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SC7751
ELECTRONIC POWER METER IC WITH ELECTRICITY PROOF
DESCRIPTION
The SC7751 is a high accuracy fault-tolerant electrical energy measurement IC that can provides superior stability and accuracy over extremes in environmental conditions and over time. The SC7751 does not exhibit any creep when there is no load. The SC7751 supplies average real power information on the low frequency outputs F1 and F2. This logic outputs may be used to directly drive an electromecanical counter or interface to an MCU. The CF logic output gives instantaneous real power information. This output is intended to be used for calibration purposes, or interfacing to an MCU. The SC7751 incorporates the fault detection scheme that warns when the two input currents differ by more than 12.5%. Billing is continued using the larger of the two currents. The SC7751 includes a power supply monitoring circuit on the AVDD supply pin. If the supply falls below 4V, the SC7751 will be reset and F1, F2 will be set to logic high, CF will be set to logic low at the same time. The SC7751 provides synchronous frequency output for auto-reading meter system. The CF logic output is synchronous with the F1 and F2 logic output to ensure the show value of the meter is consonant with the real value. * Fault is indicated when the currents differ by more than 12.5%. * Less than 0.1% error over a dynamic range of 500 to 1. * On-chip creep protection (No load threshold). *The logic output REVP can be used to indicate a potential miswiring or negative power. * A PGA in the current channel make flexible to select the shunt and burden resistance.
SSOP-24
SDIP-24
FEATURES
* Single 5V supply, low power. * On-chip power supply monitoring. * On-chip reference with external overdrive capability. * Supplies average real power on the frequency outputs F1 and F2, which can drive for electromechanical counters directly. * The high frequency output CF is intended for calibration and supplies instantaneous real power.
ORDERING INFORMATION
Device SC7751S SC7751 Package SSOP-24-300-0.65 SDIP-24-300-2.54
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SC7751
BLOCK DIAGRAM
ABSOLUTE MAXIMUM RATING (Tamb=25C, unless otherwise specified)
Characteristics AVDD to AGND DVDD to DGND Analog Input Voltage to AGND V1P, V1N, V2P and V2N Reference Input voltage to AGND Digital Input Voltage to DGND Digital Output Voltage to DGND Power Dissipation Operating Temperature Range Industrial (A, B version) Storage Temperature Junction Temperature Symbol AVDD DVDD AVIN VREF DVIN DVOUT PD TOPR TSTG TJ Value -0.3 ~ +7 -0.3 ~ +7 -6 ~ +6 -0.3 ~ AVDD+0.3 -0.3 ~ DVDD+0.3 -0.3 ~ DVDD+0.3 450 -40~ +85 -65~ +150 +150 Unit V V V V V V mW C C C
ELECTRICAL CHARACTERISTICS (Tamb=25C, unless otherwise specified)
Characteristics Power Supply Analog Power Supply Digital Power Supply Analog Input Current Digital Input Current AVDD DVDD AIDD DIDD 5V5% 5V5% (2mA) TYP. (1.5mA) TYP. 4.75 4.75 ------5.25 5.25 3 2.5 mA V Symbol Test conditions Min. Typ. Max. Unit
(To be continued)
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SC7751
(Continued) Characteristics ACCURACY Gain=1 Measurement Error Gain=2 on Channel 1 Gain=8 Gain=16 Phase Error between Channels V1 Phase Lead 37 V1 Phase Lag 60 EP CFA CFD Fmin V1=100mV, V2=100mV, AC/ DC =1 S0=S1=1 G0=G1=0 V1=100mV, V2=100mV, EM Over a dynamic range 500 to 1 Over a dynamic range 500 to 1 Over a dynamic range 500 to 1 Over a dynamic range 500 to 1 AC/ DC =0 and AC/ DC =1 --------0.1 0.1 0.1 0.1 --0.01 0.01 ----0.1 0.1 --0.014% *Fbase % % % % % % Hz Symbol Test conditions Min. Typ. Max. Unit
Output Frequency Rejection (AC) Output Frequency Rejection (DC) The MIN. frequency of output (F1, F2) FAULT DETECTION Fault detection threshold, Inactive i/p < active i/p Input swap threshold Inactive i/p > active i/p Accuracy fault V1A active, V1B=AGND mode operation V1B active, V1A=AGND Fault detection delay Swap delay ANALOG INPUTS Maximum Signal Levels Input Impedance (DC) Bandwidth (-3dB) ADC Offset Error Gain Error Gain Error Match REFERENCE INPUT REFIN/OUT Input Voltage Range Input Impedance Input Capacitance ON-CHIP REFERENCE Reference Error Temperature Coefficient CLKIN Input Clock Frequency
VDD=DVDD=5V250mV --
(V1A or V1B active) (V1A or V1B active) Over a dynamic range 500 to 1 Over a dynamic range 500 to 1
12.5 14 0.1 0.1 3 3
% % % % s s
LEVS IMIN BW EADC EG EGM VINR IMIN CIN ER TC
V1P, VIN V2N and V2P to AGND CLKIN=3.58MHz CLKIN/256, CLKIN=3.58MHz V1=660mV, V2=660mV External 2.5V reference 2.5V8% ---
-400 ----2.3 3.7 ----
--14 -4 0.2 ----30
1 --15 --2.7 -10 200 60
V k kHz mV % % V k pF mV ppm/C
Nominal 2.5V
CLKIN
Note
all
specifications
for
CLKIN of 3.58MHz
1
--
4
MHz
(To be continued)
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SC7751
(Continued)
Characteristics LOGIC INPUTS Input High Voltage Input Low Voltage Input Current Input Capacitance LOGIC OUTPUTS F1 and F2 CF Output High Voltage Output Low Voltage
Symbol
Test conditions
Min.
Typ.
Max.
Unit
VINH VINL IIN CIN
DVDD=5V5% DVDD=5V5% Typically DVDD 10nA, VIN=0V to
2.4 ----
-----
-0.8 3 10
V V A pF
VOH VOL VOH VOL
ISOURCE=10mA DVDD=5V ISINK=10mA DVDD=5V ISOURCE=5mA DVDD=5V ISINK=5mA DVDD=5V
4.5 -4 --
-----
-0.5 -0.5
V V V V
and REVP Output High Voltage Output Low Voltage
and FAULT
PIN CONFIGURATIONS
DVDD AC/DC AVDD V1A V1B V1N V2N V2P RESET 1 2 3 4 5 6 7 8 9 24 F1 23 F2 22 CF 21 DGND 20 REVP 19 FAULT 18 CLKOUT 17 CLKIN 16 G0 15 G1 14 S0 13 S1
SC7751
REFIN/OUT 10 AGND 11 SCF 12
PIN DESCRIPTION
PIN No. 1 2 3 4 5 Symbol DVDD AC/ DC AVDD V1A V1B Digital Power Supply. High Pass Filter Select. The pin should be high in power metering applications. Analog Power Supply. Positive Inputs for Channel 1 (Current Channel). Channel 1 has a PGA and the gain selections are outlined in Table I. The maximum differential input voltage is 660mV with respect to Pin V1N. The maximum signal level at these pins is 1V with respect to AGND. 6 V1N Negative Inputs for Channel 1 (Current Channel). The maximum signal level at these pins is 1V with respect to AGND. (To be continued) Description
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SC7751
(Continued) PIN No. 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 Symbol V2N V2P
RESET
Description Negative and Positive Inputs for Channel 2 (Voltage Channel). The maximum differential input voltage is 660mV for specified operation. The maximum signal level at these pins is 1V with respect to AGND. Reset Pin for the SC7751. A logic low is valid; Reference voltage input/output pin. Analog ground. Select Calibration Frequency. This logic input is used to select the frequency on the calibration output CF. Table III shows how the calibration frequencies are selected. Select one of four possible frequencies for the digital-to-frequency conversion. See Table II and Table III Select gains for Channel 1, See Table I 3.58MHZ crystal oscillator input pin 3.58MHZ crystal oscillator output pin State indication pin. When the signals on V1A and V1B differ by more than 12.5%, it will be set to logic high. State indication pin. While negative power or a potential miswriting occurs, it will be set to logic high. Digital ground. Calibration Frequency Logic Output.. Low Frequency Logic Outputs. They can be used to directly drive a stepper motor or electromechanical impulse counter
REFIN/OUT AGND SCF S1 S0 G1 G0 CLKIN CLKOUT FAULT REVP DGND CF F2 F1
TIMIING CHARACTERISTICS1,2
(AVDD=DVDD=5V5%, AGND=DGND=0V, On-chip Reference, CLKIN=3.58MHZ, TMIN to TMAX=-40C~+85C.) Parameter t1
3
Test Condition F1 and F2 Pulse-width F1 and F2 Pulse Period. Time Between F1 Falling Edge and F2 Falling Edge CF Pulse-width CF Pulse Period. Minimum Time Between F1 and F2 Pulse
Test Data 275 See Table II 1/2 t2 90 See Table III CLKIN/4
Units ms sec sec ms sec sec
t2 t3 t4
3
t5 t6
NOTE: 1. Sample tested during initial release and after any redesign or process change that may after this parameter. 2. See the following figure. 3. The pulse-widths of F1, F2 and CF are not fixed for higher output frequencies.
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SC7751
t1 F1 t6 t2 F2 t3 t4 CF
Timing Diagram for Frequency outputs Timing Diagram for Frequency Outputs shows a timing diagram for the various frequency outputs of the SC7751. The low frequency outputs, F1 and F2 can drive electromechanical counters and two phase stepper motors directly. As the figure show, the F1 and F2 outputs provide two alternating low going pulses. The pulse width (t1) is set at 275ms and the time between the falling edges of F1 and F2 (t3) is approximately half the period of F1 (t2). If however the period of F1 and F2 falls below 550 ms (1.81Hz) the pulse width of F1 and F2 is set to half of their period. The frequency of F1 and F2 corresponds to the input voltages, and F= 8.06*V1*V2*G*Fbase/ VREF2The values of G and Fbase can be set by consumers, and the selection of G and Fbase please refer to the table I and table III , V1 and V2 are the rms value of the two inputs, VREF is the voltage of reference, whose value is 2.5+0.2v when the internal bandgap reference of SCE7755 is valid. The maximum output frequencies for F1 and F2 are shown in Table II. The high frequency output, CF is intended for calibration and supplies instantaneous real power. CF produces a 90ms wide active high pulse (t4) at a frequency proportional to active power. The CF output frequencies are given in Table III. As in the case of F1 and F2, if the period of CF (t5) falls below 180ms, the CF pulse-width is set to half the period. Table I. gain selection for channel 1 G1 0 0 1 1 G0 0 1 0 1 G 1 2 8 16 Maximum Differential Signal 660mV 330mV 82mV 41mV
t5
Table II. Maximum output frequency on F1 and F2 S1 0 0 1 1 S2 0 1 0 1 Max Frequency for DC Inputs (Hz) 0.68 1.36 2.72 5.44 Max Frequency for AC Inputs (Hz) 0.34 0.68 1.36 2.72
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SC7751
Table III. Maximum output frequency on CF SCF 1 0 1 0 1 0 1 0 altered. S1 0 0 0 0 1 1 1 1 S0 0 0 1 1 0 0 1 1 Fbase(Hz) 1.7 1.7 3.4 3.4 6.8 6.8 13.6 13.6 XTAL/CLKIN* 3.579MHz/2 3.579MHz/2
21 21
CF Max for AC signals (Hz) 128xF1, F2 64xF1, F2 64xF1, F2 32xF1, F2 32xF1, F2 16xF1, F2 16xF1, F2 8xF1, F2
3.579MHz/220 3.579MHz/220 3.579MHz/2 3.579MHz/2 3.579MHz/2 3.579MHz/2
19 19 18 18
NOTE: *Fbase is a binary fraction of the master clock and therefore will vary if the specified CLKIN frequency is
TYPICAL APPLICATION CIRCUIT
10F
100nF
100nF
100nF
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100nF
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SC7751
PACKAGE OUTLINE
SSOP-24-300-0.65 UNIT: mm
12(2x)
0.1520.05 0.3 0.65
8.150.2 12(4x)
SDIP-24-300-2.54
UNIT: mm
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SC7751
HANDLING MOS DEVICES:
Electrostatic charges can exist in many things. All of our MOS devices are internally protected against electrostatic discharge but they can be damaged if the following precautions are not taken: * Persons at a work bench should be earthed via a wrist strap. * Equipment cases should be earthed. * All tools used during assembly, including soldering tools and solder baths, must be earthed. * MOS devices should be packed for dispatch in antistatic/conductive containers.
NoteSilan reserves the right to make changes without notice in this specification for the improvement of the design and performance. Silan will supply the best possible product for customers.
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