august 2000 1 mic39100/39101/39102 mic39100/39101/39102 micrel mic39100/39101/39102 evaluation board 1a low-voltage low-dropout regulator general descriptionthis evaluation board can be used to evaluate several of micrels new, low voltage, high current, low-dropout linear voltage regulators. the mic39100 is a three-terminal ldo offered in the sot-223 surface mount, power package. the mic39101 is a 1a ldo in a power so-8 package that offers the added functionality of an enable pin and an error flag output. the mic39102 is an adjustable version of the mic39100 in a power so-8 package and it also has the added functionality of an enable pin, allowing the user to disable the device and put it into a zero-current off mode state. the board has two layouts, one on the topside to accommodate the mic39100 and one on the backside to accommodate the mic39101/2. this one board can easily be used to evaluate any one of these parts. requirements the evaluation board requires a power supply capable of supplying a minimum of 1a of output current. the maximum voltage of that power supply should be at least 5v. these parts are intended for 3.3v to 2.5v and 3.3v or 2.5v to 1.8v conversion. a high voltage power supply should not be needed. the mic39100/1/2 has an input voltage range of 2.25v to 16v, therefore it is not limited to just 5v systems. circuit description the mic39100/1/2 regulators are simple to implement, re- quiring only an output capacitor for proper operation. an input cap is required when the power supply is greater than 4 away from the device. all evaluation boards include an input capacitor within 1 of the device. this is the recommended maximum distance away from the device that a capacitor should be placed. a minimum of 10 f of output capacitance is required for the mic39100/1/2. using large values of capacitance at the inputand output will help to improve transient response. table 1 shows the bill of materials for the different devices. mic39101/mic39102 the mic39101 circuit implements an error flag and an enable function. the enable function allows the user to put the device into a zero-current off state when the regulator is not required. the enable pin is an active-high pin and needs to be pulled high ( >2v) to enable the device and pulled low ( < 0.8v) to disable the device. the error flag function is a voltage monitor 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 that indicates when the output falls out of regulation for anyreason. the error flag output is an open-collector output, which is active-low, and requires a pull-up resistor for proper operation. boards assembled with the mic39101 have a 47k pull-up resistor from flg to the input voltage. the mic39102 is an adjustable regulator that implements anenable pin that allows the user to disable the device. the enable pin is also active-high and requires that pin to be pulled high to turn-on the output and pulled low to disable the output. a jumper (jp1)is available to tie that pin to either the input or to ground. the output voltage of the mic39102 is adjustable down to the band gap voltage of 1.24v. the board is set up with four set voltage options, a through d. a fifth option is available that can be custom set. the equation to set the output voltage is as follows: vv1 r1 r2 out ref =+ ?? ? ?? ? v 1.24v ref = on the board as it stands, r1 is set to 10k . using the equation and knowing that r1 = 10k , a custom voltage can be determined by solving for r2 and placing an 0805 or 1206resistor in the slot prepared and labeled e. r2 v vv r1 ref out ref = ? ?? ? ?? ? r2 1.24v v 1.24v 10k out = ? ?? ? ?? ? leaving all jumpers open sets the output voltage to the bandgap voltage, 1.24v. minimum load all of the devices require a minimum load of 10ma. a resistor is included on the board to provide a minimum load of 10ma. the resistor value is different depending on the voltage option that the board has. the mic39102 has a 140 resistor to maintain approximately 10ma at 1.4v output voltage. the140 resistor can be changed to set a 10ma load depending upon the desired output voltage. downloaded from: http:///
mic39100/39101/39102 micrel mic39100/39101/39102 2 august 2000 out in gnd r1b mic39100-x.xbm c2b gnd v in c1b v out figure 1. mic39100, sot-223 regulator schematic out in gnd r7 mic39101-x.xbm c1 gnd v in c2 v out j2 j5 flg en j4 jp1 1 2 3 j6 j3 flag r8 1C2 = on2C3 = off floating = off figure 2. mic39101, power sop-8 regulator schematic out in gnd r610k mic39102bm c1 gnd v in c2 v out j2 j5 adj en j4 jp1 1 2 3 j6 j3 r8 1C2 = on2C3 = off floating = off r5 76.8k r4 47.5k r3 30.1k r2 22.1k gnd r1 open/custom figure 3. mic39102, adjustable regulator schematic downloaded from: http:///
august 2000 3 mic39100/39101/39102 mic39100/39101/39102 micrel bill of materials item part number manufacturer description qty. c1b tpsc106m025r0500 avx 10 f, 25v, tantalum 1 c2b tpsc106m025r10500 avx 10 f, 25v, tantalum 1 r1b avx 240 (2.5v) or 180 (1.8v) 5% 1/8w 1 u1b mic39100-x.xbs micrel ldo regulator 1 c1 tpsc106m025r0500 avx 10 f, 25v, tantalum 1 c2 tpsc106m025r10500 avx 10 f, 25v, tantalum 1 r7 470 5% 1/8w, size 0805 1 r8 avx 240 (2.5v) or 180 (1.8v) 5% 1/8w 1 u1 mic39101-x.xbm micrel ldo regulator 1 c1 tpsc106m025r0500 avx 10 f, 25v, tantalum 1 c2 tpsc106m025r0500 avx 10 f, 25v, tantalum 1 r1 open r2 22.1k 1% 1/8w, size 0805 1 r3 30.1k 1% 1/8w, size 0805 1 r4 47.5k 1% 1/8w, size 0805 1 r5 76.8k 1% 1/8w, size 0805 1 r6 10k 1% 1/8w, size 0805 1 r7 open r8 140 1% 1/8w, size 0805 1 u1 mic39102bm micrel ldo regulator 1 downloaded from: http:///
mic39100/39101/39102 micrel mic39100/39101/39102 4 august 2000 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 any 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 patent right of micrel inc. ? 2000 micrel incorporated downloaded from: http:///
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