MAX187CEPA Maxim Integrated, MAX187CEPA Datasheet - Page 9

• Manufacturer Part Number: MAX187CEPA
• Description: Analog to Digital Converters - ADC
• Manufacturer: Maxim Integrated

Specifications of MAX187CEPA

• 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: + 85 C
• Package / Case: PDIP N
• Maximum Power Dissipation: 500 mW
• Minimum Operating Temperature: - 40 C
• Number Of Converters: 1
• Voltage Reference: 4.096 V

Internal protection diodes that clamp the analog input
allow the input to swing from GND - 0.3V to V
without damage. However, for accurate conversions near
full scale, the input must not exceed V
50mV, or be lower than GND by 50mV.
If the analog input exceeds the supplies by more than
50mV beyond the supplies, limit the input current
to 2mA, since larger currents degrade conversion
accuracy.
The input lines to AIN and GND should be kept as short
as possible to minimize noise pickup. Shield longer
leads. Also see the Input Protection section.
Because the MAX187/MAX189 incorporate a T/H, the
drive requirements of the op amp driving AIN are less
stringent than those for a successive-approximation ADC
without a T/H. The typical input capacitance is 16pF. The
amplifier bandwidth should be sufficient to handle the
frequency of the input signal. The MAX400 and OP07
work well at lower frequencies. For higher-frequency
operation, the MAX427 and OP27 are practical choices.
The allowed input frequency range is limited by the
75ksps sample rate of the MAX187/MAX189. Therefore,
the maximum sinusoidal input frequency allowed is
37.5kHz. Higher-frequency signals cause aliasing prob-
lems unless undersampling techniques are used.
Figure 5. MAX187/MAX189 Shutdown Sequence
Maxim Integrated
SHDN
DOUT
CS
Driving the Analog Input
POWERED UP
+5V, Low-Power, 12-Bit Serial ADCs
CONVERSION 1
DD
Input Protection
by more than
COMPLETE CONVERSION SEQUENCE
DD
+ 0.3V
POWERED DOWN
The MAX187 can be used with an internal or external ref-
erence, while the MAX189 requires an external reference.
The MAX187 has an on-chip reference with a buff-
ered temperature-compensated bandgap diode, laser-
trimmed to +4.096V Q0.5%. Its output is connected to
REF and also drives the internal DAC. The output can be
used as a reference voltage source for other components
and can source up to 0.6mA. Decouple REF with a 4.7FF
capacitor. The internal reference is enabled by pulling
the SHDN pin high. Letting SHDN float disables the inter-
nal reference, which allows the use of an external refer-
ence, as described in the External Reference section.
The MAX189 operates with an external reference at the
REF pin. To use the MAX187 with an external reference,
disable the internal reference by letting SHDN float. Stay
within the voltage range +2.5V to V
fied accuracy. The minimum input impedance is 12kI for
DC currents. During conversion, the external reference
must be able to deliver up to 350FA DC load current and
have an output impedance of 10I or less. The recom-
mended minimum value for the bypass capacitor is 0.1FF.
If the reference has higher output impedance or is noisy,
bypass it close to the REF pin with a 4.7FF capacitor.
t
WAKE
POWERED UP
MAX187/MAX189
CONVERSION 1
DD
External Reference
Internal Reference
to achieve speci-
Reference
9