(a) and Figure 89(b)]. This arrangement results in the lead frame being exposed as a thermal pad on the underside of the package [see Figure 89(c)]. Because this thermal pad has direct thermal contact with the die, excellent thermal performance can be achieved by providing a good thermal path away from the thermal pad. 2. Place five holes in the area of the thermal pad. The holes should be 13 mils in diameter. Keep them small so that solder wicking through the holes is not a problem during reflow. 3. Additional vias may be placed anywhere along the thermal plane outside of the thermal pad area. They help dissipate the heat generated by the THS4271 and THS4275 IC. These additional vias may be larger than the 13-mil diameter vias directly under the thermal pad. They can be larger because they are not in the thermal pad area to be soldered, so that wicking is not a problem. 4. Connect all holes to the internal ground plane. 5. When connecting these holes to the ground plane, do not use the typical web or spoke via connection methodology. Web connections have a high thermal resistance connection that is useful for slowing the heat transfer during soldering operations. This resistance makes the soldering of vias that have plane connections easier. In this application, however, low thermal resistance is desired for the most efficient heat transfer. Therefore, the holes under the THS4271 and THS4275 PowerPAD package should make their connection to the internal ground plane, with a complete connection around the entire circumference of the plated-through hole. The PowerPAD package allows both assembly and thermal management in one manufacturing operation. During the surface-mount solder operation (when the leads are being soldered), the thermal pad can also be soldered to a copper area underneath the package. Through the use of thermal paths within this copper area, heat can be conducted away from the package into either a ground plane or other heat dissipating device. The PowerPAD package represents a breakthrough in combining the small area and ease of assembly of surface mount with the heretofore awkward mechanical methods of heatsinking. 26 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 7. 8. The top-side solder mask should leave the terminals of the package and the thermal pad area with its five holes exposed. The bottom-side solder mask should cover the five holes of the thermal pad area. This prevents solder from being pulled away from the thermal pad area during the reflow process. Apply solder paste to the exposed thermal pad area and all of the IC terminals. With these preparatory steps in place, the IC is simply placed in position and run through the solder reflow operation as any standard surface-mount component. This results in a part that is properly installed. For a given θJA , the maximum power dissipation is shown in Figure 91 and is calculated by the equation 5: PD + Tmax * T A q JA (6) where: PD = Maximum power dissipation of THS4271 (watts) TMAX = Absolute maximum junction temperature (150°C) TA = Free-ambient temperature (°C) θJA = θJC + θCA θJC = Thermal coefficient from junction to the case θCA = Thermal coefficient from the case to ambient air (°C/W). The next consideration is the package constraints. The two sources of heat within an amplifier are quiescent power and output power. The designer should never forget about the quiescent heat generated within the device, especially multi-amplifier devices. Because these devices have linear output stages (Class AB), most of the heat dissipation is at low output voltages with high output currents. The other key factor when dealing with power dissipation is how the devices are mounted on the PCB. The PowerPAD devices are extremely useful for heat dissipation. But, the device should always be soldered to a copper plane to fully use the heat dissipation properties of the PowerPAD. The SOIC package, on the other hand, is highly dependent on how it is mounted on the PCB. As more trace and copper area is placed around the device, θJA decreases and the heat dissipation capability increases. For a single package, the sum of the RMS output currents and voltages should be used to choose the proper package. THERMAL ANALYSIS The THS4271 device does not incorporate automatic thermal shutoff protection, so the designer must take care to ensure that the design does not violate the absolute maximum junction temperature of the device. Failure may result if the absolute maximum junction temperature of 150_ C is exceeded. The thermal characteristics of the device are dictated by the package and the PC board. Maximum power dissipation for a given package can be calculated using the following formula. P Dmax + (7) Tmax–T A q JA where: PDmax is the maximum power dissipation in the amplifier (W). Tmax is the absolute maximum junction temperature (°C). TA is the ambient temperature (°C). θJA = θJC + θCA θJC is the thermal coefficient from the silicon junctions to the case (°C/W). θCA is the thermal coefficient from the case to ambient air (°C/W). For systems where heat dissipation is more critical, the THS4271 is offered in an 8-pin MSOP with PowerPAD. The thermal coefficient for the MSOP PowerPAD package is substantially improved over the traditional SOIC. Maximum power dissipation levels are depicted in the graph for the two packages. The data for the DGN package assumes a board layout that follows the PowerPAD layout guidelines referenced above and detailed in the PowerPAD application notes in the Additional Reference Material section at the end of the data sheet. 3.5 PD − Maximum Power Dissipation − W 6. 8-Pin DGN Package 3 2.5 2 8-Pin D Package 1.5 1 0.5 0 −40 −20 0 20 40 60 TA − Ambient Temperature − °C 80 θJA = 170°C/W for 8-Pin SOIC (D) θJA = 58.4°C/W for 8-Pin MSOP (DGN) TJ = 150°C, No Airflow Figure 91. Maximum Power Dissipation vs Ambient Temperature When determining whether or not the device satisfies the maximum power dissipation requirement, it is important to consider not only quiescent power dissipation, but also dynamic power dissipation. Often maximum power is difficult to quantify because the signal pattern is inconsistent, but an estimate of the RMS power dissipation can provide visibility into a possible problem. 27 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 Performance vs Package Options The THS4271 and THS4275 are offered in different package options. However, performance may be limited due to package parasitics and lead inductance in some packages. In order to achieve maximum performance of the THS4271 and THS4275, Texas Instruments recommends using the leadless MSOP (DRB) or MSOP (DGN) packages, in addition to proper high-speed PCB layout. Figure 92 shows the unity gain frequency response of the THS4271 using the leadless MSOP, MSOP, and SOIC package for comparison. Using the THS4271 and THS4275 in a unity gain with the SOIC package may result in the device becoming unstable. In higher gain configurations, this effect is mitigated by the reduced bandwidth. As such, the SOIC is suitable for application with gains equal to or higher than +2 V/V or (−1 V/V). 20 18 _ Normalized Gain − dB 16 15 13 SOIC, Rf = 0 Ω Rf Rf = 50 Ω Rf + 150 Ω 49.9 Ω 9 Rf = 0 Ω Rf = 100 Ω 7 Rf = 150 Ω 5 3 1 −1 VIN = 100 mVPP VS = ±5 V −5 10M 100M f − Frequency − Hz SOIC, Rf = 100 Ω 1G Figure 93. Frequency Response vs Feedback Resistor Using the EDGE #6439527 EVM 10 SOIC, Rf = 200 Ω 8 11 _ −3 150 Ω 49.9 Ω 12 4 17 + 14 6 The THS4271/THS4275 EVM board shown in Figure 96 through Figure 99 is designed to accommodate different gain configurations. Its default component values are set to give a gain of 2. The EVM can be configured in a gain of +1; however, it is strongly not recommended. Evaluating the THS4271/THS4275 in a gain of 1 using this EVM may cause the part to become unstable. The stability of the device can be controlled by adding a large resistor in the feedback path, the performance is sacrificed. Figure 93 shows the small signal frequency response of the THS4271 with different feedback resistors in the feedback path. Figure 94 is the small frequency response of the THS4271 using the gain of 1 EVM. Small Signal Gain − dB DESIGN TOOLS Leadless MSOP, & MSOP Rf = 0 Ω 2 4 0 −4 VIN = 100 mVPP VS =±5 V 10 M 3 100 M 1G f − Frequency − Hz Figure 92. Effects of Unity Gain Frequency Response for Differential Packages Evaluation Fixtures, Spice Models, and Applications Support Small Signal Gain − dB −2 2 28 150 Ω 49.9 Ω 1 0 −1 −2 −3 Texas Instruments is committed to providing its customers with the highest quality of applications support. To support this goal, evaluation boards have been developed for the THS4271 operational amplifier. Three evaluation boards are available: one THS4271 and one THS4275, both are configurable for different gains, and a third for a gain of +1 (THS4271 only). These boards are easy to use, allowing for straightforward evaluation of the device. These evaluation boards can be ordered through the Texas Instruments web site, www.ti.com, or through your local Texas Instruments sales representative. Schematics for the evaluation boards are shown below. _ + Gain = 1 RL = 150 Ω VO = 100 mVPP VS = ±5 V −4 100 k 1M 10 M 100 M f − Frequency − Hz 1G 10 G Figure 94. Frequency Response Using the EDGE # 6443547 G = +1 EVM The peaking in the frequency response is due to the lead inductance in the feedback path. Each pad and trace on a PCB has an inductance associated with it, which in conjunction with the inductance associated with the package may cause peaking in the frequency response, causing the device to become unstable. www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 In order to achieve the maximum performance of the device, PCB layout is very critical. Texas Instruments has developed an EVM for the evaluation of the THS4271 in a gain of 1. The EVM is shown in Figure 101 through Figure 104. This EVM is designed to minimize peaking in the unity gain configuration. Minimizing the inductance in the feedback path is critical for reducing the peaking of the frequency response in unity gain. The recommended maximum inductance allowed in the feedback path is 4 nH. This can be calculated by using Equation 8. ƪ L(nH) + Kȏ ln ƫ (8) 2ȏ ) 0.223 W ) T ) 0.5 ȏ W)T where: W = Width of trace in inches. ȏ = Length of the trace in inches. T = Thickness of the trace in inches. K = 5.08 for dimensions in inches, and K = 2 for dimensions in cm. Vs+ J9 Power Down R8 Figure 96. THS4271/THS4275 EVM Board Layout (Top Layer) C8 R9 R5 Vs − Vs+ 7 8 2 _ R3 J1 Vin − U1 R6 6 J4 Vout 3 + R2 R7 4 1 Vs − J2 Vin+ J8 Power Down Ref C7 R1 R4 J7 VS− J6 GND J5 VS+ TP1 FB1 FB2 VS− C5 C6 VS+ C1 + C2 + C3 Figure 95. THS4271/THS4275 EVM Circuit Configuration C4 Figure 97. THS4271/THS4275 EVM Board Layout (Second Layer, Ground) 29 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 Vs+ 7 8 2 _ U1 R6 6 J4 Vout 3 + R7 4 1 J2 Vin+ Vs − R4 J7 VS− J6 GND J5 VS+ TP1 FB1 FB2 VS− C5 30 C6 VS+ C1 + C2 + C3 Figure 98. THS4271/THS4275 EVM Board Layout (Third Layer, Power) Figure 100. THS4271 Unity Gain EVM Circuit Configuration Figure 99. THS4271/THS4275 EVM Board Layout (Bottom Layer) Figure 101. THS4271 Unity Gain EVM Board Layout (Top Layer) C4 www.ti.com SLOS397E − JULY 2002 − REVISED JANUARY 2004 Figure 104. THS4271 Unity Gain EVM Board Layout (Bottom Layer) Figure 102. THS4271 Unity Gain EVM Board Layout (Second Layer, Ground) Computer simulation of circuit performance using SPICE is often useful when analyzing the performance of analog circuits and systems. This is particularly true for video and RF amplifier circuits where parasitic capacitance and inductance can have a major effect on circuit performance. A SPICE model for the THS4271 is available through either the Texas Instruments web site (www.ti.com). The PIC is also available for design assistance and detailed product information. These models do a good job of predicting small-signal ac and transient performance under a wide variety of operating conditions. They are not intended to model the distortion characteristics of the amplifier, nor do they attempt to distinguish between the package types in their small-signal ac performance. Detailed information about what is and is not modeled is contained in the model file itself. ADDITIONAL REFERENCE MATERIAL Figure 103. THS4271 Unity Gain EVM Board Layout (Third Layer, Power) D PowerPAD Made Easy, application brief (SLMA004) D PowerPAD Thermally Enhanced Package, technical brief (SLMA002) 31 PACKAGE OPTION ADDENDUM www.ti.com 8-Aug-2005 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Drawing Pins Package Eco Plan (2) Qty THS4271D ACTIVE SOIC D 8 75 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4271DG4 ACTIVE SOIC D 8 75 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4271DGK ACTIVE MSOP DGK 8 100 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4271DGKR ACTIVE MSOP DGK 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4271DGKRG4 ACTIVE MSOP DGK 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4271DGN ACTIVE MSOPPower PAD DGN 8 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4271DGNR ACTIVE MSOPPower PAD DGN 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4271DGNRG4 ACTIVE MSOPPower PAD DGN 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4271DR ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4271DRBR ACTIVE SON DRB 8 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR THS4271DRBT ACTIVE SON DRB 8 250 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR THS4275D ACTIVE SOIC D 8 75 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4275DG4 ACTIVE SOIC D 8 75 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4275DGK ACTIVE MSOP DGK 8 100 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4275DGKR ACTIVE MSOP DGK 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4275DGKRG4 ACTIVE MSOP DGK 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4275DGN ACTIVE MSOPPower PAD DGN 8 80 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4275DGNG4 ACTIVE MSOPPower PAD DGN 8 80 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4275DGNR ACTIVE MSOPPower PAD DGN 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4275DR ACTIVE SOIC D 8 2500 Green (RoHS & no Sb/Br) CU NIPDAU Level-1-260C-UNLIM THS4275DRBR ACTIVE SON DRB 8 3000 Green (RoHS & no Sb/Br) CU NIPDAU Level-2-260C-1 YEAR THS4275DRBT ACTIVE SON DRB 8 250 CU NIPDAU Level-2-260C-1 YEAR 80 Addendum-Page 1 Green (RoHS & no Sb/Br) Lead/Ball Finish MSL Peak Temp (3) PACKAGE OPTION ADDENDUM www.ti.com 8-Aug-2005 Orderable Device Status (1) Package Type Package Drawing THS4275DRG4 ACTIVE SOIC D Pins Package Eco Plan (2) Qty 8 2500 Green (RoHS & no Sb/Br) Lead/Ball Finish CU NIPDAU MSL Peak Temp (3) Level-1-260C-UNLIM (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) 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. 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. 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. 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