LTC2360HS6 データシートの表示（PDF） - Linear Technology

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LTC2360HS6

100ksps/250ksps/500ksps, 12-Bit Serial ADCs in TSOT-23

Linear Technology 

LTC2360/LTC2361/LTC2362

APPLICATIONS INFORMATION

Input Filtering and Source Impedance

The noise and the distortion of the input amplifier and

other circuitry must be considered since they will add to

the LTC2360/LTC2361/LTC2362 noise and distortion. The

small-signal bandwidth of the sample-and-hold circuit is

10MHz. Any noise or distortion products that are pres-

ent at the analog inputs will be summed over this entire

bandwidth. Noisy input circuitry should be filtered prior

to the analog inputs to minimize noise. A simple 1-pole

RC filter is sufficient for many applications. For example,

Figure 14 shows a 220pF capacitor from AIN to ground

and a 51Ω source resistor to limit the input bandwidth

to 10MHz. The 220pF capacitor also acts as a charge

reservoir for the input sample-and-hold and isolates the

ADC input from sampling-glitch sensitive circuitry. High

quality capacitors and resistors should be used since these

components can add distortion. NPO and silvermica type

dielectric capacitors have excellent linearity. Carbon surface

mount resistors can generate distortion from self heating

and from damage that may occur during soldering. Metal

film surface mount resistors are much less susceptible to

both problems. When high amplitude unwanted signals

are close in frequency to the desired signal frequency,

a multiple pole filter is required. High external source

resistance, combined with the 20pF of input capacitance,

will reduce the rated 10MHz bandwidth and increase

acquisition time beyond 500ns.

Reference Input

On the TS8 package of the LTC2360/LTC2361/LTC2362,

the voltage on the VREF pin defines the full-scale range

of the ADC. The reference voltage can range from VDD

down to 1.4V.

Input Range

The analog input of the LTC2360/LTC2361/LTC2362 is

driven single-ended with respect to GND from a single

supply. The input may swing up to VDD for the S6 package

and to VREF for the TS8 package. The 0V to 2.5V range is

also ideally suited for single-ended input use with VDD or

VREF = 2.5V for single supply applications. If the difference

between the AIN input and GND exceeds VDD for the S6

package or VREF for the TS8 package, the output code will

stay fixed at all ones, and if this difference goes below 0V,

the output code will stay fixed at all zeros.

Figure 15 shows the ideal input/output characteristics for

the LTC2360/LTC2361/LTC2362. The code transitions oc-

cur midway between successive integer LSB values (i.e.,

0.5LSB, 1.5LSB, 2.5LSB, …, FS – 1.5LSB). The output

code is straight binary with 1LSB = VDD/4096 for the S6

package and 1LSB = VREF/4096 for the TS8 package.

111...111

111...110

2.2μF

220pF

51Ω

LTC2362

1

6

VDD CONV

2

5

GND SDO

3 AIN

SCK 4

236012 F14

Figure 14. RC Input Filter

000...001

000...000

0

1LSB

INPUT VOLTAGE (V)

FS – 1LSB

236012 F15

Figure 15. Transfer Characteristics

236012fa

17

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