Specifications ispLSI 2128V

8

Power Consumption

Power consumption in the ispLSI 2128V device depends

on two primary factors: the speed at which the device is

operating and the number of Product Terms used.

Figure 3 shows the relationship between power and

operating speed.

Figure 3. Typical Device Power Consumption vs fmax

200

175

250

020

40

60

80

Notes: Configuration of eight 16-bit counters

Typical current at 3.3V, 25

° C

ispLSI 2128V

275

225

0127/2128V

ICC can be estimated for the ispLSI 2128V using the following equation:

ICC (mA) = 40 + (# of PTs * 0.6) + (# of nets * Max freq * 0.004)

Where:

# of PTs = Number of Product Terms used in design

# of nets = Number of Signals used in device

Max freq = Highest Clock Frequency to the device (in MHz)

The ICC estimate is based on typical conditions (VCC = 3.3V, room temperature) and an assumption

of two GLB loads on average exists. These values are for estimates only. Since the value of ICC is

sensitive to operating conditions and the program in the device, the actual ICC should be verified.

Power-up Considerations

When Lattice 3.3V 2000V devices are used in mixed 5V/

3.3V applications, some consideration needs to be given

to the power-up sequence. When the I/O pins on the

3.3V ispLSI devices are driven directly by 5V devices, a

low impedance path can exist on the 3.3V device be-

tween its I/O and Vcc pins when the 3.3V supply is not

present. This low impedance path can cause current to

flow from the 5V device into the 3.3V ispLSI device. The

maximum current occurs when the signals on the I/O pins

are driven high by the 5V devices. If a large enough

current flows through the 3.3V I/O pins, latch-up can

occur and permanent device damage may result.

This latch-up condition occurs only during the power-up

sequence when the 5V supply comes up before the 3.3V

supply. The Lattice 3.3V ispLSI devices are guaranteed

to withstand 5V interface signals within the device oper-

ating Vcc range of 3.0V to 3.6V.

The recommended power-up options are as follows:

Option 1: Ensure that the 3.3V supply is powered-up and

stable before the 5V supply is powered up.

Option 2: Ensure that the 5V device outputs are driven to

a high impedance or logic low state during power-up.