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PDF MAX7490CEE Data sheet ( Hoja de datos )
| Número de pieza | MAX7490CEE | |
| Descripción | Dual Universal Switched-Capacitor Filters | |
| Fabricantes | Maxim Integrated | |
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19-1768; Rev 0; 7/00
Dual Universal Switched-Capacitor Filters
General Description
The MAX7490/MAX7491 consist of two identical low-
power, low-voltage, wide dynamic range, Rail-to-Rail®,
2nd-order switched-capacitor building blocks. Each of
the two filter sections, together with two to four external
resistors, can generate all standard 2nd-order func-
tions: bandpass, lowpass, highpass, and notch (band
reject). Three of these functions are simultaneously
available. Fourth-order filters can be obtained by cas-
cading the two 2nd-order filter sections. Similarly, high-
er order filters can easily be created by cascading
multiple MAX7490/MAX7491s.
Two clocking options are available: self-clocking
(through the use of an external capacitor) or external
clocking for tighter cutoff frequency control. The clock-
to-center frequency ratio is 100:1. Sampling is done at
twice the clock frequency, further separating the cutoff
frequency and Nyquist frequency.
The MAX7490/MAX7491 have an internal rail splitter
that establishes a precise common voltage needed for
single-supply operation. The MAX7490 operates from a
single +5V supply and the MAX7491 operates from a
single +3V supply. Both devices feature a low-power
shutdown mode and come in a 16-pin QSOP package.
________________________Applications
Tunable Active Filters
Multipole Filters
ADC Anti-Aliasing
Post-DAC Filtering
Adaptive Filtering
Phase-Locked Loops (PLLs)
Set-Top Boxes
Features
o Dual 2nd-Order Filter in a 16-Pin QSOP Package
o High Accuracy
Q Accuracy: ±0.2%
Clock-to-Center Frequency Error: ±0.2%
o Rail-to-Rail Input and Output Operation
o Single-Supply Operation: +5V (MAX7490)
or +3V (MAX7491)
o Internal or External Clock
o Highpass, Lowpass, Bandpass, and Notch Filters
o Clock-to-Center Frequency Ratio of 100:1
o Internal Sampling-to-Center Frequency Ratio
of 200:1
o Center Frequency up to 40kHz
o Easily Cascaded for Multipole Filters
o Low-Power Shutdown: <1µA Supply Current
Ordering Information
PART
MAX7490CEE
MAX7490EEE
MAX7491CEE
MAX7491EEE
TEMP. RANGE
0°C to +70°C
-40°C to +85°C
0°C to +70°C
-40°C to +85°C
PIN-
PACKAGE
SUPPLY
VOLTAGE
(+V)
16 QSOP
16 QSOP
16 QSOP
16 QSOP
5
5
3
3
Pin Configuration
Typical Application Circuit appears at end of data sheet.
Rail-to-Rail is a registered trademark of Nippon Motorola, Ltd.
TOP VIEW
LPA 1
BPA 2
NA/HPA 3
INVA 4
SA 5
SHDN 6
GND 7
VDD 8
MAX7490
MAX7491
QSOP
16 LPB
15 BPB
14 NB/HPB
13 INVB
12 SB
11 COM
10 EXTCLK
9 CLK
________________________________________________________________ Maxim Integrated Products 1
For free samples and the latest literature, visit www.maxim-ic.com or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
1 page  
Dual Universal Switched-Capacitor Filters
ELECTRICAL CHARACTERISTICS—MAX7491 (continued)
(VDD = EXTCLK = +3V, fCLK = 625kHz, TA = TMIN to TMAX, 10kΩ || 50pF load to VDD/2 at LP_, BP_, and N_/HP_, SHDN = VDD, 0.1µF
from COM to GND, 50% duty-cycle clock input, COM = VDD/2. Typical values are at TA = +25°C, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
POWER REQUIREMENTS
Supply Voltage
VDD
2.7 3.6 V
Power-Supply Current
IDD
No load, mode 1, R1 = R3 = 50kΩ,
R2 = 10kΩ, Q = 5
3.5 4.0 mA
Shutdown Current
ISHDN SHDN = GND
1 µA
INTERNAL OP AMPS CHARACTERISTICS
Output Short-Circuit Current
±11 mA
DC Open-Loop Gain
Gain Bandwidth Product
Slew Rate
GBW
SR
RL ≥ 10kΩ, CL ≤ 50pF
RL ≥ 10kΩ, CL ≤ 50pF
RL ≥ 10kΩ, CL ≤ 50pF
130 dB
7 MHz
6 V/µs
Note 1: Resistive loading of the N_/HP_, LP_, BP_ outputs includes the resistors used for the filter implementation.
Note 2: Crosstalk between internal filter sections is measured by applying a 1VRMS 10kHz signal to one bandpass filter section input
and grounding the input of the other bandpass filter section. The crosstalk is the ratio between the output of the grounded
filter section and the 1VRMS input signal of the other section.
Note 3: Bandwidth of noise measurement is 80kHz.
Note 4: fOSC (kHz) = 135 x 103 / COSC (COSC in pF)
Typical Operating Characteristics
(VDD = +5V for MAX7490, VDD = +3V for MAX7491, fCLK = 625kHz, SHDN = EXTCLK = VDD, COM = VDD/2, Mode 1, R3 = R1 = 50kΩ,
R2 = 10kΩ, Q = 5, TA = +25°C, unless otherwise noted.)
2ND-ORDER BANDPASS FILTER
FREQUENCY RESPONSE
10
2ND-ORDER BANDPASS FILTER
PHASE RESPONSE
300
fCLK/fO DEVIATION vs. fCLK
0
0
-10
-20
-30
-40
-50
-60
1
10
FREQUENCY (kHz)
250
200
150
100
50 VDD = +5V
fCLK = 625kHz
Q=5
0
100 1
10
FREQUENCY (kHz)
-0.1
-0.2
-0.3
-0.4
-0.5
-0.6
-0.7
-0.8
100 100
VDD = 5V
VDD = 3V
1000
fCLK (kHz)
10,000
_______________________________________________________________________________________ 5
5 Page 
Dual Universal Switched-Capacitor Filters
CC
R3
R2
NS
BP LP
R1
VIN -
+
Σ
∫
∫
COM
Figure 2. Mode 1, 2nd-Order Filter Providing Notch, Bandpass,
and Lowpass Outputs
have to track Q). The notch and bandpass center fre-
quencies are identical. The notch output gain is the
same above and below the notch center frequency.
Mode 1 can also be used to make high-order Butter-
worth lowpass filters, low Q notches, and multiple-order
bandpass filters obtained by cascading identical
switched-capacitor sections.
Mode 1 Design Equations
fO = fCLK
100
fnotch = fO
Q = R3
R2
HOLP = −R2
R1
HOBP = −R3
R1
HON1(as f → 0Hz) = −R2
R1
HON2 (at f = fCLK / 2) = −R2
R1
Mode 1B
Figure 3 shows the configuration of Mode 1B. R5 and
R6 are added to lower the feedback voltage from the
lowpass output to the summing input. This allows the
clock-to-center frequency to be adjusted beyond the
nominal value. This mode essentially has the same
functions and speed as Mode 1 while providing a high-
Q with fCLK/fO ratios greater than the nominal value.
R1
VIN
CC
R6
R3 COM
R2
N
S
-
+
Σ
R5
∫
BP
∫
LP
COM
Figure 3. Mode 1B, 2nd-Order Filter Providing Notch, Bandpass,
and Lowpass Outputs
Mode 1B Design Equations
fO = fCLK
100
fn = fO
R6
R6 + R5
Q = R3 R6
R2 R6 + R5
HOLP = −R2 R6 + R5
R1 R6
HOBP = −R3
R1
HON1(as f → 0Hz) = −R2
R1
HON2 (at f = fCLK / 2) = −R2
R1
Mode 2
Figure 4 shows the configuration of Mode 2. Mode 2 is
a combination of Mode 1 and Mode 3. In this mode,
fCLK/fO is always less than the part’s nominal ratio.
However, it provides less sensitivity to resistor toler-
ances than does Mode 3. It has a highpass notch out-
put where the notch frequency depends solely on the
clock frequency.
______________________________________________________________________________________ 11
11 Page | ||
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| PDF Descargar | [ Datasheet MAX7490CEE.PDF ] | |
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