XRD87L85 Datasheet, PDF (6/15 Pages) Exar Corporation – Low-Voltage CMOS 8-Bit High-Speed Analog-to-Digital Converter

XRD87L85
Figure 5. Equivalent Input Circuit
Figure 6. Typical Circuit Connections
APPLICATION NOTES
Signals should not exceed V_DD +0.5V or go below GND
–0.5V. All pins have internal protection diodes that will
protect them from short transients (<100µs) outside
the supply range.
AGND and DGND pins are connected internally
through the P-substrate. DC voltage differences be-
tween GND pins will cause undesirable internal sub-
strate currents.
The power supply (V_DD) and reference voltage (V_RT &
V_RB) pins should be decoupled with 0.1µF and 10µF
capacitors to AGND, placed as close to the chip as
possible.
The digital outputs should not drive long wires or buses.
The capacitive coupling and reflections will contribute
noise to the conversion.
To avoid timing errors, use the rising edge of the sample
clock (CLK) to latch data from the XRD87L85 to other
parts of the system.
The reference can be biased internally by shorting V_RT
to V_RTS and V_RB to V_RBS. This will generate 0.4V at V_RB
and 1.72V at V_RT (see Figure 5).
If the internal reference pins V_RTS and/or V_RBS are not
used, they should be left unconnected.
The output enable pin (OE) should not be left uncon-
nected. If not controlled by an active signal, then it must
be tied to a logic low value.
Rev. 1.00
6