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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

0.01

μF

C5, C11,

50V Ceramic Chip Capacitor,

±10%,

TDK

C1608X7R1H103K

C13, C14,

X7R

C15

7

6

6

0.1

μF

C12, C21,

50V Ceramic Chip Capacitor,

±10%,

TDK

C1608X7R1H104K

C33 to C36

X7R

8

2

2

0.1

μF

C6, C7

16V PPS Film Chip Capacitor, 2%

Panasonic

ECH-U1C104GX5

9

3

3

1

μF

C9, C10, C22

16V Ceramic Chip Capacitor,

±10%,

TDK

C1608X7R1C105K

X7R

10

5

5

1

μF

C37, C38,

Filter High Frequency, 1.0

μF

Murata

NFM21PC105B1C3D

C39, C44,

C45

11

6

6

2.2

μF

C23 to C28

6.3V Ceramic Chip Capacitor,

±20%,

TDK

C1608X5R0J225M

X5R

12

1

1

4.7

μF

C3

16V Ceramic Chip Capacitor,

TDK

C2012Y5V1C475Z

+80/

–20%, Y5V

13

4

4

10

μF

C8, C18 to

16V Ceramic Chip Capacitor,

± 20%,

TDK

C3216X7R1C106M

C20

X7R

14

1

1

100

μF

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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