MAX4145 MAXIM [Maxim Integrated Products], MAX4145 Datasheet - Page 13

• Manufacturer Part Number: MAX4145
• Description: High-Speed, Low-Distortion, Differential Line Receivers
• Manufacturer: MAXIM [Maxim Integrated Products]

which appears inductive at high frequencies. This
inductance forms an L-C resonant circuit with the
capacitive load, which causes peaking in the frequency
response and degrades the amplifier’s phase margin.
The MAX4144/MAX4145/MAX4146 drive capacitive
loads up to 25pF without oscillation. However, some
peaking may occur in the frequency domain (Figure 4).
To drive larger capacitance and reduce ringing, add an
isolation resistor (R
and the load (Figure 5).
The value of R
capacitive load (Figures 6 and 7). With higher capaci-
Figure 7. MAX4145/MAX4146 Isolation Resistance vs.
Capacitive Load
Figure 5. Addition of R
20
18
16
14
12
10
8
6
4
0
ISO
A
MAX4144
MAX4145
MAX4146
V
depends on the circuit’s gain and the
______________________________________________________________________________________
= 10V/V
ISO
50
ISO
OUT
CAPACITIVE LOAD (pF)
) between the amplifier’s output
to Amplifier Output
100
R
ISO
150
200
C
LOAD
250
R
High-Speed, Low-Distortion,
LOAD
Differential Line Receivers
tive values, bandwidth is dominated by the RC network
formed by R
itself is much higher. Also note that the isolation resistor
forms a divider that decreases the voltage delivered to
the load.
The MAX4144/MAX4145/MAX4146 are well suited as
receivers in twisted-pair xDSL or NTSC/PAL video
applications. The standard 24AWG telephone wire
widely used in these applications is a lossy medium for
high-frequency signals. The losses in NTSC video
applications are almost 15dB per 1000 feet (Figure 8).
Figure 6. MAX4144 Isolation Resistance vs. Capacitve Load
Figure 8. 1000 Feet of AWG24 Twisted-Pair Telephone Cable
(Gain vs. Frequency)
-10
-15
-20
-25
-30
-35
15
10
-5
5
0
30
25
20
15
10
5
0
ISO
10k
0
and C
50
Twisted-Pair Line Receiver
CAPACITIVE LOAD (pF)
100k
L
FREQUENCY (Hz)
; the bandwidth of the amplifier
100
150
1M
200
10M
250
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