Specifications

AN93
Rev. 0.8 81
Table 54. U67 Bit Map
Bit Name Function
15:14 Reserved Read returns zero.
13:12 MINI[1:0] Minimum Operational Loop Current.
Adjusts the minimum loop current at which the DAA can operate. Increasing the minimum oper-
ational loop current can improve signal headroom at a lower TIP/RING voltage.
MINI[1:0] Min Loop Current
00 10 mA
01 12 mA
10 14 mA
11 16 mA
11:10 Reserved Read returns zero
9ILIMCurrent Limiting Enable.
0 = Current limiting mode disabled.
1 = Current limiting mode enabled. This mode limits loop current to a maximum of 60 mA per
the CTR21 standard.
8 Reserved Read returns zero.
7 DCR DC Impedance Selection.
0=50 Ω dc termination slope is selected. This mode should be used for all standard
applications.
1 = 800 Ω dc termination is selected.
6OHSOn-Hook Speed.
See OHS2.
5:4 Reserved Read returns zero.
3:2 DCV[1:0] TIP/RING Voltage Adjust.
These bits adjust the voltage on the DCT pin of the line-side device, which affects the TIP/RING
voltage on the line. Low voltage countries should use a lower TIP/RING voltage. Raising the
TIP/RING voltage can improve signal headroom.
DCV[1:0] DCT Pin Voltage
00 3.1 V
01 3.2 V
10 3.35 V
11 3.5 V
1RZRinger Impedance.
0 = Maximum (high) ringer impedance.
1 = Synthesize ringer impedance. C15, R14, Z2, and Z3 must not be installed when setting this
bit. See the “Ringer Impedance” section in AN93.
0RTRinger Threshold Select.
Used to satisfy country requirements on ring detection. Signals below the lower level does not
generate a ring detection; signals above the upper level are guaranteed to generate a ring
detection.
0 = 11 to 22 V
rms
.
1 = 17 to 33 V
rms
.