GS3440 Datasheet, PDF (16/23 Pages) Semtech Corporation – Extended Reach 3G/HD/SD Adaptive Cable Equalizer

When muted, the output swing is set to 425mV_ppd and the outputs are latched.
Automatic muting of the output can be enabled by connecting the CD pin to the OP_CTL pin.
If the connection is made directly, as shown in Figure 4-1, the output would be in its default
mode (850mV_ppd swing with no de-emphasis) when there is signal present.
Figure 4-1: Direct Loopback
To enable automatic muting while the output is configured for other settings, a resistor
network should be used between CD and VCC_A. The intermediate voltages of this resistor
ladder can set the output to any one of the nine different settings as shown in Figure 4-2 and
Figure 4-3.
Levels
Taps
0
1
2
3
4
5
6
7
8 _{VCC_A}
1K 1K 1K 1K 1K 1K 1K 1K 2.6K
Levels
Taps
0
1
2
3
4
5
6
7
8 _{VCC_A}
1K 1K 1K 1K 1K 1K 1K 1K 2.6K
Figure 4-2: Resistor Divider Loopback Example #1
(Function Level 3 from Table 4-5)
Figure 4-3: Resistor Divider Loopback Example #2
(Function Level 4 from Table 4-5)
In Figure 4-2, the automatic muting of the output is established by connecting node 3 to the
OP_CTL pin. In this scenario, the output would be 850mV_ppd with 6dB of de-emphasis when
there is a signal present.
In Figure 4-3, the OP_CTL pin is connected to node 4. In this scenario, the output would be
425mV_ppd with no de-emphasis when there is a signal present.
In both cases, the output would be muted when no carrier is detected.
Note: When the device is in SLEEP mode, automatic muting and SQ_ADJ do not function.
Asserting the SLEEP pin manually overrides all other functionality.
GS3440 Adaptive Cable Equalizer
Final Data Sheet
Rev. 2
December 2012
16 of 23
Proprietary and Confidential