TLC2943 Datasheet, PDF (4/27 Pages) Texas Instruments – HIGH-PERFORMANCE DUAL PHASE-LOCKED BUILDING BLOCK

TLC2943
HIGH-PERFORMANCE DUAL PHASE-LOCKED BUILDING BLOCK
SLAS249 – NOVEMBER 1999
detailed description
MCM (multichip module) technology for TLC2943
The TLC2943 is a multichip module (MCM) product that uses two TLC2933 chips. Inside the package, two chips
are completely isolated by a special formed lead-frame. Therefore,when using the TLC2943 in two
asynchronous PLL circuits, there is no performance degradation by electrical interference between chips inside
the package. So, the same performance as TLC2933 can be easily expected by using TLC2943.
The NC terminals in the middle on both sides of the package are to achieve complete isolation inside the
package. To get the best performance from this MCM technology, it is better to make a careful board layout of
the external power supply, ground, and signal lines.
voltage controlled oscillator (VCO)
VCO_1 and VCO_2 have the same typical characteristics. Each VCO oscillation frequency is determined by
an external resistor (R_BIAS) connected between the VCO V_DD and the BIAS terminals. The oscillation frequency
and range depend on this resistor value. The bias resistor value for the minimum temperature coefficient is
nominally 2.2 kΩ with V_DD = 3.3 V and nominally 2.4 kΩ with V_DD = 5 V. For the lock frequency range, refer to
the recommended operating conditions. Figure 1 shows the typical frequency variation and VCO control
voltage.
VCO Oscillation Frequency (fosc)
VCO Oscillation Frequency Range
BIAS Resistor (RBIAS)
VCO Control Voltage (VCOIN)
Figure 1. VCO_1 and VCO_2 Oscillation Frequency
VCO inhibit function
Each VCO has an externally controlled inhibit function that inhibits the VCO output. The VCO oscillation is
stopped during a high level on VCOINHIBIT, so the high level can also be used as the power-down mode. The
VCO output maintains a low level during the power-down mode (see Table 1 and Table 2).
Table 1. VCO_1 Inhibit Function
VCO_1 INHIBIT
Low
High
VCO_1 OSCILLATOR
Active
Stop
VCO_1 OUT
Active
Low
VCO_1 IDD
Normal
Power down
Table 2. VCO_2 Inhibit Function
VCO_2 INHIBIT
Low
High
VCO_2 OSCILLATOR
Active
Stop
VCO_2 OUT
Active
Low
VCO_2 IDD
Normal
Power down
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