MICRF011BM TR Micrel Inc, MICRF011BM TR Datasheet - Page 9

• Manufacturer Part Number: MICRF011BM TR
• Manufacturer: Micrel Inc

Specifications of MICRF011BM TR

• Operating Band Frequency: 300 to 440MHz
• 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

MICRF011
3. Selecting CAGC Capacitor
Selection of CAGC is dictated by minimizing the ripple on
the AGC control voltage, by using a sufficiently large
capacitor. It is Micrel’s experience that CAGC should be in
the vicinity of 0.47 F to 4.7 F.
should be carefully considered, as this determines the time
required for the AGC control voltage to settle from a
completely discharged condition. AGC settling time from a
completely discharged (0-volt) state is given approximately
by equation (6):
where CAGC is in microfarads, and T is in seconds.
I/O Pin Interface Circuitry
Interface circuitry for the various I/O pins of the MICRF011 is
shown in Figures 1 through 6.
regarding each of these circuits is discussed in the following
sub-paragraphs.
which are applied to all input and output pins.
1. ANT Pin
The ANT pin is internally AC-coupled via a 3pF capacitor, to
an RF N-channel MOSFET, as shown in Figure 1.
Impedance on this pin to VSS is quite high at low
frequencies, and decreases as frequency increases. In the
UHF frequency range, the device input can be modeled as
6.3k
VSSRF.
2. CTH Pin
Figure 2 illustrates the CTH pin interface circuit. CTH pin is
driven from a P-channel MOSFET source-follower biased
with approximately 10µA of bias current.
gates TG1 and TG2 isolate the 6.9pF capacitor. Internal
control signals PHI1/PHI2 are related in a manner such that
the impedance across the transmission gates looks like a
“resistance” of approximately 118k . The DC potential on
the CTH pin is approximately 1.6V.
3. CAGC Pin
Figure 3 illustrates the CAGC pin interface circuit. The AGC
control voltage is developed as an integrated current into a
December 1998b
T = (1.333 * CAGC) – 0.44
in parallel with 2pF (pin capacitance) shunt to
Not shown are ESD protection diodes
Figure 1 ANT Pin
Large capacitor values
Specific information
Transmission
(6)
QwikRadio
99
capacitor CAGC.
while the decay current is a 1/10th scaling of this,
approximately 1.5 A. Signal gain of the RF/IF strip inside
the IC diminishes as the voltage on CAGC decreases. By
simply adding a capacitor to CAGC pin, the attack/decay
time constant ratio is fixed at 1:10. Further discussion on
setting the attack time constant is found in “Application Note
22,
Modification of the attack/decay ratio is possible by adding
resistance from CAGC pin either to VDDBB or VSSBB, as
desired.
4. DO Pin
The output stage for the Data Comparator (DO pin) is shown
in Figure 4. The output is a 10µA push-10µA pull, switched
current stage. Such an output stage is capable of driving
CMOS-type
recommended for driving high capacitance loads.
5. REFOSC Pin
The REFOSC input circuit is shown in Figure 5.
impedance is quite high (200k ).
oscillator, with internal 30pF capacitors.
intended to work with standard ceramic resonators,
connected from this pin to VSSBB, although a crystal may
be used instead, where greater frequency accuracy is
required.
capacitors, since these capacitors are contained inside the
IC.
amplitude limited to approximately 0.5Vpp. The nominal DC
bias voltage on this pin is 1.4V.
6. Control Inputs (SEL0, SEL1, SWEN)
Control input circuitry is shown in Figure 6. The standard
input is a logic inverter constructed with minimum geometry
MOSFETs (Q2, Q3). P-channel MOSFET Q1 is a large
channel length device which functions essentially as a
“weak” pullup to VDDBB. Typical pullup current is 5 A,
leading to an impedance to the VDDBB supply of typically
1M .
tm
MICRF001
Externally applied signals should be AC-coupled,
The resonators should not contain integral
loads.
Theory
The attack current is nominally 15 A,
An
of
external
Operation”,
This is a Colpitts
buffer-driver
This input is
section
MICRF011
Micrel
Input
6.5.
is