Si4421

8

Typical Application

Typical application with FIFO usage

C3

C2

10n

X1

10MHz

C1

2.2u

Si4421

1

3

4

2

5

7

6

8

9

10

11

12

13

14

15

16

VDD

SCK

SDO

nIRQ

P4

P3

P1

P2

SDI

CLKin

nSEL

nFFS

FFIT

nRES

PCB

Antenna

P5

P6

P7

nRESin

C4

2.2n

P0

CLK

(optional)*

TP

(optional)

(optional)*

(optional)

(opt.)

(optional)

VDI

Note: * Connections needed only in time critical applications

Recommended supply decoupling capacitor values

C2 and C3 should be 0603 size ceramic capacitors to achieve the best supply decoupling.

Band [MHz]

C1

C2

C3

433

2.2µF

10nF

220pF

868

2.2µF

10nF

47pF

915

2.2µF

10nF

33pF

Property

C1

C2

C3

SMD size

A

0603

0603

Dielectric

Tantalum

Ceramic

Ceramic

Pin Function vs. Operation Mode

Mode

Bit setting

Function

Pin 6

Pin 7

Transmit

el = 0

Internal TX data register disabled

TX data input

Not used

el = 1

Internal TX data register enabled

nFFS input

(TX data register can be accessed)

Receive

ef = 0

Receiver FIFO disabled

RX data output

RX data clock

output

ef = 1

Receiver FIFO disabled

nFFS input

(RX data FIFO can be accessed)

FFIT output

The el and ef bits can be found in the Configuration Setting Command on page 16. Bit el enables the internal TX data register.

Bit ef enables the FIFO mode.