MICRF007BM Micrel Inc, MICRF007BM Datasheet - Page 7

• Manufacturer Part Number: MICRF007BM
• Description: IC RECEIVER UHF LOW POWER 8SOIC
• Manufacturer: Micrel Inc

Specifications of MICRF007BM

• Frequency: 300MHz ~ 440MHz
• Sensitivity: -96dBm
• Data Rate - Maximum: 2.1 kbps
• Modulation Or Protocol: ASK, OOK
• Applications: RKE
• Current - Receiving: 3mA
• Data Interface: PCB, Surface Mount
• Antenna Connector: PCB, Surface Mount
• Features: Automatic Tuning
• Voltage - Supply: 4.75 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Package / Case: 8-SOIC (0.154", 3.90mm Width)
• Receiving Current: 5.7mA
• Data Rate: 3.2Kbps
• Modulation Type: ASK, OOK
• Frequency Range: 300MHz To 440MHz
• Sensitivity Dbm: -99dBm
• Rf Ic Case Style: SOIC
• No. Of Pins: 8
• Operating Band Frequency: 300 to 440MHz
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 3.94mm
• Product Height (mm): 1.48mm
• Operating Supply Voltage (min): 4.75V
• Operating Supply Voltage (typ): 5V
• Operating Supply Voltage (max): 5.5V
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Memory Size: -
• Lead Free Status / Rohs Status: Not Compliant

appropriate f
Frequencies f
of f
mixing” and “low-side mixing.” High-side mixing results in an
image frequency above the frequency of interest and low-
side mixing results in a frequency below. 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
Frequency f
REFOSC on the MICRF007. Four-decimal-place accuracy
on the frequency is generally adequate. The following table
identifies f
Step 2: Selecting C
Extraction of the DC value of the demodulated signal for
purposes of logic-level data slicing is accomplished using the
external threshold capacitor C
capacitor “resistor” RSC, shown in the block diagram.
Slicing level time constant values vary somewhat with de-
coder type, data pattern, and data rate, but typically values
range from 5ms to 50ms.This issue is covered in more detail
in “Application Note 22.” Optimization of the value of C
required to maximize range.
τ of 5x the bit-rate is recommended. The effective resistance
of RSC is listed in the electrical characteristics table as 110kΩ
at 433.92MHz, This value scales inversely with frequency.
Source impedance of the C
given by equation (3), where f
Since slicing level time constant τ has been established
as 5 times bit rate, capacitor C
equation (4),
A standard ±20% X7R ceramic capacitor is generally suffi-
cient. Refer to “Application Hint 42” for C
tion examples.
February 17, 2005
MICRF007
T
:
Table 2. Recommended Reference Oscillator Values
for Typical Transmit Frequencies (high-side mixing)
LO
Frequency f
RSC = 110kΩ
C
f
f
exist for any given f
LO
T
433.92MHz
TH
=
Transmit
T
315MHz
390MHz
418MHz
= f
=
64.5
T
for some common transmit frequencies.
f
LO
R
LO
TX
is in MHz. Connect a crystal of frequency f
TX
SC

±
for a given f
�
�
�
and f
1.18
TX
TH
6.7458
LO
433.92
Capacitor
f
f
T
TX
are in MHz. Note that two values
TX
TX
TH
T
:
�
�
�
, distinguished as “high-side
TH
Oscillator Frequency f
is in MHz:
TH
pin at other frequencies is
and the on-chip switched
may be computed using
4.8970MHz
6.0630MHz
6.4983MHz
6.7458MHz
Reference
TH
and C
AGC
(1)
(2)
(3)
(4)
LO
selec-
, use
TH
T
T
to
is
7
Step 3: Selecting C
The signal path has automatic gain control (AGC) to increase
input dynamic range. The attack time constant of the AGC is
set externally by the value of the C
to the C
it is important to keep the AGC control voltage ripple low,
preferably under 10mV
tained its quiescent value. For this reason, capacitor values
of at least 0.47µF are recommended.
The AGC control voltage is carefully managed on-chip to al-
low duty-cycle operation of the MICRF007. When the device
is placed into shutdown mode (SHUT pin is pulled high), the
AGC capacitor floats to retain the voltage. When operation
is resumed, only the voltage droop due to capacitor leakage
must be replenished. A relatively low-leakage capacitor is
recommended when the devices are used in duty-cycled
operation.
To further enhance duty-cycled operation, the AGC push
and pull currents are boosted for approximately 10ms im-
mediately after the device is taken out of shutdown. This
compensates for AGC capacitor voltage droop and reduces
the time to restore the correct AGC voltage. The current is
boosted by a factor of 45.
Selecting C
A C
recommended. Caution! If the capacitor is too large, the
AGC may react too slowly to incoming signals. AGC set-
tling time from a completely discharged (zero-volt) state
is given approximately by this equation:
where:
Selecting C
Voltage droop across the C
should be replenished as quickly as possible after the IC is
enabled. As mentioned above, the MICRF007 boosts the
push-pull current by a factor of 45 immediately after start-up.
This fixed time period is based on the reference oscillator
frequency f
inversely with f
of the shutdown time period should be selected such that the
droop can be replenished within this 10ms period.
Polarity of the droop is unknown, meaning the AGC voltage
could droop up or down. The worst-case from a recovery
standpoint is downward droop, since the AGC pull-up current
is 1/10th magnitude of the pull-down current. The downward
droop is replenished according to the Equation 6:
where:
I = AGC pull-up current for the initial 10ms (67.5µA)
CAGC = AGC capacitor value
∆t = droop recovery time
AGC
∆t = 1.333 × C
C
C
AGC
capacitor in the range of 0.47µF to 4.7µF is typically
AGC
AGC
T
is in µF, and ∆t is in seconds.
. The time is 10.9ms for f
AGC
AGC
=
pin of the device. To maximize system range,
T
It
V
. The value of C
Capacitor in Continuous Mode
Capacitor in Duty-Cycle Mode
AGC
AGC
PP
–0.44
Capacitor
once the control voltage has at-
AGC
AGC
capacitor during shutdown
capacitor and the duration
AGC
T
= 6.00MHz, and varies
capacitor connected
M9999-021705
(5)
(6)
Micrel