1 features output current to 3a output accuracy to 1.5% over temperature dropout voltage (typical) 1.2v @ 3a fast transient response fault protection current limit thermal shutdown package options 3l to-220 tab (v out ) cs5203-1 3a adjustable linear regulator 1 cs5203-1 the cs5203-1 linear regulator pro- vides 3a at adjustable output volt- ages with an accuracy of 1.5%. the device uses two external resis- tors to set the output voltage with- in a 1.25v to 5.5v 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 voltage less than 1.4v at 3a output current. device pro- tection includes overcurrent and thermal shutdown. the cs5203-1 is pin compatible with the lt1085 family of linear regulators but has lower dropout voltage. the regulator is available in to-220 and surface mount d 2 packages. cs5203-1 1 adj 2v out (tab) 3v in description 3l d 2 pak tab (v out ) 1 consult factory for fixed output voltage versions. 5.0v cs5203-1 v in adj 124 ? 1% 200 ? 1% 3.3v @ 3a 0.1 f 5v 22 f 5v 10 f 5v v out application diagram a company ? rev. 6/28/99 cherry semiconductor corporation 2000 south county trail, east greenwich, ri 02818 tel: (401)885-3600 fax: (401)885-5786 email: info@cherry-semi.com web site: www.cherry-semi.com
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 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. note 4: minimum load current is defined as the minimum output current required to maintain regulation. the reference resistor i n the output divider is usually sized to fulfill the minimum load current requirement. note5: guaranteed by design, not 100% functionally tested in production. note 6: guaranteed by design, not 100% parametrically tested in production. however, every part is subject to functional testi ng for thermal shutdown. 2 cs5203-1 absolute maximum ratings supply voltage, v in ............................................................................................................................... ......................................7v operating temperature range.................................................................................................... ............................-40c to 70c junction temperature ........................................................................................................... .................................................150c storage temperature range ...................................................................................................... ............................-60c to 150c esd damage threshold........................................................................................................... .................................................2kv lead temperature soldering wave solder (through hole styles only) .....................................................................................10 s ec. max, 260c peak reflow (smd styles only) ......................................................................................60 sec. max above 183c, 230c peak package pin description package pin # pin symbol function parameter test conditions min typ max unit electrical characteristics: c in = 10f, c out = 22f tantalum, v out + v dropout < v in < 7v, 0c t a 70c, t j +150c, unless otherwise specified, i full load = 3a. adjustable output voltage (cs5203-1) reference voltage v in ? v out = 1.5v; v adj = 0v 1.235 1.254 1.273 v (notes 1 and 2) 10ma i out 3a (-1.5%) (+1.5%) line regulation 2v v in ? v out 5.75v; i out = 10ma 0.02 0.20 % load regulation v in ? v out = 2v; 10ma i out 3a 0.04 0.4 % (notes 1 and 2) dropout voltage (note 3) i out = 3a 1.15 1.40 v current limit v in ? v out = 3v; t j 25c 3.1 4.6 a minimum load current (note 4) v in = 7v; v adj = 0 0.6 2.0 ma adjust pin current v in ? v out = 3v; i out = 10ma 50 100 a thermal regulation (note 5) 30ms pulse; t a = 25c 0.002 0.020 %/w ripple rejection (note 5) f = 120hz; i out = 3a; v in ? v out = 3v; 80 db v ripple = 1v pp thermal shutdown (note 6) 150 180 210 c thermal shutdown hysteresis (note 6) 25 c d 2 pak to-220 1 1 adj adjust pin (low side of the internal reference). 22 v out regulated output voltage (case) 33 v in input voltage.
cs5203-1 3 dropout voltage (v) output current (a) 0.90 0.75 0.85 0.95 1.00 1.05 1.10 1.15 1.20 0.80 0.00 3.00 2.70 2.40 2.10 1.80 1.50 1.20 0.90 0.60 0.30 t case = 25 c t case = 0 c t case = 125 c 030 -0.3 +0.3 reference voltage deviation (%) t j ( c) 60 90 120 +0.2 +0.1 0 -0.1 -0.2 dropout voltage vs. output current bandgap reference voltage deviation vs. temperature 1.00 2.00 3.00 4.00 5.00 minimum load current (ma) v in ? v out (v) t case = 0 c t case = 125 c 6.00 0.40 0.45 0.50 0.55 0.60 0.65 7.00 8.00 t case = 25 c minimum load current vs v in -v out typical performance characteristics error amplifier + output current limit - v in v out adj thermal shutdown bandgap reference block diagram 10 1 frequency (hz) ripple rejection (db) 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 10 2 10 3 10 4 10 5 10 6 ripple rejection vs. frequency
4 cs5203-1 03060 45 i adj ( a) t a ( c) 55 65 75 90 120 adjust pin current adjust pin current vs. temperature typical performance characteristics: continued +200 0 -200 -200 3 0 0 5 10 1 time ( s) ? v out (mv) i(a) v in = 5v v out = 3.3v c in = 100 f c out = 10 f tantalum 70.00 68.50 67.00 65.50 64.00 62.50 61.00 59.50 58.00 56.50 55.00 0.0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 3.0 i out (a) adjust pin current ( a) transient response adjust pin current vs output current 6.00 5.00 4.00 3.00 2.00 1.00 0.00 1.00 2.00 3.00 4.00 5.00 6.00 7.00 i sc (a) v in - v out (v) short circuit current vs v in -v out 54.00 62.00 66.00 68.00 1.00 2.00 6.00 8.00 v in - v out (v) adjust pin current ( a) 64.00 60.00 56.00 58.00 7.00 3.00 4.00 5.00 t case = 0 c t case = 25 c t case = 125 c adjust pin current vs. v in -v out
5 cs5203-1 applications information the cs5203-1 linear regulator provides adjustable volt- ages at currents up to 3a. the regulator is protected against overcurrent conditions and includes thermal shutdown. the cs5203-1 has a composite pnp-npn output transistor and requires an output capacitor for stability. a detailed procedure for selecting this capacitor is included in the stability considerations section. the cs5203-1 has an output voltage range of 1.25v to 5.5v. 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 50a) 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 2ma. r1 and r2 should be the same type, e.g. metal film for best tracking over temperature. while not required, a bypass capacitor between the adjust pin and ground will improve ripple rejection and transient response. a 0.1f tantalum capacitor is recommended for ?first cut? design. type and value may then be varied to optimize perfor- mance vs. price. figure 1. resistor divider scheme. the 5203-1 linear regulator has an absolute maximum specification of 7v for the voltage difference between v in and v out . however, the ic may be used to regulate volt- ages in excess of 7v. the main considerations in such a design are power-up and short circuit capability. in most applications, ramp-up of the power supply to v in is fairly slow, typically on the order of several tens of mil- liseconds, while the regulator responds in less than one microsecond. in this case, the linear regulator begins charging the load as soon as the v in to v out differential is large enough that the pass transistor conducts current. the load at this point is essentially at ground, and the supply voltage is on the order of several hundred millivolts, with the result that the pass transistor is in dropout. as the sup- ply to v in increases, the pass transistor will remain in dropout, and current is passed to the load until v out reaches the point at which the ic is in regulation. further increase in the supply voltage brings the pass transistor out of dropout. the result is that the output voltage fol- lows the power supply ramp-up, staying in dropout until the regulation point is reached. in this manner, any output voltage may be regulated. there is no theoretical limit to the regulated voltage as long as the v in to v out differen- tial of 7v is not exceeded. however, the possibility of destroying the ic in a short circuit condition is very real for this type of design. short circuit conditions will result in the immediate operation of the pass transistor outside of its safe operating area. over- voltage stresses will then cause destruction of the pass transistor before overcurrent or thermal shutdown circuit- ry can become active. additional circuitry may be required to clamp the v in to v out differential to less than 7v if fail- safe operation is required. one possible clamp circuit is illustrated in figure 2; however, the design of clamp cir- cuitry must be done on an application by application basis. care must be taken to ensure the clamp actually protects the design. components used in the clamp design must be able to withstand the short circuit condition indefinitely while protecting the ic. figure 2. short circuit protection circuit for high voltage application. 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 stability considerations v in v out v adj external supply v out v out v in cs5203-1 v in adj r 1 r 2 c 1 c adj v out c 2 v ref i adj r1 + r2 r1 adjustable operation
6 cs5203-1 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 22f tantalum capacitor will work for most applications, but with high current regulators such as the cs5203-1 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 network 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 cs5203-1 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 figure 3 is recommended. figure 3. protection diode scheme for large output capacitors. since the cs5203-1 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. for the adjustable regulator, the best load regulation occurs when r1 is connected directly to the output pin of the regulator as shown in figure 4. 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 4. grounding scheme for the adjustable output regulator to min- imize parasitic resistance effects. the cs5203-1 linear regulator includes thermal shutdown and current limit circuitry to protect the device. high power regulators such as these usually operate at high junction temperatures so it is important to calculate 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 cs5203-1 , and elec- trical isolation may be required for some applications. thermal compound should always be used with high cur- rent regulators such as these. the thermal characteristics of an ic depend on the follow- ing four factors: 1. maximum ambient temperature t a (c) 2. power dissipation p d (watts) 3. maximum junction temperature t j (c) 4. thermal resistance junction to ambient r ja (c/w) these four are related by the equation calculating power dissipation and heat sink requirements v out r c v in conductor parasitic resistance cs5203-1 v in adj r load r 1 r 2 r1 + r2 r1 output voltage sensing v out v in cs5203-1 v in adj r 1 r 2 c 1 v out c 2 c adj in4002 (optional) protection diodes applications information: continued
7 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) ?v 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 (c/w) 2. thermal resistance of the case to heat sink, r cs (c/w) 3. thermal resistance of the heat sink to the ambient air, r sa (c/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 3.5 ? c/w as a single figure for a given package type based on an average die size. for a high current regulator such as the cs5203-1 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 inter- face (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 permissible value of r ja can be calculated and the proper heat sink selected. for further discussion on heat sink selection, see application note ?thermal management for linear regulators.? applications information: continued cs5203-1
8 part number type description cs5203-1gt3 3a, adj. output 3 l to-220 straight CS5203-1GDP3 3a, adj. output 3 l d 2 pak cs5203-1gdpr3 3a, adj. output 3 l d 2 pak (tape & reel) ordering information rev. 6/28/99 package specification 3l 3l thermal data to-220 d 2 pak r jc typ 3.5 3.5 ? c/w r ja typ 50 10 - 50* ? c/w * depending on thermal properties of substrate. r ja = r jc + r ca package thermal data cs5203-1 ? 1999 cherry semiconductor corporation cherry semiconductor corporation reserves the right to make changes to the specifications without notice. please contact cherry semiconductor corporation for the latest available information. package dimensions in mm (inches) 3 lead d 2 pak (dp) 2.54 (.100) ref 10.31 (.406) 10.05 (.396) 8.53 (.336) 8.28 (.326) 0.91 (.036) 0.66 (.026) 1.40 (.055) 1.14 (.045) 4.57 (.180) 4.31 (.170) 1.68 (.066) 1.40 (.055) 2.74(.108) 2.49(.098) 1.40 (.055) 1.14 (.045) 0.10 (.004) 0.00 (.000) .254 (.010) ref 15.75 (.620) 14.73 (.580) 2.79 (.110) 2.29 (.090) 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)
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