AN1332

AN1332
Current Sensing Circuit Concepts and Fundamentals
Author:
Yang Zhen
Microchip Technology Inc.
INTRODUCTION
Current sensing is a fundamental requirement in a wide
range of electronic applications.
Typical applications that benefit from current sensing
include:
•
•
•
•
•
•
•
•
•
•
•
Battery life indicators and chargers
Overcurrent protection and supervising circuits
Current and voltage regulators
DC/DC converters
Ground fault detectors
Linear and switch-mode power supplies
Proportional solenoid control, linear or PWM
Medical diagnostic equipment
Handheld communications devices
Automotive power electronics
Motor speed controls and overload protection
This application note focuses on the concepts and
fundamentals of current sensing circuits. It introduces
current sensing resistors, current sensing techniques
and describes three typical high-side current sensing
implementations, with their advantages and disadvantages. The other current sensing implementations are
beyond the scope of this application note and reserved
for subsequent Microchip Technology Incorporated’s
application notes.
 2010-2011 Microchip Technology Inc.
CURRENT SENSING RESISTOR
Description
A current sensor is a device that detects and converts
current to an easily measured output voltage, which is
proportional to the current through the measured path.
There are a wide variety of sensors, and each sensor
is suitable for a specific current range and
environmental condition. No one sensor is optimum for
all applications.
Among these sensors, a current sensing resistor is the
most commonly used. It can be considered a currentto-voltage converter, where inserting a resistor into the
current path, the current is converted to voltage in a
linear way of V = I × R.
The main advantages and disadvantages of current
sensing resistors include:
a)
b)
-
-
Advantages:
Low cost
High measurement accuracy
Measurable current range from very low to
medium
Capability to measure DC or AC current
Disadvantages:
Introduces additional resistance into the
measured circuit path, which may increase
source output resistance and result in
undesirable loading effect
Power loss since power dissipation
P = I2 × R. Therefore, current sensing
resistors are rarely used beyond the low and
medium current sensing applications.
DS01332B-page 1
AN1332
Selection Criteria
The disadvantages mentioned previously could be
reduced by using low-value sensing resistors.
However, the voltage drop across the sensing resistor
may become low enough to be comparable to the input
offset voltage of subsequent analog conditioning
circuit, which would compromise the measurement
accuracy.
Power Supply
Load
ISEN
In addition, the current sensing resistor’s inherent
inductance must be low, if the measured current has a
large high-frequency component. Otherwise, the
inductance can induce an Electromotive Force (EMF)
which will degrade the measurement accuracy as well.
Furthermore, the resistance tolerance, temperature
coefficient, thermal EMF, temperature rating and power
rating are also important parameters of the current
sensing resistors when measurement accuracy is
required.
RSEN
2.
3.
4.
Low resistance with tight tolerance, to create a
balance between accuracy and power
dissipation
High current capability and high peak power
rating to handle short duration and transient
peak current
Low inductance to reduce the EMF due to highfrequency components
Low temperature coefficient, low thermal EMF
and high temperature capability, if there is a
wide temperature variation
CURRENT SENSING TECHNIQUES
This section introduces two basic techniques for
current sensing applications, low-side current sensing
and high-side current sensing. Each technique has its
own advantages and disadvantages, discussed in
more detail in the following topics.
VOUT
ISEN
FIGURE 1:
a)
-
In brief, the selection of current sensing resistors is vital
for designing any kind of current monitor. The following
selection criteria can be used for guidance:
1.
Op Amps Circuits
b)
-
-
Low-Side Current Sensing.
Advantages:
Low input Common mode voltage
Low VDD parts
Ground referenced input and output
Simplicity and low cost
Disadvantages:
Ground path disturbance
Load is lifted from system ground since RSEN
adds undesirable resistance to the ground
path
High load current caused by accidental short
goes undetected
In a single-supply configuration, the most important
aspect of low-side current sensing is that the Common
mode input voltage range (VCM) of the op amp must
include ground. The MCP6H0X op amp is a good
choice since its VCM is from VSS – 0.3V to VDD – 2.3V.
Considering the advantages, choose low-side current
sensing where short circuit detection is not required,
and ground disturbances can be tolerated.
Low-Side Current Sensing
As shown in Figure 1, low-side current sensing
connects the sensing resistor between the load and
ground. Normally, the sensed voltage signal
(VSEN = ISEN × RSEN) is so small that it needs to be
amplified by subsequent op amp circuits (e.g., noninverting amplifier) to get the measurable output
voltage (VOUT).
DS01332B-page 2
 2010-2011 Microchip Technology Inc.
AN1332
High-Side Current Sensing
As shown in Figure 2, high-side current sensing
connects the sensing resistor between the power
supply and load. The sensed voltage signal is amplified
by subsequent op amp circuits to get the measurable
VOUT.
Power Supply
Op Amps Circuits
VOUT
Single Op Amp Difference Amplifier
Figure 3 shows a single op amp Difference amplifier
that consists of the MCP6H01 op amp and four external
resistors. It amplifies the small voltage drop across the
sensing resistor by the gain R2/R1, while rejecting the
Common mode input voltage.
ISEN
Load
FIGURE 2:
High-side current sensing is typically selected in
applications where ground disturbance cannot be
tolerated, and short circuit detection is required, such
as motor monitoring and control, overcurrent protection
and supervising circuits, automotive safety systems,
and battery current monitoring.
This section discusses three typical high-side current
sensing implementations, with their advantages and
disadvantages. Based on application requirements,
one choice may be better than another.
ISEN
RSEN
HIGH-SIDE CURRENT SENSING
IMPLEMENTATION
High-Side Current Sensing.
Advantages:
- Eliminates ground disturbance
- Load connects system ground directly
- Detects the high load current caused by
accidental shorts
b) Disadvantages:
- Must be able to handle very high and
dynamic Common mode input voltages
- Complexity and higher costs
- High VDD parts
Power Supply
a)
In a single-supply configuration, the most important
aspects of high-side current sensing are:
V1
R2
VREF
ISEN
VDD
VOUT
RSEN
MCP6H01
ISEN
V2
R1*
R2*
Load
R1 = R1*, R2 = R2*
• The VCM range of the Difference amplifier must be
wide enough to withstand high Common mode
input voltages
• The Difference amplifier’s ability to reject dynamic
Common mode input voltages
The MCP6H0X op amp is a good fit for high-side
current sensing, which will be discussed in more detail
in the following section.
R1
RSEN << R1, R2
R2
V OUT =  V 1 – V2    ------ + V REF
 R1
FIGURE 3:
Amplifier.
Single Op Amp Difference
The Difference amplifier’s Common mode rejection
ratio (CMRRDIFF) is primarily determined by resistor
mismatches (R1, R2, R1*, R2*), not by the MCP6H0X
op amp’s CMRR.
 2010-2011 Microchip Technology Inc.
DS01332B-page 3
AN1332
The resistor ratios of R2/R1 and R2*/R1* must be well
matched to obtain an acceptable CMRRDIFF. However,
the tight tolerance resistors will add more cost to this
circuit.
In brief, the VDM and VCM of the Difference amplifier
must meet the requirements shown in Equation 2:
EQUATION 2:
The DC CMRRDIFF is shown in Equation 1.
V OL – V REF
V OH – VREF
-----------------------------  VDM  -----------------------------G
G
EQUATION 1:
R
 1 + -----2-
R 1

CMRR DIFF  20 log  ----------------
 K 


V DM
R1
V CM   V CMRL – VREF    1 + ------ + ----------

R2
2
R1
VDM
VCM   V CMRH – V REF    1 + ------ – ----------
R 2
2
K = 4TR in the worst-case
Where:
Where:
G = R2/R1; Gain of Difference Amplifier
TR = Resistor Tolerance
VDM = V1 – V2; Difference Mode Input Voltage
of Difference Amplifier
K = Net Matching Tolerance
of R2/R1 to R2*/R1*
VCM = (V1 + V2)/2; Common Mode Input Voltage of Difference Amplifier
CMRRDIFF (dB) = Common Mode Rejection
Ratio of Difference Amplifier
Example 1
• If R2/R1 = 1 and TR = 0.1%, then the worst case
DC CMRRDIFF will be 54 dB.
• If R2/R1 = 1 and TR = 1%, then the worst case DC
CMRRDIFF will be only 34 dB.
Moreover, RSEN should be much less than R1 and R2
in order to minimize resistive loading effect. The
Difference amplifier’s input impedances, seen from V1
and V2, are unbalanced. Note that the resistive loading
effect and the unbalanced input impedances will
degrade the CMRRDIFF.
The reference voltage (VREF) allows the amplifier’s
output to be shifted to some higher voltage, with
respect to ground. VREF must be supplied by a lowimpedance source, to avoid making CMRRDIFF worse.
In addition, as shown in Figure 3, the input voltages (V1,
V2) can be represented by Common mode input voltage
(VCM) and Difference mode input voltage (VDM):
• V1 = VCM + VDM/2 and V2 = VCM + VDM/2
• VOUT = (V1 – V2) × G + VREF = VDM × G + VREF,
where G = R2/R1
In order to prevent VOUT from saturating supply rails, it
must be kept within the allowed VOUT range between
VOL to VOH.
The VCM range of the Difference amplifier has been
increased due to the resistor dividers made by R1, R2,
R1* and R2*.
DS01332B-page 4
VOH = Op Amp High-Level Output
VOL = Op Amp Low-Level Output
VCMRH = Op Amp Common Mode Input Voltage
High Limit
VCMRL = Op Amp Common Mode Input Voltage
Low Limit
Example 2
Refer to Figure 3 and assume that VDD = 16V,
VSS = GND, VREF = GND, R2/R1 = 1, and the voltage
drop across RSEN is 200 mV.
Thus, according to the MCP6H01 data sheet
(DS22243), it is VCMRH = VDD– 2.3V =13.7V, VCMRL
=VSS–0.3V = -0.3V.
Based on Equation 2, the acceptable VCM of the
Difference amplifier is from -0.5V to 27.3V.
The advantages and disadvantages of Difference
amplifiers include:
a)
Advantages:
- Reasonable Common mode rejection ratio
(CMRRDIFF)
- Wide Common mode input voltage range
- Low-power consumption, low cost and
simplicity
b) Disadvantages:
- Resistive loading effect
- Unbalanced input impedances
- Adjust the Difference amplifier’s gain by
changing more than one resistor value
 2010-2011 Microchip Technology Inc.
AN1332
Three Op Amp Instrumentation Amplifier
The three op amp instrumentation amplifier (3 op amp
INA) is illustrated in Figure 4. It amplifies small
Differential voltages and rejects large Common mode
voltages.
Power Supply
V1 = VCM + VDM/2
ISEN
VOUT1
1/4
R1
R2
VREF
MCP6H04
A1
RSEN
RF
1/4
RG
VOUT
MCP6H04
A3
ISEN
RF
R1*
1/4
V2 = VCM - VDM/2
MCP6H04
A2
R2*
VOUT2
Load
2R F
R2
2RF
VOUT =  V 1 – V 2    1 + ----------   ------ + V REF =  V 1 – V2    1 + ---------- + V REF


R G   R 1
RG 
Where setting R1 = R1*= R2 = R2*
FIGURE 4:
Three Op Amp Instrumentation Amplifier.
The 3 op amp INA’s architecture includes the following:
2.
1.
The second stage is implemented by a Difference
amplifier (A3) which amplifies the Difference mode
voltage and rejects the Common mode voltage. In a
practical application, the R2/R1 ratio is usually set to 1.
First Stage
The first stage is implemented by a pair of high-input
impedance buffers (A1, A2) and resistors (RF and RG).
These buffers avoid both the input resistive loading
effect and the unbalanced input impedances issue. In
addition, the resistors RF and RG increase the buffer
pairs’ Difference mode voltage gains (GDM) to 1 + 2RF/
RG while keeping their Common mode voltage gains
(GCM) equal to 1.
Second Stage
The CMRR3INA is primarily determined by the
Difference mode voltage gain of the first stage and net
matching tolerance of R2/R1 and R2*/R1*. Note that the
tolerance of resistors RF and RG do not affect
CMRR3INA.
One benefit of this method is that it significantly
improves the 3 op amp INA’s CMRR (CMRR3INA),
according to the equation CMRR = 20 log (GDM/GCM).
Thus, CMRR3INA will theoretically increase proportion
to GDM.
Another benefit is that the overall gain of the 3 op amp
INA can be modified by adjusting only the resistance of
RG without having to adjust the resistors of R1, R1*, R2
and R2*.
 2010-2011 Microchip Technology Inc.
DS01332B-page 5
AN1332
The DC CMRR3INA is shown in Equation 3.
EQUATION 4:
V OL – VREF
V OH – V REF
-----------------------------  V DM  -----------------------------G
G
VDM
V DM
VOL + -----------  G  VCM  VOH – -----------  G
2
2
EQUATION 3:
2R
  1 + ---------F-  2

RG  

CMRR 3INA  20 log  ---------------------------------
K




K = 4TR at the worst-case
Where:
Where:
G
=
1 + 2RF/RG; Overall Gain
VDM
=
V1 – V2; Difference Mode Input Voltage of
3 op amp INA
TR
=
Resistor Tolerance
VCM
=
K
=
Net Matching Tolerance
of R2/R1 to R2*/R1*
(V1 + V2)/2; Common Mode Input Voltage
of 3 op amp INA
VOH
=
Op Amp High-Level Output
VOL
=
Op Amp Low-Level Output
CMRR3INA (dB)
=
Common Mode Rejection
Ratio of 3 op amp INA
However, for the 3 op amp INA, there is a common
issue that can be easily overlooked. This issue exists in
the reduced Common mode input voltage range (VCM)
of the 3 op amp INA.
Referring to Figure 4, the input voltages (V1, V2) can be
represented by Common mode input voltage (VCM) and
Difference mode input voltage (VDM). That is
V1 = VCM + VDM/2 and V2 = VCM + VDM/2.
The amplifiers (A1, A2) provide a Difference mode
voltage gain (GDM), which is equal to the overall gain
(G), and a Common mode gain (GCM) equal to 1.
VOUT1 = VCM × GCM + (VDM/2)×GDM
= VCM + (VDM/2) × G
VOUT2 = VCM × GCM – (VDM/2) × GDM
= VCM – (VDM/2) × G
VOUT = VDM × G + VREF
In order to prevent VOUT1, VOUT2 and VOUT from
saturating supply rails, they must be kept within the
allowed output voltage range between VOL and VOH.
Or, stated in another way, the VDM and VCM of the 3 op
amp INA must meet the requirements shown in
Equation 4.
DS01332B-page 6
Example 3
Refer to Figure 4 and assume VREF = 0V, VDD = 15V,
VSS = 0V, VOH = 14.47V, VOL = 0.03V, RF = R1 = R1* =
R2 = R2* = 100 k, RG = 2 k, and the voltage drop
across RSEN is 100 mV.
Thus, the overall gain G is equal to 100 V/V, and the
voltage range left for the 3 op amp INA’s VCM is only
from 5.03V to 9.47V, based on Equation 4. This range
is smaller than MCP6H01 op amp’s VCM range, which
is from -0.3V to 12.7V at VDD = 15V.
In conclusion, the VCM range of the 3 op amp INA will
be significantly reduced when it operates in a high gain
configuration.
The advantages and disadvantages of the 3 op amp
INA include:
a)
Advantages:
- High Common mode rejection ratio
(CMRR3INA)
- No resistive loading effect
- Balanced input impedances
- Adjust the overall gain without needing to
change more than one resistor value
b) Disadvantages:
- VCM range of the 3 op amp INA is reduced
- Increased power consumption and costs, due
to more op amps
- MCP6H04 is not rail-to-rail op amp and its
VCM is from VSS-0.3V to VDD-2.3V, thus VDD
of the 3 op amp INA should be at least 2.3V
higher than the power supply of the measured system.
 2010-2011 Microchip Technology Inc.
AN1332
Two Op Amp Instrumentation Amplifier
The DC CMRR2INA is shown in Equation 5.
Figure 5 shows a 2 op amp instrumentation amplifier (2
op amp INA). Compared to the 3 op amp INA, the 2 op
amp INA provides savings in cost and power
consumption. The input impedances of the 2 op amp
INA are also very high, which avoids the resistive
loading effect and the unbalanced input impedances
issue.
EQUATION 5:
R
 1 + -----2-
R 1

CMRR 2INA  20 log  ----------------
K




K = 4TR at the worst-case
Where:
The Common mode rejection ratio of the 2 op amp INA
(CMRR2INA) is primarily determined by the overall gain
and the net matching tolerance of R2/R1 and R2*/R1*.
K = Net Matching Tolerance
of R2/R1 to R2*/R1*
TR = Resistor Tolerance
CMRR2INA (dB) = Common Mode Rejection
Ratio of 2 op amp INA
Power Supply
VREF
R2
V2
ISEN
R1
1/2
V1 = VCM - VDM/2
MCP6H02
R1*
VOUT1
A1
RSEN
R2*
V2 = VCM + VDM/2
1/2
MCP6H02
VOUT
A2
V1
ISEN
R2
V OUT =  V 2 – V1   1 + ------ + VREF

R 1
Load
Where setting R1 = R1* and R2 = R2*
FIGURE 5:
Two Op Amp Instrumentation Amplifier.
 2010-2011 Microchip Technology Inc.
DS01332B-page 7
AN1332
As shown in Figure 5, the input voltages (V1, V2) can be
represented by Common mode input voltage (VCM) and
Difference mode input voltage (VDM). That is,
V1 = VCM – VDM/2, and V2 = VCM + VDM/2.
VOUT = (1 + R2/R1)×(V2 – V1) + VREF
= (1 + R2/R1)×VDM + VREF
VOUT1 = (1 + R1/R2)×V1 – (R1/R2)×VREF
= (1 + R1/R2)×(VCM – VDM/2) – (R1/R2)×VREF
VOUT = VDM × G + VREF
Example 4
Refer to Figure 5 and assume R1 = R1* = 5 k,
R2 = R2* = 10 k, VREF = 0V, VDD = 15V, VSS = 0V,
VOH = 14.47V, VOL = 0.03V, and the voltage drop
across RSEN is 200 mV.
Thus, the overall gain G is equal to 3 V/V, and the
voltage range left for the 2 op amp INA’s VCM is from
0.12 V to 9.75 V. This range is smaller than the
MCP6H01 op amp’s VCM range, which is from -0.3V to
12.7V at VDD = 15V.
To prevent VOUT and VOUT1 from saturating into supply
rails, they must be kept within the allowed output
voltage range between VOL and VOH.
Unlike the 3 op amp INA, the VCM range of the 2 op
amp INA will be significantly reduced when it operates
in a low-gain configuration.
The VDM and VCM of the 2 op amp INA must meet the
requirements shown in Equation 6.
Moreover, the circuit’s asymmetry in the Common
mode signal path of the 2 op amp INA causes a phase
delay between VOUT1 and V1, degrading the AC CMRR
performance. Referring to Figure 5, the input signal V1
must pass through amplifier A1 before it can be
subtracted from V2 by amplifier A2. Thus, the VOUT1 is
slightly delayed and phase shifted with respect to V2.
This is a big disadvantage of 2 op amp INA.
EQUATION 6:
VOL – V REF
V OH – V REF
-----------------------------  VDM  -----------------------------G
G
R1
V OL + ------  VREF
R2
V DM
VCM  ----------------------------------------- + ----------2
G
R1
V OH + ------  V REF
R2
VDM
VCM  ------------------------------------------ + ----------2
G
Where:
G
=
1 + R2/R1; Overall Gain
VDM
=
V2 – V1; Difference Mode Input Voltage
of 2 op amp INA
VCM
=
(V1 + V2)/2; Common Mode Input
Voltage of 2 op amp INA
VOH
=
Op Amp High-Level Output
VOL
=
Op Amp Low-Level Output
Referring to Figure 6, by adding the resistor RG
between two inverting inputs, the overall gain of the 2
op amp INA can be easily set by adjusting only RG
instead of several resistors. Moreover, the R2/R1 ratio
is usually chosen for the desired minimum gain.
Another benefit of adding the resistor RG is that the
large resistor value usage of R2 and R2* can be
avoided in very high-gain configurations.
The VDM and VCM of 2 op amp INA with additional RG
must meet the requirements shown in Equation 7:
EQUATION 7:
V OL – VREF
VOH – VREF
-----------------------------  V DM  -----------------------------G
G
R1
R1
VOL + ------  V REF + -------  V DM
R2
RG
VDM
V CM  ------------------------------------------------------------------------ + ----------2
R1
1 + -----R2
R1
R1
VOH + ------  VREF + -------  V DM
R2
RG
VDM
V CM  ------------------------------------------------------------------------ + ----------2
R1
1 + -----R2
Where:
G = 1 + R2/R1 + 2R2/RG; Overall Gain
VDM = V2 – V1; Difference Mode Input Voltage of
2 op amp INA
VCM = (V1 + V2)/2; Common Mode Input Voltage
of 2 op amp INA
VOH = Op Amp High-Level Output
VOL = Op Amp Low-Level Output
DS01332B-page 8
 2010-2011 Microchip Technology Inc.
AN1332
RG (optional)
Power Supply
VREF
R1
R2
V2
ISEN
R1*
R2*
1/2
MCP6H02
VOUT1
A1
1/2
MCP6H02
RSEN
VOUT
A2
V1
ISEN
R2 2R 2
VOUT =  V2 – V 1   1 + ------ + --------- + VREF

R1 RG 
Load
Where setting R1 = R1* and R2 = R2*
FIGURE 6:
Two Op Amp Instrumentation Amplifier with Additional RG.
The advantages and disadvantages of the 2 op amp
INA include:
a)
b)
-
Advantages:
High DC Common mode rejection
(CMRR2INA)
No resistive loading effect
Balanced input impedances
Savings in cost and power consumption,
compared to the 3 op amp INA
Disadvantages:
Reduced VCM range
Poor AC CMRR2INA, due to the circuit’s
asymmetry
Unable to operate at unity gain
MCP6H02 is not rail-to-rail op amp and its
VCM is from VSS-0.3V to VDD-2.3V, thus VDD
of the 2 op amp INA should be at least 2.3V
higher than the power supply of the measured system
 2010-2011 Microchip Technology Inc.
SUMMARY
This application note provides an overview of current
sensing circuit concepts and fundamentals. It
introduces current sensing techniques and focuses on
three
typical
high-side
current
sensing
implementations, with their specific advantages and
disadvantages.
REFERENCES
Smither, M. A., Pugh, D.R. and Woolard, L.M.,
“C.M.R.R. Analysis of the 3-Op-Amp Instrumentation
Amplifier”, Electronics Letters, 2 Feb. 1989.
Sedra, A.S. and Smith, K.C., “Microelectronic Circuits”,
4th Edition, Oxford University Press, 1998.
DS01332B-page 9
AN1332
NOTES:
DS01332B-page 10
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FilterLab, Hampshire, HI-TECH C, Linear Active Thermistor,
MXDEV, MXLAB, SEEVAL 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, chipKIT,
chipKIT logo, CodeGuard, dsPICDEM, dsPICDEM.net,
dsPICworks, dsSPEAK, ECAN, ECONOMONITOR,
FanSense, HI-TIDE, In-Circuit Serial Programming, ICSP,
Mindi, MiWi, MPASM, MPLAB Certified logo, MPLIB,
MPLINK, mTouch, Omniscient Code Generation, PICC,
PICC-18, PICDEM, PICDEM.net, PICkit, PICtail, REAL ICE,
rfLAB, Select Mode, Total Endurance, TSHARC,
UniWinDriver, 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.
© 2010-2011, Microchip Technology Incorporated, Printed in
the U.S.A., All Rights Reserved.
Printed on recycled paper.
ISBN: 978-1-61341-590-0
Microchip received ISO/TS-16949:2009 certification for its worldwide
headquarters, design and wafer fabrication facilities in Chandler and
Tempe, Arizona; Gresham, Oregon and design centers in California
and India. The Company’s quality system processes and procedures
are for its PIC® MCUs and dsPIC® DSCs, 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.
 2010-2011 Microchip Technology Inc.
DS01332B-page 11
Worldwide Sales and Service
AMERICAS
ASIA/PACIFIC
ASIA/PACIFIC
EUROPE
Corporate Office
2355 West Chandler Blvd.
Chandler, AZ 85224-6199
Tel: 480-792-7200
Fax: 480-792-7277
Technical Support:
http://www.microchip.com/
support
Web Address:
www.microchip.com
Asia Pacific Office
Suites 3707-14, 37th Floor
Tower 6, The Gateway
Harbour City, Kowloon
Hong Kong
Tel: 852-2401-1200
Fax: 852-2401-3431
India - Bangalore
Tel: 91-80-3090-4444
Fax: 91-80-3090-4123
India - New Delhi
Tel: 91-11-4160-8631
Fax: 91-11-4160-8632
Austria - Wels
Tel: 43-7242-2244-39
Fax: 43-7242-2244-393
Denmark - Copenhagen
Tel: 45-4450-2828
Fax: 45-4485-2829
India - Pune
Tel: 91-20-2566-1512
Fax: 91-20-2566-1513
France - Paris
Tel: 33-1-69-53-63-20
Fax: 33-1-69-30-90-79
Japan - Yokohama
Tel: 81-45-471- 6166
Fax: 81-45-471-6122
Germany - Munich
Tel: 49-89-627-144-0
Fax: 49-89-627-144-44
Atlanta
Duluth, GA
Tel: 678-957-9614
Fax: 678-957-1455
Boston
Westborough, MA
Tel: 774-760-0087
Fax: 774-760-0088
Chicago
Itasca, IL
Tel: 630-285-0071
Fax: 630-285-0075
Cleveland
Independence, OH
Tel: 216-447-0464
Fax: 216-447-0643
Dallas
Addison, TX
Tel: 972-818-7423
Fax: 972-818-2924
Detroit
Farmington Hills, MI
Tel: 248-538-2250
Fax: 248-538-2260
Indianapolis
Noblesville, IN
Tel: 317-773-8323
Fax: 317-773-5453
Los Angeles
Mission Viejo, CA
Tel: 949-462-9523
Fax: 949-462-9608
Santa Clara
Santa Clara, CA
Tel: 408-961-6444
Fax: 408-961-6445
Toronto
Mississauga, Ontario,
Canada
Tel: 905-673-0699
Fax: 905-673-6509
Australia - Sydney
Tel: 61-2-9868-6733
Fax: 61-2-9868-6755
China - Beijing
Tel: 86-10-8569-7000
Fax: 86-10-8528-2104
China - Chengdu
Tel: 86-28-8665-5511
Fax: 86-28-8665-7889
Netherlands - Drunen
Tel: 31-416-690399
Fax: 31-416-690340
China - Chongqing
Tel: 86-23-8980-9588
Fax: 86-23-8980-9500
Korea - Seoul
Tel: 82-2-554-7200
Fax: 82-2-558-5932 or
82-2-558-5934
China - Hangzhou
Tel: 86-571-2819-3187
Fax: 86-571-2819-3189
Malaysia - Kuala Lumpur
Tel: 60-3-6201-9857
Fax: 60-3-6201-9859
China - Hong Kong SAR
Tel: 852-2401-1200
Fax: 852-2401-3431
Malaysia - Penang
Tel: 60-4-227-8870
Fax: 60-4-227-4068
China - Nanjing
Tel: 86-25-8473-2460
Fax: 86-25-8473-2470
Philippines - Manila
Tel: 63-2-634-9065
Fax: 63-2-634-9069
China - Qingdao
Tel: 86-532-8502-7355
Fax: 86-532-8502-7205
Singapore
Tel: 65-6334-8870
Fax: 65-6334-8850
China - Shanghai
Tel: 86-21-5407-5533
Fax: 86-21-5407-5066
Taiwan - Hsin Chu
Tel: 886-3-5778-366
Fax: 886-3-5770-955
China - Shenyang
Tel: 86-24-2334-2829
Fax: 86-24-2334-2393
Taiwan - Kaohsiung
Tel: 886-7-536-4818
Fax: 886-7-330-9305
China - Shenzhen
Tel: 86-755-8203-2660
Fax: 86-755-8203-1760
Taiwan - Taipei
Tel: 886-2-2500-6610
Fax: 886-2-2508-0102
China - Wuhan
Tel: 86-27-5980-5300
Fax: 86-27-5980-5118
Thailand - Bangkok
Tel: 66-2-694-1351
Fax: 66-2-694-1350
Spain - Madrid
Tel: 34-91-708-08-90
Fax: 34-91-708-08-91
UK - Wokingham
Tel: 44-118-921-5869
Fax: 44-118-921-5820
China - Xian
Tel: 86-29-8833-7252
Fax: 86-29-8833-7256
China - Xiamen
Tel: 86-592-2388138
Fax: 86-592-2388130
China - Zhuhai
Tel: 86-756-3210040
Fax: 86-756-3210049
DS01332B-page 12
Italy - Milan
Tel: 39-0331-742611
Fax: 39-0331-466781
Korea - Daegu
Tel: 82-53-744-4301
Fax: 82-53-744-4302
08/02/11
 2010-2011 Microchip Technology Inc.
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