Datasheet
ADS7945
ADS7946
www.ti.com
SBAS539B –JUNE 2011– REVISED SEPTEMBER 2011
ELECTRICAL CHARACTERISTICS: ADS7945 (Differential)
Minimum/maximum specifications at T
A
= –40°C to +125°C, AVDD = 2.7 V to 5.25 V, DVDD = 1.65 V to AVDD, input
common-mode = V
REF
/2 ± 0.2, and f
SAMPLE
= 2 MSPS, unless otherwise noted.
Typical specifications at T
A
= +25°C, AVDD = 5 V, DVDD = 1.8 V, input common-mode = V
REF
/2 ± 0.2, and f
SAMPLE
= 2 MSPS.
PARAMETER TEST CONDITIONS MIN TYP MAX UNITS
ANALOG INPUT
Full-scale input span
(1)
AINxP – AINxN –V
REF
V
REF
V
AIN0P, AIN1P –0.2 AVDD + 0.2 V
Absolute input range
AIN0N, AIN1N –0.2 AVDD + 0.2 V
Input common-mode range
(2)
(AINxP + AINxN)/2 V
REF
/2 ± 0.2 V
Input capacitance
(3)
32 pF
Input leakage current At +125°C 1.5 nA
SYSTEM PERFORMANCE
Resolution 14 Bits
No missing codes 14 Bits
Integral linearity –1.5 ±0.8 1.5 LSB
(4)
Differential linearity –1 ±0.8 1.5 LSB
Offset error
(5)
–4 ±1.5 4 LSB
Gain error –4 ±1.5 4 LSB
Transition noise 25 µV
RMS
Power-supply rejection With 500 Hz sine wave on AVDD 60 dB
SAMPLING DYNAMICS
Conversion time 16 SCLK
Acquisition time 80 ns
Maximum sample rate (throughput rate) 40 MHz SCLK with a 16-clock frame 2 MSPS
Aperture delay
(6)
10 ns
Aperture jitter
(6)
10 ps
Step response
(6)(3)
80 ns
DYNAMIC CHARACTERISTICS
Total harmonic distortion (THD)
(7)
20 kHz, V
REF
= 4.0 V –92 dB
20 kHz, V
REF
= 4.0 V 82 84 dB
Signal-to-noise ratio (SNR)
100 kHz, V
REF
= 4.0 V 83 dB
Signal-to-noise and distorion ratio (SINAD) 20 kHz, V
REF
= 4.0 V 83.5 dB
Spurious-free dynamic range (SFDR) 20 kHz, V
REF
= 4.0 V 94 dB
Full-power bandwidth
(8)
At –3 dB 15 MHz
(1) Ideal input span; does not include gain or offset error.
(2) Refer to the Input Common-Mode Range section in Application Information.
(3) Refer to Figure 76 for sampling circuit details.
(4) LSB means least significant bit.
(5) Measured relative to an ideal full-scale input.
(6) Ensured by simulation.
(7) Calculated on the first nine harmonics of the input frequency.
(8) Indicates signal bandwidth for undersampling applications.
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