Load Cell Header Pinout - Texas Instruments ADS1230REF User Manual

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6.1 Microcontroller
The ADS1230REF uses the
hardware SPI and UART interfaces, and a multiplier. The latter is important because the firmware must
perform many multiplications.
6.2 Power Supply
The ADS1230REF operates from +5VDC and +3.3VDC. These supplies are generated by linear
regulators U1 and U2. Input power comes from either wall-adapter connector J2, or battery connector
BT1. J2 is switched; when a connector is plugged in, BT1 is disconnected.
Noise is important because the ADS1230 voltage reference is typically taken from the power supply. The
supplies are heavily bypassed to reduce noise.
6.3 User Interface
The ADS1230REF user interface consists of the display and switches SW2–5 and SW8. Switches are
connected to interrupt-capable GPIOs on the microcontroller, allowing them to wake the microcontroller
from sleep mode.
6.4 ADC Section
The ADC section consists of the ADS1230 device itself and ancillary circuitry.
All signals on the ADS1230 are filtered by pass-through capacitors that help to reject electromagnetic
interference (EMI), radio frequency interference (RFI), and noise generated by the digital circuitry.
6.4.1 Input Circuitry
The ADS1230REF is designed to connect to resistive bridge sensors, particularly load cells. The input
channel is filtered by pass-through capacitors C46 and C47 and differential capacitor C7. Common-mode
capacitors C32 and C29 provide additional RF rejection.
6.4.2 Load Cell Header
The load cell header, J6, provides a convenient terminal for load cells having a properly fitted header
connector. It provides excitation and sense connections. The negative excitation line is connected to
ground through analog switch U7, which is controlled by the microcontroller. This arrangement allows for
sleep-and-convert control, which can reduce self-heating in the load cell and conserve power.
The load cell connector's pinout is given in
Section 1.4.4.
PIN NO.
1
2
3
4
5
6
SBAU125A – August 2007 – Revised September 2007
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MSP430F449 microcontroller. This device provides an LCD controller,
Table 7. For connection examples, see
Table 7. Load Cell Header Pinout
PIN NAME
EXC+
EXCSNS+
SIG+
SIG–
EXCSNS–
EXC–
FUNCTION
Positive excitation; connected to +5VA
Positive sense; connected to external positive reference input
Input for positive load cell output
Input for negative load cell output
Negative sense; connected to external negative reference input
Negative excitation; connected to ground through switch U7
ADS1230REF User's Guide
Hardware
Section 1.4.3 and
21