LMH6622MAX National Semiconductor, LMH6622MAX Datasheet - Page 14

• Manufacturer Part Number: LMH6622MAX
• Description: IC,Operational Amplifier,DUAL,BIPOLAR,SOP,8PIN,PLASTIC
• Manufacturer: National Semiconductor

Specifications of LMH6622MAX

• Dc: 06+
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

www.national.com
DSL Receive Channel Applications
The two R
ing through the 1:N transformer.
Where R
The resistors R
the pre-amp. The receive gain is selected to meet the ADC
full-scale requirement of a DSL chipset.
Resistor R
cancellation of the output driver signal at the output of the
receiver.
Since the LMH6622 is configured as an inverting summing
amplifier, V
The expression for V
position principle.
When V
When V
Therefore,
And then,
Setting R
receive path, then we have
We can also find that,
And then
In conclusion, the peak-to-peak voltage to the ADC would
be,
(Continued)
S
A
L
N is the turns ratio of the transformer.
1
= 0,
= 0,
S
is the impedance of the twisted pair line.
1
OUT
= 2*R
resistors are used to provide impedance match-
and R
2
is found to be,
and R
2
to cancel unwanted driver signal in the
2
1
along with R
and V
F
are used to set the receive gain of
2
can be found by using super-
F
are used to achieve
14
RECEIVE CHANNEL NOISE CALCULATION
The circuit of Figure 2 also has the characteristic that it
cancels noise power from the drive channel.
The noise gain of the receive pre-amp is found to be:
Noise power at each of the output of LMH6622:
where
For a voltage feedback amplifier,
Therefore, total output noise from the differential pre-amp is:
The factor ’2 ’ appears here because of differential output.
DIFFERENTIAL ANALOG-TO-DIGITAL DRIVER
V
i
i
i
k
T
R
n
non-inv
inv
n
+
FIGURE 3. Circuit for Differential A/D Driver
Input referred voltage noise
Input referred current noise
Input referred non-inverting current noise
Input referred inverting current noise
Boltzmann’s constant, K = 1.38 x 10
Resistor temperature in k
Source resistance at the non-inverting input
to balance offset voltage, typically very small
for this inverting summing applications
−23
20029239