MAX4090 View Datasheet(PDF) - Maxim Integrated
Part Name
Description
Manufacturer
MAX4090 Datasheet PDF : 17 Pages
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3V/5V, 6dB Video Buffer with Sync-Tip Clamp
and 150nA Shutdown Current
VIDEO
CURRENT
DAC
3-POLE RECONSTRUCTION LPF
C3
6.8pF
R1
150Ω
L1
4.7μH
C1
120pF
C2
120pF
R2
150Ω
Figure 4. 3rd-Order Butterworth LPF with MAX4090
RIS
49.9Ω
C4
0.1μF
VCC
VCC
IN
OUT
MAX4090
SHDN
FB
GND
VCC
C7
1μF
R3
75Ω
VOUT
Table 2. Bench Measurement Values
R1 = R2 C1
(Ω)
(pf)
75
330
150
150
200
120
300
82
L1
(µH)
1.8
3.9
4.7
8.2
RIS
(Ω)
3dB ATTENUATION
BW AT 27MHz
(MHz)
(dB)
0
8.7
20
50
9.0
20
50
9.3
22
100 8.7
20
Table 3. 3rd-Order Butterworth Lowpass
Filter Normalized Values
Rn1 = Rn2
(Ω)
1
Cn1 (F)
0.923
Cn2 (F)
0.923
Cn3 (F)
0.06
Ln1 (H)
1.846
Table 4. Bench Measurement Values
R1 = R2 (Ω)
75
150
300
C1 (pF)
220
120
56
C2 (pF)
220
120
56
C3 (pF)
15.0
6.8
3.3
L (µH)
2.2
4.7
10.0
RIS (Ω)
0
50
100
3dB BW (MHz)
9.3
8.9
9.0
ATTENUATION AT
27MHz (dB)
43
50
45
Sag Correction
In a 5V application, the MAX4090 can use the sag con-
figuration if an AC-coupled output video signal is
required. Sag correction refers to the low-frequency
compensation for the highpass filter formed by the
150Ω load and the output capacitor. In video applica-
tions, the cutoff frequency must be low enough to pass
the vertical sync interval to avoid field tilt. This cutoff
frequency should be less than 5Hz, and the coupling
capacitor must be very large in normal configuration,
typically > 220µF. In sag configuration, the MAX4090
eliminates the need for large coupling capacitors, and
instead requires two 22µF capacitors (Figure 6) to
reach the same performance as the large capacitor.
Bench experiments show that increasing the output
coupling capacitor C5 beyond 47µF does not improve
the performance. If the supply voltage is less than 4.5V,
the sag correction is not recommended for the
MAX4090.
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