MAX271EWG(2012) 查看數據表（PDF） - Maxim Integrated

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MAX271EWG
(Rev.:2012)

Digitally-Programmed, Dual 2nd-Order Continuous Lowpass Filter

Maxim Integrated 

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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