MAX261AENG Maxim Integrated Products, MAX261AENG Datasheet - Page 21

• Manufacturer Part Number: MAX261AENG
• Description: Active Filter
• Manufacturer: Maxim Integrated Products

Specifications of MAX261AENG

• Number Of Channels: 2
• Cutoff Frequency: 57 KHz
• Supply Voltage (max): 12.6 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Supply Voltage (min): 4.74 V
• Package / Case: PDIP N-24
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 16. Power Supply and Input Connections for Single Supply Operation
mode 1 the maximum signal is 0 times the input signal,
the input should not exceed ±(2/Q)V, or ±1V in this case.
Typical wideband noise for MAX260 series devices is
0.5mV
independent of clock frequency. In multistage filters,
the section with the highest Q should be placed first for
lower output noise.
The output waveform of the MAX260 series and other
switched capacitor filters appears as a sampled signal
with stepping or “staircasing” of the output waveform
occurring at the internal sample rate (f
ping, if objectionable, can be removed by adding a sin-
gle-pole AC filter. With no input signal, clock-related
feedthrough is approximately 8mV
attenuated with an RC-smoothing filter as shown with
the MAX261 in Figure 17.
Some noise also can be generated at the filter outputs
by transitions at the logic inputs. If this is objectionable,
the digital lines should be buffered from the device by
logic gates as shown in Figure 6.
P-P
from DC to 100kHz. The noise is virtually
LEVELS
CMOS
LOGIC
Clock Feedthrough and Noise
______________________________________________________________________________________
WR
A0–A3
D0, D1
MAX260
MAX261
MAX262
P-P
. This can also be
GND
CLK
NOTE: OP-AMP LEVEL SHIFT CIRCUIT HAS A GAIN OF 0.5 FROM V*.
IN
IN
OR
V
V
A
B
+
-
Microprocessor Programmable
5V
0V
/2). This step-
4.7kΩ
4.7kΩ
4.7µF
NOTE
SEE
10kΩ
7.5kΩ
Universal Active Filters
+
-
TO GND PIN
0.1µF
The input to each filter is the switched capacitor circuit
shown in Figure 18. In the MAX260, the input capacitor
charges to the input voltage V
clock cycle. During the second half-cycle, its charge is
transferred to the feedback capacitor. The resultant
input impedance can be approximated by:
C
500kHz, R
fixed capacitance to ground.
The MAX261/MAX262 input structure is shown in Figure
19. Here C
switched, so the input resistance is 750 times larger
compared to the MAX260 (R
MAX261/MAX262 have a fixed capacitance of approxi-
mately 5pF to ground.
When low f
ed, deviation from ideal continuous filter response can
be noticeable in some designs. This is due to interac-
tion between Q and f
data in Figure 20 quantifies these differences. Since the
IN
is around 12pF, hence, for a clock frequency of
4.7µF
TO V+
R
10kΩ
2.5kΩ
IN
IN
0.1µF
A
CLK
= 1 / (C
= 333kΩ. The input also has about 5pF of
= 12pF and C
+5V
/f
0
f
0
ratios and low Q settings are select-
V
V
V
IN
IN
IN
and Q at Low Sample Rates
IN
0
f
at low f
CLK
0V
ANY DC
5V
0V
/ 2) = 2 / (C
B
= 0.016pF and only C
CLK
IN
Input Impedance
/f
IN
0
during the first half
ratios and Qs. The
= 250MΩ). The
IN
f
CLK
).
B
21
is