MAX270(2012) 查看數據表（PDF） - Maxim Integrated

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MAX270
(Rev.:2012)

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

Maxim Integrated 

MAX270/MAX271

Digitally-Programmed, Dual

2nd-Order Continuous Lowpass Filter

MAX270 Control Interlace

The A0 pin is a three-level input that selects the memory

tWS

tWH

addresses for updating cutoff frequency data in FP mode:

CS

A0

Logic Low

Logic High

SELECTS

Filter B

Filter A

Figure 2 shows µP-mode interface timing.

Connecting A0 to the negative supply selects pin-strap

mode. Pin-strap mode allows filter programming with

no timing requirements. Internal memory latches are

disabled, permitting filters A and B to be programmed

directly to fC data strapped on D0–D6. This mode dis-

ables CS and WR controls, and filters A and B are pro-

grammed to the same fC.

A low level on the SHDN pin shuts down all amplifiers

and disconnects OUTA, OUTB, and OP OUT. Current

consumption drops to less than 15µA in this mode.

MAX271 Control Interlace

Connecting the MODE pin to GND or V- selects the

µP mode. In this mode, addressable program memory

controls filter cutoff frequency programming and all T/H

functions, except T/H. See the Figure 2 for timing charac-

teristics. Table 2 describes available functions:

WR

tAS

ADDRESS

(A0, A1)

tDS

DATA

(D0-D6)

tWR

tAH

tDH

NOTE : ALL DIGITAL INPUTS ARE LEVEL-SENSITIVE. WHEN WR AND CS ARE BOTH LOW,

THE DATA INPUT LATCHES ARE TRANSPARENT. AND THE FILTERS ARE

PROGRAMMED TO THE DATA ON D0–D6

Figure 2. MAX270/MAX271 Digital Timing Diagram

In FP mode, SHDN, T/H A/B, and T/H EN pins are dis-

abled. T/H remains enabled and performs the T/H track-

ing/holding function.

Tying MODE to V+ selects pin-strap mode. In this mode,

both memory latches are transparent, and data on D0–D6

controls the fC of filters A and 8 directly (filters A and 8

are programmed to the same fC). Pin strap D0–D6 for

operation without FP. A0, A1, CS, and WR are disabled.

Table 2. MAX271 µP-Mode Interface

A1

A0

06

05 04

03

02

01

D0

FUNCTION

0

0

7-bit fC data

Selects filter A

0

1

7-bit fC data

Selects filter B

1

0

X

X

X

X

X

X

0 T/H OUT disabled

1

0

X

X

X

X

X

X

1 T/H OUT enabled

1

0

X

X

X

X

X

0

X Selects OUTB as input to T/H

1

0

X

X

X

X

X

1

X Selects OUTA as input to T/H

1

1

X

X

X

X

X

X

0

Filter shutdown mode. All outputs floated, 15μA

max supply current

1

1

X

X

X

X

X

X

1 Removes filter from shutdown mode

X = Don't care

Maxim Integrated

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