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LTC2326-16

232616fa

For more information www.linear.com/LTC2326-16

applicaTions inForMaTion

Figure 9. Power Supply Current of the LTC2326-16

Versus Sampling Rate

it cannot be restarted until the conversion is complete.

For optimum performance, CNV should be driven by a

clean low jitter signal. Converter status is indicated by the

BUSY output which remains high while the conversion is

in progress. To ensure that no errors occur in the digitized

results, any additional transitions on CNV should occur

within 40ns from the start of the conversion or after the

conversion has been completed. Once the conversion has

completed, the LTC2326-16 powers down.

Acquisition

AproprietarysamplingarchitectureallowstheLTC2326-16

to begin acquiring the input signal for the next conver-

sion 527ns after the start of the current conversion. This

extends the acquisition time to 3.460µs, easing settling

requirements and allowing the use of extremely low power

ADC drivers. (Refer to the Timing Diagram.)

Internal Conversion Clock

The LTC2326-16 has an internal clock that is trimmed to

achieve a maximum conversion time of 3µs.

Auto Nap Mode

The LTC2326-16 automatically enters nap mode after a

conversion has been completed and completely powers

up once a new conversion is initiated on the rising edge of

CNV. During nap mode, only the ADC core powers down

and all other circuits remain active. During nap, data from

the last conversion can be clocked out. The auto nap mode

featurewillreducethepowerdissipationoftheLTC2326-16

as the sampling frequency is reduced. Since full power is

consumed only during a conversion, the ADC core of the

LTC2326-16remainspowereddownforalargerfractionof

the conversion cycle (tCYC) at lower sample rates, thereby

reducing the average power dissipation which scales with

the sampling rate as shown in Figure 9.

Sleep Mode

The auto nap mode feature provides limited power savings

since only the ADC core powers down. To obtain greater

power savings, the LTC2326-16 provides a sleep mode.

During sleep mode, the entire part is powered down

except for a small standby current resulting in a power

dissipation of 300μW. To enter sleep mode, toggle CNV

twice with no intervening rising edge on SCK. The part

will enter sleep mode on the falling edge of BUSY from

the last conversion initiated. Once in sleep mode, a rising

edge on SCK will wake the part up. Upon emerging from

sleep mode, wait tWAKE ms before initiating a conversion

to allow the reference and reference buffer to wake up

and charge the bypass capacitors at REFIN and REFBUF.

(Refer to the Timing Diagrams section for more detailed

timing information about sleep mode.)

DIGITAL INTERFACE

The LTC2326-16 has a serial digital interface. The flexible

OVDDsupplyallowstheLTC2326-16tocommunicatewith

any digital logic operating between 1.8V and 5V, including

2.5V and 3.3V systems.

The serial output data is clocked out on the SDO pin when

anexternalclockisappliedtotheSCKpinifSDOisenabled.

Clocking out the data after the conversion will yield the

best performance. With a shift clock frequency of at least

20MHz, a 250ksps throughput is still achieved. The serial

output data changes state on the rising edge of SCK and

can be captured on the falling edge or next rising edge of

SCK. D15 remains valid till the first rising edge of SCK.

The serial interface on the LTC2326-16 is simple and

straightforwardtouse.Thefollowingsectionsdescribethe

operation of the LTC2326-16. Several modes are provided

depending on whether a single or multiple ADCs share the

SPI bus or are daisy-chained.

SAMPLING FREQUENCY (kHz)

100

150

200

232616 F09

250

OVDD

VDD (IN+ = –10.24V)

VDD (IN+ = 10.24V)

VDD (IN+ = 0V)

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