ES5 True RMS-to-DC Converter Features Description True RMS-To-DC Conversion Computes RMS of AC and DC Signals 600mV full scale Wide Response： The ES5 is a true RMS-to-DC converter. It accepts low-level input signals from 0 to 600 mVRMS complex input waveforms. It can be operated form either a single supply or dual supplies. The device draws less than 1.2 mA of quiescent supply current, furthermore, a chip select pin is provided to power-down mode of the device, making it ideal for battery-powered applications. 1MHz 3dB Bandwidth for VRMS＞ 100mVRMS Single or Dual Supply Operation Power Down Function: Quiescent current reduction from 1.2mA to 5uA Buffered Voltage Output 14-lead SOIC (150mil width) Application * Digital Multi-Meters * Battery-Powered Instruments * Panel Meter Pin Assignment BUFF IN 1 NC 2 COMMON 3 ES6 ES5 TOP VIEW ( Not to Scale ) 14 BUFF OUT 13 VIN 12 NC 11 +VS OUTPUTOFFSET 4 CS 5 10 - VS DEN INPUT 6 9 RMS OUT NC 7 8 CAV NC = NO CONNECT SOP 14Pin Package Ver 1.1 1 14/10/21 ES5 True RMS-to-DC Converter Pin Description Pin No 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Symbol BUFF IN NC COMMON OUTPUT OFFSET CS DEN INPUT NC CAV RMS OUT -Vs +Vs NC VIN BUFF OUT Type I G O I I I/O O P P I O Description Buffer Input No Connection Analog Common Output Offset Chip Select Denominator Input No Connection Averaging Capacitor Connection RMS Output Negative Supply Rail Positive Supply Rail No Connection Signal input Buffer Output Absolute Maximum Ratings Supply Voltage：Dual Supplies ......…………………………………………….... ±6V Single Supply ..………………………………….……...……..... +12V Input Voltage：………………………………………………………….…………+Vs Power Dissipation (Package) SOIC：………………………………….……….. 450mW Operating Temperature Range：…………………… ……………….. -40℃ to +85℃ Storage Temperature Range：………………………………………… -55℃ to +150℃ Lead Temperature (Soldering, 10sec)：…………………………………………... 300℃ Ver 1.1 2 14/10/21 ES5 True RMS-to-DC Converter Electrical Characteristics (TA= +25℃, Vs = +3V, -Vs = -3V, unless otherwise noted.) PARAMETER Transfer Equation Averaging Time Constant CONDITIONS Figure 3 CONVERSION ACCURACY Total Error, Internal Trim (Notes 1,2) Total Error vs. Temperature (-40℃ to + 85℃) MIN TYP Total Error vs. Supply +VIN=300mV - VIN=-300mV 30 100 DC Reversal Error Vin= 600mV ±0.3 Total Error, External Trim (Note 1) Crest Factor 1 to 2 Crest Factor = 3 Crest Factor = 6 FREQUENCY RESPONSE (Note 2,4) mVRMS 2.2 5.0 ±3.0V Supplies ±5V Supplies 6 ±0.5 VPK KΩ mV TA=+25℃ ±0.5 mV TA =-40~85 ℃ ±0.1 mV/℃ +3V, -3V Supplies 2.2 V mA mA Ω KΩ 5 18 Chip Select High Chip Select Low 0.5 100 DENOMINATIOR INPUT Input Range Input Resistance Offset Voltage 0 to 2 25 ±0.2 BUFFER AMPLIFIER Input and Output Voltage Range Input Offset Voltage Input Current Input Resistance Output Current Short-Circuit Current Small-Signal Bandwidth Slew Rate (Note 5) Ver 1.1 ±% of Reading mV ±% of Reading 0 to 600 OUTPUT CHARACTERISTICS (Note 1) Output Resistance μV ±% of KHz KHz KHz KHz MHz MHz Input Resistance Input Offset Voltage Output Voltage Swing Output Current Short-Circuit Current mV ±% of Reading mV ±% of Reading/℃ 11 90 200 130 1 3 Continuous RMS, All Supplies Offset Voltage (Vin=COM) ms/μF CAV ±% of Reading INPUT CHARACTERISTICS Peak Transient UNITS Specified Accuracy ±0.1 ±0.5 VIN =10mV Bandwidth for 1% Additional VIN =100mV Error (0.09dB) VIN =600mV VIN =10mV ±3dB Bandwidth VIN =100mV VIN =600mV Input Signal range ±0.5 ±1.0 ±0.1 ±0.01 150 300 ±0.25 ±0.1 ERROR vs. CREST FACTOR Additional Error (Note 3) MAX VOUT = [avg.(VIN)2]1/2 25 V kΩ V -Vs to (+Vs-1.8V) ±0.8 ±50 108 20 1 5 3 V ±1.5 mV nA Ω 5 mA mA MHz V/μs 14/10/21 ES5 True RMS-to-DC Converter Electrical Characteristics (continued) (TA= +25℃, Vs = +3V, -Vs = -3V, unless otherwise noted.) PARAMETER Power SUPPLY CONDITIONS Dual Supplies Standby Current MIN TYP ±2.5 Connect CS to –Vs and Pin4 is connected to COMMON (Figure.1). Quiescent Current (Note 6) 1 MAX UNITS ±6 V 2 μA mA Note 1: Accuracy is specified for 0 to 600mV, 1kHz sine-wave input. Accuracy is degraded at higher RMS signal levels. Note 2: Measured at pin9 (RMS OUT), with pin 4 tied to COMMON. Note 3: Error vs. crest factor is specified as an additional error for 300mVRMS rectangular pulse input, pulse width = 200μs. Note 4: Input voltages are expressed in volts VRMS Note 5: With 10 kΩ external pull-down resistor from pin 14 (BUFF OUT) to – Vs. Note 6: With BUF input tied to COMMON. Ver 1.1 4 14/10/21 ES5 True RMS-to-DC Converter Standard Connection The ES5 is simple to connect for a majority of rms measurements. In the standard rms connection shown in Figure 1, only an external capacitor is required to set the averaging time constant. In this configuration, the ES5 computes the True RMS value of any input signal. The magnitude of an averaging error is dependent on the value of the averaging capacitor, is existed at lower frequencies. For example, if the filter capacitor, CAV, is 4.7μF, the error is 0.3% at 10Hz. To measure ac signal, the ES5 can be ac-couples by adding a capacitor in series with the input, as shown in Figure 1. The performance of the ES5 is tolerant of minor variations in the power supply voltages; however, if the supplies used exhibit a considerable amount of high frequency ripple, it is advisable to bypass both supplies to ground through a 0.1μF ceramic disc capacitor places as close to the device as possible. The output signal range of the ES5 is a function of the supply voltages, the output signal can be used buffered or nonbuffered, depending on the characteristics of the load. If no buffer is needed, tie the buffer input (Pin 1) to common. The output of the ES5 is capable of driving 5mA into a 2KΩ load without degrading the accuracy of the device. 1 BUFF IN 2 NC 3 COMMON 4 OUTPUT OFFSET 5 CS 6 DEN INPUT + Vs BUFF OUT ABSOLUTE VALUE 4.7K 7 ES6 ES5 + - 14 VIN 13 22uF VIN NC 12 ( OPTIONAL) BIAS SQUARER / DIVIDER + + +VS 11 + Vs - VS 10 - Vs RMSOUT 9 + CAV CAV NC 8 VOUT 4.7uF Figure 1. Standard connection for ES5 Ver 1.1 5 14/10/21 ES5 True RMS-to-DC Converter High-Accuracy Adjustments The accuracy of the ES5 can be further improved by the external trimming scheme as shown in Figure 2. The input should be grounded and R1 adjusted to give 0V output offset from pin 9. Alternatively, R1 could be adjusted to give the correct output with the lowest expected value of VIN. The R4 is in series with the pin13 to lower the range of the scale factor. Connect the desired full scale to VIN by using a DC or AC signal (ex. 500mVRMS), and R3 is trimmed to give the correct value for a calibrated signal. + Vs R2 R1 500K + Vs - Vs 1 BUFF IN 2 NC 3 COMMON 4 OUTPUT OFFSET 5 CS 6 DEN INPUT 100K 4.7K 7 ES6 ES5 + - BUFF OUT ABSOLUTE VALUE 14 VIN 13 R4 150 VIN NC 12 BIAS SQUARER / DIVIDER +VS 11 - VS 10 + + NC RMSOUT + Vs - Vs 9 + CAV CAV 8 VOUT 4.7uF R3 2K SCALE FACTOR TRM Figure 2. Optional External Gain and Offset Trims Chip Select The ES5 provides a chip select pin (Pin 5). To enable the device, this pin must be connected to +Vs. If it is connected to –Vs or floated, the device will enter power-down mode. The current it draws at this mode is less than 10uA. (Figure 1.) Ver 1.1 6 14/10/21 ES5 True RMS-to-DC Converter Choosing the Averaging Time Constant The ES5 computes the RMS value of AC and DC signals. At low frequencies and DC, the output tracks the input exactly; at higher frequencies, the average output approaches the RMS value of the input signal. The actual output differs from the ideal by an average (or DC) error plus some amount of ripple. The DC error term is a function of the value of CAV and the input signal frequency. The output ripple is inversely proportional to the value of CAV. Waveforms with high crest factors, such as a pulse train with low duty cycle, should have an average time constant chosen to be at least ten times the signal period. Using a large value of CAV to remove the output ripple increases the setting time for a step change in the input signal level. The primary disadvantage in using a large CAV to remove ripple is that the settling time for a step change in input level is increased proportionately. A better method to reduce the settling time and ripple is to use a post filter. A suggested circuit is shown in Figure 3. The 1-pole or 2-pole filter configuration allows a smaller CAV. With post filter, the value of CAV should be just large enough to give the maximum dc error at the lowest frequency of interest. And the output ripple will be removed by the post filter. 1 BUFF IN ES6 ES5 + - BUFF OUT ABSOLUTE VALUE 2 NC 3 COMMON OUTPUT 4 OFFSET + Vs DEN 6 INPUT VIN 13 BUFF OUT VIN + NC 12 C1 10uF BIAS SQUARER / DIVIDER +VS 11 5 CS 4.7K 14 - VS 10 + + RMSOUT - Vs 9 + CAV CAV 7 NC R1 24K + Vs 8 FOR A SINGLE-POLE FILTERSHORT R1 AND REMOVE C1 VOUT 4.7uF 24K + 10uF Figure 3. 2-Pole Filter Ver 1.1 7 14/10/21 ES5 True RMS-to-DC Converter Packaging 1.14 Pin SOP Package 2. Dimension Paramenters Ver 1.1 8 14/10/21