LMV881EVAL/NOPB

Dec 2, 2011 Rev - 0.0.2 LMV881 µLLP Evaluation Board Users' Guide (Board shown with optional components installed) 2011 Texas Instruments, Inc. 1 http://www.ti.com section), the RR1 and RR2 bias resistors can provide the reference voltage for this point. Overview For lowest noise on a directly “grounded” positive input, RB should be shorted. The LMV881 Evaluation Board is designed to aid in the evaluation and testing of the LMV881 micro-LLP operational amplifier. + V CIP Many basic functions and filters can be implemented by placing the appropriate resistors or capacitors on the appropriate pads. VIN + AMP The circuits can be powered with single or dual supplies. V VOUT - + RB 1. Hardware Setup RR1 RF 1.1. Component Notation CB While the components are annotated with “R‟s” or “C‟s”, the mounting pads are the same size, so either R‟s or C‟s can be placed on the pads – depending on the circuit requirements. RR2 RG Short R8, R6, C2, C4 The pads are large enough to accommodate 1206 though 0602 surface mount devices. Figure 2. Single Supply Reference Divider 1.2. Power For the circuit in Single Supply Reference DividerFigure 2, the AC input impedance is equal to RB. Power is applied to the points labeled V−, GND, and V+. 1.5. Shutdown If a single supply is used, then V− should be connected to GND. It is recommended to short C3 and C4 to tie ground to the Vline. The LMP881 has shutdown with output clamping feature. The output will be internally connected to V- during shutdown. 1.3. Supply Bypassing The LMV881 will be in shutdown mode when the SD pin is below 0.68V. RPU and RPD are optional and provide for adding pullup, pull-down or voltage divider resistors. C1 and C2, and C3 and C4 (located rear of board), provide power supply bypassing. The shutdown input does not have internal pullup resistors and should not be left floating. Recommended values are 2.2uF to 33uF for C1 and C2, and 0.1uF for C3 and C4. RPU can be used to pull-up the shutdown pin to V+. If shutdown is not required, place a short across RPU. 1.4. Reference Voltage and Single Supplies The RR1 and RR2 resistor divider string can be used to generate V+/2 or any other required bias voltage from the V+ and Vsupply lines. CB is provided for filtering and /or AC grounding of the bias point. RPD can be used as a pull-down or line termination resistor for the shutdown pin. RPU and RPD can be used together to create a voltage divider to create a precise shutdown voltage if needed. + V 2. Basic Circuit Configurations CIP VIN + AMP V VOUT The following section shows how to configure the board for various basic amplifer configurations. Specific details of the circuit topology are available elsewhere and not covered here. - + RB - V RR1 Circuits will depict the split supply application for simplicity. Circuits can also be used in single-supply applications by adding the reference voltage dividers or an external reference voltage. See the Reference Voltage section for more biasing details. RF CB RR2 V RG - To reduce clutter, the schematics only show the parts used in the circuit. The text below the schematic will specify which component pads should be shorted. All other components not listed should have their pads left open. Short R8, R6 Figure 1. Split Supply Reference Divider Single-supply operation requires the generation of this virtual ground, usually at a voltage equal to V+/2. For single supply circuits where the positive input is grounded directly (as in the multiple feedback filter circuits in the next 2 http://www.ti.com 2.1. Non-Inverting Amplifer 2.4. Single Stage Differential Amplifer C7 RF R5 RF ROUT IN- - IN+ + VOUT R9 R5 R6 ROUT - IN- RB VOUT RIN R7 + CIN, CIP, R8, R9, CB = 0 (SHORT) CIN, RB, CB = 0 (SHORT) Figure 6. Differential to Single Ended Converter Figure 3. Non-Inverting Amplifer R12 can be used as a differential termination across the input terminals, if required. 2.2. Inverting Amplifer 3. Active Filter Configurations ROUT + Both Multiple Feedback and Sallen-Key filters of up to 2 poles can be built on this evaluation board. VOUT - For assistance designing a filter, see the WEBENCH® tool at http://www.national.com/filters or the TI FilterPro software from http://www.ti.com/tool/filterpro. INRTN R5 RF Note that the ground plane has been removed under the input circuitry area to reduce the de-tuning effects of stray capacitance. This should be considered in your final design. CIN, R9, RB, CB = 0 (SHORT) Figure 4. Inverting Amplifer 3.1. Sallen-Key Low-Pass Filter 2.3. Transimpedance (I to V) Amplifer C6 CF R8 RF RTP IN- - R6 ROUT + IN+ RB VOUT - ROUT VOUT + RG RF CB, CIP = 0 (SHORT) CIN, R9, R5, RB, CB = 0 (SHORT) Figure 7. Sallen-Key Low Pass Filter Figure 5. Transimpedance Amplifer CF is generally required for stability in transimpedance applications. See application note AN-1803 for more details. 3 http://www.ti.com 3.2. Multiple Feedback Low Pass Filter 3.5. Sallen-Key Band Pass Filter C7 C6 CF R8 R6 R9 RTP R5 C5 RB ROUT - IN- R7 + IN+ VOUT - VOUT + R7 RIN RG CIN, RB, CB = 0 (SHORT) CIP, CB = 0 (SHORT) Figure 8. Multiple Feedback Low Pass Filter Figure 11. Sallen-Key Band Pass Filter 3.3. Sallen Key High-Pass Filter 3.6. Multiple Feedback Band-Pass Filter C6 R8 RF C7 R6 RF ROUT + IN+ VOUT RTP RB R9 R5 - IN- ROUT VOUT RIN CIP, CB, RF = 0 (SHORT) R7 + Figure 9. Sallen-Key High-Pass Filter CIN, RB, CB = 0 (SHORT) 3.4. Multiple Feedback High Pass Filter Figure 12. Multiple Feedback Band Pass Filter C7 RF R9 R5 - IN- ROUT VOUT RTN R7 + CIN, RB, CB = 0 (SHORT) Figure 10. Multiple Feedback High Pass Filter 4 http://www.ti.com 4. LMV881 Evaluation Board Schematic SD V + RPU RPD + V + C1 C3 SD GND + C2 C4 C6 + V - - V TP10 VREF V RR1 + CB RR2 - RB V CIP R8 R6 + IN+ RTP R10 + V C5 1 3 DUT - R9 COUT ROUT 5 2 R7 CIN 4 + R12 GND 6 + V R5 - OUT RL CL SD RF + IN- GND CF RTN R11 RG C7 Figure 13. Demo Board Schematic 5 http://www.ti.com 5. Bill of Materials Designator Description Manufacturer PartNumber C5, C6, CF, CL, R5, R6, R7, R8, R9, R10, R11, R12, RB, RF, RG, RL, ROUT, RPD, RPU, RR1, RR2, RTN, RTP, CB, CIN, CIP, COUT Customer Defined Components C1, C2 CAP, TANT, 33uF, 10V, +/-10%, 3528-21 SMD Vishay-Sprague 293D336X9010B2TE3 C3, C4 CAP, CERM, 0.1uF, 16V, +/10%, X7R, 0603 MuRata GRM188R71C104KA01D DUT LMV881 23MHz OpAmp with Shutdown National Semiconductor LMV881LE H1, H2, H5, H6 Standoff, Hex, 0.5"L #4-40 Nylon Keystone 1902C H3, H4, H7, H8 Machine Screw, Round, #4-40 x 1/4, Nylon, Philips panhead B&F Fastener Supply NY PMS 440 0025 PH TP1, TP2, TP3, TP4, TP5, TP6, TP7, TP8, TP9, TP10 Terminal, Turret, TH, Double Keystone 1502-2 „* = Optional – not stuffed – customer provided 6 http://www.ti.com 6. 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