U4226B

The U4226B has the following features including Very low power consumption;Very high sensitivity;High selectivity by using two crystal filters;Power-down mode available;Only a few external components necessary;Digitalized serial output signal;AGC hold mode.

The U4226B is a bipolar integrated straight-through receiver circuit in the frequency range of 40 to 80 kHz.The U4226B is designed for radio-controlled clock applications.The signals and voltages at the Pins REC, INT, FLA,FLB, Q1A, Q1B, Q2A and Q2B cannot be measured by standard measurement equipment due to very high internal impedances. For the same reason, the PCB should be protected against surface humidity.Thus, the first step in designing the antenna circuit is to measure the bandwidth. Figure 16 shows an example for the test circuit. The RF signal is coupled into the bar antenna by inductive means, e.g., a wire loop. U4226B can be measured by a simple oscilloscope using the 10:1 probe.The input capacitance of the probe, typically about 10 pF, U4226B should be taken into consideration. By varying the frequency of the signal generator, the resonant frequency can be determined.

Furthermore, some critical parasitics of U4226B have to be considered. These are shortened loops (e.g., in the ground line of the PCB board) close to the antenna and undesired loops in the antenna circuit. Shortened loops decrease the Q value of the circuit. They have the same effect like conducting  plates  close  to  the  antenna.  To  avoid undesired loops in the antenna circuit, it is recommended to mount the capacitor Cres as close as possible to the antenna coil or to use a twisted wire for the antenna-coil connection. This twisted line is also necessary to reduce feedback of noise from the microprocessor to the IC input. Long connection lines must be shielded.Parameters can vary in different applications. All operating parameters of U4226B must be validated for each customer application by the customer. Should the buyer use TEMIC products for any unintended or unauthorized application, the buyer shall indemnify TEMIC against all claims, costs, damages, and expenses, arising out of,directly or indirectly, any claim of personal damage, injury or death associated with such unintended or unauthorized use.