DS64EV400 Datasheet, PDF (13/18 Pages) National Semiconductor (TI) – Programmable Quad Equalizer

pin. An output logic high indicates the presence of a signal
that has exceeded the ON threshold value (called SD_ON).
An output logic Low means that the input signal has fallen
below the OFF threshold value (called SD_OFF). These val-
ues are programmed via the SMBus (Table 1). If not pro-
grammed via the SMBus, the thresholds take on the default
values as shown in Table 4. The Signal Detect threshold val-
ues can be changed through the SMBus. All threshold values
specified are DC peak-to-peak differential signals (positive
signal minus negative signal) at the input of the device.
TABLE 4. Signal Detect Threshold Values
Channel 0:
Bit 1
Channel 1:
Bit 3
Channel 2:
Bit 5
Channel 3:
Bit 7
Channel 0:
Bit 0
Channel 1:
Bit 2
Channel 2:
Bit 4
Channel 3:
Bit 6
SD_OFF
Threshold
Register 06
(mV)
SD_ON
Threshold
Register 05
(mV)
0
0
40 (Default) 70 (Default)
0
1
30
55
1
0
55
90
1
1
45
75
OUTPUT LEVEL CONTROL
The output amplitude of the CML drivers for each channel can
be controlled via the SMBus (see Table 1). The default output
level is 620 mV_p-p. The following Table presents the output
level values supported:
TABLE 5. Output Level Control Settings
All Channels : Bit All Channels : Bit
3
2
0
0
Output Level
Register 08
(mV_P-P)
400
0
1
540
1
0
620 (Default)
1
1
760
AUTOMATIC ENABLE FEATURE
It may be desirable to place unused channels in power-saving
Standby mode. This can be accomplished by connecting the
Signal detect (SDn) pin to the Enable (ENn) pin for each
channel (See Figure 9). In order for this option to function
properly, the register value for Reg. 07 should be 00'h (default
value). If an input signal swing applied to a data channel is
above the voltage level threshold as shown in Table 4, then
the SDn output pin is asserted High. If the SDn pin is con-
nected to the ENn pin, this will enable the equalizer, limiting
amplifier, and output buffer on the data channels; thus the
DS64EV400 will automatically enter the ACTIVE state. If the
input signal swing falls below the SD_OFF threshold level,
then the SDn output will be asserted Low, causing the channel
to be placed in the STANDBY state.
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