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ADuM6000: VDD1 3.3V VISO 3.3V: Output Load 5V Boost Converter

Question asked by Patch-3153 on Mar 7, 2016
Latest reply on Mar 21, 2016 by Patch-3153

Hi AD,

 

We are using a single ADuM6000 to provide an isolated (VISO) supply of 3.3V from an input voltage source (VDD1) of 3.3V, with the ADuM6000 setup in Master Mode (self regulating, no slave) - the input 3.3V Power Supply has a slew rate of 1.7V/ms. The output of the ADum6000 is connected to an integrated 5V Output Boost Converter which is designed to supply 25mA at a nominal efficiency of 90%.

 

In typical operation, the ADum6000 is not regulating the isolated output (VISO) to 3.3V, but instead it reaches a peak voltage of 1100mV within 350us, before decreasing to 500mV - the Boost Converter attempts to turn on, but can only regulate its output to about 4Vdc. We have also noted that a fresh power up of the circuit after an extended delay (> 30 min) results in a correct VISO level of 3.3V and a Boost Output of 5V.

 

Our interpretation of this behavior is that there is a subtle timing or threshold effect within our circuit, with the 1100mV level possibly related to the ADuM6000 VISO Regulation Voltage (when the PWM control commences) - the Data Sheet is silent about this level.

 

Thank you for your guidance on the ability of the ADum6000 to supply an Output Load of this nature and the potential areas of the circuit we should concentrate on to understand and remove this undesirable behavior.

 

Best regards,

Colin Campbell

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