www.ti.com
2
Analog Interface
2.1
Analog Input Range Selection
2.2
Optional Amplifier Input
Analog Interface
For maximum flexibility, the ADS78/8509 EVM is designed for easy interfacing to multiple analog sources.
Samtec part numbers SSW-110-22-F-D-VS-K and TSM-110-01-T-DV-P provide a convenient ten-pin dual
row header/socket combination at J1. This header/socket provides access to the analog input pins of the
ADC. Please consult Samtec at www.samtec.com or call 1-800-SAMTEC-9 for a variety of mating
connector options.
shows the pin out of the analog input connector, J1.
Table 1. Pinout of the Analog Input Connector, J1
Pin Number
Signal
Description
J1.2 thru
Analog
To accommodate EVM Stacking using the TAG feature of the data converter, jumper W12 can be used
J1.16 (even)
Input
in combination with J1 to choose one of eight analog input channels to the evaluation module.
J1.20
REF(+)J
External reference source input, accessible through W6.
J1.15
REFOUT
Optional connection via W6. Provides external AFE circuitry with REFOUT bias voltage.
J1.1- J1.19
AGND
Analog ground connections. Note J1.15 is used for REFOUT connections to external AFE circuitry.
(odd)
The analog front-end (AFE) circuitry found on the EVM consists of a simple RC filter. When used in
combination with the 5-6K Interface Board, the circuits found on both DAP Signal Conditioning Boards
(see
) provide the level shifting and amplifier configurations to realize single ended or bi-polar
mode operation of the analog-to-digital converter installed on the EVM.
Jumpers W1 through W5 provide a convenient way to choose the analog input range. W1 controls the
input connection to pin 1 (R1IN), W2 controls the connection to pin 3 (R2IN) and W3 controls the inputs on
pins 4 and 5 (R3IN and CAP). Jumpers W4 and W5 provide connections to 33.2K resistors wired to the
CAP pin and TRIM adjustment pot R6 (via W5).
is representative of the input range selection.
Table 2. Input Range Selection
(1)
Range
Without Trim
With Trim
W1
W2
W3
W4
W5
W1
W2
W3
W4
W5
0–10 V
5–6
1–2
5–6
1–2
2–3
5–6
1–2
5–6
1–2
1–2
0–5 V
5–6
5–6
1–2
1–2
2–3
5–6
5–6
1–2
1–2
1–2
0–4 V
1–2
5–6
1–2
2–3
2–3
1–2
5–6
1–2
2–3
1–2
±
10 V
5–6
5–6
3–4
2–3
2–3
5–6
5–6
3–4
2–3
1–2
±
5 V
1–2
1–2
3–4
1–2
2–3
1–2
1–2
3–4
1–2
1–2
±
5 V
1–2
1–2
3–4
2–3
2–3
1–2
1–2
3–4
2–3
1–2
(1)
For Offset Adjustment, close W6 pins 5–6 and adjust R8 before trimming.
Jumper W7 provides access to an optional amplifier/buffer circuit on the front end of the data converter.
Component U2 can be installed at the user's option with any standard 8 pin SOIC single amplifier
component. The amplifier circuit is connected to the
±
VA terminals for split supply operation. If single
supply amplifiers are used, the –VA (J3 pin 2) can be tied to analog ground (J3 pin 6). The footprint for
common 4mm trim pots (see component R11) is provided as an offset adjustment pot for single supply
amplifiers. When used in conjunction with the 5-6K Interface Board, please be aware that the –VA supply
is common to all power connectors (JP1 through JP6). Shorting the –VA supply to ground on the
ADS78/8509 EVM is possible only if it is not used elsewhere on the interface board.
ADS78/8509 EVM User's Guide
2
SLAU140 – November 2004