MAX1195ECM+TD Maxim Integrated Products, MAX1195ECM+TD Datasheet - Page 16

• Manufacturer Part Number: MAX1195ECM+TD
• Description: IC ADC 8BIT 40MSPS DL 48-TQFP
• Manufacturer: Maxim Integrated Products

Specifications of MAX1195ECM+TD

• Number Of Bits: 8
• Sampling Rate (per Second): 40M
• Data Interface: Parallel
• Number Of Converters: 2
• Power Dissipation (max): 108mW
• Voltage Supply Source: Single Supply
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 48-TQFP Exposed Pad, 48-eTQFP, 48-HTQFP, 48-VQFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Figure 6. Transformer-Coupled Input Drive
Dual, 8-Bit, 40Msps, 3V, Low-Power ADC with
Internal Reference and Parallel Outputs
An RF transformer (Figure 6) provides an excellent
solution to convert a single-ended source signal to a
fully differential signal, required by the MAX1195 for
optimum performance. Connecting the center tap of the
transformer to COM provides a V
the input. Although a 1:1 transformer is shown, a step-
up transformer can be selected to reduce the drive
requirements. A reduced signal swing from the input
driver, such as an op amp, can also improve the overall
distortion.
In general, the MAX1195 provides better SFDR and
THD with fully differential input signals than single-
ended drive, especially for very high input frequencies.
In differential input mode, even-order harmonics are
lower as both inputs (INA+, INA- and/or INB+, INB-) are
balanced, and each of the ADC inputs only requires
half the signal swing compared to single-ended mode.
16
V
V
IN
IN
______________________________________________________________________________________
0.1µF
0.1µF
N.C.
N.C.
MINICIRCUITS
MINICIRCUITS
3
3
1
2
TT1–6-KK81
1
2
TT1–6-KK81
T1
T1
6
5
4
6
5
4
Using Transformer Coupling
2.2µF
2.2µF
25Ω
25Ω
25Ω
25Ω
0.1µF
0.1µF
22pF
22pF
22pF
22pF
DD
/2 DC level shift to
INA+
INA-
INB+
INB-
COM
MAX1195
Figure 7. Using an Op Amp for Single-Ended, AC-Coupled
Input Drive
Figure 7 shows an AC-coupled, single-ended applica-
tion. Amplifiers like the MAX4108 provide high speed,
high bandwidth, low noise, and low distortion to main-
tain the integrity of the input signal.
Multiple-converter systems based on the MAX1195 are
well suited for use with a common reference voltage.
The REFIN pin of those converters can be connected
directly to an external reference source.
A precision bandgap reference like the MAX6062 gen-
erates an external DC level of 2.048V (Figure 8), and
exhibits a noise voltage density of 150nV/√Hz. Its out-
put passes through a 1-pole lowpass filter (with 10Hz
cutoff frequency) to the MAX4250, which buffers the
reference before its output is applied to a second 10Hz
lowpass filter. The MAX4250 provides a low offset volt-
age (for high gain accuracy) and a low noise level. The
V
V
IN
IN
MAX4108
MAX4108
Single-Ended AC-Coupled Input Signal
Buffered External Reference Drives
100Ω
100Ω
100Ω
100Ω
0.1µF
0.1µF
REFN
REFN
REFP
REFP
1kΩ
1kΩ
1kΩ
1kΩ
0.1µF
0.1µF
R
50Ω
R
50Ω
ISO
ISO
22pF
22pF
50Ω
50Ω
R
R
C
C
C
22pF
C
22pF
ISO
ISO
IN
IN
IN
IN
Multiple ADCs
INA+
COM
INA-
INB+
INB-
MAX1195