CH1817
Family of Low Profile DAA Modules
INTRODUCTION FEATURES
The CH1817 is a Family of Low Profile Data Access
Low Profile, Ultra small size: 1.0 x 1.0 x 0.35
Arrangement (DAA) Modules. They are compatible
Complete DAA function
with all modem chip sets. These devices have been
Ring detection
tested to meet or exceed FCC Part 68 requirements
Built-in 2-wire to 4-wire conversion
and are Canadian DOC approvable. They are also
Lightweight
recognized by Underwriters Laboratories to UL 1459
Multimedia compatible
Specifications.
+5V operation
The CH1817 modules are ultra small (1.0 x 1.0 1000 VAC isolation
x0.35) affording an easy integration into space-
800 Volt surge protection
sensitive designs, including laptop and hand-held
V.32bis/14,400bps, applications
computer based products. The CH1817 family of
UL1459 recognized
products may be socketed or mounted directly onto a
CH1817-L: Low power consumption and Common
Printed Circuit Board (PCB). The telephone line
mode noise rejection filter
connection is made through TIP and RING to an RJ-11
CH1817-LM (special order): Reduced transmit
jack or equivalent.
attenuation
The CH1817 is intended for use with FAX/modem chip
CH1817-D: Differential transmission input and 0dB
sets that have a data throughput of up through
transmission insertion loss.
V.32bis. For High Speed Applications, Cermetek
RoHS Compliant versions available.
recommends the CH1837A.
FUNCTIONAL DESCRIPTION
Ring Detection. Referring to the block diagram in
V GND
CC
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
TIP
SURGE
seconds (typical) between rings. During incoming ring
AND
signal activity, the RI output is pulsed at the same
ISOLATION
PROTECTION
frequency as the ringing signal, typically 20Hz. Figure
RING
CIRCUITRY
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.
XMIT OFF-HOOK
The RI output of the CH1817 is diode protected.
HYBRID
SWITCH
Therefore, an external pull-up resistor (R>100Kohm) 2W/4W
CONVERTER
to +5V may be utilized to activate the ring detection
RCV
RING DET.
circuit when the CH1817 is not connected to power.
This can be handy in designs where power
RI
consumption is of concern. When circuited in this
manner, there is virtually no current draw until a ring
signal is present.
OFFHK
RI
Output: Active low
Opto coupler, 30K pull-up
Square wave: 15-68Hz (Typ. 20Hz)
Figure 1. CH1817 DAA Functional Block Diagram.
Sensitivity: 38Vrms across Tip & Ring
2006 Cermetek Microelectronics, Inc. Page 1 Document No. 607-0007 Revision C (11/06) Cermetek Microelectronics, Inc. CH1817 Family of Low Profile DAA Modules
Hook Switch. The OFFHK input is used to control the
TRANSMIT SIGNAL
on-hook and off-hook status of the CH1817. When
The outgoing analog signal to be transmitted through
OFFHK is low, the CH1817 is in the On-Hook State.
the phone line should be applied to the XMIT pin (with
This indicates to the CO that the CH1817 is ready to
respect to GND) and must be AC coupled as shown in
receive calls. When OFFHK is high, the CH1817
Figure 2. For the CH1817-D a XMIT (+) and XMIT (-)
allows the CO supplied loop current to flow, indicating
pins provide a differential input. The CH1817-L
either it is answering a call or preparing to place a call.
attenuates the transmit signal by 9.5dB, 0dB for the D
option. Therefore, a transmit signal of 0dBm for the L
OFFHK
option (-9.5 dB for D) applied to XMIT will comply
Input: Active High
with the FCC Part 68 requirement for data signals of
Active Current: 4mA
9dBm across TIP and RING.
2-Wire To 4-Wire Hybrid Converter. This block has
two functions: RECEIVE SIGNAL
1. It applies the XMIT signal to the phone line. The incoming analog signal appearing between TIP
2. It subtracts the desired signal from the total and RING is presented at RCV with respect to GND
outgoing signal on the phone line to derive the and must be AC coupled to the user equipment
RCV signal. receive input. The CH1817 does not gain the receive
signal. Receive signals can vary from a maximum
The accuracy of this derivation depends on how strength of 9dBm to below 50dBm.
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 RCV
signal to the received XMIT signal is called Trans-
Gain: 0dB
Hybrid Rejection, or Trans-Hybrid Loss. On a 600
Out impedance: 100
phone line, the CH1817 DAAs have very high trans- Typical Output Signal:
hybrid rejection, typically 23 dB.
-9dBm to 50dBm
2.5Vrms to 0.27mVrms
NOTE Signal referenced to GND
The FCC requires that the DTMF tone not exceed AC coupling required
0dBm.
XMIT
CH1817-D CH1817-L CH1817-DM CH1817-LM
Attenuation 0dBm 9.5dBm 6.5dBm 6.5dBm
Input Impedance
150K 150K 150K 150K
Figure 2. Typical CH1817 Application.
2006 Cermetek Microelectronics, Inc. Page 2 Document No. 607-0007 Revision C (11/06)