pulse-width-modulation control circuits TL494 features complete pwm power control circuitry uncommitted outputs for 200 ma sink or source current output control selects single-ended or push-pull operation internal circuitry prohibits double pulse at either output variable dead-time provides control over total range internal regulator provides a stable 5-v reference supply,5% circuit architecture allows easy synchronization moisture sensitivity level 3 description the TL494 incorporate on a single monolithic chip all the functions required in the construction of a pulse-width-modulation control, these devices offer the systems engineer the flexibility to tailor ordering information the power supply control circuitry to his application. the TL494 contains an error amplifier, an on-chip adjustable oscillator, a dead-time control comparator, pulse-steering control flip-flop, a 5-volt, 5% precision regulator, and output-control circuit. the error amplifier exhibits a common-mode voltage range from -0.3 volts to vcc -2 volts. the dead-time control comparator has a fixed offset that provides approximately 5% dead time when externally altered. the on-chip oscillator may be bypassed by terminating r t (pin 6) to the reference output and providing a sawtooth in put to ct (pin 5), or it may be used to drive the common circuits in synchronous multiple-rail power supplies. the uncommited output transistors provide either common-emitter or emitter-follower output capability. each device provides for push-pull or single-ended output operation, which may be selected through the output-control funct -ion. the architecture of these devices prohibits the possibility of either output being pulsed twice during push -pull operation. functional block diagram 2008 - ver. 1.2 htc TL494n 16 dip 1 / 6 device package TL494d 16 sop sop16/dip16 (top view) 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 noninv input inv input feedbac k dead-time control ct rt gnd c1 noninv input inv input ref out vcc c2 e2 e1 output control error amp 1 error amp 2 oscillator reference r t c t dead time control 0.1v dead-time control comparator pwm comparator feedback error amplifier error amplifier noninverting input inverting input noninverting input inverting input + - 2 1 + - c1 pulse-steering flip-flop q1 q2 c1 e1 c2 e2 vcc vref gnd output control
pulse-width-modulation control circuits TL494 2008 - ver. 1.2 htc 2 / 6 parameter measurement information dead-time feedback r t c t (+) (-) output control ref out e2 c2 e1 c1 vcc gnd (+) (-) error vcc = 15v 150 2w 150 2w output 1 output 2 test inputs 12k 0.01uf 50k test circuit voltage at c1 voltage at c2 voltage at c t dead-time control input feedback duty circle 0.7 v 0 v threshold voltage 0% max threshold voltage 0% 0 vcc 0 vcc figure 1. operational test circuit and waveforms
pulse-width-modulation control circuits TL494 2008 - ver. 1.2 htc 3 / 6 + - + - vref other amplifier feedback terminal amplifier under test figure 2. amplifier characteristics test circuit (each output circuit) output c l =15pf (includes probe and jig capacitance) 15 v 68 2 w 90% 10% 90% 10% t f t r output voltage waveform figure 3. common-emitter configuration test circuit (each output circuit) 15 v c l =15pf (includes probe and jig capacitance) 68 2 w 90% 90% 10% 10% t f t r output voltage waveform figure 4. emitter-follower configuration
pulse-width-modulation control circuits TL494 absolute maximum ratings over operating free-air temperature range recommended operating conditions electrical characteristics over recommended operatng free-air temperature range, vcc=15v, f= 10 khz(unless otherwise noted). oscillator section (see figure 1) 2008 - ver. 1.2 htc 1 t a = min to max 4 / 6 frequency change with temperature**** c t =0.01 f, r t =12k ? , khz standard deviation of frequency**** 10 % frequency change with voltage 0.1 frequency 10 ma parameter test conditions* value unit min typ** max short-circuit output current*** vref = 0 35 unit v mv output voltage change with temperature t a = min to max 0.2 1 % operating free-air temperature, t a -40 85 o c oscillator frequency 1 300 khz parameter value unit v vcc=7v to 40v, t a =25oc unit v ma o c storage temperature range -65 to 150 lead temperature 1,6 mm from case for 10 seconds 260 and t a constant all values of vcc, c t ,r t , c t =0.01 f, r t =12k ? output regulation io = 1ma to 10ma 1 15 4.75 5 5.25 input regulation vcc = 7v to 40 v 2 25 min typ** max output voltage (vref) lo = 1ma parameter test conditions* value timing resistor, r t 1.8 500 k ? timing capacitor, c t 0.47 10000 nf current into feedback terminal 0.3 ma collector output current (each transistor) 200 amplifier input voltage, vi -0.3 vcc -2 collector output voltage, vo 40 min max supply voltage, vcc 7 40 amplifier input voltage vcc +0.3 collector output voltage 41 collector output current 250 operating free-air temperature range -40 to 125 rating value supply voltage, vcc 41
pulse-width-modulation control circuits TL494 electrical characteristics over recommended operating free-air temperature range, vcc=15v, f=10khz (unless otherwise noted) amplifier section (see figure 2) *for conditions shown as min or max, use the appropriate value specified under recommended operating conditions. ** all typical values except for parameter changes with temperature are at ta =25 oc *** duration of the short-circuit should not exceed one second. **** standard deviation is a measure of the statistical distribution about the mean as derived from the formula. ***** temperature coefficient of timing capacitor and timing resistor not taken into account. output section dead-time control-section (see figure 1) pmw comparator section (see figure 1) 2008 - ver. 1.2 htc 5 / 6 average supply current v i (pin 4)= 2v 7.5 610 ma and outputs open v cc =40v 915 standby supply current pin 6 at vref, all other inputs v cc =15v ma total device parameter test conditions min. typ* max. unit input sink current (pin 3) v(pin3) = 0.7v 0.3 0.7 max. unit input threshold voltage (pin3) zero duty cycle 4 4.5 v parameter test conditions min. typ* 3.3 v maximum duty cycle 0 input threshold voltage(pin 4) zero duty cycle 3 -10 ? maximum duty cycle, each output v i (pin 4) =0, c t =0.1uf, r t =12k ? 45 % input bias current(pin4) v i =0 to 5.25v -2 3.5 ma parameter test conditions min. typ* max. unit output control input current v i =vref 1.1 1.3 v emitter-follower vc=15v, i e =-200ma 1.5 2.5 collector-emitter saturation voltage common-emitter v e =0, i c =200ma 100 ? emitter off-state current v cc =v c =40v,v e =0 -100 collector off-state current v ce =40v, vcc=40v 2 ma parameter test conditions min. typ* max. unit output source current (pin 3) v id =15mv~5v, v( pin3 )=3.5v -2 db output sink current (pin 3) v id =-15mv~-5v, v( pin3 )=0.7v 0.3 0.7 ma common-mode rejection ratio vo= 40v, t a = 25 o c 65 80 db unity-gain bandwidth vo=0.5~3.5v, r l =2k ? 800 khz open-loop voltage amplification vo=3v, r l =2k ? , vo=0.5~3.5v 70 95 1 ? common-mode input voltage range vcc = 7v to 40v -0.3~-2 v input bias current vo(pin 3)=2.5v 0.2 10 ? input offset current vo(pin 3)=2.5v 25 250 na input offset voltage vo(pin 3)=2.5v 2 symbol test conditions min. typ**. max. unit
pulse-width-modulation control circuits TL494 switching characteristics, t a = 25 o c 2008 - ver. 1.2 htc * all typical values except for temperature coefficient are at t a = 25 o c 6 / 6 100 200 output voltage fall time 40 100 200 ns output voltage fall time 25 100 output voltage rise time emitter-follower configuration output voltage rise time common-emitter configuration 100 parameter test conditions min. typ* max. unit 1.0 5.0 20 k 50 200 500 1.0 500 1.0 10 k 100 500 t osc - r t timing resistance oscillator frequency t osc (hz) saturation voltage v ce (sat) (v) v ce - i e 0 100 200 300 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 emitter current i e (ma) saturation voltage v ce (sat) (v) 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 v ce ( sat ) - i c 0 100 200 300 collector current i c () open-loop voltage gain a vol (db) 1.1 10 100 1.0k 10k 100k 1.0m frequency f(hz) 0 10 20 30 40 50 60 70 80 90 100 vcc=15v vo=3.0v rl=2.0? 180 160 140 120 100 80 60 40 20 0 excess phase (degrees) supply current icc (ma) 0 5.0 10 15 20 25 30 supply voltage vcc (v) 0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10 35 40 i cc - v cc
|
