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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 ADS1x31REF are shown in
Figure 9 through Figure 12, respectively. Schematics for the ADS1x31REF are shown in Section A.3. The
bill of materials is provided in Table 9.
A.1 Bill of Materials
NOTE: All components should be RoHS compliant. Some part numbers may be either leaded or
RoHS. Verify that purchased components are RoHS compliant.
Table 9. ADS1x31REF Bill of Materials
Item
No ADS1131 ADS1231 Value Ref Des Description Vendor Part Number
1 1 1 BT1 (+) 9 Volt Battery Clip Female Keystone 594
Electronics
2 1 1 BT1 (–) 9 Volt Battery Clip Male Keystone 593
Electronics
3 4 4 22pF C1, C2, C16, 50V Ceramic Chip Capacitor, ±5%, TDK C1608C0G1H220J
C17 C0G
4 4 4 100pF C29, C30, 16V PPS Film Chip Capacitor, 2% Panasonic ECH-U1C101GX5
C31, C32
5 4 4 100pF C40, C41, Filter High Frequency, 100pF Murata NFM21CC101U1H3D
C42, C43
6 5 5 0.01μF C5, C11, 50V Ceramic Chip Capacitor, ±10%, TDK C1608X7R1H103K
C13, C14, X7R
C15
7 6 6 0.1μF C12, C21, 50V Ceramic Chip Capacitor, ±10%, TDK C1608X7R1H104K
C33 to C36 X7R
8 2 2 0.1μF C6, C7 16V PPS Film Chip Capacitor, 2% Panasonic ECH-U1C104GX5
9 3 3 1μF C9, C10, C22 16V Ceramic Chip Capacitor, ±10%, TDK C1608X7R1C105K
X7R
10 5 5 1μF C37, C38, Filter High Frequency, 1.0μF Murata NFM21PC105B1C3D
C39, C44,
C45
11 6 6 2.2μF C23 to C28 6.3V Ceramic Chip Capacitor, ±20%, TDK C1608X5R0J225M
X5R
12 1 1 4.7μF C3 16V Ceramic Chip Capacitor, TDK C2012Y5V1C475Z
+80/–20%, Y5V
13 4 4 10μF C8, C18 to 16V Ceramic Chip Capacitor, ± 20%, TDK C3216X7R1C106M
C20 X7R
14 1 1 100μF C4 10V Tantalum Chip Capacitor, ±10% Kemet T494D107K010AT
15 1 1 D1 30V, 200mA Schottky Diode Fairchild BAT54
Semiconductor
16 1 1 D2 Green LED, SMD Lumex SSL-LX3052GD
17 1 1 J1 USB Type 'B' Socket Mill-Max 897-43-004-90-000000
18 1 1 J2 2.5mm Power Jack CUI PJ-102BH
19 0 0 J3 2 X 7 Header
20 1 1 J6 1 X 6 Header Samtec TSW-106-07-G-S
21 2 2 J7, J8 1 X 2 Header Samtec TSW-102-07-G-S
22 1 1 J4 3.5mm PCB Terminal Block, 4 position On Shore ED555/4DS
Technology
23
SBAU175A–July 2010–Revised August 2011 Schematic and Layout
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