Texas Instruments ADS1232REF, User Manual, Page: 22 / 30

Hardware
www.ti.com
The terminal block pinout is given in Table 8 .
Table 8. Terminal Block Pinout
TERMINAL NAME FUNCTION
+5VA 5V analog power-supply output
IN1 – Channel 1 negative input
IN1+ Channel 1 positive input
REF+ Positive reference input
IN2 – Channel 2 negative input
IN2+ Channel 2 positive input
REF – Negative reference input
GND Board ground
6.4.4 Voltage Reference
The ADS1232REF is designed to operate either ratiometrically or with an external reference. The two
modes are selected using switch SW7.
In the EXT position, the ADS1232 reference inputs are taken from the load cell connectors. In the +5VA
position, the ADS1232 positive reference input comes from the 5V analog supply, and the negative
reference input is connected to ground.
After the switch is placed a filtering network that consists of resistors R14 and R15, bulk capacitor C4,
pass-through capacitors C44 and C45, and filtering capacitors C28, C30, and C31.
6.4.5 Input Shorting Jumpers
The shorted-input noise test for the ADS1232 is best performed with both inputs connected to 2.5V. To
make this test easy to perform, jumpers J7 and J8 are provided.
Jumper J8 shorts the inputs of channel 1 together. Jumper J7 connects the inverting input to a voltage
divider made from R25 and R26, dividing the power supply by 2. This voltage divider electrically
resembles an ideal bridge sensor.
6.5 USB Interface
The USB interface can be used for firmware download or data communications. Its role in firmware
download is discussed in
Section 6.6 .
The USB interface consists of USB-to-serial converter U4, a Texas Instruments TUSB3410 . This device
incorporates a USB interface module, a microcontroller, and a 16550-type UART. Driver software is
available that causes the device to appear as a serial port on the host PC.
The USB interface is powered separately from the rest of the ADS1232REF; it takes power from the USB
line, through linear regulator U3.
The serial port side of U4 is connected to the microcontroller UART signals. To keep the power domains
separate, and to keep the USB and microcontroller sides from inadvertently powering each other, the
UART is connected through isolators U8 and U9.
6.6 Programming Connections
The MSP430 can be programmed via the dedicated JTAG port or the serial bootstrap loader.
The JTAG connector is not factory-installed. The footprint is similar to an edge-card pattern, and accepts a
standard, dual-row 0.100in header mounted on the side of the board. This header is compatible with
MSP430 parallel-port JTAG adaptors.
22 ADS1232REF User ' s Guide SBAU120B – November 2005 – Revised July 2011
Submit Documentation Feedback
Copyright © 2005 – 2011, Texas Instruments Incorporated