PSB4860HV4.1 Lantiq, PSB4860HV4.1 Datasheet - Page 51

• Manufacturer Part Number: PSB4860HV4.1
• Manufacturer: Lantiq

Specifications of PSB4860HV4.1

• Lead Free Status / Rohs Status: Supplier Unconfirmed

2.1.8
The universal tone detector can be used instead of the CPT detector to detect special
tones which are not covered by the standard CPT band-pass. Figure 27 shows the
functional block diagram.
A
Figure 27 Universal Tone Detector - Block Diagram
Initially, the input signal is filtered by a programmable band-pass (center frequency CF
and band width BW). Both the in-band signal (upper path) and the out-of-band signal are
determined (lower path) and the absolute value is calculated. Both signals are
furthermore filtered by a limiter and a low-pass. All signal samples (absolute values)
below a programmable limit LIM are set to zero and all other signal samples are
diminished by LIM. The purpose of the limiter is to increase noise robustness. After the
limiter stages both signals are filtered by a fixed low pass.
The evaluation logic block determines when to set and when to reset the status bit
STATUS:UTD.
The status bit will be set if both of the following conditions hold for at least time TTONE
without breaks exceeding time TB1:
1. the in-band signal exceeds a programmable level LEV
2. the difference of the in-band and the out-of-band signal exceeds DELTA
The status bit will be reset if at least one of these conditions is violated by at least time
TGAP without breaks exceeding TB2.
The times TB1 and TB2 help to reduce the effects of sporadic dropouts.
Example:
TTONE is set to 100 ms and TB1 is set to 4 ms.
Data Sheet
I
1
Universal Tone Detector
Programmable
Band-pass
|x|
|x|
51
Limit
Limit
LP
LP
Evaluation
Logic
PSB 4860
2000-01-14
SCI