Application Note OUTPUT TRI-STATE FUNCTION CB3 and MXO45 The output tri-state function is achieved using two different methods. Each method is dependent on the internal configuration of the oscillator ASIC and provides different functional characteristics. A brief description of each method follows. TRI-STATE – OSCILLATOR STOP The oscillator stop function is represented by the schematic of Figure 1. In this configuration, when the INH pin is at Logic 1 or left floating, transistor M1 is turned off allowing the oscillator to run. The output buffer is also activated and the clock signal is present at the output pin. When INH is pulled to Logic 0, transistor M1 is turned on pulling the input to the oscillator gate to ground forcing it to stop oscillating. This also disables (tri-state) the output buffer placing the output pin into a high impedance state. The standby current is very low due to the oscillator shutting off, but the clock signal will take longer to reactivate at the output because the oscillator must restart. Table 1 provides a summary of typical specifications for this method. FIGURE 1 TRI-STATE – OSCILLATOR STOP PARAMETER SYMBOL Enable Input Voltage VIH Disable Input Voltage VIL Standby Current IST Output Enable Time Oscillator Start-up Time tPLZ - CONDITION Logic 1 or NC Output High Impedance V IL = 0.8V Oscillator stops running V IH = 2.0V Application of V CC MINIMUM 2.0 - MAXIMUM 0.8 15 UNITS V V uA - 10 10 mS mS TABLE 1 ♦ ♦ ♦ CTS Communications Components, Inc . ♦ 171 Covington Drive ♦ Bloomingdale, IL 60108 ♦ 630-924-3500 ♦ ♦ ♦ Document No. 014-0002-0 Rev B ECO # 16772 Page 1 of 2 Application Note OUTPUT TRI-STATE FUNCTION CB3 and MXO45 TRI-STATE – OSCILLATOR RUN The oscillator run function is represented by the schematic of Figure 2. In this configuration, when the INH pin is at Logic 1 or left floating, the oscillator stage is running and the output buffer is active. The clock signal is present at the output pin. When INH is pulled to Logic 0, the output buffer is disabled (tri-state) placing the output pin into a high impedance state, but the oscillator stage remains running. The standby current will be higher in this configuration due to an active oscillator stage, but the clock signal can be reactivated at the output much faster since there is no wait time for the oscillator to start-up. Table 2 provides a summary of typical specifications for this method. FIGURE 2 TRI-STATE – OSCILLATOR RUN PARAMETER SYMBOL Enable Input Voltage VIH Disable Input Voltage VIL Tri-state Current IZ Output Enable Time Oscillator Start-up Time tPLZ - CONDITION Logic 1 or NC Output High Impedance V IL = 0.8V Oscillator remains running V IH = 2.0V Application of V CC MINIMUM 2.0 - MAXIMUM 0.8 ICC UNITS V V mA - 100 10 nS mS TABLE 2 Each method described above is approved by CTS and both technologies are used in the CB3 and MXO45 clock oscillator product families. The following table indicates which method of tri-state function will be used for a given product family. PRODUCT FAMILY MXO45TLV MXO45HSTLV CB3LV MXO45T MXO45HST CB3 TRI-STATE METHOD OSCILLATOR STOP OSCILLATOR STOP or OSCILLATOR RUN ♦ ♦ ♦ CTS Communications Components, Inc . ♦ 171 Covington Drive ♦ Bloomingdale, IL 60108 ♦ 630-924-3500 ♦ ♦ ♦ Document No. 014-0002-0 Rev B ECO # 16772 Page 2 of 2