7-Bit DAC output repels (repels) reduction

My DAC is giving a spikes or repels at its output.... it works with input of frequency of 140 KHz.
I mainly use this DAC for a SAR ADC, its so weird any help ?

You will need to tell us more about your issue: including what is the DAC, how are you sending data to it etc.
As a wild guess, some DACs have an internal 'default value' they use if you are not sending data to them fast enough; that can cause "spikes" to appear when the default value is used.
Susan