MICRF219 datasheet(8/23 Pages) MICREL

8 / 23 page

Micrel

MICRF219

June 2011

M9999-060811

(408) 944-0800

data

cer

ros based on

cap itor.

tal da .

The slicing threshold is default at 50%. The

ing

threshold

n b

serial programming through

Slicer and Slicing Level

The signal, prior to the slicer, is still AM. The

converts the AM signal into ones and ze

sli

the threshold voltage built up in the CTH

After the slicer, the signal is ASK or OOK digi

slic

e set via

D6.

Slicing Level

l 30%

Slice Leve

Slice Level 40%

Slice Level 50%

- default

Slice Level 60%

AGC Comparator

The AGC comparator monitors the signal

from the output of the programmable low

When the output signal is less than 750mV th

1.5µA

amplitude

ass filter.

-p

current is sourced into the external CAGC

tor. When the output signal is greater th

CAGC

he CA

designed to reduce the

nsitivity

of the MICRF219 receiver to a maximum of 45dB for

training the MICRF219 receiver. This is done in order to

recognize an intended transmitter. Very often, a receiver

needs to learn how to recognize a particular transmitter.

It is important for the receiver not to learn the signal of a

stray transmitter near by. The simplest solution is to turn

down the receiver gain, so the receiver only recognizes

the transmitter at close range.

The de-sense function is accessible only through serial

programming.

MODE: Desense

resh-hold,

capaci

750mV, a 15µA current sink discharges

capacitor. The voltage developed on t

capacitor acts to adjust the gain of the mixer

amplifier to compensate for RF input s

variation.

Desense

Desense is a function

nd the IF

nal level

No Desense - default

6dB Desense

16dB Desense

30dB Desense

42dB Desense

Reference Control

ce and Control sub-

and 2) Control Logic

1, SHDN

MICRF219 (Figure 2)

asic Pierce crystal oscillator configuration with

negative resistance.

Though the MICRF219 has build-in load capacitors for

ator, the external load capacitors are still

required for tuning it to the right frequency. R01 and R02

219 to connect the crystal

to the reference oscillator.

ncy can be calculated:

FREF OSC = FRF/(32 + 1.1/12)

For 433.92 MHz, FREF OSC = 13.52127 MHz.

To operate the MICRF219 with minimum offset, crystal

frequencies should be specified with 10pF loading

capacitance.

There are 2 components in Referen

block: 1) Reference Oscillator

through parallel Inputs: SEL0, SEL

Reference Oscillator

The reference oscillator in the

uses a b

MOS transconductor to provide

the crystal oscill

are external pins of the MICRF

Reference oscillator crystal freque

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