Additional Pulse Amplitude Settings for DS2148, DS21348, DS21Q48, DS21Q348 and DS21448
Mar 21, 2003
Abstract: This application note shows how to use undocumented settings to modify output amplitudes.
Introduction
This application note provides the register settings for the DS2148/DS21348/DS21Q48/DS213Q48 and DS21448 to configure the transmitter for pulse amplitudes that are different than the line build-out (LBO) modes documented in the respective data sheets. The following tables list the register settings and define the resulting pulse amplitudes for the 3.3V (DS21348, DS21Q348) and 5V (DS2148, DS21Q48) devices.
In addition to the these settings, additional pulse amplitudes can be obtained in the following devices by setting test register 2 (Address 14h) as per Table 3.
Table 3. Additional Pulse Amplitude Settings
OPERATING MODE
APPLICABLE DEVICES
APPLICABLE DEVICE REVISIONS
TEST2 (ADDRESS 14h) REGISTER SETTINGS
TYPICAL CHANGE IN PULSE AMPLITUDE
E1
DS21348, DS21Q348
C1
D0
38% enhancement over LBO setting 0, 1, 2, and 3
DS21348, DS21Q348, DS2148, DS21Q48
C1
E0
19% enhancement over LBO setting 0, 1, 2, and 3
T1/J1
DS21348, DS21Q348
C1
D0
38% enhancement over LBO setting 0, 5, 6, and 7
DS21348, DS21Q348, DS2148, DS21Q48
C1
E0
19% enhancement over LBO setting 0, 5, 6, and 7
E1
DS21448
A1
D0
33% enhancement over LBO setting 0, 1, 2, and 3
T1/J1
DS21448
A1
D0
33% enhancement over LBO setting 0, 5, 6, and 7
In addition to the above settings, writing a HEX BO in address 14h (register TEST2) reduces any tendency of the waveform to ring.
