SA614AD/01,112 NXP Semiconductors, SA614AD/01,112 Datasheet - Page 10

• Manufacturer Part Number: SA614AD/01,112
• Description: IC FM IF SYSTEM LOW PWR 16-SOIC
• Manufacturer: NXP Semiconductors

Specifications of SA614AD/01,112

• Package / Case: 16-SOIC (0.154", 3.90mm Width)
• Function: FM IF System
• Frequency: 25MHz
• Rf Type: Cellular, ASK, FSK
• Secondary Attributes: RSSI Equipped
• Mounting Style: SMD/SMT
• Operating Supply Voltage: 6 V
• Maximum Operating Temperature: + 85 C
• Minimum Operating Temperature: - 40 C
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant, Lead free / RoHS Compliant
• Other names: 935275282112; SA614AD/01; SA614AD/01

V
Philips Semiconductors
From the above equation, the phase shift between nodes 1 and 2, or
the phase across C
It is notable that at
line with a slope of
The signal V
If V
Multiplying the two signals in the mixer, and
V
after low pass filtering
Which is discriminated FM output. (Note that
frequency from the carrier
Ref. Krauss, Raab, Bastian; Solid State Radio Eng.; Wiley, 1980, p.
311. Example: At 455kHz IF, with +5kHz FM deviation. The
maximum normalized frequency will be
Go to the f vs. normalized frequency curves (Figure 12) and draw a
vertical straight line at
The curves with Q = 100, Q = 40 are not linear, but Q = 20 and less
shows better linearity for this application. Too small Q decreases
the amplitude of the discriminated FM signal. (Eq. 6)
Q = 20
The internal R of the 614A is 40k. From Eq. 1c, and then 1b, it
results that
C
1997 Nov 07
Figure 12 is the plot of
low pass filtering yields:
2
For
OUT
IN
2
P
=
1
Low power FM IF system
V
IN
and the response is close to a straight
+ C
–
= 1.01.
OUT
V
= A Sin
V
2Q
2Q
S
O
O
Sin
Sin
1
2Q
455 +5kHz
= 174pF and L = 0.7mH.
=
= 1
1
1
-
= A
1
1
1
2
2
O
455
V
2
<<
IN
would have a phase shift of
Sin
A
A
t +
t +
1
with respect to the V
t
2
2
=
=
Cos
Sin
2
S
2
2
t
V
t
g
2Q
=
will be:
-1
(
= 1.010 or 0.990
O
–
–
2Q
= A
1
1
vs.
2
2Q
2Q
(
1
, the phase shift is
1
=
1
)
1
1
–
–
1
1
1
( )
1
.
2Q
( )
Q
2Q
+
1
1
1
1
1
1
1
1
1
IN
2
)
.
(2)
(3)
(4)
(5)
(6)
is the deviation
Choose a
10
A more exact analysis including the source resistance of the
previous stage shows that there is a series and a parallel resonance
in the phase detector tank. To make the parallel and series
resonances close, and to get maximum attenuation of higher
harmonics at 455kHz IF, we have found that a C
164pF (commercial values of 150pF or 180pF may be practical), will
give the best results. A variable inductor which can be adjusted
around 0.7mH should be chosen and optimized for minimum
distortion. (For 10.7MHz, a value of C
Audio Outputs
Two audio outputs are provided. Both are PNP current-to-voltage
converters with 55k
is always active to permit the use of signaling tones in systems such
as cellular radio. The other output can be muted with 70dB typical
attenuation. The two outputs have an internal 180 phase
difference.
The nominal frequency response of the audio outputs is 300kHz.
this response can be increased with the addition of external
resistors from the output pins to ground in parallel with the internal
55k resistors, thus lowering the output time constant. Singe the
output structure is a current-to-voltage converter (current is driven
into the resistance, creating a voltage drop), adding external parallel
resistance also has the effect of lowering the output audio amplitude
and DC level.
This technique of audio bandwidth expansion can be effective in
many applications such as SCA receivers and data transceivers.
Because the two outputs have a 180 phase relationship, FSK
demodulation can be accomplished by applying the two output
differentially across the inputs of an op amp or comparator. Once
the threshold of the reference frequency (or “no-signal” condition)
has been established, the two outputs will shift in opposite directions
(higher or lower output voltage) as the input frequency shifts. The
output of the comparator will be logic output. The choice of op amp
or comparator will depend on the data rate. With high IF frequency
(10MHz and above), and wide IF bandwidth (L/C filters) data rates in
excess of 4Mbaud are possible.
RSSI
The “received signal strength indicator”, or RSSI, of the SA614A
demonstrates monotonic logarithmic output over a range of 90dB.
The signal strength output is derived from the summed stage
currents in the limiting amplifiers. It is essentially independent of the
IF frequency. Thus, unfiltered signals at the limiter inputs, spurious
products, or regenerated signals will manifest themselves as RSSI
outputs. An RSSI output of greater than 250mV with no signal (or a
very small signal) applied, is an indication of possible regeneration
or oscillation.
In order to achieve optimum RSSI linearity, there must be a 12dB
insertion loss between the first and second limiting amplifiers. With
a typical 455kHz ceramic filter, there is a nominal 4dB insertion loss
in the filter. An additional 6dB is lost in the interface between the
filter and the input of the second limiter. A small amount of
additional loss must be introduced with a typical ceramic filter. In the
test circuit used for cellular radio applications (Figure 5) the optimum
linearity was achieved with a 5.1k
first limiter (Pin 14) to the input of the interstage filter. With this
resistor from Pin 14 to the filter, sensitivity of 0.25 V for 12dB
SINAD was achieved. With the 3.6k
nominal internal loads. The unmuted output
resistor from the output of the
S
resistor, sensitivity was
= 1pF is recommended.)
Product specification
S
= 10pF and C
SA614A
P
=