description the sp3842/3843 series are high performance fixed frequency current mode controllers. they are s pecifically designed for off-line and dc-to-dc converter applications offering the designer a cost effective solution with minimal external components. these integrated circuits feature a trimm ed oscillator for precise duty cycle control, a te mperature compensated reference, high gain error amplifier, current sensing comparator, and a high current totem pole output ideally suited for driving a power mosfet. also included are protective features consisting of input and reference under voltage lockouts each with hyst eresis, cycle-by-cycle current limiting, programmable output dead time, and a latch for single pulse metering. these devices are available in 8-pin dual-in-line ceramic and plastic packages as well as the 14-pin plastic su rface mount (so-14). the so-14 package has separate power and ground pins for the totem pole output stage. difference between members of this series is the under-voltage lockout thresholds. the sp3842 has uvlo thresholds of 16 v (on) and 10 v (off), ideally suited for off-line converters. the corresponding thresholds for the SP3843 are 8.5 v and 7.9 v. features ? trimmed oscillator discharge current for precise duty cycle control ? current mode operation to 500 khz ? automatic feed forward compensation ? latching pwm for cycle-by-cycle current limiting ? internally trimmed reference with under voltage lockout ? high current totem pole output ? under voltage lockout with hysteresis ? low start-up and operating current ? direct interface with motorola sensefet products pin configurations (top view) SP3843 1 of 8 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
pin function description pin no. function description 8-pin 1 compensatio n this pin is the error amplifier out put and is made available for loop compensation. 2 voltage feedback this is the inverting input of the e rror amplifier. it is normally connected to the switching power supply output through a resistor divider. 3 current sense a voltage proportional to inductor curr ent is connected to this input. the pwm uses this information to termi nate the output swit ch conduction. 4 r t /c t the oscillator frequency and maxi mum output duty cycle are programmed by connecting resistor r t to vref and capacitor c t to ground. operation to 500 khz is possible. 5 gnd this pin is the combined control circuitry and power ground (8-pin package only). 6 output this output directly drives the gat e of a power mosfet. peak currents up to 1.0 a are sourced a nd sunk by this pin. 7 v cc this pin is the positive s upply of the control ic. 8 v ref this is the reference output. it prov ides charging current for capacitor c t through resistor r t . block diagram SP3843 2 of 8 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
maximum ratings rating symbol value unit total power supply and zenger current (i cc +i z ) 30 ma output current, source or sink (note 1) i o 1.0 a output energy (capacitive load per cycle) w 5.0 ? j current sense and voltage feedback inputs v in -0.3 to +5.5 v error amp output sink current i o 10 ma power dissipation and thermal characteristics nf suffix, plastic package maximum power dissipation @ t a =25c p d 862 mw thermal resistance junction to air r ja 145 c/w n suffix, plastic package maximum power dissipation @ t a =25c p d 1.25 w thermal resistance junction to air r ja 100 c/w operating junction temperature t j +150 c operating ambient temperature t a c sp3842/3843 0 to +70 storage temperature range tstg -65 to +150 c electrical characteristics (vcc=15 v [note 2], rt=10 k, ct=3.3 nf, ta=tlow to thigh [note 3] unless otherwise noted) characteristic sp3842/3843 symbol min typ max unit reference section reference output voltage (i 0 =1.0 ma, t j =25c) v ref 4.9 5.0 5.1 v line regulation (v cc = 12 v to 25 v) reg line ? 2.0 20 mv load regulation (i 0 =1 ma to 20 ma) reg load ? 3.0 25 mv temperature stability t s ? 0.2 ? mv/c total output variation over line, load, and temperature v ref 4.82 ? 5.18 v output noise voltage (f=10 hz to 10 khz, t =25c) v n ? 50 ? ? v SP3843 3 of 8 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
long term stability ( t a =125c for 1000 hours) s ? 5.0 ? mv output short circuit current i sc -30 -85 -180 ma oscillator section frequency f osc khz t j =25c 47 52 57 t a =t low to t high 46 ? 60 frequency change with voltage (v cc = 12 v to 25 v) ? f osc / v ? 0.2 1.0 % frequency change with temperature ? f osc / v ? 5.0 ? % t a =t low to t high oscillator voltage swing (peak-to-peak) v osc ? 1.6 ? v discharge current (v osc =2.0 v) i dischg ma t j =25c 7.5 8.4 9.3 t a =t low to t high 7.2 ? 9.5 notes: 1. maximum package power dissipation limits must be observed. 2. adjust vcc above the start-up threshold before setting to 15 v. 3. low duty cycle pulse techniques are used during test to maintain junction temperature as close to ambient as possible. tlow = 0c thigh = +70c 4. this parameter is measured at the latch trip point with vfb = 0 v. 5. comparator gain is defined as: av = input sense current on compensati output / v v ? ? electrical characteristics (vcc=15 v [note 2], rt=10 k, ct=3.3 nf, ta=tlow to thigh [note3] unless otherwise noted) characteristic sp3842/3843 symbol min typ max unit error amplifier section voltage feedback input (v 0 =2.5 v) v fb 2.42 2.5 2.58 v input bias current (v fb =2.7 v) i ib ? -0.1 -2.0 ? a open-loop voltage gain (v 0 =2.0 v to 4.0 v) a vol 65 90 ? db unity gain bandwidth (t j =25c) bw 0.7 1.0 ? mhz power supply rejection ratio (v cc =12 v to 25 v) psrr 60 70 ? db output current ma SP3843 4 of 8 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
sink (v 0 =1.1 v, v fb =2.7 v) i sink 2.0 12 ? source (v 0 =5.0 v, v fb =2.3 v) i source -0.5 -1.0 ? output voltage swing v high state (r l =15 k to ground, v fb =2.3 v) v oh 5.0 6.2 ? low state (r l =15 k to vref, v fb =2.7 v) v ol ? 0.8 1.1 current sense section current sense input voltage gain (notes 4 & 5) a v 2.85 3.0 3.15 v/v maximum current sense input threshold (note 4) v th 0.9 1.0 1.1 v power supply rejection ratio psrr ? 70 ? db v cc =12 v to 25v, note 4 input bias current i ib ? -2.0 -10 ? a propagation delay (current sense input to output) t plh(in/out) ? 150 300 ns output section output voltage v low state (i sink =20 ma) v ol ? 0.1 0.4 (i sink =200 ma) ? 1.6 2.2 high state (i source =20 ma) v oh 13 13.5 ? (i source =200 ma) 12 13.4 ? output voltage with uvlo activated v cc =6.0 v, i sink =1.0 ma v ol ( uvlo ) ? 0.1 1.1 v output voltage rise time (c l =1.0 nf, t j =25c) t r ? 50 150 ns output voltage fall time (c l =1.0 nf, t j =25c) t f ? 50 150 ns undervoltage lockout section start-up threshold v th v sp3842/3843 14.5/7.8 16/8.4 17.5/9.0 minimum operating voltage after turn-on v cc(min) v sp3842 8.5 10 11.5 pwm section duty cycle % maximum dc max 94 96 ? minimum dc min ? ? 0 total device power supply current i cc ma start-up ? 0.5 1.0 (v cc =14 v for sp3842 /v cc =6.5 v for SP3843 ) operating (note 2) ? 12 17 power supply zener voltage (i cc =25 ma) v z 30 36 ? v SP3843 5 of 8 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
typical applications line regulation 5.0v v in =95 to 130 vac ? = 50 mv or 0.5% 12 v ? = 24 mv or 0.1% load regulation 5.0 v v in =115 vac, iout= 1.0 a to 4.0 a ? = 300 mv or 3.0% 12v v in =115 vac, iout = 100 ma to 300 ma ? = 60 mv or 0.25% output ripple 5.0 v v in =115 vac 40 mvp.p 12v 80 mvp-p efficiency v in =115 vac 70% all outputs are at nominal load currents unless otherwise noted. SP3843 6 of 8 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
package description SP3843 7 of 8 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
SP3843 8 of 8 4008-318-123 sales@twtysemi.com http://www.twtysemi.com product specification
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