Evaluates: MAX2181 MAX2181 Evaluation Kit General Description Quick Start The MAX2181 evaluation kit (EV kit) simplifies evalua- Required Test Equipment tion of the MAX2181 FM low-noise amplifier. The EV kit RF signal generator (or generators) capable of enables testing of the devices features and performance delivering a signal in the 76MHz to 162.5MHz (FM) and does not require additional support circuitry or range at a power level of -34dBm.(A higher power software. The signal input and output use SMA connectors to source is required to measure distortion performance. facilitate connection of RF test equipment. See the Measurements section for more details) The EV kit is fully assembled with the device on board and RF spectrum analyzer that covers the operating incorporates input matching components for the U.S. FM frequency range broadcast band. DC power supply capable of supplying +6V to +24V Features 50 cables with SMA connectors Easy Evaluation of the MAX2181 Ammeter to measure supply current (optional) +6V to +24V Single-Supply Operation Noise-figure meter to measure NF (optional) RF Input and Output Matched to 50 Network analyzer to measure gain and return loss Proven PCB Layout (optional) Fully Assembled and Tested Connections and Setup Checking Gain The EV kit is fully assembled and factory tested. Follow Ordering Information appears at end of data sheet. the steps below for proper device evaluation in the default configuration. 1) Connect a DC supply with its output disabled (preset to +10V) to the VBATT and GND terminals (through an ammeter, if desired) on the EV kit. 2) Set the RF generator to the desired fre- quency at a power level of -37dBm. Disable the generators output and connect it to the FMIN SMA connector on the EV kit. 3) Connect an SMA cable from the FMOUT SMA connec- tor to the input of the spectrum analyzer. 4) Turn on the DC supply. The supply current should read approximately 56mA. 5) Activate the RF generators output. The signal on the spectrum analyzers display should indicate a typical 19-6884 Rev 0 12/13Evaluates: MAX2181 MAX2181 Evaluation Kit gain, as shown on the MAX2181 IC data sheet after Distortion accounting for cable and board losses. Two-tone distortion of the amplifier can be measured using a power combiner to couple the signals from two 6) Optional: Another method of determining gain is by generators into FMIN on the EV kit. During closed-loop using a network analyzer. This has the advantage operation, as the signal levels increase, the devices of displaying gain versus a swept frequency band, input impedance is reduced. At the upper end of the input in addition to displaying input and output return loss. signal level range, where each tone can be greater than Refer to the user manual of the network analyzer for 120dBV, this reduced impedance could create distor- setup information. Note: Depending on the settings of tion within the signal generators. For accurate distortion the devices maximum gain and power detector, the measurement, the input of the EV kit should be AGC loop can become active for input power levels isolated from the signal generators and power combiner. as low as -24dBm. To ensure consistent results are This can be accomplished using a ferrite isolator. obtained, the stimulus level of the network analyzer should be no greater than -34dBm, ensuring that the Layout Considerations gain is unaffected by the AGC loop. Electrical Detailed Description of Hardware At high-signal-level conditions, the RF currents flowing in the device can induce voltages in the PCB ground plane, Test Points known as ground bounce. To avoid unwanted spurious The MAX2181 signal path includes a power detector and products due to ground bounce, proper grounding tech- AGC loop, which can be adjusted for maximum gain and niques must be followed. AGC threshold. In addition, the AGC loop can be overrid- den by applying an external voltage to the FMAGC pin. Thermal Table 1 describes how to control the performance of the The device is designed to meet data sheet specifications device using the test points on the EV kit. at supply voltages up to +15V and to function at supply voltages up to +24V. Under these conditions, a significant Measurements amount of power must be dissipated by the device. This Noise requires the application PCB to provide a low thermal Noise figure can be measured using a NF meter. Because impedance path to a thermal ground. of the large number of FM broadcast signals that might be The EV kit PCB design accounts for this by providing present, this measurement should take place with the EV an array of thermal vias in the ground plane and a wide kit in a screen box or other type of RF shield. top metal trace connecting the package pad to a nearby screw. Adjacent pins 5-7 and 14-16 are all grounded, which allows the wide trace. Table 1. Control Performance with Test Points TEST POINT FUNCTION DESCRIPTION Disables the device and sets the supply current to 20mA (typ) if the antenna fault is ANTSENSE Antenna sense detected. Refer to the MAX2181 IC data sheet. FM AGC loop control Applying a DC control voltage to FMAGC allows the user to override the AGC loop. 0V FMAGC voltage gives maximum gain 5V gives minimum gain. Sets the FM AGC threshold. Refer to the MAX2181 IC data sheet. Default value on the FMDET FM AGC threshold EV kit is 99dBV (typ) referred to the FMOUT SMA connector (R4 = 43k). Sets the maximum value of FM gain (FMAGC = 0V). Default setting on the EV kit is FMGAIN FM gain control 6dB (typ) referred to the FMOUT SMA connector (R2 = 10k). LDO Regulated voltage Allows measurement of internal regulator voltage. Maxim Integrated 2 www.maximintegrated.com