SA614A Philips Semiconductors (Acquired by NXP), SA614A Datasheet - Page 11

• Manufacturer Part Number: SA614A
• Description: SA614A; Low Power FM if System
• Manufacturer: Philips Semiconductors (Acquired by NXP)

Philips Semiconductors
optimized at 0.22 V for 12dB SINAD with minor change in the RSSI
linearity.
Any application which requires optimized RSSI linearity, such as
spectrum analyzers, cellular radio, and certain types of telemetry,
will require careful attention to limiter interstage component
selection. This will be especially true with high IF frequencies which
require insertion loss or impedance reduction for stability.
At low frequencies the RSSI makes an excellent logarithmic AC
voltmeter.
For data applications the RSSI is effective as an amplitude shift
keyed (ASK) data slicer. If a comparator is applied to the RSSI and
the threshold set slightly above the no signal level, when an in-band
signal is received the comparator will be sliced. Unlike FSK
1997 Nov 07
Low power FM IF system
200
175
150
125
100
75
50
25
0
0.95
Q = 10
Q = 20
Figure 12. Phase vs Normalized IF Frequency
0.975
Q = 100
Q = 80
Q = 60
11
demodulation, the maximum data rate is somewhat limited. An
internal capacitor limits the RSSI frequency response to about
100kHz. At high data rates the rise and fall times will not be
symmetrical.
The RSSI output is a current-to-voltage converter similar to the
audio outputs. However, an external resistor is required. With a
91k
the input amplitude.
Additional Circuitry
Internal to the SA614A are voltage and current regulators which
have been temperature compensated to maintain the performance
of the device over a wide temperature range. These regulators are
not accessible to the user.
1.0
resistor, the output characteristic is 0.5V for a 10dB change in
I
1
1.025
I
Product specification
SA614A
SR00334
1.05