This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

[FAQ] TPS2640 TPS2660: How to recover fast during supply line interruptions ?

Guru* 94516 points
Part Number: TPS2640
Other Parts Discussed in Thread: TPS2663, TPS2660

How to recover fast during supply line interruptions ?

  • During supply line interruptions, the TPS2640 eFuse turns-OFF and restarts in dVdT mode which takes significant amount of time to recover the output voltage. Till that time, the load has to be supported by the buffer capacitor to meet class-A system performance.

    Let’s take an example with specifications:

    Vin = 24V

    Cout = 440 µF

    Cdvdt = 680 nF

    Rilim = 22.4 kΩ sets Current limit at 530 mA

    Load = 200 mA

    Power fail interval = 5 ms

    As you see in the below test waveform, the output voltage drops as low as 6-V due to slow restart in dVdT mode. That means the Cout has to be increased dramatically and it is just case of load current as low as 200 mA.  

    Solutions:

    1. Use TPS2663 which by device architecture considers this aspect and designed with fast recovery mode of operation.
    2. To overcome this issue for TPS2640, TPS2660 devices, a series resistor can be placed in the dVdT path. When the input supply resumes back, the dVdT pin sources current IdVdT and creates an offset voltage (Idvdt*R25) at the Cdvdt pin. The offset voltage forces the eFuse to operate in current limit mode and enables quick recovery of the output voltage.

    As seen in the below test waveform, the device starts in current limit mode and quickly recovers the output voltage.