Datasheet

Input Range
±10V
±5V
Without Trim
With Trim
(Adjust Gain)
R1
IN
AGND1
R2
IN
R3
IN
CAP
REF
AGND2
R1
IN
AGND1
R2
IN
R3
IN
CAP
REF
AGND2
V
IN
2.2µF
2.2µF
2.2µF
+5V
50kΩ
576kΩ
2.2µF
V
IN
V
IN
R1
IN
AGND1
R2
IN
R3
IN
CAP
REF
AGND2
R1
IN
AGND1
R2
IN
R3
IN
CAP
REF
AGND2
+5V
2.2µF
2.2µF
576kΩ
50kΩ
V
IN
2.2µF
2.2µF
ADS8519
www.ti.com SLAS462D –JUNE 2007–REVISED SEPTEMBER 2010
Figure 30. Offset/Gain Circuits for Bipolar Input Ranges
Analog input pins R1
IN
, R2
IN
, and R3
IN
have ±25V overvoltage protection. The input signal must be referenced to
AGND1. This referencing minimizes the ground-loop problem typical to analog designs. The analog input should
be driven by a low-impedance source. A typical driving circuit using the OPA627 or OPA132 is shown in
Figure 30.
The ADS8519 can operate with its internal 4.096V reference or an external reference. An external reference
connected to pin 7 (REF) bypasses the internal reference. The external reference must drive the 4kΩ resistor
that separates pin 6 from the internal reference (see the illustration on page 1). The load varies with the
difference between the internal and external reference voltages. The external reference voltage can vary from
3.9V to 4.2V. The internal reference is approximately 4.096V. The reference, whether internal or external, is
buffered internally with the output on pin 6 (CAP).
The ADS8519 is factory-tested with 2.2mF capacitors connected to pin 6 (CAP) and pin 7 (REF). Each capacitor
should be placed as close as possible to its pin. The capacitor on pin 7 band-limits the internal reference noise.
A smaller capacitor can be used, but it may degrade SNR and SINAD The capacitor on pin 6 stabilizes the
reference buffer and provides switching charge to the CDAC during conversion. Capacitors smaller than 1mF
may cause the buffer to become unstable and not hold sufficient charge for the CDAC. The parts are tested to
specifications with 2.2mF, so larger capacitors are not necessary. The equivalent series resistance (ESR) of
these compensation capacitors is also critical. Keep the total ESR under 3Ω. See the Typical Characteristics
section concerning how ESR affects performance.
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