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Performance Screening Phase-Locked Loops for Ionic Contamination

IP.com Disclosure Number: IPCOM000099952D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Bocash, KC: AUTHOR [+4]

Abstract

Characteristics of a phase-locked loop (PLL) circuit in a burn-in test are used to make pass/fail measurements of ionic contamination in integrated circuit chips. In particular, ionic contamination affects linearity at extremes of a transfer curve of a voltage-controlled oscillator (VCO) within the PLL circuit. Increased response time between frequency applied and voltage out indicates ionic contamination in the VCO. Some local area network (LAN) chips contain a PLL. Other chips may have a PLL added to allow ionic contamination testing.

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Performance Screening Phase-Locked Loops for Ionic Contamination

       Characteristics of a phase-locked loop (PLL) circuit in a
burn-in test are used to make pass/fail measurements of ionic
contamination in integrated circuit chips.  In particular, ionic
contamination affects linearity at extremes of a transfer curve of a
voltage-controlled oscillator (VCO) within the PLL circuit.
Increased response time between frequency applied and voltage out
indicates ionic contamination in the VCO.  Some local area network
(LAN) chips contain a PLL.  Other chips may have a PLL added to allow
ionic contamination testing.

      Fig. 1 is a block diagram of a PLL circuit.  A frequency is
applied at IN to detector 10.  Output from detector 10 goes to charge
pump 12.  Output from charge pump 12 is connected to VCO 14, to an RC
filter 16, and also to precharge node A.  Signal at OUT is fed back
to detector 10.

      Fig. 2 is a transfer curve of the VCO, having voltage at node A
plotted along the horizontal axis and input frequency applied at IN
along the vertical axis.  Maximum frequency fmax, minimum frequency
fmin, and nominal frequency fnom are identified on the plot.  M0 is
the slope near midpoint of the transfer curve.  Slopes M1 and M2 of
straight dashed lines are used as indicators of non-linearity of the
transfer curve at its extremes.

      The test is performed by precharging node A in Fig. 1 to a
voltage level typical of that normally measured at a...