In some applications, inputs are required to have a default logic state at power-up. This requirement often occurs when buffers are used to interface both control and data signals to a bus. As the power-up state of the bus-hold circuit is not guaranteed, an external resistor is required to set the default state. The value of the resistor should be such that it overdrives the bus-hold input to the desired state during power-up. Equations (1) and (2) can be used to estimate the maximum value of pull-down resistor R_PD or pull-up resistor R_PU to overdrive the bus-hold circuit. V_TH is the input switching threshold voltage; this can be estimated as (V_IH + V_IL)/2.