LTC1865LACMS Datasheet, PDF (15/24 Pages) Linear Technology – Power, 16-Bit, 250ksps 1- and 2-Channel

LTC1864/LTC1865
APPLICATIONS INFORMATION
GENERAL ANALOG CONSIDERATIONS
Grounding
The LTC1864/LTC1865 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 LTC1865 MSOP package and GND for the LTC1864
and LTC1865 SO-8 package) should be tied directly to the
analog ground plane with minimum lead length.
Bypassing
For good performance, the V_CC and V_REF pins must be free
of noise and ripple. Any changes in the V_CC/V_REF voltage
with respect to ground during the conversion cycle can
induce errors or noise in the output code. Bypass the V_CC
and V_REF 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 LTC1864/LTC1865
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.
1111111111111111
1111111111111110
•
•
•
0000000000000001
0000000000000000
*V_IN = (SELECTED “+” CHANNEL) –
(SELECTED “–” CHANNEL)
REFER TO TABLE 1
Figure 5. LTC1865 Transfer Curve
V_IN^*
18645 F05
18645fb
15