TUSB7340 datasheet(17/122 Pages) TI2

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When enabled, the receiver equalization logic analyzes data patterns and transition times to determine whether

the low frequency gain of the equalizer should be increased or decreased. For the fully adaptive setting (EQ =

0001), if the low frequency gain reaches the minimum value, the zero frequency is then reduced. Likewise, if it

reaches the maximum value, the zero frequency is then increased.

The decision logic is implemented as a voting algorithm with a relatively long analysis interval. The slow time

constant that results reduces the probability of incorrect decisions but allows the equalizer to compensate for the

relatively stable response of the channel.

Table 6-3. Receiver Equalizer Configuration

EQ VALUE

AMPLITUDE REDUCTION

LOW-FREQUENCY GAIN

ZERO FREQUENCY

0000

Maximum

0001

Fully Adaptive, FTC Normal

0010

Fully Adaptive, FTC Reversed

0011

Hold

0100

Initialize

0101

0110

0111

1000

Partially Adaptive

365 MHz

1001

275 MHz

1010

195 MHz

1011

140 MHz

1100

105 MHz

1101

75 MHz

1110

55 MHz

1111

50 MHz

6.3.2 Input Clock

6.3.2.1 Clock Source Requirements

The TUSB73x0 supports an external oscillator source or a crystal unit. The frequency of the clock source may

be 24 MHz or 48 MHz. If a clock is provided to XI instead of a crystal, XO is left open and VSSOSC should be

connected to the PCB ground plane. Otherwise, if a crystal is used, the connection needs to follow the guidelines

below.

Because XI and XO are coupled to other leads and supplies on the PCB, it is important to keep them as short

as possible and away from any switching leads. It is also recommended to minimize the capacitance between XI

and XO. This can be accomplished by connecting the VSSOSC lead to the two external capacitors CL1 and CL2

and shielding them with the clean ground lines. The VSSOSC should not be connected to PCB ground when

using a crystal.

Load capacitance (Cload) of the crystal varying with the crystal vendors is the total capacitance value of the entire

oscillation circuit system as seen from the crystal. It includes two external capacitors CL1 and CL2.

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TUSB7320, TUSB7340

SLLSE76Q – MARCH 2011 – REVISED MARCH 2024

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