Cermetek Microelectronics, Inc.
CH1837A/7F/8A Data Access Arrangement Module
2002 Cermetek Microelectronics, Inc.
Page 5
Document No. 607-0014 Revision C2 (12/02)
Table 1. CH1837A/F Pin Description.
PIN
I/O
CH1837A/F
FUNCTION
1
I/O
TIP
TIP. Direct PSTN line connection.
2
I/O
RING
RING. Direct PSTN line connection.
3
I
OFFHK
OFF-HOOK. Used to toggle CH1837A/F product between On-Hook and Off-Hook.
When set LOW, CH1837A/F is On-Hook. When set HIGH, CH1837A/F is set Off-
Hook to answer or place a call. See Note 1.
4
O
RI
RING INDICATION. Indicates the presence of a ring signal between TIP and RING
pins. RI output is a square wave coincident with the incoming AC ring signal. The
RI square wave output can be conditioned to produce an envelope of the incoming
AC ring signal by using the circuit in Figure 4. See Notes 2 and 3.
5
O
RCV
RECEIVE. Audio output signal with respect to GND. AC couple RCV through
0.1
µF capacitor to eliminate any DC offset.
6
I
XMIT(-)
TRANSMIT(+). Audio input signal. AC couple through 0.1
µF capacitor. The
CH1837A/F can be used in differential mode with XMIT(+) or in single ended mode
with respect to GND.
7
I
VCC
POWER SUPPLY. +5V
±5%. Supply line noise should be less than 50mV peak to
peak.
8
I
XMIT(+)
TRANSMIT(-). Audio input signal for CH1837A/Fwhen used in differential mode
only. Connect to GND through 0.1
µF capacity when CH1837A/F used in single
ended input via PIN 8.
9
I
GND
GROUND. Supply line noise should be less than 50mV peak to peak.
Note:
1. When answering incoming calls in response to a ring indication on RI, internal degradation may occur if OFFHK
is set HIGH before RI returns to its HIGH state.
2. For CH1837A, the RI output is 2X the frequency of the incoming ring signal.
3. For CH1837F, the RI output is 1X the frequency of the incoming ring signal.
Table 2. CH1838A Pin Description.
PIN
I/O
CH1838A
FUNCTION
1
I/O
TIP
TIP. Direct PSTN line connection.
2
I/O
RING
RING. Direct PSTN line connection.
3
I
OFFHK
OFF-HOOK. Used to toggle CH18378 product between On-Hook and Off-Hook.
When set LOW, CH1838 is On-Hook. When set HIGH, CH1838 is set Off-Hook to
answer or place a call. See Note 1.
4
O
RI
RING INDICATION. Indicates the presence of a ring signal between TIP and
RING pins. RI output is a square wave coincident with the incoming AC ring
signal. The RI square wave output can be conditioned to produce an envelope of
the incoming AC ring signal by using the circuit in Figure 4. The RI output is 2X
the frequency of the incoming ring signal.
5
I/O
T1
RECEIVE. Audio input and output signal with respect to T2.
6
N/C
N/C
AUDIO INPUT/OUTPUT. Internally not connected. Either let float or connect to
GND.
7
I
VCC
POWER SUPPLY. +5V
±5%. Supply line noise should be less than 50mV peak to
peak.
8
I/O
T2
AUDIO INPUT/OUTPUT. Audio input and output signal with respect to T1.
9
I
GND
GROUND. Supply line noise should be less than 50mV peak to peak.
Note:
1. When answering incoming calls in response to a ring indicator on RI, internal degradation may occur if OFFHK
is set HIGH before RI returns to its HIGH state.
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