LA1650 查看數據表（PDF） - SANYO -> Panasonic

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LA1650

Time Code Reception ICs

SANYO -> Panasonic 

LA1650, 1650C

Block Functional Descriptions

Amplifier Block

The radio signal picked up by the bar antenna (resonant frequency: 40 kHz for Japan) is amplified by amplifier 1 which

includes an AGC function, and is passed through a 40 kHz crystal element used as a bandpass filter. This signal is then

amplified further by amplifier 2. The total gain from the amplifier 1 input to the amplifier 2 output is 90 dB when the

AGC is disabled.

AMP(1) witn AGC Crystal AMP(2)

A12770

Since amplifier 1 has frequency characteristics of –3 dB at fc = 80 kHz from the output level at fc = 40 kHz, and

amplifier 2 has frequency characteristics that are flat up to 100 kHz, this IC can support the standard radio frequencies

used in any country simply by changing bar antenna and the resonant frequency of the crystal used.

REC Block

The 40 kHz carrier signal output from amplifier 2 is input to the REC block through a 1000 pF capacitor. The REC block

input impedance is 20 kΩ, which, in conjunction with the 1000 pF capacitor, forms a high-pass filter with a cutoff

frequency of about 8 kHz. The carrier is full-wave rectified within the REC block, split into two signal systems, and

output. One signal system passes through a low-pass filter with a time constant of about 1 s and is then input to the DEC

block. The other passes through a low-pass filter with an even larger time constant and is fed back to amplifier 1 as the

AGC control voltage (pin 3: a DC voltage).

Rectifier

Low-pass filter

(time constant: 1 s)

Low-pass filter

(time constant: several seconds or longer)

To the DEC block

AGC voltage (to amplifier 1)

A12771

The AGC voltage is set up to be about 0.6 V when there is no input present. However, since charging is performed by a

small current of only a few µA, we recommend precharging if the LA1650 is used for reception immediately after power

is applied. (Charge to about 1.0 V for about 100 ms.)

DEC Block

The time code signal (1 Hz) from which the 40 kHz carrier has been removed is input to the DEC block, and wave

shaping is applied to create a serial output signal in which 1 and 0 have the levels VCC and ground, respectively.

VCC

Decoder

GND

A12772

No. 6310-8/14

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