User Manual

MAX7418–MAX7425
5th-Order, Lowpass,
Switched-Capacitor Filters
_______________________________________________________________________________________ 5
Note 1: The maximum f
C
is defined as the clock frequency f
CLK
= 100 x f
C
at which the peak S / (THD+N) drops to 68dB with a
sinusoidal input at 0.2f
C
. Maximum f
C
increases as V
IN
signal amplitude decreases.
Note 2: DC insertion gain is defined as ∆V
OUT
/ ∆V
IN
.
Note 3: MAX7418/MAX7421/MAX7422/MAX7425: f
OSC
(kHz) ≅ 87x10
3
/ C
OSC
(pF).
MAX7419/MAX7420/MAX7423/MAX7424: f
OSC
(kHz) ≅ 110x10
3
/ C
OSC
(pF).
Note 4: PSRR is the change in output voltage from a V
DD
of 4.5V and a V
DD
of 5.5V.
-70 -65f
IN
= 5f
C
-47.5 -43
-3.6 -3.0 -2.4f
IN
= f
C
f
IN
= 3f
C
-0.3 0
dB
f
IN
= 0.5f
C
PARAMETER MIN TYP MAX UNITSCONDITIONS
BUTTERWORTH FILTERS—MAX7420/MAX7424BUTTERWORTH FILTERS—MAX7420/MAX7424
FILTER CHARACTERISTICS
(V
DD
= +5V for MAX7418–MAX7421, V
DD
= +3V for MAX7422–MAX7425 filter output measured at OUT, 10kΩ
|| 50pF load to GND at
OUT, SHDN = V
DD
, f
CLK
= 2.2MHz, T
A
= T
MIN
to T
MAX
, unless otherwise noted.)
__________________________________________Typical Operating Characteristics
(V
DD
= +5V for MAX7418–MAX7421, V
DD
= +3V for MAX7422–MAX7425, f
CLK
= 2.2MHz, SHDN = V
DD
, V
COM
= V
OS
= V
DD
/ 2,
T
A
= +25°C, unless otherwise noted.)
-90
-60
-70
-80
-50
-40
-30
-20
-10
0
10
04020 60 80 100
MAX7418/MAX7422
FREQUENCY RESPONSE (ELLIPTIC, r = 1.6)
MAX7418 toc01
INPUT FREQUENCY (kHz)
GAIN (dB)
-60
-40
-50
-20
-30
0
-10
10
04020 60 80 100
MAX7419/MAX7423
FREQUENCY RESPONSE (BESSEL)
MAX7418 toc02
INPUT FREQUENCY (kHz)
GAIN (dB)
-80
-60
-70
-30
-40
-50
0
-10
-20
10
04020 60 80 100
MAX7420/MAX7424
FREQUENCY RESPONSE (BUTTERWORTH)
MAX7418 toc03
INPUT FREQUENCY (kHz)
GAIN (dB)
Insertion Gain Relative to
DC Gain