MICRF219_11 datasheet(17/23 Pages) MICREL

17 / 23 page

Micrel

MICRF219

June 2011

M9999-060811

(408) 944-0800

ey are the

pin has a

enough for

today. The

RF signal

determine

signal-to-noise ratio of the RF link, crude range

capacitor

ve energy.

e de c

ion is

en toggling

ired f

a tim

o show up in the DO pin. This time w

dependent upon many things such as tempe

the crystal used, and if there is an external os

with faster startup time. See Figure 11 and Figu

or time-to-good-data on both 433.92MHz and 31

versions.

Three other pins are worthy of comment. Th

DO, RSSI, and shutdown pins. The DO

driving capability of 0.4mA. This is good

most of the logic family ICs on the market

RSSI pin provides a transfer function of the

intensity versus voltage. It is very useful to

the

estimate from the transmitter source and AM

demodulation, which requires a low CAGC

value.

The shutdown pin (SHDN) is useful to sa

Making its level close to VDD (SHDN = 1), th

not in operation. Its DC current consumpt

than 1µA (do not forget to remove R3). Wh

from high to low, there will be a time requ

device to come to steady-state mode, and

data t

vi e is

less

or the

e for

ill be

rature,

cillator

re 12

5MHz

Figure 12. Time-to-Good-Data a

315MHz at Room Te

Serial Register Programming

Programming the device is accompli

of pins DO and SCLK. Norm

outputting data and needs to

fter Shutdown Cycle,

mperature

shed by the use

ally, D0 (Pin 10) is

switch to an input pin

de by the start sequence, as shown at Figure 13.

High at the SCLK pin tri-states the DO pin, enabling

the external drive into the DO pin with an initial low

level. The start sequence is completed by taking

SCLK low, then high while DO is low, followed by

taking DO high, then low while SCLK is high. The

serial interface is initialized and ready to receive the

programming data.

BIT TIME 1

BIT TIME 0

DO AS

OUTPUT

DO INPUT BITS:

SCLK

D19

“19”

“0”

“1”

D18

D17

BIT TIME 2

Figure 11. Time-to-Good-Data after Shutdown Cycle,

433.92MHz, Room Temperature

Figure 13. Serial Interface Start Sequence

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