MAX271(2012) Ver la hoja de datos (PDF) - Maxim Integrated
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MAX271 Datasheet PDF : 16 Pages
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MAX270/MAX271
Digitally-Programmed, Dual
2nd-Order Continuous Lowpass Filter
INA 5
D0-D6
17-23
V+
V-
GND
2
6
10
3 OUTA
EN
DIRECT
CONTROL
EN
1 T/H OUT
INB 7
EN
9 OUTB
16 15 14 12
A0* A1* CS* WR*
MAX270
*PIN HAS NO FUNCTION IN PIN-STRAP MODE.
Figure 1c. MAX271 Block Diagram—Pin-Strap Mode
4
11
24
SHDN* T/H* T/H
A/B
PIN-STRAP
MODE
13 8
T/H* MODE
EN
TO GND OR V-
Filter Programming
Cutoff Frequency
fC is the frequency of 3dB attenuation in the filter
response.
Table 1 shows how data pins D0–D6 allow programming
of 128 cutoff frequencies from 1kHz to 25kHz.
The equations for calculating fC from the programmed
code are as follows:
fC
=
87.5
87.5 − CODE
x 1kHz
for codes 0− 63
(fC =1kHz to 3.57kHz)
fC
262.5
=
137.5 − CODE
x 1kHz
for codes 64 − 127
(fC = 3.57kHz to 25kHz)
where CODE is the data on pins D0–D6 (0–127). D6 is
the most significant bit (MSB).
Actual cutoff frequencies are subject to some error for
each programmed code. Highest accuracy occurs at
CODE = 0 where filters are trimmed for a 1kHz cut-
off frequency. At higher codes, CODE vs. fC errors
increase; the frequency error at CODE = 127 {highest
code) remains typically within Q9.5%. This means that
the actual filter cutoff frequency, when programmed to
CODE = 127, falls between 22.63kHz and 27.38kHz.
Maxim Integrated
9
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