ML3356
Wideband FSK Receiver
Legacy Device:
Motorola MC3356
The ML3356 includes Oscillator, Mixer, Limiting IF Amplifier,
Quadrature Detector, Audio Buffer, Squelch, Meter Drive, Squelch
Status output, and Data Shaper comparator. The ML3356 is designed
for use in digital data communciations equipment.
• Data Rates up to 500 kilobaud
• Excellent Sensitivity: – 3 dB Limiting Sensitivity
30 µVrms @ 100 MHz
• Highly Versatile, Full Function Device, yet Few External Parts
are Required
• Down Converter Can be Used Independently — Similar to NE602
• Operating Temperature Range TA = –40° to +85°C
SO 20W = -6P
PLASTIC PACKAGE
CASE 751D
(SO–20L)
PACKAGE
P DIP 20
SO 20W
MOTOROLA
MC3356P
MC3356DW
LANSDALE
ML3356RP
ML3356-6P
P DIP 20 = RP
PLASTIC PACKAGE
CASE 738
Note:
Lansdale lead free (Pb) product, as it
becomes available, will be identified by a part
number prefix change from
ML
to
MLE.
Figure 1. Representative Block Diagram
RF
VCC
RF
Ground
1
2
3
4
5
Ceramic
Filter
6
7
8
9
10
Quadrature Detector
Tank
20
19
18
Mixer
Data Shaping
Comparator
+
–
17
16
Squelch
Status
Hysteresis
RF
Input
Ground
PIN CONNECTIONS
RF Ground 1
OSC Emitter 2
Data
Output
VCC
OSC Collector 3
RF VCC 4
Mixer Output 5
IF VCC 6
Limiter Input 7
Limiter Bias 8
13
12
11
Squelch
Adjust
(Meter)
Limiter Bias 9
Quad Bias 10
20 RF Input
19 Ground
18 Data Output
17 + Comparator
16 – Comparator
15 Squelch Status
14 Squelch Control
13 Buffered Output
12 Demodulator
Filter
11 Quad Input
OSC
Comparator –
+
Meter Current
Limiter
15
14
Buffer
VCC
Page 1 of 9
www.lansdale.com
Issue A
ML3356
MAXIMUM RATINGS
Rating
Power Supply Voltage
Operating Power Supply Voltage Range (Pins 6, 10)
Operating RF Supply Voltage Range (Pin 4)
Junction Temperature
Operating Ambient Temperature Range
Storage Temperature Range
Power Dissipation, Package Rating
Symbol
VCC(max)
VCC
RF VCC
TJ
TA
Tstg
PD
Value
15
3.0 to 9.0
3.0 to 12.0
150
– 40 to + 85
– 65 to + 150
1.25
Unit
Vdc
Vdc
Vdc
°C
°C
°C
W
LANSDALE Semiconductor, Inc.
ELECTRICAL CHARACTERISTICS
(VCC = 5.0 Vdc, fo = 100 MHz, fosc = 110.7 MHz,
∆f
=
±75
kHz, fmod = 1.0 kHz, 50
Ω
source,
TA = 25°C, test circuit of Figure 2, unless otherwise noted.)
Characteristics
Drain Current Total, RF VCC and VCC
Input for – 3 dB limiting
Input for 50 dB quieting
+
(
SN N
)
Min
–
–
–
2.5
–
–
–
–
–
–
–
–
Typ
20
30
60
–
260
5.0
0.2 to 150
0.2 to 50
50
0.5
7.0
0.8
Max
25
–
–
–
–
–
–
–
–
–
–
–
Unit
mAdc
µVrms
µVrms
v/v
Ω
pF
MHz
MHz
dB
Vrms
µA/dB
Vdc
Mixer Voltage Gain, Pin 20 to Pin 5
Mixer Input Resistance, 100 MHz
Mixer Input Capacitance, 100 MHz
Mixer/Oscillator Frequency Range (Note 1)
IF/Quadrature Detector Frequency Range (Note 1)
AM Rejection (30% AM, RF Vin = 1.0 mVrms)
Demodulator Output, Pin 13
Meter Drive
Squelch Threshold
NOTE:
1. Not taken in Test Circuit of Figure 2; new component values required.
Figure 2. Test Circuit
Squelch
Status
Data Output
130 k
3.3 k
18 k
3.0 k
0.01
390 k
20
RF Input
19
Ground
18
Data
Output
17
Comp(+)
16
Comp(–)
3.3 k
15
Squelch
Status
14
Squelch
Control
0.1
470
pF
13
Demod
Out
12
Demod
Filter
18 k
11
Quad
Input
Demod
Out
47 k
100 MHz
RF Input
10 k
0.01
51
47 k
L1 – 110.7 MHz, 0.4
µH
L1 –
7T #22, 3/16 Form
L1 –
w/slug & can
L2 – 10.7 MHz, 1.5
µH
L2 –
20T #30, 3/16 Form
L2 –
w/slug & can
T1 – muRata
T1 –
SFE10.7 MA5–Z
or
KYOCERA
T1 –
KBF10.7MN–MA
150 pF
L2
RF
Gnd
1
OSC
EM.
2
5.6 pF
15 pF
L1
330
OSC
COL.
3
RF
VCC
4
Mixer
Out
5
0.01
330
VCC
5 Vdc
T1
0.01
VCC
6
Limiter
Input
7
Limiter
Bias
8
0.01
Limiter
Bias
9
Quad
Bias
10
Page 2 of 9
www.lansdale.com
Issue A
ML3356
LANSDALE Semiconductor, Inc.
Figure 3. Output Components of Signal,
Noise, and Distortion
10
S+N+D
RELATIVE OUTPUT (dB)
–10
–20
–30
N+D
–40
–50
–60
0.01
0.1
INPUT (mVrms)
N
fO = 100 MHz
fm = 1.0 kHz
∆f
=
±
75 kHz
METER CURRENT, PIN 14 (
µ
A)
0
700
600
500
400
300
200
100
Figure 4. Meter Current versus Signal Input
1.0
10
0
0.010
0.1
1.0
10
PIN 20 INPUT (mVrms)
100
1000
GENERAL DESCRIPTION
This device is intended for single and double conversion
VHF receiver systems, primarily for FSK data transmission up
to 500 K baud (250 kHz). It contains an oscillator, mixer, lim-
iting IF, quadrature detector, signal strength meter drive, and
data shaping amplifier.
The oscillator is a common base Colpitts type which can be
crystal controlled, as shown in Figure 1, or L–C controlled as
shown in figure 8. At higher VCC, it has been operated as
high as 200 MHz. A mixer/oscillator voltage gain of 2 up to
approximately 150 MHz, is readily achievable.
The mixer functions well from an input signal of 10 µVrms,
below which the squelch is unpredictable, up to about 10
mVrms, before any evidence of overload. Operation up to 1.0
Vrms input is permitted, but non–linearity of the meter output
is incurred, and some oscillator pulling is suspected. The AM
rejection above 10 mVrms is degraded.
The limiting IF is a high frequency type, capable of being
operated up to 50 MHz. It is expected to be used at 10.7 MHz
in most cases, due to the availability of standard ceramic res-
onators. The quadrature detector is internally coupled to the
IF, and a 5.0 pF quadrature capacitor is internally provided.
The –3dB limiting sensitivity of the IF itself is approximately
50 µV (at Pin 7), and the IF can accept signals up to 1.0 Vrms
without distortion or change of detector quiescent DC level.
The IF is unusual in that each of the last 5 stages of the 6
state limiter contains a signal strength sensitive, current sink-
ing device. These are parallel connected and buffered to pro-
duce a signal strength meter drive which is fairly linear for IF
input signals of 10 µV to 100 mVrms (see Figure 4).
A simple squelch arrangement is provided whereby the
meter current flowing through the meter load resistance flips a
comparator at about 0.8 Vdc above ground. The signal
strength at which this occurs can be adjusted by changing the
meter load resistor. The comparator (+) input and output are
available to permit control of hysteresis. Good positive action
can be obtained for IF input signals of above 30 µVrms. The
130 kΩ resistor shown in the test circuit provides a small
amount of hysteresis. Its connection between the 3.3k resistor
to ground and the 3.0 k pot, permits adjustment of squelch
level without changing the amount of hysteresis.
The squelch is internally connected to both the quadrature
detector and the data shaper. The quadrature detector output,
when squelched, goes to a DC level approximately equal to the
zero signal level unsquelched. The squelch causes the data
shaper to produce a high (VCC) output.
The data shaper is a complete ‘‘floating’’ comparator, with
back to back diodes across its inputs. The output of the quad-
rature detector can be fed directly to either input of this ampli-
fier to produce an output that is either at VCC or VEE,
depending upon the received frequency. The impedance of the
biasing can be varied to produce an amplifier which “follows”
frequency detuning to some degree, to prevent data pulse
width changes.
When the data shaper is driven directly from the demodula-
tor output, Pin 13, there may be distortion at Pin 13 due to the
diodes, but this is not important in the data application. A use-
ful note in relating high/low input frequency to logic state: low
IF frequency corresponds to low demodulator output. If the
oscillator is above the incoming RF frequency, then high RF
frequency will produce a logic low (input to (+) input of Data
Shaper as shown in Figures 1 and 2).
APPLICATION NOTES
The ML3356 is a high frequency/high gain receiver that
requires following certain layout techniques in designing a sta-
ble circuit configuration. The objective is to minimize or elim-
inate, if possible, any unwanted feedback.
Page
3
of 9
www.lansdale.com
Issue A
ML3356
LANSDALE Semiconductor, Inc.
Legacy Applications Information
Figure 5. Application with Fixed Bias on Data Shaper
Data Out
5.0 V
18 k
130 k
RF In
1:2
0.01
10 k
10 k
390 k
20
RF Input
19
Ground
18
Data
Output
17
Comp(+)
16
Comp(–)
3.3 k
15
Squelch
Status
14
Squelch
Control
13
Demod
Out
3.0 k
0.1
470
pF
Car. Det. Out
0 V or 4.0 V
3.3 k
15 k
18 k
12
Demod
Filter
11
Quad
Input
ML3356
150 pF
RF
Gnd
1
5.0 V
15 pF
+ 5.0 to + 12 V
OSC
EM.
2
5.6 pF
OSC
COL.
3
fO
RF
VCC
4
Mixer
Out
5
0.01
VCC
6
Limiter
Input
7
0.1
330
0.01
Limiter
Bias
8
Limiter
Bias
9
0.01
0.01
Quad
Bias
10
Bead
0.01
4.0 V
180
82
330
Bead
0.1
Cer. Fil.
10.7 MHz
APPLICATION NOTES (continued)
Shielding, which includes the placement of input and output
components, is important in minimizing electrostatic or elec-
tromagnetic coupling. The ML3356 has its pin connections
such that the circuit designer can place the critical input and
output circuits on opposite ends of the chip. Shielding is nor-
mally required for inductors in tuned circuits.
The ML3356 has a separate VCC and ground for the RF and
IF sections which allows good external circuit isolation by
minimizing common ground paths.
Note that the circuits of Figures 1 and 2 have RF, Oscillator,
and IF circuits predominantly referenced to the plus supply
rails. Figure 5, on the other hand, shows a suitable means of
ground referencing. The two methods produce identical results
when carefully executed. It is important to treat Pin 19 as a
ground node for either approach. The RF input should be
‘‘grounded’’ to Pin 1 and then the input and the mixer/oscilla-
tor grounds (or RF VCC bypasses) should be connected by a
low inductance path to Pin 19. IF and detector sections should
also have their bypasses returned by a separate path to Pin 19.
VCC and RF VCC can be decoupled to minimize feedback,
although the configuration of Figure 2 shows a successful
implementation on a common 5.0 V supply. Once again, the
message is: define a supply node and a ground node and return
each section to those nodes by separate, low impedance paths.
The test circuit of Figure 2 has a 3 dB limiting level of 30
µV which can be lowered 6 db by a 1:2 untuned transformer at
the input as shown in Figures 5 and 6. For applications that
require additional sensitivity, an RF amplifier can be added,
but with no greater than 20 db gain. This will give a 2.0 to 2.5
µV sensitivity and any additional gain will reduce receiver
dynamic range without improving its sensitivity. Although the
test circuit operates at 5.0 V, the mixer/oscillator optimum per-
formance is at 8.0 V to 12 V. A minimum of 8.0 V is recom-
mended in high frequency applications (above 150 MHz), or in
PLL applications where the oscillator drives a prescaler.
Page 4 of 9
www.lansdale.com
Issue A
ML3356
LANSDALE Semiconductor, Inc.
Legacy Applications Information
Figure 6. Application with Self–Adjusting Bias on Data Shaper
Data
Out
5.0 V
Car. Det. Out
0 V or 4.0 V
130 k
3.3 k
1
47 k
RF In
1:2
470 k
20
RF Input
19
Ground
18
Data
Output
0.01
10 k
470 pF
17
Comp(+)
16
15
47 k
0.1
3.3 k
0.1
14
Squelch
Control
13
Demod
Out
470
pF
15 k
18 k
12
Demod
Filter
11
Quad
Input
f = 10.7
150 pF
1.5
µH
Comp(–) Squelch
Status
APPLICATION NOTES (continued)
Depending on the external circuit, inverted or noninverted
data is available at Pin 18. Inverted data makes the higher fre-
quency in the FSK signal a “one” when the local oscillator is
above the incoming RF. Figure 5 schematic shows the com-
parator with hysteresis. In this circuit the DC reference volt-
age at Pin 17 is about the same as the demodulated output
voltage (Pin 13) when no signal is present. This type circuit is
preferred for systems where the data rates can drop to zero.
Some systems have a low frequency limit on the data rate,
such as systems using the MC3850 ACIA that has a start or
stop bit. This defines the low frequency limit that can appear
in the data stream. Figure 5 circuit can then be changed to a
circuit configuration as shown in Figure 6. In Figure 6 the ref-
erence voltage for the comparator is derived from the demodu-
lator output through a low pass circuit where
τ
is much lower
than the lowest frequency data rate. This and similar circuits
will compensate for small tuning changes (or drift) in the
quadrature detector.
Squelch status (Pin 15) goes high (squelch off) when the
input signal becomes greater than some preset level set by the
resistance between Pin 14 and ground. Hysteresis is added to
the circuit externally by the resistance from Pin 14 to Pin 15.
Page 5 of 9
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Issue A
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