MAX4450EVKIT Maxim Integrated, MAX4450EVKIT Datasheet - Page 3

• Manufacturer Part Number: MAX4450EVKIT
• Description: Amplifier IC Development Tools Evaluation Kit for the MAX4450
• Manufacturer: Maxim Integrated
• Series: MAX4450, MAX4451r

Specifications of MAX4450EVKIT

• Operating Supply Voltage: 5 V or 9 V

Figure 3. Multiburst Measurement of the EV Kit Circuit
for the NTSC Composite format. The results are shown
in Figures 3 and 4 for multiburst and differential gain/dif-
ferential phase (DG/DP), respectively. The bandwidth
was measured using the HP4195A spectrum analyzer to
show the out-of-band insertion loss and the results are
shown in Figure 5. The bandwidth of the filter is a func-
tion of the components’ value and their tolerances but
the DG/DP is indicative of the excellent gain and phase
linearity of the MAX4450 itself. The linearity combined
with the 175MHz large-signal bandwidth, and the
50MHz, 0.1dB large-signal bandwidth, make the
MAX4450 an excellent choice for all video applications.
The MAX4450 EV kit circuit’s output bandwidth is
5.25MHz at -3dB point and has an insertion loss
greater than 20dB at 13.5MHz and greater than 40dB
at 27MHz. Figure 5 illustrates the Signal Gain vs. Input
Signal Frequency of the EV kit’s filtering circuit. The
group delay variation across the bandwidth is 25ns or
less and can be used for all of the video formats (RGB,
Component, and Composite Video).
To preserve the quality of the video waveform it is
important that the filter’s group delay variation and the
group delay differential between filters, be as low as
possible. To accomplish that, some means of adjusting
group delay without affecting bandwidth is required.
The addition of R8 in series with C3 (see Figure 9) cre-
ates a lag-lead network. By keeping the sum of R3 and
R8 approximately equal to the original R3 value, the
dominant pole frequency is not affected, preserving the
bandwidth. As the value of R3 increases, a “lead” term
is introduced, reducing the rate of change of the
phase, and consequentially, the group delay.
-0.5
-1.0
-1.5
-2.0
1.0
0.5
0
0
0.5
_______________________________________________________________________________________
1.0
FREQUENCY (MHz)
MULTIBURST
1.5
2.0
2.5
3.0
3.5
4.0
Output
MAX4450 Evaluation Kit
In the circuit shown in Figure 9, the average group
delay variation across the filters bandwidth for R8 = 0,
and R3 = 332Ω is about 20ns at 4.5MHz (see Figure 6).
Raising R8 to 31.6Ω and lowering R3 to 301Ω drops the
group delay variation to about 10ns at 4.5MHz (see
Figure 7), and to <3ns at 4.5MHz for R3 = 274Ω, and
R8 = 59Ω (see Figure 8). This slightly affects the band-
edge selectivity, <0.5dB, but the -3dB bandwidth
remains unchanged, as shown in Table 1.
The MAX4450 EV kit circuit’s input is DC-coupled and
resistor R11 insures a path to ground for the input cur-
rent. When the circuit is driven from a low-impedance
source, resistor R11 may be removed to make the cir-
cuit a high-impedance load for the preceding stage.
Resistor R7 is used to simulate a back-terminated coax
and a 75Ω resistor should be installed if an external
load is not applied.
Figure 4. Differential Gain/Differential Phase Measurement of
EV Kit Circuit
Table 1. Group Delay Results with Varying
Resistor Values
R3 (Ω)
332
301
274
CONFIGURATION
RESISTOR
-0.5
-1.0
-0.5
-1.0
1.0
0.5
1.0
0.5
0
0
0
0
0 (shorted)
DIFFERENTIAL GAIN AND PHASE
R8 (Ω)
31.6
1
1
59
2
2
STEP
STEP
3
3
DELAY (ns)
AVERAGE
SIGNAL FREQUENCY AT
GROUP
25
15
4
4
7
4.5MHz
5
5
Termination
6
6
LOSS (dB)
SIGNAL
-2.1
-2.2
-2.4
3