MAX197BEWI+T Maxim Integrated Products, MAX197BEWI+T Datasheet - Page 13

• Manufacturer Part Number: MAX197BEWI+T
• Description: IC DAS 12BIT SNGL 28-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Data Acquisition System (DAS)r

Specifications of MAX197BEWI+T

• Resolution (bits): 12 b
• Sampling Rate (per Second): 100k
• Data Interface: Parallel
• Voltage Supply Source: Single Supply
• Voltage - Supply: 4.75 V ~ 5.25 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

At power-up, the internal power-supply circuitry sets INT
high and puts the device in normal operation/external
clock mode. This state is selected to keep the internal
clock from loading the external clock driver when the
part is used in external clock mode.
The MAX197 can operate with either an internal or an
external reference. An external reference can be connect-
ed to either the REF pin or to the REFADJ pin (Figure 9).
To use the REF input directly, disable the internal buffer
by tying REFADJ to V
nates the need to buffer the reference externally.
When the reference is applied at REFADJ, bypass
REFADJ with a 0.01µF capacitor to AGND.
The REFADJ internal buffer gain is trimmed to 1.6384 to
provide 4.096V at the REF pin from a 2.5V reference.
The internally trimmed 2.50V reference is gained
through the REFADJ buffer to provide 4.096V at REF.
Bypass the REF pin with a 4.7µF capacitor to AGND
and the REFADJ pin with a 0.01µF capacitor to AGND.
The internal reference voltage is adjustable to ±1.5%
(±65 LSBs) with the reference-adjust circuit of Figure 1.
At REF and REFADJ, the input impedance is a mini-
mum of 10kΩ for DC currents. During conversions, an
Figure 9a. Internal Reference
__________Applications Information
Single +5V, 12-Bit DAS with 8+4 Bus Interface
MAX197
Internal or External Reference
______________________________________________________________________________________
2.5V
10kΩ
DD
A
V
. Using the REFADJ input elimi-
= 1.638
Multi-Range (±10V, ±5V, +10V, +5V),
REFADJ
Power-On Reset
External Reference
REF
Internal Reference
26
25
C
4.7µF
0.01µF
REF
external reference at REF must be able to deliver
400µA DC load currents, and must have an output
impedance of 10Ω or less. If the reference has higher
input impedance or is noisy, bypass it close to the REF
pin with a 4.7µF capacitor to AGND.
With an external reference voltage of less than 4.096V
at the REF pin or less than 2.5V at the REFADJ pin, the
increase in the ratio of the RMS noise to the LSB value
(FS / 4096) results in performance degradation (loss of
effective bits).
Figure 9b. External Reference, Reference at REF
Figure 9c. External Reference, Reference at REFADJ
MAX197
MAX197
2.5V
2.5V
10kΩ
10kΩ
A
A
V
V
= 1.638
= 1.638
REFADJ
REFADJ
REF
REF
26
25
26
25
C
4.7µF
REF
V
C
4.7µF
0.01µF
DD
REF
4.096V
2.5V
13