AK4709 Datasheet, PDF (23/42 Pages) Asahi Kasei Microsystems – Low Power AV SCART Switch

[AK4709]
■ Clamp and DC-restore circuit control (06H: D7-D2)
Each CVBS and Y input has the sync tip clamp circuit. The DC-restore circuit has two clamp voltages 0.24V(typ) and
1.49V(typ) to support both RGB and YPbPr signal. They correspond to 0.12V(typ) and 0.75V(typ) at the SCART
connector when matched by 75Ω resistors. The CLAMP1, CLAMP0 and CLAMPB bits select the input circuit for
ENCRC pin (Encoder Red/Chroma), ENCB pin (Encoder Blue), VCRRC pin (VCR Red/Chroma) and VCRB pin (VCR
Blue) respectively. VCLP2-0 bits select the sync source of DC- restore circuit.
CLAMPB
0
0
1
1
CLAMP0
0
1
0
1
VCRRC Input Circuit
VCRB Input Circuit
DC restore clamp active
(0.24V at sync timing/output pin)
Biased
(1.49V at sync timing/output pin)
DC restore clamp active
(1.49V at sync timing/output pin)
DC restore clamp active
(0.24V at sync timing/output pin)
(DC restore clamp active)
(0.24V at sync timing output pin)
DC restore clamp active
(1.49V at sync timing/output pin)
(reserved)
(reserved)
Table 13. DC-restore control for VCR Input
note
for RGB
for Y/C (default)
for Y/Pb/Pr
CLAMPB
0
0
1
1
CLAMP1
0
1
0
1
ENCRC Input Circuit
ENCB Input Circuit
DC restore clamp active
(0.24V at sync timing/output pin)
Biased
(1.49V at sync timing/output pin)
DC restore clamp active
(1.49V at sync timing/output pin)
DC restore clamp active
(0.24V at sync timing/output pin)
DC restore clamp active
(0.24V at sync timing output pin)
DC restore clamp active
(1.49V at sync timing/output pin)
(reserved)
(reserved)
Table 14. DC-restore control for Encoder Input
note
for RGB
for Y/C
for Y/Pb/Pr
(default)
CLAMP2
0
1
ENCG Input Circuit
DC restore clamp active
(0.24V at sync timing/output pin)
Sync tip clamp active
(0.24V at sync timing/output pin)
note
for RGB
for Y/Pb/Pr
(default)
Note: When the VTV2-0 bits = “001” (source for TV = Encoder CVBS /RGB), TVG bit = “1” (TVG = active) and
VCLP1-0 bits = “11” (DC restore source = ENCG), the sync tip is selected even if the CLAMP2 bit = “0”.
Table 15. DC-restore control for Encoder Green/Y Input
VCLP2-0: DC restore source control
VCLP2 VCLP1 VCLP0
Sync Source of DC Restore
0
0
0
ENCV
0
0
1
0
1
0
0
1
1
ENCY
VCRVIN
ENCG
1
0
0
1
0
1
1
1
0
VCRG
(reserved)
(reserved)
1
1
1
(reserved)
Note: When the AUTO bit = “1”, the source is fixed to VCRVIN.
Table 16. DC-restore source control
(default)
MS1319-E-00
- 23 -
2011/07