3-phase dc brushless motor pre-drivers technical information NJM2625A 1 ?05.07.07 1.feature njm2625 is a controller and pre-driver for speed control 3-phase blushless dc motor. the device provides the proper sequencing of 3-phase drive output with external hall elements inputs.(120degree turn-on mode) it is possible to control of 3-phase blushless dc motor by added external output buffers. the device has totem-pole pre-drivers for external power mos transistors and therefore can make the target output motor driver by using suitable power elements. further more the device has pwm control ,forward-reverse rotation and current limiting function. 2. application circuit the application shown in below circuit is designed for an open loop motor speed control system that the upper power switch are p-channel power mosfet while the lower switches are n-channel power mosfet. mosfet drive (upper:pch ,lower:nch),lower side pwm operating v + :12v, supply vm:24v 3:h1+ 20:f/r rotor position decode 2:vref vref + - uvlo saw osillator + - 10:osc 9:verr logic 11:gnd + - 12: ilimit 15:ul 14:vl 13:wl 18:wh 17:vh 16:wh 4:h1- 5:h2+ 6:h2- 7:h3+ 8:h3- + - + - + - fg 19:v+ v+ 1:fg pwm comp n n s s motor h1 h2 h3 v+ v+ vm
3-phase dc brushless motor pre-drivers technical information NJM2625A - 2 - 3. terminal functions (3-1) wl, ul, vl it consists of totem-pole pre-driver and control the upper p-channel power mosfet. the upper side gate bias current is generated with connected inverting transistor and resistor. regarding design case at 4.5v about the gate bias voltage of p-channel power mosfet. ma r bias vbe voh igate 20 470 6 . 0 10 = ? = ? = v igate rgate vgs 5 . 4 02 . 0 220 = = = the values of r-bias and r-gate should be 470 ? , 220 ? . here, it was referred to as voh: 10v and vbe:0. 6v. (3-2) wh, vh, uh it consists of totem-pole pre-driver and control the lower n-channel power mosfet. it is possible to make motor speed control by pwm control. series gate resistor rg will damp any high frequency oscillations caused by the mosfet input capacitance and any series wiring induction in the gate-source circuit. (3-3) h1+, h1-, h2+, h2-, h3+, h3- it is the signal input terminal of the hall device that controls on-off of 3-phase mosfet bridge. positive input is defined as h+>h-, negative is defined as h+ 3-phase dc brushless motor pre-drivers technical information NJM2625A - 3 - the relation between hall inputs and commutation logic outputs is as follows. commutation logic truth table hall inputs f/r=l f/r=h outputs h1 h2 h3 h1 h2 h3 uh vh wh ul vl wl fg h l h l h l l h l h l l h h l l l h h l l h h l l l h h l l l h l l h l h l h l h l h l h h l l l h l l l h h h l l h l l l l h h l l h h h l l h l l l h l the information of the timing chart is shown in attached (4-2) (4-6) i limit it is the motor over-current detection terminal. the motor current is converted to a voltage by inserting a ground-referenced sense resistor rs in series with the three lower mosfets. the voltage developed across the sense resistor is monitored by i limit terminal, and compared to the internal sense voltage(v th ). if the current sense is exceeded, the comparator sets the over-current latch and terminates the pwm output. over-current detection is reset for every cycle of the internal oscillator. the value for over-current detection is: rs vth = i when an over-current detection function is not well detected by the noise etc., the addition of the rc filter will eliminate current-limit instability by the leading edges spike on the current waveform. (4-7) vref it is the output terminal of internal reference voltage. this terminal please inserts capacitor between gnd for stabilization. (we recommend capacitor value is 1 f. ) (4-8) verr it is the motor speed control terminal. input voltage is compared with internal triangular wave voltage, and pwm operation is carried out. the use of pwm provides an energy efficient method of controlling the motor speed by varying the average voltage applied to each motor winding. please input the voltage of 0 v-vref. when the motor speed control stabilized more is required, closed loop control using fg signal etc. is performed. (4-9) osc by connecting a capacitor to this terminal, the internal oscillation frequency is decided. frequency is set to about 25khz when capacitor value is 1000pf. if frequency is low, the switching sound from a motor will occur, and if high, the switching loss of a power element will increase. we recommend selection with a frequency of 20 to 30khz.
3-phase dc brushless motor pre-drivers technical information NJM2625A - 4 - 4. appendix (4-1) the example of hall ic interface (4-2) the timing chart of hall input and pre-driver output f/r:l forward rotation f/r:h reverse rotation h1 h2 h3 ul vl wl uh vh wh h1 h2 h3 ul vl wl uh vh wh njm2625 vre f hall ic 3k 10k 20k 10k h1 r1=r2 h1=high:r3 and r4 are set up so that voltage of h1+ terminal is smaller than vcc-1.5v. h1=low:r3 and r4 are set up so that voltage of h1+ terminal is larger than 1.5v. 3k h1+ h1- r1 r2 r3 r4 r5
3-phase dc brushless motor pre-drivers technical information NJM2625A - 5 - (4-3) the ttl logic level conversion circuit of fg output (4-4)closed loop speed control circuit speed control circuit is shown as following figure. this circuit consists of input buffer, level shifter and speed control amplifier. motor speed can be changed by ?speed set? vr. vr1 is trimmer for final stage gain for stability. njm13403 is quad single supply general-purpose operational amplifier. the typical values of the other parts are shown in figure. the speed control circuit and the interface of njm2625 are as follows. v+ NJM2625A 10k fg hi:4.9v~3.82v low:0.5v(max) @v+=12v ttl level 5.6k from njm2625 fg out v+=12v to verr 2k 82k 47k 0.47u 2k 4.7u 10k 10k speed set opamp:njm13403 vr 1 10u 0.1u speed controller circui t v+ v+ njm2625 gnd gnd fg out verr fg in vou t 12v gnd connection with njm2625 *for other pins' connection,see product catalog. [caution] the specifications on this databook are only given for information , without any guarantee as regards either mistakes or omissions. the application circuits in this databook are described only to show representative usages of the product and not intended for the guarantee or permission of any right including the industrial rights.
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