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RC6601
PRODUCT SPECIFICATION
6
Performance Curves
Figure 2. Amplitude Response—Default Setting
Figure 3. Attentuation and Group Delay
Figure 4. Amplitude Responses Over Programming Range
Figure 5. Frequency Programming Using V
f
and Passband Group Delay
10.0
0
-40.0
-60.0
.2
.4 .6.8 1
2
4
6 810
20
40
A
Frequency (MHz)
6
1
-1 (dB)
0
1 (dB)
2
3
4
5
6
350 (ns)
300 (ns)
250 (ns)
Frequency (MHz)
A
65-6601-06
G
10.0
0
-10.0
-20.0
-30.0
-40.0
-50.0
-60.0
-70.0
-80.0
-950 KHz
2
4 68 1
2
4 68 1
2
50 MHz
4
G
Frequency (Hz)
6
Vf = 1.9V
Vf = 0V
0
100
200
300
400
500
600
700
800
900
0.2
0.4
0.6
0.8
1
Vf (V)
P
1.2
1.4
1.6
1.8
2
65-6601-08
0
5
10
15
C
Application Discussion
The RC6601 is fully integrated in the sense that no critical
external components are required for the low pass filtering
function. For luminance filtering at a cut-off frequency of
5.5MHz, the only off-chip components are the decoupling
capacitors and termination resistors shown in Figure 6. The
part also provides temperature and supply independent band-
gap reference voltages (2.48V and 1.24V) that can be used
for setting the ADC converters or DACs in the system.
The programmable feature of the RC6601 makes it versatile
for use in applications with other standard cut-off frequen-
cies. There are three ways of changing the cut-off frequency.
1.
External Voltage setting on V
F
:
A higher voltage on
V
F
than 1.2V gives a lower frequency than 5.5MHz cut-
off. The highest frequency (above 10MHz) is obtained
by grounding the V
F
pin.
2.
Potentiometer at V
REF
(pin 8) and/or V
F
(pin 9):
There is an internal resistor divider of roughly 10K each
that sets the default voltage of 1.2V at half the value of
V
REF
. Using a lower value external pot of 1K–2K, the
internal setting can be overridden.
3.
Current Source/Sink at V
F
:
The typical current output
from a DAC can be tied to the V
F
pin to program the
cut-off frequency from a controller.
In applications requiring dynamic programming of the filter
cut-off, a combination of above techniques may be used. Use
of the RC6601 in such applications eliminates the need for
multiplexers and filter banks. The other adjustment possible
on the RC6601 is the output d.c. level. The output d.c. level
can be adjusted by connecting a potentiometer between pins
R
OS1
and R
OS2
(pins 11 and 12) and taking the center tap to
V
CC
. These adjustments are shown in Figure 7 below.