Evaluates: MAX44267 MAX44267 Evaluation Kit General Description Quick Start The MAX44267 evaluation kit (EV kit) provides a proven Required Equipment design to evaluate the MAX44267 Beyond-the-Rails MAX44267 EV kit precision, low-noise, low-drift, dual operational amplifier 12V DC power supply (op-amp) in a 14-pin TSSOP package. The EV kit circuit is preconfigured as noninverting amplifiers, but can be adapt- Two precision voltage sources ed to other topologies by changing a few components. Two digital multimeters (DMMs) The EV kit comes with a MAX44267AUD+ installed. Procedure Features and Benefits The EV kit is fully assembled and tested. Follow the steps below to verify board operation: Accommodate Multiple Op-Amp Configuration 1) Verify that all jumpers (JU1JU5) are in their default Up to 12.5V with a Single Supply (+2.25V to +15V) positions, as shown in Table 1. True Zero Output from a Single Supply 2) Connect the positive terminal of the +12V supply to Proven PCB Layout the VDD test point and the negative terminal to the Fully Assembled and Tested GND test point. 3) Connect the positive terminal of the precision voltage Ordering Information appears at end of data sheet. source to INAP test point. Connect the negative ter- minal of the precision voltage source to the GND test point. INAM is already connected to GND via JU1. 4) Connect the positive terminal of the second preci- sion voltage source to the INBP test point. Connect the negative terminal of the precision voltage source to the GND test point. INBM is already connected to GND via JU3. 5) Connect the DMMs to monitor the voltages on OUTA and OUTB test points. With the 10k feedback resis- tors and 1k series resistors, the gain of the nonin- verting amplifier is +11V/V. 6) Turn on the power supply. 7) Set the precision voltage sources to 100mV and en- able. Observe the output at OUTA and OUTB on the DMMs. Both should read approximately +1.1V. 8) Disable the precision voltage sources and supply. 9) Remove shunts from JU1 and JU3, and install shunts on jumper JU2 and JU4. The gain of the inverting am- plifier is -10V/V. 10) Apply each precision voltage source to INAM and INBM test points. 11) Enable the precision voltage sources. Observe the output at OUTA and OUTB on the DMMs. Both should Beyond-the-Rails is a trademark of Maxim Integrated Products, read approximately -1.0V. Inc. 19-7520 Rev 0 2/15Evaluates: MAX44267 MAX44267 Evaluation Kit filter and buffer operations. The MAX44267 EV kit can Detailed Description of Hardware be configured in a Sallen-Key topology by replacing and The MAX44267 precision, low-noise, low-drift dual opera- populating a few components. The Sallen-Key topology tional amplifier offers true-zero output that allows the can be configured as a unity-gain buffer by replacing R5 output to cross zero and maximize the dynamic range of with a 0 resistor and removing resistor R1. The signal an ADC and increase resolution. is noninverting and applied to INAP. The filter component Op Amp Configurations pads are R2R4 and R8, where some have to be popu- lated with resistors and others with capacitors. The MAX44267 is a single-supply, dual op amp that is ideal for differential sensing, noninverting amplification, Lowpass Filter: To configure the Sallen-Key as a low- buffering, and filtering. A few common configurations are pass filter, remove jumper JU1, populate the R2 and R8 shown in the next few sections. pads with resistors and populate the R3 and R4 pads with capacitors. The corner frequency and Q are then The following sections explain how to configure one of the given by: devices op amps (op amp A). To configure the devices second op amp (op amp B), the same equations can be 1 f = used after modifying the component reference designators. C 2 RR C C R2 R8 R3 R4 Noninverting Configuration The MAX44267 EV kit comes preconfigured as a nonin- RR C C R2 R8 R3 R 4 verting amplifier. The gain is set by the ratio of R5 and R1. Q = C (R + R ) The MAX44267 EV kit comes preconfigured for a gain of R3 R2 R8 +11V/V. The output voltage for the noninverting configura- Highpass Filter: To configure the Sallen-Key as a high- tion is given by the equation below: pass filter, remove jumper JU1, populate the R3 and R4 R5 V =(1+)V V pads with resistors and populate the R2 and R8 pads OUTA INAP OS R1 with capacitors. The corner frequency and Q are then Inverting Configuration given by: 1 To configure the EV kit as an inverting amplifier, remove f = C the shunt on JU1 and install a shunt on jumper JU2 and 2 RR C C R3 R4 R2 R8 feed an input signal on the INAM pad. RR C C Differential Amplifier R3 R4 R2 R8 Q = To configure the MAX44267 EV kit as a differential R (C + C ) R4 R2 R8 amplifier, replace R1, R2, R3, and R5 with appropriate Bandpass Filter: To configure the Sallen-Key as a band- resistors. When R1 = R2 and R3 = R5, the CMRR of the pass filter, remove jumper JU1, replace R8, populate R3 differential amplifier is determined by the matching of the and R4 pads with resistors and populate C8 and R2 pads resistor ratios R1/R2 and R3/R5. with capacitors. The corner frequency and Q are then V A (V V ) given by: OUTA V INAP INAM RR+ where the gain is: R4 R8 1 f = C R5 R3 2 C C RRR C8 R2 R8 R3 R4 A V R1 R2 R + R C C RRR Sallen-Key Configuration ( ) R4 R8 C8 R2 R8 R3 R4 Q = The Sallen-Key topology is ideal for filtering sensor R R5 signals with a second-order filter and acting as a buf- R R C ++C R C (R R ) ( ) R4 R8 C8 R2 R3 R2 R4 R8 R R1 fer. Schematic complexity is reduced by combining the Maxim Integrated 2 www.maximintegrated.com = = =