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. Table 1. DS21348, DS21Q348 Register Settings Operating Voltage: 3.3V (VSM pin wired low) Applicable Devices: DS21348, DS21Q348 Applicable Device Revisions: A2, B1, C1, and C2 (DS21Q348) Operating Mode: E1 L2 (CCR4.7) L1 (CCR4.6) L0 (CCR4.5) APPLICATION TYPICAL CHANGE IN PULSE AMPLITUDE RETURN LOSS (dB) Rt (Ω) 0 1 0 75Ω normal 7% enhancement over LBO setting 0 N.M. 0 0 1 1 120Ω normal 8% enhancement over LBO setting 1 N.M. 0 1 1 0 120Ω normal with high return loss 8% attenuation over LBO setting 5 21 9.1 1 1 1 120Ω normal with high return loss 4% attenuation over LBO setting 5 21 10 N.M. = not meaningful Table 2. DS2148, DS21Q48 Register Settings Operating Voltage: 5V (VSM pin wired high) Applicable Devices: DS2148, DS21Q48 Applicable Device Revisions: A2, B1, C1 and C2 (DS21Q48) Operating Mode: E1 L2 (CCR4.7) L1 (CCR4.6) L0 (CCR4.5) APPLICATION TYPICAL CHANGE IN PULSE AMPLITUDE RETURN LOSS (dB) Rt (Ω) 0 1 0 75Ω normal 10% enhancement over LBO setting 0 N.M. 0 0 1 1 120Ω normal 10% enhancement over LBO setting 1 N.M. 0 1 1 0 120Ω normal with high return loss 10% attenuation over LBO setting 5 21 22 1 1 1 120Ω normal with high return loss 10% enhancement over LBO setting 5 21 33 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. To learn more about testing Dallas Semiconductor line interface units and transceivers for compliance to T1/J1 and E1 pulse mask specifications, refer to Application Note 397: Pulse Template Measurement We Want Your Feedback! Automatic Updates Would you like to be automatically notified when new application notes are published in your areas of interest? Sign up for EE-Mail™. More Information   APP 402: Mar 21, 2003 DS21348 3.3V E1/T1/J1 Line Interface Full Data Sheet (PDF, 792kB) Free Samples DS21448 3.3V E1/T1/J1 Quad Line Interface Full Data Sheet (PDF, 836kB) Free Samples DS2148 5V E1/T1/J1 Line Interface Full Data Sheet (PDF, 1.1MB) Free Samples DS21Q348 3.3V E1/T1/J1 Line Interface Full Data Sheet (PDF, 792kB) DS21Q48 5V E1/T1/J1 Line Interface Full Data Sheet (PDF, 1.1MB)   Download, PDF Format (46kB)  AN402, AN 402, APP402, Appnote402, Appnote 402