CDK8307 Cadeka Microcircuits LLC., CDK8307 Datasheet - Page 19

• Manufacturer Part Number: CDK8307
• Description: 12/13-bit, 20/40/50/65/80msps, Eight Channel, Ultra Low Power Adc With Lvds
• Manufacturer: Cadeka Microcircuits LLC.

PRELIMINARY Data Sheet
Table 7. LVDS Internal Termination Programmability
The off-chip load on the LVDS buffers may represent a characteristic impedance that is not perfectly matched with
the PCB traces. This may result in reflections back to the LVDS outputs and loss of signal integrity. This effect can be
mitigated by enabling an internal termination between the positive and negative outputs of each LVDS buffer. Internal
termination mode can be selected by setting the en_lvds_term bit to '1'. Once this bit is set, the internal termination
values for the bit clock, frame clock, and data buffers can be independently programmed using sets of three bits. Table
8 shows how the internal termination of the LVDS buffers are programmed. The values are typical values and can vary
by up to ±20% from device to device and across temperature.
Table 8. Bit Clock Internal Termination
Table 9. Analog Input Invert
The IPx pin represents the positive analog input pin, and INx represents the negative (complementary) input. Setting
the bits marked invert_ch <8:1> (individual control for each channel) causes the inputs to be swapped. INx would then
represent the positive input, and IPx the negative input.
©2009 CADEKA Microcircuits LLC
en_lvds_term
term_lclk<2:0>
term_
frame<2:0>
term_dat<2:0>
invert_ch<8:1>
Name
Name
term_*<2:0>
000
001
010
011
100
101
110
111
Enables internal termination for
LVDS buffers
Programmable termination for
LCLKN and LCLKP buffers
Programmable termination for
FCLKN and FCLKP buffers
Programmable termination for
DxP and DxN buffers
Swaps the polarity of the analog
input pins electrically
Description
Description
LVDS Internal Termination
Termination Disabled
Termination
disabled
Termination
disabled
Termination
disabled
Termination
disabled
IPx is positive
input
Default
Default
260Ω
150Ω
125Ω
94Ω
80Ω
66Ω
55Ω
5
5
D
1
D
1
D
1
4
X
1
1
1
D
1
4
D
3
D
3
1
1
D
1
2
D
1
2
D
1
D
1
1
1
D
1
0
X X X
D
1
0
D
9
D
9
D
D
8
8
D
7
D
7
X X X X X X X X
D
D
6
X X X
6
D
5
D
5
D
4
D
4
D
D
3
3
D
2
X X X
D
2
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D
D
1
1
D
0
D
0
Address
Address
In Hex
In Hex
12
24
19