8.3.1 CMOS Open-Drain Outputs

The open-drain output allows the device to sink current to GND but not to source current from V_CC. When the output is not actively pulling the line low, it will go into a high impedance state (tri-state). This allows the device to be used for a wide variety of applications, including up-translation and down-translation, as the output voltage can be determined by an external pullup.

The drive capability of this device creates fast edges into light loads so routing and load conditions should be considered to prevent ringing. Additionally, the outputs of this device are capable of driving larger currents than the device can sustain without being damaged. It is important for the power output of the device to be limited to avoid thermal runaway and damage due to over-current. The electrical and thermal limits defined in the Absolute Maximum Ratings must be followed at all times.

8.3.2 Standard CMOS Inputs

The impendence for standard CMOS inputs is high. Typically, a CMOS input is modeled as a resistor in parallel with the input capacitance as shown in the Electrical Characteristics. The worst case resistance is calculated with the maximum input voltage, given in the Absolute Maximum Ratings, and the maximum input leakage current, given in the Electrical Characteristics, using ohm's law (R = V ÷ I).

Signals applied to the inputs need to have fast edge rates, as defined by Δt/Δv in the Recommended Operating Conditions to avoid excessive current consumption and oscillations. If a slow or noisy input signal is required, a device with a Schmitt-trigger input should be used to condition the input signal before the standard CMOS input.

8.3.3 Negative Clamping Diodes

The inputs and outputs to this device have negative clamping diodes as depicted in Figure 5.

Figure 5. Electrical Placement of Clamping Diodes for Each Input and Output

8.3.4 Partial Power Down (I_off)

Each input and output enter a high impedance state when the supply voltage is 0 V. The maximum leakage into or out of any input or output pin on the device is specified by I_off in the Electrical Characteristics.

8.3.5 Over-voltage Tolerant Inputs

Input signals to this device can be driven above the supply voltage as long as the input signals remain below the maximum input voltage value specified in the Recommended Operating Conditions.

Table 1. Function Table