8-3. High Speed Outputs (SDO/SDO and SCO/SCO)
V
CC
SDO/SDO and SCO/SCO are current mode outputs that
require external pullups (see Figure 17). The output signal
swings are 800mV when 75Ω resistors are used. To shift the
signal levels down by approximately 0.7 volts, place a
diode between VCC and the pullups. When the output traces
are longer than 1in, use controlled impedance traces. Place
the pullup resistors at the end of the output traces as they
terminate the trace in its characteristic impedance (75Ω).
75
75
75
75
SDO
SDO
SCO
SCO
GS7025
V
CC
Fig. 17
TYPICAL APPLICATION CIRCUIT
V
CC
10k
V
CC
V
V
CC
CC
V
V
CC
CC
V
CC
V
CC
4n7
44
43
42
41
40
39
38
37
36
35
34
4 x 75 see Note 2
V
33
32
31
30
29
28
27
26
25
24
23
EE
DDI
1
2
3
4
5
6
7
8
9
from GS9024
see Note 1
SDO
SDO
DDI
V
V
CC
CC_75
CC
To
GS9020
V
V
V
V
CC
EE
75
GS7025
TOP VIEW
SCO
SCO
EE
SDI
15nH
75
10n
V
EE
SDI
V
37.5 75 10n
nc
nc
V
CC
CC
V
CC
V
EE
100k
Pot
(Optional)
V
270
nc
10 CD_ADJ
11 AGC-
CC
0.1µ
12
13
14
15
16
17
18
19
20
21
22
All resistors in ohms,
all capacitors in microfarads,
unless otherwise stated.
V
CC
365
(1%)
1.8k 15n
3.3p
0.1µ
0.1µ
0.1µ
V
Power supply decoupling
capacitors are not shown.
CC
NOTES
1. It is recommended that the DDI/DDI inpute are not driven when the SDI/SDI inputs are being used.
This minimizes crosstalk between the DDI/DDI and SDI/SDI inputs and maximizes performance.
2. These resistors are not needed if the internal pull-up resistors on the GS9020 are used.
12
GENNUM CORPORATION
522 - 80 - 00
GENNUM [ GENNUM CORPORATION ]
