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ds04-27208-1e fujitsu semiconductor data sheet assp bipolar switching regulator controller (4 channels plus high-precision, high-frequency capabilities ) MB3785a n description the MB3785a is a pwm-based 4-channel switching regulator controller featuring high-precision, high-frequency capabilities. all of the four channels of circuits allow their outputs to be set in three modes: step-down, step-up, and inverted. the third and fourth channels are suited for dc motor speed control. the triangular-wave oscillation circuit accepts a ceramic resonator, in addition to the standard method of oscillation using an rc network. n features ? wide range of operating power supply voltages: 4.5 v to 18 v ? low current consumption: 6 ma [typ] when operating10 m a or less during standby ? built-in high-precision reference voltage generator: 2.50 v1% ? oscillation circuit - capable of high-frequency oscillation: 100 khz to 1 mhz - also accepts a ceramic resonator. ? wide input range of error amplifier: C0.2 v to v cc C1.8 v ? built-in timer/latch-actuated short-circuiting detection circuit (continued) n package 48-pin, plastic lqfp (fpt-48p-m05)
2 MB3785a (continued) ? output circuit - the drive output for pnp transistors is the totem-pole type allowing the on-current and off-current values to be set independently. ? adjustable dead time over the entire duty ratio range ? built-in standby and output control functions ? high-density mounting possible: 48-pin lqfp package n pin assignment (top view) ve1 v cc 2 ve2 ve3 out4 cb4 cb1 out1 out2 gnd ve4 out3 osc in r t v cc 1 ctl1 ctl3 ?n3 (c) ?n2 (c) osc out c t v ref scp ctl2 (fpt-48p-m05) cb2 dtc1 ?n1 (e) ?n1 (c) fb2 +in2 (e) ca1 ca2 fb1 +in1 (e) ?n2 (e) dtc2 cb3 fb4 +in4 (e) dtc3 ?n3 (e) ca4 dtc4 ?n4 (e) ?n4 (c) +in3 (e) fb3 ca3 2 5 7 9 11 1 4 6 8 12 10 3 35 33 31 29 27 25 36 34 32 30 26 28 48 47 46 45 44 43 42 41 40 39 38 37 13 14 15 16 17 18 19 20 21 22 23 24 each alphabet in parentheses following the pin symbol indicates the input pin of the next circuit. (c) denotes a comparator. (e) denotes an error amplifier.
3 MB3785a n pin description (continued) pin no. symbol i/o description ch1 1 ca1 ch1 output transistor off-current setting pin. insert a capacitor between the ca1 and the cb1 pins, then set the output transistor off-current. 48 cb1 7 +in1(e) i ch1 error amp non-inverted input pin. 6 Cin1(e) i ch1 error amp inverted input pin. 5 fb1 o ch1 error amp output pin. 8 Cin1(c) i ch1 comparator inverted input pin. 4 dtc1 i ch1 dead time control pin. 47 ve1 i ch1 output current setting pin. 46 out1 o ch1 totem-pole output pin. ch2 3ca2 ch2 output transistor off-current setting pin. insert a capacitor between the ca2 and the cb2 pins, then set the output transistor off-current. 2cb2 12 +in2(e) i ch2 error amp non-inverted input pin. 11 Cin2(e) i ch2 error amp inverted input pin. 10 fb2 o ch2 error amp output pin. 13 Cin2(c) i ch2 comparator inverted input pin. 9 dtc2 i ch2 dead time control pin. 43 ve2 i ch2 output current setting pin. 44 out2 o ch2 totem-pole output pin. ch3 34 ca3 ch3 output transistor off-current setting pin. insert a capacitor between the ca3 and the cb3 pins, then set the output transistor off-current. 35 cb3 25 +in3(e) i ch3 error amp non-inverted input pin. 26 Cin3(e) i ch3 error amp inverted input pin. 27 fb3 o ch3 error amp output pin. 24 Cin3(c) i ch3 comparator inverted input pin. 28 dtc3 i ch3 dead time control pin. 41 ve3 i ch3 output current setting pin. 40 out3 o ch3 totem-pole output pin. ch4 36 ca4 ch4 output transistor off-current setting pin. insert a capacitor between the ca4 and the cb4 pins, then set the output transistor off-current. 37 cb4 30 +in4(e) i ch4 error amp non-inverted input pin. 31 Cin4(e) i ch4 error inverted input pin. 32 fb4 o ch4 error amp output pin. 29 Cin4(c) i ch4 comparator inverted input pin.
4 MB3785a (continued) pin no. symbol i/o description ch4 33 dtc4 i ch4 dead time control pin. 38 ve4 i ch4 output current setting pin. 39 out4 o ch4 totem-pole output pin. 14 osc in this pin connects a ceramic resonator. 15 osc out 16 r t this pin connects to a resistor for setting the triangular-wave frequency. 17 c t this pin connects to a capacitor for setting the triangular-wave frequency. 18 v cc 1 power supply pin for the reference power supply control circuit. 45 v cc 2 power supply pin for the output circuit. 42 gnd gnd pin. 19 v ref o reference voltage output pin. 23 scp this pin connects to a capacitor for the short-circuit protection circuit. 20 ctl1 i power supply circuit and first-channel control pin. 21 ctl2 i second-channel control pin. while the ctl1 pin is high 22 ctl3 i third and fourth-channel control pin. while the ctl1 pin is high triangular-wave oscillator circuit power supply circuitt control circuit when this pin is high, the power supply circuit and first channel are in active state. when this pin is low, the power supply circuit and first channel are in standby state. when this pin is high, the second channel is in active state. when this pin is low, the second channel is in the inactive state. when this pin is high, the third and fourth channels are in active state. when this pin is low, the third and fourth channels are in the inactive state.
5 MB3785a n block diagram 7 6 5 8 4 1 48 45 46 47 + + + 12 11 10 13 9 3 2 44 43 + + + 25 26 27 24 28 34 33 40 41 + + 30 31 32 29 33 36 37 39 38 + + 21 22 18 20 42 19 17 16 15 14 23 + + + + + + + + +in1 (e) ?n1 (e) fb1 ?n1 (c) dtc1 +in2 (e) ?n2 (e) fb2 ?n2 (c) dtc2 +in3 (e) ?n3 (e) fb3 ?n3 (c) dtc3 +in4 (e) ?n4 (e) fb4 ?n4 (c) dtc4 scp ctl1 v cc 1 ctl3 ctl2 out4 out3 out2 out1 ve4 cb4 ca4 ve3 cb3 ca3 ve2 cb2 ca2 ve1 cb1 ca1 v cc 2 pwm comparator 1 off current setting ch 1 error amp 1 comparator 1 v ref v ref 2 v dtc comparator 1 2.5 v ch 2 error amp 2 comparator 2 v ref dtc comparator 2 2 v v ref 2.5 v ch 3 error amp 3 comparator 3 0.6 v 100 w pwm comparator 2 pwm comparator 3 2.5 v ch 4 error amp 4 0.6 v 100 w 2.5 v pwm comparator 4 comparator 4 scp comparator 2.1 v 1.2 v ?.9 v ?.3 v 1 m a r sr latch s under voltage lock-out protection circuit triangular-wave oscillator circuit ref. vol. circuit power supply circuit & channel control 2.5 v osc in osc out rt ct v ref gnd dtc comparator 3 v ref ceramic resonator off current setting off current setting off current setting
6 MB3785a n functional description 1. switching regulator function (1) reference voltage circuit the reference voltage circuit generates a temperature-compensated reference voltage ( @ 2.50 v) using the voltage supplied from the power supply terminal (pin 18). this voltage is used as the operating power supply for the internal circuits of the ic. the reference voltage can also be supplied to an external device from the v ref terminal (pin 19). (2) triangular-wave oscillator circuit by connecting a timing capacitor and a resistor to the c t (pin 17) and the r t (pin 16) terminals, it is possible to generate any desired triangular oscillation waveform. the oscillation can also be obtained by using a ceramic resonator connected to pins 14 and 15. this waveform has an amplitude of 1.3 v to 1.9 v and is input to the internal pwm comparator of the ic. at the same time, it can also be supplied to an external device from the c t terminal (pin 17). (3) error amplifier this amplifier detects the output voltage of the switching regulator and outputs a pwm control signal accordingly. it has a wide common-mode input voltage range from C0.2 v to v cc C1.8 v and allows easy setting from an external power supply, making the system suitable for dc motor speed control. by connecting a feedback resistor and capacitor from the error amplifier output pin to the inverted input pin, you can form any desired loop gain, for stable phase compensation. (4) pwm comparator ? ch1 & ch2 the pwm comparators in these channels are a voltage comparator with two inverted input and one non-inverted input, that is, a voltage-pulse width converter to control the output pulse on-time according to the input voltage. it turns on the output transistor when the triangular wave from the oscillator is higher than both the error amplifier output and the dtc-pin voltages. ? ch3 & ch4 the pwm comparators in these channels are a voltage comparator with one inverted input and two non-inverted inputs, that is, a voltage-pulse width converter to control the output pulse on-time according to the input voltage. it turns on the output transistor when the triangular wave from the oscillator is lower than both the error amplifier output and the dtc-pin voltages. these four channels can be provided with a soft start function by using the dtc pin. (5) output circuit the output circuit is comprised of a totem-pole configuration and can drive a pnp transistor (30 ma max.)
7 MB3785a 2. channel control function the MB3785a allows the four channels of power supply circuits to be controlled independently. set the voltage levels on the ctl1 (pin 20), ctl2 (pin 21), and ctl3 (pin 22) terminals to turn the circuit of each channel on or off, as listed below. table 1 channel by channel on/off setting conditions. * : the power supply current value during standby is 10 m a or less. 3. protective functions (1) timer/latch-actuated short-circuiting protection circuit the scp comparator checks the output voltage of each comparator which is used to detect the short-circuiting of output. when any of these comparators have an output voltage greater than or equal to 2.1 v, the timer circuit is activated and a protection enable capacitor externally fitted to the scp terminal (pin 23) begins to charge. if the comparators output voltage is not restored to normal voltage level by the time the capacitor voltage has risen to the base-emitter junction voltage of the transistor, i.e., v be ( @ 0.65 v), the latch circuit is activated to turn off the output transistor while at the same time setting the duty (off) = 100 %. when actuated, this protection circuit can be reset by turning on the power supply again. (2) under voltage lockout protection circuit a transient state at power-on or a momentary drop of the power supply voltage causes the control ic to malfunction, resulting in system breakdown or deterioration. by detecting the internal reference voltage with respect to the power supply voltage, this protection circuit resets the latch circuit to turn off the output transistor and set the duty (off) = 100 %, while at the same time holding the scp terminal (pin 23) at the l. the reset is cleared when the power supply voltage becomes greater than or equal to the threshold voltage level of this protection circuit. ctl pin voltage level on/off state of channel ctl1 ctl2 ctl3 power supply circuit first channel second channel 3rd and 4th chan- nels h h h on on on l off l h off on l off l x standby state*
8 MB3785a n absolute maximum ragings (see warning) (ta = +25 c) * : the packages are mounted on the epoxy board (4 cm 4 cm). warning: permanent device damage may occur if the above absolute maximum ratings are exceeded. functional operation should be restricted to the conditions as detailed in the operational sections of this data sheet. exposure to absolute maximum rating conditions for extended periods may affect device reliability. n recommended operating conditions (ta = +25 c) * : the minimum value of the recommended supply voltage is 3.6 v except when the device operates with constant output sink current. parameter symbol conditions rating unit power supply voltage v cc 20v control input voltage v ictl 20v power dissipation p d ta +25 c 550* mw operating ambient temperature t op C30 to 85 c storage temperature t stg C55 to 125 c parameter symbol conditions value unit min. typ. max. power supply voltage* v cc 4.56.018v error amp. input voltage v i C0.2v cc C0.8 v comparator input voltage v i C0.2v cc v control input voltage v ictl C0.2 18 v output current i o 3.030ma timing capacitance c t 68 1500 pf timing resistance r t 5.1 100 k w oscillation frequency f osc 100 500 1000 khz operating ambient temperature t op C30 25 85 c
9 MB3785a n electrical characteristics (v cc = +6 v, ta = +25 c) (continued) parameter symbol conditions value unit min. typ. max. reference voltage v ref i or = C1 ma 2.475 2.500 2.525 v rate of changed in output voltage vs. temperature d v ref /v ref ta = C30c to +85c C2 0.2 2 % input stability line v cc = 3.6 v to 18 v C10 C2 10 mv load stability load i or = C0.1 ma to C1 ma C10 C3 10 mv sort-circuit output current i os v ref = 2 v C25 C8 C3 ma threshold voltage v th 2.72 v v tl 2.60 v hysteresis width v hys 80 120 mv reset voltage (v cc )v r 1.51.9v input threshold voltage v th 2.45 2.50 2.55 v input bias current i ib v i = 0 v C200 C100 na input voltage range v i C0.2 v cc v input offset voltage v io 0.58 0.65 0.72 v input bias current i ib v i = 0 v C200 C100 na common mode input voltage range v icm C0.2 v cc C1.8 v threshold voltage v tpc 0.60 0.65 0.70 v input standby voltage v stb 50100mv input latch voltage v i 50100mv input source current i lbpc C1.4 C1.0 C0.6 m a oscillation frequency f osc c t = 300 pf, r t = 6.2 k w 450 500 550 khz frequency stability (v cc ) d f/f dv v cc = 3.6 v to 18 v 1 % frequency stability (ta) d f/f dt ta = C30c to +85c C4 4 % reference voltage block under voltage lockout protection circuit (u.v.l.o) short-circuit detection comparator 1 ch/2 ch 3 ch/4 ch short circuit detection block triangular waveform oscillator block
10 MB3785a (continued) (v cc = +6 v, ta = +25 c) parameter symbol conditions value unit min. typ. max. input offset voltage v io v fb = 1.6 v C10 10 mv input bias current i ib v fb = 1.6 v C200 C100 na common mode input voltage range v icm C0.2 v cc C1.8 v voltage gain a v 60 100 db frequency bandwidth bw a v = 0 db 800 khz input threshold voltage v t0 duty cycle = 0 % 1.9 2.25 v v t100 duty cycle = 100 % 1.05 1.3 v input bias current i ibdt v dt = 2.3 v 0.1 0.5 m a latch mode source current i idt v dt = 1.5 v C500 C80 m a latch input voltage v idt i dt = C40 m a v ref C 0.3 2.4 v input threshold voltage v t0 duty cycle = 0 % 1.05 1.3 v v t100 duty cycle = 100 % 1.9 2.25 v input bias current i ibdt v dt = 2.3 v 0.1 0.5 m a latch mode source current i idt v dt = 1.5 v 80 500 m a latch input voltage v idt i dt = +40 m a0.20.3v threshold voltage v th 0.71.42.1v input current i ih v ctl = 5 v 100 200 m a i il v ctl = 0 v C10 10 m a source current i o C40 ma sink current i o r e = 82 w 18 30 42 ma output leakage current i lo v o = 18 v 20 m a standby current i cc0 010 m a supply current when output off i cc 68.6ma error amplifier 1 ch/2 ch dead time control circuit 3 ch/4 ch dead time control circuit channel control block output block general
11 MB3785a n typical characteristic curves (continued) 1. supply current vs. supply voltage supply current i cc (ma) 10 8 6 4 2 0 04 8121620 supply voltage v cc (v) ta = +25? ctl1 = 6 v ctl1, 2 = 6 v, ctl1, 2, 3 = 6 v 5 4 3 2 1 0 04 8121620 supply voltage v cc (v) reference voltage v ref (v) ta = +25? 2. reference voltage vs. supply voltage 3. reference voltage and output current setting pin voltage vs. supply voltage reference voltage v ref (v) 5 4 3 2 1 012 34 5 v ref v e supply voltage v cc (v) 5 4 3 2 1 voltage on output current ?setting pin v e (v) ta = +25? 2.54 2.52 2.50 2.48 2.46 2.44 2.56 ?0 ?0 ?0 0 20 40 60 80 100 v cc = 6 v v ctl1, 2,3 = 6 v i or = ? ma reference voltage v ref (v) 4. reference voltage vs. ambient temperature ambient temperature t a (?) 2.0 5. reference voltage vs. control voltage reference voltage v ref (v) 3.0 2.8 2.4 2.6 2.2 012 34 5 v cc = 6 v ta = +25? control voltage v ctl1 (v) v cc = 6 v ta = +25? 6. control current vs. control voltage control current i ctl1 ( m a) 500 400 300 200 100 0 04 8121620 control voltage v ctl1 (v)
12 MB3785a (cont i nued) ( c on t i n u ed ) 7. triangular wave maximum amplitude voltage vs. timing capacitance 2.4 2.2 2.0 1.8 1.6 1.4 1.2 1.0 0 50 10 2 5 10 2 10 3 5 10 3 10 4 5 10 4 10 5 timing capacitance c t (pf) triangular - wave maximum amplitude voltage v max (v) v cc = 6 v rt = 10 k ta = +25? 8. triangular wave frequency vs. timing resistance 5 m 1 m 100 k 50 k 10 k 5 k 1 k 5 k10 k 50 k100 k 500 k 1 m triangular wave frequency f osc (hz) v cc = 6 v ta = +25? timing resistance r t ( w ) 500 k c t = 68 pf c t = 150 pf c t = 300 pf c t = 1500 pf c t = 15000 pf 9. triangular wave cycle vs. timing capacitance v cc = 6 v r t = 10 k w ta = +25? 100 50 10 5 1 0.5 0.2 10 10 2 5 10 2 10 3 5 10 3 10 4 5 10 4 triangular wave cycle t osc ( m sec) timing capacitance c t (pf) 10. duty vs. triangular wave frequency v cc = 6 v v dt = 1.60 v ta = +25? 100 80 60 40 20 0 5 k 10 k 50 k 100 k 500 k 1 m triangular wave frequency (hz) duty dtr (%) ch 1 11. rate of change in triangular wave frequency vs. ambient temperature (not using ceramic resonator) rate of change in triangular wave frequency (%) ambient temperature ta (?) 10 5 0 ? ?0 ?0 ?0 0 2 0 4 0 6 0 8 0 100 v cc = 6 v f osc = 460 khz (r t = 6.8 k, c t = 280 pf) 12. rate of change in triangular wave frequency vs. ambient temperature (using ceramic resonator) rate of change in triangular wave frequency (%) ambient temperature ta (?) 10 5 0 ? ?0 ?0 ?0 0 2 0 4 0 6 0 8 0 100 v cc = 6 v f osc = 450 khz (r t = 8.5 k w , c t = 250 pf)
13 MB3785a (continued) 13. gain vs. frequency and phase vs. frequency gain av (db) frequency f (hz) phase f (deg) a j f 40 20 0 ?0 ?0 1 k 10 k 100 k 1 m 10 m 180 90 0 ?0 ?80 ta = +25? 14. error amp maximum output voltage vs. frequency error amp maximum output voltage amplitude (v) triangular wave frequency f osc (hz) 3.0 2.0 1.0 0 100 500 1 k 1 m 5 k 10 k 50 k 100 k 500 k v cc = 6v ta = +25? ch 1 10 m f 4.7 k w 4.7 k w 4.7 k w 4.7 k w 240 k w + out in + 2.5 v 2.5 v error amp [measuring circuit] 15. power dissipation vs. ambient temperature power dissipation pd (mw) ambient temperature ta (?) lqfp 1000 800 600 550 400 200 0 ?0 0 20 40 60 80 100 ?0
14 MB3785a n methods of setting the output voltage 1. method of connecting channels 1 and 2: when output voltage (v o ) is positive 2. method of connecting channels 1 and 2: when output voltage (v o ) is negative v ref r r r 1 r 2 r nf v out + v o + = v ref 2 r 2 (r 1 + r 2 ) + + v ref r r r 1 r 2 r nf v o ? = v ref 2 r 1 (r 1 + r 2 ) + v ref v out ?
15 MB3785a 3. method of connecting channels 3 and 4: when output voltage (v o ) is positive 4. method of connecting channels 3 and 4: when output voltage (v o ) is negative v ref r r r 1 r 2 r nf v out v o + = v ref 2 r 2 (r 1 + r 2 ) + v ref rr 1 r 2 r nf v out v o ? = v ref 2 r 1 (r 1 + r 2 ) + v ref + r
16 MB3785a n method of setting the output current the output circuit is comprised of a totem-pole configuration. its output current waveform is such that the on-current value is set by constant current and the off-current value is set by a time constant as shown in figure 2. these output currents are set using the equations below. ? on-current = 2.5/r e [a] (voltage on output current-setting pin v e = 2.5 v) ? off-current time constant = proportional to the value of c b figure 1. ch1 to ch4 output circuit figure 2. output current waveform figure 3. voltage and current waveforms figure 4. measuring circuit diagram on output pin (ch1) drive transistor c b off-current off-current setting block on-current r e v e 0 t output current on-current off-current 10 0 v o (v) 40 20 0 ?0 ?0 i o (ma) 0 0.4 0.8 1.2 1.6 2.0 t ( m s) v cc = 10 v 1000 pf v cc MB3785a i o v o 8 pin 7 pin (5 v) 22 m h 10 m f 8.2 k 2.7 k 570 pf 82 w 48 1 45 46 47
17 MB3785a n method of setting time constant for timer/latch-actuated short- circuting protection circuit figure 5 schematically shows the protection latch circuit. the outputs from the output-shorting detection comparators 1 to 4 are respectively connected to the inverted inputs of the scp comparator. these inputs are always compared with the reference voltage of approximately 2.1 v which is fed to the non-inverted input of the scp comparator. while the switching regulator load conditions are stable, there are no changes in the outputs of the comparators 1 to 4 so that short-circuit protection control keeps equilibrium state. at this time, the voltage on the scp terminal (pin 23) is held at approximately 50 mv. when load conditions change rapidly due to a short-circuiting of load, for example, the output voltage of the comparator for the relevant channel goes h (2.1 v or more). consequently, the scp comparator outputs a l, causing the transistor q 1 to turn off, and the short-circuit protection capacitor c pe (externally fitted to the scp terminal) begins to charge. v pe = 50 mv + t pe 10 C6 /c pe 0.65 = 50 mv + t pe 10 C6 /c pe c pe = t pe /0.6 (sec) when the external capacitor c pe is charged to approximately 0.65 v, the sr latch is set and the output drive transistor is turned off. simultaneously, the dead time is extended to 100% and the output voltage on the scp terminal (pin 23) is held l. as a result, the s-r latch input is closed and c pe is discharged. figure 5. protection latch circuit comparator 1 comparator 2 comparator 3 comparator 4 2.1 v q 1 q 2 c pe 1 m a sr latch u.v.l.o pwm comparator out 2.5 v 23 +
18 MB3785a n treatment when not using scp when you do not use the timer/latch-actuated short-circuiting protection circuit, connect the scp terminal (pin 23) to gnd with the shortest distance possible. also, connect the comparators input terminal for each channel to the v cc1 terminal (pin 18). figure 6. treatment when not using scp v cc 1 ?n1 (c) ?n2 (c) ?n3 (c) ?n4 (c) 18 8 13 24 29 23
19 MB3785a n method of setting the triangular-wave oscillator circuit 1. when not using ceramic resonator connect the osc in terminal (pin 14) to gnd and leave the osc out terminal (pin 15) open. this makes it possible to set the oscillation frequency with only c t and r t . 2. when using ceramic resonator by connecting a ceramic resonator between osc in and osc out as shown below, you can set the oscillation frequency. in this case, too, c t and r t are required. determine the values of c t and r t so that the oscillation frequency of this rc network is about 5-10% lower than that of the ceramic resonator. figure 7. when not using ceramic resonator 14 15 16 17 osc in r t c t osc out r t c t open figure 8. when using ceramic resonator 14 15 16 17 osc in r t c t osc out r t c t c 2 c 1 ceramic resonator
20 MB3785a when the oscillation rise time at power switch-on is compared between a ceramic and a crystal resonator, it is known that the crystal resonator is about 10 to 100 times slower to rise than the ceramic resonator. therefore, when a crystal resonator is used, system operation as a switching regulator at power switch-on becomes unstable. to avoid this problem, it is recommended that you use a ceramic oscillator because it has a short rise time and, hence, ensures stable operation. ? crystal resonator turn-on characteristic ? ceramic resonator turn-on characteristic 012345 2.0 1.5 1.0 v ct (v) t ( msec ) 012345 2.0 1.5 1.0 v ct (v) t (msec)
21 MB3785a n method of setting the dead time and soft start 1. dead time when the device is set for step-up inverted output based on the flyback method, the output transistor is fixed to a full-on state (on-duty = 100 %) at power switch-on. to prevent this problem, you may determine the voltages on the dtc terminals (pins 4, 9, 28, and 33) from the v ref voltage so you can easily set the output transistors dead time (maximum on-duty) independently for each channel as shown below. (1) ch1 and ch2 channels when the voltage on the dtc terminals (pins 4 and 9) is higher than the triangular-wave output voltage from the oscillator, the output transistor turns off. the dead time calculation formula assuming that triangular-wave amplitude @ 0.6 v and triangular-wave minimum voltage @ 1.3 v is given below. when you do not use these dtc terminals, connect them to gnd. (2) ch3 and ch4 channels when the voltage on the dtc terminals (pins 28 and 33) is lower than the triangular-wave output voltage from the oscillator, the output transistor turns off. the dead time calculation formula assuming that traingular-wave amplitude @ 0.6 v and triangular-wave maximum voltage @ 1.9 v is given below. when you do not use these dtc terminals, connect them to v ref . duty (off) = 100 [%], v dt = v ref v dt C 1.3 r 1 + r 2 r 2 0.6 figure 9. when using dtc to set dead time figure 10. when not using dtc v ref r 1 r 2 dtc1 (dtc2) vdt 19 dtc1 (dtc2) duty (off) @ 100 [%], v dt = v ref 1.9 Cv dt r 1 + r 2 r 2 0.6
22 MB3785a when you use a ceramic resonator, pay attention when setting the dead time because the triangular-wave amplitude is determined by the values of c t and r t . 2. soft start to prevent inrush current at power switch-on, the device can be set for soft start by using the dtc terminals (pins 4, 9, 28, and 33). the diagrams below show how to set. figure 11. when using dtc to set dead figure 12. when not using dtc time v ref r 1 r 2 dtc3 (dtc4) vdt 19 v ref dtc3 (dtc4) 19 figure 13. setting soft start for ch1 and figure 14. setting soft start for ch3 and ch2 ch4 v ref dtc1 (dtc2) rdt 19 cdt rdt cdt dtc3 (dtc4) 19 v ref
23 MB3785a it is also possible to set soft start simultaneously with the dead time by configuring the dtc terminals as shown below. figure 15. setting dead time and soft start figure 16. setting dead time and soft start for ch1 and ch2 for ch3 and ch4 v ref r 1 r 2 dtc1 (dtc2) cdt 19 v ref r 1 r 2 dtc3 (dtc4) cdt 19
24 MB3785a n equivalent series resistor and stability of smoothing capacitor the equivalent series resistance (esr) of a smoothing capacitor in a dc/dc converter greatly affects the phase characteristics of the loop depending on its value. system stability is improved by esr because it causes the phase to lead that of the ideal capacitor in high-frequency regions. (see figures 17 and 19.) conversely, if a low-esr smoothing capacitor is used, system stability deterio- rates. therefore, use of a low-esr semiconductor electrolytic capacitors (os C con) or tantalum capacitors calls for careful attention. figure 17. basic circuit of stepdown dc/dc converter figure 18. gain-frequency characteristic figure 19. phase-frequency characteristic tr l c v in r c r l d 20 0 C20 C40 C60 10 100 1 k 10 k 100 k gain (db) frequency f (hz) (2) (1) : r c = 0 w (2) : r c = 31 m w (1) 0 C90 C180 10 100 1 k 10 k 100 k phase (deg) frequency f (hz) (1) : r c = 0 w (2) : r c = 31 m w (2) (1)
25 MB3785a (reference data) the phase margin is halved by changing the smoothing capacitor from an aluminum electrolytic capacitor (r c = 1.0 w ) to a small-esr semiconductor electrolytic capacitor (os C con; r c = 0.2 w ). (see figure 21 and 22.) figure 20. dc/dc converter av- f characteristic measuring circuit figure 21. gain-frequency characteristic figure 22. phase-frequency characteristic v out v o + c nf fb v ref /2 r 1 r 2 v in av characteristic between this interval error amp + ?n +in v cc = 10 v r l = 25 w c p = 0.1 m f a v 62 j 60 40 20 0 ?0 ?0 10 100 1 k 10 k 100 k 180 90 0 ?0 ?80 gain (db) phase (deg) frequency f (hz) + v o + gnd al electrolytic capacitor 220 m f (16 v) r c @ 1.0 w : f osc = 1 khz gain - frequency and phase frequency characteristics of al electrolytic capacitor (dc/dc converter +5 v output) v cc = 10 v r l = 25 w c p = 0.1 m f j 27 a v 60 40 20 0 ?0 ?0 10 100 1 k 10 k 100 k 180 90 0 ?0 ?80 fre q uenc y f ( hz ) gain (db) phase (deg) v o + gnd + os ?con 22 m f (16 v) r c @ 0.2 w : f osc = 1 khz gain - frequency and phase frequency characteristics of os ?con (dc/dc converter +5 v output)
26 MB3785a n example of application circuit chi ch2 ch3 ch4 v cc a 7 33 m f +in ?n fb rfb 150 k w 4.7 k w 4.7 k w 33 k w b c 6 5 8 4 12 11 10 dtc 27 k w 1 m f +in ?n fb rfb 150 k w 4.7 k w 4.7 k w d 27 k w dtc 1 m f 33 k w 13 9 26 25 27 28 e f +in ?n fb rfb 150 k w dtc 24 10 k w g h motor control signal ?n fb rfb 150 k w dtc 10 k w v ref 30 31 32 29 33 19 23 scp 0.1 m f 1 48 45 46 47 3 2 43 34 35 40 41 36 37 39 38 42 22 20 21 17 16 15 14 18 1000 pf 1000 pf out v cc 250 w 1000 pf 1000 pf 1000 pf 250 w out 1000 pf 1000 pf 250 w out 1000 pf 250 w v cc gnd 22 m h 300 pf ctl1 ctl2 ctl3 rt ct 6.2 k 10 ma 8.2 k w 2.7 k w dc motor 10 m f 10 ma g h e 8.2 k w 2.7 k w dc motor 22 m h 10 m f f 22 m h 10 m f 8.2 k w 2.7 k w a b 5 v 10 m h 33 m f 10 ma 24 v 15 m f 20 k w 1.8 k w 15 v 44 out 10 ma output control signals ceramic resonator motor control signal d c +in
27 MB3785a n precautions on using the device 1. do not input voltages greater than the maximum rating. inputting voltages greater than the maximum rating may damage the device. 2. always use the device under recommended operating c onditions. if a voltage greater than the maximum value is input to the device, its electrical characteristics may not be guaranteed. similarly, inputting a voltage below the minimum value may cause device operation to become unstable. 3. for grounding the printed circuit board, use as wide ground lines as possible to prevent high-frequency noise. because the device uses high frequencies, it tends to generate high-frequency noise. 4. take the following measures for protection against static charge: ? for containing semiconductor devices, use an antistatic or conductive container. ? when storing or transporting device-mounted circuit boards, use a conductive bag or container. ? ground the workbenches, tools, and measuring equipment to earth. ? make sure that operators wear wrist straps or other appropriate fittings grounded to earth via a resistance of 250 k to 1 m ohms placed in series between the human body and earth. n ordering information part number package remarks MB3785apfv 48-pin plastic lqfp (fpt-48p-m05)
28 MB3785a n package dimension 48-pin plastic lqfp (fpt-48p-m05) c 1995 fujitsu limited f48013s-2c-5 0.10(.004) 0.500.08 (.0197.0031) 9.000.20(.354.008)sq 5.50 (.217) ref 8.00 (.315) nom .007 .001 +.003 0.03 +0.08 0.18 .005 .001 +.002 0.02 +0.05 0.127 .059 .004 +.008 0.10 +0.20 1.50 7.000.10(.276.004)sq "a" 0.500.20 (.020.008) 0.100.10 (.004.004) details of "a" part 0 10? 25 24 13 12 1 48 37 36 index lead no. (stand off) (mounting height) dimensions in: mm (inches)
32 MB3785a fujitsu limited for further information please contact: japan fujitsu limited corporate global business support division electronic devices kawasaki plant, 4-1-1, kamikodanaka nakahara-ku, kawasaki-shi kanagawa 211-8588, japan tel: (044) 754-3763 fax: (044) 754-3329 http://www.fujitsu.co.jp/ north and south america fujitsu microelectronics, inc. semiconductor division 3545 north first street san jose, ca 95134-1804, usa tel: (408) 922-9000 fax: (408) 922-9179 customer response center mon. - fri.: 7 am - 5 pm (pst) tel: (800) 866-8608 fax: (408) 922-9179 http://www.fujitsumicro.com/ europe fujitsu mikroelektronik gmbh am siebenstein 6-10 d-63303 dreieich-buchschlag germany tel: (06103) 690-0 fax: (06103) 690-122 http://www.fujitsu-ede.com/ asia pacific fujitsu microelectronics asia pte ltd #05-08, 151 lorong chuan new tech park singapore 556741 tel: (65) 281-0770 fax: (65) 281-0220 http://www.fmap.com.sg/ f9803 ? fujitsu limited printed in japan all rights reserved. the contents of this document are subject to change without notice. customers are advised to consult with fujitsu sales representatives before ordering. the information and circuit diagrams in this document presented as examples of semiconductor device applications, and are not intended to be incorporated in devices for actual use. also, fujitsu is unable to assume responsibility for infringement of any patent rights or other rights of third parties arising from the use of this information or circuit diagrams. fujitsu semiconductor devices are intended for use in standard applications (computers, office automation and other office equipment, industrial, communications, and measurement equipment, personal or household devices, etc.). caution: customers considering the use of our products in special applications where failure or abnormal operation may directly affect human lives or cause physical injury or property damage, or where extremely high levels of reliability are demanded (such as aerospace systems, atomic energy controls, sea floor repeaters, vehicle operating controls, medical devices for life support, etc.) are requested to consult with fujitsu sales representatives before such use. the company will not be responsible for damages arising from such use without prior approval. any semiconductor devices have inherently a certain rate of failure. you must protect against injury, damage or loss from such failures by incorporating safety design measures into your facility and equipment such as redundancy, fire protection, and prevention of over-current levels and other abnormal operating conditions. if any products described in this document represent goods or technologies subject to certain restrictions on export under the foreign exchange and foreign trade control law of japan, the prior authorization by japanese government should be required for export of those products from japan.

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