AK4955 Datasheet, PDF (66/117 Pages) Asahi Kasei Microsystems – 24bit Stereo CODEC with MIC/SPK/Cap-less VIDEO-AMP/ LDO & DSP

[AK4955]
■ Video Block
The integrated cap-less video amplifier with a charge pump has drivability for a load resistance of 150Ω (Figure 52). The
AK4955 has a composite input and output. A Low Pass Filter (LPF) and Gain Control Amp are integrated, and VG1-0
bits set the gain (+6/+9/+12/16.5 dB) (Table 63).The integrated charge pump circuit supplies a negative power to the
video amplifier, and the video amplifier outputs 0V video signal as pedestal level. The video amplifier power
management is controlled by PMV bit, and the charge pump circuit power management is controlled by PMCP bit. When
PMV bit = “0”, the VOUT pin outputs 0V. The video inputs must be C-coupled by a 0.1μF capacitor. The video signal
source impedance at transmitting side must be less than or equal to 600Ω.
max 600Ω
VIN
Typ 0.1µF
Clamp
PMV bit
LPF
+6/+9/+12/+16.5dB
PMCP bit
Clock
Generator
Charge
Pump
VSS1
PVEE
2.2µF
VOUT
Figure 52. Video Block Diagram
VG1-0 bits
GAIN
00
+6dB
(default)
01
+9dB
10
+12dB
11
+16.5dB
Table 63. Video Signal Gain Setting
AK4955
75Ω
VOUT
75Ω
0V
Figure 53. Video Signal Output
MS1343-E-00
- 66 -
2011/12