LTC2365 datasheet(18/24 Pages) LINER

18 / 24 page

LTC2365/LTC2366

23656f

SINGLE-ENDED ANALOG INPUT

Driving the Analog Input

The analog input of the LTC2365/LTC2366 is easy to drive.

The input draws only one small current spike while charg-

ing the sample-and-hold capacitor at the end of conver-

sion. During the conversion, the analog input draws only

a small leakage current. If the source impedance of the

driving circuit is low, then the input of the LTC2365/LT2366

can be driven directly. As source impedance increases,

so will acquisition time. For minimum acquisition time

with high source impedance, a buffer ampliﬁer should be

used. The main requirement is that the ampliﬁer driving

the analog input must settle after the small current spike

before the next conversion starts (settling time must be

less than 56ns for full throughput rate). While choosing

an input ampliﬁer, also keep in mind the amount of noise

and harmonic distortion the ampliﬁer contributes.

Choosing an Input Ampliﬁer

Choosing an input ampliﬁer is easy if a few requirements

are taken into consideration. First, to limit the magnitude

of the voltage spike seen by ampliﬁer from charging the

sampling capacitor, choose an ampliﬁer that has a low

output impedance (<100Ω) at the closed-loop bandwidth

frequency. For example, if an ampliﬁer is used in a gain

of 1 and has a unitygain bandwidth of 50MHz, then the

output impedance at 50MHz must be less than 100Ω. The

second requirement is that the closed-loop bandwidth must

be greater than 40MHz to ensure adequate small signal

settling for full throughput rate. If slower op amps are

used, more time for settling can be provided by increas-

ing the time between conversions. The best choice for an

op amp to drive the LTC2365/LTC2366 will depend on the

application. Generally, applications fall into two categories:

AC applications where dynamic speciﬁcations are most

critical and time domain applications where DC accuracy

and settling time are most critical. The following list is a

summary of the op amps that are suitable for driving the

LTC2365/LTC2366. (More detailed information is available

on the Linear Technology website at www.linear.com.)

APPLICATIONS INFORMATION

LTC2365 Datasheet(PDF) 18 Page - Linear Technology

LTC2365 Datasheet(HTML) 18 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

Datasheet Download

Link URL