A111 Pulsed Coherent Radar (PCR)

Datasheet, v2.8

Page 23 of 35

2022-06-22

© 2022 Copyright by Acconeer

Bill of Material (BoM)

The below table shows BOM for integration of the A111 using a crystal as input clock source:

Component

Value

Description

C1, C2, C3

1 µF

VIO_1, VIO_2, VIO_3 decoupling

R1, R2

100 kΩ

INTERRUPT and CTRL pull down resistor

X1

XTAL 24 MHz, Epson TSX-3225

C4, C5

8 pF (1)

XTAL freq. tuning capacitor

Table 9.1. BOM list.

(1) See details in chapter 9.1 XTAL for C4, C5 value calculation.

9.1 XTAL

The input clock origin from a crystal (XTAL), connected to XIN and XOUT.

The A111 sensor has a built-in XTAL oscillator and adding an external XTAL component, as shown

in the Figure 9.2.

C4

C5

GND

GND

GND

XOU T

XIN

TSX-3225

XTAL 24MHz

I/O

GND

I/O

GND

Figure 9.2. External XTAL schematics.

To enable the internal XTAL oscillator to drive the external resonator, the relation in Equation 1 must

be fulfilled.

������ ∗ ������������������������

0.8 ∗ ������

������������������

0.61 < 0.7

(Equation 1)

������ = 2(������������ − ������������������������������������)

(Equation 2)

������������������������ = ������ + ������������������������������������ ∗ 2

(Equation 3)

The capacitance values are calculated in Equation 2. CL and RESR are XTAL parameters and vary from

XTAL to XTAL. The stray capacitance is the sum of the capacitance between XIN and XOUT, that is,

the PCB trace capacitance plus package capacitance; 2 to 5 pF is a general estimation.

Example:

• f = 24 MHz

• C

L = 9 pF

• R

ESR = 40 ohm

Assuming Cstray = 5 pF gives C4, C5 = 8 pF and that the condition is met with the result 0.58 < 0.7.