NJM2549 WIDE BAND FM IF DEMODULATOR GENERAL DESCRIPTION PACKAGE OUTLINE The NJM2549 is a wide band IF IC with a maximum IF input frequency of 15 MHz. It includes an IF Amplifier, Quadrature Detector, RSSI and IF Balanced Output. NJM2549RB2 MAIN APPLICATIONS RF ID Radar detector Wireless Infrared Communication System Voice Transmission System A few MHz band Signal Detector FEATURES Wide Range Operating Voltage 2.7V to 9V (recommended supply voltage) Low Operating Current 3mA (standard) Wide Range IF Input Frequency 10.7MHz (standard) 100kHz to 15MHz (reference value) Wide Band FM Detector Range DC to 1MHz (reference value) RSSI Quick Response High FM Detection Sensitivity 22dBuV (- 3dB Limiting Sensitivity) IF Amplifier with Balanced Output Bipolar Technology Package Outline TVSP10 BLOCK DIAGRAM AF QUAD IF IF RSSI OUT IN OUT1 OUT2 OUT 10 9 8 7 6 QUAD DET IF AMP RSSI 1 2 3 4 5 IF IF IF + GND V IN DEC1 DEC2 Ver.2011-09-26 -1- NJM2549 EXPLANATION Functional Block Diagram + AF OUT V RSSI OUT FM Demodulator T1 10.7MHz C7 C4 PHASE C6 0.01u R2 2.4k 100p SHIFTER 82p C5 3p 10 9 8 7 6 QUAD DET RSSI IF AMP RSSI 1 2 3 4 5 C2 C1 C3 0.01u 0.01u 0.01u C9 C8 R1 10u 0.01u 51 IF Amplifier IF IN General The frequency- converted RF signal goes through an external narrow or wide bandwidth BPF and is inputted to Pin 2 as unbalanced input, otherwise inputted to Pin2 and Pin3 as balanced input. The available frequency range of IF signals are from 100kHz to 15MHz. The IF amplifier is a limiting amplifier with 75dB gain and converts IF input signal to an amplitude - limiting IF signal. The FM demodulator consists of an external phase shifter circuit and an internal quadrature detector. It demodulates the amplitude - limiting IF signal and outputs to Pin10 as AF output signal. The demodulated AF output signal is the rail-to-rail output of 2.7Vpp with the maximum bandwidth of up to 1MHz. Pin6 is the output of RSSI circuit, which outputs DC level proportional to the log of input signal level to Pin 2. NJM2549 has other remarkable functions: balanced input/ output (Pins 2, 3, 7and 8), and pin-selectable for either of two demodulation characteristics (Pin7and 8). IF Amplifier (Pins 2, 3, 4, 7, and 8) Input impedance Pin2 and Pin 3 are the input terminal for IF input signal. Pin2 is used for unbalanced input, and a pair of Pin 2 and Pin3 is used for balanced input. As one general example of unbalanced input, IF signal is supplied to Pin 2 through an external band-pass filter and a matching resistor R1 in parallel. In general, the matching impedance of the filter is 330ohm. Pin 2 is designed to have input impedance of 10kohm much higher than 330ohm, and R1 should be 330ohm Ver.2011-09-26 -2-