ADSP-2156x Power Sequencing Requirements
This note explains power sequencing for ADSP-2156x processors to mitigate indeterminate I/O voltage glitches during power-up by ramping VDD_REF before VDD_EXT.
Overview
Application note EE-470 details the power sequencing requirements for ADSP-2156x SHARC+ processors to prevent indeterminate output voltage glitches on I/O pins. These glitches occur when the VDD_EXT supply ramps up before VDD_REF reaches a stable state, potentially causing erratic behavior in connected SoCs, FPGAs, or memory devices. The document specifies that VDELTA_EXT_REF must be maintained within +/-1.89V across all power phases. It provides mitigation strategies including specific ramping orders, the use of supervisory reset ICs, and bidirectional buffers. Reference power supply designs are illustrated using Analog Devices LT8636 and LTC3307A regulators.
Use Cases
- Interfacing ADSP-2156x processors with FPGAs or SoCs
- Protecting external memory from erratic writes during power-up
- Implementing reliable reset circuits using supervisory ICs
- Designing multi-rail power supplies for high-performance DSPs
Topics
Referenced Parts
MAX16161
Analog Devices
MAX16161/MAX16162 nanoPower Supply Supervisors with Glitch-Free Power-Up Data Sheet
MAX16162
Analog Devices
MAX16161/MAX16162 nanoPower Supply Supervisors with Glitch-Free Power-Up Data Sheet
| ADP151 | Analog Devices | ADP151 Ultralow Noise, 200 mA, CMOS Linear Regulator Data Sheet |
| ADSP-21562 | Analog Devices | ADSP-21562/21563/21565/21566/21567/21569 Data Sheet (Rev. D). |
| ADSP-21563 | Analog Devices | ADSP-21562/21563/21565/21566/21567/21569 Data Sheet (Rev. D). |
| ADSP-21565 | Analog Devices | ADSP-21562/21563/21565/21566/21567/21569 Data Sheet (Rev. D). |
| ADSP-21566 | Analog Devices | ADSP-21562/21563/21565/21566/21567/21569 Data Sheet (Rev. D). |
| ADSP-21567 | Analog Devices | ADSP-21562/21563/21565/21566/21567/21569 Data Sheet (Rev. D). |
| ADSP-21569 | Analog Devices | ADSP-21562/21563/21565/21566/21567/21569 Data Sheet (Rev. D). |
| LT8636 | Analog Devices | LT8636 (VDD_EXT) and LTC3307A (VDD_REF) Regulators Supplied by Common Input. |
| LT8637 | Analog Devices | LT8636/LT8637 42V, 5A/7A Peak Synchronous Step-Down Silent Switcher |
| LTC3307A | Analog Devices | LTC3307A 5V, 3A Synchronous Step-Down Silent Switcher |
| MAX16161 | Analog Devices | MAX16161/MAX16162 nanoPower Supply Supervisors with Glitch-Free Power-Up Data Sheet |
| MAX16162 | Analog Devices | MAX16161/MAX16162 nanoPower Supply Supervisors with Glitch-Free Power-Up Data Sheet |