Does the LM5088-1 require a minimum load?
At light /no load, LM5088 skips HG pulses if a required on-time is less than 'Minimum HG on-time.
I am using LM5088, 60Vin, 44Vout, Max 4.5A, Min 0A. The output is unstable at light / no load. I need to have regulated voltage at full range of current. How can the LM5088 output be stabilized during hysteretic "pulse skipping" mode?
Pulse skipping operation at no load does not mean "Unstable".
You can minimize the pulse skipping operation by adding a dummy load, using smaller inductance of inductor, lowering bandwidth.
Due to its large difference between reference voltage(1.205V) and target output voltage (44V), any small perturbation due to a noise on feedback path will be amplified at the output.
Unstable because output voltage 14V p-p or more at low / no load. Also mean output voltage only 31V. Large enough dummy load solves the problem, but at a price. PCB layout was careful to isolate all analog circuits from high current switching noise. Tried decreasing output capacitance. Mean output voltage closer to 44V, but Vp-p still too large. Am beginning to think that LM5088 unable to achieve low / no current output @ 44V and 4.5A output @ 44V with same circuit and 1V p-p or less. Do you know otherwise?
It is unstable and unregulated. Something is wrong. Share your schematic and board with your local TI engineer. We can help you to find what is wrong.
That's easy. It is the TI LM5088-1 Eval board. I changed the feedback resistors to 66.5K and 1.91K for 44Vout. I changed the output caps to 50V (same capacitances).
I see regulation failure below 100mA load. I am not testing above 500mA load,
Perhaps you can give me contact information for the local TI engineer you refer to.
Did you get the solution for your no load/light load operation? I have the same issue with the LM5088-1 with Vout set for >27V and operate in no load. Vout<27V seem very stable.
Please refer http://e2e.ti.com/support/power_management/non-isolated_dcdc/f/196/t/217498.aspx
I am using LM5088Q-1 for of our application: Requirement is as follows:
Vin= 6V(Cranking) to 36V
I.Load=0.1A to 2.5A
I did try to simulate the circuit in TINA.There were two things which I am not sure about.
1> At low input voltage(6V) I did not see the frequency shift(DFC) To achive High duty cycle and Output did go below 5.7V.
2> At Light Load IL=100mA or less Output voltage rose above set voltageof 5.7V and went around 7V and above.
Please let me know if the issue is with the I.C. or with T.I.N.A Simulation.
Waiting for your reply.
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