Datasheet ADE7854, ADE7858, ADE7868, ADE7878 (Analog Devices) - 3

Silicon Anomaly ADE7854/ADE7858/ADE7868/ADE7878 Table 5. Values Written to the SAGLVL and ZXTOUT Registers May Not Be Immediately Used by ADE7854, ADE7858, ADE7868, and ADE7878 [er005, Version = 4 and Version = 5 Silicons] Background
Usually, the SAGLVL and ZXTOUT registers initialize immediately after power-up or after a hardware/software reset. After the run register is set to 1, the phase voltage sag detector (for SAGLVL), and the zero-crossing timeout circuit (for ZXTOUT) use these values immediately.
Issue
After the SAGLVL register is initialized with a new value after power-up or a hardware or software reset, the new value may be delayed and not available for immediate use by the phase voltage sag detector. However, it is used by the detector after at least one phase voltage rises above 10% of the full-scale input at the phase voltage ADCs. After the ZXTOUT register is initialized with a new value after power-up or a hardware or software reset, the new value may be delayed and not available for immediate use by the zero-crossing timeout circuit. However, the circuit does use the new value after at least one phase voltage rises above 10% of the full-scale input at the phase voltage ADCs.
Workaround
Usually, at least one of the phase voltages is greater than 10% of full scale after power-up or after a hardware/software reset. If this cannot be guaranteed, then the SAGLVL and ZXTOUT registers should be written eight consecutive times to reduce the probability of not being considered immediately by the phase voltage sag detector and zero-crossing timeout circuit below 0.2 ppm.
Related Issues
None.
SECTION 1. ADE7854/ADE7858/ADE7868/ADE7878 FUNCTIONALITY ISSUES Reference Number Description Status
er001 Offset rms registers cannot be set to negative values. Identified er002 Values written to the CF1DEN, CF2DEN, CF2DEN, SAGLVL, and ZXTOUT registers may not be immediately Identified used by ADE7854, ADE7858, ADE7868, and ADE7878. er003 The read-only rms registers may show the wrong value. Identified er004 To obtain best accuracy performance, internal setting must be changed. Identified er005 Values written to the SAGLVL and ZXTOUT registers may not be immediately used by ADE7854, ADE7858, Identified ADE7868, and ADE7878. Rev. C | Page 3 of 4 Document Outline ADE7854/ADE7858/ADE7868/ADE7878 Functionality Issues Functionality Issues Section 1. ADE7854/ADE7858/ADE7868/ADE7878 Functionality Issues