■ FIGURE 5. Microchip’s DM164120-1
development board.
■ FIGURE 4. A configuration for
driving high-voltage devices.
Cmax = 42/[120 * ln ( 2.1/5.0)]
Cmax = 0.4 µF
back of the motor. This may be a great
way to make a serially controlled
motor — similar to a serially controlled
LCD module. (That also may be the
focus of a future article.)
What I like most about these parts
is the ability to run them off the same
voltage source as the outputs you may
be trying to drive. For example, back in
the November ‘06 column, I showed
some hardware interfaces to the PIC
MCU. One of them showed how to
drive some high-voltage devices using a
bipolar transistor, as shown in Figure 4.
I don’t specify a voltage here, but
instead just state B+. What if that was 12
volts, instead? Using the resistor and
capacitor values I calculated above, I
could control one of these outputs while
also powering the HV PIC MCU from
the same supply. Now, this will require
some better filtering to prevent the large
voltage line from dipping quickly when
the load kicks in, possibly resetting the
PIC MCU. But, that may be easily solved
if the load is fairly clean. This does offer
a simpler solution than trying to add a
separate voltage regulator.
Therefore, I chose a value of 0.1 µF —
since it’s greater than 0.047 µF and less
than 0.4 µF. We now have our PIC
MCU regulator ready to go. One thing
to note with this type of setup is the
amount of current a shunt regulator
draws without anything happening. The
shunt regulator will draw 4 mA, even if
the PIC MCU is in sleep mode and
nothing else is connected. This is not an
ideal setup for battery-operated devices
that need long life. For those devices,
you could use the PIC16F616 version
of this same part, with an external low
quiescent current draw regulator.
The HV parts are really handy,
though, for applications that need a
small component count. I’ve seen
motors with the HV part built into the
DEVELOPMENT SUPPORT
As I mentioned, Microchip’s
PICkit 2 programmer supports these
parts. So does the latest version of my
PICBasic Pro compiler — except for the
PIC12HV615, which has just recently
been released to the public. This is the
eight-pin version of the PIC16HV616,
so it’s got its own set of great applications. Can you imagine that part in a
small surface-mount SOIC package
without the need for a regulator?
I can already think of several applications where that could be squeezed
into a tight sensor package. It could
use an A/D port to read the sensor
element and then send the value back
via a one-wire serial connection. This
Order online at:
www.melabs.com
Development Tools for PIC® MCUs
microEngineering Labs, Inc.
Phone: (719) 520-5323
Fax: (719) 520-1867
Box 60039
Colorado Springs, CO 80960
USB Programmer
for PIC® MCUs
RoHS
Compliant
$119.95
( with accessories)
Programs PIC
MCUs including
low-voltage ( 3.3V)
devices
Includes:
Programmer, USB Cable,
ZIF Programming Adapter for 8 to 40-pin DIP,
Software for Windows 98/Me/NT/2K/XP
EPIC™ Parallel
Port Programmer
starting at $59.95
LAB-X Experimenter Boards
Pre-Assembled Board
Available for 8, 14, 18, 28,
and 40-pin PIC® MCUs
2-line, 20-char LCD Module
9-pin Serial Port
Sample Programs
Full Schematic Diagram
Pricing from $69.95 to $349.95
PICPROTO™ Prototyping Boards
Double-Sided with Plate-Thru Holes
Circuitry for Power Supply and Clock
Large Prototype Area
Boards Available for Most PIC® MCUs
Documentation and Schematic
Pricing from $8.95 to $19.95
BASIC Compilers for PICmicro®
Easy-To-Use BASIC Commands
Windows 9x/Me/2K/XP Interface
PICBASIC™ Compiler $99.95
BASIC Stamp 1 Compatible
Supports most 14-bit Core PICs
Built-In Serial Comm Commands
PICBASIC PRO™ Compiler $249.95
Supports All PICmicro® MCU Families
Direct Access to Internal Registers
Supports In-Line Assembly Language
Interrupts in PICBASIC and Assembly
Built-In USB, I2C, RS-232 and More
Source Level Debugging
See our full range of products, including
books, accessories, and components at:
www.melabs.com
92
May 2007