LTC1098ACN8 datasheet(19/32 Pages) LINER

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LTC1096/LTC1096L

LTC1098/LTC1098L

10968fc

APPLICATIONS INFORMATION

Figure 3. LTC1098(L) Operation with DIN and DOUT Tied Together

Figure 4. Automatic Power Shutdown Between Conversions

Allows Power Consumption to Drop with Sample Rate

Figure 5. After a Conversion, When the Microprocessor

Drives CS High, the ADC Automatically Shuts Down Until the

Next Conversion. The Supply Current, Which Is Very Low

During cConversions, Drops to Zero in Shutdown

the data line and drive it low on the 4th falling CLK edge

after the start bit is received (see Figure 3). Therefore the

processor port line must be switched to an input before

this happens, to avoid a conﬂict.

In the Typical Applications section, there is an example of

interfacing the LTC1098(L) with DINand DOUT tied together

to the Intel 8051 MPU.

ACHIEVING MICROPOWER PERFORMANCE

With typical operating currents of 40μA and automatic

shutdown between conversions, the LTC1096/LTC1098

achieves extremely low power consumption over a wide

range of sample rates (see Figure 4). In systems that

convert continuously, the LTC1096/LTC1098 will draw

CLK

DATA (DIN/DOUT)

START

SGL/DIFF

ODD/SIGN

MSBF

•••

MSBF BIT LATCHED

BY LTC1098(L)

LTC1098(L) CONTROLS DATA LINE AND SENDS

A/D RESULT BACK TO MPU

MPU CONTROLS DATA LINE AND SENDS

MUX ADDRESS TO LTC1098(L)

PROCESSOR MUST RELEASE

DATA LINE AFTER 4TH RISING CLK

AND BEFORE THE 4TH FALLING CLK

LTC1098(L) TAKES CONTROL OF

DATA LINE ON 4TH FALLING CLK

10968 F03

its normal operating power continuously. Figure 5 shows

that the typical current varies from 40μA at clock rates

below 50kHz to 100μA at 500kHz. Several things must

be taken into account to achieve such a low power

consumption.

Sample Rate, fSAMPLE (kHz)

0.1

100

1000

100

10968 F04

TA = 25°C

VCC = 5V

CLOCK FREQUENCY (Hz)

120

140

100

10k

100k

10968 F05

100

0.002

TA = 25°C

VCC = 5V

ACTIVE (CS LOW)

SHUTDOWN (CS HIGH)

SUPPLY CURRENT vs CLOCK RATE FOR

ACTIVE AND SHUTDOWN MODES

Shutdown

Figures 1 and 2 show the operating sequence of the

LTC1096/LTC1098. The converter draws power when the

CS pin is low and powers itself down when that pin is high.

If the CS pin is not taken to ground when it is low and not

taken to supply voltage when it is high, the input buffers

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