LA1145, 1145M
SD Output Circuit
1. LA1145 SD output differs from the LA1140’s pin substitute SD output as shown below. The SD output on the LA1145 does
not operate in conjunction with the soft mute characteristics.
1) LA1140
Hole detector
Mute driver
Signal meter
Band mute
output
2) LA1145
Hole detector
Mute driver
Signal meter
Bandmute
output
Comparator
Exhibit hysteresis
As shown, the SD output is the logical AND of the band mute and S-meter comparator outputs.
2. Signal search using the SD output circuit
2-1 The transition response characteristics of the SD output circuit depends on the time constants of pins 15, 16, 17 and 8.
As the SD output transition response characteristics are determined by the pin with the largest time constant, erroneous
stopping will result when a search time is less than the largest one.
2-2 Band mute range circuit time constant (pin 8)
An equivalent circuit to the band circuit is shown below.
Mute switch circuit
No. 2725-9/17
SANYO [ SANYO SEMICON DEVICE ]
