AS3685A/AS3685B

Datasheet

www.austriamicrosystems.com/

AS3685

(ptr)

Revision 2.2

17 - 24

8

External Components

8.1 Capacitor and Resistor Selection

Use low-ESR ceramic capacitors with X7R or X5R dielectric. These capacitors allow good filtering and have a

wide temperature range. The connections of all external capacitors should be kept as short as possible. All

resistors should have a tolerance of ±1%.

8.2 Usage of PCB Wire Inductance

of

It is recommended to apply a minimum of 20nH (maximum 200nH) with low impedance. This inductance can be

realized on the PCB without any discrete coil. Assuming that a 1mm signal line corresponds to approximately

1nH (valid if the length (L) is significantly bigger than the width (W) of the line (L/W <10)), a line length of

20mm < L < 200mm

is recommended. The shape of the line is not important.

Figure 25 – PCB Wire Inductance Example1

Figure 26 – PCB Wire Inductance Example2

8.3 External Component Specifications

Table

10 – External Components List

Part

Min

Value

Typ

Max

Tol

(Min)

Rating

(Max)

Notes

Package

(min)

1

2.2

μF

+/-20%

6.3V

Ceramic, X5R

e.g. Murata GRM21BR71A225KA01L

0603

1.0

μF

+/-20%

6.3V

Ceramic, X5R

e.g. Murata GRM188R60J105K

0603

(0402, 0405)

2.2

μF

+/-20%

6.3V

Ceramic, X5R

e.g. Murata GRM21BR71A225KA01L

0603

10k

Ω

130k

Ω

+/-1%

Current Set Resistor

0201

See section ‘TXMask function’

+/-1%

TXMask Set Resistor

0201

Flash Led

Notes:

1. See section ‘Usage of PCB Wire Inductance’

Battery

Connector

VSS

VSS

AS3685

Pin VBAT

L

Battery

Connector

VSS

VSS

AS3685

Pin VBAT

L1