MICRF005BM TR Micrel Inc, MICRF005BM TR Datasheet - Page 8

• Manufacturer Part Number: MICRF005BM TR
• Manufacturer: Micrel Inc

Specifications of MICRF005BM TR

• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Operating Supply Voltage (min): 4.75V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Lead Free Status / Rohs Status: Not Compliant

MICRF005
Application Information
Bypass and Output Capacitors
The bypass and output capacitors connected to V
have the shortest possible lead lengths. For best perfor-
mance, connect V
(that is, keep V
return path). V
together at the IC pins. A 10 resistor in series with the supply
line plus three decoupling capacitors is recommended. The
suggested capacitor values are 1nF, 10nF and 100nF.
External Timing Signals
Externally applied signals should be ac-coupled and the
amplitude must be limited to approximately 0.5Vpp.
Optional BandPass Filter
For applications located in high ambient noise environments,
a fixed value band-pass network may be connected between
the ANT pin and V
ity and input overload protection.
Frequency and Capacitor Selection
Selection of the reference oscillator frequency f
capacitor (C
marized in this section.
Selecting Reference Oscillator Frequency f
As with any superheterodyne receiver, the difference be-
tween the internal LO (local oscillator) frequency f
incoming transmit frequency f
center frequency. Equation 1 may be used to compute the
appropriate f
(1)
Frequencies f
f
and “low-side mixing,” and there is generally no preference of
one over the other.
After choosing one of the two acceptable values of f
Equation 2 to compute the reference oscillator frequency f
(2)
Equations (1) and (2) can be simplified to:
Frequency f
frequency f
MICRF005
LO
exist for any given f
f
f
f
T
LO
T
= 63.8258 f
VSS
5V
f
64
LO
T
f
TX
TH
T
LO
to REFOSC on the MICRF005. Four-decimal-
TX
DDRF
is in MHz. Connect a series-mode crystal of
Figure 8. Supply Bypassing
SSBB
10R
), and AGC capacitor (C
R1
for a given f
and f
SSRF
2 496
SSRF
.
TX
and V
currents from flowing through the V
C1
100nF
LO
TX
to provide additional receive selectiv-
915
to V
, distinguished as “high-side mixing”
f
are in MHz. Note that two values of
TX
DDBB
C2
10nF
TX
SSBB
:
TX
should be connected directly
ideally must equal the IF
at the power supply only
C3
1nF
AGC
T
To MICRF005
VDD
) are briefly sum-
T
, slicing level
SSBB
LO
and the
LO
should
, use
SSRF
T
:
8
place accuracy on the frequency is generally adequate. The
following table identifies f
quencies when the MICRF005 is operated.
Selecting Capacitor C
The first step in the process is selection of a data-slicing-level
time constant. This selection is strongly dependent on sys-
tem issues including system decode response time and data
code structure (that is, existence of data preamble, etc.). This
issue is covered in more detail in “Application Note 22.”
Source impedance of the C
where f
(3)
Assuming that a slicing level time constant
established, capacitor C
(4).
(4)
A standard 20% X7R ceramic capacitor is generally suffi-
cient.
Selecting C
Selection of C
AGC control voltage by using a sufficiently large capacitor.
Factory experience suggests that C
vicinity of 0.47 F to 4.7 F. Large capacitor values should be
carefully considered as this determines the time required for
the AGC control voltage to settle from a completely dis-
charged condition. AGC settling time from a completely
discharged (zero-volt) state is given approximately by equa-
tion (5):
(5)
where:
Selecting C
Generally, droop of the AGC control voltage during shutdown
should be replenished as quickly as possible after the IC is
“turned-on”. As described in the functional description, for
about [tbd]ms after the IC is turned on, the AGC push-pull
currents are increased to 45 times their normal values.
Consideration should be given to selecting a value for C
and a shutdown time period such that the droop can be
replenished within this [tbd]ms period.
C
R
Table 2. Common Transmitter Frequencies
T
AGC
t 1.333C
SC
is in MHz:
Frequency (f
AGC
AGC
is in F, and t is in seconds.
3
868.35MHz
916.5MHz
Transmit
0
AGC
915MHz
Capacitor in Continuous Mode
Capacitor in Duty-Cycle Mode
C
14.3359
AGC
is dictated by minimizing the ripple on the
TH
TH
f
T
TX
R
TH
0.44
)
SC
T
may be computed using equation
for some common transmit fre-
TH
Reference Oscillator
pin is given by equation (3),
Frequency (f
13.6050MHz
14.3359MHz
14.3594MHz
AGC
should be in the
T
October 2001
)
has been
Micrel
AGC