MICRF219 datasheet(16/23 Pages) MICREL

16 / 23 page

Micrel

MICRF219

June 2011

M9999-060811

(408) 944-0800

Figure 8. Example of a Data Profile

For best results, they should always be optimiz d for

the data pattern u

the baud rate increases,

itor

s de

se.

e 8

s sugg ted

values for Manches

ncoded data, 50% duty cycle.

SEL

JP2

(Hz)

Cagc

sed. As

crea

ter E

the

apac

value

Tabl

show

mod.

Cth

Short

1625

100nF

4.7µF

Open

Short

3250

47nF

2.2µF

Short

Open

6500

22nF

1µF

Open

13000

10nF

0.47µF

Table 8. Suggested CTH and CAGC Val

JP3 and JP4 are jumpers selectable to h

and used to configure the digital squelch

When it is tied to high, there is no squelch ap

the digital circuits and the DO (data out)

hash signal. When the pin is low, the DO pi

considerably reduced. It will have more or

shown in the figure below depending upon

ues

igh or lo

fun tio

n act

les

the o

band noise. The penalty for using squelch is a d

getting a good signal in the DO pin. This means

takes longer for the data to show up. The de

dependent upon many factors such as RF

intensity, data profile, data rate, CTH and

AGC

capacitor values, and outside band noise See Figure

9 and Figure 10. Please note that Squelch action is

based on the Bitcheck operation and may be

optimized using the Bitcheck Window serial register

lied to

has a

ivity is

s than

utside

elay in

that it

lay is

signal

setting.

Figure 9. Data Out Pin with No Squelch (SQ = 1)

Figure 10. Data Out Pin with

Other compo

Squelch (SQ = 0)

nents used are C5, which is a decoupling

capacitor for the VDD line; R3 for the shutdown pin

(SHDN = 0, device is operation), which can be

removed if that pin is connected to a microcontroller or

an external switch; and R1 and R2 which form a

voltage divider for the

pin. One can force a

voltage in this AGC pin to purposely decrease the

device sensitivity. Special care is needed when doing

this operation, as an external control of the AGC

voltage may vary from lot to lot and may not work the

same in several devices.

AGC

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