advertisement


LDO Reg for ESS9038 DAC

timH

pfm Member
Further adventures in DAC-Land - After fitting ALWSRs to all the vaguely analog parts of the board the next step is fitting some regs for the digital circuits starting off with DVCC. I decided to use LT1763 regs because 1. they were recommended on the DIYAudio thread, 2. they come in a range of fixed output voltages and 3. they're available as samples from Analog Devices :). They come in a SOIC package so I got some SOIC to DIP adapters to mount them on together with the caps etc.
Here is the AD recommended circuit...
B1-A47231-545-F-497-E-AE04-054-AD6-E358-C3.jpg

And here are the pinouts...
DD1-D45-F6-5331-48-EB-9-A6-F-0746-C8854425.jpg


Parts used...
fullsizeoutput-1be7.jpg


First step is to solder the chip to the adapter
fullsizeoutput-1bde.jpg

The blob of solder bridging two pins was deliberate (honest). If you look at the circuit Vout which is pin 1 and Sense which is pin 2 have to be connected, hence the blob
The next step was to fit a ground pin using one of the pins that come with adapters. There are 2 grounds on the chip, pins 3 and 6. I used pin 6.
fullsizeoutput-1bdd.jpg

Yes I know it looks like I've used pin 3 but the rear of these boards are for an even smaller size chip and the numbering is A*** about F***
Now to start fitting the caps. First off the inlet cap. I've used a 1uF Tantalum bead. This goes between pin 8 (input) and pin 6 (ground)
fullsizeoutput-1be0.jpg

If you look carefully you'll see another cunning trick. I've kept one leg of the cap a bit longer to bridge between board hole 8 and chip pin 5. If you look at the circuit again you'll see this is the link between input and SHDN
Now for the output cap - I've used a 10uF Oscon...
fullsizeoutput-1be1.jpg

A couple of cunning tricks here. Pin 3 is also connected to ground through the chip so I've used that. I've also left the leg of the cap long to use as a connection to the main board.
Final cap is the 0.01uF Bypass cap which can be mounted on top of or below the board...
fullsizeoutput-1be4.jpg

I decided to give the board a bit more clearance by taking the plastic spacer off another of the board connectors and sliding it over the one fitted to the ground pin
fullsizeoutput-1be2.jpg

On the home straight now. Just fitted an input wire ready to connect to the main board 5v reg plus a bit of insulation for the output leg of the Oscon
fullsizeoutput-1be6.jpg

That is the reg basically done. Tested it by hooking it up to a USB charger - all ok, phew!
Now comes the REALLY scary part - fitting it to the DAC board which involves drilling a 1mm hole in the main board, scraping off some lacquer from the ground plane and soldering the reg ground pin to that. Then cutting the original track to DVCC, desoldering an smd resistor and wiring the reg output to the pad from that. The reg input is fairly straightforward and just involves connecting the input wire to the output leg of the on-board 5v reg
Here it is...
1-E17303-D-3510-4395-8-C0-C-B68-F6-A55-E226.jpg

The other two red wires are from the ALWSRs feeding AVCC-L and AVCC-R. Anyway miraculously it all works and sound is improved with greater separation between instruments etc etc :D.
It all ended up as a fairly straightforward, if fiddly, project. The LT1763s come in a range of fixed voltages up to 5v and there's also an adjustable version if you want higher voltages but this involves fitting 2 resistors.

Tim
 


advertisement


Back
Top