This document is an Engineer-to-Engineer Note from Analog Devices about using their DSP components and development tools. It introduces how to perform level conversion between ICs operating at different voltage/logic levels, including 5V and 3.3V ICs.
This document addresses interface issues between Analog Devices 3.3v DSP processors and 5v peripherals. It explains that while many DSPs support 3.3v I/O standards, they cannot tolerate input voltages exceeding their supply voltage plus 0.5v. Consequently, additional logic is required to connect these devices to 5v systems without causing damage or signal integrity issues.
The recommended solution is the use of a Bus Switch, also known as a QuickSwitch. These bi-directional ICs act as voltage level translators, shunting excess voltage to protect the 3.3v device while allowing normal signal transmission. The note details the transfer function of a Bus Switch, noting a typical propagation delay of 0.25ns, and suggests using a diode to generate the required 4.3v reference voltage for the switch.
| Propagation Delay | 0.25ns |
|---|
You must add a Bus Switch (QuickSwitch) to the system to add voltage tolerance between the two ICs.
No, because Bus Switches are bi-directional ICs, no additional routing logic is needed for the connection.