Obsolescence Notice
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replacement product lists, please visit
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PURPOSES ONLY AND IS NOT
RECOMMENDED FOR NEW DESIGNS
2471-3.1
SL6659
LOW POWER IF/AF CIRCUIT (WITH RSSI) FOR FM RADIO
The SL6659 is a complete single chip mixer, IF amplifier and
detector for FM cellular radio, cordless telephones and low
power radio applications. It features an exceptionally stable
RSSI (Received Signal Strength Indicator) output using a
unique system of detection. Supply current is less than 2mA
from a supply voltage in the range 2·5V to 7·5V.
FEATURES
s
Low Power Consumption (1·5mA)
s
Single Chip Solution
s
Guaranteed 200MHz Operation
s
Exceptionally Stable RSSI
APPLICATIONS
s
Cellular Radio Telephones
MP16
Fig. 1 Pin connections – top view
s
Cordless Telephones
ORDERING INFORMATION
SL6659 NA MP
– Miniature plastic DIL package
SL6659 NA MPTD
- As above, supplied on tape and reel
QUICK REFERENCE DATA
s
Supply Voltage: 2·5V to 7·5V
s
Sensitivity: 3µV
s
Co-channel Rejection: 7dB
Fig. 2 Block diagram
SL6659
ABSOLUTE MAXIMUM RATINGS
Supply voltage
Storage temperature
Mixer input
55°C to
8V
150°C
1Vrms
NOTE: This device has static sensitive inputs, sensitivity
typically measured as 500V using MIL-STD-883 method
3015. Therefore, ESD handling precautions are essential to
avoid degradation of performance or permanent damage of
this device.
ELECTRICAL CHARACTERISTICS
The characteristics are guaranteed over the following condltions, unless otherwise stated:
V
CC
= 2·5V to 7·5V, T
AMB
= 30°C to 85°C, IF = 455kHz, RF = 50MHz, Quad Coil working Q = 30
Characteristic
Overall
Supply current
Sensitivity
AM rejection
V
BIAS
Co-channel rejection
Mixer
RF input impedance
LO input impedance
LO input bias
Mixer gain
3rd order input intercept
LO input level
LO frequency
IF Amplifier
Gain
Frequency
Differential input impedance
Detector
Audio output level
Ultimate S/N ratio
THD
Output impedance
RSSI Output (T
AMB
=
Output current
25°C)
50
0·9
70
25
80
1·5
µA
µA
µA/dB
dB
No input pin13
Pin 13 = 2·5mV
See Note 1
See Note 1
Value
Min.
Typ.
1·5
5
3
40
1·2
7
Max.
2·0
Units
Conditions
1·0
1·4
mA
µV
µV
dB
V
dB
20dB SINAD
12dB SINAD
RF input
,500µV
T
AMB
= 25°C
See Note 2
1
2
5
15
10
180
200
300
kΩ
kΩ
µA
dB
dBm
mV
MHz
At V
BIAS
R
LOAD
= 1.5kΩ
455
90
1500
20
dB
kHz
kΩ
75
60
0·5
40
125
5
mV
dB
%
kΩ
5mV into pin 13
Current change
Linear dynamic range
1·22
NOTES
1. The RSSI output is 100% dynamically tested at 5V and 20°C over a 70dB range. First the input to pin 13 is set to 2·5mV and the RSSI current
recorded. Then for each step of 10dB from 40 to 30db, the current is measured. The current change in each step must meet the specified
figure for current change. The RSSI output is guaranteed monotonic and free from discontinuities over this range.
2. Co-channel rejection is measured by applying a 3kHz deviation, 1kHz modulated signal at an input level to give a 20dB SINAD ratio. Then
a 3kHz deviation 400Hz modulated slgnal on the same frequency is also applied and its level increased to degrade the SINAD to 14dB.
2
SL6659
Fig. 3 Internal schematic
GENERAL DESCRIPTION
The SL6659 is a very low power, high performance integrated
circuit intended for IF amplification and demodulation in FM radio
receivers. It comprises:
q
A mixer stage for use up to 200MHz
q
A limiting amplifier operating up to 1·5MHz
q
A quadrature detector with AF output
q
An RSSI (Received Signal Strength Indicator)
ceramic filter. Because of the high gain, pins 11 and 12 must be
adequately bypassed.
Detector
A conventional quadrature detector providing audio output is fed
internally from the IF amplifier; the quadrature input is fed externally
using an appropriate capacitor and phase shift network.
output
RSSI Output
The RSSI output is a current source with value proportional to the
logarithm of the IF signal amplitude. There is a small residual current
due to noise within the amplifier (and mixer) but beyond this point
there is a measured and guaranteed 70dB dynamic range. The
typical range extends to 92dB, independent of frequency, and with
exceptionally good temperature and supply voltage stability.
Mixer
The Mixer is single balanced with an active load. Gain is set
externally by the load resistor, although the value is normally
determined by that required for matching into the ceramic filter. It is
possible to use a tuned circuit but an increase in mixer gain will result
in a corresponding reduction of the mixer input intercept point.
The RF input is a diode-biased transistor with a bias current of
typically 300µA. The LO input is differential but would normally be
driven single-ended. Special care should be taken to avoid acciden-
tal overload of the local oscillator input.
Supply Voltage
The SL6659 will operate reliably trom 2·5V to 7·5V. The supply
line must be decoupled with 470nF using short leads.
IF Amplifier
The limiting amplifier is capable of operation to at least 1MHz and
the input impedance is set by an external resistor to match the
Internal Bias Voltage
The internal band-gap reference must be externally decoupled.
It can be used as an external reference but must not be loaded
heavily; the output impedance is typically 14Ω
..
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