LM1972 Datasheet | National Semiconductor

Description The LM1972 is a digitally controlled 2-channel 78d B audio attenuator fabricated on a CMOS process. Each channel has attenuation steps of 0.5d B from 0d B- 47.5d B, 1.0d B steps from 48d B- 78d B, with a mute function attenuating 104d B. Its logarithmic attenuation curve can be customized through software to fit the desired application. The performance of a µPot is demonstrated through its excellent Signal-to-Noise Ratio, extremely low (THD+N), and high channel separation. Each µPot contains a mute function that disconnects the input signal from the output, providing a minimum attenuation of 96d B. Transitions between any attenuation settings are pop free. The LM1972’s 3-wire serial digital interface is TTL and CMOS patible; receiving data that selects a channel and the desired attenuation level. The Data-Out pin of the LM1972 allows multiple µPots to be daisy-chained together, reducing the number of enable and data lines to be routed for a given application. n n n n n Frequency response: 100 k Hz (- 3d B) (min) Attenuation range (excluding mute): 78d B (typ) ± 0.25d B (max) Differential attenuation: Signal-to-noise ratio (ref. 4 Vrms): 110d B (min) Channel separation: 100d B (min) Features n n n n 3-wire serial interface Daisy-chain capability 104d B mute attenuation Pop and click free attenuation changes Applications n n n n n Automated studio mixing consoles Music reproduction systems Sound reinforcement systems Electronic music (MIDI) Personal puter audio control Key Specifications n Total Harmonic Distortion + Noise: 0.003% (max) Typical Application Connection Diagram Dual-In-Line Plastic or Surface Mount Package DS011978-1 FIGURE 1. Typical Audio Attenuator Application Circuit DS011978-2 Top View Order Number LM1972M or LM1972N See NS Package Number M20B or N20A µPot™ and Overture™ are trademarks of National Semiconductor Corporation. © 1999 National Semiconductor Corporation DS011978 .national. Absolute Maximum Ratings (Notes 2, 1) If Military/Aerospac...