LTC2499 datasheet(23/34 Pages) LINER

23 / 34 page

LTC2499

2499fc

Figure 11. Equivalent Analog Input Circuit

32 bits are read out of the device or after a Stop command.

The following conversion will be performed using the

newly programmed data. In cases where the same speed

(1x/2x mode) and rejection frequency (50Hz, 60Hz, 50Hz

and 60Hz) is used but the channel is changed, a Stop or

Repeated Start may be issued after the ﬁrst byte (channel

selection data) is written into the device.

Discarding a Conversion Result and Initiating a New

Conversion with Optional Write

At the conclusion of a conversion cycle, a write cycle

can be initiated. Once the write cycle is acknowledged, a

Stop command will start a new conversion. If a new input

channel or conversion conﬁguration is required, this data

can be written into the device and a Stop command will

initiate the next conversion (see Figure 9).

Figure 10. Synchronize Multiple LTC2499s with a Global Address Call

Synchronizing Multiple LTC2499s with a Global

Address Call

In applications where several LTC2499s (or other I2C

delta-sigma ADCs from Linear Technology Corporation)

are used on the same I2C bus, all converters can be syn-

chronized through the use of a global address call. Prior

to issuing the global address call, all converters must have

completed a conversion cycle. The master then issues a

Start, followed by the global address 1110111, and a write

request. All converters will be selected and acknowledge

the request. The master then sends a write byte (optional)

followed by the Stop command. This will update the chan-

nel selection (optional) converter conﬁguration (optional)

and simultaneously initiate a start of conversion for all

delta-sigma ADCs on the bus (see Figure 10). In order

APPLICATIONS INFORMATION

IN+

IN–

10kΩ

INTERNAL

SWITCH

NETWORK

10kΩ

CEQ

12μF

10kΩ

IIN

–

REF+

IREF

IIN

IREF

–

2499 F11

SWITCHING FREQUENCY

fSW = 123kHz INTERNAL OSCILLATOR

fSW = 0.4 • fEOSC EXTERNAL OSCILLATOR

REF–

10kΩ

100Ω

INPUT

MULTIPLEXER

EXTERNAL

CONNECTION

100Ω

MUXOUTP

ADCINP

EXTERNAL

CONNECTION

MUXOUTN

ADCINN

IIN+

()

AVG

= IIN–

()

AVG

VIN(CM) VREF(CM)

0.5

•R

IREF+

()

AVG

1.5VREF + VREF(CM) –VIN(CM)

()

0.5 • REQ

–

VIN

VREF •REQ

where:

VREF = REF

+ REF

VREF(CM) =

REF+ –REF

VIN =IN

+ IN ,WHEREIN+ ANDIN ARE THE SELECTEDINPUT CHANNELS

VIN(CM) =

IN+ –IN

REQ = 2.71M INTERNAL OSCILLATOR 60Hz MODE

REQ = 2.98M INTERNAL OSCILLATOR 50Hz/60Hz MODE

REQ = 0.833•10

()/f

EOSC EXTERNAL OSCILLATOR

GLOBAL ADDRESS

SCL

SDA

LTC2499

…

ALL LTC2499s IN SLEEP

CONVERSION OF ALL LTC2499s

DATA INPUT

W ACK

WRITE (OPTIONAL)

2499 F10

LTC2499 Datasheet(PDF) 23 Page - Linear Technology

LTC2499 Datasheet(HTML) 23 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 29 30 31 32 33 34

Datasheet Download

Link URL