TLC2942 Datasheet, PDF (4/28 Pages) Texas Instruments – HIGH-PERFORMANCE DUAL PHASE-LOCKED LOOP BUILDING BLOCK

TLC2942
HIGH-PERFORMANCE DUAL PHASE-LOCKED LOOP BUILDING BLOCK
SLAS146B – NOVEMBER 1996 – REVISED JUNE 1997
detailed description
multichip module
The TLC2942 is a multichip module (MCM) product that uses two TLC2932 chips. A newly developed lead frame
for TLC2942IBD is specially shaped and cut in the package to electrically isolate one chip from another. The
two chips are completely independent from each other to perform the best stable oscillation and locking. If
asynchronous locking operation is required for these two PLL blocks, each TLC2942 VCO and PFD can achieve
the same stability as the single chip TLC2932IPW.
Three NC terminals are on both sides of the package between chip1 and chip2 due to the lead frame shape.
To avoid performance degradation, special attention is needed for each PLL block PCB layout especially for
supply voltage lines and GND patterns.
voltage-controlled oscillator (VCO)
VCO1 and VCO2 have the same typical characteristics. Each VCO oscillation frequency is determined by an
external resistor (R_BIAS) connected between each VCO V_DD and BIAS terminals. The oscillation frequency and
range depends on this register value. The bias resistor value for the minimum temperature coefficient is
nominally 3.3 kΩ with V_DD = 3 V and nominally 2.2 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 Range
Bias Resistor (RBIAS)
1/2 VDD
VCO Control Voltage (VCOIN)
Figure 1. VCO1 and VCO2 Oscillation Frequency
VCO output frequency 1/2 divider
SELECT1 and SELECT2 select between f_osc and 1/2 f_osc for the VCO output frequencies as shown in Table 1.
Table 1. SELECT1 and SELECT2 Function Table
SELECT1
Low
High
VCO1 OUTPUT
FREQUENCY
fosc1
1/2 fosc1
SELECT2
Low
High
VCO2 OUTPUT
FREQUENCY
fosc2
1/2 fosc2
4
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