Analog Devices ADSST-EM-3040, ADSST-SALEM-3T specifications Potential Section

Page 17

ADSST-SALEM-3T

POWER-UP INITIALIZATION AND DATA FROM THE ADSST-SALEM-3T

The ADSST-SALEM-3T-EV boot loads the code from the nonvolatile flash memory as shown in the block diagram of a functional meter in Figure 1. The configuration and calibra- tion data also gets loaded from the nonvolatile memory. For further details on boot loading, refer to the ADSST-SALEM-3T- DK (Developer’s Kit) User Manual. The user manual also describes various commands for instantaneous and computed parameters.

VOLTAGE AND CURRENT SENSING

Figure 9 shows the input section for the voltage and current sections. Based on the voltage and current values, the GUI software in the ADSST-SALEM-3T-DK computes the values of resistors R1, R2, and R3. The closest available values to those calculated by the GUI software should be selected and used.

The ADSST-73360LAR has a peak-to-peak input range of VREF – (VREF × 0.6525) to VREF + (VREF × 0.6525); for VREF = 2.5 V, this is 0.856 V to 4.14 V p-p. This limit defines the resistance network on the potential circuits and the burden resistance on the sec- ondary side of the CT. Since the ADSST-73360LAR is a unipolar ADC, the ac potential and current signals have to be offset by some dc level. The reference design has a dc offset of 2.5 V. This limits the peak-to-peak signal range of potential and current to 3.28 V p-p or 1.16 V rms.

Potential Section

The selection of the potential divider circuit should be such that it can:

• Handle high surge voltages

•

Have minimum VA burden

•

Give approximately 1 V peak headroom to accommodate

VOLTAGE INPUT

PHASE

VOLTAGER1

R2

NEUTRAL

CURRENT INPUT

PHASER3 CURRENT

TO ADC CHANNEL

TO ADC CHANNEL

NEUTRAL

03738-0-007

overvoltages.

Current Section

The selection of CT ratio and burden resistance should be such that it can:

•Handle the complete dynamic range for the current signal input.

•Give approximately 1 V peak headroom to accommodate loads with high crest factors.

The reference design has a CT with a turns ratio of 1:2500 and burden resistance of 82 Ω. This generates 0.656 V rms or

Figure 9. Input Section

0.928 V peak at 20 A current. This leaves enough margin for current pulses or low crest factor loads, such as SMPS. The maximum current can be up to 32.768 A.

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Contents Parameter Each Phase Total FeaturesGeneral Description High accuracyADSST-SALEM-3T Table of Contents Easy Calibration Effective Phase CompensationEase of Design Quadrant and Other ConventionsArchitecture Overview ADSST-SALEM-3TGeneral Description of the ADSST-218X DSP Serial Ports Function ADSST-218X COMMON-MODE PinsPin Name No. of Pins Reset Clock SignalsRecommended Operating Conditions Parameter Min Max UnitParameter Test Conditions Min Typ Max Unit ADSST-SALEM-3T ADSST-218X Electrical CharacteristicsESD Caution ADSST-SALEM-3T Absolute Maximum RATINGS-ADSST-218XRating Parameter Min MaxADSST-218x ADSST-SALEM-3T PIN CONFIGURATION-ADSST-218XADSST-73360LAR General Description of the ADSST-73360LAR ADCParameter Min Typ Max Unit Test Conditions ADSST-SALEM-3T SPECIFICATIONS-ADSST-73360LARComments Digital Current Conditions Max mAParameter Rating ADSST-SALEM-3T Absolute Maximum RATINGS-ADSST-73360LARPin No Mnemonic Function PIN Function DescriptionsGround Plane Layout Grounding and LayoutPotential Section Current Voltage Min Typ Max Unit Parameter Nominal ValueCurrent Voltage Min Typ Voltage CurrentMax Unit Current VoltageMinTyp Min Typ View a ADSST-SALEM-3T Outline DimensionsOrdering Guide Part Number1 Temperature Range Processors Included PackageRev Page 22 Rev Page 23 Rev Page 24
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