LTC2445 datasheet(16/28 Pages) LINER

16 / 28 page

LTC2444/LTC2445/

LTC2448/LTC2449

sn2444589 2444589fs

External Serial Clock, Single Cycle Operation

(SPI/MICROWIRE Compatible)

This timing mode uses an external serial clock to shift out

the conversion result and a CS signal to monitor and

control the state of the conversion cycle, see Figure 4.

The serial clock mode is selected by the EXT pin. To select

the external serial clock mode, EXT must be tied low.

The serial data output pin (SDO) is Hi-Z as long as CS is

HIGH. At any time during the conversion cycle, CS may be

pulled LOW in order to monitor the state of the converter.

While CS is pulled LOW, EOC is output to the SDO pin.

EOC = 1 (BUSY = 1) while a conversion is in progress and

EOC = 0 (BUSY = 0) if the device is in the sleep state.

Independent of CS, the device automatically enters the low

power sleep state once the conversion is complete.

When the device is in the sleep state (EOC = 0), its

conversion result is held in an internal static shift regis-

ter. The device remains in the sleep state until the first

rising edge of SCK is seen. Data is shifted out the SDO pin

on each falling edge of SCK. This enables external circuitry

to latch the output on the rising edge of SCK. EOC can be

latched on the first rising edge of SCK and the last bit of

the conversion result can be latched on the 32nd rising

edge of SCK. On the 32nd falling edge of SCK, the device

begins a new conversion. SDO goes HIGH (EOC = 1) and

BUSY goes HIGH indicating a conversion is in progress.

At the conclusion of the data cycle, CS may remain LOW

and EOC monitored as an end-of-conversion interrupt.

Alternatively, CS may be driven HIGH setting SDO to Hi-Z

and BUSY monitored for the completion of a conversion.

Figure 4. External Serial Clock, Single Cycle Operation

MSB

BIT 28 BIT 27 BIT 26 BIT 25 BIT 24 BIT 23 BIT 22 BIT 21

BIT 20 BIT 19

BIT 0

LSB

Hi-Z

2444 F05

SIG

BIT 29

“0”

BIT 30

EOC

Hi-Z

SCK

(EXTERNAL)

SDI

SDO

BUSY

BIT 31

SGL

OSR3

OSR2

OSR1

OSR0

TWOX

ODD

12345

CONVERSION

SLEEP

DATA OUTPUT

CONVERSION

TEST EOC

VCC

REF+

REF–

CH0

CH7

CH8

CH15

COM

SCK

SDI

SDO

GND

1,4,5,6,31,32,33

REFERENCE

VOLTAGE

0.1V TO VCC

ANALOG

INPUTS

= EXTERNAL OSCILLATOR

= INTERNAL OSCILLATOR

1µF

2.7V TO 5.5V

LTC2448

4-WIRE

SPI INTERFACE

•

BUSY

APPLICATIO S I FOR ATIO

LTC2445 Datenblatt(PDF) 16 Page - Linear Technology

LTC2445 Datenblatt(HTML) 16 Page - Linear Technology

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

Datenblatt Download

Link URL