Philips SA615 User Manual
Page 8
Philips Semiconductors
Product specification
SA615
High performance low power mixer FM IF system
1997 Nov 07
8
RF GENERATOR
SA615 DEM0–BOARD
RSSI
AUDIO
DATA
C–MESSAGE
HP339A DISTORTION
ANALYZER
SCOPE
DC VOLTMETER
V
CC
(+6)
45MHz
SR00345
Figure 5. SA615 Application Circuit Test Set Up
NOTES:
1. C-message: The C-message filter has a peak gain of 100 for accurate measurements. Without the gain, the measurements may be
affected by the noise of the scope and HP339 analyzer.
2. Ceramic filters: The ceramic filters can be 30kHz SFG455A3s made by Murata which have 30kHz IF bandwidth (they come in blue), or
16kHz CFU455Ds, also made by Murata (they come in black). All of our specifications and testing are done with the more wideband filter.
3. RF generator: Set your RF generator at 45.000MHz, use a 1kHz modulation frequency and a 6kHz deviation if you use 16kHz filters, or
8kHz if you use 30kHz filters.
4. Sensitivity: The measured typical sensitivity for 12dB SINAD should be 0.22
µ
V or –120dBm at the RF input.
5. Layout: The layout is very critical in the performance of the receiver. We highly recommend our demo board layout.
6. RSSI: The smallest RSSI voltage (i.e., when no RF input is present and the input is terminated) is a measure of the quality of the layout and
design. If the lowest RSSI voltage is 250mV or higher, it means the receiver is in regenerative mode. In that case, the receiver sensitivity
will be worse than expected.
7. Supply bypass and shielding: All of the inductors, the quad tank, and their shield must be grounded. A 10–15
µ
F or higher value tantalum
capacitor on the supply line is essential. A low frequency ESR screening test on this capacitor will ensure consistent good sensitivity in
production. A 0.1
µ
F bypass capacitor on the supply pin, and grounded near the 44.545MHz oscillator improves sensitivity by 2–3dB.
8. R5 can be used to bias the oscillator transistor at a higher current for operation above 45MHz. Recommended value is 22k
Ω
, but should not
be below 10k
Ω
.