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LTC2326-16

232616fa

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

applicaTions inForMaTion

Figure 5b. Using the LTC6655-2.048 as an External Reference

Figure 5c. Overdriving REFBUF Using the LTC6655-5

Figure 6. CNV waveform Showing Burst Sampling

of the output code. If an external reference is used to

overdrive REFBUF, the fast settling LTC6655-5 reference

is recommended.

Internal Reference Buffer Transient Response

Foroptimumtransientperformance,theinternalreference

buffer should be used. The internal reference buffer uses a

proprietary design that results in an output voltage change

atREFBUFoflessthan0.25LSBwhenrespondingtoasud-

denburstofconversions.Thismakestheinternalreference

bufferoftheLTC2326-16trulysingle-shotcapablesincethe

first sample taken after idling will yield the same result as

a sample taken after the transient response of the internal

reference buffer has settled. Figure 7 shows the transient

responses of the LTC2326-16 with the internal reference

buffer and with the internal reference buffer overdriven by

the LTC6655-5, both with a bypass capacitance of 47μF.

rate and output code. In applications where a burst of

samples is taken after idling for long periods, as shown in

Figure 6, IREFBUF quickly goes from approximately 390µA

to a maximum of 0.6mA for REFBUF = 5V at 250ksps. This

step in DC current draw triggers a transient response in

the external reference that must be considered since any

deviation in the voltage at REFBUF will affect the accuracy

Figure 7. Transient Response of the LTC2326-16

LTC2326-16

BANDGAP

REFERENCE

LTC6655-2.048

232616 F05b

47µF

2.7µF

6.5k

REFBUF

REFIN

15k

6.5k

REFERENCE

BUFFER

GND

–

LTC2326-16

GND

BANDGAP

REFERENCE

LTC6655-5

232616 F05c

47µF

6.5k

REFBUF

REFIN

15k

6.5k

REFERENCE

BUFFER

–

TIME (µs)

0.5

–0.5

–1.0

232616 F07

–2.0

–1.5

900

800

700

600

500

400

300

200

100

1000

INTERNAL REFERENCE BUFFER

EXTERNAL SOURCE ON REFBUF

CNV

IDLE

PERIOD

IDLE

PERIOD

232616 F06

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