TSC TS2576 handbook
Contents
1. DECE 0 394 B 3 240 4440 0128 0 175 D 0 260 1 020 0 010 0 040 2760 29 44 1 087 1159 TO 263 5L Mechanical Drawin TO 263 DIMENSION B 14600 15870 0 575 0625 o 1573 1827 oos2 0 072 Ci e240 8280 0 324 0 326 TS2576 7 7 2003 12 rev A2. U U 152 74 U L TS2576 3A Step Down Switching Voltage Regulator TO 263 5L Pin assignment 1 Input 52KHz Oscillating Frequency AAA UpN Output Current up to 3A 3 Ground i Fesdback Enable Input Control 5 Enable General Description The TS2576 Series are step down switching regulators with all required active functions It is capable of driving 3A load with excellent line and load regulations These devices are available in fixed output voltages of 3 3V 5V and an adjustable output version The TS2576 series offers a high efficiency replacement for popular three terminal linear regulators Also it requires a minimum number of external components It substantially not only reduces the area of board size but also the size of heat sink and in some cases no heat sink is required The 4 tolerance on output voltage within specified input voltages and output load conditions is guaranteed Also the oscillator frequency accuracy is within 10 External shutdown is included Featuring 70pA typical standby current The output switch includes cycle by cycle current limiting as well as thermal shutdown for full protection under fault conditions This series are offered in 5 pin TO 263 TO 220 package Features Ordering Information Guaranteed 3A output current Operating Temp Package 3 3V 5V and adjustable versions Ambient Wide input voltage range up to 40V TS2576CZ5 XX TO 220 5L Internal oscillator of 52KHz fixed frequency eee
3. he regulator performance and requirements With relatively heavy load currents the circuit operates in the continuous mode inductor current always flowing But under light Load conditions the circuit will be force to the discontinuous mode inductor current falls to zero for a period of time For light loads less than approximately 300mA it may be desirable to operate the regulator in the discontinuous mode primarily because of the lower inductor values required for the discontinuous mode Indictors are available in different styles such as pot core toroid E frame bobbin core et as well as different core materials such as ferrites and powdered iron The least expensive the bobbin core type consists of wire wrapped on a ferrite rod core This type of construction makes for an inexpensive inductor but since the magnetic flux is not completely contained within the core it generates more electromagnetic interference EMI This EMI can cause problems in sensitive circuits or can give incorrect scope readings because of induced voltage in the scope probe An inductor should not be operated beyond its maximum rated current because it may saturate When an inductor begins to saturate the inductance decreases rapidly and the inductor begins to look mainly resistive the DC resistance of the winding This will cause the switch current to rise very rapidly Different inductor types have different saturation characteristics and this sho
4. itance Wiring inductance and even the scope probes used for transients evaluation To minimize these voltage spikes shortening the lead length and PCB traces is always the first thought Further more an additional small LC filter 30UH amp 100UF as shown in Figure 3 will possibly provide a 10X reduction in output ripple voltage and transients Heatsink and Thermal Consideration Although the TS2576 requires only a small heatsink for most cases the following thermal consideration is important for all operation With the package thermal resistances Oja and Ojc total power dissipation can be estimated as follows PD Vin x lq Vout Vin lout x Vsat When no heatsink is used the junction temperature rise can be determined by the following AT PDx Oja With the ambient temperature the actual junction temperature will be Tj ATj Ta If the actual operating junction temperature is out of the safe operating junction temperature typically 125 C then a heatsink is required When using a heatsink the junction temperature rise will be reduced by the following ATj PD x jc interface heatsink Also one can see from the above it is important to choose an heatsink with adequate size and thermal resistance such that to maintain the regulator s junction temperature below the maximum operating temperature TS2576 6 7 2003 12 rev A TO 220 5L Mechanical Drawin TO 220 DIMENSION MAX MIN MAX ENET
5. l Wide adjust version output voltage range from 1 23V TS28 6029 20 85 C to 37V 4 max at over line and load conditions TS257 6CM5 XX TO 263 5L Low standby current typ 70A at shutdown mode TS2576CM5 Requires only 4 external components Note Where XX denotes voltage option available are Thermal shutdown and current limit protection 12V 5V and 3 3V Leave blank for adjustable P product enhancement tested version Contact factory for additional voltage options Applications lt LCD Monitors lt Efficient Pre regulator for Linear Regulators lt ADD ON Cards Switching Regulators lt 4 Positive to Negative converter Buck Boost lt gt High Efficiency Step Down Regulators ENABLE Pin Input Voltage Vin operate 0 3V lt V lt Vin Power Dissipation P memalmid w Lo 0 Operating Junction Temperature Range Ty R Storage Temperature Range 65 150 Lead Soldering Temperature 260 C TO 220 5L TO 263 5L Package 5 S TS2576 1 7 2003 12 rev A Fixed Gain Error amp JAmp Comparator Driver Switch Thermal shutdown 1 234 Band Gap 92KHez Current Reference Ostillator Reset Limited Vin 12V 500mA Ta 25 C unless otherwise specified Parameter Conditions min Typ Max unit TS2576 3 3V i La a 1 02 Vo Output Voltage Note r 0 5A lt Doaa 3A 6V lt Vin lt 40V 0 96 Vo 1 04 Vo V a 1 TS2576 5V aana oats mar este 1 02 Vo E Output Voltage Note
6. pple voltage while larger value capacitors will reduce the ripple to approximately 20mV to 50mV The amount of output ripple voltage is primarily a function of the ESR Equivalent Series Resistance of the output capacitor and the amplitude of the inductor ripple current lwn Output Ripple Voltage linn x ESR of Court Some capacitors called high frequency low inductance or low ESR are recommended to use to further reduce the output ripple voltage to 10mV or 20mV However very low ESR capacitors such as tantalum capacitors should be carefully evaluated Catch Diode This diode is required to return path for the inductor current when the switch is off It should be located close to the TS2576 using short leads and short printed circuit traces as possible To satisfy the need to fast switching speed and low forward voltage drop Schottky diodes are widely used to provide the best efficiency especially in low output voltage switching regulators less than 5V Beside Fast Recovery high efficiency or ultra fast recovery diodes are also suitable But some types with an abrupt turn off characteristic may cause instability and EMI problems A fast recovery diode with soft recovery characteristics is better choice TS2576 5 7 Inductor Selection The TS2576 can be used for either continuous or discontinuous modes of operation Each mode has distinctively different operating characteristics which can affect t
7. r 0 5A lt 3A 8V lt Vin lt 40V 0 96 Vo 1 04 Vo V Figure 1 Efficiency Vinstzvns3A Lr TS2576 12V ET 7 1 02 Vo E Output Voltage Note 0 5A lt ie 3A 15V lt Vin lt 40V 0 96 Vo 1 04 Vo V Figure 1 Efficiency Vinstgvn 3A Lt TS2576 E 1 02Vo Feedback Voltage Note 0 5A lt E lt 3A 8V lt Vin lt 40V 0 96 Vo 1 04 Vo V Vout 5V Figure 2 Vin 12V Vout 5V 155 p wi x TS2576 2 7 2003 12 rev A Oscillator Frequency Note 2 Quiescent Current Note 3 Standby Current ENABLE 5V l _ Current Limit Note 2XNote4 Vout Output Leakage Current Note 3 ou testage curent noes PEEN 33 FW ENABLE 5V r2 eR wense to Note 1 External components such as the catch diode inductor input and output capacitors can affect switching regulator system performance Refer to Application information for details Note 2 The oscillator frequency reduces to approximately 11KHz in the event of fault conditions such as output short or overload And the regulated output voltage will drop approximately 40 from the nominal output voltage This self protection feature lowers the average power dissipation by lowering the minimum duty cycle from 5 down to approximately 2 Note 3 For these parameters FB is removed from Voy and connected to 12V to force the output transistor OFF Note 4 V aur pin sourcing current No diode inductor or capacitor connected to Vout Note 5 FB is
8. removed from V our and connected to OV TS2576 3 7 2003 12 rev A Unregulated Cin DC Input Figure 1 Fixed Voltage Version Unregulated Cin DC Input Vout 1 23 x 1 R2 R1 Figure 2 Adjustable Voltage Version Unregulated Cin DC Input Figure 3 LC filter for Low Output Ripple TS2576 4 7 2003 12 rev A Application Information It is required that VIN must be bypassed with at least a 100uUF electrolytic capacitor for stability Also it is strongly recommended the capacitors leads must be dept short and located near the regulator as possible For low operating temperature range for example below 25 C the input capacitor value may need to be larger This is due to the reason that the capacitance value of electrolytic capacitors decreases and the ESR increases with lower temperatures and ago Paralleling a ceramic or solid tantalum capacitor will increase the regulator stability at cold temperatures Output Capacitor An output capacitor is also required to filter the output voltage and is needed for loop stability The capacitor should be located near the TS2576 using short PC board traces Low ESR types capacitors are recommended for low output ripple voltage and good stability Generally low value or low voltage less than 12V electrolytic capacitors usually have higher ESR numbers For example the lower capacitor values 220uF 1000F will yield typically 50mV to 150mV of output ri
9. uld be well considered when selecting as inductor Feedback Connection For fixed output voltage version the FB feedback pin must be connected to Vour For the adjustable version it is important to place the output voltage ratio resistors near TS2576 as possible in order to minimize the noise introduction Enable Input It is required that the ENABLE must not be left open For normal operation connect this pin to a LOW voltage typically below 1 6V On the other hand for standby mode connect this pin with a HIGH voltage This pin can be safely pulled up to Tow without a resistor in series with it 2003 12 rev A Grounding To maintain output voltage stability the power ground connections must be low impedance For the 5 lead TO 220 and TO 263 style package both the tab and pin 3 are ground and rather connection may be used Thermal Characteristics The output ripple voltage is due mainly to the inductor sawtooth ripple current multiplied by the ESR of the output capacitor The output ripple voltage of a switching power supply will contain a sawtooth ripple voltage at the switcher frequency typically about 1 of the output voltages and may also contain short voltage spokes of the sawtooth waveform Due to the fast switching action and the parasitic inductance of the output filter capacitor there is voltage spikes presenting at the peaks of the sawtooth waveform Cautions must be taken for stray capac
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TSC TS2576 handbook