7

ATA5749/ATA5749C [DATASHEET]

9128I–RKE–04/14

4.

Application

4.1

Typical Application

Figure 4-1. Typical Application Circuit

Figure 4-1 shows the typical application circuit. For C6, the supply-voltage blocking capacitor, value of 68nF X7R is

recommended. C2 and C3 are NPO capacitors used to match the loop antenna impedance to the power amplifier optimum

load impedance. They are based on the PCB trace antenna and are ≤ 20pF NPO capacitors. C1 (typically 1nF X7R) is

needed for the supply blocking of the PA. In combination with L1 (200nH to 300nH), they prevent the power amplifier from

coupling to the supply voltage and disturbing PLL operation. They should be placed close to pin 5. L1 also provides a low

CLK_DRV

PFD

ASK_mod

433_N315

FREQ[0:14]

PWR[0:3]

FSK_mod

DIV_CNTRL

SCK

XTO2

XTO1

XTAL

VS

GND

EN

ANT2

ANT1

SDIN_TXDIN

CLK

XTO_RDY

CLK

IO3

IO2

IO1

3

4

C1

VS

VS

C2

C3

C5

C4

C6

L1

5

2

1

8

7

6

9

10

Fractional-N-PLL

CLK_ON

FSEP[0:7]

4 or 8

1

Digital

Control

and

Registers

Frac.

Div.

XTO

(FOX)

Power

up/down

CP

LP

VCO

PA

Loop

antenna

Micro-

controller

Atmel ATA5749

XTO Signal