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september 2001 1 MIC79050 MIC79050 micrel typical applications li-ion cell 4.2v 0.75% over temp in bat gnd MIC79050-4.2bs regulated or unregulated wall adapter simplest battery charging solution 4.2v 0.75% li-ion cell in bat fb gnd en MIC79050-4.2bmm external pwm* *see applications information regulated or unregulated wall adapter pulse-charging application MIC79050 simple lithium-ion battery charger final information general description the MIC79050 is a simple single-cell lithium-ion battery charger. it includes an on-chip pass transistor for high preci- sion charging. featuring ultrahigh precision ( +0.75% over the li-ion battery charging temperature range) and zero off mode current, the MIC79050 provides a very simple, cost effective solution for charging lithium-ion battery. other features of the MIC79050 include current limit and thermal shutdown protection. in the event the input voltage to the charger is disconnected, the MIC79050 also provides minimal reverse-current and reversed-battery protection. the MIC79050 is a fixed 4.2v device and comes in the thermally-enhanced mso-8, so-8, and sot-223 packages. the 8-pin versions also come equipped with enable and feedback inputs. all versions are specified over the tempera- ture range of C40 c to +125 c. features ? high accuracy charge voltage: 0.75% over -5 c to + 60 c (li-ion charging temperature range) ? zero off-mode current ?10 a reverse leakage ? ultralow 380mv dropout at 500ma ? wide input voltage range ? logic controlled enable input (8-pin devices only) ? thermal shutdown and current limit protection ? power msop-8, power sop-8, and sot-223 ? pulse charging capability applications ? li-ion battery charger ? celluar phones ? palmtop computers ?pdas ? self charging battery packs micrel, inc. ? 1849 fortune drive ? san jose, ca 95131 ? usa ? tel + 1 (408) 944-0800 ? fax + 1 (408) 944-0970 ? http://www.mic rel.com ordering information part number voltage junct. temp. range package MIC79050-4.2bs 4.2v C40 c to +125 c sot-223 MIC79050-4.2bm 4.2v C40 c to +125 c sop-8 MIC79050-4.2bmm 4.2v C40 c to +125 c msop-8
MIC79050 micrel MIC79050 2 september 2001 pin description pin no. pin no. pin name pin function sot-223 sop-8 msop-8 1 2 in supply input 2, tab 5C8 gnd ground: sot-223 pin 2 and tab are internally connected. so-8 pins 5 through 8 are internally connected. 3 3 bat battery voltage output 1 en enable (input): ttl/cmos compatible control input. logic high = enable; logic low or open = shutdown. 4 fb feedback node pin configuration in bat gnd 13 2 ta b gnd MIC79050-x.xbs sot-223 1 2 3 4 8 7 6 5 gnd gnd gnd gnd en in bat fb MIC79050-x.xbm sop-8 and msop-8
september 2001 3 MIC79050 MIC79050 micrel electrical characteristics v in = v bat + 1.0v; c out = 4.7 f, i out = 100 a; t j = 25 c, bold values indicate C 40 c t j +125 c; unless noted. symbol parameter conditions min typical max units v bat battery voltage accuracy variation from nominal v out C 5 c to +60 c C 0.75 +0.75 % ? v bat / ? t battery voltage note 4 40 ppm/ c temperature coefficient ? v bat /v bat line regulation v in = v bat + 1v to 16v 0.009 0.05 %/v 0.1 %/v ? v bat /v bat load regulation i out = 100 a to 500ma, note 5 0.05 0.5 % 0.7 % v in C v bat dropout voltage, note 6 i out = 500ma 380 500 mv 600 mv i gnd ground pin current, notes 7, 8 v en 3.0v, i out = 100 a 85 130 a 170 a v en 3.0v, i out = 500ma 11 20 ma 25 ma i gnd ground pin quiescent current, v en 0.4v (shutdown) 0.05 3 a note 8 v en 0.18v (shutdown) 0.10 8 a psrr ripple rejection f = 120hz 75 db i limit current limit v bat = 0v 750 900 ma 1000 ma ? v bat / ? p d thermal regulation note 9 0.05 %/w enable input v enl enable input logic-low voltage v en = logic low (shutdown) 0.4 v 0.18 v v en = logic high (enabled) 2.0 v i enl enable input current v enl 0.4v (shutdown) 0.01 C 1 a v enl 0.18v (shutdown) 0.01 C2 a i enh v enh 2.0v (enabled) 5 20 a 25 a note 1. exceeding the absolute maximum rating may damage the device. note 2. the device is not guaranteed to function outside its operating rating. note 3. the maximum allowable power dissipation at any t a (ambient temperature) is calculated using: p d(max) = (t j(max) C t a ) ja . exceeding the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. note 4. battery voltage temperature coefficient is the worst case voltage change divided by the total temperature range. note 5. regulation is measured at constant junction temperature using low duty cycle pulse testing. parts are tested for load regulatio n in the load range from 100 a to 500ma. changes in output voltage due to heating effects are covered by the thermal regulation specification. note 6. dropout voltage is defined as the input to battery output differential at which the battery voltage drops 2% below its nominal value measured at 1v differential. note 7: ground pin current is the charger quiescent current plus pass transistor base current. the total current drawn from the supply is the sum of the load current plus the ground pin current. note 8: v en is the voltage externally applied to devices with the en (enable) input pin. [mso-8(mm) and so-8 (m) packages only.] note 9: thermal regulation is the change in battery voltage at a time t after a change in power dissipation is applied, excluding load or line regulation effects. specifications are for a 500ma load pulse at v in = 16v for t = 10ms. absolute maximum ratings (note 1) supply input voltage (v in ) ............................ C 20v to +20v power dissipation (p d ) ............... internally limited, note 3 junction temperature (t j ) ....................... C 40 c to +125 c lead temperature (soldering, 5 sec.) ....................... 260 c storage temperature (t s ) ....................... C 65 c to +150 c operating ratings (note 2) supply input voltage (v in ) ........................... +2.5v to +16v enable input voltage (v en ) .................................. 0v to v in junction temperature (t j ) ....................... C 40 c to +125 c package thermal resistance (note 3) ............................... msop-8 ( ja ) ...................................................... 80 c/w sop-8( ja ) .......................................................... 63 c/w sot-223( jc ) ...................................................... 15 c/w
MIC79050 micrel MIC79050 4 september 2001 typical characteristics 0 100 200 300 400 0 100 200 300 400 500 dropout voltage (mv) output current (ma) dropout voltage vs. output current 0 100 200 300 400 500 600 -40 0 40 80 120 dropout voltage (mv) temperature (c) dropout voltage vs. temperature 0 1 2 3 4 5 0246810121416 output voltage (v) input voltage (v) dropout characteristics 50ma, 150ma 5ma 0 1 2 3 4 5 0246 output voltage (v) input voltage (v) dropout characteristics 250ma 500ma 0 2 4 6 8 10 12 0 100 200 300 400 500 ground current (ma) output current (ma) output current vs. ground 0 0.5 1 1.5 0 4 8 12 16 ground current (ma) supply voltage (v) ground current vs. supply volta g e 50ma 5ma 0 5 10 15 20 25 0123456 ground current (ma) supply voltage (v) ground current vs. supply volta g e 500ma 250ma 125ma 0 50 100 150 -40 0 40 80 120 ground current (ua) temperature (c) ground current vs. temperature 3.0 3.2 3.4 3.6 3.8 4.0 -40 0 40 80 120 ground current (ma) temperature (c) ground current vs. temperature 11.0 11.5 12.0 12.5 13.0 13.5 -40 0 40 80 120 ground current (ma) temperature (c) ground current vs. temperature 4.190 4.195 4.200 4.205 4.210 -40 -20 0 20 40 60 80 100120140 output voltage (v) temperature (c) battery voltage vs. temperature 0 100 200 300 400 500 600 700 800 -40 0 40 80 120 short circuit current (ma) temperature (c) short circuit current vs. temperature
september 2001 5 MIC79050 MIC79050 micrel -0.75 -0.25 0.25 0.75 0 200 400 600 800 drift from nominal vout (%) time (hrs) typical voltage drift limits vs. time upper lower 0 5 10 15 20 012345 reverse leakage current ( a) output voltage (v) reverse leakage current vs. output voltage 0 5 10 15 20 -5 5 1525354555 reverse leakage current ( a) temperature (c) reverse leakage current vs. output voltage 3.0v 3.6v 4.2v v in +v en floating 0 5 10 15 20 -5 5 1525354555 reverse leakage current (ua) temperature (c) reverse leakage current vs. temperature 3.0v 3.6v 4.2v v in +v en grounded
MIC79050 micrel MIC79050 6 september 2001 block diagrams current limit thermal shutdown in gnd bandgap ref. v bat v in MIC79050-x.xbs 3-pin version functional description the MIC79050 is a high-accuracy, linear battery charging circuit designed for the simplest implementation of a single lithium-ion (li-ion) battery charger. the part can operate from a regulated or unregulated power source, making it ideal for various applications. the MIC79050 can take an unregulated voltage source and provide an extremely accurate termina- tion voltage. the output voltage varies only 0.75% from nominal over the standard temperature range for li-ion battery charging ( C 5 c to 60 c). with a minimum of external components, an accurate constant current charger can be designed to provide constant current, constant voltage charg- ing for li-ion cells. input voltage the MIC79050 can operate with an input voltage up to 16v (20v absolute maximum), ideal for applications where the input voltage can float high, such as an unregulated wall adapter that obeys a load-line. higher voltages can be sustained without any performance degradation to the output voltage. the line regulation of the device is typically 0.009%/v; that is, a 10v change on the input voltage corresponds to a 0.09% change in output voltage. enable the MIC79050 has an enable pin that allows the charger to be disabled when the battery is fully charged and the current drawn by the battery has approached a minimum and/or the maximum charging time has timed out. when disabled, the regulator output sinks a minimum of current with the battery voltage applied directly onto the output. this current is typically 12 a or less. feedback the feedback pin allows for external manipulation of the control loop. this node is connected to an external resistive divider network, which is connected to the internal error amplifier. this amplifier compares the voltage at the feed- back pin to an internal voltage reference. the loop then corrects for changes in load current or input voltage by monitoring the output voltage and linearly controlling the drive to the large, pnp pass element. by externally control- ling the voltage at the feedback pin the output can be disabled or forced to the input voltage. pulling and holding the feed- back pin low forces the output low. holding the feedback pin high forces the pass element into saturation, where the output will be the input minus the saturation (dropout) voltage. battery output the bat pin is the output of the MIC79050 and connects directly to the cell to provide charging current and voltage. when the input is left floating or grounded, the bat pin limits reverse current to <12 a to minimize battery drain. in en fb gnd v ref bandgap ref. current limit thermal shutdown v bat v in MIC79050-x.xbmm/m 5-pin version
september 2001 7 MIC79050 MIC79050 micrel applications information simple lithium-ion battery charger. figure 1a shows a simple, complete lithium-ion battery charger. the charging circuit comprises of a cheap wall adapter, with a load-line characteristic. this characteristic is always present with cheap adapters due to the internal impedance of the transformer windings. the load-line of the unregulated output should be < 4.4v to 4.6v at somewhere between 0.5c to 1c of the battery under charge. this 4.4 to 4.6v value is an approximate number based on the head- room needed above 4.2v for the MIC79050 to operate lm4041 cim3-1.2 in bat fb gnd en MIC79050-4.2bm v ref = 1.225v impedence ac load-line wall adapter 10k 4.7 f 1k end of charge r2 r1 mic6270 vv r1 r2 eoc ref =+ ? ? ? ? ? ? 1 v s figure 1a. load-line charger with end-of-charge termination circuit. 0 2 4 6 8 0 0.2 0.4 0.6 0.8 source voltage (v) source current (a) load-line source characteristics figure 1b. load-line characteristics of ac wall adapter correctly e.g. for a 500mahr battery, the output of the semi- regulated supply should be between 225ma to 500ma ( 0.5c to 1c ). if it is below 225ma no damage will occur but the battery will take longer to charge. figure 1b shows a typical wall adapter characteristic with an output current of 350ma at 4.5v. this natural impedance of the wall adapter will limit the max current into the battery, so no external circuitry is needed to accomplish this. if extra impedance is needed to achieve the desired loadline, extra resistance can easily be added in series with the MIC79050 in pin.
MIC79050 micrel MIC79050 8 september 2001 v eoc open circuit charger voltage battery current (i b ) battery voltage (v b ) unregulated input voltage(v b ) 79050 programmed output voltage (no load voltage) end of charge (v eoc ) state a initial charge state b voltage charge state c end of charge state d charge top state c figure 1c. charging cycles in bat fb gnd en MIC79050-4.2bm lm4041 cim3-1.2 5v 5%@ 400ma 5% 4.7 f 8.06m 47k 47k 1k 0.050 ? q1 10k r2 mic6270 mic7300 10k 1k figure 2. protected constant-current charger the charging cycle (see figure 1c.) 1. state a: initial charge. here the battery s charging current is limited by the wall adapter s natural imped- ance. the battery voltage approaches 4.2v. 2. state b: constant voltage charge. here the battery voltage is at 4.2v 0.75% and the current is decaying in the battery. when the battery has reached approxi- mately 1/10th of its 1c rating, the battery is considered to have reached full charge. because of the natural characteristic impedance of the cheap wall adapters, as the battery voltage decreases so the input voltage increases. the mic6270 and the lm4041 are config- ured as a simple voltage monitor, indicating when the input voltage has reached such a level so the current in the battery is low, indicating full charge. 3. state c: end of charge cycle. when the input voltage, v s reaches v eoc, an end of charge signal is indicated. 4. state d: top up charge. as soon as enough current is drawn out of the input source, which pulls the voltage lower than the v eoc , the end of charge flag will be pulled low and charging will initiate. variations on this scheme can be implemented, such as the circuit shown in figure 2. for those designs that have a zero impedance source , see figure 3.
september 2001 9 MIC79050 MIC79050 micrel protected constant-current charger another form of charging is using a simple wall adapter that offers a fixed voltage at a controlled, maximum current rating. the output of a typical charger will source a fixed voltage at a maximum current unless that maximum current is ex- ceeded. in the event that the maximum current is exceeded, the voltage will drop while maintaining that maximum current. using an MIC79050 after this type of charger is ideal for lithium-ion battery charging. the only obstacle is end of charger termination. using a simple differential amplifier and a similar comparator and reference circuit, similar to figure 1, completes a single cell lithium-ion battery charger solution. figure 2 shows this solution in completion. the source is a fixed 5v source capable of a maximum of 400ma of current. when the battery demands full current (fast charge), the source will provide only 400ma and the input will be pulled down. the output of the MIC79050 will follow the input minus a small voltage drop. when the battery approaches full charge, the current will taper off. as the current across r s approaches 50ma, the output of the differential amplifier (mic7300) will approach 1.225v, the reference voltage set by the lm4041. when it drops below the reference voltage, the output of the comparator (mic6270) will allow the base of q1 to be pulled high through r2. zero-output impedance source charging input voltage sources that have very low output impedances can be a challenge due to the nature of the source. using the circuit in figure 3 will provide a constant-current and constant voltage charging algorithm with the appropriate end-of-charge termination. the main loop consists of an op-amp controlling the feedback pin through the schottky diode, d1. the charge current through r s is held constant by the op-amp circuit until the output draws less than the set charge-current. at this point, the output goes constant-voltage. when the current through r s gets to less than 50ma, the difference amp output becomes less than the reference voltage of the mic834 and the output pulls low. this sets the output of the MIC79050 less than nominal, stopping current flow and terminating charge. lithium-ion battery charging single lithium-ion cells are typically charged by providing a constant current and terminating the charge with constant voltage. the charge cycle must be initiated by ensuring that the battery is not in deep discharge. if the battery voltage is below 2.5v, it is commonly recommended to trickle charge the battery with 5ma to 10ma of current until the output is above 2.5v. at this point the battery can be charged with constant current until it reaches its top off voltage (4.2v for a typical single lithium-ion cell) or a time out occurs. for the constant-voltage portion of the charging circuit, an extremely accurate termination voltage is highly recom- mended. the higher the accuracy of the termination circuit, the more energy the battery will store. since lithium-ion cells do not exhibit a memory effect, less accurate termination does not harm the cell but simply stores less usable energy in the battery. the charge cycle is completed by disabling the charge circuit after the termination current drops below a minimum recommended level, typically 50ma or less, de- pending on the manufacturer s recommendation, or if the circuit times out. time out the time-out aspect of lithium-ion battery charging can be added as a safety feature of the circuit. often times this function is incorporated in the software portion of an applica- tion using a real-time clock to count out the maximum amount of time allowed in the charging cycle. when the maximum recommended charge time for the specific cell has been exceeded, the enable pin of the MIC79050 can be pulled low, and the output will float to the battery voltage, no longer providing current to the output. as a second option, the feedback pin of the MIC79050 can be modulated as in figure 4. figure 4. shows a simple circuit where the mic834, an integrated comparator and reference, monitors the battery voltage and disables the MIC79050 output after the voltage on the battery exceeds a set vaue. when the voltage decays below this set threshold, the mic834 drives q1 low allowing the MIC79050 to turn on MIC79050-4.2bm mic834 sd101 1 ? 2 mic7122 1 ? 2 mic7122 in bat fb gnd en 8.06m 4.7 f r 2 =124k r 3 =1k r 4 =124k 0.01 f vdd out gnd inp r 1 =1k d1 221k 16.2k 16k 10k 5v r s =0.200 ? i 80mv r cc s = i 1.240v r rr eoc 1 2 s = figure 3.
MIC79050 micrel MIC79050 10 september 2001 again and provide current to the battery until it is fully charged. this form of pulse charging is an acceptable way of maintain- ing the full charge on a cell until it is ready to be used. li-ion cell in bat fb gnd en MIC79050-4.2bmm vdd out gnd inp r1 100k 4.7 f r2 mic834 vin gnd v ref =1.240v vv1 r1 r2 bat(low) ref = =+ + ? ? ? ? ? ? ? ? ? ? ? ? figure 4. pulse charging for top-off voltage charging rate lithium-ion cells are typically charged at rates that are fractional multiples of their rated capacity. the maximum varies between 1c C 1.3c (1 to 1.3 the capacity of the cell). the MIC79050 can be used for any cell size. the size of the cell and the current capability of the input source will deter- mine the overall circuit charge rate. for example, a 1200mah battery charged with the MIC79050 can be charged at a maximum of 0.5c. there is no adverse effects to charging at lower charge rates; that charging will just take longer. charg- ing at rates greater than 1c are not recommended, or do they decrease the charge time linearly. the MIC79050 is capable of providing 500ma of current at its nominal rated output voltage of 4.2v. if the input is brought below the nominal output voltage, the output will follow the input, less the saturation voltage drop of the pass element. if the cell draws more than the maximum output current of the device, the output will be pulled low, charging the cell at 600ma to 700ma current. if the input is a fixed source with a low output impedance, this could lead to a large drop across the MIC79050 and excess heating. by driving the feedback pin with an external pwm-circuit, the MIC79050 can be used to pulse charge the battery to reduce power dissipation and bring the device and the entire unit down to a lower operating temperature. figure 5 shows a typical configuration for a pwm-based pulse-charging topology. two circuits are shown in figure 5: circuit a uses an external pwm signal to control the charger, while circuit b uses the mic4417 as a low duty- cycle oscillator to drive the base of q1. (consult the battery manufacturer for optimal pulse-charging techniques). li-ion cell 4.7 f in bat fb gnd en MIC79050-4.2bmm vin external pwm figure 5a. li-ion cell 4.7 f 200pf 1k ? 40k ? in bat fb gnd en MIC79050-4.2bmm vin=4.5v to 16v mic4417 figure 5b. pwm based pulse-charging applications figure 6 shows another application to increase the output current capability of the MIC79050. by adding an external pnp power transistor, higher output current can be obtained while maintaining the same accuracy. the internal pnp now becomes the driver of a darlington array of pnp transistors, obtaining much higher output currents for applications where the charge rate of the battery is much higher. in bat 4.7 f fb gnd en MIC79050-4.2bmm figure 6. high current charging regulated input source charging when providing a constant-current, constant-voltage, charger solution from a well-regulated adapter circuit, the MIC79050 can be used with external components to provide a constant voltage, constant-current charger solution. figure 7 shows a configuration for a high-side battery charger circuit that monitors input current to the battery and allows a constant current charge that is accurately terminated with the MIC79050. the circuit works best with smaller batteries, charging at c rates in the 300ma to 500ma range. the mic7300 op-amp compares the drop across a current sense resistor and compares that to a high-side voltage reference, the lm4041, pulling the feedback pin low when the circuit is in the constant-current mode. when the current through the resistor drops and the battery gets closer to full charge, the output of the op-amp rises and allows the internal feedback network of the regulator take over, regulating the output to 4.2v. in bat fb gnd en MIC79050-4.2bmm sd101 4.7 f 0.01 f mic7300 lm4041cim3-1.2 16.2k 221k 10k r s i mv r cc s = = 80 figure 7. constant current,
september 2001 11 MIC79050 MIC79050 micrel constant voltage charger simple charging the MIC79050 is available in a three-terminal package, allowing for extremely simple battery charging. when used with a current-limited, low-power input supply, the MIC79050- 4.2bs completes a very simple, low-charge-rate, battery- charger circuit. it provides the accuracy required for termina- tion, while a current-limited input supply offers the constant- current portion of the algorithm. thermal considerations the MIC79050 is offered in three packages for the various applications. the sot-223 is most thermally efficient of the three packages, with the power sop-8 and the power msop-8 following suit. power sop-8 thermal characteristics one of the secrets of the MIC79050 s performance is its power so-8 package featuring half the thermal resistance of a standard so-8 package. lower thermal resistance means more output current or higher input voltage for a given package size. lower thermal resistance is achieved by joining the four ground leads with the die attach paddle to create a single- piece electrical and thermal conductor. this concept has been used by mosfet manufacturers for years, proving very reliable and cost effective for the user. thermal resistance consists of two main elements, jc , or thermal resistance junction to case and ca , thermal resis- tance case to ambient (figure 8). jc is the resistance from the die to the leads of the package. ca is the resistance from the leads to the ambient air and it includes cs , thermal resistance case to sink, and sa , thermal resistance sink to ambient. using the power sop-8 reduces the jc dramati- cally and allows the user to reduce ca . the total thermal resistance, ja , junction to ambient thermal resistance, is the limiting factor in calculating the maximum power dissipation capability of the device. typically, the power sop-8 has a jc of 20 c/w, this is significantly lower than the standard sop- 8 which is typically 75 c/w. ca is reduced because pins 5- 8 can now be soldered directly to a ground plane, which significantly reduces the case to sink thermal resistance and sink to ambient thermal resistance. ja jc ca printed circuit board ground plane heat sink are a sop-8 ambient figure 8. thermal resistance the MIC79050 is rated to a maximum junction temperature of 125 c. it is important not to exceed this maximum junction temperature during operation of the device. to prevent this maximum junction temperature from being exceeded, the appropriate ground plane heat sink must be used. figure 9 shows curves of copper area versus power dissipa- tion, each trace corresponding to different temperature rises above ambient. from these curves, the minimum area of copper necessary for the part to operate safely can be determined. the maximum allowable temperature rise must be calculated to determine operation along which curve. 0 100 200 300 400 500 600 700 800 900 0 0.25 0.50 0.75 1.00 1.25 1.50 copper area (mm 2 ) power dissipation (w) 40 c 50 c 55 c 65 c 75 c 85 c 100 c ? t ja = figure 9. copper area vs. power-sop power dissipation (? t ja ) where ? t = t j(max) C t a(max) t j(max) = 125 c t a(max) = maximum ambient operating temperature for example, the maximum ambient temperature is 40 c, the ? t is determined as follows: ? t = +125 c C 40 c ? t = +85 c using figure 9, the minimum amount of required copper can be determined based on the required power dissipation. power dissipation in a linear regulator is calculated as fol- lows: p d = (vin-vout)*iout + vin*ignd for example, using the charging circuit in figure 7, assume the input is a fixed 5v and the output is pulled down to 4.2v at a charge current of 500ma. the power dissipation in the MIC79050 is calculated as follows: p d = (5v C 4.2v)*0.5a + 5v*0.012a p d = 0.460w from figure 9, the minimum amount of copper required to operate this application at a ? t of 85c is less than 50mm 2 . quick method determine the power dissipation requirements for the design along with the maximum ambient temperature at which the device will be operated. refer to figure 10 , which shows safe operating curves for 3 different ambient temperatures: +25 c, +50 c and +85 c. from these curves, the minimum amount of copper can be determined by knowing the maximum power
MIC79050 micrel MIC79050 12 september 2001 dissipation required. if the maximum ambient temperature is +40 c and the power dissipation is as above, 0.46w, the curve in figure 10 shows that the required area of copper is 50mm 2 . the ja of this package is ideally 63 c/w, but it will vary depending upon the availability of copper ground plane to which it is attached. 0 100 200 300 400 500 600 700 800 900 0 0.25 0.50 0.75 1.00 1.25 1.50 copper area (mm 2 ) power dissipation (w) 85 c 50 c 25 c t j = 125 c figure 10. copper area vs. power-sop power dissipation (t a ) power msop-8 thermal characteristics the power-mso-8 package follows the same idea as the power-so-8 package, using four ground leads with the die attach paddle to create a single-piece electrical and thermal conductor, reducing thermal resistance and increasing power dissipation capability. the same method of determining the heat sink area used for the power-sop-8 can be applied directly to the power- msop-8. the same two curves showing power dissipation versus copper area are reproduced for the power-msop-8 and they can be applied identically. quick method determine the power dissipation requirements for the design along with the maximum ambient temperature at which the device will be operated. refer to figure 12, which shows safe operating curves for 3 different ambient temperatures, +25 c, +50 c and +85 c. from these curves, the minimum amount of copper can be determined by knowing the maximum power dissipation required. if the maximum ambient temperature is +25 c and the power dissipation is 1w, the curve in figure 12v shows that the required area of copper is 500mm 2 ,when using the power msop-8 0 100 200 300 400 500 600 700 800 900 0 0.25 0.50 0.75 1.00 1.25 1.50 copper area (mm 2 ) power dissipation (w) 40 c 50 c 55 c 65 c 75 c 85 c 1 00 c figure 11. copper area vs. power-msop power dissipation ( ? t ja ) 0 100 200 300 400 500 600 700 800 900 0 0.25 0.50 0.75 1.00 1.25 1.50 copper area (mm 2 ) power dissipation (w) 85 c 50 c 25 c t j = 125 c figure 12. copper area vs. power-msop power dissipation (t a )
september 2001 13 MIC79050 MIC79050 micrel package information 16 10 0.84 (0.033) 0.64 (0.025) 1.04 (0.041) 0.85 (0.033) 2.41 (0.095) 2.21 (0.087) 4.7 (0.185) 4.5 (0.177) 6.70 (0.264) 6.30 (0.248) 7.49 (0.295) 6.71 (0.264) 3.71 (0.146) 3.30 (0.130) 3.15 (0.124) 2.90 (0.114) 10 max 0.10 (0.004) 0.02 (0.0008) 0.38 (0.015) 0.25 (0.010) c l dimensions: mm (inch) c l 1.70 (0.067) 1.52 (0.060) 0.91 (0.036) min sot-223 (s) 45 0 C 8 0.244 (6.20) 0.228 (5.79) 0.197 (5.0) 0.189 (4.8) seating plane 0.026 (0.65) max ) 0.010 (0.25) 0.007 (0.18) 0.064 (1.63) 0.045 (1.14) 0.0098 (0.249) 0.0040 (0.102) 0.020 (0.51) 0.013 (0.33) 0.157 (3.99) 0.150 (3.81) 0.050 (1.27) typ pin 1 dimensions: inches (mm) 0.050 (1.27) 0.016 (0.40) 8-pin sop (m)
MIC79050 micrel MIC79050 14 september 2001 0.008 (0.20) 0.004 (0.10) 0.039 (0.99) 0.035 (0.89) 0.021 (0.53) 0.012 (0.03) r 0.0256 (0.65) typ 0.012 (0.30) r 5 max 0 min 0.122 (3.10) 0.112 (2.84) 0.120 (3.05) 0.116 (2.95) 0.012 (0.03) 0.007 (0.18) 0.005 (0.13) 0.043 (1.09) 0.038 (0.97) 0.036 (0.90) 0.032 (0.81) dimensions: inch (mm) 0.199 (5.05) 0.187 (4.74) 8-pin msop (mm)
september 2001 15 MIC79050 MIC79050 micrel
MIC79050 micrel MIC79050 16 september 2001 micrel inc. 1849 fortune drive san jose, ca 95131 usa tel + 1 (408) 944-0800 fax + 1 (408) 944-0970 web http://www.micrel.com this information is believed to be accurate and reliable, however no responsibility is assumed by micrel for its use nor for an y infringement of patents or other rights of third parties resulting from its use. no license is granted by implication or otherwise under any patent or pat ent right of micrel inc. ? 2001 micrel incorporated

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