AK7846 Datasheet, PDF (9/16 Pages) Asahi Kasei Microsystems – Stereo Audio Class-D Amp with Power Booster for Piezo Speakers

AKEMDAKEMD CONFIDENTIAL
[AK7846]
„ Analog inputs
AC-coupling capacitor is required at analog inputs. Recommended capacitance is 0.1µF. This AC-coupling
capacitance configures High-Pass-Filter, and used to configuration of POP NOISE SUPPRESSOR as well.
Therefore, any variation of this capacitance affects both HPF cut-off frequency and POP NOISE SUPPRESSOR
operation.
Additional input filter is applicable. When using filter at analog input, place it before AC-coupling capacitors.
Note 16. Cut off frequency (fc) of the High-pass filter, used as decoupling before input, is caluculated by an
equation, 1 / (2 × π × R × C). For example, when Input impedance of INN and INP pins are 50kΩ(typ.) and
AC coupling capacitors are 0.1µF, then the cut off frequency will be 31.8Hz.
„ Pre AMP
THE AK7846 has internal Pre-Amplifier, which supports from −6dB to +15dB(3dB/step) gain range.
Pre-Amplifier gain is adjusted by PG0,PG1 and PG2 like as shown below.
PG2
“Low”
“Low”
“Low”
“Low”
“High”
“High”
“High”
“High”
PG1
“Low”
“Low”
“High”
“High”
“Low”
“Low”
“High”
“High”
PG0
“Low”
“High”
“Low”
“High”
“Low”
“High”
“Low”
“High”
Pre Gain Setting Value
−6dB
-3dB
0dB
+3dB
+6dB
+9dB
+12dB
+15dB
Table. 1 Pre Gain Setting
„ Class-D AMP
Class-D architecture features higher efficiency and low power consumption operation.
AKM filter-less solution offers Class-AB performance with Class-D efficiency and minimal board space.
„ Pop Noise Suppressor
The AK7846 features extensive pop noise suppression circuitry.
„ Power Booster
Built-in BOOST DCDC CONVERTER generates adequate high voltage for Piezo-Speaker. Input voltage range
corresponds with Li-Ion battery voltage range (2.7V ~ 4.5V), and output voltage is 13V. Normally, output connected
to and supply VDD1 and VDD2 for Class-D operation.
„ Lowpass Filter
The AK7846 has a built-in Lowpass Filter at the input side. Cutoff frequency can be adjusted by FC0 and FC1 as
follows. FC0 and FC1 must be connected to either ground (VSS4) or DVDDI.
FC1
FC0
CurOff Frequency
“Low”
“Low”
16kHz
“Low”
“High”
8kHz
“High”
“Low”
4kHz
“High”
“High”
4kHz
Table. 2 Adjustable Cutoff Frequency of Lowpass filter
Rev.04.9
–9–
2008/03