lx8940 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 1 copyright ? 2000 rev. 1.3a, 2005-11-18 www. microsemi . com 5v low dropout regulator tm ? description the lx8940 is a 5v, low dropout, low quiescent current regulator rated for 1a of output current. it can regulate with as low as 0.4v headroom between the input and output voltages, thus minimizing power dissipation. in addition, it can be used in applications where worst case supplies require a low input-output differential to maintain regulation. this feature makes it ideal for computer monitors that have to comply with energy-efficient / "green pc" programs, where the input voltage drops to only a few tenths of a volt above the output when power supply enters sleep-mode operation. important: for the most current data, consult microsemi ?s website: http://www.microsemi.com product highlight part vin out gnd lx8940 0.1f 10f 5v / 100ma 5.3v key features ? 2% internally trimmed output ? output current in excess of 1a ? input-output differential less than 0.4v at 1a ? reverse battery protection ? 60v load dump protection ? -50v reverse transient protection ? short circuit protection ? internal thermal overload protection ? available in 3-lead plastic to- 220 ? drops in most lm2940 sockets applications ? small headroom battery applications ? high efficiency linear regulators ? post regulators for switching power supplies ? green pc monitor applications t a = 25c c o = 47f electrolytic c in = 1f v in = 5.3v load transient response output voltage (20mv/ div.) output current (50ma/ div.) 5.00v 4.98v 100ma 0ma 125c 25c -40c 600 500 400 300 200 100 0 100 500 1000 dropout voltage (mv) output current (ma) dropout voltage vs. output current v.s temperature time (20s / div.) package order info p plastic to-220 3-pin t a ( c) rohs compliant / pb-free transition dc: 0543 0 to 125 lx8940cp -40 to 125 lx8940ip note: available in tape & reel. append the letters ?tr? to the part number. (i.e. lx8940ip-tr) l l x x 8 8 9 9 4 4 0 0
lx8940 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 2 copyright ? 2000 rev. 1.3a, 2005-11-18 www. microsemi . com 5v low dropout regulator tm ? absolute maximum ratings input voltage (vin )......................................................................................... -15v to 26v maximum operating junc tion temperat ure .............................................................. 150c storage temperature ra nge.........................................................................-65 c to 150c peak package solder reflow temp. ( 40 seconds max. expos ure) ................. 260c (+0,-5) note: exceeding these ratings could cause damage to the device. all voltages are with respect to ground. currents are positive into, negative out of specified terminal. pin numbers refer to dil packages only thermal data p plastic to-220 3-pin thermal resistance - junction to t ab , jt 3.0 c/w thermal resistance - junction to a mbient , ja 60 c/w junction temperature calculation: t j = t a + (p d x ja ). the ja numbers are guidelines for the thermal performan ce of the device/pc-board system. all of the above assume no ambient airflow. package pin out 1 2 3 tab is gnd gnd output input p p ackage (top view) rohs / pb-free 100% matte tin lead finish recommended operating conditions lx8940 parameter symbol min typ max units input voltage vin note 2 26 v load current (with adequate heatsinking) 5 1000 ma maximum line transient (load dump), vo < 5.5v 60 v input capacitor (vin to gnd) 0.1 f output capacitor with esr of 10 ? max., (v out to gnd & v sb to gnd) 10 f note 2: v in(min) = 1.2 ? v (max) see dropout voltage maximum limit. p p a a c c k k a a g g e e d d a a t t a a
lx8940 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 3 copyright ? 2000 rev. 1.3a, 2005-11-18 www. microsemi . com 5v low dropout regulator tm ? electrical characteristics unless otherwise specified, the following specifications apply over the operating ambient temperature -40 c to +125c for the lx8940ip and 0c to +125c for lx8940cp; v in = 10v, i o = 1a, c out = 22f, and for dc characteristics only. low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the ambient temperature.) lx8940 parameter symbol test conditions min typ max units ` section header output voltage v o i o = 0a, t a = 25c 4.85 5 5.15 v line regulation ? v oi 7v < v in < 26, i o =5ma 1 50 mv load regulation ? v ol 50ma < i o < 1a 10 50 mv output impedance (note 3) r o 100ma dc and 20ma rms , f o = 120hz 200 m ? i o < 5ma, 7 < v in < 26v 3 15 ma i o = 500ma 30 50 ma quiescent current i q i o = 1000ma 115 180 ma output noise voltage (note 3) v orms 10hz ? 100khz, i o = 5ma 150 v rms long term stability (note 3) 20 mv / 1000hr ripple rejection (note 3) r r f o = 120hz, 1v rms , i o = 100ma 66 db i o = 100ma 150 300 mv i o = 500ma 275 500 mv dropout voltage ? v i o = 1a 400 800 mv current limit i cl v in = 26v 1 1.2 a maximum operational input voltage v in(max) 26 31 v maximum line transient v in(tr) r o = 100 ? , t < 100ms 60 v note 3: these parameters, although gua ranteed, are not tested in production. simplified block diagram overvoltage thermal shutdown 1 regulator bias 1.23v reference + _ 2 3 input voltage c1 0.1f c2 10f output voltage lx8940 input output gnd * required if regulator is located far from power supply filter figure 1 ? simplified block diagram e e l l e e c c t t r r i i c c a a l l s s
lx8940 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 4 copyright ? 2000 rev. 1.3a, 2005-11-18 www. microsemi . com 5v low dropout regulator tm ? application note the advantages of using a low-dropout regulator such as the lx8940 is the need for less ?headroom? for full regulation, and the inherent reverse polarity protection provided by the pnp output device. a typical npn regulator design requires an input to output differential of approximately two volts minimum. this is due to the 2vbe + vcesat of the npn darlington used in the output, coupled with the voltage drop across the current limit resistor. in contrast, the ?pnp regulator? uses a single series pass transistor with its single vces at, thus the lower input to output voltage differential or dropout voltage. in some applications the regulator output voltage is used not only as a power supply but also as a voltage reference for control systems. in such cases not just the temperature stability of the output is important bu t also the initial accuracy. lx8940 fills this need as the internal bandgap reference is trimmed allowing a typical output voltage tolerance of 1%. external capacitors to stabilize the outputs and prevent oscillation (perhaps by many volts) external capacitors are required. the minimum recommended value for the output capacitors is 10 f, although the actual size and type will likely vary according to the particular a pplication, e.g., operating temperature range and load. another consideration is the effective series resistance (esr) of the capacitor. capacitor esr will vary by manufacturer. consequently, some evaluation may be required to determine the minimum value of the output capacitors. generally worst case occurs at the maximum load and minimum ambient temperature. the size of the output capacitor can be increased to any value above the minimum. one possible advantage of this would be to maintain the output voltage during brief periods of negative input transients the output capacitors chosen should be rated for the full range of ambient temperature over which the circuit will be exposed and expected to operate. for example, many aluminum type electrolytic capacitors change values at cold temperatures. the effective capacitance is reduced and regulator stability is affected. tantalum capacitors are a good choice for these types of environments. output protection the output features fault protection against over voltage as well as a thermal shutdown feature. if the input voltage rises above 33v (load dump), the output shuts down automatically. the internal circ uitry is thus protected and the ic is able to survive higher voltage transients than might otherwise be expected. the thermal shutdown output effectively guards against overheating of the die and protects the device from being damaged. a a p p p p l l i i c c a a t t i i o o n n s s
lx8940 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 5 copyright ? 2000 rev. 1.3a, 2005-11-18 www. microsemi . com 5v low dropout regulator tm ? package dimensions p 3-pin plastic to-220 a g f q b d h c j r k l n s t u 123 note: 1. dimensions do not include mold flash or protrusions; these shall not exceed 0.155mm(.006?) on any side. lead dimension shall not include solder coverage. m illimeters i nches dim min max min max a 14.22 15.88 0.560 0.625 b 9.65 10.67 0.380 0.420 c 3.56 4.83 0.140 0.190 d 0.51 1.14 0.020 0.045 f 3.53 4.09 0.139 0.161 g 2.54 bsc 0.100 bsc h 6.35 0.250 j 0.30 1.14 0.012 0.045 k 12.70 14.73 0.500 0.580 l 1.14 1.27 0.045 0.050 n 5.08 typ 0.200 typ q 2.54 3.05 0.100 0.120 r 2.03 2.92 0.080 0.115 s 1.14 1.40 0.045 0.055 t 5.84 6.86 0.230 0.270 u 0.508 1.14 0.020 0.045 m m e e c c h h a a n n i i c c a a l l s s
lx8940 p roduction d ata s heet microsemi integrated products division 11861 western avenue, garden grove, ca. 92841, 714-898-8121, fax: 714-893-2570 page 6 copyright ? 2000 rev. 1.3a, 2005-11-18 www. microsemi . com 5v low dropout regulator tm ? notes production data ? information contained in this document is proprietary to microsemi and is current as of publication date. this document may not be modified in any way without the express written consent of microsemi. product processing does not necessarily include testing of all parameters. microsemi reserves the right to change the configuration and performance of the product and to discontinue product at any time. n n o o t t e e s s
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