LTC1966 - Precision Micropower ΔΣ RMS-to-DC Converter

1 LTC1966 . Precision Micropower RMS-to-DC Converter Features Description n Simple to Use, Requires One Capacitor The LTC 1966 is a true RMS-to-DC Converter that utilizes n True RMS DC Conversion Using Technology an innovative patented computational technique. The n High Accuracy: internal delta sigma circuitry of the LTC1966 makes it sim- Gain Accuracy from 50Hz to 1kHz pler to use, more accurate, lower power and dramatically Total Error from 50Hz to 1kHz more flexible than conventional log antilog RMS-to-DC . n High Linearity: converters. Linearity Allows Simple System Calibration The LTC1966 accepts single-ended or differential input n Low Supply Current: signals (for EMI/RFI rejection) and supports crest factors up 155 A Typ, 170 A Max to 4. Common mode input range is rail-to-rail. Differential n Ultralow Shutdown Current: input range is 1 VPEAK, and offers unprecedented linearity. A Unlike previously available RMS-to-DC converters, the n Constant Bandwidth: superior linearity of the LTC1966 allows hassle free system Independent of Input voltage calibration at any input voltage .

2 800kHz 3dB, 6kHz 1%. The LTC1966 also has a rail-to-rail output with a separate n Flexible Supplies: output reference pin providing flexible level shifting. The to Single Supply LTC1966 operates on a single power supply from to Up to Dual Supply or dual supplies up to A low power shutdown n Flexible Inputs: mode reduces supply current to A. Differential or Single-Ended Rail-to-Rail Common Mode voltage Range The LTC1966 is insensitive to PC board soldering and Up to 1 VPEAK Differential voltage stresses, as well as operating temperature. The LTC1966 . n Flexible Output: is packaged in the space saving MSOP package which is Rail-to-Rail Output ideal for portable applications. Separate Output Reference Pin Allows Level Shifting n Wide Temperature Range: Applications 55 C to 125 C n True RMS Digital Multimeters and Panel Meters n Small Size: n True RMS AC + DC Measurements Space Saving 8-Pin MSOP Package L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and No Latency DS is a trademark of Linear Technology Corporation.

3 All other trademarks are the property of their respective owners. Protected by Patents including 6359576, 6362677, 6516291 and 6651036. Typical Application Quantum Leap in Linearity Performance LINEARITY ERROR (VOUT mV DC VIN mV ACRMS). LTC1966 , . Single Supply RMS-to-DC Converter 0. TO VDD IN1 OUTPUT. DIFFERENTIAL LTC1966 . CAVE + VOUT. INPUT 1 F CONVENTIONAL. IN2 OUT RTN LOG/ANTILOG. 1966 TA01. F EN VSS GND. OPT. AC. COUPLING 60Hz SINEWAVES. 0 50 100 150 200 250 300 350 400 450 500. VIN (mV ACRMS) 1966 TA01b 1966fb 1. LTC1966 . Absolute Maximum Ratings Pin Configuration (Note 1). Supply voltage VDD to to 7V. VDD to VSS .. to 12V. VSS to 7V to TOP VIEW. Input Currents (Note 2).. 10mA GND 1 8 ENABLE. Output Current (Note 3).. 10mA IN1 2 7 VDD. IN2 3 6 OUT RTN. ENABLE VSS to VSS + 12V VSS 4 5 VOUT. OUT RTN VSS to VDD MS8 PACKAGE. Operating Temperature Range (Note 4) 8-LEAD PLASTIC MSOP.

4 TJMAX = 150 C, JA = 220 C/W. LTC1966 40 C to 85 C. 40 C to 125 C. 55 C to 125 C. Specified Temperature Range (Note 5). LTC1966 40 C to 85 C. 40 C to 125 C. 55 C to 125 C. Maximum Junction 150 C. Storage Temperature 65 C to 150 C. Lead Temperature (Soldering, 10 sec).. 300 C. Order Information LEAD FREE FINISH TAPE AND REEL PART MARKING* PACKAGE DESCRIPTION TEMPERATURE RANGE. LTC1966 CMS8#PBF LTC1966 CMS8#TRPBF LTTG 8-Lead Plastic MSOP 0 C to 70 C. LTC1966 IMS8#PBF LTC1966 IMS8#TRPBF LTTH 8-Lead Plastic MSOP 40 C to 85 C. LTC1966 HMS8#PBF LTC1966 HMS8#TRPBF LTTG 8-Lead Plastic MSOP 40 C to 125 C. LTC1966 MPMS8#PBF LTC1966 MPMS8#TRPBF LTTG 8-Lead Plastic MSOP 55 C to 125 C. Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. For more information on lead free part marking, go to: For more information on tape and reel specifications, go to: Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 C.

5 VDD = 5V, VSS = 5V, VOUTRTN = 0V, CAVE = 10 F, VIN = 200mVRMS, VENABLE = unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS. Conversion Accuracy GERR Conversion Gain Error 50Hz to 1kHz Input (Notes 6, 7) %. LTC1966C, LTC1966I l %. LTC1966H, LTC1966MP l %. VOOS Output offset voltage (Notes 6, 7) mV. LTC1966C, LTC1966I l mV. LTC1966H, LTC1966MP l mV. LINERR Linearity Error 50mV to 350mV (Notes 7, 8) l %. 1966fb 2. LTC1966 . Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 C. VDD = 5V, VSS = 5V, VOUTRTN = 0V, CAVE = 10 F, VIN = 200mVRMS, VENABLE = unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS. PSRR Power Supply Rejection (Note 9) %V. LTC1966C, LTC1966I l %V. LTC1966H, LTC1966MP l %V. VIOS Input offset voltage (Notes 6, 7, 10) mV. l mV. Accuracy vs Crest Factor (CF).

6 CF = 4 60Hz Fundamental, 200mVRMS (Note 11) l 1 2 mV. CF = 5 60Hz Fundamental, 200mVRMS (Note 11) l 20 30 mV. Input Characteristics IVR Input voltage Range (Note 14) l VSS VDD V. ZIN Input Impedance Average, Differential (Note 12) 8 M . Average, Common Mode (Note 12) 100 M . CMRRI Input Common Mode Rejection (Note 13) l 7 200 V/V. VIMAX Maximum Input Swing Accuracy = 1% (Note 14) l 1 V. VIMIN Minimum RMS Input l 5 mV. PSRRI Power Supply Rejection VDD Supply (Note 9) l 250 600 V/V. VSS Supply (Note 9) l 120 300 V/V. Output Characteristics OVR Output voltage Range l VSS VDD V. ZOUT Output Impedance VENABLE = (Note 12) l 75 85 95 k . VENABLE = 30 k . CMRRO Output Common Mode Rejection (Note 13) l 16 200 V/V. VOMAX Maximum Differential Output Swing Accuracy = 2%, DC Input (Note 14) V. l V. PSRRO Power Supply Rejection VDD Supply (Note 9) l 250 1000 V/V. VSS Supply (Note 9) l 50 500 V/V. Frequency Response f1P 1% Additional Error (Note 15) CAVE = 10 F 6 kHz f10P 10% Additional Error (Note 15) CAVE = 10 F 20 kHz f 3dB 3dB Frequency (Note 15) 800 kHz Power Supplies VDD Positive Supply voltage l V.

7 VSS Negative Supply voltage (Note 16) l 0 V. IDD Positive Supply Current IN1 = 20mV, IN2 = 0V l 155 170 A. IN1 = 200mV, IN2 = 0V 158 A. ISS Negative Supply Current IN1 = 20mV, IN2 = 0V l 12 20 A. Shutdown Characteristics IDDS Supply Currents VENABLE = l 10 A. ISSS Supply Currents VENABLE = l 1 A. LTC1966H, LTC1966MP l 2 A. IIH ENABLE Pin Current High VENABLE = l A. 1966fb 3. LTC1966 . Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25 C. VDD = 5V, VSS = 5V, VOUTRTN = 0V, CAVE = 10 F, VIN = 200mVRMS, VENABLE = unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS. IIL ENABLE Pin Current Low VENABLE = l 2 1 A. LTC1966H, LTC1966MP l 10 A. VTH ENABLE Threshold voltage VDD = 5V, VSS = 5V V. VDD = 5V, VSS = GND V. VDD = , VSS = GND V. VHYS ENABLE Threshold Hysteresis V. Note 1: Stresses beyond those listed under Absolute Maximum Ratings Note 11: High speed automatic testing cannot be performed with 60Hz may cause permanent damage to the device.

8 Exposure to any Absolute inputs. The LTC1966 is 100% tested with DC stimulus. Correlation tests Maximum Rating condition for extended periods may affect device have shown that the performance limits above can be guaranteed with the reliability and lifetime. additional testing being performed to verify proper operation of all internal Note 2: The inputs (IN1, IN2) are protected by shunt diodes to VSS and circuitry. VDD. If the inputs are driven beyond the rails, the current should be limited Note 12: The LTC1966 is a switched capacitor device and the input/. to less than 10mA. output impedance is an average impedance over many clock cycles. The Note 3: The LTC1966 output (VOUT) is high impedance and can be input impedance will not necessarily lead to an attenuation of the input overdriven, either sinking or sourcing current, to the limits stated. signal measured. Refer to the Applications Information section titled Input Note 4: The LTC1966C/LTC1966I are guaranteed functional over Impedance for more information.

9 The operating temperature range of 40 C to 85 C. The LTC1966H/ Note 13: The common mode rejection ratios of the LTC1966 are measured LTC1966MP are guaranteed functional over the operating temperature with DC inputs from 50mV to 350mV. The input CMRR is defined as the range of 55 C to 125 C. change in VIOS measured between input levels of VSS to VSS + 350mV and Note 5: The LTC1966C is guaranteed to meet specified performance from input levels of VDD 350mV to VDD divided by VDD VSS 350mV. The 0 C to 70 C. The LTC1966C is designed, characterized and expected to output CMRR is defined as the change in VOOS measured with OUT RTN =. meet specified performance from 40 C to 85 C but is not tested nor VSS and OUT RTN = VDD 350mV divided by VDD VSS 350mV. QA sampled at these temperatures. The LTC1966I is guaranteed to meet Note 14: Each input of the LTC1966 can withstand any voltage within specified performance from 40 C to 85 C.

10 The LTC1966H is guaranteed the supply range. These inputs are protected with ESD diodes, so going to meet specified performance from 40 C to 125 C. The LTC1966MP is beyond the supply voltages can damage the part if the absolute maximum guaranteed to meet specified performance from 55 C to 125 C. current ratings are exceeded. Likewise for the output pins. The LTC1966 . Note 6: High speed automatic testing cannot be performed with input and output voltage swings are limited by internal clipping. The CAVE = 10 F. The LTC1966 is 100% tested with CAVE = 22nF. Correlation maximum differential input of the LTC1966 (referred to as maximum input tests have shown that the performance limits above can be guaranteed swing) is 1V. This applies to either input polarity, so it can be thought of as with the additional testing being performed to guarantee proper operation 1V. Because the differential input voltage gets processed by the LTC1966 .