LTC1609I 查看數據表（PDF） - Linear Technology

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LTC1609I

16-Bit, 200ksps, Serial ADC with Multiple Input Ranges

Linear Technology 

LTC1609

W

FUNCTIONAL BLOCK DIAGRA

20k

R1IN

10k

R2IN

20k

5k

R3IN

4k

REF

2.5V REF

CAP

(2.5V)

AGND1

AGND2

DGND

REF BUF

INTERNAL

CLOCK

CSAMPLE

CSAMPLE

ZEROING SWITCHES

VANA

VDIG

16-BIT CAPACITIVE DAC

+

COMP

–

SUCCESSIVE APPROXIMATION

REGISTER

CONTROL LOGIC

CS

R/C

PWRD BUSY

SERIAL INTERFACE

DATA

DATACLK

SYNC

SB/BTC EXT/INT

1609 BD

TAG

APPLICATIO S I FOR ATIO

Conversion Details

The LTC1609 uses a successive approximation algorithm

and an internal sample-and-hold circuit to convert an

analog signal to a 16-bit serial output. The ADC is complete

with a precision reference and an internal clock. The

control logic provides easy interface to microprocessors

and DSPs. (Please refer to the Digital Interface section for

timing information.)

Conversion start is controlled by the CS and R/C inputs. At

the start of conversion the successive approximation

register (SAR) is reset. Once a conversion cycle has begun

it cannot be restarted.

During the conversion, the internal 16-bit capacitive DAC

output is sequenced by the SAR from the most significant

bit (MSB) to the least significant bit (LSB). Referring to

Figure 1, VIN is connected through the resistor divider to

the sample-and-hold capacitor during the acquire phase

and the comparator offset is nulled by the autozero switches.

In this acquire phase, a minimum delay of 2µs will provide

enough time for the sample-and-hold capacitor to acquire

8

the analog signal. During the convert phase, the autozero

switches open, putting the comparator into the compare

mode. The input switch switches CSAMPLE to ground,

injecting the analog input charge onto the summing junc-

tion. This input charge is successively compared with the

binary-weighted charges supplied by the capacitive DAC.

Bit decisions are made by the high speed comparator. At

RIN1

VIN

RIN2

SAMPLE CSAMPLE

HOLD

CDAC

DAC

VDAC

SAMPLE

SI

–

+

COMPARATOR

S

A

R

16-BIT

SHIFT REGISTER

1609 F01

Figure 1. LTC1609 Simplified Equivalent Circuit

1609fa

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