CH1817

Features:

`Low Profile, Ultra small size: 1.0" x 1.0" x 0.35"
`Complete DAA function
`Ring detection
`Built-in 2-wire to 4-wire conversion
`Lightweight
`Multimedia compatible
`+5V operation
`1000 VAC isolation
`800 Volt surge protection
`V.32bis/14,400bps, applications
`UL1459 recognized
`CH1817-L: Low power consumption and Common mode noise rejection filter
`CH1817-LM (special order): Reduced transmit attenuation
`CH1817-D: Differential transmission input and 0dB transmission insertion loss.


Pinout




Description

Ring Detection. Referring to the block diagram in Figure 1, incoming ring detection is performed by the CH1817 and the RI pin is set Low during the 2 second (typical) ring period and is restored to High for the 4 seconds (typical) between rings. During incoming ring signal activity, the RI output is pulsed at the same frequency as the ringing signal, typically 20Hz. Figure 2 contains additional external circuitry which may be used to provide an envelope indication of the ring signal. CH1817 internal ring detection circuit is designed to deter false indications due to pulse dialing or noise on the line.

The RI output of the CH1817 is diode protected. Therefore, an external pull-up resistor (R>100Kohm) to +5V may be utilized to activate the ring detection circuit when the CH1817 is not connected to power. This can be handy in designs where power consumption is of concern. When circuited in this manner, there is virtually no current draw until a ring signal is present.