NJM2646 - 1 - two-phase unipolar dc brushless motor pre-driver ic ? general description the NJM2646 is a 2-phase dc brushless motor pre-driver ic with a totem-pole pre-driver for external power mos-fet driving. it has useful functions of lock detect and auto protection circuit, which improve safety in motor locking. the turn-on/turn-off ratio in the auto-recovery period is set in 1:10. the njm2644 is available in surface mount packages, an 8-lead dmp, sop and thin type msop (tvsp), which provides downsizing in the 12v fan motor applications. and it is pin compatible with the njm2640, 48v pre-driver. ? package outline ? features ? operating voltage v dd =4 to 15v ? absolute maximum voltage 30v ? internal lock detect / auto protection release circuit ? internal hall amp with hysterisis ? lock alarm output terminal ? package outline dmp8, sop8 jedec 150mil msop8(tvsp8)* *meet jedec mo-187-da / thin type ? block diagrlam ? pin function 1: vcc 2: h1 3: la 4: h2 5: gnd 6: ct 7: out1 8: out2 5 6 7 8 4 3 2 1 h1 h2 vcc referrence bias ct to vcc gnd out2 out1 logic lock detect auto restart lock alarm la h c to vcc to vcc 1 2 3 4 5 6 8 NJM2646rb1 ( msop8(tvsp8 )) NJM2646m ( dmp8 ) NJM2646e ( sop8 )
NJM2646 - 2 - ? absolute maximum ratings (ta=25 c) parameter symbol ratings unit note supply voltage v cc 30 v - hall input voltage range v ih -0.3 to v cc v - output current (peak) i o ut 70 ma - lock alarm output voltage v ola 30 v - hall input differential voltage v ihd 2 v - lock alarm output current i ola 20 v - operating temperature range topr -40 to 85 c - operating junction temperature range toj -40 to 150 c - storage temperature range tstg -50 to 150 c - power dissipation p d 300 (dmp8) 300 (sop8) 400 (msop8(tvsp8)) mw device itself ? recommended operating conditions (ta=25 c) parameter symbol ratings unit (unit) note supply voltage v cc 4 to 15 v - hall input voltage common mode voltage v icm 1.5 to vcc-2 v - junction temperature tj -40 to 125 c -
NJM2646 - 3 - ? electrical characteristics (v dd =12v, ta=25c) parameter symbol condition min. typ. max. unit operating current icc - - 7.7 10.5 ma hall input hysterisis range v hys - 8 20 - mv hall amplifier input bias current i b - - 0.5 - a high side output voltage v oh i out =20ma 10.0 10.3 - v low side output voltage v ol i out =20ma - 0.5 0.8 v output clamp voltage v clm v cc =28v - 15 - v lock alarm output voltage v la lock alarm on,i la =5ma - - 0.5 v lock alarm leak current i la-leak v la =15v - 1 3 a ct charge current i c v ct =1.5v - 4.0 5.5 a ct discharge current i dc v ct =1.5v - 0.4 0.6 a charge / discharge current ratio i c / i dc - - 12 - ct h-level cense voltage v ch 2.2 2.5 2.8 v ct l-level cense voltage v cl - 0.85 0.95 1.05 v auto protection release on time t on ct=0.47f - 0.23 - s auto protection release on time t off ct=0.47f - 2.8 - s
NJM2646 - 4 - ? typical characteristics ? application note vcc vs icc 0 1 2 3 4 5 6 7 8 9 10 0 5 10 15 20 25 30 vcc[v] icc[ma] iout vs voh 5 6 7 8 9 10 11 12 0 1020304050607080 iout[m a] voh1[v] vcc vs vclm 0 2 4 6 8 1 0 1 2 14 16 0 5 10 15 20 25 30 vcc[v] vclm[v] iout vs vol 0. 0 0. 5 1 . 0 1 . 5 2 . 0 0 102030405060708090100 iout[m a] vol1[v] ta vs toff/ton 0 2 4 6 8 1 0 1 2 14 16 1 8 20 -50 -25 0 25 50 75 100 125 150 ta[ ? ] toff/ton[sec] vla 0 . 0 0.1 0. 2 0. 3 0. 4 0. 5 0 . 6 0 . 7 0.8 0. 9 1. 0 -50 -25 0 25 50 75 100 125 150 ta[ ? ] vla[v]
NJM2646 - 5 - the NJM2646 is a two-phase motor unipolar pre-driver ic for fet drive. it is suitable for fan motor drivers for communication equipment where 12v operation is required. [application circuit example] [design notes] above application example is designed for 12v oper ation. it uses the following components: hall elements: hw101a (ake) tr1,tr2: 2sk3022 (panasonic) 1. selection of c1 and d1: c1 is used for a noise reduction purpose. a typical value is 0.1uf. optimize the value in actual operating conditions if necessar y. d1 is a diode for protection against reverse voltage supply. silicon rectifier diode (wo3 c, 10d1 and equivalent) is appropriate. 2. lock protection function (design of c2 value): lock protection function, consists of motor lock detection and auto resume function, is a safety feature to protect a motor and a driver circuit from fatal destruction in case of motor halt. motor lock detection detects motor halt due to irregular load conditions and then cuts motor driving current f or safety operation. when lock detection is acti vated; lock alert out (la: pin 3) goes to l. a value of c2 determines lock detection time (ton) and auto resume time (toff). lock detection time (ton) is given by: where c2 is 0.47uf: auto resume time (toff) is given by: [] sec 2 ic vcl vch c t on ? = [] sec 18 . 0 10 0 . 4 95 . 0 5 . 2 10 47 . 0 6 6 = ? = ? ? on t h1 h2 vcc refarence bias ct gnd out2 out1 logic lock detect auto res tart lock alarm la motor vm hall element c2 r1 + - r2 d2 ca ra c1 d1 zd zd tr1 tr2 v+ gnd r3
NJM2646 - 6 - where c2 is 0.47uf: in actual application, lock detection time (ton) is affected by the mechanical time constant of a motor. therefore, constant start up must be confirmed in actual evaluation ta king operating variations (i.e. temperature, voltage change and so on) in consideration. a typical value of c2 is either 0.47uf or 1uf depending on a motor. lock protection lock alert out (la: pin 3) is a open collector output and r3 is a pull up resister. a typical value of r3 is 10k ? . it must be noted that lock alert out stays a h state du ring few hundred milliseconds from power up as shown in the picture below. [] sec 82 . 1 10 4 . 0 95 . 0 5 . 2 10 47 . 0 6 6 = ? = ? ? off t [] sec 2 idc vcl vch c t off ? = t on t off high hall input motor output ct teminal voltage lateminal voltage returns to normal operation motor lock protection period motor locked power supply la terminal output hundreds of millimeter second
NJM2646 - 7 - 3.design of hall element bias resistance ( r1 and r2 ) hall amplifier is a differential amplifier with hysteresis characteristics (24mv typical). the common-mode input voltage is between 1.5v and vcc- 2v and the input signal must be within the range. non-excitation hall bias voltage is to be set at a half of vcc for effective use of common-mode input voltage range. therefore the same value of hall bias resistors is selected for r1 and r2. given that the bias current is set to be 5ma by hw 101a datasheet, r1 and r2 can be determined as follows: the output voltage of hall elements is influenced by th e bias current and magnetic fl ux density of hall elements. the optimum input voltage of the NJM2646 is 100mvp-p and higher. with such input voltage, the highest efficiency can be obtained. 4. design of spike killer for power transistor ( zd1 and zd2 ) zenner diodes (often referred as spike killer ) are used fo r limiting kick back voltage of motor winding generated when power transistors is (tr1 and tr2) turned off from on. there are two methodologies to consume kick back voltage: 1) by insertion of zd1 (zenner diode connected between base and emitter of tr1) energy of kick back voltage is consumed by tr1(or tr 2). when zd1 is in operation, collector voltage is sum of vbe and zd1. therefore, breakdown voltage of zd1 must be lower than that of tr1. 2) by insertion of zd2 (zenner diode connected between collector and emitter of tr1) energy of kick back voltage is consumed by zd2. to protect tr1, breakdown voltage of zd2 must be lower than that of tr1. this method is generally used when energy of kick back volt age is large. in such application, power rating of zd must take in consideration. 5. vcc input (design of ra and ca ) ra and ca must be used if vcc ex ceeds operating voltage range of NJM2646. example) vcc 30v application given that current consumption of NJM2646 is 10.5ma (at vcc=12v), ra is given by: ca is used if NJM2646 is oscillated or shows unstable operation. a typical value ca is from 0.01 f to 0.1 f. a ceramic type is recommended and it must be place near vcc and gnd. inserting ra and ca also improves esd immunity. 7. protection from active power on and off ( d2 ) if an application requires active power on and off, tr1 (tr2) may be damaged or resulted in destruction. in such application, adding diode between moto r winding and gnd will reduce the damage. ? = = ? = = = + ? k r r k ihbias vcc r r 2 . 1 2 1 4 . 2 10 5 12 2 1 3 ? = ? = ? k ra 71 . 1 10 5 . 10 12 30 3
NJM2646 - 8 - the specifications on this data book are only given fo r information, without any guarantee as regards eithe r mistakes or omissions. the application circuit in this dat a book are described only to show representative usages o f the product and not intended for the guarantee o r permission of any right including the industrial rights.
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