AK2347B Datasheet, PDF (32/34 Pages) Asahi Kasei Microsystems – Two-way Radio Audio & Sub-Audio Processor

ASAHI KASEI
[AK2347B]
8) LIMLV pin
The LIMLV pin is used for adjusting the limit level of the limiter circuit. This pin may be left open
or may be used by connecting resistors as shown in the figure below.
When the pin is left open, a predetermined limit level can be obtained. The limit level is
expressed as follows:
HVref = 0.256 × (VDD - AGND) [Vo-p]
For example, let VDD be 3V. The limit level is calculated as follows:
Hvref = 0.256 × (3.0 - 1.5) = 0.384Vo-p Then, 1.5 ±0.384V is the typical value of the limit level.
When a DC voltage higher than the AGND voltage level (= 1/2VDD) is applied to the pin through
resistors, the limit level can be adjusted. The limit level is the difference between LIMLV and
AGND and is expressed as AGND ±(LIMLV - AGND).
Let VDD be 3V. The limit level is calculated as follows:
LIMLV=1.6V → 1.5 ±0.1V
1.7V → 1.5 ±0.2V
1.8V → 1.5 ±0.3V
1.9V → 1.5 ±0.4V
1.933V → 1.5 ±0.433V (equivalent to -6.6dBx (Max.))
Then, the above values are obtained as the typical limit levels.
Because AGND level is used as the reference level for the limiter circuit operation as mentioned
above, when resistors are connected, they should be connected so that VDD and AGND are
separated by these resistors to supply a DC level to the LIMLV pin. In addition, make
adjustments so that the sum of resistance (R1 + R2) is around 51kΩ.
VDD
R1
7 _LIMLV
R2
2 _AGND
LSI
R1+R2
VSS
MS1419-E-00
- 32 -
2012/05