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Technical content
Features
True RMS-to-DC Conversion Fast settling time for all input levels Input level is specified up to 400mVRMS (Crest factor < 3 at +3V power) Averaging capacitor is typically 22uF Positive output voltage Computes RMS of AC and DC Signals Single or Dual Supply Operation Low Cost Low Power: 250μA typically Wide power supply range : from ± 2.5V(CF < 2) to ±6V Note: Input level up to 600mVRMS (CF < 2) if minimum power supply range +3V . 8-pin SOP package
Description
The ES736 series are designed for the true RMS-to-DC conversion. ES736 accept low-level input signals from 0 to 400 mV RMS complex input waveforms. ES736 can be operated form either a single supply or dual supplies. The device draws 0.25mA typically of quiescent supply current, furthermore, making it ideal for battery-powered applications. Application * Digital Multi-Meters * Battery-Powered Instruments * Panel Meter
V 1 . 4 1 8 / 0 5 / 3 1 2 ES736 True RMS-to-DC Converters Pin Assignment: ES736 SOP 8 Pin Package Pin Description Pin No Symbol Type Description
1 Cc I Low-Z measurement input
2 Vin I High-Z measurement input.
3 Cf I Connected to offset adjustment or kept open
4 -Vs P Negative supply voltage.
5 Cav I/O Averaging capacitor
6 V out O Measurement output. 7 +Vs P Positive supply voltage.
8 COM P Power ground
I: input, O: output, P: power 4 5 ES736 Cc Vin Cf -Vs Cav V out COM +Vs
V 1 . 4 1 8 / 0 5 / 3 1 3 ES736 True RMS-to-DC Converters Absolute Maximum Ratings Power Dissipation (Package) (TA= +25℃, Vs = +3V , -Vs = -3V , unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS Transfer Equation VOUT = avg.[(V IN) Averaging Time Constant 6 ms/μF CAV CONVERSION ACCURACY Total Error, Internal Trim (Notes 1) ES736 ±0.5 ± 1.5 mV ±% of Reading Total Error vs. Temperature Reading/℃ Total Error vs. Supply ±0.1 ±0.01 mV ±% of Reading/V Total Error vs. DC Reversal VIN=+ 400mV ±2.5 ±% of Reading Total Error, External trim 0.1/0.2 mV ±% of Reading Additional Error (Note 2) Cav=22μF Crest Factor = 1 400mV Specified Accuracy ±% of ReadingCrest Factor = 2 200mV 0.5 1.0 400mV 0.5 1.0 Crest Factor = 3 200mV 1.0 2.0 400mV 1.0 2.0 FREQUENCY RESPONSE Bandwidth for 1% Additional Error (0.09dB) 10mV 6 kHz 100mV 40 200mV 60 400mV 70
V 1 . 4 1 8 / 0 5 / 3 1 4 ES736 True RMS-to-DC Converters (TA= +25℃, Vs = +3V , -Vs = -3V , unless otherwise noted.) PARAMETER CONDITIONS MIN TYP MAX UNITS INPUT CHARACTERISTICS Input Signal range Continuous RMS, All Supplies 0 to 400 mV RMS Peak Transient ±2.5V Supplies 0.9 VPK ±3V Supplies 1.4 ±5V Supplies 2.8 Input Resistance Pin2 100 MΩ Input Offset Voltage (Note3) ES736 ±0.5 mV OUTPUT CHARACTERISTICS Output Voltage Swing +3V, -3V Supplies 1 VRMS ±5V Supplies 1 1.5 Power SUPPLY Rated Performance ±3 V Dual Supplies ±2.5 ±6 V Single Supply +5 +10 V Supply Current ±3V Supply. Vin connects to COM 250 - μA Note 1: Accuracy is specified for 0 to 400mV, 1kHz sine-wave input. Accuracy is degraded at higher RMS signal levels. Note 2: Error vs. crest factor is specified as an additional error for 200mV RMS and 400mVRMS rectangular pulse input, pulse width = 200μs Note 3: The input offset voltage can be reduced or canceled by an external 500kohm variable resistor shown in Figure
The standard RMS connection requires onl y two external components, Rin and C av. be the case in single-supply operation. Figure 1. Standard connection for ES736.
- SW1 is opened for AC-coupled (Cc is necessary for this case) operation, or closed
- The AC error component may be easily re moved by using a post filtering capacitor
500kohm VR can reduce the zero offset voltage. Figure 2. Adjust the zero-offset
- The 500k ohm variable resistor can be used to adjust the zero-offset voltage.
V 1 . 4 1 8 / 0 5 / 3 1 7 ES736 True RMS-to-DC Converters Fast setting time for all input levels There is almost no effect of signal input level on the settling time. 400ms 1KHz 100mV rms BURST INPUT CAV = 10uF 10mV 100mV 100mV DC OUT 1KHz 10mV rms BURST INPUT 10mV DC OUT 400ms
V 1 . 4 1 8 / 0 5 / 3 1 8 ES736 True RMS-to-DC Converters Application notes 1. AC-coupled operation Refer to the standard circuit of ES736 s hown in Figure 1~2. ES736 will work in an AC-coupled operation when the SW1 is opened. In AC-coupled operation, an AC-coupled capacitor (Ccp, see Fig1.) and bi as resistors Rin must be required. The pin1 connected to Cc capacitor is necessary for this case. 2. Post Filter CF To reduce the output ripple of ES736, a post filter capacitor C F is required. This capacitor should be connected as shown in fi gure 1 or 2. With post filter, the value of Cav (22uF) should be just large enough to gi ve the maximum dc error at the lowest frequency of interest. And the output ripple will be removed by the post filter (1uF).
V 1 . 4 1 8 / 0 5 / 3 1 9 ES736 True RMS-to-DC Converters Packaging