AMC DOC. #:AMC2576_B November 2002 AMC2576 ADD MICROTECH CORP. 3A STEP DOWN VOLTAGE REGULATOR DESCRIPTION FEATURES The AMC2576 series is a step-down switching regulator with all the 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 AMC2576 series offers a high-efficiency replacement for popular three-terminal linear regulators. It requires only a minimum number of external components. Substantially, it reduces not only the area of board size but also the size of the heat sink. In some cases, no heat sink is required. The 4% tolerance on output voltage within specified input voltages and output load conditions is guaranteed. The oscillator frequency accuracy is within 10%. External shutdown is included, featuring 70A(typical) standby current. The output switch includes cycle-by-cycle current limitation, as well as thermal shutdown for full protection under fault conditions. ! ! ! ! ! # # # # Guaranteed 3A output current 3.3V, 5V and adjustable output versions Wide input voltage range, up to 40V Internal oscillator of 52 KHz fixed frequency Wide adjustable version output voltage range, from 1.23V to 37V 4% max over line and load conditions Low standby current, typ. 70A, at shutdown mode Requires only 4 external components Thermal shut down and current limit protection P+ Product enhancement tested APPLICATIONS PACKAGE PIN OUT LCD Monitors ADD-ON Cards Switching Regulators High Efficiency Step-Down Regulators Efficient Pre-regulator for Linear Regulators ! ! ! ! $ 5. Enable 4. FB 3. GND 2. VOUT 1. VIN 5-Pin Plastic TO-220 (Top View) 5. Enable 4. FB 3. GND 2. VOUT 1. VIN Voltage Options: AMC2576-3.3 - 3.3V Fixed AMC2576-5.0 - 5.0V Fixed AMC2576-ADJ - Adjustable Output (Side View) 5-Pin Plastic TO-220B 5. Enable 4. FB 3. GND 2. VOUT 1. VIN 5-Pin Plastic TO-263 Surface Mount (Top View) Temperature Range -40C TJ 125C P ORDER INFORMATION Plastic TO-220B Plastic TO-220 5-pin AMC2576-ADJP AMC2576-X.XP PB 5-pin AMC2576-ADJPB AMC2576-X.XPB Note: All surface-mount packages are available in Tape & Reel. AMC2576-X.XDDT). Copyright 2002, ADD Microtech Corp. 1 DD Plastic TO-263 5-pin AMC2576-ADJDD AMC2576-X.XDD Append the letter "T" to part number (i.e. www.addmtek.com AMC2576 AMC DOC. #: AMC2576_B November 2002 3A STEP-DOWN VOLTAGE REGULATOR TYPICAL APPLICATION AMC2576-X.X 4 FB 1 VIN 7V - 40V DC INPUT GND CIN 100F 3 Figure 1. VOUT ENABLE 2 OUTPUT L1 100H 5 COUT 1000F Fixed Output Voltage Versions AMC2576-ADJ FB 4 1 V IN 7V - 40V DC INPUT OUTPUT VOUT 2 GND CIN 100F Figure 2. 3 L1 100H ENABLE 5 R2 COUT 1000F R1 Adjustable Output Voltage Versions VOUT = VREF R2 = R1 (1+ ( VV OUT REF R2 R1 -1 ) ) Where VREF = 1.23V, R1 between 1K and 5K Copyright 2002, ADD Microtech Corp. 2 www.addmtek.com AMC2576 AMC DOC. #: AMC2576_B November 2002 3A STEP-DOWN VOLTAGE REGULATOR ABSOLUTE MAXIMUM RATINGS (Note 1) 45V Input Voltage, VIN -0.3V V VIN ENABLE Pin Input Voltage 150C Operating Junction Temperature, TJ Storage Temperature Range -65C to 150C Lead Temperature (soldiering, 10 seconds) 260C Note 1: Exceeding these ratings could cause damage to the device. All voltages are with respect to Ground. Currents are positive into, negative out of the specified terminal. RECOMMENDED OPERATING RATINGS -40C TJ 125C 40V(Max.) Temperature Range Input Voltage, VIN THERMAL DATA P,PB, DD PACKAGE: Thermal Resistance-Junction to Tab, JT Thermal Resistance-Junction to Ambient, JA 3.0C /W 45C /W Junction Temperature Calculation: TJ = TA + (PD x JA). The JA numbers are guidelines for the thermal performance of the device/pc-board system. All of the above assume no ambient airflow. BLOCK DIAGRAM VIN FB 1 4 R2* 3 Regulator With Enable 5 ENABLE 2 VOUT Comparator Driver Error Amplifier R1* GND Thermal Shutdown & Current Limit 52KHz Oscillator 1.23V Reference VOUT = 3.3V VOUT = 5.0V VOUT = Adjustable Copyright 2002, ADD Microtech Corp. Reset : R2/R1 = 1.7 : R2/R1 = 3.1 : R2 = 0 R1 = Open 3 www.addmtek.com AMC2576 AMC DOC. #: AMC2576_B November 2002 3A STEP-DOWN VOLTAGE REGULATOR DC ELECTRICAL CHARACTERISTICS Unless otherwise specified, these specifications apply VIN = 12V, ILOAD = 0.5A and the operating ambient temperatures TJ = 25C. Parameter Output Voltage (Note 1) Output Voltage (Note 1) Output Voltage (Note 1) Feedback Voltage (Note 1) Feedback Voltage (Note 1) Feedback Voltage (Note 1) Symbol AMC2576 Units Min Typ Max 3.234 3.300 3.366 6V VIN 40V 4.900 3.168 5.000 3.300 5.100 3.432 8V VIN 40V 4.800 5.000 5.200 0.5A ILOAD 3A, 6V VIN 40V 3.135 3.300 3.482 Test circuit of Figure 1 8V VIN 40V 4.750 5.000 5.250 AMC2576-ADJ VOUTFB Test circuit of Figure 2 VOUT = 5V 1.217 1.230 1.243 V VIN 40V, VOUT = 5V, AMC2576-ADJ VOUTFB 8V Test circuit of Figure 2 0.5A ILOAD 3A 1.193 1.230 1.267 V VIN 40V, VOUT = 5V, AMC2576-ADJ VOUTFB 8V Test circuit of Figure 2 0.5A ILOAD 3A, 1.180 -40C TJ 125C 1.230 1.286 V AMC2576-3.3 AMC2576-5.0 AMC2576-3.3 AMC2576-5.0 AMC2576-3.3 AMC2576-5.0 VOUT Test circuit of Figure 1 0.5A I 3A LOAD VOUT Test circuit of Figure 1 VOUT -40C TJ 125C AMC2576-3.3 Efficiency Test Conditions V % 77 ILOAD = 3A, VOUT = 5V AMC2576-ADJ 77 (Note 3) 52 52 5 58 63 10 Standby Current ISTBY ENABLE = 5V 70 200 Saturation Voltage VSAT ILOAD = 3A (Note 4) 1.4 1.8 50 2.0 100 500 98 7 7.2 0.3 9 1.4 8.8 9 2 20 Oscillator Frequency Quiescent Current fOSC (Note 2) IQ Feedback Bias Current IFB VOUT = 5V (ADJ version only) Duty Cycle (ON) DC (Note 5) Current Limit ILIMIT (Note 2, 4) Output Leakage Current ILEAK (Note 3) VIH VOUT = 0V VIL VOUT = Normal Output Voltage IIH IIL ENABLE Threshold Voltage ENABLE Input Current Copyright 2002, ADD Microtech Corp. V 75 ILOAD = 3A AMC2576-5.0 V TJ = 25C -40 C TJ 125C O 47 42 TJ = 25C -40C TJ 125C TJ = 25C -40C TJ 125C TJ = 25C -40C TJ 125C VOUT = 0V VOUT = -1V TJ = 25C -40C TJ 125C TJ = 25C -40C TJ 125C 93 4.2 3.5 2.2 2.4 mA A V nA % 1.2 1.0 0.8 ENABLE = 5V 12 30 ENABLE = 0V 0 10 4 kHz A mA V A www.addmtek.com AMC DOC. #: AMC2576_B November 2002 AMC2576 3A STEP-DOWN VOLTAGE REGULATOR 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 VOUT and connected to +12V to force the output transistor OFF. Note 4: VOUT pin sourcing current. No diode, inductor or capacitor connect to VOUT. Note 5: FB is removed from VOUT and connected to 0V. Copyright 2002, ADD Microtech Corp. 5 www.addmtek.com AMC2576 AMC DOC. #: AMC2576_B November 2002 3A STEP-DOWN VOLTAGE REGULATOR CHARACTERIZATION CURVES Test circuits of Figure 1 and 2, TJ =25C, unless otherwise specified. Output voltage vs. temperature 5.00 5.10 5.08 5.06 5.04 5.02 5.00 4.98 4.96 4.94 4.92 4.90 4.88 4.86 4.84 4.82 4.80 VOUT=5V VIN = 12V, VOUT = 5V ILOAD = 0.5A 4.98 ILOAD=0.5A VOUT(V) VOUT(V) Line regulation ILOAD=3A 4.96 4.94 4.92 4.90 0 5 10 15 20 25 30 35 -40 40 -20 0 20 VIN(V) VOUT = 5V VIN = 25V Quiescent Current (mA) Current Limit (A) 100 120 30.0 8.60 8.20 8.00 7.80 7.60 7.40 25.0 20.0 15.0 ILOAD=3A 10.0 5.0 7.20 7.00 ILOAD=200mA 0.0 -40 -20 0 20 40 60 80 0 100 120 10 20 30 40 Input Voltage(V) TJ (C) Dropout voltage vs. temperature Standby current vs. temperature 2.10 180 160 ILOAD=3A 1.80 140 1.50 Standby current (A) Dropout Voltage (V) 80 Quiescent current vs. input voltage Current limit vs. temperature 8.40 40 60 TJ (C) 1.20 0.90 ILOAD=0. 5A 0.60 0.30 VIN =40V 120 100 80 60 VIN =12V 40 20 0.00 0 -40 -20 0 20 40 60 -40 80 100 120 TJ (C) Copyright 2002, ADD Microtech Corp. -20 0 20 40 60 80 100 120 TJ (C) 6 www.addmtek.com AMC2576 AMC DOC. #: AMC2576_B November 2002 3A STEP-DOWN VOLTAGE REGULATOR CHARACTERIZATION CURVES (continued) Test circuits of Figure 1 and 2, TJ =25C, unless otherwise specified. Load transient response Saturation voltage vs. load current 1.60 1.40 ILOAD (A) 1.20 TJ = 25C 1.00 0.80 VOUT 100mV/ Div 5V TJ =125C 0.60 3A 1A/ Div 0.40 0.20 0.00 0 0.5 1 1.5 2 2.5 3 ILOAD 0.5A Saturation voltage (V) Copyright 2002, ADD Microtech Corp. Time:100s/ Div 7 www.addmtek.com AMC2576 AMC DOC. #: AMC2576_B November 2002 3A STEP-DOWN VOLTAGE REGULATOR Application Information Input Capacitors (CIN) It is required that VIN must be bypassed with at least a 100F electrolytic capacitor for stability. Also, it is strongly recommended the capacitor's leads must be dept short, and located near the regulator as possible. For low operating temperature range, for example, below -25C, 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 age. Paralleling a ceramic or solid tantalum capacitor will increase the regulator stability at cold temperatures. Output Capacitors (COUT) An output capacitor is also required to filter the output voltage and is needed for loop stability. The capacitor should be located near the AMC2576 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 (220F-1000F) will yield typically 50 mV to 150 mV of output ripple voltage, while larger-value capacitors will reduce the ripple to approximately 20 mV to 50 mV. 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 (IIND). Output Ripple Voltage = (IIND) x (ESR of COUT) Some capacitors called "high-frequency," "low-inductance," or "low-ESR." are recommended to use to further reduce the output ripple voltage to 10 mV or 20 mV. However, very low ESR capacitors, such as Tantalum capacitors, should be carefully evaluated. Catch Diode This diode is required to provide a return path for the inductor current when the switch is off. It should be located close to the AMC2576 using short leads and short printed circuit traces as possible. To satisfy the need of 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). Besides, 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 a better choice. Copyright 2002, ADD Microtech Corp. 8 www.addmtek.com AMC2576 AMC DOC. #: AMC2576_B November 2002 3A STEP-DOWN VOLTAGE REGULATOR Application Information (contd.) Output Voltage Ripple and Transients The output ripple voltage is due mainly to the inductor sawtooth ripple current multiplied by the ESR of the output capacitor. The output voltage of a switching power supply will contain a sawtooth ripple voltage at the switcher frequency, typically about 1% of the output voltage, and may also contain short voltage spikes at the peaks 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 capacitance, 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 (20H & 100F) (as shown in Figure 3) will possibly provide a 10X reduction in output ripple voltage and transients. AMC2576-ADJ FB 4 7V - 40V DC INPUT L2 20H 1 V IN CIN 100F GND 3 VOUT 2 ENABLE 5 L1 100H COUT 1000F R2 50K R1 1.21K OUTPUT C1 100F Figure 3. LC Filter for Low Output Ripple Inductor Selection The AMC2576 can be used for either continuous or discontinuous modes of operation. Each mode has distinctively different operating characteristics, which can affect the 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 forced to the discontinuous mode (inductor current falls to zero for a period of time). For light loads (less than approximately 300 mA) it may be desirable to operate the regulator in the discontinuous mode, primarily because of the lower inductor values required for the discontinuous mode. Inductors 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 voltages 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 should be well considered when selecting as inductor. Copyright 2002, ADD Microtech Corp. 9 www.addmtek.com AMC DOC. #: AMC2576_B November 2002 AMC2576 3A STEP-DOWN VOLTAGE REGULATOR Application Information (contd.) Feedback Connection For fixed output voltage version, the FB (feedback) pin must be connected to VOUT. For the adjustable version, it is important to place the output voltage ratio resistors near AMC2576 as possible in order to minimize the noise introduction. ENABLE 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 +VIN without a resistor in series with it. 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 either connection may be used. Heat Sink and Thermal Consideration Although the AMC2576 requires only a small heat sink for most cases, the following thermal consideration is important for all operation. With the package thermal resistances JA and JC, total power dissipation can be estimated as follows: PD = (VIN x IQ)+(VOUT / VIN)(ILOAD x VSAT); When no heat sink is used, the junction temperature rise can be determined by the following: TJ = PD x JA; With the ambient temperature, the actual junction temperature will be: TJ = TJ +TA ; If the actual operating junction temperature is out of the safe operating junction temperature (typically 125C), then a heat sink is required. When using a heat sink, the junction temperature rise will be reduced by the following: TJ = PD x (JC + interface + Heat sink); As one can see from the above, it is important to choose an heat sink with adequate size and thermal resistance, such that to maintain the regulator's junction temperature below the maximum operating temperature. Copyright 2002, ADD Microtech Corp. 10 www.addmtek.com AMC2576 AMC DOC. #: AMC2576_B November 2002 3A STEP-DOWN VOLTAGE REGULATOR 5-Pin Plastic TO-220 (P) S B INCHES C T F A K D MILLIMETERS MIN TYP MAX MIN TYP MAX A 0.560 - 0.650 14.23 - 16.51 B 0.380 - 0.420 9.66 - 10.66 C 0.140 - 0.190 3.56 - 4.82 D 0.018 - 0.035 0.46 - 0.89 F 0.140 - 0.160 3.56 - 4.06 G 0.134 - - 3.40 - - J 0.012 - 0.045 0.31 - 1.14 K 0.500 - 0.580 12.70 - 14.73 N 0.268 TYP 6.80 TYP R 0.080 - 0.115 2.04 - 2.92 S 0.045 - 0.055 1.14 - 1.39 T 0.230 - 0.270 5.85 - 6.85 R G N J 5-Pin Surface Mount TO-263 (DD) INCHES C A MIN TYP MAX MIN TYP MAX A 0.395 - 0.420 10.03 - 10.67 B 0.325 - 0.361 8.25 - 9.17 C 0.171 - 0.181 4.34 - 4.59 D 0.045 - 0.055 1.14 - 1.40 E 0.013 - 0.017 0.330 - 0.432 F 0.029 - 0.035 0.737 - 0.889 G 0.062 - 0.072 1.57 - 1.83 I - - 0.065 - - 1.65 K 0.575 0.635 14.60 16.13 L 0.090 0.110 2.29 2.79 D I B K MILLIMETERS N M L F E G Copyright 2002, ADD Microtech Corp. 11 M 7 7 N 3 3 www.addmtek.com AMC2576 AMC DOC. #: AMC2576_B November 2002 3A STEP-DOWN VOLTAGE REGULATOR 5-Pin Plastic TO-220B (PB) INCHES G A MILLIMETERS MIN TYP MAX MIN TYP MAX A 0.380 0.401 0.420 9.65 10.20 10.65 I B 0.248 6.30 c 0.348 0.358 0.368 8.85 9.10 9.35 B f z1 f1 M c c1 d1 z4 H J z2 c1 0.167 4.25 d1 0.138 3.50 d2 0.154 3.90 d3 0.213 5.40 e1 0.134 3.40 e2 0.268 6.80 e3 0.032 0.81 f 0.151 3.84 f1 0.039 1.00 G 0.048 0.05 0.052 1.22 1.27 1.32 z3 H K d3 0.996 25.30 I 0.175 0.180 0.185 4.44 4.57 4.70 d2 J 0.965 24.50 K 0.105 2.67 L 0.164 0.173 0.182 4.17 4.40 4.63 e1 N L e2 O M 0.05 1.27 N 0.013 0.015 0.025 0.33 0.381 0.63 O 0.322 0.331 0.340 8.17 8.40 8.63 z5 z1 7 7 z2 7 7 z3 7 7 z4 5 5 Z5 5 5 e3 Copyright 2002, ADD Microtech Corp. 12 www.addmtek.com AMC DOC. #: AMC2576_B November 2002 AMC2576 3A STEP-DOWN VOLTAGE REGULATOR IMPORTANT NOTICE ADD Microtech (ADDM) reserves the right to make changes to its products or to discontinue any integrated circuit product or service without notice, and advises its customers to obtain the latest version of relevant information to verify, before placing orders, that the information being relied on is current. A few applications using integrated circuit products may involve potential risks of death, personal injury, or severe property or environmental damage. ADDM integrated circuit products are not designed, intended, authorized, or warranted to be suitable for use in life-support applications, devices or systems or other critical applications. Use of ADDM products in such applications is understood to be fully at the risk of the customer. In order to minimize risks associated with the customer's applications, the customer should provide adequate design and operating safeguards. ADDM assumes to no liability to customer product design or application support. ADDM warrants the performance of its products to the specifications applicable at the time of sale. U.S. Asia Pacific region ADD Microtech Inc. 492 Altamont Drive Milpitas, CA 95035 ADD Microtech Corp 3F, 132, Sec. 4, Chung Hsiao E. Rd., Taipei, Taiwan T E L : (408) 9410420 FA X : (408) 9410864 T E L : 2-27760166 FA X : 2-27764208 Copyright 2002, ADD Microtech Corp. 13 www.addmtek.com