AK2346B Datasheet, PDF (29/31 Pages) Asahi Kasei Microsystems – Two-way Radio Audio Processor

ASAHI KASEI
[AK2346B]
8) LIMLV pin configuration
LIMLV pin is an adjuster for the limit level of audio signal at baseband. It operates in left open or
applying a DC voltage.
In case of left open, limit level sets predetermined value depending on the VDD level, which can
be calculated using the following formula:
HVref = 0.256 x (VDD - AGND) [Vo-p]
For example at VDD=3V HVref=0.256 x (3.0 - 1.5)=0.384Vo-p
So typical peak-to-peak limit level is calculated as 1.5±0.384Vp-p
In case of applying a DC voltage higher than AGND(=1/2VDD) level, the limit level can be
adjusted according to following formula:
Vlimit = AGND ± (LIMLV-AGND)
For example at VDD=3V, typical limit level: Vlimit is calculated as below.
LIMLV = 1.6V → Vlimit = 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 (corresponding to –6.6dBx (Max.) )
Limiter circuitry operates at AGND level common. In case of applying a DC voltage usage,
recommended external configuration is composed of VDD and AGND level separation with
resistors. Typical resistor value is R1+R2=51kΩ
VDD
R1
5 _LIMLV
R2
R1+R2
AGND
VSS
LSI
MS1409-E-00
- 29 -
2012/05