Category: Hardware
Product Number: HMC4069
During the use of the HMC4069 device, two instances of chip damage have occurred. The failure symptom is a short circuit between the VCC pin and ground. Meanwhile, the impedance of other pins is an order of magnitude lower than that of a normal chip. Both damaged units failed after approximately six months of operation. I have reviewed the surrounding peripheral circuits and have the following questions:
- When the device is initially powered on without enabling the HMC4069, voltage leakage is observed from the control pins to the VCC and NUND pins. Will this leakage cause long-term damage to the chip?
- I captured the lock and unlock behavior using an oscilloscope. Why does the unlock state come with a fixed low-level duration of about 2.5 seconds?
- The datasheet specifies that the NUND pin voltage must not drop below 2.5 V. Does this requirement apply under specific operating conditions, or must NUND be kept above 2.5 V continuously from power-up and enablement?
- Are there any other potential root causes that may lead to this type of gradual chip damage after long-term operation?
Figure 1 shows the schematic of the HMC4069 and the peripheral op-amp circuit. Figure 2 displays the NUND waveform during locked status, and Figure 3 shows the NUND waveform during unlock status.
