1 features output current to 5a output trimmed to +/- 1% dropout voltage 1.15v @ 5a fast transient response fault protection circuitry thermal shutdown overcurrent protection safe area protection package options 3l to-220 tab (v out ) cs5205a-1 5a adjustable linear regulator 1 cs5205a-1 the cs5205a-1 linear regulator provides 5a at an adjustable volt- age with an accuracy of 1%. two external resistors are used to set the output voltage within a 1.25v to 13v range. the regulator is intended for use as a post regulator and microproces- sor supply. the fast loop response and low dropout voltage make this regulator ideal for applications where low voltage operation and good transient response are impor- tant. the circuit is designed to operate with dropout voltages as low as 1v depending on the output current level. the maximum quiescent cur- rent is only 10ma at full load. the regulator is fully protected against overload conditions with protection circuitry for safe operating area (soa), overcurrent and thermal shutdown. the cs5205a-1 is pin compatible with the lt1084 family of linear regulators but has lower dropout voltage. the regulator is available in to-220 and surface mount d 2 packages. block diagram 1 adj 2v out 3v in error amplifier + output current limit - v in v out adj thermal shutdown bandgap description 3l d 2 pak 1 june, 1999 - rev. 2 on semiconductor 2000 south county trail, east greenwich, ri 02818 tel: (401)885?600 fax: (401)885?786 n. american technical support: 800-282-9855 web site: www.cherry?emi.com
2 cs5205a-1 package pin description package pin # pin symbol function electrical characteristics: c in = 10 f, c out = 22 f tantalum, v in ?v out = 3v, v in 15v, 0? t a 70?, t j +150?, unless otherwise specified, i full load = 5a. parameter test conditions min typ max unit absolute maximum ratings supply voltage, v cc ............................................................................................................................... ......................................17v operating temperature range .................................................................................................... ..............................-40? to 70? junction temperature ........................................................................................................... ....................................................150? storage temperature range ...................................................................................................... ...............................-60? to 150? lead temperature soldering wave solder (through hole styles only) ........................................................................................1 0 sec. max, 260? peak reflow (smd styles only) .........................................................................................60 sec. max ab ove 183?, 230? peak adjustable output voltage reference voltage v in ?v out = 1.5v; v adj = 0v 1.241 1.254 1.266 v (notes 1 and 2) 10ma i out 5a (-1%) (+1%) line regulation 1.5v v in ?v out 6v; i out = 10ma 0.04 0.20 % load regulation v in ?v out = 1.5v; 0.08 0.4 % (notes 1 and 2) 10ma i out 5a dropout voltage (note 3) i out = 5a; t j 25? 1.15 1.25 v current limit v in ?v out = 3v; t j 25? 5.5 8.5 a v in ?v out = 9v 1.0 a minimum load current v in ?v out = 7v 1.2 6 ma adjust pin current 50 100 a adjust pin current change 1.5v v in ?v out 4v; 0.2 5.0 a 10ma i out 5a thermal regulation 30ms pulse; t a = 25? 0.003 %w ripple rejection f = 120hz; c adj = 25 f; i out = 5a 82 db temperature stability 0.5 % rms output noise 10hz f 10khz; t a = 25? 0.003 %v out thermal shutdown 150 180 ? thermal shutdown hysteresis 25 ? note 1: load regulation and output voltage are measured at a constant junction temperature by low duty cycle pulse testing. cha nges in out- put voltage due to thermal gradients or temperature changes must be taken into account separately. note 2: specifications apply for an external kelvin sense connection at a point on the output pin 1/4?from the bottom of the p ackage. note 3: dropout voltage is a measurement of the minimum input/output differential at full load. d 2 pak 3l to-220 1 1 adj adjust pin (low side of the internal reference). 22v out regulated output voltage (case). 33v in input voltage.
cs5205a-1 3 typical performance characteristics dropout voltage vs. output current reference voltage vs. temperature 0.025 0.000 0.050 0.075 0.100 0.200 01 2 3 4 5 output current (a) t case = 0 c 0.125 0.150 0.175 t case = 125 c t case = 25 c output voltage deviation (%) 0 10 130 -0.12 0.10 output voltage deviation (%) t j ( c) 20 30 40 50 60 70 80 90 100 110 120 0.08 0.06 0.04 0.02 0.00 -0.02 -0.04 -0.06 -0.08 -0.10 load regulation vs. output current 0.85 0.70 0.90 0.95 1.00 1.10 1.15 1.20 1.25 t case = 0 c t case = 125 c t case = 25 c 0.75 dropout voltage (v) output current (a) 012 34 5 1.05 0.80 123456 0.550 minimum load current (ma) v in ?v out (v) t case = 0 c t case = 125 c 7 0.875 1.200 1.525 1.850 2.175 2.500 8 9 t case = 25 c minimum load current 0.0 10 1 frequency (hz) ripple rejection (db) 10.0 20.0 30.0 40.0 50.0 60.0 70.0 80.0 90.0 100.0 10 2 10 3 10 4 10 5 t case = 25 c i out = 5a (v in ?v out ) = 3v v ripple = 1.6v pp c adj = 25 f ripple rejection vs. frequency
4 cs5205a-1 the cs5205a-1 linear regulator provides an adjustable voltage at currents up to 5a. the regulator is protected against short circuit, and include thermal shutdown and safe area protection (soa) circuitry. the soa protection circuitry decreases the maximum available output current as the input-output differential voltage increases. the cs5205a-1 has a composite pnp-npn output transis- tor and requires an output capacitor for stability. a detailed procedure for selecting this capacitor is included in the stability considerations section. the adjustable regulator (cs5205a-1) has an output volt- age range of 1.25v to 13v. an external resistor divider sets the output voltage as shown in figure 1. the regulator maintains a fixed 1.25v (typical) reference between the output pin and the adjust pin. a resistor divider network r1 and r2 causes a fixed cur- rent to flow to ground. this current creates a voltage across r2 that adds to the 1.25v across r1 and sets the overall output voltage. the adjust pin current (typically 50 a) also flows through r2 and adds a small error that should be taken into account if precise adjustment of v out is necessary. the output voltage is set according to the formula: v out = v ref () + i adj r2 the term i adj r2 represents the error added by the adjust pin current. r1 is chosen so that the minimum load current is at least 10ma. r1 and r2 should be the same type, e.g. metal film for best tracking over temperature. the adjust pin is bypassed to improve the transient response and ripple rejection of the regulator. figure 1. resistor divider scheme for the adjustable version. the output or compensation capacitor helps determine three main characteristics of a linear regulator: start-up delay, load transient response and loop stability. the capacitor value and type is based on cost, availability, size and temperature constraints. a tantalum or aluminum electrolytic capacitor is best, since a film or ceramic capaci- tor with almost zero esr, can cause instability. the alu- minum electrolytic capacitor is the least expensive solu- tion. however, when the circuit operates at low tempera- tures, both the value and esr of the capacitor will vary considerably. the capacitor manufacturers data sheet pro- vides this information. a 22 f tantalum capacitor will work for most applications, but with high current regulators such as the cs5205a-1 the transient response and stability improve with higher val- ues of capacitor. the majority of applications for this regu- lator involve large changes in load current so the output capacitor must supply the instantaneous load current. the esr of the output capacitor causes an immediate drop in output voltage given by: ? v = ? i esr for microprocessor applications it is customary to use an output capacitor network consisting of several tantalum and ceramic capacitors in parallel. this reduces the overall esr and reduces the instantaneous output voltage drop under load transient conditions. the output capacitor net- work should be as close as possible to the load for the best results. when large external capacitors are used with a linear regu- lator it is sometimes necessary to add protection diodes. if the input voltage of the regulator gets shorted, the output capacitor will discharge into the output of the regulator. the discharge current depends on the value of the capaci- tor, the output voltage and the rate at which v in drops. in the cs5205a-1 linear regulator, the discharge path is through a large junction and protection diodes are not usu- ally needed. if the regulator is used with large values of output capacitance and the input voltage is instantaneous- ly shorted to ground, damage can occur. in this case, a diode connected as shown in figure2 is recommended. figure 2. protection diode scheme for adjustable output regulator. since the cs5205a-1 is a three terminal regulator, it is not possible to provide true remote load sensing. load regula- tion is limited by the resistance of the conductors connect- ing the regulator to the load. output voltage sensing v out v in cs5205a-1 v in adj r 1 r 2 c 1 v out c 2 c adj in4002 (optional) protection diodes stability considerations v out v in cs5205a-1 v in adj r 1 r 2 c 1 v out c 2 v ref i adj c adj r1 + r2 r1 adjustable operation applications information
5 best load regulation occurs when r1 is connected directly to the output pin of the regulator as shown in figure 3. if r1 is connected to the load, r c is multiplied by the divider ratio and the effective resistance between the regulator and the load becomes r c () r c = conductor parasitic resistance figure 3. grounding scheme for the adjustable output regulator to min- imize parasitics. the cs5205a-1 linear regulator includes thermal shut- down and safe operating area circuitry to protect the device. high power regulators such as these usually oper- ate at high junction temperatures so it is important to cal- culate the power dissipation and junction temperatures accurately to ensure that an adequate heat sink is used. the case is connected to v out on the cs5205a-1, electrical isolation may be required for some applications. thermal compound should always be used with high current regu- lators such as these. the thermal characteristics of an ic depend on the follow- ing four factors: 1. maximum ambient temperature t a (?) 2. power dissipation p d (watts) 3. maximum junction temperature t j (?) 4. thermal resistance junction to ambient r ja (c/w) these four are related by the equation t j = t a + p d r ja (1) the maximum ambient temperature and the power dissi- pation are determined by the design while the maximum junction temperature and the thermal resistance depend on the manufacturer and the package type. the maximum power dissipation for a regulator is: p d(max) ={v in(max) ? out(min) }i out(max) +v in(max) i q (2) where v in(max) is the maximum input voltage, v out(min) is the minimum output voltage, i out(max) is the maximum output current, for the application i q is the maximum quiescent current at i out (max). a heat sink effectively increases the surface area of the package to improve the flow of heat away from the ic and into the surrounding air. each material in the heat flow path between the ic and the outside environment has a thermal resistance. like series electrical resistances, these resistances are summed to determine r ja , the total thermal resistance between the junction and the surrounding air. 1. thermal resistance of the junction to case, r jc (?/w) 2. thermal resistance of the case to heat sink, r cs (?/w) 3. thermal resistance of the heat sink to the ambient air, r sa (?/w) these are connected by the equation: r ja = r jc + r cs + r sa (3) the value for r ja is calculated using equation (3) and the result can be substituted in equation (1). the value for r jc is normally quoted as a single figure for a given package type based on an average die size. for a high current regulator such as the cs5205a-1 the majority of the heat is generated in the power transistor section. the value for r sa depends on the heat sink type, while r cs depends on factors such as package type, heat sink interface (is an insulator and thermal grease used?), and the contact area between the heat sink and the package. once these calculations are complete, the maximum per- missible value of r ja can be calculated and the proper heat sink selected. for further discussion on heat sink selection, see application note ?hermal management for linear regulators. calculating power dissipation and heat sink requirements v out r c conductor parasitic resistance cs5205a-1 v in adj r load r 1 r 2 r1 + r2 r1 applications information: continued cs5205a-1
part number type description cs5205a-1gt3 5a, adj. output 3l to-220 straight cs5205a-1gdp3 5a, adj. output 3l d 2 pak cs5205a-1gdpr3 5a, adj. output 3l d 2 pak (tape & reel) 6 ordering information cs5205a-1 package specification package dimensions in mm(inches) thermal data 3l 3l to-220 d 2 pak r jc typ 1.6 1.6 ?/w r ja typ 50 10 - 50* ?/w * depending on thermal properties of substrate. r ja = r jc + r ca package thermal data 3 lead to-220 (t) straight 5.33 (.210) 4.83 (.190) 2.79 (.110) 2.29 (.090) 1.02 (.040) 0.63 (.025) 0.56 (.022) 0.38 (.014) 1.40 (.055) 1.14 (.045) 4.83 (.190) 4.06 (.160) 6.17 (.243) ref 1.14 (.045) 1.52 (.060) 1.14 (.045) 1.40 (.055) 2.87 (.113) 2.62 (.103) 6.55 (.258) 5.94 (.234) 14.22 (.560) 13.72 (.540) 2.92 (.115) 2.29 (.090) 9.78 (.385) 10.54 (.415) 3.71 (.146) 3.96 (.156) 14.99 (.590) 14.22 (.560) 3 lead d 2 pak (dp) 2.54 (.100) ref 20 typ 10.31 (.406) 10.05 (.396) 15.75 (.620) 14.73 (.580) 8.53 (.336) 8.28 (.326) 0.91 (.036) 0.66 (.026) e?in 1.40 (.055) 1.14 (.045) 6 4 6 4 b 0.10(.004) 0.00(.000) 2.79 (.110) 2.29 (.090) b a 3 0 c 4.57 (.180) 4.31 (.170) 6 4 (both sides) 1.88 (.066) 1.40 (.055) 2.74(.108) 2.49(.098) 1.40 (.055) 1.14 (.045) on semiconductor and the on logo are trademarks of semiconductor components industries, llc (scillc). on semiconductor reserves the right to make changes without further notice to any products herein. for additional information and the latest available information, please contact your local on semiconductor representative. ?semiconductor components industries, llc, 2000
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