4707 dey road liverpool, n.y. 13088 m.s.kennedy corp. (315) 701-6751 features: series fast transient response low dropout voltage: 340mv @ 3a low noise: 40uvrms (10hz to 100khz) 1ma quiescent current fixed output voltages: 1.5v, 1.7v, 1.8v, 1.9v, 2.0v, 2.5v, 3.3v no protection diodes required stable with 10uf output capacitor available with top tab or tabless package available in four lead configurations contact msk for mil-prf-38534 qualification status description: the msk 5142 series regulators offer a low 340mv dropout voltage while supplying to 3a of output current. with fast transient response, these regulators have very low output noise. excellent line and load regulation characteristics ensure accurate performance for multiple applications with a low operating quiescent current of 1ma. these regulators offer internal short circuit current limit, thermal limiting and reverse current protection which eliminates the need for external components and excessive derating. the msk 5142 series regulators are available in a hermetically sealed space efficient to-257 package with multiple lead form options. equivalent schematic 5142 typical applications pin-out information post regulator for switching power supplies battery powered equipment microprocessor power supplies pre-amplifier power supplies gnd vout vin 1 2 3 1 preliminary rev. - 10/10 mil-prf-38534 certified 3a low noise, fixed output ldo regulator top tab no tab
20v 1.5a 20v -55c to +125c -40c to +85c supply voltage output current differential input voltage case operating temperature range msk 5142h msk 5142 in i out vin t c t st t ld t j absolute maximum ratings 2 electrical specifications storage temperature range lead temperature range (10 seconds) junction temperature -65c to +150c 300c +150c 1 2 3 4 5 6 7 8 the output is decoupled to ground using a 100 f low esr tantalum capacitor in parallel with a 1 f ceramic capacitor. see figure 1 for typical circuit. guaranteed by design but not tested. typical parameters are representative of actual device performance but are for reference o nly. industrial grade devices shall be tested to subgroups 1 unless otherwise requested. military grade devices ("h" suffix) shall be 100% tested to subgroups 1,2 and 3. subgroup 1 ta=+25c subgroup 2 ta=+125c subgroup 3 ta=-55c not applicable to versions where vin + v dropout < vin min. the minimum input voltage requirement must be maintained. reference current limit typical performance curves for input to output differential limitations. continuous operation at or above absolute maximum ratings may adversely effect the device performance and/or life cycle. notes: preliminary rev. - 10/10 7
application notes 3 input bypass capacitors unless the regulator is located very close to the main input filter capacitor, a 1 f to 10 f low esr tantalum capacitor should be added to the regulator's input to maximize tran- sient response and minimize power supply transients. a 0.1 f ceramic capacitor should also be used for high fre- quency bypassing. figure 1 output capacitor selection for most applications a 10 f low esr tantalum capacitor, as close to the regulators output as possible, is all that is required for the msk 5142 to be stable. when using a 10 f capacitor on the lower output voltage devices, a minimum esr is required of the capacitor. this requirement decreases from 20m on the 1.5v output regulator to 5m on the 3.3v output regulator. with an increase in capacitance, the minimum esr requirement decreases. at 100 f, the mini- mum esr requirement decreases to 5m for all versions of the msk 5142. to reduce ringing and improve transient response, capacitors with slightly larger esr in the range of 20m to 50m provides improved damping. capacitors with higher esr can be combined in parallel with low esr ceramic capacitors for good high frequency response and settling time. the maximum esr value must be less than 3 . care must be taken when selecting a ceramic type. the x5r and x7r are the best choice for output stability when considering response due to applied voltage and tem- perature. load regulation in voltage regulator applications where very large load cur- rents are present, the load connection is very important. the path connecting the output of the regulator to the load must be extremely low impedance to avoid affecting the load regulation specifications. as shown in figure 2, any impedance (rs) in this path will form a voltage divider with the load. for best results the ground pin should be connected directly to the load as shown in figure 2. the direct connec- tion eliminates the effect the potential voltage drop in the power ground path can have on the internal ground sensing, thus improving load regulation. the msk 5142 ground pin trace must be designed to carry the ground pin current with- out significant voltage drops. see typical performance curves. figure 2 overload protection the msk 5142 series regulators feature both current limit and thermal overload protection. within the safe operating region, the regulators will current limit above their 1.6amp rating. as the input to output voltage increases, however, the current limit decreases to keep the output transistor within its power dissipation limitation. see the current limit typical curves for conditional performance detail. if the de- vice heats enough to exceed its rated die junction tempera- ture due to excessive ambient temperature, improper heat sinking etc., the regulators also shutdown until an appropri- ate junction temperature is maintained. to bring the regula- tor out of shutdown, the device input may need to be cycled to zero and power reapplied to eliminate the shutdown con- dition. reverse voltage protection the regulators are protected against reverse input and out- put voltages. reverse input voltages up to 20v will be blocked from the input while current flow is limited to less than 1ma. the reverse voltage on the input is also pre- vented from appearing on the output and the load. when the input voltage is pulled down to ground and the output is held up by a second source, the current flow between them is limited to typically 600 a. see the electrical specifica- tions table. preliminary rev. - 10/10
to select a heat sink for the msk 5142, the following for- mula for convective heat flow may be used. governing equation: t j = p d x (r jc + r cs + r sa ) + t a where t j = junction temperature p d = total power dissipation r jc = junction to case thermal resistance r cs = case to heat sink thermal resistance r sa = heat sink to ambient thermal resistance t a = ambient temperature power dissipation=(vin-vout) x i out next, the user must select a maximum junction tempera- ture. the absolute maximum allowable junction temperature is 150c. the equation may now be rearranged to solve for the required heat sink to ambient thermal resistance (r sa ). example: an msk 5142 is connected for vin=+5v and vout=+3.3v. i out i s a continuous 2a dc level. the am- bient temperature is +25c. the maximum desired junc- tion temperature is +125c. r jc =5.6c/w and r cs =0.15c/w for most thermal greases power dissipation=(5v-3.3v) x (2a) =3.4 watts solve for r sa: 125c - 25c 3.4w = 25.5c/w in this example, a heat sink with a thermal resistance of no more than 25.5c/w must be used to maintain a maximum junction temperature of no more than 125c. vin min=minimum input voltage vout max=maximum output voltage across the full v drop =worst case dropout voltage (typically 430mv) i out peak=maximum load current gnd pin current=max. gnd pin current at i out peak application notes cont'd minimizing power dissipation: to maximize the performance and reduce power dissipation of the msk 5142 series devices, vin should be maintained as close to dropout or at vin minimum when possible. see input supply voltage requirements. a series resistor can be used to lower vin close to the dropout specification, lower- ing the input to output voltage differential. in turn, this will decrease the power that the device is required to dissipate. knowing peak current requirements and worst case volt- ages, a resistor can be selected that will drop a portion of the excess voltage and help to distribute the heating. the circuit below illustrates this method. the maximum resistor value can be calculated from the following: r1 max = where: vin min - (vout max + v drop ) i out peak + gnd pin current temperature range r sa = - 3.8c/w - 0.15c/w heat sink selection 4 preliminary rev. - 10/10
typical performance curves 5 preliminary rev. - 10/10
typical performance curves cont'd 6 preliminary rev. - 10/10
7 mechanical specifications ordering information note: all dimensions are 0.010 inches unless otherwise labeled. esd triangle indicates pin 1. msk5142-1.8 h t d lead configurations (gull wing not available with top tab version) s= straight; u= bent up; d= bent down package style t=top tab; blank=no tab screening blank= industrial h= mil-prf-38534 class h output voltage 1.5=+1.5v; 1.7=+1.7v; 1.8=+1.8v; 1.9=+1.9v; 2.0=+2.0v; 2.5=+2.5v; 3.3=+3.3v general part number weight=2.9 grams typical preliminary rev. - 10/10
the information contained herein is believed to be accurate at the time of printing. msk reserves the right to make changes to its products or specifications without notice, however, and assumes no liability for the use of its products. please visit our website for the most recent revision of this datasheet. contact msk for mil-prf-38534 qualification status. msk5142-1.8 h g 8 mechanical specifications m.s. kennedy corp. 4707 dey road, liverpool, new york 13088 phone (315) 701-6751 fax (315) 701-6752 www.mskennedy.com ordering information the above example is a +1.8v, military regulator with gull wing leads and no tab. note: all dimensions are 0.010 inches unless otherwise labeled. lead configurations (gull wing not available with top tab version) s= straight; u= bent up; d= bent down; g=gull wing package style t=top tab; blank=no tab screening blank= industrial h= mil-prf-38534 class h output voltage 1.5=+1.5v; 1.7=+1.7v; 1.8=+1.8v; 1.9=+1.9v; 2.0=+2.0v; 2.5=+2.5v; 3.3=+3.3v general part number weight=2.9 grams typical preliminary rev. - 10/10
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