WEBENCH® Tools/TPS55340: Design from WorkBench doesn not work for us..

Dear Helen

Tank you for your reply.

Adding the capacitor did help but it did not resolve our issues.

Let me explain what we see:

First, we have created a simulation board that includes all parts from Q1 to the right (on the attached 7853.Boost.PDF).

Supplying 6V to L1, using 2200 uF instead of 4700uf as C4.

Enable we are supplying 3.3 VDC.

We are measuring the Voltage on C4 and monitoring it also using a scope.

We did add 10uF ceramic capacitor between leg 3 of D1 and the ground.

Our problems:

1. The performance of the boost is not constant.

1.1 At times when we give enable to leg 3 the voltage goes up only to 6.5 or 7 V and stopes (we expect it to ramp up to 18.4 V).

1.2 At times it ramps up slowly

1.3 At times it ramps up fast but does not stop at 20 V we saw it ramps to 25V and we stopped the enable to protect the circuit.

1.4 At times we give it enable and nothing happens.

2. we have few questions:

2.1 Leg #5 sync do we need to connect it to the ground or it should be left unconnected (we are not using external clock).

2.2 Leg #4 SS what is the relationship between the capacitance to the ground and the parts charge speed?

After writing the above we have decided to try using 6V as enable. We have started to see a much more stable operation of the device.

The only problem we see is that the voltage over shuts to 25V when according to the calculation it should get to 18.41 V.

Appreciate your quick response

Amir