nw6005 Integrated Device Technology, nw6005 Datasheet - Page 5

• Manufacturer Part Number: nw6005
• Description: Enhanced Type Ii Caller Id Decoder
• Manufacturer: Integrated Device Technology

DT-AS DETECTION ON EITHER TIP/RING OR HYBRID
RECEIVE PAIR
will affect the quality of the call waiting service. Even though the end
office has muted the far end party before and after it sends DT-AS, the
near end user who is to receive the FSK information may be still
talking. Therefore, the CPE must be able to detect DT-AS successfully
in the presence of near end speech. Furthermore, imitation of DT-AS
by speech will also affect the DT-AS detector, thus false detection may
be generated.
detection on the telephone hybrid receive pair instead of on Tip/Ring.
As the near end speech has been attenuated while the DT-AS level is
the same as on Tip/Ring, the DT-AS immunity is improved.
process of being defined by Bellcore, requests the CPE be capable of
detecting DT-AS when the line is off-hook, although the CPE itself may
be on-hook. Under some conditions, an on-hook CPE may send an
acknowledgment to the end office. Also, the on-hook CPE’s capability
of detecting DT-AS enables the call logs between on and off-hook
CPEs to be maintained synchronous. In this way, when all off-hook
CPEs are MEI compatible and DT-AS is received, one of the CPEs will
send the acknowledgment signal and all CPEs will receive FSK.
receive pair, the CPE can not detect DT-AS when it is on-hook. When
the CPE is on-hook, either the hybrid is non-functional or the signal
level is severely attenuated. Thus, an on-hook CPE must be able to
detect DT-AS from Tip/Ring.
be connected both to Tip/Ring and to the Hybrid Receive pairs. Both
connection can be differential or single-ended. FSK demodulation is
implemented only on Tip/Ring, while DT-AS detection can be on either
Tip/Ring or Hybrid Receive. Tip/Ring DT-AS detection is required for
MEI and BT’s on-hook CLIP.
detection only, its gain can always be adjusted specifically for the DT-
AS signal.
NW6005 ENHANCED TYPE II CALLER ID DECODER
In off-hook services, the detection of Dual Tone Alert Signal (DT-AS)
To achieve better DT-AS detection quality, a method is to put DT-AS
A CPE capability called Multiple Extension Interworking(MEI), in
Therefore, if the DT-AS detector is connected only to the hybrid
The NW6005 provides two input OP amps via which the device can
It should be noted here that as the Hybrid OP amp is for DT-AS
5
BLOCK DESCRIPTION
of three major functional blocks: Analog Input Circuit, Dual Tone Alert
Signal Detection, and FSK Demodulation.
ANALOG INPUT CIRCUIT
which is comprised of two OP amps and a bias source (VREF). VREF
is the output of a low impedance voltage source used to bias the input
OP amp, and is typically equal to VCC/2. The Tip/Ring OP amp
(IN1+, IN1-, GS1 pins) is for connecting to Tip and Ring, while the
Hybrid OP amp (IN2+, IN2-, GS2 pins) is for connecting to Hybrid
Receive Pair. The gain adjustable OP amps are also used to select
the input gain by connecting a feedback resistor between GS and the
IN- pin. Fig. 3 shows the differential input configuration. In single-
ended configuration, the gain adjustable OP amp is connected as
shown in Fig. 4.
The NW6005 requires a 3.579545 MHz system clock and consists
The input signal is processed by the Analog Input Circuit block,
Differential Input Amplifier
C1=C2
R1=R2 (For unity gain R5=R2)
R3=(R4R5)/(R4+R5)
Figure 4. Single-ended Input Gain Control Circuit
Figure 3. Differential Input Gain Control Circuit
Voltage Gain
Av = Rf / Rin
C1
C2
C
R1
R2
INDUSTRIAL TEMPERATURE RANGE
Rin
R3
Voltage Gain
Av = R5/R2
Input Impedance
Zin =2 R1
R4
Rf
R5
²
+ (1/
IN+
IN-
GS
V
V
IN+
IN-
GS
REF
REF
NW6005
NW6005
C)²