Features
• Minimal External Circuitry Requirements, No RF Components on the PC Board Except
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Matching to the Receiver Antenna
High Sensitivity, Especially at Low Data Rates
Sensitivity Reduction Possible Even While Receiving
Fully Integrated VCO
Low Power Consumption Due to Configurable Self Polling with a Programmable Time
Frame Check
Supply Voltage 4.5 V to 5.5 V
Operating Temperature Range -40°C to 105°C
Single-ended RF Input for Easy Adaptation to λ/4 Antenna or Printed Antenna on PCB
Low-cost Solution Due to High Integration Level
ESD Protection According to MIL-STD 883 (4KV HBM) Except Pin POUT (2KV HBM)
High Image Frequency Suppression due to 1 MHz IF in Conjunction with a SAW
Front-end Filter
– Up to 40 dB is Thereby Achievable with Newer SAWs.
Programmable Output Port for Sensitivity Selection or for Controlling External
Periphery
Communication to the Microcontroller Possible via a Single, Bi-directional Data Line
Power Management (Polling) is also Possible by Means of a Separate Pin via the
Microcontroller
2 Different IF Bandwidth Versions are Available (300 kHz and 600 kHz)
UHF ASK
Receiver IC
U3741BM
Description
The U3741BM is a multi-chip PLL receiver device supplied in an SO20 package. It has
been specially developed for the demands of RF low-cost data transmission systems
with low data rates from 1 kBaud to 10 kBaud (1 kBaud to 3.2 kBaud for FSK) in
Manchester or Bi-phase code. The receiver is well suited to operate with Atmel's PLL
RF transmitter U2741B. Its main applications are in the areas of telemetering, security
technology and keyless-entry systems. It can be used in the frequency receiving
range of f0 = 300 MHz to 450 MHz for ASK or FSK data transmission. All the statements made below refer to 433.92-MHz and 315-MHz applications.
Rev. 4662B–RKE–10/04
System Block Diagram
UHF ASK/FSK
Remote control receiver
UHF ASK/FSK
Remote control transmitter
1 Li cell
U2741B
Encoder
ATARx9x
U3741BM
Demod
Control
1...3
µC
PLL
Antenna
Antenna
Keys
XTO
VCO
PLL
Power
amp.
LNA
XTO
VCO
Block Diagram
VS
FSK/ASKDemodulator
and data filter
FSK/ASK
CDEM
RSSI
AVCC
50 kΩ
DEMOD_OUT
DATA
Limiter out
ENABLE
SENS
IF Amp
Sensitivity
reduction
Polling circuit
and
control logic
AGND
POUT
MODE
4th Order
DGND
TEST
FE
CLK
DVCC
Standby logic
LPF
3 MHz
MIXVCC
LFGND
LNAGND
LFVCC
IF Amp
LPF
3 MHz
VCO
XTO
XTO
f
LNA_IN
2
LNA
÷ 64
LF
U3741BM
4662B–RKE–10/04
U3741BM
Pin Configuration
Figure 1. Pinning SO20
SENS
FSK/ASK
CDEM
AVCC
AGND
DGND
MIXVCC
LNAGND
LNA_IN
NC
1
2
3
4
5
6
7
8
9
10
20
19
18
17
16
15
14
13
12
11
DATA
ENABLE
TEST
POUT
MODE
DVCC
XTO
LFGND
LF
LFVCC
Pin Description
Pin
Symbol
1
SENS
2
FSK/ASK
3
CDEM
Lower cut-off frequency data filter
4
AVCC
Analog power supply
5
AGND
Analog ground
6
DGND
Digital ground
7
MIXVCC
Power supply mixer
8
LNAGND
High-frequency ground LNA and mixer
9
LNA_IN
10
NC
11
LFVCC
12
LF
13
LFGND
Function
Sensitivity-control resistor
Selecting FSK/ASK. Low: FSK, High: ASK
RF input
Not connected
Power supply VCO
Loop filter
Ground VCO
14
XTO
15
DVCC
Digital power supply
16
MODE
Selecting 433.92 MHz/315 MHz. Low: 4.90625 MHz (USA). High: 6.76438 (Europe)
17
POUT
Programmable output port
18
TEST
19
ENABLE
20
DATA
Crystal oscillator
Test pin, during operation at GND
Enables the polling mode
Low: polling mode off (sleep mode)
H: polling mode on (active mode)
Data output/configuration input
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4662B–RKE–10/04
RF Front End
The RF front end of the receiver is a heterodyne configuration that converts the input
signal into a 1-MHz IF signal. According to the block diagram, the front end consists of
an LNA (low noise amplifier), LO (local oscillator), a mixer and RF amplifier.
The LO generates the carrier frequency for the mixer via a PLL synthesizer. The XTO
(crystal oscillator) generates the reference frequency fXTO. The VCO (voltage-controlled
oscillator) generates the drive voltage frequency fLO for the mixer. fLO is dependent on
the voltage at pin LF. fLO is divided by a factor of 64. The divided frequency is compared
to fXTO by the phase frequency detector. The current output of the phase frequency
detector is connected to a passive loop filter and thereby generates the control voltage
VLF for the VCO. By means of that configuration, VLF is controlled in a way that fLO/64 is
equal to fXTO. If fLO is determined, fXTO can be calculated using the following formula:
f LO
f XTO = ------64
The XTO is a one-pin oscillator that operates at the series resonance of the quartz crystal. According to Figure 2, the crystal should be connected to GND via a capacitor CL.
The value of that capacitor is recommended by the crystal supplier. The value of CL
should be optimized for the individual board layout to achieve the exact value of fXTO and
hereby of fLO. When designing the system in terms of receiving bandwidth, the accuracy
of the crystal and XTO must be considered.
Figure 2. PLL Peripherals
VS
DVCC
CL
XTO
R1 = 820 Ω
C9 = 4.7 nF
C10 = 1 nF
LFGND
LF
LFVCC
VS
R1
C10
C9
The passive loop filter connected to pin LF is designed for a loop bandwidth of
BLoop = 100 kHz. This value for BLoop exhibits the best possible noise performance of the
LO. Figure 2 shows the appropriate loop filter components to achieve the desired loop
bandwidth. If the filter components are changed for any reason, please note that the
maximum capacitive load at pin LF is limited. If the capacitive load is exceeded, a bit
check may no longer be possible since fLO cannot settle in time before the bit check
starts to evaluate the incoming data stream. Therefore, self polling also does not work in
that case.
fLO is determined by the RF input frequency fRF and the IF frequency fIF using the following formula:
f LO = f RF – f IF
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U3741BM
4662B–RKE–10/04
U3741BM
To determine fLO, the construction of the IF filter must be considered at this point. The
nominal IF frequency is fIF = 1 MHz. To achieve a good accuracy of the filter’s corner frequencies, the filter is tuned by the crystal frequency fXTO. This means that there is a
fixed relation between fIF and fLO that depends on the logic level at pin mode. This is
described by the following formulas:
f LO
MODE = 0 (USA) f IF = --------314
fLO
MODE = 0 (Europe) f IF = ----------------432.92
The relation is designed to achieve the nominal IF frequency of fIF = 1 MHz for most
applications. For applications where fRF = 315 MHz, the MODE must be set to ‘0’. In the
case of fRF = 433.92 MHz, the MODE must be set to ‘1’. For other RF frequencies, fIF is
not equal to 1 MHz. fIF is then dependent on the logical level at pin MODE and on fRF.
Table 1 summarizes the different conditions.
The RF input either from an antenna or from a generator must be transformed to the RF
input pin LNA_IN. The input impedance of that pin is provided in the electrical parameters. The parasitic board inductances and capacitances also influence the input
matching. The RF receiver U3741BM exhibits its highest sensitivity at the best signal-to-noise ratio in the LNA. Hence, noise matching is the best choice for designing the
transformation network.
A good practice when designing the network is to start with power matching. From that
starting point, the values of the components can be varied to some extent to achieve the
best sensitivity.
If a SAW is implemented into the input network, a mirror frequency suppression of
∆P Ref = 40 dB can be achieved. There are SAWs available that exhibit a notch at
∆f = 2 MHz. These SAWs work best for an intermediate frequency of IF = 1 MHz. The
selectivity of the receiver is also improved by using a SAW. In typical automotive applications, a SAW is used.
Figure 3 on page 6 shows a typical input matching network for f RF = 315 MHz and
fRF = 433.92 MHz using a SAW. Figure 4 on page 6 illustrates an input matching to 50 Ω
without a SAW. The input matching networks shown in Figure 4 are the reference networks for the parameters given in the “Electrical Characteristics”.
Table 1. Calculation of LO and IF Frequency
Conditions
Local Oscillator Frequency
Intermediate Frequency
fRF = 315 MHz, MODE = 0
fLO = 314 MHz
fIF = 1 MHz
fRF = 433.92 MHz, MODE = 1
fLO = 432.92 MHz
fIF = 1 MHz
300 MHz < fRF < 365 MHz, MODE = 0
f RF
f LO = ------------------1
1 + ---------314
365 MHz < fRF < 450 MHz, MODE = 1
f RF
f LO = --------------------------1 1 + ----------------432.92
f LO
fIF = --------314
f LO
f IF = ----------------432.92
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4662B–RKE–10/04
Figure 3. Input Matching Network with SAW Filter
8
8
LNAGND
L
C3
9
C3
LNA_IN
C16
100p
fRF = 433.92 MHz
27n
L2
TOKO LL2012
F33NJ
RFIN
L3
1
33n
C2
2
C16
8.2p
100p
OUT
OUT_GND
f RF = 315 MHz
3, 4
22p
TOKO LL2012
F47NJ
L2
TOKO LL2012
F82NJ
RFIN
5
47n
1
6
C2
82n
2
B3551
IN
IN_GND
CASE_GND
8.2p
C17
L3
TOKO LL2012
27NJ
IN_GND
LNA_IN
25n
C17
B3555
IN
9
L
47p
25n
22p
LNAGND
U3741BM
U3741BM
5
OUT
6
OUT_GND
CASE_GND
10p
7, 8
3, 4 7, 8
Figure 4. Input Matching Network without SAW Filter
fRF = 315 MHz
fRF = 433.92 MHz
8
8
LNAGND
U3741BM
U3741BM
9
25n
15p
LNAGND
9
25n
33p
LNA_IN
LNA_IN
RF IN
RFIN
3.3p
3.3p
100p
22n
TOKO LL2012
F22NJ
100p
39n
TOKO LL2012
F39NJ
Please note that for all coupling conditions (see Figure 3 and Figure 4), the bond wire
inductivity of the LNA ground is compensated. C3 forms a series resonance circuit
together with the bond wire. L = 25 nH is a feed inductor to establish a DC path. Its
value is not critical but must be large enough not to detune the series resonance circuit.
For cost reduction, this inductor can be easily printed on the PCB. This configuration
improves the sensitivity of the receiver by about 1 dB to 2 dB.
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U3741BM
4662B–RKE–10/04
U3741BM
Analog Signal Processing
IF Amplifier
The signals coming from the RF front end are filtered by the fully integrated 4th-order IF
filter. The IF center frequency is fIF = 1 MHz for applications where fRF = 315 MHz or
fRF = 433.92 MHz is used. For other RF input frequencies, refer to Table 1 to determine
the center frequency.
The U3741BM is available with 2 different IF bandwidths. U3741BM-M2, the version
with B IF = 300 kHz, is well suited for ASK systems where Atmel’s PLL transmitter
U2741B is used. The receiver U3741BM-M3 employs an IF bandwidth of BIF = 600 kHz.
This version can be used together with the U2741B in FSK and ASK mode. If used in
ASK applications, it allows higher tolerances for the receiver and PLL transmitter crystals. SAW transmitters exhibit much higher transmit frequency tolerances compared to
PLL transmitters. Generally, it is necessary to use BIF = 600 kHz together with such
transmitters.
RSSI Amplifier
The subsequent RSSI amplifier enhances the output signal of the IF amplifier before it is
fed into the demodulator. The dynamic range of this amplifier is DRRSSI = 60 dB. If the
RSSI amplifier is operated within its linear range, the best S/N ratio is maintained in ASK
mode. If the dynamic range is exceeded by the transmitter signal, the S/N ratio is
defined by the ratio of the maximum RSSI output voltage and the RSSI output voltage
due to a disturber. The dynamic range of the RSSI amplifier is exceeded if the RF input
signal is about 60 dB higher compared to the RF input signal at full sensitivity.
In FSK mode, the S/N ratio is not affected by the dynamic range of the RSSI amplifier.
The output voltage of the RSSI amplifier is internally compared to a threshold voltage
VTh_red. VTh_red is determined by the value of the external resistor RSense. RSense is
connected between pin Sense and GND or VS. The output of the comparator is fed into
the digital control logic. By this means it is possible to operate the receiver at lower
sensitivity.
If RSense is connected to VS, the receiver operates at a lower sensitivity. The reduced
sensitivity is defined by the value of R Sense , the maximum sensitivity by the signal-to-noise ratio of the LNA input. The reduced sensitivity is dependent on the signal
strength at the output of the RSSI amplifier.
Since different RF input networks may exhibit slightly different values for the LNA gain,
the sensitivity values given in the electrical characteristics refer to a specific input
matching. This matching is illustrated in Figure 4 on page 6 and exhibits the best possible sensitivity.
RSense can be connected to VS or GND via a microcontroller or by the digital output port
POUT of the U3741BM receiver IC. The receiver can be switched from full sensitivity to
reduced sensitivity or vice versa at any time. In polling mode, the receiver will not wake
up if the RF input signal does not exceed the selected sensitivity. If the receiver is
already active, the data stream at pin DATA will disappear when the input signal is lower
than defined by the reduced sensitivity. Instead of the data stream, the pattern according to Figure 5 is issued at pin DATA to indicate that the receiver is still active.
Figure 5. Steady L State Limited DATA Output Pattern
DATA
tmin2
tDATA_L_max
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4662B–RKE–10/04
FSK/ASK Demodulator
and Data Filter
The signal coming from the RSSI amplifier is converted into the raw data signal by the
ASK/FSK demodulator. The operating mode of the demodulator is set via pin ASK/FSK.
Logic 'L' sets the demodulator to FSK, Logic 'H' sets it into ASK mode.
In ASK mode an automatic threshold control circuit (ATC) is employed to set the detection reference voltage to a value where a good signal-to-noise ratio is achieved. This
circuit also implies the effective suppression of any kind of in-band noise signals or competing transmitters. If the S/N ratio exceeds 10 dB, the data signal can be detected
properly.
The FSK demodulator is intended to be used for an FSK deviation of ∆f ≥ 20 kHz. Lower
values may be used but the sensitivity of the receiver is reduced in that condition. The
minimum usable deviation is dependent on the selected baud rate. In FSK mode, only
BR_Range0 and BR_Range1 are available. In FSK mode, the data signal can be
detected if the S/N Ratio exceeds 2 dB.
The output signal of the demodulator is filtered by the data filter before it is fed into the
digital signal processing circuit. The data filter improves the S/N ratio as its bandpass
can be adopted to the characteristics of the data signal. The data filter consists of a
1st-order high-pass and a 1st-order low-pass filter.
The high-pass filter cut-off frequency is defined by an external capacitor connected to
pin CDEM. The cut-off frequency of the high-pass filter is defined by the following formula:
1
fcu_DF = ------------------------------------------------------------2 × π × 30 kΩ × CDEM
In self-polling mode, the data filter must settle very rapidly to achieve a low current consumption. Therefore, CDEM cannot be increased to very high values if self polling is
used. On the other hand, CDEM must be large enough to meet the data filter requirements according to the data signal. Recommended values for CDEM are given in the
“Electrical Characteristics” on page 23. The values are slightly different for ASK and
FSK mode.
The cut-off frequency of the low-pass filter is defined by the selected baud rate range
(BR_Range). BR_Range is defined in the OPMODE register (refer to section “Configuration of the Receiver” on page 17). BR_Range must be set in accordance to the used
baud rate.
The U3741BM is designed to operate with data coding where the DC level of the data
signal is 50%. This is valid for Manchester and Bi-phase coding. If other modulation
schemes are used, the DC level should always remain within the range of
VDC_min = 33% and VDC_max = 66%. The sensitivity may be reduced by up to 1.5 dB
in that condition.
Each BR_Range is also defined by a minimum and a maximum edge-to-edge time
(tee_sig). These limits are defined in the “Electrical Characteristics” on page 23. They
should not be exceeded to maintain full sensitivity of the receiver.
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U3741BM
4662B–RKE–10/04
U3741BM
Receiving
Characteristics
The RF receiver U3741BM can be operated with and without a SAW front-end filter. In a
typical automotive application, a SAW filter is used to achieve better selectivity. The
selectivity with and without a SAW front end-filter is illustrated in Figure 6. This example
relates to ASK mode and the 300-kHz bandwidth version of the U3741BM. FSK mode
and the 600-kHz version of the receiver exhibit similar behavior. Note that the mirror frequency is reduced by 40 dB. The plots are printed relative to the maximum sensitivity. If
a SAW filter is used, an insertion loss of about 4 dB must be considered.
When designing the system in terms of receiving bandwidth, the LO deviation must be
considered as it also determines the IF center frequency. The total LO deviation is calculated to be the sum of the deviation of the crystal and the XTO deviation of the
U3741BM. Low-cost crystals are specified to be within ±100 ppm. The XTO deviation of
the U3741BM is an additional deviation due to the XTO circuit. This deviation is specified to be ±30 ppm. If a crystal of ±100 ppm is used, the total deviation is ±130 ppm in
that case. Note that the receiving bandwidth and the IF-filter bandwidth are equivalent in
ASK mode but not in FSK mode.
Figure 6. Receiving Frequency Response
0.0
-10.0
-20.0
without SAW
-30.0
dP (dB)
-40.0
-50.0
-60.0
-70.0
-80.0
with SAW
-90.0
-100.0
-6.0
-5.0 -4.0
-3.0
-2.0
-1.0
0.0
1.0
2.0
3.0
4.0
5.0
6.0
df (MHz)
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4662B–RKE–10/04
Polling Circuit and Control Logic
The receiver is designed to consume less than 1 mA while being sensitive to signals
from a corresponding transmitter. This is achieved via the polling circuit. This circuit
enables the signal path periodically for a short time. During this time the bit check logic
verifies the presence of a valid transmitter signal. Only if a valid signal is detected the
receiver remains active and transfers the data to the connected microcontroller. If there
is no valid signal present, the receiver is in sleep mode most of the time resulting in low
current consumption. This condition is called polling mode. A connected microcontroller
is disabled during that time.
All relevant parameters of the polling logic can be configured by the connected microcontroller. This flexibility enables the user to meet the specifications in terms of current
consumption, system response time, data rate etc.
Regarding the number of connection wires to the microcontroller, the receiver is very
flexible. It can be either operated by a single bi-directional line to save ports to the connected microcontroller, it can be operated by up to three uni-directional ports.
Basic Clock Cycle of the
Digital Circuitry
The complete timing of the digital circuitry and the analog filtering is derived from one
clock. According to Figure 7, this clock cycle TClk is derived from the crystal oscillator
(XTO) in combination with a divider. The division factor is controlled by the logical state
at pin MODE. According to section “RF Front End” on page 4, the frequency of the crystal oscillator (f XTO) is defined by the RF input signal (f RFin ) which also defines the
operating frequency of the local oscillator (fLO).
Figure 7. Generation of the Basic Clock Cycle
TClk
MODE
Divider
:14/:10
fXTO
16
L : USA (:10)
H: Europe (:14)
DVCC
15
XTO
XTO
14
Pin MODE can now be set in accordance with the desired clock cycle TClk. TClk controls
the following application-relevant parameters:
•
Timing of the polling circuit including bit check
•
Timing of analog and digital signal processing
•
Timing of register programming
•
Frequency of the reset marker
•
F filter center frequency (fIF0)
Most applications are dominated by two transmission frequencies: fSend = 315 MHz is
mainly used in the USA, fSend = 433.92 MHz in Europe. In order to ease the usage of all
TClk-dependent parameters, the electrical characteristics display three conditions for
each parameter.
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U3741BM
4662B–RKE–10/04
U3741BM
•
USA Applications
(fXTO = 4.90625 MHz, MODE = L, TClk = 2.0383 µs)
•
Europe Applications
(fXTO = 6.76438 MHz, MODE = H, TClk = 2.0697 µs)
•
Other applications
(TClk is dependent on fXTO and on the logical state of pin MODE. The electrical
characteristic is given as a function of TClk).
The clock cycle of some function blocks depends on the selected baud rate range
(BR_Range) which is defined in the OPMODE register. This clock cycle TXClk is defined
by the following formulas for further reference:
BR_Range =
Polling Mode
BR_Range0:
TXClk = 8 × TClk
BR_Range1:
TXClk = 4 × TClk
BR_Range2:
TXClk = 2 × TClk
BR_Range3:
TXClk = 1 × TClk
According to Figure 3 on page 6, the receiver stays in polling mode in a continuous
cycle of three different modes. In sleep mode, the signal processing circuitry is disabled
for the time period TSleep while consuming a low current of IS = ISoff. During the start-up
period, TStartup, all signal processing circuits are enabled and settled. In the following bit
check mode, the incoming data stream is analyzed bit by bit against a valid transmitter
signal. If no valid signal is present, the receiver is set back to sleep mode after the
period TBitcheck. This period varies check by check as it is a statistical process. An average value for TBitcheck is given in “Electrical Characteristics” on page 23. During TStartup
and TBitcheck the current consumption is IS = ISon. The average current consumption in
polling mode is dependent on the duty cycle of the active mode and can be calculated
as:
I Soff × T Sleep + I Son × ( TStartup + T Bitcheck )
I Spoll = -----------------------------------------------------------------------------------------------------------TSleep + TStartup + TBitcheck
During TSleep and TStartup, the receiver is not sensitive to a transmitter signal. To guarantee the reception of a transmitted command, the transmitter must start the telegram with
an adequate preburst. The required length of the preburst is dependent on the polling
parameters TSleep, TStartup, TBitcheck and the startup time of a connected microcontroller
(TStart,µC). TBitcheck thus depends on the actual bit rate and the number of bits (NBitcheck) to
be tested.
The following formula indicates how to calculate the preburst length.
TPreburst ≥ TSleep + TStartup + TBitcheck + TStart_µC
Sleep Mode
The length of period TSleep is defined by the 5-bit word Sleep of the OPMODE register,
the extension factor XSleep, according to Figure 10 on page 13, and the basic clock cycle
TClk. It is calculated to be:
T Sleep = Sleep × X Sleep × 1024 × T Clk
In US and European applications, the maximum value of TSleep is about 60 ms if XSleep is
set to 1. The time resolution is about 2 ms in that case. The sleep time can be extended
to almost half a second by setting XSleep to 8. XSleep can be set to 8 by bit XSleepStd or by
bit XSleepTemp resulting in a different mode of action as described below:
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4662B–RKE–10/04
XSleepStd = 1 implies the standard extension factor. The sleep time is always extended.
XSleepTemp = 1 implies the temporary extension factor. The extended sleep time is used
as long as every bit check is OK. If the bit check fails once, this bit is set back to 0 automatically resulting in a regular sleep time. This functionality can be used to save current
in presence of a modulated disturber similar to an expected transmitter signal. The connected microcontroller is rarely activated in that condition. If the disturber disappears,
the receiver switches back to regular polling and is again sensitive to appropriate transmitter signals.
According to Table 7 on page 19, the highest register value of Sleep sets the receiver to
a permanent sleep condition. The receiver remains in that condition until another value
for Sleep is programmed into the OPMODE register. This function is desirable where
several devices share a single data line.
Figure 8. Polling Mode Flow Chart
Sleep Mode:
All circuits for signal processing are
disabled. Only XTO and polling logic is
enabled.
Output level on pin IC_ACTIVE => low
IS = ISON
TSleep = Sleep × XSleep × 1024 × TClk
Start-up Mode:
The signal processing circuits are
enabled. After the start-up time (TStartup) all
circuits are in stable condition and ready
to receive.
IS = ISON
TStartup
Bit-check Mode:
The incomming data stream is analyzed.
If the timing indicates a valid transmitter
signal, the receiver is set to receiving
mode. Otherwise it is set to Sleep mode.
IS = ISon
TBit-check
Sleep:
5-bit word defined by Sleep0 to Sleep4 in
OPMODE register
XSleep:
Extension factor defined by XSleepTemp
according to Table 8
TClk:
Basic clock cycle defined by fXTO and pin
MODE
TStartup:
Is defined by the selected baud rate range
and TClk. The baud-rate range is defined
by Baud0 and Baud1 in the OPMODE
register.
TBit-check:
Depends on the result of the bit check.
If the bit check is ok, TBit-check depends
on the number of bits to be checked
(NBit-checked) and on the utilized data rate.
If the bit check fails, the average time
period for that check depends on the
selected baud-rate range on TClk. The
baud-rate range is defined by Baud0 and
Baud1 in the OPMODE register.
Bit-check
OK?
NO
YES
Receiving Mode:
The receiver is turned on permanently
and passes the data stream to the
connected microcontroller. It can be set to
Sleep mode through an OFF command
via pin DATA or ENABLE
IS = ISON
OFF command
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U3741BM
4662B–RKE–10/04
U3741BM
Figure 9. Timing Diagram for a Completely Successful Bit Check
Number of Checked Bits: 3
Bit check ok
Enable IC
Bit check
1/2 Bit
1/2 Bit
1/2 Bit
1/2 Bit
1/2 Bit
1/2 Bit
Dem_out
DATA
Polling mode
Receiving mode
Bit Check Mode
In bit check mode, the incoming data stream is examined to distinguish between a valid
signal from a corresponding transmitter and signals due to noise. This is done by subsequent time frame checks where the distances between 2 signal edges are continuously
compared to a programmable time window. The maximum count of this edge-to-edge
test, before the receiver switches to receiving, mode is also programmable.
Configuring the Bit Check
Assuming a modulation scheme that contains 2 edges per bit, two time frame checks
are verifying one bit. This is valid for Manchester, Bi-phase and most other modulation
schemes. The maximum count of bits to be checked can be set to 0, 3, 6 or 9 bits via the
variable NBitcheck in the OPMODE register. This implies 0, 6, 12 and 18 edge-to-edge
checks respectively. If NBitcheck is set to a higher value, the receiver is less likely to
switch to the receiving mode due to noise. In the presence of a valid transmitter signal,
the bit check takes less time if NBitcheck is set to a lower value. In polling mode, the bit
check time is not dependent on NBitcheck. Figure 9 shows an example where 3 bits are
tested successfully and the data signal is transferred to pin DATA.
According to Figure 10, the time window for the bit check is defined by two separate
time limits. If the edge-to-edge time tee is in between the lower bit check limit TLim_min and
the upper bit check limit TLim_max , the check will be continued. If t ee is smaller than
T Lim_min or t ee exceeds T Lim_max , the bit check will be terminated and the receiver
switches to sleep mode.
Figure 10. Valid Time Window for Bit Check
1/fSig
Dem_out
tee
Tlim_min
Tlim_max
For best noise immunity it is recommended to use a low span between TLim_min and
TLim_max. This is achieved using a fixed frequency at a 50% duty cycle for the transmitter
preburst. A ‘11111...’ or a ‘10101...’ sequence in Manchester or Bi-phase is a good
choice in this regard. A good compromise between receiver sensitivity and susceptibility
to noise is a time window of ±25% regarding the expected edge-to-edge time tee. Using
preburst patterns that contain various edge-to-edge time periods, the bit check limits
must be programmed according to the required span.
13
4662B–RKE–10/04
The bit check limits are determined by means of the formula below:
TLim_min = Lim_min × TXClk
TLim_max = (Lim_max –1) × TXClk
Lim_min and Lim_max are defined by a 5-bit word each within the LIMIT register.
Using the above formulas, Lim_min and Lim_max can be determined according to the
required TLim_min , TLim_max and TXClk. The time resolution when defining TLim_min and
TLim_max is TXClk. The minimum edge-to-edge time tee (tDATA_L_min, tDATA_H_min) is defined
according to the section “Receiving Mode” on page 15. Due to this, the lower limit
should be set to Lim_min ≥ 10. The maximum value of the upper limit is Lim_max = 63.
Figure 11, Figure 12 and Figure 13 on page 15 illustrate the bit check for the default bit
check limits Lim_min = 14 and Lim_max = 24. When the IC is enabled, the signal processing circuits are enabled during TStartup. The output of the ASK/FSK demodulator
(Dem_out) is undefined during that period. When the bit check becomes active, the bit
check counter is clocked with the cycle TXClk.
Figure 11 shows how the bit check proceeds if the bit-check counter value CV_Lim is
within the limits defined by Lim_min and Lim_max at the occurrence of a signal edge. In
Figure 12, the bit check fails as the value CV_lim is lower than the limit Lim_min. The bit
check also fails if CV_Lim reaches Lim_max. This is illustrated in Figure 13 on page 15.
Figure 11. Timing Diagram During Bit Check
(Lim_min = 14, Lim_max = 24)
Bit check ok
Bit check ok
Enable IC
TStartup
Bit check
1/2 Bit
1/2 Bit
1/2 Bit
Dem_out
Bit check
Counter
1
0
2 3 4
5 6
7 8 1 2 3
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 1
2
3 4 5
6 7
8 9 10 11 12 13 14 15 1
2 3 4
TXClk
Figure 12. Timing Diagram for Failed Bit Check (Condition: CV_Lim < Lim_min)
(Lim_min = 14, Lim_max = 24)
Bit check failed ( CV_Lim < Lim_min )
Enable IC
Bit check
1/2 Bit
Dem_out
Bit check
Counter
0
Startup Mode
14
1 2 3 4 5 6 1 2 3 4 5 6 7 8 9 101112
Bit check Mode
0
Sleep Mode
U3741BM
4662B–RKE–10/04
U3741BM
Figure 13. Timing Diagram for Failed Bit Check (Condition: CV_Lim ≥ Lim_max)
(Lim_min = 14, Lim_max = 24)
Bit check failed (CV_Lim = Lim_max)
Enable IC
Bit check
1/2 Bit
Dem_out
Bit check
Counter
1 2 3 4 5 6 7 1 2 3 4 5 6 7 8 9 10 1112 13141516171819 20 21222324
0
Startup Mode
Duration of the Bit Check
Bit check Mode
0
Sleep Mode
If no transmitter signal is present during the bit check, the output of the ASK/FSK
demodulator delivers random signals. The bit check is a statistical process and TBitcheck
varies for each check. Therefore, an average value for TBitcheck is given in “Electrical
Characteristics”. TBitcheck depends on the selected baud rate range and on TClk. A higher
baudrate range causes a lower value for TBitcheck resulting in lower current consumption
in polling mode.
In the presence of a valid transmitter signal, TBitcheck is dependant on the frequency of
that signal, fSig and the count of the checked bits, NBitcheck. A higher value for NBitcheck
thereby results in a longer period for TBitcheck requiring a higher value for the transmitter
preburst TPreburst.
Receiving Mode
If the bit check has been successful for all bits specified by N Bitcheck , the receiver
switches to receiving mode. According to Figure 9 on page 13, the internal data signal is
switched to pin DATA in that case. A connected microcontroller can be woken up by the
negative edge at pin DATA. The receiver stays in that condition until it is switched back
to polling mode explicitly.
Digital Signal Processing
The data from the ASK/FSK demodulator (Dem_out) is digitally processed in different
ways and as a result converted into the output signal data. This processing depends on
the selected baud rate range (BR_Range). Figure 14 on page 16 illustrates how
Dem_out is synchronized by the extended clock cycle TXClk. This clock is also used for
the bit check counter. Data can change its state only after T XClk elapsed. The
edge-to-edge time period tee of the Data signal as a result is always an integral multiple
of TXClk.
The minimum time period between two edges of the data signal is limited to
tee ≥ TDATA_min. This implies an efficient suppression of spikes at the DATA output. At the
same time, it limits the maximum frequency of edges at DATA. This eases the interrupt
handling of a connected microcontroller. TDATA_min is to some extent affected by the preceding edge-to-edge time interval tee as illustrated in Figure 15. If tee is in between the
specified bit check limits, the following level is frozen for the time period
TDATA_min = tmin1, in case of tee being outside that bit check limits TDATA_min = tmin2 is the
relevant stable time period.
The maximum time period for DATA to be low is limited to TDATA_L_max. This function
ensures a finite response time during programming or switching off the receiver via pin
DATA. TDATA_L_max is thereby longer than the maximum time period indicated by the
transmitter data stream. Figure 16 gives an example where Dem_out remains low after
the receiver has switched to receiving mode.
15
4662B–RKE–10/04
Figure 14. Synchronization of the Demodulator Output
TXClk
Clock Bitcheck
counter
Dem_out
DATA
tee
Figure 15. Debouncing of the Demodulator Output
Dem_out
DATA
Lim_min ≤ CV_Lim < Lim_max
tmin1
tee
CV_Lim < Lim_min or CV_Lim ≥ Lim_max
tmin2
tee
Figure 16. Steady L State Limited DATA Output Pattern after Transmission
Enable IC
Bit check
Dem_out
DATA
Sleep mode
Bit check mode
Receiving mode
tmin2
tDATA_L_max
After the end of a data transmission, the receiver remains active and random noise
pulses appear at pin DATA. The edge-to-edge time period tee of the majority of these
noise pulses is equal to or slightly higher than TDATA_min.
Switching the Receiver Back
to Sleep Mode
The receiver can be set back to polling mode via pin DATA or via pin ENABLE.
When using pin DATA, this pin must be pulled to low for the period t1 by the connected
microcontroller. Figure 17 illustrates the timing of the OFF command (see also Figure 21
on page 21). The minimum value of t1 depends on the BR_Range. The maximum value
for t1 is not limited but it is recommended not to exceed the specified value to prevent
erasing the reset marker. This item is explained in more detail in the section “Configuration of the Receiver” on page 17. Setting the receiver to sleep mode via DATA is
achieved by programming bit 1 of the OPMODE register to 1. Only one sync pulse (t3) is
issued.
The duration of the OFF command is determined by the sum of t1, t2 and t10. After the
OFF command, the sleep time TSleep elapses. Note that the capacitive load at pin DATA
is limited. The resulting time constant τ together with an optional external pull-up resistor may not be exceeded to ensure proper operation.
16
U3741BM
4662B–RKE–10/04
U3741BM
If the receiver is set to polling mode via pin ENABLE, an ‘L’ pulse (TDoze) must be issued
at that pin. Figure 18 illustrates the timing of that command. After the positive edge of
this pulse, the sleep time TSleep elapses. The receiver remains in sleep mode as long as
ENABLE is held to ‘L’. If the receiver is polled exclusively by a microcontroller, TSleep can
be programmed to 0 to enable a instantaneous response time. This command is the
faster option than via pin DATA at the cost of an additional connection to the
microcontroller.
Figure 17. Timing Diagram of the OFF Command Via Pin DATA
t1
t2
t3
t5
t4
t10
t7
Out1 (microcontroller)
DATA (U3741BM)
X
X
Serial bi-directional
data line
X
X
Bit 1
("1")
(Start bit)
Receiver
on
TSleep
Startup mode
OFF command
Figure 18. Timing Diagram of the OFF Command Via Pin ENABLE
TDoze
TSleep
toff
ENABLE
DATA (U3741BM)
X
X
Serial bi-directional
data line
X
X
Receiver on
Configuration of the
Receiver
Startup mode
The U3741BM receiver is configured via two 12-bit RAM registers called OPMODE and
LIMIT. The registers can be programmed by means of the bi-directional DATA port. If
the register contents have changed due to a voltage drop, this condition is indicated by a
certain output pattern called reset marker (RM). The receiver must be reprogrammed in
that case. After a power-on reset (POR), the registers are set to default mode. If the
receiver is operated in default mode, there is no need to program the registers.
Table 3 on page 18 shows the structure of the registers. According to Table 2 on page
18, bit 1 defines if the receiver is set back to polling mode via the OFF command, (see
section “Receiving Mode” on page 15) or if it is programmed. Bit 2 represents the register address. It selects the appropriate register to be programmed.
17
4662B–RKE–10/04
Table 2. Effect of Bit 1 and Bit 2 in Programming the Registers
Bit 1
Bit 2
Action
1
x
The receiver is set back to polling mode (OFF command)
0
1
The OPMODE register is programmed
0
0
The LIMIT register is programmed
Table 4 and the following illustrate the effect of the individual configuration words. The
default configuration is highlighted for each word.
BR_Range sets the appropriate baud rate range. At the same time it defines XLim. XLim
is used to define the bit check limits TLim_min and TLim_max as shown in Table 4.
POUT can be used to control the sensitivity of the receiver. In that application, POUT is
set to 1 to reduce the sensitivity. This implies that the receiver operates with full sensitivity after a POR.
Table 3. Effect of the Configuration Words within the Registers
Bit1 Bit2
Bit2
Bit4
Bit5
Bit6
Bit7
Bit8
Bit9
Bit10
Bit11
Bit12
Bit13
Bit14
OFF Command
1
OPMODE Register
0
1
0
1
BR_Range
NBitcheck
VPOUT
Sleep
XSleep
Baud1
Baud0
BitChk1
BitChk0
POUT
Sleep4
Sleep3
Sleep2
Sleep1
Sleep0
XSleep Std
XSleep Temp
0
0
1
0
0
0
1
0
1
1
0
0
(Default)
LIMIT Register
0
0
0
0
Lim_min
Lim_max
Lim_min5 Lim_min4 Lim_min3 Lim_min2 Lim_min1 Lim_min0 Lim_max5 Lim_max4 Lim_max3 Lim_max2 Lim_max1 Lim_max0
(Default)
0
0
1
1
1
0
0
1
1
0
0
0
Table 4. Effect of the Configuration Word BR_Range
BR_Range
18
Baud1
Baud0
Baud Rate Range/Extension Factor for Bit Check Limits (XLim)
0
0
BR_Range0 (application USA/Europe: BR_Range0 = 1.0 kBaud to 1.8 kBaud) (Default)
XLim = 8 (Default)
0
1
BR_Range1 (application USA/Europe: BR_Range1 = 1.8 kBaud to 3.2 kBaud)
XLim = 4
1
0
BR_Range2 (application USA/Europe: BR_Range2 = 3.2 kBaud to 5.6 kBaud)
XLim = 2
1
1
BR_Range3 (Application USA/Europe: BR_Range3 = 5.6 kBaud to 10 kBaud)
XLim = 1
U3741BM
4662B–RKE–10/04
U3741BM
Table 5. Effect of the Configuration Word NBitcheck
NBitcheck
BitChk1
BitChk0
Number of Bits to be Checked
0
0
0
0
1
3
1
0
6 (Default)
1
1
9
Table 6. Effect of the Configuration Bit VPOUT
VPOUT
Level of the Multi-purpose Output Port POUT
POUT
0
0 (Default)
1
1
Table 7. Effect of the Configuration Word Sleep
Sleep
Sleep4
Sleep3
Sleep2
Sleep1
Sleep0
Start Value for Sleep Counter (TSleep = Sleep × XSleep × 1024 × TClk)
0
0
0
0
0
0 (Receiver is continuously polling until a valid signal occurs)
0
0
0
0
1
1 (TSleep ≈ 2ms for XSleep = 1 in US-/European applications)
0
0
0
1
0
2
0
0
0
1
1
3
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
0
1
0
1
1
11 (USA: TSleep = 22.96 ms, Europe: TSleep = 23.31 ms) (Default)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
1
1
0
1
29
1
1
1
1
0
30
1
1
1
1
1
31 (Permanent sleep mode)
Table 8. Effect of the Configuration Word XSleep
XSleep
XSleepStd
XSleepTemp
Extension Factor for Sleep Time (TSleep = Sleep × XSleep × 1024 × TClk)
0
0
1 (Default)
0
1
8 (XSleep is reset to 1 if bit check fails once)
1
0
8 (XSleep is set permanently)
1
1
8 (XSleep is set permanently)
19
4662B–RKE–10/04
Table 9. Effect of the Configuration Word Lim_min
Lim_min
Lower Limit Value for Bit Check
Lim_min < 10 is not applicable
(TLim_min = Lim_min × XLim × TClk)
0
0
1
0
1
0
10
0
0
1
0
1
1
11
0
0
1
1
0
0
12
0
0
1
1
0
1
13
0
0
1
1
1
0
14 (Default)
(USA: TLim_min = 228 µs, Europe: TLim_min = 232 µs)
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
1
1
1
0
1
61
1
1
1
1
1
0
62
1
1
1
1
1
1
63
Table 10. Effect of the Configuration Word Lim_max
Lim_max
Upper Limit Value for Bit Check
Lim_max < 12 is not applicable
(TLim_max = (Lim_max - 1) × XLim × TClk)
0
0
1
1
0
0
12
0
0
1
1
0
1
13
0
0
1
1
1
0
14
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
0
1
1
0
0
0
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
.
1
1
1
1
0
1
61
1
1
1
1
1
0
62
1
1
1
1
1
1
63
Conservation of the Register
Information
24 (Default)
(USA: TLim_max = 375 µs, Europe: TLim_max = 381 µs)
The U3741BM has an integrated power-on reset and brown-out detection circuitry to
provide a mechanism to preserve the RAM register information.
According to Figure 19 on page 21, a power-on reset (POR) is generated if the supply
voltage VS drops below the threshold voltage VThReset. The default parameters are programmed into the configuration registers in that condition. Once VS exceeds VThReset,
the POR is canceled after the minimum reset period tRst. A POR is also generated when
the supply voltage of the receiver is turned on.
To indicate that condition, the receiver displays a reset marker (RM) at pin DATA after a
reset. The RM is represented by the fixed frequency fRM at a 50% duty cycle. RM can be
canceled via an ‘L’ pulse t1 at pin DATA. The RM implies the following characteristics:
20
U3741BM
4662B–RKE–10/04
U3741BM
•
fRM is lower than the lowest feasible frequency of a data signal. By this means, RM
cannot be misinterpreted by the connected microcontroller.
•
If the receiver is set back to polling mode via pin DATA, RM cannot be canceled by
accident if t1 is applied according to the proposal in the section “Programming the
Configuration Register” on page 21.
By means of that mechanism, the receiver cannot lose its register information without
communicating that condition via the reset marker RM.
Figure 19. Generation of the Power-on Reset
VS
VThReset
POR
tRst
DATA (U3741BM)
X
1/fRM
Figure 20. Timing of the Register Programming
t1
t2
t3
t5
t4
t9
TSleep
t8
t6
t7
Out1
(microcontroller)
DATA (U3741BM)
X
X
Serial bi-directional
data line
X
X
Receiver
on
Programming the
Configuration Register
Bit 1
("0")
Bit 2
("1")
(Start bit)
(Register select)
Bit 13
("0")
(Poll8)
Bit 14
("1")
(Poll8R)
Startup
mode
Programming Frame
The configuration registers are programmed serially via the bi-directional data line
according to Figure 20 and Figure 21.
Figure 21. One-wire Connection to a Microcontroller
U3741BM
microcontroller
Internal pull-up
resistor
Bi-directional
data line
DATA
I/O
Out 1 (µC)
DATA (U3741BM)
21
4662B–RKE–10/04
To start programming, the serial data line DATA is pulled to ‘L’ for the time period t1 by
the microcontroller. When DATA has been released, the receiver becomes the master
device. When the programming delay period t2 has elapsed, it emits 14 subsequent
synchronization pulses with the pulse length t3. After each of these pulses, a programming window occurs. The delay until the program window starts is determined by t4, the
duration is defined by t5. Within the programming window, the individual bits are set. If
the microcontroller pulls down pin DATA for the time period t7 during t5, the according
bit is set to ‘0’. If no programming pulse t7 is issued, this bit is set to ‘1’. All 14 bits are
subsequently programmed in this way. The time frame to program a bit is defined by t6.
Bit 14 is followed by the equivalent time window t9. During this window, the equivalent
acknowledge pulse t8 (E_Ack) occurs if the mode word just programmed is equivalent to
the mode word that was already stored in that register. E_Ack should be used to verify
that the mode word was correctly transferred to the register. The register must be programmed twice in that case.
Programming of a register is possible both during sleep and active mode of the receiver.
During programming, the LNA, LO, low-pass filter, IF-amplifier and the demodulator are
disabled.
The programming start pulse t1 initiates the programming of the configuration registers.
If bit 1 is set to ‘1’, it represents the OFF command to set the receiver back to polling
mode at the same time. For the length of the programming start pulse t1, the following
convention should be considered:
•
t1(min) < t1 < 1535 × TClk: [t1(min) is the minimum specified value for the relevant
BR_Range]
Programming (respectively OFF command) is initiated if the receiver is not in reset
mode. If the receiver is in reset mode, programming (respectively Off command) is not
initiated, and the reset marker RM is still present at pin DATA.
This period is generally used to switch the receiver to polling mode. In a reset condition,
RM is not canceled by accident.
•
t1 > 5632 × TClk
Programming (respectively OFF command) is initiated in any case. RM is cancelled if
present. This period is used if the connected microcontroller detected RM. If a configuration register is programmed, this time period for t1 can generally be used.
Note that the capacitive load at pin DATA is limited. The resulting time constant t
together with an optional external pull-up resistor may not be exceeded to ensure proper
operation.
22
U3741BM
4662B–RKE–10/04
U3741BM
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Parameters
Max.
Unit
Supply voltage
Symbol
VS
6
V
Power dissipation
Ptot
450
mW
Tj
150
°C
Junction temperature
Min.
Storage temperature
Tstg
-55
+125
°C
Ambient temperature
Tamb
-40
+105
°C
10
dBm
Maximum input level, input matched to 50 W
Pin_max
Thermal Resistance
Parameters
Junction ambient
Symbol
Value
Unit
RthJA
100
K/W
Electrical Characteristics
All parameters refer to GND, Tamb = -40°C to +105°C, VS = 4.5 V to 5.5 V, f0 = 433.92 MHz and f0 = 315 MHz, unless otherwise specified.
(VS = 5 V, Tamb = 25°C)
6.76438-Mhz Osc.
(Mode 1)
Parameter
Test Condition
Symbol
Min.
Typ.
Max.
4.90625-Mhz Osc.
(Mode 0)
Min.
Typ.
Max.
Variable Oscillator
Min.
Typ.
Max.
Unit
Basic Clock Cycle of the Digital Circuitry
Basic clock
cycle
MODE = 0 (USA)
MODE = 1 (Europe)
TClk
Extended
basic clock
cycle
BR_Range0
BR_Range1
BR_Range2
BR_Range3
TXClk
2.0383
1/(fXTO/10)
1/(fXTO/14)
µs
µs
16.6
8.3
4.1
2.1
16.3
8.2
4.1
2.0
8 × TClk
4 × TClk
2 × TClk
1 × TClk
µs
µs
µs
µs
TSleep
Sleep ×
XSleep ×
1024 ×
2.0697
Sleep ×
XSleep ×
1024 ×
2.0383
Sleep ×
XSleep ×
1024 × TClk
ms
1855
1061
1061
663
1827
1045
1045
653
896.5
512.5
512.5
320.5 × TClk
µs
µs
µs
µs
0.45
0.24
0.14
0.14
0.47
0.26
0.16
0.15
2.0697
Polling Mode
Sleep time
Sleep and XSleep are
defined in the
OPMODE register
Start-up time
BR_Range0
BR_Range1
BR_Range2
BR_Range3
TStartup
Average bit check
time while polling
BR_Range0
BR_Range1
BR_Range2
BR_Range3
TBitcheck
Bit check time for a
valid input signal fSig
NBitcheck = 0
NBitcheck = 3
NBitcheck = 6
NBitcheck = 9
TBitcheck
Time for Bit
Check
3/fSig
6/fSig
9/fSig
3.5/fSig
6.5/fSig
9.5/fSig
3/fSig
6/fSig
9/fSig
ms
ms
ms
ms
3.5/fSig
6.5/fSig
9.5/fSig
TXClk
3.5/fSig
6.5/fSig
9.5/fSig
ms
ms
ms
ms
23
4662B–RKE–10/04
Electrical Characteristics (Continued)
All parameters refer to GND, Tamb = -40°C to +105°C, VS = 4.5 V to 5.5 V, f0 = 433.92 MHz and f0 = 315 MHz, unless otherwise specified.
(VS = 5 V, Tamb = 25°C)
6.76438-Mhz Osc.
(Mode 1)
Parameter
Test Condition
Symbol
Min.
Typ.
Max.
4.90625-Mhz Osc.
(Mode 0)
Min.
Typ.
Max.
Variable Oscillator
Min.
Typ.
Max.
Unit
Receiving Mode
Intermediate
frequency
MODE=0 (USA)
MODE=1 (Europe)
Baud rate
range
BR_Range0
BR_Range1
BR_Range2
BR_Range3
Minimum time BR_Range0
period
between
BR_Range1
edges at
pin DATA
BR_Range2
(Figure 15)
BR_Range3
BR_Range0
Maximum low
BR_Range1
period at DATA
BR_Range2
(Figure 16)
BR_Range3
OFF
command at
pin ENABLE
(Figure 18)
fIF
BR_Range
1.0
1.0
1.8
3.2
5.6
TDATA_min
tmin1
tmin2
tmin1
tmin2
tmin1
tmin2
tmin1
tmin2
TDATA_L_max
tDoze
fXTO × 64/314
fXTO × 64/432.92
1.0
1.8
3.2
5.6
10.0
1.0
1.8
3.2
5.6
1.8
3.2
5.6
10.0
BR_Range0 ×
BR_Range1 ×
BR_Range2 ×
BR_Range3 ×
MHz
MHz
2 µs/TClk
2 µs/TClk
2 µs/TClk
2 µs/TClk
kBaud
kBaud
kBaud
kBaud
149
182
75
91
37.3
45.5
18.6
22.8
147
179
73
90
36.7
44.8
18.3
22.4
9 × TXClk
11 × TXCl
9 × TXClk
11 × TXClk
9 × TXClk
11 × TXClk
9 × TXClk
11 × TXClk
µs
µs
µs
µs
µs
µs
µs
µs
2169
1085
542
271
2136
1068
534
267
131 ×
131 ×
131 ×
131 ×
µs
µs
µs
µs
3.1
TXClk
TXClk
TXClk
TXClk
1.5 ¥
TClk
3.05
µs
Configuration of the Receiver
Frequency of
the reset
marker
(Figure 19)
Programming
start pulse
(Figure 17,
Figure 20)
fRM
1
--------------------------------4096 × T CLK
119.8
BR_Range0
2188
3176
2155
3128
BR_Range1
1104
3176
1087
3128
561
3176
553
3128
290
3176
286
3128
BR_Range2
t1
BR_Range3
after POR
11656
Programming
delay period
(Figure 17,
Figure 20)
t2
Synchronization pulse
(Figure 17,
Figure 20)
t3
24
117.9
11479
795
798
265
783
786
261
Hz
1057 ×
TClk
533 ×
TClk
271 ×
TClk
140 ×
TClk
5632 ×
TClk
1535 ×
TClk
1535 ×
TClk
1535 ×
TClk
1535 ×
TClk
384.5 ×
TClk
385.5
× TClk
128 × TClk
µs
µs
µs
U3741BM
4662B–RKE–10/04
U3741BM
Electrical Characteristics (Continued)
All parameters refer to GND, Tamb = -40°C to +105°C, VS = 4.5 V to 5.5 V, f0 = 433.92 MHz and f0 = 315 MHz, unless otherwise specified.
(VS = 5 V, Tamb = 25°C)
6.76438-Mhz Osc.
(Mode 1)
Parameter
Test Condition
Symbol
Min.
Typ.
Max.
4.90625-Mhz Osc.
(Mode 0)
Min.
Typ.
Max.
Variable Oscillator
Min.
Typ.
Max.
Unit
Delay until the
program
window starts
(Figure 17,
Figure 20)
t4
131
129
63.5 × TClk
µs
Programming
window
(Figure 17,
Figure 20)
t5
530
522
256 × TClk
µs
Time frame
of a bit
(Figure 20)
t6
1060
1044
512 × TClk
µs
Programming
pulse (Figure
17, Figure 20)
t7
Equivalent
acknowledge
pulse: E_Ack
(Figure 20)
t8
265
261
128 × TClk
µs
Equivalent
time window
(Figure 20)
t9
534
526
258 × TClk
µs
OFF-bit
programming
window
(Figure 17)
t10
930
916
449.5 × TClk
µs
133
529
131
521
256 ×
TClk
64 ×
TClk
µs
Electrical Characteristics
All parameters refer to GND, Tamb = -40°C to +105°C, VS = 4.5 V to 5.5 V, f0 = 433.92 MHz and f0 = 315 MHz, unless otherwise specified.
(VS = 5 V, Tamb = 25°C)
Parameters
Typ.
Max.
Unit
ISoff
190
350
µA
IC active
(startup-, bit check-, receiving mode)
pin DATA = H
ISon
7.0
8.6
mA
Third-order intercept point
LNA/mixer/IF amplifier
input matched according to Figure 4
IIP3
-28
LO spurious emission at RFIn
Input matched according to Figure 4,
required according to I-ETS 300220
ISLORF
-73
Noise figure LNA and mixer (DSB)
Input matching according to Figure 4
NF
7
dB
LNA_IN input impedance
at 433.92 MHz
at 315 MHz
ZiLNA_IN
1.0 || 1.56
1.3 || 1.0
kΩ || pF
kΩ || pF
IP1db
-40
dBm
Current consumption
Test Conditions
Sleep mode
(XTO and polling logic active)
Symbol
Min.
LNA Mixer
1 dB compression point (LNA, mixer, IF Input matched according to Figure 4,
referred to RFin
amplifier)
dBm
-57
dBm
25
4662B–RKE–10/04
Electrical Characteristics (Continued)
All parameters refer to GND, Tamb = -40°C to +105°C, VS = 4.5 V to 5.5 V, f0 = 433.92 MHz and f0 = 315 MHz, unless otherwise specified.
(VS = 5 V, Tamb = 25°C)
Parameters
Test Conditions
Maximum input level
Input matched according to Figure 4,
BER ≤10-3,
ASK mode
Symbol
Min.
Typ.
Max.
Unit
-28
-20
dBm
dBm
449
MHz
-93
-113
-90
-110
dBC/Hz
dBC/Hz
-55
-47
dBC
Pin_max
Local Oscillator
Operating frequency range VCO
fVCO
Phase noise VCO/LO
fosc = 432.92 MHz
at 1 MHz
at 10 MHz
Spurious of the VCO
at ±fXTO
VCO gain
299
L (fm)
KVCO
190
MHz/V
Loop bandwidth of the PLL
For best LO noise
(design parameter)
R1 = 820 Ω
C9 = 4.7 nF
C10 = 1 nF
BLoop
100
kHz
Capacitive load at pin LF
The capacitive load at pin LF is limited
if bit check is used. The limitation
therefore also applies to self polling.
CLF_tot
XTO operating frequency
XTO crystal frequency,
appropriate load capacitance must be
connected to XTAL
6.764375 MHz
fXTO
4.90625 MHz
Series resonance resistor of the crystal
fXTO = 6.764 MHz
4.906 MHz
Static capacitance of the crystal
10
6.764375 6.764375 6.764375
-30 ppm
+30 ppm
4.90625 4.90625 4.90625
-30 ppm
+30 ppm
nF
MHz
MHz
RS
150
220
Ω
Ω
Cxto
6.5
pF
Analog Signal Processing
Input sensitivity ASK 300-kHz IF filter
Input matched according to Figure 4
ASK (level of carrier)
BER ≤10-3, B = 300 kHz
fin = 433.92 MHz/315 MHz
T = 25°C, VS = 5 V
fIF = 1 MHz
Input sensitivity ASK 300-kHz IF filter
BR_Range0
-109
-111
-113
dBm
Input sensitivity ASK 300-kHz IF filter
BR_Range1
-107
-109
-111
dBm
Input sensitivity ASK 300-kHz IF filter
BR_Range2
-106
-108
-110
dBm
Input sensitivity ASK 300-kHz IF filter
BR_Range3
-104
-106
-108
dBm
Input sensitivity ASK 600 kHz IF filter
Input matched according to Figure 4
ASK (level of carrier)
BER ≤10-3, B = 600 kHz
fin = 433.92 MHz/315 MHz
T = 25°C, VS = 5 V
fIF = 1 MHz
26
PRef_ASK
PRef_ASK
U3741BM
4662B–RKE–10/04
U3741BM
Electrical Characteristics (Continued)
All parameters refer to GND, Tamb = -40°C to +105°C, VS = 4.5 V to 5.5 V, f0 = 433.92 MHz and f0 = 315 MHz, unless otherwise specified.
(VS = 5 V, Tamb = 25°C)
Parameters
Test Conditions
Input sensitivity ASK 600 kHz IF filter
Min.
Typ.
Max.
Unit
BR_Range0
-108
-110
-112
dBm
Input sensitivity ASK 600 kHz IF filter
BR_Range1
-106.5
-108.5
-110.5
dBm
Input sensitivity ASK 600 kHz IF filter
BR_Range2
-106
-108
-110
dBm
Input sensitivity ASK 600 kHz IF filter
BR_Range3
-104
-106
-108
dBm
Sensitivity variation ASK for the full
operating range compared to
Tamb = 25°C, VS = 5 V
300-kHz and 600-kHz version
fin = 433.92 MHz/315 MHz
fIF = 1 MHz
PASK = PRef_ASK + ∆PRef
∆PRef
+2.5
-1.5
dB
Sensitivity variation ASK for full
operating range including IF filter
compared to Tamb = 25°C, VS = 5 V
300-kHz version
fin = 433.92 MHz/315 MHz
fIF = 0.88 MHz to 1.12 MHz
fIF = 0.85 MHz to 1.15 MHz
PASK = PRef_ASK + ∆PRef
∆PRef
+5.5
+7.5
-1.5
-1.5
dB
dB
Sensitivity variation ASK for full
operating range including IF filter
compared to Tamb = 25°C, VS = 5 V
600-kHz version
fin = 433.92 MHz/315 MHz
fIF = 0.79 MHz to 1.21 MHz
fIF = 0.73 MHz to 1.27 MHz
PASK = PRef_ASK + ∆PRef
∆PRef
+5.5
+7.5
-1.5
-1.5
dB
dB
Input sensitivity FSK 600 kHz IF filter
Input matched according to Figure 4,
BER ≤10-3, B = 600 kHz
fin = 433.92 MHz/315 MHz
T = 25°C, VS = 5 V
fIF = 1 MHz
Input sensitivity FSK 600 kHz IF filter
BR_Range0
df ≥ ±20 kHz
df ≥ ±30 kHz
-95.5
-96.5
-97.5
-98.5
-99.5
-100.5
dBm
dBm
Input sensitivity FSK 600 kHz IF filter
BR_Range1
df ≥ ±20 kHz
df ≥ ±30 kHz
-94.5
-95.5
-96.5
-97.5
-98.5
-99.5
dBm
dBm
Sensitivity variation FSK for the full
operating range compared to
Tamb = 25°C, VS = 5 V
600-kHz version
fin = 433.92 MHz/315 MHz
fIF = 1 MHz
PFSK = PRef_FSK + ∆PRef
∆PRef
+2.5
-1.5
dB
Sensitivity variation FSK for full
operating range including IF filter
compared to Tamb = 25°C, VS = 5 V
600-kHz version
fin = 433.92 MHz/315 MHz
fIF = 0.86 MHz to 1.14 MHz
fIF = 0.82 MHz to 1.18 MHz
PFSK = PRef_FSK + ∆PRef
∆PRef
+5.5
+7.5
-1.5
-1.5
dB
dB
FSK frequency deviation
The sensitivity of the receiver is higher
for higher values of ∆fFSK
BR_Range0
BR_Range1
BR_Range2 and BR_Range3 are not
suitable for FSK operation
∆fFSK
20
20
50
50
kHz
kHz
S/N ratio to suppress inband noise
signals
ASK mode
FSK mode
SNRASK
SNRFSK
10
2
12
3
dB
dB
Dynamic range RSSI ampl.
Symbol
PRef_FSK
∆RRSSI
30
30
60
dB
27
4662B–RKE–10/04
Electrical Characteristics (Continued)
All parameters refer to GND, Tamb = -40°C to +105°C, VS = 4.5 V to 5.5 V, f0 = 433.92 MHz and f0 = 315 MHz, unless otherwise specified.
(VS = 5 V, Tamb = 25°C)
Parameters
Test Conditions
Lower cut-off frequency of the data
filter
1
f cu_DF = ----------------------------------------------------------2 × π × 30kΩ × CDEM
Recommended CDEM for best
performance
ASK mode
BR_Range0 (Default)
BR_Range1
BR_Range2
BR_Range3
CDEM
Recommended CDEM for best
performance
FSK mode
BR_Range0 (Default)
BR_Range1
BR_Range2 and BR_Range3 are not
suitable for FSK operation
CDEM
BR_Range0 (Default)
Maximum edge-to-edge time period of BR_Range1
the input data signal for full sensitivity BR_Range2
BR_Range3
Upper cut-off frequency data filter
Upper cut-off frequency programmable
in 4 ranges via a serial mode word
BR_Range0 (Default)
BR_Range1
BR_Range2
BR_Range3
BR_Range0 (Default)
Minimum edge-to-edge time period of BR_Range1
the input data signal for full sensitivity BR_Range2
BR_Range3
Symbol
Min.
Typ.
Max.
Unit
fcu_DF
0.11
0.16
0.20
kHz
39
22
12
8.2
nF
nF
nF
nF
27
15
nF
nF
tee_sig
fu
2.5
4.3
7.6
13.6
3.1
5.4
9.5
17.0
tee_sig
1000
560
320
180
µs
µs
µs
µs
3.7
6.5
11.4
20.4
kHz
kHz
kHz
kHz
270
156
89
50
µs
µs
µs
µs
dBm
(peak
level)
Reduced sensitivity
RSense connected from pin Sens to VS,
input matched according to Figure 4
Reduced sensitivity
RSense = 56 kΩ, fin = 433.92 MHz,
(VS = 5 V, Tamb = 25°C)
at B = 300 kHz
at B = 600 kHz
-71
-67
-76
-72
-81
-77
dBm
dBm
Reduced sensitivity
RSense = 100 kΩ, fin = 433.92 MHz
at B = 300 kHz
at B = 600 kHz
-80
-76
-85
-81
-90
-86
dBm
dBm
Reduced sensitivity
RSense = 56 kΩ, fin = 315 MHz
at B = 300 kHz
at B = 600 kHz
-72
-68
-77
-73
-82
-78
dBm
dBm
Reduced sensitivity
RSense = 100 kΩ, fin = 315 MHz
at B = 300 kHz
at B = 600 kHz
-81
-77
-86
-82
-91
-87
dBm
dBm
Reduced sensitivity variation over full
operating range
RSense = 56 kΩ
RSense = 100 kΩ
PRed = PRef_Red + DPRed
5
6
0
0
0
0
dB
dB
28
PRef_Red
∆PRed
U3741BM
4662B–RKE–10/04
U3741BM
Electrical Characteristics (Continued)
All parameters refer to GND, Tamb = -40°C to +105°C, VS = 4.5 V to 5.5 V, f0 = 433.92 MHz and f0 = 315 MHz, unless otherwise specified.
(VS = 5 V, Tamb = 25°C)
Parameters
Test Conditions
Symbol
Min.
Typ.
Max.
Unit
Values relative to
RSense = 56 kΩ
Reduced sensitivity variation for
different values of RSense
RSense = 56 kΩ
RSense = 68 kΩ
RSense = 82 kΩ
RSense = 100 kΩ
RSense = 120 kΩ
RSense = 150 kΩ
PRed = PRef_Red + ∆PRed
Threshold voltage for reset
0
-3.5
-6.0
-9.0
-11.0
-13.5
∆PRed
VThRESET
dB
dB
dB
dB
dB
dB
1.95
2.8
3.75
V
39
0.08
50
0.3
61
2.5
41
540
V
kΩ
µs
pF
pF
0.3
V
V
0.2 × VS
V
V
0.2 × VS
V
V
0.2 × VS
V
V
0.2 × VS
V
Digital Ports
Data output
- Saturation voltage LOW
- Internal pull-up resistor
- Maximum time constant
- Maximum capacitive load
Iol = 1 mA
t = CL (Rpup//RExt)
without ext. pull-up resistor
Rext = 5 kΩ
VOI
RPup
τ
CL
CL
POUT output
- Saturation voltage LOW
- Saturation voltage HIGH
IPOUT = 1 mA
IPOUT = -1 mA
VOl
VOh
0.08
VS - 0.3 V VS - 0.14V
FSK/ASK input
- Low-level input voltage
- High-level input voltage
FSK selected
ASK selected
VIl
VIh
0.8 × VS
ENABLE input
- Low-level input voltage
- High-level input voltage
Idle mode
Active mode
VIl
VIh
0.8 × VS
MODE input
- Low-level input voltage
- High-level input voltage
Division factor = 10
Division factor = 14
VIl
VIh
0.8 × VS
Test input must always be set to LOW
VIl
TEST input
- Low-level input voltage
29
4662B–RKE–10/04
Ordering Information
Extended Type Number
Package
Remarks
U3741BM-P2FL
SO20
2: IF bandwidth of 300 kHz, tube
U3741BM-P2FLG3
SO20
2: IF bandwidth of 300 kHz, taped and reeled
U3741BM-P3FL
SO20
3: IF bandwidth of 600 kHz, tube
U3741BM-P3FLG3
SO20
3: IF bandwidth of 600 kHz, taped and reeled
Package Information
9.15
8.65
Package SO20
Dimensions in mm
12.95
12.70
7.5
7.3
2.35
0.25
0.25
0.10
0.4
10.50
10.20
1.27
11.43
20
11
technical drawings
according to DIN
specifications
1
30
10
U3741BM
4662B–RKE–10/04
U3741BM
Revision History
Please note that the following page numbers referred to in this section refer to the
specific revision mentioned, not to this document.
Changes from Rev.
4662A - 06/03 to Rev.
4662B - 10/04
1. Put datasheet in a new template.
2. Heading rows at Table “Absolute Maximum Ratings” added.
3. Table “Ordering Information” on page 30 changed.
31
4662B–RKE–10/04
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4662B–RKE–10/04