MAX261AENG Maxim Integrated Products, MAX261AENG Datasheet - Page 7

• 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 1. Filter Block Diagram (One Second-Order Section)
Each MAX260/MAX261/MAX262 contains two second-
order switched-capacitor active filters. Figure 1 shows
the filter's state variable topology, employed with two
cascaded integrators and one summing amplifier. The
MAX261 and MAX262 also contain an uncommitted
amplifier. On-chip switches and capacitors provide
feedback to-control each filter section's f
Internal capacitor ratios are primarily responsible for
the accuracy of these parameters. Although these
switched-capacitor networks (SCN) are in fact sampled
systems, their behavior very closely matches that of
continuous filters, such as RC active filters. The ratio of
the clock frequency to the filter center frequency
(f
variable response is maintained.
The MAX262 uses a lower range of sampling (f
ratios than the MAX260 or MAX261 to allow higher
operating f
reduced sample rates result in somewhat more devia-
tion from ideal continuous filter parameters than with
the MAX260/MAX261. However, these differences can
be compensated using Figure 20 (see Application
Hints) or Maxim's filter design software.
The MAX260 employs auto-zero circuitry not included
in the MAX261 or MAX262. This provides improved DC
characteristics, and improved low-frequency perform-
CLK
/f
0
) is kept large so that ideal second-order state-
0
IN
frequencies and signal bandwidths. These
SCN = SWITCH-CAPACITOR NETWORK
_______________________________________________________________________________________
S1
M0
SELECT
MODE
SCN
S2
M1
S3
Introduction
(TABLE 3)
Q0–Q6
Microprocessor Programmable
SCN
SCN
+
-
0
and Q.
CLK
SCN
/f
0
)
+
S1
Universal Active Filters
Σ
ance at the expense of high-end f
width. The N/HP/AP outputs of the MAX260 are internal-
ly sample-and-held as a result of its auto-zero
operation. Signal swing at this output is somewhat
reduced as a result (MAX260 only). See Table 1 for
bandwidth comparisons of the three filters.
Maxim also provides design programs that aid in con-
verting filter response specifications into the f
program codes used by the MAX260 series devices.
This software also precompensates f
sample rates are used.
It is important to note that, in all MAX260 series filters,
the filter's internal sample rate is one half the input
clock rate (CLK
by two. All clock-related data, tables, and other dis-
cussions in this data sheet refer to the frequency at the
CLK
unless specifically stated otherwise.
The MAX260, MAX261, and MAX262, with Maxim's filter
design software, greatly simplify the design procedures
for many active filters. Most designs can be realized
using a three-step process described in this section. If
the design software is not used, or if the filter complexi-
ty is beyond the scope of this section, refer to the
remainder of this data sheet for more detailed applica-
tions and design information.
S2
-
-
S3
A
or CLK
Quick Look Design Procedure
∫
SAMPLE-HOLD
MAX260 ONLY
B
input, i.e., twice the internal sample rate,
A
or CLK
(TABLE 2)
S-H
F0–F5
∫
B
) due to an internal division
N/HP/AP
BP
LP
0
0
and signal band-
and Q when low
0
and Q
7