SA58640 Datasheet, PDF (9/16 Pages) NXP Semiconductors – Low-voltage mixer FM IF system

Philips Semiconductors
13. Test information
SA58640
Low-voltage mixer FM IF system
RF GENERATOR
45 MHz
V_CC (+3)
SA58640 DEMOBOARD
RSSI AUDIO
DC VOLTMETER
DE-EMPHASIS
FILTER
C–MESSAGE
SCOPE
HP339A DISTORTION
ANALYZER
002aab127
Fig 4. Application circuit test setup
The following list items 1 through 8 apply to Figure 4:
1. The C-message and de-emphasis filter combination has a peak gain of 10 for
accurate measurements. Without the gain, the measurements may be affected by the
noise of the scope and HP339A analyzer. The de-emphasis filter has a fixed
6 dB/Octave slope between 300 Hz and 3 kHz.
2. The ceramic filters can be 30 kHz SFG455A3s made by Murata which have 30 kHz IF
bandwidth (they come in blue), or 16 kHz CFU455Ds, also made by Murata (they
come in black). All specifications and testing are done with the wideband filter.
3. Set your RF generator at 45.000 MHz, use a 1 kHz modulation frequency and a 6 kHz
deviation if you use 16 kHz filters, or 8 kHz if you use 30 kHz filters.
4. The measured typical sensitivity for 12 dB SINAD should be 0.45 PV or 114 dBm at
the RF input.
5. The layout is very critical in the performance of the receiver. We highly recommend
our demo board layout.
6. 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 500 mV or higher, it means the receiver is in regenerative mode. In that
case, the receiver sensitivity will be worse than expected.
7. All of the inductors, the quad tank, and their shield must be grounded. A 10 PF to
15 PF 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 PF bypass capacitor on the supply pin, and grounded near the
44.545 MHz oscillator improves sensitivity by 2 dB to 3 dB.
8. R5 can be used to bias the oscillator transistor at a higher current for operation above
45 MHz. Recommended value is 22 k:, but should not be below 10 k:.
9397 750 14161
Objective data sheet
Rev. 01 — 1 November 2004
© Koninklijke Philips Electronics N.V. 2004. All rights reserved.
9 of 16