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BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 1 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator features high accuracy, less than 0.1% error over a dynamic range of 500: 1 on-chip oscillator as clock source exactly measure the real power in the positive orientation and negative orientation, calculate the energy in the same orientation two current monitors continuously monitor the phase and neutral currents in two-wire distribution systems. uses the larger of two currents to bill, e ven during a fault condition a pga in the current channel allows using small value shunt and burden resistance the low frequency outputs f1 and f2 can directly drive electromechanical counters and two phase stepper motors and the high frequency output cf, supplies instantaneous real power, is intended f or calibration and communications two logic outputs revp and fault can be used to indicate a potential orientation or fault condit ion on-chip power supply detector on-chip anti-creep protection on-chip voltage reference of 2.5v 8% single 5v supply low static power (typical value of 25mw). the technology of slim (smartClowCcurrentC management) is used. credible work, working time is more than twenty years interrelated patents are pending description the BL0921 is a low cost, high accuracy, high stability, simple peripheral circuit electrical ene rgy meter ic. the meter based on the BL0921 is intended for using in single-phase, two-wire distribution systems. it can exactly measure the real power in t he positive orientation and negative orientation and calculate the energy in the same orientation. the BL0921 incorporates a novel fault detection scheme that both warns of fault conditions and allo ws the BL0921 to continue accurate billing during a fau lt event. the BL0921 does this by continuously monitoring both the phase and neutral (return) currents. pin12 (fault) indicates fault condition, when these currents differ by more than 12.5%. billing is continued using the larger of the two currents when the difference is greater than 14%. the BL0921 supplies average real power information on the low frequency outputs f1 (pin16) and f2 (pin15). these logic outputs may be used to directly drive an electromechanical counter and two-phase stepper motors. the cf (pin14) logic output gives instantaneous real power information. this output is intended to be used for calibration purposes or interface to an mcu. BL0921 thinks over the stability of reading error in the process of calibration. bulk test data indicate that in the condition of small signal 5%ib (ib=5a), the error of cf is less than 0.1%. an inter nal no-load threshold ensures that the BL0921 does not exhibit any creep when there is no load. block diagram 12 3 5 6 7 8 9 10 12 14 15 16 4 vdd v1a v1b v1n v2n v2p vref gnd s1 s0 revp cf f2 f1 BL0921 BL0921 BL0921 BL0921 11 g 13 fault current sampling voltage sampling analog to digital high pass filter digital multiplic ation digital to frequency and output low pass filter v1a v1av1a v1a v1n v1nv1n v1n v1b v1bv1b v1b v2p v2pv2p v2p v2n v2nv2n v2n revp revp revp revp cf cfcf cf f1 f1f1 f1 f2 f2f2 f2 BL0921 BL0921 BL0921 BL0921 vdd vddvdd vdd power detector voltage reference vref vref vref vref analog to digital input contron logic contron g gg g s0 s0s0 s0 s1 s1s1 s1 fault fault fault fault high pass filter internal oscillator sop 16
BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 2 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator pin descriptions pin symbol descriptions 1 vdd power supply (+5v). provides the supply voltage for the digital circuitry. it should be maintained at 5 v 5% for specified operation. 2,3 v1a,v1b inputs for current channel. these inputs are fully differential voltage inputs with a maximum signal level of 660 mv with respect to pin6 (v1n) for specified operation. 4 v1n negative input pin for differential voltage i nputs v1a and v1b. 5,6 v2n,v2p negative and positive inputs for voltage channel. t hese inputs provide a fully differential input pair. the maximum differential i nput voltage is 660 mv for specified operation. 7 vref on-chip voltage reference. the on-chip reference ha s a nominal value of 2.5v 8% . an external reference source may also be conne cted at this pin. 8 agnd ground reference. provides the ground refere nce for the circuitry. 9,10 s1,s0 output frequency select. these logic inputs are use d to select one of four possible frequencies for the digital-to-frequency conversion . this offers the designer greater flexibility when designing the energy meter. 11 g gain select. these logic inputs are used to select one of four possible gains for current channel. the possible gains are 1 and 16. 12 fault fault indication. logic high indicates fault condit ion. fault is defined as a condition under which the signals on v1a and v1b differ by mo re than 12.5%. the logic output will be reset to zero when fault condition is no lo nger detected. 13 revp negative indication. logic high indicates negative power, i.e., when the phase angle between the voltage and current signals is greater that 90 . this output is not latched and will be reset when positive power is once again detected. 14 cf calibration frequency. the cf logic output gives in stantaneous real power information. this output is intended to use for cal ibration purposes. 15,16 f1,f2 low-frequency. f1 and f2 supply average real power information. the logic outputs can be used to directly drive electromechanical cou nters and 2-phase stepper motors. absolute maximum ratings ( t = 25 ) parameter symbol value unit power voltage vdd vdd -0.3~+7(max) v input voltage of channel 2 to gnd v (v) vss+0.5 v(v) vdd-0.5 v input voltage of channel 1 to gnd v (i) vss+0.5 v(i) vdd-0.5 v operating temperature range topr -40~+75 storage temperature range tstr -55~+150 power dissipation 400 mw
BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 3 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator electronic characteristic parameter (t=25 , vdd=5v on-chip oscillator on-chip voltage reference) parameter symbol test condition measure pin min value typica l value max value unit 1 power supply i dd pin1 5 ma 2 logic input pins s1, s0, g, pin 9, 10, 11 input high voltage v ih 2 v input low voltage v il vdd=5v 1 v input capacitance c in 10 pf 3 logic output pins f1, f2, cf, revp, fault pin16,15 ,14,13,12 output high voltage v oh1 i h =10ma 4.4 v output low voltage v ol1 i l =10ma 0.5 v 4 on-chip reference vref vdd=5v pin7 2.3 2.5 2.7 v temperature coefficient 30 60 ppm/ c 5 analog input pins v1a, v1b, v1n, v2n, v2p pin 2,3,4,5,,6 maximum input voltage v ain 1 v dc input impedance 330 kohm input capacitance 6 10 pf 6 accuracy measurement error on channel 1 and 2 gain=1 enl1 pin14 0.1 % gain=16 enl16 both channels with full-scale signal 660mv over a dynamic range 500 to 1 pin14 0.1 % phase error between channels channel 1 lead 37 (pf=0.8 capacitive) pin14 0.1 channel 1 lags (pf=0.5 inductive) pin14 0.1 7 start current i start ib=5a, c=3200 pin14 0.2%ib a 8 positive and negative real power error (%) enp vv= 110mv,v(i)=2mv, cos j =1 vv= 110mv,v(i)=2mv, cos j =-1 pin14 0.1 0.3 % 9 gain error gain error pin14 5 %
BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 4 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator 10 gain error match pin14 0.2 1 % terminology 1) measurement error the error associated with the energy measurement ma de by the BL0921 is defined by the following formula: % 100 0921 re - = energy true energy true bl the gisteredby energy error pencebtage 2) nonlinear error the nonlinear error is defined by the following for mula: enl% [(error at x-error at ib) / (1+error at ib )]*100% when v(v)= 110mv, cos j =1, over the arrange of 5%ib to 800%ib, the nonline ar error should be less than 0.1%. 3) positive and negative real power error when the positive real power and the negative real power is equal, and v(v) = 110mv, the test current is ib, then the positive and negative real power error can be achieved by the following formula: enp%=|[(en%-ep%)/(1+ep%)]*100%| where: ep% is the positive real power error, en% is the negative real power error. 4) phase error between channels the hpf (high pass filter) in channel 1 has a phase lead response. to offset this phase response and equalize the phase response between channels, a phase correction network is also placed in channel 1. the phase correction network matches the phase to within 0.1 over a range of 45 hz to 65 hz and 0.2 over a range 40hz to 1khz. 5) gain error the gain error of the BL0921 is defined as the diff erence between the measured output frequency (minus the offset) and the ideal output frequency. it is measured with a gain of 1 in channel v1. the difference is expressed as a percentage of the ideal frequency. the ideal frequency is obtained from the BL0921 transfer function. 6) gain error match the gain error match is defined as the gain error ( minus the offset) obtained when switching between a gain of 1 and a gain of 16. it is express ed as a percentage of the output frequency obtained under a gain of 1. this gives the gain err or observed when the gain selection is changed from 1 to 16. 7) power supply monitor BL0921 has the on-chip power supply monitoring the BL0921 will remain in a reset condition until the supply voltage on vdd reaches 4 v. if the supply falls below 4 v, the BL0921 will also be reset and no pulses will be issued on f1, f2 and cf.
BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 5 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator timing characteristic (vdd=5v, gnd=0v, on-chip reference, integrated osci llator, temperature range: -20~+70 c) parameter value comments t1 144ms f1 and f2 pulse-width (logic low). when th e power is low, the t1 is equal to 144ms; when the power is high, a nd the output period falls below 550ms, t1 equals to half of the output period. t2 f1 or f2 output pulse period. t3 ? t2 time between f1 falling edge and f2 falling edge. t4 cf pulse period. see transfer function section. t5 71ms cf pulse-width (logic high). when the power is low, the t5 is equal to 71ms; when the power is high, and the o utput period falls below 180ms, t5 equals to half of the output period. t6 clkin/4 minimum time between f1 and f2. notes: 1) cf is not synchronous to f1 or f2 frequency outp uts. 2) sample tested during initial release and after a ny redesign or process change that may affect this parameter. theory of operation principle of energy measure in energy measure, the power information varying wi th time is calculated by a direct multiplication of the voltage signal and the curren t signal. assume that the current signal and the voltage signal are cosine functions; v and i are th e peak values of the voltage signal and the current signal; is the angle frequency of the input signals; the ph ase difference between the current signal and the voltage signal is expressed as . then the power is given as follows: ) cos( ) cos( ) ( f + = wt i wt v t p
BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 6 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator f =0: ) 2 cos( 1( 2 ) ( wt vi t p + = 1 f 0: [ ] ) sin( ) 2 sin( 2 ) cos( )) 2 cos( 1( 2 ) sin( ) sin( ) cos( ) cos( )) 2 cos( 1( 2 ) sin( ) sin( ) cos( ) cos( ) cos( ) cos( ) cos( ) ( f + f + = f + f + = f + f = f + = wt vi wt vi wt wt vi wt vi wt wt i wt v wt i wt v t p p(t) is called as the instantaneous power signal. t he ideal p(t) consists of the dc component and ac component whose frequency is 2 . the dc component is called as the average active power, that is: cos( ) 2 vi p j = the average active power is related to the cosine v alue of the phase difference between the voltage signal and the current signal. this cosine value is called as power factor (pf) of the two channel signals. figure1. the effect of phase when the signal phase difference between the voltag e and current channels is more than 90 , the average active power is negative. it indicates the user is using the electrical energy reversely. operation process in BL0921, the two adcs digitize the voltage signal s from the current and voltage transducers. these adcs are 16-bit second order sigma-delta with an over sampling rate of 900 khz. this analog input structure greatly simplifies transduce r interfacing by providing a wide dynamic range for direct connection to the transducer and also si mplifying the anti-alias filter design. a programmable gain stage in the current channel furt her facilitates easy transducer interfacing. a high pass filter in the current channel removes any dc component from the current signal. this eliminates any inaccuracies in the real power calcu lation due to offsets in the voltage or current signals. the real power calculation is derived from the inst antaneous power signal. the instantaneous power signal is generated by a direct multiplicatio n of the current and voltage signals. in order to extract the real power component (i.e., the dc comp onent), the instantaneous power signal is low-pass filtered. figure 2 illustrates the instant aneous real power signal and shows how the real power information can be extracted by low-pass filt ering the instantaneous power signal. this
BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 7 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator scheme correctly calculates real power for non-sinu soidal current and voltage waveforms at all power factors. all signal processing is carried out in the digital domain for superior stability over temperature and time. current sampling voltage sampling analog to digital analog to digital high pass filter digital multipli- cation digital to frequency low pass filter i v cf f1 f2 high pass filter v*i v*i p(t)=i(t)*v(t) v(t)=v*cos(wt) i(t)=i*cos(wt) p(t)= [1+cos(2wt)] 2 v*i 2 t v*i 2 t instantaneous power signal p(t) instantaneous real power signal integral figure 2. signal processing block diagram accumulating this real power information generates the low frequency output of the BL0921. this low frequency inherently means a long accumulation time between output pulses. the output frequency is therefore proportional to the average real power. this average real power information can, in turn, be accumulated (e.g., by a counter) t o generate real energy information. because of its high output frequency and hence shorter integration time, the cf output is proportional to the instantaneous real power. this is useful for system calibration purposes that would take place under steady load conditions. offset effect the dc offsets come from the input signals and the forepart analog circuitry. assume that the input dc offsets on the voltage cha nnel and the current channel are u offset and i offset , and pf equals 1 ( =0). ) 2 cos( 2 ) cos( ) cos( 2 ] ) cos( [ ] ) cos( [ ) ( t ui t i u t u i ui i t i u t u t p offset offset offset offset w w w w w + + + = + f + + = figure 3. effect of offset as can be seen, for each phase input, if there are simultaneous dc offsets on the voltage channel and the current channel, these offsets contribute a dc component for the result of multiplication. that is, the offsets bring the error of u offset i offset to the final average real power. additionally,
BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 8 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator there exists the component of u offset i + u i offset at the frequency of . the dc error on the real power will result in measure error, and the compone nt brought to the frequency of will also affect the output of the average active power when the next low-pass filter cannot restrain the ac component very completely. when the offset on the one of the voltage and the c urrent channels is filtered, for instance, the offset on the current channel is removed; the resul t of multiplication is improved greatly. there is no dc error, and the additional component at the fr equency of is also decreased. when the offsets on the voltage channel and the cur rent channel are filtered respectively by two high-pass filters, the component at the frequency o f (50hz) is subdued, and the stability of the output signal is advanced. moreover, in this case, the phases of the voltage channel and the current channel can be matched completely, and the performa nce when pf equal 0.5c or 0.5l is improved. in BL0921, this structure is selected. though it is given in the system specification that the ripple of the output signal is less than 0.1%, in real mea sure of BL0921, the calibration output is very stable, and the ripple of the typical output signal is less than 0.05%. additionally, this structure can ensure the frequen cy characteristic. when the input signal changes from 45hz to 65hz, the complete machine error due t o the frequency change is less than 0.1%. in such, the meter designed for the 50hz input signal can be used on the transmission-line system of electric power whose frequency is 60hz. voltage channel input the output of the line voltage transducer is connec ted to the BL0921 at this analog input. as figure4 shows that channel v2 is a fully differenti al voltage input. the maximum peak differential signal on channel 2 is 660mv. figure4 illustrates the maximum signal level s that can be connected to the BL0921 voltage channel. v1 v2 +660mv -660mv v1 v2 agnd v1a v1n + - v1b + - v1 gain gain maximun input differential voltage 660mv maximun input common-mode voltage 100mv figure 4. voltage channels voltage channel must be driven from a common-mode v oltage, i.e., the differential voltage signal on the input must be referenced to a common mode (u sually gnd). the analog inputs of the BL0921 can be driven with common-mode voltages of u p to 100 mv with respect to gnd. however, best results are achieved using a common m ode equal to gnd. figure5 shows two typical connections for channel v 2. the first option uses a pt (potential transformer) to provide complete isolation from the mains voltage. in the second option, the BL0921 is biased around the neutral wire and a resi stor divider is used to provide a voltage signal that is proportional to the line voltage. adjusting the ratio of ra and rb is also a convenient way of carrying out a gain calibration on the meter.
BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 9 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator agnd vap vn + - cf agnd cf rf rf ct 660mv agnd agnd vap vn + - cf agnd cf ra rf 660mv agnd agnd rb rv agnd ra >> rf rb+rv=rf phase neutral phase neutral figure 5. typical connections for voltage channels current channel input the voltage outputs from the current transducers ar e connected to the BL0921 here. as figure6 shows that channel v1 has two voltage inputs, namel y v1a and v1b. these inputs are fully differential with respect to v1n. however, at any o ne time, only one is selected to perform the power calculation. v1 v2 +660mv -660mv v1 v2 agnd v2p v2n + - maximun input differential voltage 660mv maximun input common-mode voltage 100mv figure 6. current channels the analog inputs v1a, v1b and v1n have same maximu m signal level restrictions as v2p and v2n. however, channel 1 has a programmable gain amp lifier (pga) with user-selectable gains of 1 or 16. these gains facilitate easy transducer int erfacing. figure illustrates the maximum signal levels on v1a, v1b, and v1n. the maximum differenti al voltage is 660 mv divided by the gain selection. again, the differential voltage sig nal on the inputs must be referenced to a common mode, e.g., gnd. the maximum common-mode signal is 100 mv. figure7 shows a typical connection diagram for chan nel v1. here the analog inputs are being used to monitor both the phase and neutral currents . because of the large potential difference between the phase and neutral, two cts (current tra nsformers) must be used to provide the isolation. the ct turns ratio and burden resistor ( rb) are selected to give a peak differential voltage of 660 mv/gain.
BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 10 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator v1a v1n + - cf rf ct 660mv agnd v1b + - cf rf ct rb rb gain 660mv gain phase neutral ip in v1a v1n + - agnd phase neutral v1b + - cf rf ct rb 660mv gain ip in agnd cf ra rb rv agnd 660mv ra >> rf rb+rv=rf figure 7. typical connections for current channels fault detection the BL0921 incorporates a novel fault detection sch eme that warns of fault conditions and allows the BL0921 to continue accurate billing during a fa ult event. the BL0921 does this by continuously monitoring both the phase and neutral (return) currents. a fault is indicated when these currents differ by more than 12.5%. however, even during a fault, the output pulse rate on f1 and f2 is generated using the larger of the two currents. because the BL0921 looks for a difference between the signals on v1a and v1b, it i s important that both current transducers are closely matched. on power-up the output pulse rate of the BL0921 is proportional to the product of the signals on channel v1a and voltage channel. if there is a difference of greater than 12.5% between v1a and v1b on power-up, the fault indicato r (fault) will go active after about one second. in addition, if v1b is greater than v1a the BL0921 will select v1b as the input. the fault detection is automatically disabled when the voltag e signal on channel 1 is less than 0.5% of the full-scale input range. this will eliminate false d etection of a fault due to noise at light loads. if v1a is the active current input (i.e., is being used for billing), and the signal on v1b (inactive input) falls by more than 12.5% of v1a, the fault i ndicator will go active. both analog inputs are filtered and averaged to prevent false triggering o f this logic output. as a consequence of the filtering, there is a time delay of approximately o ne second on the logic output fault after the fault event. the fault logic output is independent of any activity on outputs f1 or f2. figure 8 illustrates one condition under which fault becomes active. since v1a is the active input and it is still greater than v1b, billing is maintained on via, i.e., no swap to the v1b input will occur. v1a remains the active input.
BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 11 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator current sampling v1a v1n v1b 0v v1a v1b v1b < 87.5% v1a to adc fault figure 8. fault conditions for inactive input less than active input figure 9 illustrates another fault condition. if v1 a is the active input (i.e., is being used for bill ing) and the voltage signal on v1b (inactive input) beco mes greater than 114% of v1a, the fault indicator goes active, and there is also a swap ove r to the v1b input. the analog input v1b has now become the active input. again there is a time delay of about 1.2 seconds associated with this swap. v1a will not swap back to being the active ch annel until v1a becomes greater than 114% of v1b. however, the fault indicator will become in active as soon as v1a is within 12.5% of v1b. this threshold eliminates potential chatter be tween v1a and v1b. current sampling v1a v1n v1b 0v v1a v1b v1a < 87.5% v1b to adc fault figure 9. fault conditions for inactive input great er than active input power supply monitor the BL0921 contains an on-chip power supply monitor . if the supply is less than 4v 5% then the BL0921 will go in an inactive state, i.e., no e nergy will be accumulated when the supply voltage is below 4v. this is useful to ensure corre ct device operation at power up and during power down. the power supply monitor has built-in h ysteresis and filtering. this gives a high degree of immunity to false triggering due to noisy supplies. the trigger level is nominally set at 4v, and the t olerance on this trigger level is about 5%. the power supply and decoupling for the part should be such that the ripple at vdd does not exceed 5v 5% as specified for normal operation. slim technology the BL0921 adopts the technology of slim (smart low current management) to decrease the static power greatly. the static power of BL0921 is about 15mw. this technology also decreases the request for power supply design. bl65xx series products used 0.35um cmos process. th e reliability and consistency are advanced. operation mode transfer function the BL0921 calculates the product of two voltage si gnals (on channel 1 and channel 2) and then
BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 12 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator low-pass filters this product to extract real power information. this real power information is then converted to a frequency. the frequency information is output on f1 and f2 in the form of active low pulses. the pulse rate at these outputs is rela tively low. it means that the frequency at these outputs is generated from real power information ac cumulated over a relatively long period of time. the result is an output frequency that is pro portional to the average real power. the average of the real power signal is implicit to the digital -to-frequency conversion. the output frequency or pulse rate is related to the input voltage signals by the following equation. 2 )( ) ( 5.3 ref v fz gain i v v v freq = freq output frequency on f1 and f2 (hz) v(v) differential rms voltage signal on channel 1 (volts ) v(i) differential rms voltage signal on channel 2 (volts ) gain 1 , 16 depending on the pga gain selection, using l ogic inputs g vref the reference voltage (2.4 v 8%) (volts) fz one of four possible frequencies selected by using the logic inputs s0 and s1. s1 s0 fz(hz) 0 0 1.7 0 1 3.4 1 0 6.8 1 1 13.6 frequency output cf the pulse output cf (calibration frequency) is inte nded for use during calibration. the output pulse rate on cf can be up to 128 times the pulse r ate on f1 and f2. the following table shows how the two frequencies are related, depending on t he states of the logic inputs s0, s1 and scf. mode s1 s0 cf/f1 (or f2) 1 0 0 64 2 0 1 32 3 1 0 16 4 1 1 8 because of its relatively high pulse rate, the freq uency at this logic output is proportional to the instantaneous real power. as is the case with f1 an d f2, the frequency is derived from the output of the low-pass filter after multiplication. howeve r, because the output frequency is high, this real power information is accumulated over a much shorte r time. hence less averaging is carried out in the digital-to-frequency conversion. with much less averaging of the real power signal, the cf output is much more responsive to power fluctuation s. gain selection by select the digital input g0 and g1 voltage (5v o r 0v), we can adjust the gain of current
BL0921 BL0921 BL0921 BL0921 http://www.belling.com.cn - 13 - 3/15/2007 total 13 pages single phase energy meter ic single phase energy meter ic single phase energy meter ic single phase energy meter ic with integrated oscillator with integrated oscillator with integrated oscillator with integrated oscillator channel. we can see that while increasing the gain, the input dynamic range is decreasing. g gain maximum differential signal 1 1 660mv 0 16 41mv analog input range the maximum peak differential signal on voltage cha nnel is 660 mv, and the common-mode voltage is up to 100 mv with respect to gnd. the analog inputs v1a, v1b, and v1n have the same m aximum signal level restrictions as v2p and v2n. however, the current channel has a program mable gain amplifier (pga) with user-selectable gains of 1,16. these gains facilita te easy transducer interfacing. the maximum differential voltage is 660 mv and the maximum common-mode signal is 100 mv.the corresponding max frequency of cf/f1/f2 is shown in the following table. max frequency of f1, f2 (hz) cf max frequency (hz) s1 s0 fz dc ac dc ac 0 0 1.7 0.45 0.22 64 f1,f2=28.8 64 f1,f2=14.4 0 1 3.4 0.90 0.45 32 f1,f2=28.8 32 f1,f2=14.4 1 0 6.8 1.80 0.90 16 f1,f2=28.8 16 f1,f2=14.4 1 1 13.6 3.60 1.80 8 f1,f2=28.8 8 f1,f2=14.4 package dimensions sop16 notice sample tested during initial release and after any redesign or process change that may affect parameter. specification subjects t o change without notice. please ask for the newest product specification at any moment.

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