z02201 ZiLOG Semiconductor, z02201 Datasheet - Page 74

• Manufacturer Part Number: z02201
• Description: Z02201 V.22bis Data Pump With Integrated Afe
• Manufacturer: ZiLOG Semiconductor

Example DAA
PS000904-0107
Figure 15
transformer, T1, couples the primary (line) and secondary (modem) sides, while
providing high voltage isolation. This wet transformer (allowing DC current)
simplifies the circuit, while reducing the cost of the DAA.
On the Secondary side, the transmit (TxA+ and TxA–) and receive (RxA+ and
RxA–) are combined in the 4-wire to 2-wire hybrid circuit. This hybrid can be either
passive or active. The more complex active hybrid allows operation to lower signal
levels. It cancels out most of the transmit signal from the receive
signal.
On the Primary side, the off-hook relay switches the phone line between a local
handset (PHONE) or the modem. The ring detect circuit consists of DC blocking
capacitor C4, current limiting resistor R2, zener diodes CR3 and CR4, optocoupler
U3, and its reverse protection diode D3. Protection elements RV1, F1, C1, and C2
(and transformer T1’s isolation) provide higher voltage capability for approval in
some foreign markets. C1 and C2, for example, may must be replaced by Metal
Oxide Varistors (MOV’s) or Gas Discharge Tubes (GDTs). The shunt relay
reduces the DAA impedance during pulse dialing. This operation is required for
some country regulations
indicates an example DAA configuration for North America. Isolation
V.22BIS Data Pump with Integrated AFE
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