Can I Connect an E5 to a 5-volt Device?

A Triscend E5 device interfaces with most 5-volt devices. The E5’s PIO pins are fully 5-volt tolerant even though the E5’s I/O supply voltage, VCCIO, is only 3.3 volts. This capability allows 5-volt signals to connect directly to the E5 inputs without damage. In addition, the E5’s 3.3-volt VCC and VCCIO power inputs can be applied before or after 5 volt signals are applied to the I/Os. This makes the E5 immune to power supply sequencing problems.

Figure 1. The 3.3-volt Triscend E5 Interfaces with all 5-volt TTL and most 5-volt CMOS devices.

As shown in Figure 1, an E5 CSoC device accepts both TTL and CMOS inputs from a 5-volt device. Built-in over-voltage protection prevents any latch up or potential device damage caused by applying a 5-volt signal to the 3.3-volt E5 device.

Likewise, the E5’s PIO outputs drive valid TTL levels to a 5-volt device. Most 5-volt devices, including 5-volt CMOS parts, have TTL-compatible inputs. Most 5-volt CMOS devices have HCT-style inputs that operate at TTL levels but translate the incoming TLL signal to CMOS levels inside the device.

The only potential voltage-standard mismatch occurs when the E5 drives a pure 5-volt CMOS device with CMOS-only inputs. However, CMOS devices with CMOS-only inputs are typically used in very lower power applications. The E5 device interfaces directly with other 3.3-volt CMOS devices. For power sensitive applications, switching to a 3.3-volt CMOS device instead of a 5-volt device cuts power consumption nearly in half and eliminates any potential voltage-standard mismatch.

The PIOs on the A7 CSoC family can drive a 5-volt TTL or HCT device but cannot accept 5-volt inputs.