Texas Instruments ADS1232REF, User Manual, Page: 23 / 30

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Appendix A
To allow firmware to be downloaded through USB, U4 is connected to the microcontroller bootstrap loader
pins. The DTR and RTS pins are connected to the RST and TCK inputs on the microcontroller to allow the
serial bootstrap loader to operate. These lines are not isolated; instead, they are switched through SW9,
which also connects USB ground and power to the microcontroller ground and power. Normally this switch
is open; it is only switched on when firmware is to be downloaded through USB. This feature also protects
the microcontroller from unknown states on these pins at power-up.
Appendix A Schematic and Layout
The printed circuit board (PCB) layouts for the top and bottom sides of the ADS1232REF are shown in
Figure 9 and Figure 10 , respectively. The schematic for the ADS1232REF is shown in Section A.3 . The
bill of materials is provided in Table 9 .
A.1 Bill of Materials
Table 9. ADS1232REF Bill of Materials
REFERENCE DESIGNATOR DESCRIPTION MANUFACTURER MFG. PART NUMBER
R23, R24 0 1/16W 1% Chip Resistor Panasonic ERJ-3GEY0R00V
R17 20 1/4W 5% Chip Resistor Panasonic ERJ-8GEYJ200V
R2, R3 33 1/10W 5% Chip Resistor Panasonic ERJ-3GEYJ330V
R12 – R15 100 1/10W 5% Chip Resistor Panasonic ERJ-3GEYJ101V
R11 220 1/10W 5% Chip Resistor Panasonic ERJ-3GEYJ221V
R1 1.5K 1/10W 5% Chip Resistor Panasonic ERJ-3GEYJ152V
R4 – R10, R16 10K 1/10W 5% Chip Resistor Panasonic ERJ-3GEYJ103V
R25, R26 20K 1/16W 1% Chip Resistor Panasonic ERJ-3EKF2002V
R18, R27 47K 1/10W 5% Chip Resistor Panasonic ERJ-3GEYJ473V
R22 200k Potentiometer 200k Ω , 1/4in Bourns 3362U-1-204LF
SQ
R19-R21 221k 1/16W 1% Chip Resistor Panasonic ERJ-3EKF2213V
C1, C2, C16, C17 22pF 50V Ceramic Chip TDK C1608C0G1H220J
Capacitor, ± 0.5pF, NPO
C29, C30, C31, C32 100pF 16V PPS Film Chip Panasonic ECH-U1C101GX5
Capacitor, 2%
C38 – C43, C48, C49 100pF Filter High Frequency, Murata NFM21CC101U1H3D
100pF
C5, C11, C13 – C15 0.01 μ F 50V Ceramic Chip TDK C1608X7R1H103K
Capacitor, ± 10%, X7R
C12, C21, C33 – C36 0.1 μ F 50V Ceramic Chip TDK C1608X7R1H104K
Capacitor, ± 10%, X7R
C6, C7 0.1 μ F 16V PPS Film Chip Panasonic ECH-U1C104GX5
Capacitor, 2%
C9, C10, C22 1
μ
F 16V Ceramic Chip TDK C1608X7R1C105K
Capacitor, ± 10%, X7R
C37, C44 – C47 1 μ F Filter High-Frequency, 1.0 μ F Murata NFM21PC105B1C3D
C23 – C28 2.2 μ F 6.3V Ceramic Chip TDK C1608X5R0J225M
Capacitor, ± 20%, X5R
C3 4.7 μ F 16V Ceramic Chip TDK C2012Y5V1C475Z
Capacitor, +80/-20%, Y5V
C8, C18 – C20 10 μ F 16V Ceramic Chip TDK C3216X7R1C106M
Capacitor, ± 20%, X7R
C4 100
μ
F 10V Tantalum Chip Kemet T494D107K010AT
Capacitor, ± 10%
U6 Analog-to-Digital Converter Texas Instruments ADS1232IPW
U5 Microcontroller Texas Instruments MSP430F449IPZ
U2, U3 Linear Voltage Regulator, +3.3V Texas Instruments TPS77133DGKG4
23 SBAU120B – November 2005 – Revised July 2011 Schematic and Layout
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