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 2010-2011 Microchip Technology Inc. Note the following details of the code protection feature on Microchip devices: • Microchip products meet the specification contained in their particular Microchip Data Sheet. • Microchip believes that its family of products is one of the most secure families of its kind on the market today, when used in the intended manner and under normal conditions. • There are dishonest and possibly illegal methods used to breach the code protection feature. All of these methods, to our knowledge, require using the Microchip products in a manner outside the operating specifications contained in Microchip’s Data Sheets. Most likely, the person doing so is engaged in theft of intellectual property. • Microchip is willing to work with customer who is concerned about the integrity of their code. • Neither Microchip nor any other semiconductor manufacturer can guarantee the security of their code. Code protection does not mean that we are guaranteeing the product as “unbreakable.” Code protection is constantly evolving. We at Microchip are committed to continuously improving the code protection features of our products. Attempts to break Microchip’s code protection feature may be a violation of the Digital Millennium Copyright Act. If such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that Act. 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 devices in life support and/or safety applications is entirely at the buyer’s risk, and the buyer agrees to defend, indemnify and hold harmless Microchip from any and all damages, claims, suits, or expenses resulting from such use. No licenses are conveyed, implicitly or otherwise, under any Microchip intellectual property rights. Trademarks The Microchip name and logo, the Microchip logo, dsPIC, KEELOQ, KEELOQ logo, MPLAB, PIC, PICmicro, PICSTART, PIC32 logo, rfPIC and UNI/O are registered trademarks of Microchip Technology Incorporated in the U.S.A. and other countries. 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.

- Similar pages