MAX187BMJA Maxim Integrated, MAX187BMJA Datasheet - Page 12

• Manufacturer Part Number: MAX187BMJA
• Description: Analog to Digital Converters - ADC
• Manufacturer: Maxim Integrated

Specifications of MAX187BMJA

• Number Of Channels: 1
• Architecture: SAR
• Conversion Rate: 75 KSPs
• Resolution: 12 bit
• Input Type: Single-Ended
• Snr: Yes
• Interface Type: QSPI, Serial (SPI, Microwire)
• Operating Supply Voltage: 4.75 V to 5.25 V
• Maximum Operating Temperature: + 125 C
• Package / Case: CDIP N
• Maximum Power Dissipation: 500 mW
• Minimum Operating Temperature: - 55 C
• Number Of Converters: 1
• Voltage Reference: 4.096 V

Minimum cycle time is accomplished by using DOUT’s
rising edge as the EOC signal. Clock out the data with
13 clock cycles at full speed. Raise CS after the conver-
sion’s LSB has been read. After the specified minimum
time, t
conversion.
The data output from the MAX187/MAX189 is binary, and
Figure 10 depicts the nominal transfer function. Code
transitions occur halfway between successive integer
LSB values. If V
4.096V/4096.
High-speed sampling capability and a 75ksps throughput
make the MAX187/MAX189 ideal for wideband signal pro-
cessing. To support these and other related applications,
Fast Fourier Transform (FFT) test techniques are used
to guarantee the ADC’s dynamic frequency response,
distortion, and noise at the rated throughput. Specifically,
this involves applying a low-distortion sine wave to the
ADC input and recording the digital conversion results for
a specified time. The data is then analyzed using an FFT
algorithm that determines its spectral content. Conversion
errors are then seen as spectral elements outside of the
Figure 10. MAX187/MAX189 UnipolarTransfer Function, 4.096V
= Full Scale
Maxim Integrated
ACQ
11...111
11...110
11...101
00...011
00...010
00...000
00...01
OUTPUT CODE
Output Coding and Transfer Function
, CS can be pulled low again to initiate the next
0
1
REF
INPUT VOLTAGE (LSBs)
2
= +4.096V, then 1 LSB = 1.00mV or
Dynamic Performance
3
FULL-SCALE
TRANSITION
+5V, Low-Power, 12-Bit Serial ADCs
FS - 3/2 LSB
FS = +4.096V
1 LSB = FS
FS
4096
fundamental input frequency. ADCs have traditionally
been evaluated by specifications such as Zero and Full-
Scale Error, Integral Nonlinearity (INL), and Differential
Nonlinearity (DNL). Such parameters are widely accepted
for specifying performance with DC and slowly varying
signals, but are less useful in signal-processing applica-
tions, where the ADC’s impact on the system transfer
function is the main concern. The significance of various
DC errors does not translate well to the dynamic case, so
different tests are required.
Signal-to-noise plus distortion (SINAD) is the ratio of the
fundamental input frequency’s RMS amplitude to the
RMS amplitude of all other ADC output signals. The input
bandwidth is limited to frequencies above DC and below
one-half the ADC sample (conversion) rate.
The theoretical minimum ADC noise is caused by quanti-
zation error and is a direct result of the ADC’s resolution:
SINAD = (6.02N + 1.76)dB, where N is the number of bits
of resolution. An ideal 12-bit ADC can, therefore, do no
better than 74dB. An FFT plot of the output shows the out-
put level in various spectral bands. Figure 11 shows the
result of sampling a pure 10kHz sine wave at a 75ksps
rate with the MAX187/MAX189.
Figure 11. MAX187/MAX189 FFT plot
-100
-120
-140
-20
-40
-60
-80
20
0
0
MAX187/MAX189
Signal-to-Noise Ratio and
Effective Number of Bits
FREQUENCY (kHz)
18.75
f
f
T
S
T
A
= 75ksps
= 10kHz
= +25°C
37.5
12