ADC0808S125_ADC0808S250_3 © NXP B.V. 2009. All rights reserved.
Product data sheet Rev. 03 — 24 February 2009 13 of 23
NXP Semiconductors
ADC0808S125/250
Single 8-bit ADC, up to 125 MHz or 250 MHz
[1] Output data acquisition: the output data is available after the maximum delay of t
d(o)
.
[2] The −3 dB analog bandwidth is determined by the 3 dB reduction in the reconstructed output, the input being a full-scale sine wave.
[3] The total harmonic distortion is obtained with the addition of the first five harmonics.
[4] The signal-to-noise ratio takes into account all harmonics above five and noise up to Nyquist frequency.
[5] Intermodulation measured relative to either tone with analog input frequencies f
1
and f
2
. The two input signals have the same amplitude
and the total amplitude of both signals provides full-scale to the converter (−6 dB below full-scale for each input signal). IMD3 is the ratio
of the RMS value of either input tone to the RMS value of the worst case third-order intermodulation product.
12. Definitions
12.1 Static parameters
12.1.1 Integral non-linearity
Integral non-linearity (INL) is defined as the deviation of the transfer function from a
best-fit straight line (linear regression computation). The INL of the code is obtained from
the equation:
(1)
where: S corresponds to the slope of the ideal straight line (code width), i corresponds to
the code value, V
in
is the input voltage.
12.1.2 Differential non-linearity
Differential non-linearity (DNL) is the deviation in code width from the value of 1 LSB.
(2)
where: V
in
is the input voltage; i is a code value from 0 to (2
n
− 2).
12.2 Dynamic parameters
Figure 10 shows the spectrum of a single tone full-scale input sine wave of frequency f
t
,
conforming to coherent sampling and which is digitized by the ADC under test. Coherent
sampling: (f
t
/ f
s
= M / N, where M = number of cycles and N = number of samples,
M and N values being relatively prime).
SFDR spurious free dynamic range f
clk
= 125 MHz; f
i
= 78 MHz - 55 - dBc
f
clk
= 250 MHz; f
i
= 125 MHz - 55 - dBc
IMD2 second-order intermodulation
distortion
f
1
= 124 MHz; f
2
= 126 MHz;
f
clk
= 250 MHz
[5]
- −55 - dB
IMD3 third-order intermodulation
distortion
f
1
= 124 MHz; f
2
= 126 MHz;
f
clk
= 250 MHz
[5]
- −60 - dB
Table 13. Dynamic characteristics
…continued
V
CCA
= 3.0 V to 3.6 V; V
CCD
= 1.65 V to 1.95 V; V
CCO
= 1.65 V to 1.95 V; pins AGND1, AGND2 and DGND1 shorted together;
T
amb
=
−
40
°
C to +85
°
C; V
i(IN)
−
V
i(INN)
= 2.0 V
−
0.5 dB; V
I(cm)
= 0.95 V; V
FSIN
= 0 V; typical values are measured at
V
CCA
= 3.3 V, V
CCD
=V
CCO
= 1.8 V, T
amb
=25
°
C and C
L
= 10 pF; unless otherwise specified.
Symbol Parameter Conditions Min Typ Max Unit
INL i()
V
in
i() V
in
ideal()–
S
-----------------------------------------------
=
DNL i()
V
in
i1+()V
in
i()–
S
---------------------------------------------
=
