Hi guys, I am trying to use a TPS61165, using the Evaluation Module, to drive a string of LED's.
I have tried modulating the CTRL input with a 32KHz PWM signal but, from what I can see, the chip enters startup mode on each rising edge of CTRL.
Since this takes 4ms I get no output. Reducing the PWM frequency confirms my thoughts and I can see the time required for startup.
Using the Easyscale protocol on the control pin is erratic at best, even with the USB Interface Adaptor supplied with the Evaluation Module.
Sometimes it works very well, othertimes I get no ACK and have to go through a complete restart to get things to happen. Sometimes even a complete restart does not work, but persevering eventually gets things to work again - for a while.
I am using an Atmel tiny25 programmed in 'C' to generate the required sequences and have verified all pulse widths with a digital storage scope. The waveforms have been captured and saved as pdf docs for perusal.
Below is the email I sent to TI, but have had no response as yet - it is that time of year after all.
Has anyone ever got this to work, in either mode ? I would appreciate any pointers.
Email - as sent to TI
I am using a TPS61165 boosting from 12V to 35V driving a string of LED’s at 75mA.
I have tried using PWM at 32KHZ to the control pin but get some funny results.
It appears that the startup period of 4ms is involved, so this frequency of PWM cannot work.
I decided to try the digital control to the CTRL pin and due to your generous donation of an Evaluation Module could try this out.
It works, most of the time, but is erratic. Some times it’s OK other times it just fails.
I programmed an AVRTiny25 to emulate your control signals and do not get the same response.
I have attached scope captures of what I am sending and what I get back for you to see.
My scope is a Tektronix TDS360 which has the capability of storing waveforms to disk (Very Useful)
Image TEK13 is an overview showing the initialization and the command sequence being delivered to the CTRL pin.
To give you some timings on TEK13, The initial low pulse is 2.7ms, following high is 190us, following low is 300us, following high is 2.74ms.
Image TEK12 is an exploded view of the actual command bytes as seen in TEK13 as a bit of a mush towards the right hand side.
Timing on TEK12 to give you some scale, the second low pulse is 5us. The command code is 0 and ACK is requested.
As you can see there is no acknowledge to the command byte sequence.
I have run this in a continuous loop and never get an acknowledge !!
Can you please help, I would love to go this route, but if I cannot get this to work, I am going to have to find an alternative.
Regards,
0878.TEK00012.pdf6888.TEK00013.pdf
Dave Neale (Technical and Manufacturing Director)
Revelation Designs (Pty) Ltd.
+27 (0)11 312 0866
