Intelligent
Power Supply
Design
Tips ‘n Tricks
M
Tips ‘n Tricks
Table of Contents
Tips ‘N Tricks Introduction ....................................... 1
TIP #1:
TIP #2:
TIP #3:
TIP #4:
TIP #5:
TIP #6:
TIP #7:
TIP #8:
TIP #9:
TIP #10:
TIP #11:
TIP #12:
TIP #13:
TIP #14:
TIP #15:
TIP #16:
Soft-Start Using a PIC10F200..................... 2
A Start-Up Sequencer ................................. 5
A Tracking and Proportional Soft-Start
of Two Power Supplies................................ 8
Creating a Dithered PWM Clock ............... 11
Using a PIC® Microcontroller as a Clock
Source for a SMPS PWM Generator......... 13
Current Limiting Using the MCP1630........ 15
Using a PIC® Microcontroller for Power
Factor Correction....................................... 18
Transformerless Power Supplies .............. 21
An IR Remote Control Actuated AC
Switch for Linear Power Supply
Designs ..................................................... 24
Driving High Side FETs ............................. 26
Generating a Reference Voltage with
a PWM Output.......................................... 28
Using Auto-Shutdown CCP ....................... 30
Generating a Two-Phase Control
Signal ........................................................ 33
Brushless DC Fan Speed Control ............. 35
High Current Delta-Sigma Based
Current Measurement Using a Slotted
Ferrite and Hall Effect Device.................... 40
Implementing a PID Feedback Control
in a PIC12F683-Based SMPS Design....... 43
© 2006 Microchip Technology Inc.
DS41283A-page i
Tips ‘n Tricks
Table of Contents (continued)
TIP #17:
TIP #18:
TIP #19:
TIP #20:
TIP #21:
An Error Detection and Restart
Controller ...................................................46
Data-Indexed Software State Machine......48
Execution Indexed Software
State Machine ...........................................51
Compensating Sensors Digitally................54
Using Output Voltage Monitoring to
Create a Self-Calibration Function ............56
DS41283A-page ii
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
TIPS ‘N TRICKS INTRODUCTION
Microchip continues to provide innovative
products that are smaller, faster, easier-to-use and
more reliable. PICmicro® microcontrollers (MCUs)
are used in a wide range of everyday products
from washing machines, garage door openers and
television remotes to industrial, automotive and
medical products.
While some designs such as Switch Mode Power
Supplies (SMPS) are traditionally implemented
using a purely analog control scheme, these
designs can benefit from the configurability and
intelligence that can only be realized by adding a
microcontroller.
This document showcases several examples in
which a PICmicro microcontroller may be used to
increase the functionality of a design with a
minimal increase in cost.
Several of the tips provide working software
examples or reference other documents for more
information. The software and referenced
documents can be found on the CD included with
this booklet, or on the Microchip Technology web
site at www.microchip.com.
© 2006 Microchip Technology Inc.
DS41283A-page 1
Tips ‘n Tricks
TIP #1
Soft-Start Using a PIC10F200
Almost all power supply controllers are equipped
with shutdown inputs that can be used to disable
the MOSFET driver outputs. Using Pulse Width
Modulation (PWM), the amount of time the power
supply is allowed to operate can be slowly
incremented to allow the output voltage to slowly
rise from 0% to 100%.
FIGURE 1-1:
SOFT-START CIRCUIT SCHEMATIC
VDD
0.1 μF
5
On/Off
Control
Input
1
GP0
GP1
3
Shutdown
PWM Output
10 kΩ
N.C. X
6
GP3
GP2
4
X N.C.
2
Note: Assumes SOT-23 packaging.
This technique is called soft-start and is used to
prevent the large inrush currents that are
associated with the start-up of a switching power
supply.
DS41283A-page 2
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
GP0 on the PIC® MCU is used to enable or disable
the soft-start. Once enabled, the on-time of the
PWM signal driving the shutdown output will
increase each cycle until the power supply is fully
on.
During the PIC MCU Power-on Reset, the PWM
output (GP1) is initially in a high-impedance state.
A pull-down resistor on the PWM output ensures
the power supply will not unexpectedly begin
operating.
FIGURE 1-2:
TIMING DIAGRAM
PWM
Output Voltage
100%
0%
It is important to note that this type of soft-start
controller can only be used for switching regulators
that respond very quickly to changes on their
shutdown pins (such as those that do cycle-bycycle limiting). Some linear regulators have activelow shutdown inputs, however, these regulators do
not respond fast enough to changes on their
shutdown pins in order to perform soft-start.
© 2006 Microchip Technology Inc.
DS41283A-page 3
Tips ‘n Tricks
Example software is provided for the PIC10F200
which was taken from TB081. Please refer to
TB081, “Soft-Start Controller For Switching Power
Supplies” (DS91081) for more information.
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
DS41283A-page 4
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
TIP #2
A Start-Up Sequencer
Some new devices have multiple voltage
requirements (e.g., core voltages, I/O voltages,
etc.). The sequence in which these voltages rise
and fall may be important.
By expanding on the previous tip, a start-up
sequencer can be created to control two output
voltages. Two PWM outputs are generated to
control the shutdown pins of two SMPS
controllers. Again, this type of control only works
on controllers that respond quickly to changes
on the shutdown pin (such as those that do
cycle-by-cycle limiting).
FIGURE 2-1:
MULTIPLE PWM OUTPUT SOFT-START
CONTROLLER
VDD
0.1 μF
UnderVoltage
Lockout
Shutdown
5
1
6
GP0/CIN+ GP1
GP3
GP2
3
4
2
PWM Output #1
10 kΩ
PWM Output #2
10 kΩ
Note: Assumes SOT-23 packaging.
© 2006 Microchip Technology Inc.
DS41283A-page 5
Tips ‘n Tricks
This design uses the PIC MCU comparator to
implement an under-voltage lockout. The input on
the GP0/CIN+ pin must be above the internal 0.6V
reference for soft-start to begin, as shown in
Figure 2-2.
Two conditions must be met in order for the soft-start
sequence to begin:
1. The shutdown pin must be held at VDD (logic
high).
2. The voltage on GP0 must be above 0.6V.
Once both start-up conditions are met, the
sequences will delay and PWM #1 will ramp from
0% to 100%. A second delay allows the first voltage
to stabilize before the sequencer ramps PWM #2
from 0% to 100%. All delays and ramp times are
under software control and can be customized for
specific applications. If either soft-start condition
becomes invalid, the circuit will shutdown the
SMPS controllers.
DS41283A-page 6
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
FIGURE 2-2:
TIMING DIAGRAM
V1
V2
PWM1
PWM2
1
1.
2.
3.
4.
5.
2
3
4
5
Start-up conditions met
Initial delay
PWM Ramp #1 complete
Between PWM delay
PWM #2 complete
Example software is provided for the PIC10F200
which was taken from TB093, “Multiple PWM
Output Soft-Start Controller for Switching Power
Supplies” (DS91093).
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
© 2006 Microchip Technology Inc.
DS41283A-page 7
Tips ‘n Tricks
TIP #3
A Tracking and Proportional
Soft-Start of Two Power
Supplies
Expanding on the previous tip, we can also use a
PIC MCU to ensure that two voltages in a system
rise together or rise proportionally to one another,
as shown in Figure 3-1. This type of start-up is
often used in applications with devices that require
multiple voltages (such as I/O and core voltages).
Like the previous two, this tip is designed to control
the shutdown pin of the SMPS controller and will
only work with controllers that respond quickly to
changes on the shutdown pin.
FIGURE 3-1:
TIMING DIAGRAM
VA
Voltage
VB
Time
DS41283A-page 8
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
FIGURE 3-2:
EXAMPLE SCHEMATIC
VDD
Resistor
Divider 2
0.1 μF
VA
Shutdown A
+
VB
-
Resistor
Divider 1
Control
Software
R1
Shutdown B
R2
PIC12F629
Shutdown
The comparator of the PIC MCU is used to
determine which voltage is higher and increases
the on-time of the other output accordingly. The
logic for the shutdown pins is as shown in
Table 3-1.
TABLE 3-1:
SHUTDOWN PIN LOGIC
Case
Shutdown
A
Shutdown
B
High
VA>VB
Low
VB>VA
High
Low
VB> Internal Reference
High
High
To determine if it has reached full voltage, VB is
compared to the internal voltage reference. If VB is
higher, both shutdown outputs are held high.
© 2006 Microchip Technology Inc.
DS41283A-page 9
Tips ‘n Tricks
Resistor Divider 1 should be designed so that the
potentiometer output is slightly higher than the
comparator voltage reference when VB is at full
voltage.
The ratio of resistors in Resistor Divider 2 can be
varied to change the slope at which VA rises.
Pull-down resistors ensure the power supplies will
not operate unexpectedly when the PIC MCU is
being reset.
DS41283A-page 10
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
TIP #4
Creating a Dithered PWM Clock
In order to meet emissions requirements as
mandated by the FCC and other regulatory
organizations, the switching frequency of a power
supply can be varied. Switching at a fixed
frequency produces energy at that frequency. By
varying the switching frequency, the energy is
spread out over a wider range and the resulting
magnitude of the emitted energy at each individual
frequency is lower.
The PIC10F200 has an internal 4 MHz oscillator. A
scaled version of oscillator can be output on a pin
(FOSC/4). The scaled output is 1/4 of the oscillator
frequency (1 MHz) and will always have a 50%
duty cycle. Figure 4-1 shows a spectrum analyzer
shot of the output of the FOSC/4 output.
FIGURE 4-1:
SPECTRUM OF CLOCK OUTPUT BEFORE
DITHERING
10 dB/ REF 20 dBm
Center 1.0 MHz
© 2006 Microchip Technology Inc.
Span 1.8 MHz
DS41283A-page 11
Tips ‘n Tricks
The PIC10F200 provides an Oscillator Calibration
(OSCCAL) register that is used to calibrate the
frequency of the oscillator. By varying the value of
the OSCCAL setting, the frequency of the clock
output can be varied. A pseudo-random sequence
was used to vary the OSCCAL setting, allowing
frequencies from approximately 600 kHz to
1.2 MHz. The resulting spectrum is shown in
Figure 4-2.
FIGURE 4-2:
SPECTRUM OF CLOCK OUTPUT AFTER
DITHERING
10 dB/ REF 20 dBm
Center 1.0 MHz
Span 1.8 MHz
By spreading the energy over a wider range of
frequencies, a drop of more than 20 dB is
achieved.
Example software is provided for the PIC10F200
that performs the pseudo-random sequence
generation and loads the OSCCAL register.
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
DS41283A-page 12
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
TIP #5
Using a PIC® Microcontroller as
a Clock Source for a SMPS PWM
Generator
A PIC MCU can be used as the clock source for a
PWM generator, such as the MCP1630.
PIC® MCU AND MCP1630 EXAMPLE BOOST
APPLICATION
FIGURE 5-1:
VIN
L1
MCP1630
®
PIC
MCU
VIN
VEXT
OSC IN
FB
CS
D1
M1
R1
C1
R2
RSENSE
The MCP1630 begins its cycle when its clock/
oscillator source transitions from high-to-low,
causing its PWM output to go high state. The PWM
pulse can be terminated in any of three ways:
1. The sensed current in the magnetic device
reaches 1/3 of the error amplifier output.
2. The voltage at the Feedback (FB) pin is higher
than the reference voltage (VREF).
3. The clock/oscillator source transitions from
low-to-high.
© 2006 Microchip Technology Inc.
DS41283A-page 13
Tips ‘n Tricks
The switching frequency of the MCP1630 can be
adjusted by changing the frequency of the clock
source. The maximum on-timer of the MCP1630
PWM can be adjusted by changing the duty cycle
of the clock source.
The PIC MCU has several options for providing
this clock source:
• The FOSC/4 pin can be enabled. This will
produce a 50% duty cycle square wave that is
1/4th of the oscillator frequency. TIP #4
provides both example software and information
on clock dithering using the FOSC/4 output.
• For PIC MCUs equipped with a Capture/Compare/PWM (CCP) or Enhanced CCP (ECCP)
module, a variable frequency, variable duty
cycle signal can be created with little software
overhead. This PWM signal is entirely under
software control and allows advanced features,
such as soft-start, to be implemented using
software.
• For smaller parts that do not have a CCP or
ECCP module, a software PWM can be
created. Tips #1 and #2 use software PWM for
soft-start and provide software examples.
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
DS41283A-page 14
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
TIP #6
Current Limiting Using the
MCP1630
FIGURE 6-1:
MCP1630 HIGH-SPEED PWM
VIN
0.1 μA
UVLO
VEXT
OSC IN
0.1 μA
CS
Comp
+
–
VIN
2R
Q
GND
100 kΩ
Q
R
Comp
Latch Truth Table
R
2.7V Clamp
Note 1:
(1)
S
VIN
FB
–
VREF EA
+
VIN
Overtemperature
S
R
Q
0
0
Qn
0
1
1
1
0
0
1
1
1
During overtemperature, VEXT driver is high-impedance.
The block diagram for the MCP1630 high-speed
PWM driver is shown in Figure 6-1. One of the
features of the MCP1630 is the ability to perform
current limiting. As shown in the bottom left corner
of the diagram, the output of the Error Amplifier
(EA) is limited by a 2.7V clamp. Therefore,
regardless of the actual error, the input to the
negative terminal of the comparator (labeled
Comp) is limited to 2.7V÷3 or 0.9V.
© 2006 Microchip Technology Inc.
DS41283A-page 15
Tips ‘n Tricks
It is possible to implement the current limiting by
using a single sense resistor. In this case, the
maximum current would be given by Equation 6-1.
EQUATION 6-1:
IMAX = (0.9V) /RSENSE
For high current applications, this method may be
acceptable. When lower current limits are
required, the size of the sense resistor, RSENSE,
must be increased. This will cause additional
power dissipation. An alternative method for lower
current limits is shown in Figure 6-2.
FIGURE 6-2:
LOW CURRENT LIMITS
VDD
L1
R1
R2
CS Input
+
RSENSE
In this case, the Current Sense (CS) input of the
MCP1630 is biased upward using the R1/R2
resistor divider. The equations for the new current
limit are shown in Equation 6-2.
DS41283A-page 16
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
EQUATION 6-2:
0.9V =
(VDD - IMAX • RSENSE) • R2
R1 + R2
Equation 6-2 can be solved to determine the
values of R1 and R2 that provide the desired
current limit.
© 2006 Microchip Technology Inc.
DS41283A-page 17
Tips ‘n Tricks
TIP #7
Using a PIC® Microcontroller for
Power Factor Correction
In AC power systems, the term Power Factor (PF)
is used to describe the fraction of power actually
used by a load compared to the total apparent
power supplied.
Power Factor Correction (PFC) is used to increase
the efficiency of power delivery by maximizing the
PF.
The basis for most Active PFC circuits is a boost
circuit, shown in Figure 7-1.
FIGURE 7-1:
TYPICAL POWER FACTOR CORRECTION
BOOST SUPPLY
L1
+
-
DS41283A-page 18
D1
M1
+
PWM
C1
VBoost
+
C2
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
The AC voltage is rectified and boosted to voltages
as high as 400 VDC. The unique feature of the PFC
circuit is that the inductor current is regulated to
maintain a certain PF. A sine wave reference
current is generated that is in phase with the line
voltage. The magnitude of the sine wave is
inversely proportional to the voltage at VBoost.
Once the sine wave reference is established, the
inductor current is regulated to follow it, as shown
in Figure 7-2.
FIGURE 7-2:
DESIRED AND ACTUAL INDUCTOR
CURRENTS
Reference
Inductor
Current
© 2006 Microchip Technology Inc.
Actual
Inductor
Current
DS41283A-page 19
Tips ‘n Tricks
A PIC MCU has several features that allow it to
perform power factor correction.
• The PIC MCUs CCP module can be used to
generate a PWM signal that, once filtered, can
be used to generate the sine wave reference
signal.
• The PIC Analog-to-Digital (A/D) converter can
be used to sense VBoost and the reference
sine wave can be adjusted in software.
• The interrupt-on-change feature of the PIC
MCU input pins can be used to allow the PIC
MCU to synchronize the sine wave reference to
the line voltage by detecting the zero crossings.
• The on-chip comparators can be used for
driving the boost MOSFET(s) using the PWM
sine wave reference as one input and the actual
inductor current as another.
DS41283A-page 20
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
TIP #8
Transformerless Power Supplies
When using a microcontroller in a line-powered
application, such as the IR remote control actuated
AC switch described in TIP #9, the cost of building
a transformer-based AC/DC converter can be
significant. However, there are transformerless
alternatives which are described below.
Capacitive Transformerless Power Supply
FIGURE 8-1:
CAPACITIVE POWER SUPPLY
L
VOUT
IIN
D1
5.1V
N
C2
470 uF
IOUT
C1
R1
.47u 250V
470Ω 1/2W
© 2006 Microchip Technology Inc.
D2
DS41283A-page 21
Tips ‘n Tricks
Figure 8-1 shows the basics for a capacitive power
supply. The Zener diode is reverse-biased to
create the desired voltage. The current drawn by
the Zener is limited by R1 and the impedance of
C1.
Advantages:
• Significantly smaller than a transformer-based
power supply
• Lower cost than a transformer-based or
switcher-based power supply
• Power supply is more efficient than a resistive
transformerless power supply
Disadvantages:
• Not isolated from the AC line voltage which
introduces safety issues
• Higher cost than a resistive power supply
because X2 rated capacitors are required
More information on either of these solutions,
including equations used for calculating circuit
parameters, can be found in AN954,
“Transformerless Power Supplies: Resistive and
Capacitive” (DS00954) or in TB008,
“Transformerless Power Supply” (DS91008).
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
DS41283A-page 22
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
Resistive Power Supply
FIGURE 8-2:
RESISTIVE POWER SUPPLY
L
VOUT
IIN
D1
5.1V
C2
IOUT
N
R1
R2
1KΩ 5W 1KΩ 5W
D2
The resistive power supply works in a similar
manner to the capacitive power supply by using a
reversed-biased Zener diode to produce the
desired voltage. However, R1 is much larger and
is the only current limiting element.
Advantages:
• Significantly smaller than a transformer-based
power supply
• Lower cost than a transformer-based power
supply
• Lower cost than a capacitive power supply
Disadvantages:
• Not isolated from the AC line voltage which
introduces safety issues
• Power supply is less energy efficient than a
capacitive power supply
• More energy is dissipated as heat in R1
© 2006 Microchip Technology Inc.
DS41283A-page 23
Tips ‘n Tricks
TIP #9
An IR Remote Control Actuated
AC Switch for Linear Power
Supply Designs
Many line-powered applications (audio amplifiers,
televisions, etc.) can be turned on and off using an
infrared remote control. This requires that some
components be energized to receive the remote
signals even when the device is off. Low current
PIC® microcontrollers are best in this application.
Figure 9-1 shows an example circuit layout.
FIGURE 9-1:
PIC® MCU INFRARED RECEIVER
SCHEMATIC
.
Q1
Load
AC IN
R1
C2
U1
+
Do
-
DS41283A-page 24
Load
+5V C1
VDD
GP0/C+ GP2/COUT
GP1/C- GP2/MCLR
VSS
R2
Zero Crossing
Detection
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
The PIC10F200 has several features that make it
ideally suited for this type of application:
• Extremely low operating and standby current
(350 μA operating, 0.1 μA when asleep)
• Input/Output pins with configurable pull-ups and
reset-on-change capability
• High sink/source ability (+/- 25 mA) allows
driving external devices, such as the IR
receiver, directly from the I/O pin
• Ability to use a low-cost resistive power supply
• Small form factor (SOT-23 packaging)
TB094, “Dimming AC Incandescent Lamps Using
A PIC10F200” (DS91094) provides both software
and hardware examples of an infrared controller.
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
© 2006 Microchip Technology Inc.
DS41283A-page 25
Tips ‘n Tricks
TIP #10 Driving High Side FETs
In applications where high side N channel FETs
are to be driven, there are several means for
generating an elevated driving voltage. One very
simple method is to use a voltage doubling charge
pump as shown in Figure 10-1.
Method 1
FIGURE 10-1: TYPICAL CHANGE PUMP
VDD
D1
VOUT max =
2 * VDD - 2 * VDIODE
CLKOUT
CPUMP D2
CFILTER
The PIC MCU’s CLKOUT pin toggles at 1/4 of the
oscillator frequency. When CLKOUT is low, D1 is
forward biased and conducts current, thereby
charging CPUMP. After CLKOUT is high, D2 is
forward biased, moving the charge to CFILTER. The
result is a voltage equal to twice the VDD minus two
diode drops. This can be used with a PWM or any
other I/O pin that toggles.
In Figure 10-2, a standard FET driver is used to
drive both the high and low side FETs by using the
diode and capacitor arrangement.
DS41283A-page 26
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
Method 2
FIGURE 10-2: SCHEMATIC
+5
D1
+12
FET Driver
D2
M1
PWM1
C2
U1A
L1
C1
.
PWM2
U1B
M2
The +5V is used for powering the microcontroller.
Using this arrangement, the FET driver would
have approximately 12 + (5 – VDIODE) – VDIODE
volts as a supply and is able to drive both the high
and low side FETs.
The circuit above works by charging C1 through
D1 to (5V – VDIODE) while M2 is on, effectively
connecting C1 to ground. When M2 turns off and
M1 turns on, one side of C1 is now at 12V and the
other side is at 12V + (5V –VDIODE). The D2 turns
on and the voltage supplied to the FET driver is
12V + (5V – VDIODE) – VDIODE.
© 2006 Microchip Technology Inc.
DS41283A-page 27
Tips ‘n Tricks
TIP #11 Generating a Reference Voltage
with a PWM Output
FIGURE 11-1: LOW-PASS FILTER
MCP6001
CCP1
Analog
Out
+
R
C
-
A PWM signal can be used to create a Digital-toAnalog Converter (DAC) with only a few external
components. Conversion of PWM waveforms to
analog signals involves the use of an analog lowpass filter. In order to eliminate unwanted
harmonics caused by a PWM signal, the PWM
frequency (FPWM) should be significantly higher
than the bandwidth (FBW) of the desired analog
signal. Equation 11-1 shows this relation.
EQUATION 11-1:
FPWM = K•FBW
Where harmonics decrease as K increases
R and C are chosen based on the following
equation:
EQUATION 11-2:
RC = 1/(2•π•FBW)
Where harmonics decrease as K increases
DS41283A-page 28
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
Choose the R value based on drive capability and
then calculate the required C value. The
attenuation of the PWM frequency for a given RC
filter is shown in Equation 11-3.
EQUATION 11-3:
Att(dB) = -10 • log [1 + (2π • FPWM • RC) 2]
If the attenuation calculated in Equation 11-3 is not
sufficient, then K must be increased in
Equation 11-1.
In order to sufficiently attenuate the harmonics, it
may be necessary to use small capacitor values or
large resistor values. Any current draw will effect
the voltage across the capacitor. Adding an op
amp allows the analog voltage to be buffered and,
because of this, any current drawn will be supplied
by the op amp and not the filter capacitor.
For more information on using a PWM signal to
generate an analog output, refer to AN538, “Using
PWM to Generate Analog Output” (DS00538).
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
© 2006 Microchip Technology Inc.
DS41283A-page 29
Tips ‘n Tricks
TIP #12 Using Auto-Shutdown CCP
PWM Auto-Shutdown
Several of Microchip’s PIC® MCUs, such as the
PIC16F684, PIC16F685 and PIC16F690, have a
PWM auto-shutdown feature. When autoshutdown is enabled, an event can terminate the
current PWM pulse and prevent subsequent
pulses unless the event is cleared. The ECCP can
be setup to automatically start generating pulses
again once the event clears.
FIGURE 12-1: PWM AUTO-SHUTDOWN TIMING
PWM Signal
Shutdown
Event
Figure 12-1 shows an example timing for the PWM
auto-shutdown. When the shutdown event occurs,
the current pulse is immediately terminated. In this
example, the next two pulses are also terminated
because the shutdown event had not been cleared
by the beginning of the pulse period. After the
event has cleared, pulses are allowed to resume,
but only at the beginning of a pulse period.
DS41283A-page 30
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
Using Auto-Shutdown to Create a Boost
Supply
By using the auto-shutdown feature, a very simple
SMPS can be created. Figure 12-2 shows an
example boost power supply.
FIGURE 12-2: BOOST POWER SUPPLY
VIN
L1
Internal to PIC® MCU
PWM
Module
out
R1
Q1
VOUT
C1
D1
R2
+
R3
This power supply configuration has several
unique features:
1. The switching frequency is determined by
the PWM frequency and, therefore, can be
changed at any time.
2. The maximum on-time is determined by the
PWM duty cycle and, therefore, can be
changed any time. This provides a very easy
way to implement soft-start.
3. On PIC MCUs that have a programmable
reference module, the output voltage can be
configured and changed at any time.
© 2006 Microchip Technology Inc.
DS41283A-page 31
Tips ‘n Tricks
The topology can also be re-arranged to create
other types of power supplies.
Example software is provided for the PIC16F685
(but can be adapted to any PIC MCU with the
ECCP module). The software configures the PWM
and comparator modules as shown in Figure 12-2.
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
DS41283A-page 32
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
TIP #13 Generating a Two-Phase Control
Signal
Power supplies using a push-pull topology or with
multiple switching components require a two-phase
control signal as shown in Figure 13-1.
FIGURE 13-1: TWO-PHASE CONTROL SIGNAL
P1A
P1B
It is possible to produce this type of control signal
with two out-of-phase square waves using a PIC
MCU with an ECCP module.
FIGURE 13-2: TWO-PHASE CONTROL SIGNAL
SCHEMATIC
P1A
PIC® MCU
P1B
© 2006 Microchip Technology Inc.
DS41283A-page 33
Tips ‘n Tricks
In order to configure the ECCP to produce this
type of output:
1. Configure the ECCP in half H-bridge
configuration PWM pulse with both outputs
active-high.
2. Set the duty cycle register (CCPR1L) with the
maximum duty cycle of 50%.
3. Change the programmable dead-time generator
to reduce the pulse width to the desired value.
The programmable dead-time generator has a 7-bit
resolution and, therefore, the resulting pulses will
only have a 7-bit resolution. Each pulse will have a
50% duty cycle, less the dead time.
Using an internal 4 MHz clock produces 31 kHz
output pulses, and using a 20 MHz crystal would
produce 156 kHz output. The frequency of the
output could be increased with a loss in resolution.
Example software is provided for the PIC16F684,
but this tip is applicable to all PIC MCUs with
ECCP modules.
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
DS41283A-page 34
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
TIP #14 Brushless DC Fan Speed
Control
There are several methods to control the speed of
a DC brushless fan. The type of fan, allowable
power consumption and the type of control desired
are all factors in choosing the appropriate type.
FIGURE 14-1: LOW-SIDE PWM DRIVE
12V
PWM Drive
FIGURE 14-2: HIGH-SIDE PWM DRIVE
12V
12V
PWM Drive
© 2006 Microchip Technology Inc.
DS41283A-page 35
Tips ‘n Tricks
Method 1 – Pulse Width Modulation
As shown in Figure 14-1 and Figure 14-2, a simple
PWM drive may be used to switch a two-wire fan
on and off. While it is possible to use the circuit in
Figure 14-1 without a high-side MOSFET driver,
some manufacturers state that switching on the
low side of the fan will void the warranty.
Because of this, it is necessary to switch the high
side of the fan in order to control the speed. The
simplest type of speed control is ‘on’ or ‘off’.
However, if a higher degree of control is desired,
PWM can be used to vary the speed of the fan.
For 3-wire fans, the tachometer output will not be
accurate if PWM is used. The sensor providing the
tachometer output on 3-wire fans is powered from
the same supply as the fan coils, thus using a
PWM to control fan speed will render the fan’s
tachometer inaccurate.
One solution to this is to use a 4-wire fan which
includes both the tachometer output and a drive
input. Figure 14-3 shows a diagram of a 4-wire fan.
DS41283A-page 36
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
FIGURE 14-3: TYPICAL 4-WIRE FAN
V+
Drive
TACH
TACH
GND
A 4-wire fan allows speed to be controlled using
PWM via the Drive line. Since power to the
tachometer sensor is not interrupted, it will
continue to output the correct speed.
© 2006 Microchip Technology Inc.
DS41283A-page 37
Tips ‘n Tricks
Method 2 – Linear Control
When using PWM, the voltage will vary between a
maximum and a minimum, however, is it also
possible to use a linear method to control fan
speed, as shown in Figure 14-4.
FIGURE 14-4: LINEAR CONTROL DRIVE
12V
VREF
+
Out
-
R1
R2
The voltage applied at the non-inverting terminal of
the op amp is used to vary the voltage across the
op amp. The non-inverting terminal voltage can be
produced by a Digital-to-Analog Converter (DAC)
or by the method shown in TIP #11.
DS41283A-page 38
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
When using this method, care must be taken to
ensure that the fan voltage is not too low or the fan
will stop spinning. One advantage this method has
over PWM is that the tachometer output will
function properly on 3-wire fans. The
disadvantage, however, is that it often offers less
speed control. For example, a 12V fan will not spin
below 8V, so a range of only 4V is available for
speed control. A 5V fan will not spin below 4V and
so the control range is only 1V, which is often
unacceptable. Another disadvantage is the power
consumption of the circuit. The transistor will
dissipate more power than the PWM method.
© 2006 Microchip Technology Inc.
DS41283A-page 39
Tips ‘n Tricks
TIP #15 High Current Delta-Sigma Based
Current Measurement Using a
Slotted Ferrite and Hall Effect
Device
Many current sensors rely on ferrite cores.
Nonlinearity in the ferrite can lead to inaccurate
results, especially at high currents. One way to
avoid the nonlinearities is to keep the net flux in the
ferrite near zero. Consider the circuit in Figure 15-1.
FIGURE 15-1: HALL EFFECT CURRENT MEASUREMENT
SCHEMATIC
PIC® MCU
+
MOSFET Driver
VDD
VREF
Hall Effect
Sensor
The Hall Effect sensor output is proportional to the
current being measured. When IIN = 0 amps, the
output of the sensor will be VDD/2. A current
passing through the sensor in one direction will
increase the output of the sensor, and a current in
the other direction will decrease the output of the
sensor.
DS41283A-page 40
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
The output of the comparator is used to drive a coil
of wire wound around the ferrite core. This coil of
wire will be used to create flux in the opposite
direction as the flux imposed in the core.
FIGURE 15-2: FLUX DIRECTIONS
Flux due to input current
IIN
Flux due to
driven coil
The net flux in the core should be approximately
zero. Because the flux will always be very near
zero, the core will be very linear over the small
operating range.
When IIN = 0, the output of the comparator will have
an approximate 50% duty cycle. As the current
moves one direction, the duty cycle will increase.
As the current moves the other direction, the duty
cycle will decrease. By measuring the duty cycle of
the resulting comparator output, we can determine
the value of IIN.
© 2006 Microchip Technology Inc.
DS41283A-page 41
Tips ‘n Tricks
Finally, a Delta-Sigma ADC can be used to
perform the actual measurement. Features such
as comparator sync and Timer1 gate allow the
Delta-Sigma conversion to be taken care of
entirely in hardware. By taking 65,536 (2^16)
samples and counting the number of samples that
the comparator output is low or high, we can obtain
a 16-bit A/D result.
Example schematic and software are provided for
the PIC12F683 in both C and Assembly.
For more information on using a PIC® MCU to
implement a Delta-Sigma converter, please refer
to AN700, “Make a Delta-Sigma Converter Using a
Microcontroller’s Analog Comparator Module”
(DS00700), which includes example software.
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
DS41283A-page 42
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
TIP #16 Implementing a PID Feedback
Control in a PIC12F683-Based
SMPS Design
Simple switching power supplies can be controlled
digitally using a Proportional Integral Derivative
(PID) algorithm in place of an analog error
amplifier and sensing the voltage using the
Analog-to-Digital Converter (ADC).
FIGURE 16-1: SIMPLE PID POWER SUPPLY
+5V
VSENSE
VDD
CCP1
GP5
VSS
PIC12F683
AN0
GP1
GP3
GP4
+5V
R1
Q1
C2
L1
D2
VOUT
VSENSE
+
R2
C1
R3
The design in Figure 16-1 utilizes an 8-pin
PIC12F683 PIC® MCU in a buck topology. The
PIC12F683 has the basic building blocks needed
to implement this type of power supply: an A/D
converter and a CCP module.
© 2006 Microchip Technology Inc.
DS41283A-page 43
Tips ‘n Tricks
FIGURE 16-2: PID BLOCK DIAGRAM
PIC® Microcontroller
A/D Voltage
Sense
+
Desired
Value
-
Software
PID
Routine
CCP
Duty Cycle
The A/D converter is used to sense the output
voltage for this particular application, VDD is used
as the reference to the A/D converter. If desired, a
more accurate reference could be used. The
output voltage is subtracted from the desired
value, creating an error value.
This error becomes the input to the PID routine.
The PID routine uses the error voltage to
determine the appropriate duty cycle for the output
drive. The PID constants are weighted so that the
main portion of the control is proportional and
integral. The differential component is not
essential to this system and is not used.
Furthermore, the PID constants could be
optimized if a particular type of transient response
was desired, or if a predictable transient load was
to be connected.
Finally, the CCP module is used to create a PWM
signal at the chosen frequency with the proper
duty cycle.
DS41283A-page 44
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
Example software is provided for the PIC12F683
using the schematic in Figure 16-1.
The following application notes are related to PID
control algorithms and all include example
software:
• AN258, “Low Cost USB Microcontroller
Programmer The Building of the PICkit® 1 Flash
Starter Kit” (DS00258)
• AN937, “Implementing a PID Controller Using a
PIC18 MCU” (DS00937)
• AN964, “Software PID Control of an Inverted
Pendulum Using the PIC16F684” (DS00937)
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
© 2006 Microchip Technology Inc.
DS41283A-page 45
Tips ‘n Tricks
TIP #17 An Error Detection and Restart
Controller
An error detection and restart controller can be
created by combining TIP #18 and TIP #19. The
controller uses the PIC® microcontroller (MCU)
Analog-to-Digital Converter (ADC) for making
voltage and current measurements. Input voltage,
input current, output voltage, output current,
temperature and more can all be measured using
the A/D converter. The on-board comparators are
used for monitoring faster signals, such as output
current, ensuring that they do not exceed
maximum allowable levels. Many PIC MCUs have
internal programmable comparator references,
simplifying the circuit.
FIGURE 17-1: BLOCK DIAGRAM
Input Voltage
Input Current
Status
Indicators
DS41283A-page 46
Output Voltage
PIC® MCU
Output Voltage
Temperature
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
Using a PIC MCU as a controller allows for a
greater level of intelligence in system monitoring.
Rather than a single event causing a shutdown, a
combination of events can cause a shutdown. A
certain number of events in a certain time frame or
possibly a certain sequence of events could be
responsible for a shutdown.
The PIC MCU has the ability to restart the supply
based on the shutdown event. Some events (such
as overcurrent) may call for immediate restart,
while other events (such as overtemperature) may
require a delay before restarting, perhaps
monitoring other parameters and using those to
determine when to restart.
It is also possible to build this type of error
detection and restart controller into many of the
tips listed within this guide.
© 2006 Microchip Technology Inc.
DS41283A-page 47
Tips ‘n Tricks
TIP #18 Data-Indexed Software State
Machine
A state machine can be used to simplify a task by
breaking the task up into smaller segments. Based
on a state variable, the task performed or the data
used by the state machine can be changed. There
are three basic types of state machines: dataindexed, execution indexed and a hybrid of the
two. This tip will focus on a data-indexed state
machine.
The data-indexed state machine is ideal for
monitoring multiple analog inputs with the Analogto-Digital Converter (ADC). The state variable in
these state machines determines which data is
acted upon. In this case, the tasks of changing the
ADC channel, storing the current result and
starting a new conversion are always the same.
A very simple flow diagram for a data-indexed
state machine is shown in Figure 18-1.
DS41283A-page 48
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
FIGURE 18-1: DATA-INDEXED STATE MACHINE
FLOWCHART
ADC Interrupt
Load ADC control register
with CONSTANT[i] to
change ADC channel
Store current measurement
data to ADCDATA[i]
registers
Start next ADC conversion
Increment state variable,
checking for rollover
End ADC Interrupt
Service Routine
As shown in Figure 18-1, a constant array
(CONSTANT[i]) can be created to store the values
to be loaded into the ADC control register to
change the ADC channel. Furthermore, a data
array (ADCDATA[i]) can be used to store the
results of the ADC conversion. Finally, the next
conversion is started and the logic required to
increment and bind the state variable is executed.
© 2006 Microchip Technology Inc.
DS41283A-page 49
Tips ‘n Tricks
This particular example used the ADC interrupt to
signal when a conversion has completed, and will
attempt to take measurements as quickly as
possible. A subroutine could also be built to
perform the same task, allowing the user to call the
subroutine when needed.
Example software is provided using the
PIC16F676 and RS-232 to monitor several ADC
channels.
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
DS41283A-page 50
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
TIP #19 Execution-Indexed Software
State Machine
Another common type of state machine is the
execution-indexed state machine. This type of
state machine uses a state variable in order to
determine what is executed. In C, this can be
thought of as the switch statement structure as
shown in Example 19-1.
EXAMPLE 19-1: EXAMPLE USING SWITCH STATEMENT
SWITCH (State)
{
CASE 0:IF (in_key()==5)THEN state = 1;
Break;
CASE 1:IF (in_key()==8)THEN State = 2;
Else State = 0;
Break;
CASE 2:IF (in_key()==3)THEN State = 3;
Else State = 0;
Break;
CASE 3:IF (in_key()==2)THEN UNLOCK();
Else State = 0;
Break;
}
© 2006 Microchip Technology Inc.
DS41283A-page 51
Tips ‘n Tricks
Each time the software runs through the loop, the
action taken by the state machine changes with
the value in the state variable. By allowing the
state machine to control its own state variable, it
adds memory, or history, because the current state
will be based on previous states. The
microcontroller is able to make current decisions
based on previous inputs and data.
In assembly, an execution-indexed state machine
can be implemented using a jump table.
EXAMPLE 19-2: EXAMPLE USING A JUMP TABLE
MOVFW state
ADDWF PCL,f
GOTO
GOTO
GOTO
GOTO
GOTO
GOTO
state0
state1
state2
state3
state4
state5
DS41283A-page 52
;load state into w
;jump to state
;number
;state 0
;state 1
;state 2
;state 3
;state 4
;state 5
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
In Example 19-2, the program will jump to a GOTO
statement based on the state variable. The GOTO
statement will send the program to the proper
branch. Caution must be taken to ensure that the
variable will never be larger than intended. For
example, six states (000 to 101) require a threebit state variable. Should the state variable be set
to an undefined state (110 to 111), program
behavior would become unpredictable.
Means for safeguarding this problem include:
• Mask off any unused bits of the variable. In the
above example, ANDLW b'00000111' will
ensure that only the lower 3 bits of the number
contain a value.
• Add extra cases to ensure that there will always
be a known jump. For example in this case, two
extra states must be added and used as error
or Reset states.
© 2006 Microchip Technology Inc.
DS41283A-page 53
Tips ‘n Tricks
TIP #20 Compensating Sensors Digitally
Many sensors and references tend to drift with
temperature. For example, the MCP9700
specification states that its typical is +/-0.5°C and its
max error is +/- 4°C.
FIGURE 20-1: MCP9700 ACCURACY
6.0
Accuracy (°C)
4.0
Spec. Limit
2.0
0.0
-2.0
+ V
Average
- V
-4.0
-55 -35 -15
5
25 45 65
Temperature (°C)
85
105 125
Figure 20-1 shows the accuracy of a 100 sample
lot of MCP9700 temperature sensors. Despite the
fact that the sensor’s error is nonlinear, a PIC®
microcontroller (MCU) can be used to compensate
the sensor’s reading.
Polynomials can be fitted to the average error of
the sensor. Each time a temperature reading is
received, the PIC MCU can use the measured
result and the error compensation polynomials to
determine what the true temperature is.
DS41283A-page 54
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
FIGURE 20-2: MCP9700 AVERAGE ACCURACY AFTER
COMPENSATION
0.3
Accuracy (°C)
0.2
0.1
0.0
-0.1
-0.2
Average
-0.3
-55 -35 -15
5
25 45 65
Temperature (°C)
85
105 125
Figure 20-2 shows the average accuracy for the
100 sample lot of MCP9700 temperature sensors
after compensation. The average error has been
decreased over the full temperature range.
It is also possible to compensate for error from
voltage references using this method.
For more information on compensating a
temperature sensor digitally, refer to AN1001, “IC
Temperature Sensor Accuracy Compensation with
a PICmicro® Microcontroller” (DS01001).
The software and referenced documents can be
found on the CD included with this booklet, or on
the Microchip Technology web site at
www.microchip.com.
© 2006 Microchip Technology Inc.
DS41283A-page 55
Tips ‘n Tricks
TIP #21 Using Output Voltage Monitoring
to Create a Self-Calibration
Function
A PIC® microcontroller can be used to create a
switching power supply controlled by a PID loop
(as described in Tip #16). This type of power
supply senses its output voltage digitally,
compares that voltage to the desired reference
voltage and makes duty cycle changes
accordingly. Without calibration, it is sensitive to
component tolerances.
FIGURE 21-1: TYPICAL POWER SUPPLY OUTPUT STAGE
VOUT
Switching Circuitry
C1
R1
Voltage Sense
R2
The output stage of many power supplies is similar
to Figure 21-1. R1 and R2 are used to set the ratio
of the voltage that is sensed and compared to the
reference.
DS41283A-page 56
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
A simple means of calibrating this type of power
supply is as follows:
1. Supply a known reference voltage to the
output of the supply.
2. Place the supply in Calibration mode and allow
it to sense that reference voltage.
By providing the supply with the output voltage that
it is to produce, it can then sense the voltage
across the resistor divider and store the sensed
value. Regardless of resistor tolerances, the
sensed value will always correspond to the proper
output value for that particular supply.
Futhermore, this setup could be combined with
TIP #20 to calibrate at several temperatures.
This setup could also be used to create a
programmable power supply by changing the
supplied reference and the resistor divider for
voltage feedback.
© 2006 Microchip Technology Inc.
DS41283A-page 57
Tips ‘n Tricks
NOTES:
DS41283A-page 58
© 2006 Microchip Technology Inc.
Tips ‘n Tricks
NOTES:
© 2006 Microchip Technology Inc.
DS41283A-page 59
Tips ‘n Tricks
NOTES:
DS41283A-page 60
© 2006 Microchip Technology Inc.
Information contained in this publication regarding device applications and the like is provided only for your convenience and may be
superseded by updates. It is your responsibility to ensure that your
application meets with your specifications. MICROCHIP MAKES
NO REPRESENTATIONS OR WARRANTIES OF ANY KIND
WHETHER EXPRESS OR IMPLIED, WRITTEN OR ORAL,
STATUTORY OR OTHERWISE, RELATED TO THE INFORMATION, INCLUDING BUT NOT LIMITED TO ITS CONDITION,
QUALITY, PERFORMANCE, MERCHANTABILITY OR FITNESS
FOR PURPOSE. Microchip disclaims all liability arising from this
information and its use. Use of Microchip’s products as critical
components in life support systems is not authorized except with
express written approval by Microchip. No licenses are conveyed,
implicitly or otherwise, under any Microchip intellectual property
rights.
Trademarks
The Microchip name and logo, the Microchip logo, Accuron,
dsPIC, KEELOQ, microID, MPLAB, PIC, PICmicro, PICSTART,
PRO MATE, PowerSmart, rfPIC, and SmartShunt are registered
trademarks of Microchip Technology Incorporated in the U.S.A.
and other countries.
AmpLab, FilterLab, Migratable Memory, MXDEV, MXLAB,
SEEVAL, SmartSensor and The Embedded Control Solutions
Company are registered trademarks of Microchip Technology
Incorporated in the U.S.A.
Analog-for-the-Digital Age, Application Maestro, dsPICDEM,
dsPICDEM.net, dsPICworks, ECAN, ECONOMONITOR,
FanSense, FlexROM, fuzzyLAB, In-Circuit Serial Programming,
ICSP, ICEPIC, Linear Active Thermistor, MPASM, MPLIB,
MPLINK, MPSIM, PICkit, PICDEM, PICDEM.net, PICLAB,
PICtail, PowerCal, PowerInfo, PowerMate, PowerTool, REAL
ICE, rfLAB, rfPICDEM, Select Mode, Smart Serial, SmartTel,
Total Endurance, UNI/O, WiperLock and ZENA are trademarks of
Microchip Technology Incorporated in the U.S.A. and other
countries.
SQTP is a service mark of Microchip Technology Incorporated in
the U.S.A. All other trademarks mentioned herein are property of
their respective companies.
© 2006, Microchip Technology Incorporated, Printed in the
U.S.A., All Rights Reserved.
Printed on recycled paper.
© 2006 Microchip Technology Inc.
DS41283A-page 61
M
Worldwide Sales and Service
AMERICAS
Corporate Office
Tel: 480-792-7200
Technical Support:
http://support.microchip.com
Atlanta
Tel: 770-640-0034
Boston
Tel: 774-760-0087
Chicago
Tel: 630-285-0071
Dallas
Tel: 972-818-7423
Detroit
Tel: 248-538-2250
Kokomo
Tel: 765-864-8360
Los Angeles
Tel: 949-462-9523
San Jose
Tel: 650-215-1444
Toronto
Tel: 905-673-0699
ASIA/PACIFIC
Australia
Tel: 61-2-9868-6733
China-Beijing
Tel: 86-10-8528-2100
China-Chengdu
Tel: 86-28-8676-6200
China-Fuzhou
Tel: 86-591-87503506
China-Hong Kong
SAR
Tel: 852-2401-1200
DS41283A-page 62
China-Qingdao
Tel: 86-532-85027355
China-Shanghai
Tel: 86-21-5407-5533
China-Shenyang
Tel: 86-24-2334-2829
China-Shenzhen
Tel: 86-755-82032660
China-Shunde
Tel: 86-757-28395507
China-Wuhan
Tel: 86-27-5980-5300
China-Xian
Tel: 86-29-8833-7250
India-Bangalore
Tel: 91-80-4182-8400
India-New Delhi
Tel: 91-11-5160-8631
India-Pune
Tel: 91-20-2566-1512
Japan
Tel: 81-45-471- 6166
Korea-Gumi
Tel: 82-54-473-4301
Korea-Seoul
Tel: 82-2-554-7200
Malaysia
Tel: 60-4-646-8870
Philippines
Tel: 63-2-634-9065
Singapore
Tel: 65-6334-8870
Taiwan-Hsin Chu
Tel: 886-3-572-9526
Taiwan-Kaohsiung
Tel: 886-7-536-4818
Taiwan-Taipei
Tel: 886-2-2500-6610
Thailand
Tel: 66-2-694-1351
EUROPE
Austria
Tel: 43-7242-2244-399
Denmark
Tel: 45-4450-2828
France
Tel: 33-1-69-53-63-20
Germany
Tel: 49-89-627-144-0
Italy
Tel: 39-0331-742611
Netherlands
Tel: 31-416-690399
Spain
Tel: 34-91-708-08-90
England
Tel: 44-118-921-5869
02/16/06
Microchip received ISO/TS-16949:2002 quality system
certification for its worldwide headquarters, design and
wafer fabrication facilities in Chandler and Tempe,
Arizona and Mountain View, California in October 2003.
The Company’s quality system processes and procedures
are for its PICmicro® 8-bit MCUs, KEELOQ® code hopping
devices, Serial EEPROMs, microperipherals, nonvolatile
memory and analog products. In addition, Microchip’s
quality system for the design and manufacture of
development systems is ISO 9001:2000 certified.
© 2006 Microchip Technology Inc.
Microchip Technology Inc.
2355 W. Chandler Blvd. • Chandler, AZ 85224 U.S.A.
Phone: 480-792-7200 • Fax: 480-792-9210
www.microchip.com
© 2006, Microchip Technology Inc., 4/06 DS41283A
*DS41283A*