Rainbow Electronics MAX7480 User Manual
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General Description
The MAX7480 8th-order, lowpass, Butterworth,
switched-capacitor filter (SCF) operates from a single
+5V supply. The device draws only 2.9mA of supply
current and allows corner frequencies from 1Hz to
2kHz, making it ideal for low-power post-DAC filtering
and anti-aliasing applications. The MAX7480 features a
shutdown mode, which reduces the supply current to
0.2µA.
Two clocking options are available: self-clocking
(through the use of an external capacitor) or external
clocking for tighter corner-frequency control. An offset
adjust pin allows for adjustment of the DC output level.
The MAX7480 Butterworth filter provides a maximally
flat passband response. The fixed response simplifies
the design task to selecting a clock frequency.
Applications
ADC Anti-Aliasing
Post-DAC Filtering
Features
♦ 8th-Order, Lowpass Butterworth Filter
♦ Low Noise and Distortion: -73dB THD + Noise
♦ Clock-Tunable Corner Frequency (1Hz to 2kHz)
♦ 100:1 Clock-to-Corner Ratio
♦ +5V Single-Supply Operation
♦ Low Power
2.9mA (Operating Mode)
0.2µA (Shutdown Mode)
♦ Available in 8-Pin SO/DIP Package
♦ Low Output Offset: ±5mV
MAX7480
8th-Order, Lowpass, Butterworth,
Switched-Capacitor Filter
________________________________________________________________
Maxim Integrated Products
1
OS
OUTV
DD
1
2
87CLK
SHDNIN
GND
COM
SO/DIP
TOP VIEW
3
4
6
5
MAX7480
V
DD
IN
CLK
OUT
GND
INPUT
0.1µF
0.1µF
CLOCK
SHDN
OUTPUT
V
SUPPLY
COM
OS
MAX7480
Typical Operating Circuit
19-1416; Rev 0; 1/99
Pin Configuration
Ordering Information
PART
MAX7480ESA
MAX7480EPA -40°C to +85°C
-40°C to +85°C
TEMP. RANGE PIN-PACKAGE
8 SO
8 Plastic DIP
MAX7480
8th-Order, Lowpass, Butterworth,
Switched-Capacitor Filter
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VDD= +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF from COM to GND, SHDN =
V
DD
, f
CLK
= 100kHz, TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at TA= +25°C.)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
VDDto GND..............................................................-0.3V to +6V
IN, OUT, COM, OS, CLK............................-0.3V to (V
DD
+ 0.3V)
SHDN........................................................................-0.3V to +6V
OUT Short-Circuit Duration...................................................1sec
Continuous Power Dissipation (T
A
= +70°C)
8-Pin SO (derate 5.88mW/°C above +70°C)................471mW
8-Pin DIP (derate 9.09mW/°C above +70°C)...............727mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10sec).............................+300°C
C
OSC
= 1000pF (Note 4)
VOS= 0 to (VDD- 1V) (Note 3)
SHDN = GND, V
COM
= 0 to V
DD
(Note 1)
Input, COM externally driven
fIN= 200Hz, VIN= 4Vp-p,
measurement bandwidth = 22kHz
VIN= V
COM
= V
DD
/ 2
V
COM
= V
DD
/ 2 (Note 2)
CONDITIONS
40 53 67f
OSC
Internal Oscillator Frequency
±0.1 ±10Input Leakage Current at OS
±0.1 ±10Input Leakage Current at COM
50 500C
L
10 1R
L
Resistive Output Load Drive
10Clock Feedthrough
75 125R
COM
Input Resistance at COM
100:1f
CLK
/f
C
Clock-to-Corner Ratio
0.001 to 2f
C
Corner Frequency
V
COM
1A
OS
OS Voltage Gain to OUT
-73THD+N
Total Harmonic Distortion
plus Noise
10Clock-to-Corner Tempco
0.25 V
DD
-
0.25Output Voltage Range
±5 ±25V
OFFSET
Output Offset Voltage
-0.1 0.15 0.3
DC Insertion Gain with
Output Offset Removed
MIN TYP MAX
SYMBOLPARAMETER
V
CLK
= 0 or 5V
0.5V
IL
Clock Input Low
V
DD
- 0.5V
IH
Clock Input High
±24 ±40I
CLK
Clock Input Current
V
V
µA
kHz
µA
µA
pF
kΩ
mVp-p
kΩ
V
V/V
dB
dB
mV
V
ppm/°C
kHz
UNITS
Maximum Capacitive Load at
OUT
COM Voltage Range
V
DD
/ 2 V
DD
/ 2 V
DD
/ 2
- 0.5 + 0.5
V
COM
±0.1V
OS
Input Voltage Range at OS V
V
DD
/ 2 V
DD
/ 2 V
DD
/ 2
- 0.2 + 0.2
FILTER CHARACTERISTICS
CLOCK
Output, COM internally biased
MAX7480
8th-Order, Lowpass, Butterworth,
Switched-Capacitor Filter
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VDD= +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, OS = COM, 0.1µF from COM to GND, SHDN =
V
DD
, f
CLK
= 100kHz, TA= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at TA= +25°C.)
CONDITIONS
MIN TYP MAX
SYMBOLPARAMETER
Measured at DC
SHDN = GND, CLK driven from 0 to V
DD
Operating mode, no load, IN = OS = COM
0.5V
SDL
SHDN Input Low
V
DD
- 0.5V
SDH
SHDN Input High
60PSRRPower-Supply Rejection Ratio
0.2 1I
SHDN
Shutdown Current
2.9 3.5Supply Current I
DD
4.5 5.5V
DD
Supply Voltage
V
V
dB
µA
mA
V
UNITS
SHDN Input Leakage Current V
SHDN
= 0 to V
DD
±0.1 ±10 µA
POWER REQUIREMENTS
SHUTDOWN
FILTER CHARACTERISTICS
(VDD= +5V, filter output measured at OUT, 10kΩ || 50pF load to GND at OUT, SHDN = VDD, V
COM = VOS = VDD/2, fCLK
= 100kHz, T
A
= T
MIN
to T
MAX
, unless otherwise noted. Typical values are at TA= +25°C.)
Note 1: The maximum f
C
is defined as the clock frequency f
CLK
= 100 · fCat which the peak SINAD drops to 68dB with a sinusoidal
input at 0.2f
C
.
Note 2: DC insertion gain is defined as ∆V
OUT
/ ∆VIN.
Note 3: OS voltages above V
DD
- 1V saturate the input and result in a 75µA typical input leakage current.
Note 4: f
OSC
(kHz) ≅ 53 · 103/ C
OSC
(pF).
fIN= 0.5f
C
-0.1 0.0
fIN= 2f
C
fIN= f
C
-3.5 -3.0 -2.5
Insertion Gain Relative to
DC Gain
-48 -43
fIN= 3f
C
dB
-76 -70
CONDITIONS UNITS
MIN TYP MAX
PARAMETER
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