A121 Pulsed Coherent Radar (PCR)

Datasheet v1.0

© 2023 Copyright by Acconeer

2023-03-30

Page 18 of 29

6.1 Bill of Materials (BOM)

Table 13 shows BOM for integration of the A121 using a crystal as input clock source:

Component

Value

Description

C1, C2, C3, C4

1 µF

Decoupling for VRX, VTX, VDIG and VIO.

X1

24 MHz

Crystal resonator

C5, C6

See Ch. 6.2

XTAL frequency tuning capacitors

Table 13. BOM list.

6.2 XTAL

The A121 sensor has a built-in crystal oscillator that requires an external crystal component (XTAL)

that is shown in Figure 6.3.

C5

C6

GND

GND

GND

XOUT

XIN

XTAL

I/O

GND

I/O

GND

Figure 6.3. External XTAL schematics.

To enable the internal XTAL oscillator to drive the external resonator, 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 0.3 < 0.7.