general description the max1735 negative-output, low-dropout linear regu-lator operates from a -2.5v to -6.5v input and delivers a guaranteed 200ma with a low 80mv dropout. the high- accuracy (?%) output voltage is preset or can be adjusted from -1.25v to -5.5v with an external resistive voltage-divider. an internal n-channel mosfet allows for a low 85? quiescent current virtually independent of the load, making this device ideal for battery-powered portable equipment, such as pdas, mobile phones, cordless phones, and wireless data modems. the device is available in several preset output voltage versions: -5.0v, -3.0v, and -2.5v. all versions offer a 1na low-power shutdown mode, short-circuit protec- tion, and thermal overload protection. the device is offered in a tiny 5-pin sot23 package. applications disk drivesmodems instrumentation amplifiers notebook computers mobile and cordless telephones pcmcia cards gaasfet bias mobile wireless data modems pdas and palmtop computers features ? guaranteed 200ma output current ? low 80mv dropout voltage at 200ma ? low 85a quiescent supply current ? low 1na current shutdown mode ? stable with 1f c out ? psrr >60db at 100hz ? thermal overload protection ? short-circuit protection ? -5.0v, -3.0v, or -2.5v output voltageor adjustable (-1.25v to -5.5v) ? tiny sot23-5 package max1735 200ma, negative-output, low-dropout linear regulator in sot23 ________________________________________________________________ maxim integrated products 1 in set shdn 15 out gnd max1735 sot23-5 top view 234 max1735 shdn -6.5v to -2.5v input -5v, -3v, or -2.5v output up to 200ma c in c out out in set gnd gnd on off on typical operating circuit 19-1783; rev 1; 11/03 pin configuration ordering information part temp range pin-package max1735euk50-t -40? to +85? 5 sot23-5 MAX1735EUK30-t -40? to +85? 5 sot23-5 max1735euk25-t -40? to +85? 5 sot23-5 output-voltage selector guide part preset output voltage sot top mark max1735euk50-t -5.0v or adj adoz MAX1735EUK30-t -3.0v or adj adoy max1735euk25-t -2.5v or adj adox for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. downloaded from: http:///
max1735 200ma, negative-output, low-dropout linear regulator in sot23 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics(circuit of figure 2, v in = v out - 1v, v shdn = v in , t a = -40 c to +85 c, unless otherwise noted. typical values are at t a = +25 c.) (note 1) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. in, set to gnd .................................................... -7.0v to +0.3v shdn to gnd ............................................ (v in - 0.3)v to +7.0v out to gnd ...............................................(v in - 0.3)v to +0.3v output short-circuit duration ........................................indefinite continuous power dissipation (t a = +70 c) 5-pin sot23 (derate 7.1mw/ c above +70 c)........... 571mw operating temperature range ...........................-40 c to +85 c junction temperature ......................................................+150 c storage temperature range ............................ -65 c to +150 c lead temperature (soldering, 10s) ................................ +300 c parameter symbol conditions min typ max units input voltage v in -6.5 -2.5 v t a = +25 c, i out = -100? -1 +1 i out = -100?, t a = 0 c to +85 c- 2+ 2 output voltage accuracy i load = -100? to -200ma -3 +2 % circuit of figure 3, t a = +25 c, i out = -100? -1.2625 -1.25 -1.2375 circuit of figure 3, i out = -100?, t a = 0 c to +85 c -1.275 -1.225 set regulation set point circuit of figure 3, i load = -100? to -200ma -1.275 -1.2125 v maximum output current i out -200 ma current limit i lim v out = 0 -1020 -515 -250 ma i out = -100? -180 -85 ground-pin current i q i out = -200ma -125 ? i out = -100ma 40 dropout voltage (note 2) i out = -200ma 80 240 mv line regulation circuit of figure 3,v in from -6.5v to -2.5v, v out = -1.25v -0.15 0 +0.15 %/v load regulation i out from 0ma to -200ma 0.004 %/ma output voltage noise 10hz to 1mhz, c out = 1? 160 ? rms power-supply rejection ratio psrr f = 100hz 60 db t a = +25 c -1 -0.001 shutdown supply current v shdn = 0 t a = +85 c- 1 ? positive voltage at shdn +1.6 shdn input high threshold (note 3) negative voltage at shdn -1.6 v positive voltage at shdn +0.4 shdn input low threshold (note 3) negative voltage at shdn -0.4 v set input bias current i set v set = -1.25v, t a = +25 c -100 -15 na v shdn = +6.5v 3.5 shdn input bias current t a = +25 c v shdn = 0, -6.5v -0.5 +0.5 ? thermal shutdown junctiontemperature hysteresis = 15 c (typ) 160 c note 1: limits are 100% production tested at t a = +25 c. limits over operating temperature range are guaranteed by design. note 2: the dropout voltage is defined as v out - v in , when v out is 100mv above the nominal value of v out . note 3: the shdn logic input can be driven by either a positive voltage or a negative voltage. | v shdn | < 0.4v puts the device in shutdown, while | v shdn | > 1.6v enables the device. downloaded from: http:///
max1735 200ma, negative-output, low-dropout linear regulator in sot23 _______________________________________________________________________________________ 3 0 4020 100 8060 160140 120 180 0- 2 - 3 -1 -4 -5 -6 supply current vs. supply voltage max1735 toc01 supply voltage (v) supply current ( a) i load = 200ma -7 70 9080 110100 130120 140 08 0 40 120 160 20 100 60 140 180 200 supply current vs. load current max1735 toc02 load current (ma) supply current ( a) 0 4020 100 8060 160140 120 180 -40 10 - 1 5 3 56 08 5 supply current vs. temperature max1735 toc03 temperature ( c) supply current ( a) no load i load = 200ma 0 20 6040 80 100 05 0 7 5 25 100 125 150 175 200 dropout voltage vs. load current max1735 toc04 load current (ma) dropout voltage (mv) t a = +25 c t a = +85 c t a = -40 c v out = -2.9v -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0 05 0 25 75 100 125 150 175 200 output voltage change vs. load current max1735 toc05 load current (ma) output voltage change (%) v out = -3v t a = -40 c t a = +25 c t a = +85 c -1.00 -0.75 -0.50 -0.25 0 0.25 0.50 0.75 1.00 -40 -15 10 35 60 85 output voltage change vs. temperature max1735 toc06 temperature ( c) output voltage change (%) i load = 200ma no load typical operating characteristics (circuit of figure 2, v in = -4.0v, v out = -3.0v, t a = +25 c, unless otherwise specified.) downloaded from: http:///
max1735 200ma, negative-output, low-dropout linear regulator in sot23 4 _______________________________________________________________________________________ 0.001 0.01 0.1 1 10 100 0 80 100 40 60 20 120 140 160 180 200 region of stable esr vs. load current max1735 toc10 load current (ma) region of stable esr c out ( ) c out = 1 f region of stability line-transient response max1735 toc11 time (100 s/div) v out 50mv/divv in 1v/div load-transient response (normal operation) max1735 toc12 time (100 s/div) i load step 0 to 50mav out 10mv/div load-transient response (near dropout) max1735 toc13 time (100 s/div) i load step 0 to 50mav out 10mv/div typical operating characteristics (continued) (circuit of figure 2, v in = -4.0v, v out = -3.0v, t a = +25 c, unless otherwise specified.) 0 2010 4030 6050 70 1 100 10 1k 10k 100k power-supply rejection ratio vs. frequency max1735 toc07 frequency (hz) psrr (db) 1m c out = 10 f c out = 1.0 f 10 0.01 10 1k 100k output noise density vs. frequency max1735 toc08 frequency (hz) output noise ( v rms / hz) 0.1 1 output noise (10hz to 1mhz) max1735 toc09 time (1ms/div) 500 v/div c out = 1 f i load = 50ma downloaded from: http:///
max1735 200ma, negative-output, low-dropout linear regulator in sot23 _______________________________________________________________________________________ 5 shutdown response (driven from a positive voltage) max1735 toc14a time (200 s/div) v shdn 2v/div0 v out 2v/div 0 shutdown response (driven by a negative voltage) max1735 toc14b time (200 s/div) v shdn 2v/divv out 2v/div 0 0 -0.5 0 0.5 1.0 1.5 2.0 -6.5 -2.0 -0.5 -5.0 -3.5 1.0 2.5 4.0 5.5 shutdown-pin bias current vs. shutdown-pin voltage max1735 toc15 shutdown-pin voltage (v) shutdown-pin bias current ( a) invalid logic voltage invalid logic voltage pin description pin name function 1 gnd ground 2i n regulator input. supply voltage can range from -2.5v to -6.5v. bypass with a 1 f capacitor to gnd (see capacitor selection and regulator stability ). this pin also functions as a heatsink. solder to a large pc board pad or directly to the pc board power plane to maximize thermal dissipation. 3 shdn shutdown input. drive shdn to gnd to turn the regulator off, reducing the input current to less than 1na. drive shdn above +1.6v or below -1.6v to enable the regulator. connect shdn to in for always-on operation. 4 set dual mode regulator feedback input. connect set to gnd for the preset output voltage. use a resistive voltage-divider from out to set to set the output voltage between -1.25v and -5.5v. regulation setpoint is -1.25v. 5 out regulator output. out supplies up to 200ma in regulation. bypass to gnd with a 1 f ceramic capacitor. typical operating characteristics (continued) (circuit of figure 2, v in = -4.0v, v out = -3.0v, t a = +25 c, unless otherwise specified.) dual mode is a trademark of maxim integrated products, inc. downloaded from: http:///
max1735 200ma, negative-output, low-dropout linear regulator in sot23 detailed description the max1735 is a low-dropout negative linear voltageregulator. it features dual mode operation, allowing a fixed -5.0v, -3.0v, or -2.5v output voltage or an adjustable output from -1.25v to -5.5v. the regulator is guaranteed to supply 200ma of output current. it fea- tures 60db power-supply rejection for noise-sensitive applications and a low 85? operating current that opti- mizes it for battery-operated devices. as figure 1 illustrates, the device consists of an internal -1.25v reference, an error amplifier, an n-channel mosfet, an internal precision-trimmed feedback volt- age-divider, and a dual mode comparator. the -1.25v reference is connected to the inverting input of the error amplifier. the error amplifier compares the reference voltage with the selected feedback voltage and amplifies the difference. the error amplifier drives the mosfet to control the output voltage. the feedback voltage for regulation is generated by either an internal or external resistive voltage-divider connected from out to set. the internal dual mode comparator selects the feedback path based on v set . connect set to gnd to use the internal feedback path,setting the output voltage to the preset value. if an external voltage-divider is used, see output voltage selection . internal n-channel mosfet the max1735 features an n-channel mosfet passtransistor. unlike similar designs using npn bipolar pass transistors, n-channel mosfets require extreme- ly low drive currents, reducing overall quiescent cur- rent. also, npn-based regulators consume still more base current in dropout conditions when the pass tran- sistor saturates. the max1735 does not suffer from these problems, consuming only 125? total current at full load and in dropout. output voltage selection the max1735 features dual mode operation, allowing fora preset or adjustable output voltage. in preset voltage mode, the output of the max1735 is set to -5.0v, -3.0v, or -2.5v (see ordering information ). select this mode by connecting set to gnd (figure 2). on off on thermal sensor nmos pass transistor out c out r1 r2 set gnd dual mode comparator erroramplifier v ref -1.25v -270mv shutdown logic shdn c in in max1735 gnd figure 1. functional diagram 6 _______________________________________________________________________________________ downloaded from: http:///
max1735 200ma, negative-output, low-dropout linear regulator in sot23 _______________________________________________________________________________________ 7 in adjustable mode, an output voltage between -5.5v and-1.25v is selected using two external resistors connected as a voltage-divider from out to set (figure 3). the out- put voltage is determined by the following equation: where v set = v reference = -1.25v when in regulation. since the input bias current at set is <100na, uselarge resistance values for r1 and r2 to minimize power consumption in the feedback network. a typical value of 100k for r2 is acceptable for most applica- tions. higher values consume less current at theexpense of output voltage accuracy. the above equa- tion solved for r1 is: for preset output voltage mode, connect set directly to gnd. shutdown in shutdown, the n-channel mosfet, control circuitry,reference, and all internal circuits are turned off, reduc- ing supply current to typically 1na. shdn can be dri- ven by either a positive or negative voltage. driveshdn above +1.6v or below -1.6v to turn the regulator on. to turn the regulator off, drive shdn to gnd. for always-on operation, connect shdn to in. by including a positive threshold at shdn , it can be driven by a standard 5v ttl level without needing level-shifting cir-cuitry. current limiting the max1735 features a current limit that protects theregulator. short-circuit output current is typically 515ma. the output will withstand a short to ground indefinitely; however, if the increased power dissipation heats the die to +160 c, the thermal overload protec- tion will shut off the regulator, preventing damage to theic. thermal overload protection the thermal overload protection circuit protects the reg-ulator against overheating due to prolonged overload conditions. when the die temperature exceeds +160 c, an on-chip thermal sensor disables the pass transistor,allowing the ic to cool. the thermal sensor reenables the pass mosfet once the die temperature drops 15 c. a continuous short-circuit fault condition results in a cyclical enabling and disabling of the output.thermal overload protection is designed to safeguard the max1735 in the event of overload fault conditions. for normal operation, do not exceed the absolute maxi- mum junction temperature rating of +150 c. junction temperature is greater than ambient by an amountdepending on package heat dissipation and the ther- mal resistance from the junction to ambient ( ja ): t junction = t ambient + ( ja )(p dissipation ) where ja for the 5-pin sot23 is about 0.140 c/mw. rr v v out set 12 1 = ?? ? ?? ? ? ?? ?? ?? ?? vv r r out set =+ ?? ? ?? ? ?? ? ?? ? 1 1 2 max1735 shdn input c in 1 f ceramic adjustableoutput c out 1 f ceramic out in set gnd on off on -6.5v to -2.5v gnd -5.5v to -1.25v r2 r1 v out = v set ( 1 + r1 ) r2 figure 3. typical application circuit with adjustable output voltage max1735 shdn input c in 1 f ceramic fixedoutput c out 1 f ceramic out in set gnd on off on -6.5v to -2.5v gnd -5.0v,-3.0v, or -2.5v figure 2. typical application circuit with preset output voltage downloaded from: http:///
max1735 200ma, negative-output, low-dropout linear regulator in sot23 8 _______________________________________________________________________________________ operating region and power dissipation maximum power dissipation of the max1735 dependson the thermal resistance of the case and the circuit board, the temperature difference between the die junction and ambient air, and the rate of air flow (see also thermal overload protection ). the maximum power that can be dissipated by the device is:where the numerator expresses the temperature differ- ence between the maximum allowed die junction (+150 c) and the surrounding air, jc (junction to case) is the thermal resistance of the package, and ca (case to ambient) is the thermal resistance from the packagethrough the pc board, traces, and other material to the surrounding air. the former is a characteristic solely of the device in its package, and the latter is completely defined by pc board layout and airflow. it is important to note that the ability to dissipate power is as much a func- tion of the pc board layout and air flow as the packaged part itself. hence, a manufacturer can reliably provide a value for jc , but not accurately provide a value for the total thermal resistance ja . ja is the sum of jc and ca , and the manufacturer can seldom reliably predict the thermal characteristics of the application circuit.figure 4 shows the estimated allowable power dissipa- tion for a max1735 mounted on a typical pc board at ambient temperatures of +50 c, +70 c, and +85 c. figure 4 shows the maximum continuous output currentfor a particular input-to-output voltage differen tial, for selected ambient temperatures. the working principle isthat the sot23-5 package is small enough that in a typi- cal application circuit at room temperature, the package cannot dissipate enough power to allow -6.5v to be reg- ulated to -1.25v at -200ma output (more than 1200mw). as ambient temperature falls, the available power dissi- pation increases to allow for a greater operating region. the equation for the family of curves follows: where | i out | is in ma, | v out - v in | in v, p max (571mw) is the absolute maximum rated power dissipation at+70 c for the sot23-5, and ja (0.140 c/mw) is the approximate junction-to-ambient thermal resistance ofthe sot23-5 in a typical application. a key to reducing ca , thereby increasing thermal con- ductivity to the pc board, is to provide large pc board pads and traces for in. __________applications information capacitor selection and regulator stability capacitors are required at the input and output of themax1735. connect a 1? or greater capacitor between in and gnd. this input capacitor serves only to lower the source impedance of the input supply in transient conditions; a smaller value can be used when the regu- lator is powered from a low-impedance source, such as another regulated supply or low-impedance batteries. for output voltages between -2.5v and -5.5v, connect a 1? or greater capacitor between out and gnd. for voltages between -1.25v and -2.5v, use a 2.2? or greater output capacitor. the maximum value of the output capacitor to guarantee stability is 10?. the output capacitor s value and equivalent series resistance (esr) affect stability and output noise. toensure stability and optimum transient response, output capacitor esr should be 0.1 or less for output volt- ages from -1.25v to -2.45v and 0.2 or less for output voltages between -2.5v and -5.5v. inexpensive sur-face-mount ceramic capacitors typically have very-low esr and are commonly available in values up to 10?. other low-esr capacitors, such as surface-mount tan- talum, may also be used. do not use low-cost alu- minum electrolytic capacitors due to their large size and relatively high esr. lastly, make sure the input and output capacitors are as close to the ic as possible to minimize the impact of pc board trace impedance. || || i p t vv out max a ja out in = ? ? ? 70 p tttt max jmax a jc ca jmax a ja = ? + = ? ? 250 150 100 50 0 03 12 456 maximum output current vs. input-output voltage differential input-output voltage differential (v) maximum output current (ma) device in dropout max supply voltage ?min output voltage at maximumjunction temp (t j = +150 c) 200 maximum continuous current t a = +50 c t a = +70 c t a = +85 c figure 4. output current and in-out voltage differential operating region bounded by available power dissipation at selected ambient temperatures downloaded from: http:///
noise, psrr, and transient response max1735 output noise is typically 160? rms . this is suitably low for most applications. see the outputnoise vs. frequency plot in the typical operating characteristics . the max1735 is optimized for battery-powered equip-ment, with low dropout voltage and low quiescent cur- rent. it maintains good transient response, ac rejection, and noise characteristics even near dropout. see power-supply rejection ratio vs. frequency in the typical operating characteristics . when operating from very noisy sources, supply noise rejection andtransient response can be improved by increasing the input and output capacitance, and by employing pas- sive postfiltering. dropout voltage a regulator s minimum input-to-output voltage differen- tial dropout voltage determines the lowest usable sup-ply voltage for an application. in battery-powered systems, this determines the useful end-of-life battery voltage. since the max1735 s pass element is an n-channel mosfet, dropout voltage is the product ofr ds(on) and the load current; see electrical characteristics and dropout voltage vs. load current in the typical operating characteristics for details. the max1735 operating (ground pin) current typicallyremains below 125? at full load in dropout. ___________________chip information transistor count: 293 max1735 200ma, negative-output, low-dropout linear regulator in sot23 _______________________________________________________________________________________ 9 downloaded from: http:///
max1735 200ma, negative-output, low-dropout linear regulator in sot23 sot-23 5l .eps e 1 1 21-0057 package outline, sot-23, 5l maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 10 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2003 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) downloaded from: http:///
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