LTC2602 datasheet(20/26 Pages) LINER

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LTC2311-16

231116fa

For more information www.linear.com/LTC2311-16

APPLICATIONS INFORMATION

frequency. Figure 16 shows that the LTC2311-16 achieves

a typical SINAD of 81dB at a 5MHz sampling rate with a

2.2MHz input.

POWER CONSIDERATIONS

The LTC2311-16 requires two power supplies: the 5V

power supply (VDD), and the digital input/output interface

power supply (OVDD). The flexible OVDD supply allows

the LTC2311-16 to communicate with any digital logic

operating between 1.8V and 2.5V. When using LVDS I/O,

the OVDD supply must be set to 2.5V.

Power Supply Sequencing

The LTC2311-16 does not have any specific power sup-

ply sequencing requirements. Care should be taken to

adhere to the maximum voltage relationships described

in the Absolute Maximum Ratings section. The LTC2311-

16 has a power-on-reset (POR) circuit that will reset the

LTC2311-16 at initial power-up or whenever the power

supply voltage drops below 2V. Once the supply voltage

re-enters the nominal supply voltage range, the POR will

reinitialize the ADC. No conversions should be initiated

until 10ms after a POR event to ensure the reinitialization

period has ended. Any conversions initiated before this

time will produce invalid results.

Figure 16. 32k Point FFT of the LTC2311-16

SNR = 81.6dB

THD = –90dB

SINAD = 81.1dB

SFDR = 96dB

FREQUENCY (MHz)

0.5

1.5

2.5

–140

–120

–100

–80

–60

–40

–20

231116 F16

Figure 17. Power Supply Current of the LTC2311-16

Versus Sampling Rate

Signal-to-Noise Ratio (SNR)

The signal-to-noise ratio (SNR) is the ratio between the

RMS amplitude of the fundamental input frequency and

the RMS amplitude of all other frequency components

except the first five harmonics and DC. Figure 16 shows

that the LTC2311-16 achieves a typical SNR of greater

than 81dB at a 5MHz sampling rate with a 2.2MHz input.

Total Harmonic Distortion (THD)

Totalharmonicdistortion(THD)istheratiooftheRMSsum

ofallharmonicsoftheinputsignaltothefundamentalitself.

The out-of-band harmonics alias into the frequency band

between DC and half the sampling frequency (fSMPL/2).

THD is expressed as:

THD=20log

V22 + V32 + V42 +…+ VN2

where V1 is the RMS amplitude of the fundamental

frequency and V2 through VN are the amplitudes of the

second through Nth harmonics. The THD specifications

for the LTC2311-16 consider the first seven harmonics

(i.e. N=7). Figure 16 shows that the LTC2311-16 achieves

a typical THD of –90dB at a 5MHz sampling rate with a

2.2MHz input.

SAMPLE FREQUENCY (Msps)

231116 G16

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