THS4521 Datasheet, PDF (48/65 Pages) Texas Instruments – VERY LOW POWER, NEGATIVE RAIL INPUT, RAIL-TO-RAIL OUTPUT, FULLY DIFFERENTIAL AMPLIFIER

THS4521, THS4522, THS4524
SBOS458H – DECEMBER 2008 – REVISED JUNE 2015
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9.2.2.2 Detailed Design Procedure
9.2.2.2.1 ADC Driver Performance: THS4521 and ADS8321 Combined Performance
To demonstrate achievable performance, the THS4521 is tested as the drive amplifier for the ADS8321 16-bit
SAR ADC. The ADS8321 offers excellent ac and dc performance, with ultra-low power and small size. The circuit
shown in Figure 86 was used to test the performance.
Data were taken using the ADS8321 at 100 kSPS with input frequencies of 2 kHz and 10 kHz and signal levels
that were -0.5 dBFS. FFT plots that illustrate the spectral performance are given in Figure 89 and Figure 90.
Tabulated ac analysis results are listed in Table 12 and compared to the ADS8321 data sheet typical
performance. Note the significant improvement in SFD using the THS4521 driver over just the ADC by itself.
1 kW
V_IN+
V_IN-
1 kW
1 kW
5V
THS4521
V_OCM
49.9 W
49.9 W
Open
0.22 mF
68 pF
1 nF
68 pF
-IN
ADS8321
+IN
1 kW
Figure 86. THS4521 and ADS8321 Test Circuit
Configuration
THS4521 and
ADS8321
ADS8321 Data
sheet (typ)
Tone
2 kHz
10 kHz
10 kHz
Table 12. AC Analysis
Signal (dBFS)
–0.5
–0.5
SNR (dBc)
86.7
85.2
THD (dBc)
–97.8
–98.1
–0.5
87
–86
SINAD (dBc)
86.4
85.2
84
SFDR (dBc)
100.7
102.2
86
48
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