Overview

The LA1780M integrates all six blocks required in a car radio tuner on a single chip. The LA1780M is based on the LA1888NM, and features improvements to each of the blocks; improvements designed to provide improved noise characteristics, especially for noise related to multipath, three-signal intermodulation distortion, and two-signal suppression.

Features

• Improved noise reduction methods

— The FM front end provides excellent 3-signal

characteristics equivalent to those of the LA1193M.

— Superlative listenability due to improved medium and

weak field noise canceller characteristics.

— Improved separation characteristics

— Anti-birdie filter

— Improved AM and FM thermal characteristics

— Excellent FM signal meter linearity

— Modified N.C. circuit for improved noise rejection

• Double conversion AM tuner (up conversion)

Reduces the number of external components required as

compared to earlier double conversion tuners, in

particular, no crystal is required (when used in

conjunction with the LC72144).

• Sample-to-sample variation reduction circuit built into the FM IF circuit.

(Fixed resistors are used for the SD, keyed AGC, mute

on adjustment, ATT, SNC, and HCC functions.)

• Since the LA1780M retains the block structure of the

LA1888NM, products using that IC can be easily

converted, allowing further end product miniaturization.

Functions

• FM front end

• FM IF

• Noise canceller

• Multiplex

• AM up-conversion

• FM/AM switch

• MRC