UCD3138A: Device will not power up

We've revised our recommendations on reset to use a 2200 ohm resistor with whatever the same capacitor was recommended with the 220 ohm resistor.  We did this because some power supplies come up slow and sloppy with ups and downs, which doesn't do a good job for reset.  The UCD has a power on reset built in, so if the power supply comes up quickly and neatly, it should start anyway. 

Since there is a resistor, you should try pulling the reset end down to ground and release it to see if that helps.  

There are some other questions and potential issues with power up that I will mention:

Make sure that other pins are not powered up before the device is.  This will also interfere with the power on reset by leaking power into the device.

It's also possible that the PMBus interface isn't hooked up correctly, and the device is actually working correctly. Look at the signals on the PMBus, assuming that is what you are using to communicate, and see what they look like.  

Of course, don't believe the schematic - check on the pins to make sure that the proper voltages are present on the power and ground pins.  

You should see a pretty accurate 1.8 volts on the BP18 pin.  

Hi Viktorija,

What exactly it does? How much current it draws(consumes)?
Can you try to ramp VCC up faster and see what happens?
Can it communicate? Is it in ROM mode?

The R value should be 2.2 KOhms and C value should be 2.2 uF for reset pin.

http://www.ti.com/lit/an/slua779b/slua779b.pdf  (Page 23).

Regards,