8

4702J–RKE–09/08

ATA5756/ATA5757

Figure 4-4.

Timing ASK Mode with ENABLE Connected to the Microcontroller

4.3

Accuracy of Frequency Deviation

The accuracy of the frequency deviation using the XTAL pulling method is about

±20% if the fol-

lowing tolerances are considered. One important aspect is that the values of C

crystals are strongly correlated which reduces the tolerance of the frequency deviation.

Figure 4-5.

Tolerances of Frequency Modulation

Using a crystal with a motional capacitance of C

C

C

internal FSK switch with C

the resulting C

deviation of ±19.3 kHz with worst case tolerances of ±15.8 kHz to ±23.2 kHz.

FSK

CLK

Power-up,

PA off

ASK

ΔT

XTO

Power-down

Power-up,

PA on

(High)

> 250 µs

Power-down

Power-up,

PA off

(Low)

ENABLE

~

V

S

XTAL

C

M

L

M

R

S

C

0

C

Stray

C

4

C

5

Crystal equivalent circuit

C

Switch