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Failure Analysis of Burned ADF4153 & ADF4106

Question asked by Dorin on Mar 27, 2012
Latest reply on Mar 29, 2012 by Dorin

Dear all,

 

we have recently experienced a number of return of synthesizers build with ADF4153 and ADF4106.

 

These circuits use 2 supplies of +5V (VCO and PLL) supply and 15-20V (Vtune).

The PLL supply of 3.3V comes from the +5V through a low noise regulator. The VP is tied to +5V of VCO.

The charge-pump pin 20 is connected to the negative input of an OpAmp (used as integrator for the PLL filter).

The OpAmp supply is 15-20V to GND.

 

All these cases exhibit low impedance on the charge-pump pin (Pin 20).

 

I have removed (un-soldered) the ADF4153 from the PCB and I checked the impedance with a multimeter (set for diode/continuity measurement).

The following is the result of the measurement:

MeasurementReturned ADF4153
Good ADF4153
CP (pin20) -> GND28 OhmOpen
GND -> CP (pin20)28 Ohm0.569V (ESD diode)
Vp (Pin18) -> GND1.5VOpen
GND -> VP (Pin18)0.57V0.565V
Rset (pin 19)-> GND2.01VOpen
GND-> RSET (pin 19)0.585V0.569V

Please note that the 28Ohm impedance to ground was observed also when the ADF4153 was soldered on PCB. The good-working PCBs do not exhibit this short.

 

The answer to the following question will be appreciated:

 

Q1. In your opinion, what could cause such behavior?

Q2. Is it possible to investigate the failure on the damaged device?

Q3. What FIB houses could provide such investigation?

Q4. How much would cost the failure investigation ?

 

Best regards,

Dorin

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