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 SSOP-24 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 SDIP-24 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. FEATURES * 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. * 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 ORDERING INFORMATION Device Package SC7751S SSOP-24-300-0.65 SC7751 SDIP-24-300-2.54 directly. * The high frequency output CF is intended for calibration and supplies instantaneous real power. HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.2 2008.04.22 Page 1 of 10 SC7751 BLOCK DIAGRAM ABSOLUTE MAXIMUM RATING (Tamb=25°C, unless otherwise specified) Characteristics Symbol Value Unit AVDD to AGND AVDD -0.3 ~ +7 V DVDD to DGND DVDD -0.3 ~ +7 V AVIN -6 ~ +6 V Reference Input voltage to AGND VREF -0.3 ~ AVDD+0.3 V Digital Input Voltage to DGND DVIN -0.3 ~ DVDD+0.3 V DVOUT -0.3 ~ DVDD+0.3 V PD 450 mW TOPR -40~ +85 °C Storage Temperature TSTG -65~ +150 °C Junction Temperature TJ +150 °C Analog Input Voltage to AGND V1P, V1N, V2P and V2N Digital Output Voltage to DGND Power Dissipation Operating Temperature Range Industrial (A, B version) ELECTRICAL CHARACTERISTICS (Tamb=25°C, unless otherwise specified) Characteristics Symbol Test conditions Min. Typ. Max. Unit V Power Supply Analog Power Supply AVDD 5V±5% 4.75 -- 5.25 Digital Power Supply DVDD 5V±5% 4.75 -- 5.25 Analog Input Current AIDD (2mA) TYP. -- -- 3 Digital Input Current DIDD (1.5mA) TYP. -- -- 2.5 mA (To be continued) HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.2 2008.04.22 Page 2 of 10 SC7751 (Continued) Characteristics Symbol Test conditions Min. Typ. Max. Unit Gain=1 Over a dynamic range 500 to 1 -- 0.1 -- % Measurement Error Gain=2 Over a dynamic range 500 to 1 -- 0.1 -- % Over a dynamic range 500 to 1 -- 0.1 -- % Over a dynamic range 500 to 1 AC/ DC =0 and AC/ DC =1 -- 0.1 -- % -- -- ±0.1 ° -- -- ±0.1 ° -- 0.01 -- % -- 0.01 -- % ACCURACY on Channel 1 Gain=8 EM Gain=16 Phase Error V1 Phase Lead 37° between Channels V1 Phase Lag 60° EP Output Frequency Rejection (AC) CFA Output Frequency Rejection (DC) CFD The MIN. frequency of output (F1, F2) Fmin V1=100mV, V2=100mV, AC/ DC =1 S0=S1=1 G0=G1=0 V1=100mV, V2=100mV, VDD=DVDD=5V±250mV 0.014% -- *Fbase Hz FAULT DETECTION Fault detection threshold, (V1A or V1B active) 12.5 % (V1A or V1B active) 14 % fault V1A active, V1B=AGND Over a dynamic range 500 to 1 0.1 % mode operation V1B active, V1A=AGND Over a dynamic range 500 to 1 0.1 % Fault detection delay 3 s Swap delay 3 s Inactive i/p < active i/p Input swap threshold Inactive i/p > active i/p Accuracy ANALOG INPUTS V1P, VIN V2N and V2P to Maximum Signal Levels LEVS Input Impedance (DC) IMIN CLKIN=3.58MHz Bandwidth (-3dB) BW CLKIN/256, CLKIN=3.58MHz ADC Offset Error EADC AGND -- -- ±1 V 400 -- -- kΩ -- 14 -- kHz -- -- 15 mV EG V1=660mV, V2=660mV -- ±4 -- % EGM External 2.5V reference -- ±0.2 -- % REFIN/OUT Input Voltage Range VINR 2.5V±8% 2.3 -- 2.7 V Input Impedance IMIN -- 3.7 -- -- kΩ Input Capacitance CIN -- -- -- 10 pF -- -- 200 mV -- 30 60 ppm/°C 1 -- 4 MHz Gain Error Gain Error Match REFERENCE INPUT ON-CHIP REFERENCE Reference Error ER Temperature Coefficient TC Nominal 2.5V CLKIN Input Clock Frequency CLKIN Note all specifications CLKIN of 3.58MHz for (To be continued) HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.2 2008.04.22 Page 3 of 10 SC7751 (Continued) Characteristics Symbol Test conditions Min. Typ. Max. Unit LOGIC INPUTS Input High Voltage VINH DVDD=5V±5% 2.4 -- -- V Input Low Voltage VINL DVDD=5V±5% -- -- 0.8 V -- -- ±3 μA -- -- 10 pF 4.5 -- -- V Input Current IIN Input Capacitance CIN Typically 10nA, VIN=0V DVDD to LOGIC OUTPUTS Output High Voltage VOH ISOURCE=10mA DVDD=5V Output Low Voltage VOL ISINK=10mA DVDD=5V -- -- 0.5 V and REVP Output High Voltage VOH ISOURCE=5mA DVDD=5V 4 -- -- V VOL ISINK=5mA DVDD=5V -- -- 0.5 V F1 and F2 CF and FAULT Output Low Voltage PIN CONFIGURATIONS 1 24 F1 AC/DC 2 23 F2 AV DD 3 22 CF V1A 4 21 DGND V1B 5 20 REVP V1N 6 V2N 7 V2P 8 17 CLKIN RESET 9 16 G0 REF IN/OUT 10 15 G1 AGND 11 14 S0 SCF 12 13 S1 SC7751 DV DD 19 FAULT 18 CLKOUT PIN DESCRIPTION PIN No. Symbol Description 1 2 DVDD AC/ DC High Pass Filter Select. The pin should be high in power metering applications. 3 AVDD Analog Power Supply. 4 V1A Digital 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 5 V1B ±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) HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.2 2008.04.22 Page 4 of 10 SC7751 (Continued) PIN No. Symbol Description 7 V2N Negative and Positive Inputs for Channel 2 (Voltage Channel). The maximum 8 V2P 9 RESET 10 REFIN/OUT 11 AGND 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 12 SCF 13 S1 Select one of four possible frequencies for the digital-to-frequency conversion. 14 S0 See Table II and Table III 15 G1 16 G0 17 CLKIN 18 CLKOUT 19 FAULT 20 REVP 21 DGND 22 CF Calibration Frequency Logic Output.. 23 F2 Low Frequency Logic Outputs. They can be used to directly drive a stepper motor 24 F1 or electromechanical impulse counter the calibration output CF. Table III shows how the calibration frequencies are selected. 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. TIMIING CHARACTERISTICS1,2 (AVDD=DVDD=5V±5%, AGND=DGND=0V, On-chip Reference, CLKIN=3.58MHZ, TMIN to TMAX=-40°C~+85°C.) Parameter 3 Test Condition t1 F1 and F2 Pulse-width t2 F1 and F2 Pulse Period. t3 Time Between F1 Falling Edge and F2 Falling Edge 3 t4 CF Pulse-width t5 CF Pulse Period. t6 Minimum Time Between F1 and F2 Pulse Test Data Units 275 ms See Table II sec 1/2 t2 sec 90 ms See Table III sec CLKIN/4 sec 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. HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.2 2008.04.22 Page 5 of 10 SC7751 t1 F1 t6 t2 F2 t3 t4 t5 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）/ VREF2，The 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 G0 G Maximum Differential Signal 0 0 1 ±660mV 0 1 2 ±330mV 1 0 8 ±82mV 1 1 16 ±41mV Table II. Maximum output frequency on F1 and F2 S1 S2 Max Frequency for DC Inputs (Hz) Max Frequency for AC Inputs (Hz) 0 0 0.68 0.34 0 1 1.36 0.68 1 0 2.72 1.36 1 1 5.44 2.72 HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.2 2008.04.22 Page 6 of 10 SC7751 Table III. Maximum output frequency on CF SCF 1 S1 S0 0 0 Fbase(Hz) 1.7 XTAL/CLKIN* CF Max for AC signals (Hz) 21 3.579MHz/2 128×F1, F2 21 0 0 0 1.7 3.579MHz/2 64×F1, F2 1 0 1 3.4 3.579MHz/220 64×F1, F2 0 0 1 3.4 3.579MHz/220 32×F1, F2 6.8 19 32×F1, F2 19 16×F1, F2 18 16×F1, F2 18 8×F1, F2 1 0 1 0 1 0 1 0 1 1 1 1 6.8 13.6 13.6 3.579MHz/2 3.579MHz/2 3.579MHz/2 3.579MHz/2 NOTE: *Fbase is a binary fraction of the master clock and therefore will vary if the specified CLKIN frequency is altered. HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn 100nF 100nF 100nF 100nF 10μF TYPICAL APPLICATION CIRCUIT REV:1.2 2008.04.22 Page 7 of 10 SC7751 PACKAGE OUTLINE SSOP-24-300-0.65 UNIT: mm 12°(2×) 0.152±0.05 0.3 0.65 8.15±0.2 12°(4×) SDIP-24-300-2.54 HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn UNIT: mm REV:1.2 2008.04.22 Page 8 of 10 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. Note：Silan 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. HANGZHOU SILAN MICROELECTRONICS CO.,LTD Http: www.silan.com.cn REV:1.2 2008.04.22 Page 9 of 10