WT1117A

WEITRON 1.0A LOW DROPOUT PRECISION LINEAR REGULATORS P b Lead(Pb)-Free General Description: WT1117A WT1117A of positive adjustable and fixed regulators is designed to provide 1.0A output with low dropout voltage performance. On-chip trimming adjusts the reference voltage to 1.5%. For usage on working in post regulators or microprocessor power supplies, low voltage operation and fast transient response are required. WT1117A is available in surface-mount SOT-223 and TO-252 packages. Features: * Adjustable or Fixed Output * Output Current of 1.0A * Dropout Voltage(Typical) 1.15V @1.0A * Line Regulation 0.2% max. * Load Regulation 0.4% max. * Fast Transient Response * Current Limit Protection * Thermal Shutdown Protection Applications: * High Efficiency Linear Regulators * Post Regulators for Switching Supplies * Microprocessor Supply * Hard Drive Controllers * Battery Chargers * Adjustable Power Supply WEITRON hpp://www.weitron.com.tw 1/11 Rev-A 18-Oct-06 WT1117A Ordering Information Ordering Number Output Voltage WT1117AN-X WT1117AD-X WT1117AN-15 WT1117AD-15 WT1117AN-18 WT1117AD-18 WT1117AN-25 WT1117AD-25 WT1117AN-285 WT1117AD-285 WT1117AN-30 WT1117AD-30 WT1117AN-33 WT1117AD-33 WT1117AN-50 WT1117AD-50 Adj Adj 1.5 1.5 1.8 1.8 2.5 2.5 2.85 2.85 3.0 3.0 3.3 3.3 5.0 5.0 Package SOT-223 TO-252 SOT-223 TO-252 SOT-223 TO-252 SOT-223 TO-252 SOT-223 TO-252 SOT-223 TO-252 SOT-223 TO-252 SOT-223 TO-252 Shipping 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel 2,500 Units/Tape&Reel Marking Information & PIN Configurtions (Top View) TO-252 (DPAK) SOT-223 1117-VV YAWW YAWW 1117-VV VOUT ADJ/ GND* VIN VIN VOUT ADJ/GND* V V/VVV A Y WW = Output Voltage (50 = 5.0V, 285= 2.85V ,X = ADJ ) = Assembly Location = Year = Weekly On fixed versions Pin 1 = GND, on adjustable versions Pin 1 = A DJ Tab = VOUT http://www.weitron.com.tw WEITRON 2/11 Rev-A 18-Oct-06 WT1117A Typical Application (Adjustable Version) (Fixed Version) VOUT= 3.45V VIN> 4.75V 3 WT1117A-Adj 2 VOUT VIN ADJ VIN> 4.75V 3 WT1117A-3.3 VOUT 2 VIN GND VOUT= 3.3V + C 10μF Tant 1 R1 133 1.0% R2 232 1.0% R2 ) + IADJ X R2 R1 + C2 10μF Tant.Min + C1 10μF Tant 1 + C2 10μF Tant.Min VOUT= VREF X (1 + Notes: 1 . C 1 need e d i f devi c e i s f a r f r o m filt e r capacito r s 2 . C 2 minim u m val u e requir e d f o r stabili t y Block Diagram (Fixed Version) VIN Output Current Limit VOUT Thermal Shutdown Bandgap Reference + Error Amplifier GND (Adjustable Version) VIN Output Current Limit VOUT Thermal Shutdown Bandgap Reference + Error Amplifier ADJ http://www.weitron.com.tw WEITRON 3/11 Rev-A 18-Oct-06 WT1117A Parameter Power Dissipation Input Voltage Lead Temperature(Soldering, 10sec) Symbol PD V IN T LEAD TJ T STG Value Internally limited 7.0 300 -40 to 125 -40 to 150 -65 to + 150 UNIT W V °C °C °C Operating Junction Temperature Range Control Section Power Transistor Storage Temperature Range Thermal Characteristics SOT-223 Thermal Resistance, Junction-to-Case DPAK Thermal Resistance, Junction-to-Case R JC 15 6.0 °C / W http://www.weitron.com.tw WEITRON 4/11 Rev-A 18-Oct-06 WT1117A ELECTRICAL CHARACTERISTICS Typicals and limits appearing in normal type apply for Tj 25°C Parameter Reference Voltage WT1117A-Adj Symbol VREF 10mA Condition IOUT=10mA, VIN= 5V IOUT 1.0A, 2.65V VIN 7V IOUT=10mA, VIN=VOUT+1.5V VIN=VOUT+1.5V to 7 V 0 IOUT 1.0A ILoad =10mA, (1.5 V +VOUT) VOUT 7V Min 1.232 1.225 -1.5 -2 1.0 VIN 7V 60 Typ 1.250 1.250 0.04 Max 1.268 1.275 +1.5 +2 0.20 Unit V % % % Output Voltage - Line Regulation All REGLINE REGLOAD VD ICL IO MIN IQ IADJ Load Regulation Dropout Voltage Current Limit Minimum Load Current Ground Current Adjust Pin Current Temp. Coefficient Thermal Regulation Ripple Rejection (Note 1) All All All WT1117A-Adj All Fixed Versions WT1117A-Adj All All All VIN =VOUT + 1.5V ILoad =10mA to 1.0A 0.20 1.15 2 7 35 0.005 0.003 72 0.40 1.3 % IOUT=1.0A VIN-VOUT=1.5V VIN=5V, Vadj=0V VIN =VOUT + 1.5V ILoad =10mA to 1.0A ILoad=10mA, 2.65V V A mA mA μA %/°C %/W dB 7 13 90 VIN-VOUT=1.5V, ILoad=10mA TC RA TA=25℃, 30ms pulse VIN-VOUT=1.5V, ILoad=1.0A - Note 1: 120Hz input ripple (CADJ for ADJ =25μF) http://www.weitron.com.tw WEITRON 5/11 Rev-A 18-Oct-06 WT1117A Typical Performance Characteristics 1.00 0.10 TCASE = 0°C Output Voltage Deviation (%) 0.08 0.06 0.04 0.02 0.00 -0.02 -0.04 -0.06 -0.08 -0.10 -0.12 0 0.95 0.90 0.85 0.80 0.75 0 V DROPOUT TCASE = 25°C TCASE = 125°C 200 400 600 800 1000 10 20 30 40 50 60 70 80 90 100 110 120 130 TJ (°C) IOUT(mA) Fig.1 Dropout Voltage vs. Output Current 70 65 85 Fig.2 Reference Voltage vs. Temperature Adjust Pin Current(μA) IO = 10mA Ripple Rejection(dB) 75 65 55 45 60 55 50 45 40 0 10 TCASE = 25°C I = 1.0A 35 OUT (VIN-VOUT) = 3.0V VRIPPLE = 1.0VP-P 25 Cadj =0.1μF 15 20 30 40 50 60 70 80 90 100 110 120 130 Temperature (°C) 10 1 10 2 10 3 10 4 10 5 10 6 Frequency(Hz) Fig.3 Adjust Pin Current vs. Temperature 300 Load Step(mA) Voltage Deviation(mV) Fig.4 Ripple Rejection vs. Frequency 3.5 3.3 3.1 2.9 2.7 2.5 2.3 2.1 1.9 1.7 1 2 3 4 5 Tim(μS) 200 100 I SC (A) 0 -100 -200 VOUT = 3.3V COUT = CIN =22μF Tantalum CAdj =0.1μF 1000 500 0 0 6 7 8 9 10 1.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Fig.5 Transient Response VIN - VOUT(V) Fig.6 Short Circuit Current vs. VIN- VOUT http://www.weitron.com.tw WEITRON 6/11 Rev-A 18-Oct-06 WT1117A APPLICATION INFORMATION WT1117A linear regulators provide fixed and adjustable output voltages at currents up to 1.0A. These regulators are protected against overcurrent conditions and include thermal shutdown protection. The WT1117A's have a composite PNP-NPN output transistorand require an output capacitor for stability. A detailed procedure for selecting this capacitor follows. Adjustable Operation The WT1117A has an output voltage range of 1.25 V to 5.5 V. 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 current 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 35μA) also flows through R2 and adds a small error that should be taken into account if precise adjustment of VOUT is necessary. The output voltage is set according to the formula: V OUT = VREF X ( R1 + R2 ) + IAdj X R2 R1 The term IAdj R2 represents the error added by the adjust pin current. R1 is chosen so that the minimum load current is at least 2.0mA R1 and R2 should be the same type e.g. metal film for best tracking over temperature. While not required, a bypass capacitor from the adjust pin to ground will improve ripple rejection and transient response. A 0.1μF tantalum capacitor is recommended for first cut design. Type and value may be varied to obtainoptimum performance vs. price. WT1117A VIN C1 VIN VOUT Adj VREF IAdj CAdj R2 R1 C2 VOUT Figure1. Resistor Divider Scheme Stability Considerations The output compensation capacitor helps to determine three main characteristics of a linear regulator ’s performance: start-up delay,load transient response, and loop stability. The capacitor value and type is based on cost, availability, size and temperature constrains, A tantalum or aluminum electrolytic capacitor is preferred, as a film or ceramic capacitor with almost zero ESR can cause Instability. An aluminum electrolytic capacitor is the least expensive type. but when the circuit operates at low temperatures, both the value and ESR of the capacitor will vary widelt.For optimum performance over the full operating temperature range, a tantalum capacitor is best, A 22µF tantalum capacitor will work fine in most applications, but with high current regulators such as the W T1117A higher capacitance values will improve the transient response and stability. Most applications for the W T1117A’s involve large changes in load current, so the output capacitor must supply instantaneous load current. The ESR of the output capacitor causes an immediate drop in output voltage given by: V = I x ESR In microprocessor applications an output capacitor network of several tantalum and ceramic capacitors in parallel is commonly used. This reduces overall ESR and minimizes the instantaneous output voltage drop under transient load conditions. The output capacitor network should be placed as close to the load as possible for the best results. Used with large output capacitance values and theinput voltage is instantaneously shorted to ground, damage can occur. In this case, a diode connected as shown above in Figure1. http://www.weitron.com.tw WEITRON 7/11 Rev-A 18-Oct-06 WT1117A Protection Diodes When large external capacitors are used with most linear regulator, it is wise to add protection diodes. If the input voltage of the regulator is shorted, the output capacitor will discharge into the output of the regulator. The discharge current depends on the value of capacitor, output voltage, and rate at which VIN drops. Figure2 (a),(b) Protection Diode Scheme for Large Output Capacitors (a) Fixed Version IN4002 VIN VIN VOUT VOUT VIN VIN (b) Adjustable Version IN4002 VOUT VOUT WT1117A-Adj C2 C1 ADJ R1 CADJ C2 WT1117A-3.3 C1 GND R2 In the W T1117A linear regulators, the discharge path is through a large junction, and protection diodes are normally not needed. However, damage can occur if the regulator is used with large output capacitance values and the input voltage is instantaneously shorted to ground. In this case, a diode connected as shown above in Figure 2. Output Voltage Sensing The W T1117A are three terminal regulators. For which, they cannot provide true remote load sensing. Load regulation is limited by the resistance of the conductors connecting the regulator to the load. For best results the W T1117A should be connected are as shown in Figure 3. Figure3 (a),(b) Conductor Parasitic Resistance Effects are Minimized by this Grounding Scheme For Fixed and Adjustable Output Regulators VIN VIN VOUT RC Conductor Parasitic Resistance RLOAD VIN VIN VOUT RC R1 R2 Conductor Parasitic Resistance RLOAD WT1117A-3.3 GND (a) Fixed Version WT1117A-Adj ADJ (b) Adjustable Version Calculating Power Dissipation and Heat Sink Requirements The W T1117A precision linear regulators include thermal shutdown and current limit circuitry to protect the devices. However, high power regulators normally operate at high junction temperatures. It is important to calculate the power dissipation and junction temperatures accurately to be sure that you use and adequate heat sink. The case is connected to VOUT on the W T1117A, and electrical isolation may be required for some applications. Thermal compound should always be used with high current regulators like the W T1117A. WEITRON http://www.weitron.com.tw 8/11 Rev-A 18-Oct-06 WT1117A The thermal characteristics of an IC depend four factors: 1. Maximum Ambient Temperature TA(°C) 2. Power Dissipation PD ( Watts) 3. Maximum Junction Junction Temperature TJ(°C) 4. Thermal Resistance Junction to ambient RθJA(°C/W ) The relationship of these four factors is expressed by equation (1): TJ=TA + PD X RθJA ........(1) Maximum ambient temperature and power dissipation are determined by the design while the maximum junction temperature and thermal resistance depend on the manufacturer and the package type. The maximum power dissipation for a regulator is expressed by equation (2): PD(max) = { VIN(max)- VOUT(min) } IOUT(max) + VIN(max)IQ ........(2) where: VIN(max) is the maximum input voltage, VOUT(min) is the minimum output voltage, IOUT(max) is the maximum output current IQ is the maximum quiescent current at IOUT(max) . A heat sink effectively increases the surface area of the package to improve the flow of heat away from the IC into the air. Each material in the heat flow path between the IC and the environment has a thermal resistance. Like series electrical resistances, these resistance are summed to determine RθJA the total thermal resistance between the junction and the air. This is expressed by equation (3): RθJA=RθJC + RθCS X RθSA........(3) Where all of the following are in °C/W RθJC is thermal resistance of junction to case, RθCS is thermal resistance of case to heat sink, RθSA is thermal resistance of heat sink to ambient air The value for RθJA is calculated using equation (3) and the result can be substituted in equation (1) .The value for RθJC is 3.5°C/W for a given package type based on an average die size. For a high current regulator such as the W T1117A the majority of the heat is generated in the power transistor section. http://www.weitron.com.tw WEITRON 9/11 Rev-A 18-Oct-06 WT1117A TO-252-3 PACKAGE OUTLINE DIMENSIONS 6.50 0.10 5.30 0.10 1.40 0.10 2.30 0.10 0.51 0.005 5.50 0.10 9.50 0.25 1.00 0.10 0.80 0.05 2.30 0.05 4.60 0.10 0.60 0.05 1.20 0.25 0.51 0.05 Unit: mm SOT-223 PACKAGE OUTLINE DIMENSIONS 6.50 0.20 3.00 0.10 0.325 0.005 7.00 0.15 3.50 0.15 1.75TYP 0~10 2.30 0.05 4.60 0.10 0.73 0.05 1.60 0.05 0.06 0.04 Unit: mm http://www.weitron.com.tw WEITRON 10/11 Rev-A 18-Oct-06 WT1117A ORDERING NUMBER WT1117 A X - XX Output Voltage - X : Adj - 15 : 1.5V - 18 : 1.8V - 25 : 2.5V - 285 : 2.85V - 30 : 3.0V - 33 : 3.3V - 50 : 5.0V Circuit Type Output Current = 1.0A Package N : SOT-223 D : TO-252 http://www.weitron.com.tw WEITRON 11/11 Rev-A 18-Oct-06