MAX199BC/D Maxim Integrated, MAX199BC/D Datasheet - Page 13

• Manufacturer Part Number: MAX199BC/D
• Description: Analog to Digital Converters - ADC
• Manufacturer: Maxim Integrated

Specifications of MAX199BC/D

• Number Of Channels: 8
• Architecture: SAR
• Conversion Rate: 100 KSPs
• Resolution: 12 bit
• Input Type: Single-Ended
• Interface Type: Parallel
• Operating Supply Voltage: 4.75 V to 5.25 V
• Maximum Power Dissipation: 762 mW
• Number Of Converters: 1
• Voltage Reference: 4.096 V

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 MAX199 can operate with either an internal or external
reference. An external reference can be connected 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
+5V Supply, 12-Bit DAS with 8+4 Bus Interface
MAX199
Internal or External Reference
______________________________________________________________________________________
2.5V
DD
10k
A
V
. Using the REFADJ input elimi-
= 1.638
REFADJ
Power-On Reset
External Reference
REF
Multi-Range (±4V, ±2V, +4V, +2V),
Internal Reference
26 4.096V
25
4.7 F
C
0.01 F
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 at REF
Figure 9c. The external reference at REFADJ overdrives the
internal reference.
MAX199
MAX199
2.5V
2.5V
10k
10k
A
A
V
V
= 1.638
= 1.638
REFADJ
REFADJ
REF
REF
26
25
26 4.096V
25
4.7 F
C
REF
V
4.7 F
C
0.01 F
DD
REF
4.096V
2.5V
13