CH1817DM Datasheet

Family of Low Profile Daa Modules


Features, Applications

The is a Family of Low Profile Data Access Arrangement (DAA) Modules. They are compatible with all modem chip sets. These devices have been tested to meet or exceed FCC Part 68 requirements and are Canadian DOC approvable. They are also recognized by Underwriters Laboratories UL 1459 Specifications. The CH1817 modules are ultra small 1.0" x0.35") affording an easy integration into spacesensitive designs, including laptop and hand-held computer based products. The CH1817 family of products may be socketed or mounted directly onto a Printed Circuit Board (PCB). The telephone line connection is made through TIP and RING an RJ-11 jack or equivalent. The CH1817 is intended for use with FAX/modem chip sets that have a data throughput of up through V.32bis. For High Speed Applications, Cermetek recommends the CH1837A.


Low Profile, Ultra small size: x 0.35" Complete DAA function Ring detection Built-in 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.

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. The 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 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. RI Output: Active low Opto coupler, 30K pull-up Square wave: 15-68Hz (Typ. 20Hz) Sensitivity: 38Vrms across Tip & Ring

Hook Switch. The OFFHK input is used to control the on-hook and off-hook status of the CH1817. When OFFHK is low, the is in the On-Hook State. This indicates to the CO that the CH1817 is ready to receive calls. When OFFHK is high, the CH1817 allows the CO supplied loop current to flow, indicating either it is answering a call or preparing to place a call. OFFHK Input: Active High Active Current: To 4-Wire Hybrid Converter. This block has two functions: 1. It applies the XMIT signal to the phone line. 2. It subtracts the desired signal from the total outgoing signal on the phone line to derive the RCV signal. The accuracy of this derivation depends on how closely the impedance of the phone line matches 600 Ohms. Generally, a small amount of the XMIT signal will appear at RCV. The ratio of the applied XMIT signal to the received XMIT signal is called TransHybrid Rejection, or Trans-Hybrid Loss. a 600 phone line, the CH1817 DAAs have very high transhybrid rejection, typically 23 dB. NOTE The FCC requires that the DTMF tone not exceed 0dBm 150K XMIT 9.5dBm 150K

The outgoing analog signal to be transmitted through the phone line should be applied to the XMIT pin (with respect to GND) and must be AC coupled as shown in Figure 2. For the CH1817-D a XMIT and XMIT pins provide a differential input. The CH1817-L attenuates the transmit signal 9.5dB, 0dB for the �D option. Therefore, a transmit signal of 0dBm for the �L option (-9.5 dB for �D) applied to XMIT will comply with the FCC Part 68 requirement for data signals � 9dBm across TIP and RING.

The incoming analog signal appearing between TIP and RING is presented at RCV with respect to GND and must be AC coupled to the user equipment receive input. The CH1817 does not gain the receive signal. Receive signals can vary from a maximum strength �9dBm to below �50dBm. RCV Gain: 0dB Out impedance: 100 Typical Output Signal: to 0.27mVrms Signal referenced to GND AC coupling required

2002 Cermetek Microelectronics, Inc. Page 2 Document No. 607-0007 Revision B (01/02)

OFF HOOK. When set LOW, the CH1817 is placed On-Hook. When set HIGH, the CH1817 is placed Off-Hook to answer or place a call. This input can also be used for pulse dialing. NOTE: When answering incoming calls in response to a ring indication on RI, internal relay contact degradation may occur if OFFHK is set HIGH before RI returns to its HIGH state. RING INDICATION. It is asserted LOW by the CH1817 during the 2 second ON portion of the incoming AC Ring Signal and is asserted HIGH during the 4 second idle period between rings. An envelope of the AC ring signal may be created using the application circuit shown in Figure 2. RECEIVE. This provides the signal or audio output with respect to ground and must be AC coupled with a 0.1�F capacitor to eliminate DC offset. TRANSMIT SIGNAL Input a differential AC coupled audio signal with respect to XMIT(+), CH1817-D versions only. All others, No Connection. For single ended operation of CH1817-D, connect this pin to ground through a 0.1�F capacitor. POWER SUPPLY. � 5%

TRANSMIT SIGNAL Input an AC coupled audio signal with respect to ground. Input a differential signal with respect to XMIT(-) for the CH1817-D versions only. Ground. Must be connected to signal ground. Note: Noise should be less than 25mV peak-to-peak.



Manufacturer information

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