SG3524

SG1524/SG2524/SG3524 REGULATING PULSE WIDTH MODULATOR DESCRIPTION This monolithic integrated circuit contains all the control circuitry for a regulating power supply inverter or switching regulator. Included in a 16pin dual-in-line package is the voltage reference, error amplifier, oscillator, pulse width modulator, pulse steering flip-flop, dual alternating output switches and current limiting and shut-down circuitry. This device can be used for switching regulators of either polarity, transformer coupled DC to DC converters, transformerless voltage doublers and polarity converters, as well as other power applications. The SG1524 is specified for operation over the full military ambient temperature range of -55°C to +125°C, the SG2524 for -25°C to +85°C, and the SG3524 is designed for commercial applications of 0°C to +70°C. FEATURES • • • • • • • • • • • 8V to 40V operation 5V reference Reference line and load regulation of 0.4% Reference temperature coefficient < ± 1% 100Hz to 300KHz oscillator range Excellent external sync capability Dual 50mA output transistors Current limit circuitry Complete PWM power control circuitry Single ended or push-pull outputs Total supply current less than 10mA HIGH RELIABILITY FEATURES - SG1524 ♦ Available to MIL-STD-883B and DESC SMD ♦ MIL-M-38510/12601BEA - JAN1524J ♦ Radiation data available ♦ LMI level "S" processing available BLOCK DIAGRAM Rev 1.1a 03/18/2005 Copyright © 1994 1 11861 Western Avenue ∞ Garden Grove, CA 92841 (714) 898-8121 ∞ FAX: (714) 893-2570 Microsemi. Inc. ABSOLUTE MAXIMUM RATINGS (Note 1) Input Voltage (+VIN ) ............................................................. 42V Collector Voltage ................................................................ 40V Logic Inputs ........................................................... -0.3V to 5.5V Current Limit Sense Inputs ................................... -0.3V to 0.3V Output Current (each transistor) .................................... 100mA Reference Load Current .................................................. 50mA Note 1. Values beyond which damage may occur. Oscillator Charging Current ................................................ 5mA Operating Junction Temperature Hermetic (J, L Packages) ............................................. 150°C Plastic (N, D Packages) ............................................... 150°C Storage Temperature Range ............................. -65°C to 150°C Pb-free / RoHS Peak Package Solder Reflow Temp (40 sec. max. exposure)... 260°C (+0, -5) Lead Temperature (Soldering, 10 seconds).................................300°C THERMAL DATA J Package: Thermal Resistance-Junction to Case, θ JC .................. 30°C/W Thermal Resistance-Junction to Ambient, θ JA .............. 80°C/W N Package: Thermal Resistance-Junction to Case, θ JC .................. 40°C/W Thermal Resistance-Junction to Ambient, θ JA ............. 65°C/W D Package: Thermal Resistance-Junction to Case, θ JC ................... 50°C/W Thermal Resistance-Junction to Ambient, θ JA ............ 120°C/W L Package: Thermal Resistance-Junction to Case, θ JC .................. 35°C/W Thermal Resistance-Junction to Ambient, θ JA ........... 120°C/W Note A. Junction Temperature Calculation: TJ = TA + (PD x θJA). Note B. The above numbers for θ JC are maximums for the limiting thermal resistance of the package in a standard mounting configuration. The θ JA numbers are meant to be guidelines for the thermal performance of the device/pcboard system. All of the above assume no ambient airflow. RECOMMENDED OPERATING CONDITIONS (Note 2) Input Voltage (+VIN) ................................................... 8V to 40V Collector Voltage ....................................................... 0V to 40V Error Amp Common Mode Range ..........................1.8V to 3.4V Current Limit Sense Common Mode Range ........ -0.3V to 0.3V Output Current (each transistor) ............................... 0 to 50mA Reference Load Current ........................................... 0 to 20mA Oscillator Charging Current .................................. 30µ A to 2mA Oscillator Frequency Range ......................... 100Hz to 300KHz Oscillator Timing Resistor (RT) ........................ 1.8KΩ to 100KΩ Oscillator Timing Capacitor (CT) ............................ 1nF to 1.0 µF Operating Ambient Temperature Range SG1524 ......................................................... -55°C to 125°C SG2524 ........................................................... -25°C to 85°C SG3524 ............................................................... 0°C to 70 °C Note 2: Range over which the device is functional and parameter limits are guaranteed. ELECTRICAL CHARACTERISTICS (Unless otherwise specified, these specifications apply over the operating ambient temperatures for SG1524 with -55 ° C ≤ TA ≤ 125° C, SG2524 with -25°C ≤ TA ≤ 85°C, SG3524 with 0° C ≤ TA ≤ 70°C, and +V IN = 20V. Low duty cycle pulse testing techniques are used which maintains junction and case temperatures equal to the ambient temperature.) Parameter Reference Section (Note 3) Output Voltage Line Regulation Load Regulation Temperature Stability (Note 7) Total Output Voltage Range (Note 7) Short Circuit Current Note 3. IL = 0mA Test Conditions TJ = 25°C VIN = 8V to 40V IL = 0 to 20mA Over Operating Temperature Range Over Line, Load and Temperature VREF = 0V SG1524/2524 SG3524 Units Min. Typ. Max. Min. Typ. Max. 4.80 5.00 5.20 4.60 5.00 5.40 20 30 50 50 50 50 4.80 5.20 4.60 5.40 25 50 150 25 50 150 V mV mV mV V mA Rev 1.1a Copyright © 1994 2 11861 Western Avenue ∞ Garden Grove, CA 92841 (714) 898-8121 ∞ FAX: (714) 893-2570 ELECTRICAL CHARACTERISTICS Parameter Oscillator Section (Note 4) Initial Accuracy Voltage Stability Maximum Frequency Sawtooth Peak Voltage Sawtooth Valley Voltage Clock Amplitude Clock Pulse Width Error Amplifier Section (Note 5) Input Offset Voltage Input Bias Current Input Offset Current DC Open Loop Gain Output Low Level Output High Level Common Mode Rejection Supply Voltage Rejection Gain-Bandwidth Product (Note 7) P.W.M. Comparator (Note 4) Minimum Duty Cycle Maximum Duty Cycle (continued) Test Conditions TJ = 25°C MIN ≤ TJ ≤ MAX VIN = 8V to 40V RT = 2KΩ, CT = 1nF VIN = 40V VIN = 8V SG1524/2524 SG3524 Units Min. Typ. Max. Min. Typ. Max. 36 34 200 3 0.6 3.2 0.3 40 0.1 400 1 44 46 1 3.8 1.2 1.5 0.5 1 72 3.8 70 55 1 0.2 4.2 0.5 3.8 5 10 1 60 0.2 4.2 0.5 36 34 200 3 0.6 3.2 0.3 40 0.1 400 1 44 46 1 3.8 1.2 1.5 2 1 10 10 2 KHz KHz % KHz V V V µs mV µA µA dB V V dB dB MHz % % mV µA V V µA V V µs µs mA RS ≤ 2KΩ RL ≥10MΩ, TJ = 25°C VPIN 1 - VPIN 2 ≥ 150mV VPIN 2 - VPIN 1 ≥150mV VCM = 1.8V to 3.4V VIN = 8V to 40V TJ = 25°C VCOMP = 0.5V VCOMP = 3.6V 2 0 1 2 0 45 190 49 200 210 200 1.2 1.8 50 2 45 180 49 200 220 200 1.2 1.8 50 2 Current Limit Amplifier Section (Note 6) TJ = 25°C Sense Voltage Input Bias Current Shutdown Section Threshold Voltage TJ = 25°C MIN ≤ TJ ≤ MAX Output Section (each transistor) Collector Leakage Current VCE = 40V Collector Saturation Voltage IC = 50mA Emitter Output Voltage IE = 50mA RC = 2KΩ Collector Voltage Rise Time Collector Voltage Fall Time RC = 2KΩ Power Consumption Standby Current VIN = 40V Note Note Note Note 4. 5. 6. 7. 0.5 0.2 0.8 0.5 0.2 0.8 17 0.4 0.2 7 10 17 0.4 0.2 7 10 FOSC = 40KHz (R T = 2.9KΩ, CT = .01µF) VCM = 2.5V VCM = 0V These parameters, although guaranteed over the recommended operating conditions, are not 100% tested in production. Rev 1.1a Copyright © 1994 3 11861 Western Avenue ∞ Garden Grove, CA 92841 (714) 898-8121 ∞ FAX: (714) 893-2570 APPLICATION NOTES OSCILLATOR The oscillator in the SG1524 uses an external resistor RT to establish a constant charging current into an external capacitor CT. While this uses more current than a series-connected RC, it provides a linear ramp voltage at CT which is used as a timedependent reference for the PWM comparator. The charging current is equal to 3.6V/RT, and should be restricted to between 30µA and 2mA. The equivalent range for RT is 1.8K to 100K. The range of values for CT also has limits, as the discharge time of CT determines the pulse width of the oscillator output pulse. The pulse is used (among other things) as a blanking pulse to both outputs to insure that there is no possibility of having both outputs on simultaneously during transitions. This output deadtime relationship is shown in Figure 1. A pulse width below 0.35 microseconds may cause failure of the internal flip-flop to toggle. This restricts the minimum value of CT to 1000pF. (Note: Although the oscillator output is a convenient oscilloscope sync input, the probe capacitance will increase the pulse width and decrease the oscillator frequency slightly.) Obviously, the upper limit to the pulse width is determined by the modulation range required in the power supply at the chosen switching frequency. Practical values of CT fall between 1000pF and 0.1µ F, although successful 120 Hz oscillators have been implemented with values up to 5µF and a series surge limit resistor of 100 ohms. The oscillator frequency is approximately 1/RT •CT; where R is in ohms, C is in microfarads, and the frequency is in Megahertz. For greater accuracy, the chart in Figure 2 may be used for a wide range of operating frequencies. Note that for buck regulator topologies, the two outputs can be wire-ORed for an effective 0-90% duty cycle range. With this connection, the output frequency is the same as the oscillator frequency. For push-pull applications, the outputs are used separately; the flip-flop limits the duty cycle range at each output to 0-45%, and the effective switching frequency at the transformer is 1/2 the oscillator frequency. If it is desired to synchronize the SG1524 to an external clock, a positive pulse may be applied to the clock pin. The oscillator should be programmed with RT and CT values that cause it to freerun at 90% of the external sync frequency. A sync pulse with a maximum logic 0 of +0.3 volts and a minimum logic 1 of +2.4 volts applied to Pin 3 will lock the oscillator to the external source. The minimum sync pulsewidth should be 200 nanoseconds, and the maximum is determined by the required deadtime. The clock pin should never be driven more negative than -0.3 volts, nor more positive than +5.0 volts. The nominal resistance to ground is 3.2K at the clock pin, ±25% over temperature. If two or more SG1524s must be synchronized together, program one master unit with RT and CT for the desired frequency. Leave the RT pins on the slaves open, connect the C T pins to the CT of the master, and connect the clock pins to the clock pin of the master. Since CT is a high-impedance node, this sync technique works best when all devices are close together. FIGURE 1 - OUTPUT STAGE DEADTIME VS. CT FIGURE 2 - OSCILLATOR FREQUENCY VS. RT AND CT Rev 1.1a Copyright © 1994 4 11861 Western Avenue ∞ Garden Grove, CA 92841 (714) 898-8121 ∞ FAX: (714) 893-2570 APPLICATION NOTES (continued) CURRENT LIMITING The current limiting circuitry of the SG1524 is shown in Figure 3. By matching the base-emitter voltages of Q1 and Q2, and assuming a negligible voltage drop across R1: C.L. Threshold = VBE(Q1) + I1• R2 - VBE(Q2) = I1• R 2 ~ 200 mV Although this circuit provides a relatively small threshold with a negligible temperature coefficient, there are some limitations to its use because of its simplicity. The most important of these is the limited common-mode voltage range: ±0.3 volts around ground. This requires sensing in the ground or return line of the power supply. Also precautions should be taken to not turn on the parasitic substrate diode of the integrated circuit, even under transient conditions. A Schottky clamp diode at Pin 5 may be required in some configurations to achieve this. A second factor to consider is that the response time is relatively slow. The current limit amplifier is internally compensated by R1 , C1 , and Q1, resulting in a roll-off pole at approximately 300 Hz. A third factor to consider is the bias current of the C.L. Sense pins. A constant current of approximately 150µ A flows out of Pin 4, and a variable current with a range of 0-150µA flows out of Pin 5. As a result, the equivalent source impedance seen by the current sense pins should be less than 50 ohms to keep the threshold error less than 5%. Since the gain of this circuit is relatively low (42 dB), there is a transition region as the current limit amplifier takes over pulse width control from the error amplifier. For testing purposes, threshold is defined as the input voltage required to get 25% duty cycle (+2 volts at the error amplifier output) with the error amplifier signaling maximum duty cycle. APPLICATION NOTE: If the current limit function is not used on the SG1524, the common-mode voltage range restriction requires both current sense pins to be grounded. FIGURE 3 - CURRENT LIMITING CIRCUITRY OF THE SG1524 In this conventional single-ended regulator circuit, the two outputs of the SG1524 are connected in parallel for effective 0 - 90% duty-cycle modulation. The use of an output inductor requires and R-C phase compensation network for loop stability. Push-pull outputs are used in this transformer-coupled DC-DC regulating converter. Note that the oscillator must be set at twice the desired output frequency as the SG1524's internal flip-flop divides the frequency by 2 as it switches the P.W.M. signal from one output to the other. Current limiting is done here in the primary so that the pulse width will be reduced should transformer saturation occur. Rev 1.1a Copyright © 1994 5 11861 Western Avenue ∞ Garden Grove, CA 92841 (714) 898-8121 ∞ FAX: (714) 893-2570 CONNECTION DIAGRAMS & ORDERING INFORMATION Package 16-PIN CERAMIC DIP J - PACKAGE (See Notes Below) Part No. SG1524J/883B JAN1524J SG1524J/DESC SG1524J SG2524J SG3524J SG2524N SG3524N SG2524D SG3524D Ambient Temperature Range -55°C to 125°C -55°C to 125°C -55°C to 125°C -55°C to 125°C -25°C to 85°C 0°C to 70° C -25°C to 85°C 0°C to 70° C -25°C to 85°C 0°C to 70° C Connection Diagram INV. INPUT N.I. INPUT OSC. OUTPUT +C.L. SENSE -C.L. SENSE RT CT GROUND 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 16-PIN PLASTIC DIP N - PACKAGE 16-PIN NARROW BODY PLASTIC S.O.I.C. D - PACKAGE RoHS / Pb-free transition DC:0440 VREF +VIN EB CB CA EA SHUTDOWN COMPENSATION N Package: RoHS / Pb-free Transition DC: 0503*. 100% Matte Tin Lead Finish Pb-free / RoHS 100% Matte Tin Lead Finish* INV. INPUT N.I. INPUT OSC. OUTPUT +C.L. SENSE -C.L. SENSE RT CT GROUND 1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9 VREF +VIN EB CB CA EA SHUTDOWN COMPENSATION 20-PIN CERAMIC LEADLESS CHIP CARRIER L- PACKAGE SG1524L/883B SG1524L -55°C to 125°C -55°C to 125°C 3 2 1 20 19 1. N.C. 2. VREF 3. INV. INPUT 4. N.I. INPUT 5. OSC. OUTPUT 6. + C.L. SENSE 7. - C.L. SENSE 8. RT 9. CT 10. GROUND 4 5 6 7 8 18 17 16 15 14 9 10 11 12 13 11. COMP 12. SHUTDOWN 13. N.C. 14. EA 15. CA 16. N.C. 17. CB 18. EB 19. N.C. 20. +VIN *RoHS compliant Note 1. Contact factory for JAN and DESC product availablity. 2. All packages are viewed from the top. Rev 1.1a Copyright © 1994 6 11861 Western Avenue ∞ Garden Grove, CA 92841 (714) 898-8121 ∞ FAX: (714) 893-2570