LTC1861 View Datasheet(PDF) - Linear Technology
Part Name
Description
MFG CO.
'LTC1861' PDF : 16 Pages View PDF
LTC1860/LTC1861
APPLICATIONS INFORMATION
Reference Input
The reference input of the LTC1861 SO-8 package is
internally tied to VCC. The span of the A/D converter is
therefore equal to VCC. The voltage on the reference input
of the LTC1861 MSOP package defines the span of the A/D
converter. The LTC1861 MSOP package can operate with
reference voltages from 1V to VCC.
GENERAL ANALOG CONSIDERATIONS
Grounding
The LTC1860/LTC1861 should be used with an analog
ground plane and single point grounding techniques. Do not
use wire wrapping techniques to breadboard and evaluate
the device. To achieve the optimum performance, use a
printed circuit board. The ground pins (AGND and DGND
for the LTC1861 MSOP package and GND for the LTC1860
and LTC1861 SO-8 package) should be tied directly to the
analog ground plane with minimum lead length.
Bypassing
For good performance, the VCC and VREF pins must be free
of noise and ripple. Any changes in the VCC/VREF voltage
with respect to ground during the conversion cycle can
induce errors or noise in the output code. Bypass the VCC
and VREF pins directly to the analog ground plane with
a minimum of 1μF tantalum. Keep the bypass capacitor
leads as short as possible.
Analog Inputs
Because of the capacitive redistribution A/D conversion
techniques used, the analog inputs of the LTC1860/LTC1861
have capacitive switching input current spikes. These cur-
rent spikes settle quickly and do not cause a problem if
source resistances are less than 200Ω or high speed op
amps are used (e.g., the LT®1211, LT1469, LT1807, LT1810,
LT1630, LT1226 or LT1215). But if large source resistances
are used, or if slow settling op amps drive the inputs, take
care to ensure the transients caused by the current spikes
settle completely before the conversion begins.
18601fa
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