15Aug/090
Half-bridge
Here's a simple half-bridge driver based on the LM5106 half-bridge driver with charge pump and programmable dead time coupled with a FDS6986AS dual N mosfet . It's pretty much the sample circuit in the datasheet with an added jumper to select the charge pump source. The current setup allows for driving loads at 30V up to 6.5A continuously while switching at high frequencies (50khz and up). By replacing the chosen dual mosfet with two discrete high power fets up to 100V loads and very high currents can be controlled. The current minimum switching frequency is around 1-2Hz (charge pump self-discharge).
Eagle library, schematic and board available here. Use 25V X5R or X7R capacitors, do not use Y5V/Z5U capacitors.
The second image shows a use for the half-bridge driver; driving a synchronous three-phase hard-disk motor. Commutation is done "blindly" with an adjustable delay between each commutation step. The output to each phase is a trapezoidal waveform. Speeds of up to 20,000 RPM are easily achieved. This design can easily be scaled up for larger motors.
6Aug/090
Simple audio amp
I've often found that I need a basic audio amplifier for smaller projects so I decided once and for all to make a basic low-cost audio amplifier that can be used in a whole range of applications. After some searching I managed to find a surprisingly good monolithic amplifier, the TDA7057AQ. It's good features are that it drives the load differentially (up to 8W), so only a single supply is needed, controls both left and right volume logarithmically from a single-channel potentiometer and mutes at very low volumes, has a very small number of required additional components, has a reasonable voltage range and is surprisingly cheap. It is limited in that the output can't swing very close to the rails, is limited to 8W per channel and can't operate above 18V, however for most simple solutions these limitations aren't really problematic.
I've made a relatively small board that mostly follows the recommended setup detailed in the datasheet, I've added some more decoupling, the 0603 SMD X5R capacitor is placed directly underneath the IC in an attempt to reduce the risk of oscillation or other strange behavior from PCB lead-inductance (probably not a problem as the IC has a GBW of only around 300kHz). There's also a fuse and a reverse polarity protection diode, use a low forward voltage SMC-case Schottky diode (here's one, though somewhat over dimensioned).
Eagle schematic, board and library for TDA7057AQ available here
