Rainbow Electronics MAX7427 - Manual (Page 10)

MAX7426/MAX7427
5th-Order, Lowpass, Elliptic,
Switched-Capacitor Filters
10 ______________________________________________________________________________________
Characteristics table for the input voltage range of COM
and OS. Changing the voltage on COM or OS signifi-
cantly from midsupply reduces the dynamic range.
Power Supplies
The MAX7426 operates from a single +5V supply, and
the MAX7427 operates from a single +3V supply.
Bypass V
DD
to GND with a 0.1µF capacitor. If dual
supplies are required, connect COM to the system
ground and GND to the negative supply. Figure 4
shows an example of dual-supply operation. Single-
supply and dual-supply performance are equivalent.
For either single-supply or dual-supply operation, drive
CLK and SHDN from GND (V- in dual-supply operation)
to V
DD . Use the MAX7427 for ±2.5, and use the
MAX7426 for ±1.5V. For ±5V dual-supply applications,
refer to the MAX291/MAX292/MAX295/MAX296 and
MAX293/MAX294/MAX297 data sheets.
Input Signal Amplitude Range
The optimal input signal range is determined by observ-
ing the voltage level at which the signal-to-noise plus
distortion (SINAD) ratio is maximized for a given corner
frequency. The Typical Operating Characteristics show
the THD + Noise response as the input signal’s peak-to-
peak amplitude is varied.
Anti-Aliasing and Post-DAC Filtering
When using the MAX7426/MAX7427 for anti-aliasing or
post-DAC filtering, synchronize the DAC (or ADC) and
the filter clocks. If the clocks are not synchronized,
beat frequencies may alias into the desired passband.
Harmonic Distortion
Harmonic distortion arises from nonlinearities within the
filter. These nonlinearities generate harmonics when a
pure sine wave is applied to the filter input. Table 2 lists
typical harmonic distortion values with a 10k
Ω load at
T A = +25°C.
V DD
V+
V-
IN
CLK
GND
INPUT
OUTPUT OUT
0.1 µF
CLOCK
*CONNECT SHDN TO V- FOR LOW-POWER SHUTDOWN MODE.
SHDN
COM
OS
0.1 µF
MAX7426
MAX7427
*
V+
V-
Figure 4. Dual-Supply Operation
Table 2. Typical Harmonic Distortion
FILTER
f IN
(Hz)
V IN
(Vp-p)
2nd 4th
f CLK
(kHz)
TYPICAL HARMONIC DISTORTION (dB)
3rd 5th
MAX7426
1k
200
4
500
100
-73 -71
-88
1k
-90
-92
MAX7427
200
2
500
100
-87
-90
-90
-90
-82
-86
-86
-87
-88
-90
-90
TRANSISTOR COUNT: 1457
PROCESS: BiCMOS
Chip Information