LM2524D, LM3524D www.ti.com SNVS766E - JUNE 2009 - REVISED MAY 2013 LM2524D/LM3524D Regulating Pulse Width Modulator Check for Samples: LM2524D, LM3524D FEATURES 1 * 2 * * * * * * * * Fully Interchangeable With Standard LM3524 Family 1% Precision 5V Reference With Thermal Shut-Down Output Current to 200 mA DC 60V Output Capability Wide Common Mode Input Range for ErrorAmp One Pulse per Period (Noise Suppression) Improved Max. Duty Cycle at High Frequencies Double Pulse Suppression Synchronize Through Pin 3 DESCRIPTION The LM3524D family is an improved version of the industry standard LM3524. It has improved specifications and additional features yet is pin for pin compatible with existing 3524 families. New features reduce the need for additional external circuitry often required in the original version. The LM3524D has a 1% precision 5V reference. The current carrying capability of the output drive transistors has been raised to 200 mA while reducing VCEsat and increasing VCE breakdown to 60V. The common mode voltage range of the error-amp has been raised to 5.5V to eliminate the need for a resistive divider from the 5V reference. In the LM3524D the circuit bias line has been isolated from the shut-down pin. This prevents the oscillator pulse amplitude and frequency from being disturbed by shut-down. Also at high frequencies (300 kHz) the max. duty cycle per output has been improved to 44% compared to 35% max. duty cycle in other 3524s. In addition, the LM3524D can now be synchronized externally, through pin 3. Also a latch has been added to insure one pulse per period even in noisy environments. The LM3524D includes double pulse suppression logic that insures when a shut-down condition is removed the state of the T-flip-flop will change only after the first clock pulse has arrived. This feature prevents the same output from being pulsed twice in a row, thus reducing the possibility of core saturation in push-pull designs. Connection Diagram Figure 1. Top View See Package Number NFG See Package Number D 1 2 Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet. All trademarks are the property of their respective owners. PRODUCTION DATA information is current as of publication date. Products conform to specifications per the terms of the Texas Instruments standard warranty. Production processing does not necessarily include testing of all parameters. Copyright (c) 2009-2013, Texas Instruments Incorporated LM2524D, LM3524D SNVS766E - JUNE 2009 - REVISED MAY 2013 www.ti.com Block Diagram 2 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D LM2524D, LM3524D www.ti.com SNVS766E - JUNE 2009 - REVISED MAY 2013 These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam during storage or handling to prevent electrostatic damage to the MOS gates. Absolute Maximum Ratings (1) (2) Supply Voltage 40V Collector Supply Voltage LM2524D 55V LM3524D 40V Output Current DC (each) 200 mA Oscillator Charging Current (Pin 7) 5 mA Internal Power Dissipation Operating Junction Temperature Range 1W (3) LM2524D -40C to +125C LM3524D 0C to +125C Maximum Junction Temperature 150 -65C to +150C Storage Temperature Range Lead Temperature (Soldering 4 sec.) (1) NFG, D Pkg. 260C Absolute maximum ratings indicate limits beyond which damage to the device may occur. DC and AC electrical specifications do not apply when operating the device beyond its rated operating conditions. If Military/Aerospace specified devices are required, please contact the Texas Instruments Sales Office/Distributors for availability and specifications. For operation at elevated temperatures, devices in the NFG package must be derated based on a thermal resistance of 86C/W, junction to ambient. Devices in the D package must be derated at 125C/W, junction to ambient. (2) (3) Electrical Characteristics (1) Symbol Parameter Conditions LM2524D LM3524D Typ Tested Limit (2) Design Limit (3) Typ Tested Limit (2) 5 4.85 4.80 5 4.75 Units Design Limit (3) REFERENCE SECTION VREF Output Voltage 5.15 5.20 VRLine Line Regulation VIN = 8V to 40V 10 15 30 10 25 50 mVMax VRLoad Load Regulation IL = 0 mA to 20 mA 10 15 25 10 25 50 mVMax VIN/VREF Ripple Rejection f = 120 Hz 66 IOS Short Circuit Current VREF = 0 5.25 10 Hz f 10 kHz 40 Long Term Stability TA = 125C 20 550 dB 25 mA Min 50 180 Output Noise VMax 66 25 50 NO VMin 200 100 40 mA Max Vrms 100 Max 20 mV/kHr OSCILLATOR SECTION fOSC Max. Freq. RT = 1k, CT = 0.001 F (4) fOSC Initial Accuracy RT = 5.6k, CT = 0.01 F (4) 500 RT = 2.7k, CT = 0.01 F (4) kHzMin 22.5 22.5 kHzMax 34 30 kHzMin 46 kHzMax 20 38 38 42 (2) (3) (4) kHzMin 17.5 20 (1) 350 17.5 Unless otherwise stated, these specifications apply for TA = TJ = 25C. Boldface numbers apply over the rated temperature range: LM2524D is -40 to 85C and LM3524D is 0C to 70C. VIN = 20V and fOSC = 20 kHz. Tested limits are ensured and 100% tested in production. Design limits are ensured (but not 100% production tested) over the indicated temperature and supply voltage range. These limits are not used to calculate outgoing quality level. The value of a Ct capacitor can vary with frequency. Careful selection of this capacitor must be made for high frequency operation. Polystyrene was used in this test. NPO ceramic or polypropylene can also be used. Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D Submit Documentation Feedback 3 LM2524D, LM3524D SNVS766E - JUNE 2009 - REVISED MAY 2013 www.ti.com Electrical Characteristics(1) (continued) Symbol Parameter Conditions fOSC Freq. Change with VIN VIN = 8 to 40V fOSC Freq. Change with Temp. TA = -55C to +125C at 20 kHz RT = 5.6k, CT = 0.01 F VOSC Output Amplitude (Pin 3) RT = 5.6k, CT = 0.01 F tPW LM2524D Typ Tested Limit (2) 0.5 1 LM3524D Design Limit (3) 5 Tested Limit (2) 0.5 1.0 Design Limit (3) 2.4 Output Pulse Width (Pin 3) RT = 5.6k, CT = 0.01 F 0.5 1.5 Sawtooth Peak Voltage RT = 5.6k, CT = 0.01 F 3.4 3.6 3.8 Sawtooth Valley Voltage RT = 5.6k, CT = 0.01 F 1.1 0.8 0.6 2 8 10 Units %Max 5 3 (5) Typ % 3 2.4 VMin 0.5 1.5 sMax 3.8 VMax 0.6 VMin 2 10 mVMax ERROR-AMP SECTION VIO Input Offset Voltage VCM = 2.5V IIB Input Bias Current VCM = 2.5V 1 8 10 1 10 AMax IIO Input Offset Current VCM = 2.5V 0.5 1.0 1 0.5 1 AMax ICOSI Compensation Current (Sink) VIN(I) - VIN(NI) = 150 mV 65 AMin 125 125 AMax Compensation Current (Source) VIN(NI) - VIN(I) = 150 mV -125 -125 AMin AVOL Open Loop Gain RL = , VCM = 2.5 V VCMR Common Mode Input Voltage Range CMRR Common Mode Rejection Ratio GBW Unity Gain Bandwidth AVOL = 0 dB, VCM = 2.5V VO Output Voltage Swing RL = ICOSO 65 95 95 -95 -95 -65 PSRR Power Supply Rejection Ratio 80 90 -65 60 1.5 1.4 1.5 VMin 5.5 5.4 5.5 VMax 80 dBMin 80 80 90 3 70 AMax 74 2 60 dBMin MHz 0.5 0.5 VMin 5.5 5.5 VMax 80 65 dbMin VIN = 8 to 40V 80 Minimum Duty Cycle Pin 9 = 0.8V, [RT = 5.6k, CT = 0.01 F] 0 0 0 0 %Max Maximum Duty Cycle Pin 9 = 3.9V, [RT = 5.6k, CT = 0.01 F] 49 45 49 45 %Min Maximum Duty Cycle Pin 9 = 3.9V, [RT = 1k, CT = 0.001 F] 44 35 44 35 %Min Input Threshold Zero Duty Cycle 1 1 V 3.5 3.5 V -1 -1 A 70 COMPARATOR SECTION tON/tOSC tON/tOSC tON/tOSC VCOMPZ (Pin 9) VCOMPM Input Threshold (Pin 9) IIB Input Bias Current Maximum Duty Cycle CURRENT LIMIT SECTION VSEN Sense Voltage V(Pin 2) - V(Pin 1) 150 mV 180 200 Sense Voltage T.C. Common Mode Voltage Range (5) 4 V5 - V4 = 300 mV mVMin 220 mVMax 200 220 TC-Vsense 180 0.2 0.2 mV/C -0.7 -0.7 VMin 1 1 VMax OSC amplitude is measured open circuit. Available current is limited to 1 mA so care must be exercised to limit capacitive loading of fast pulses. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D LM2524D, LM3524D www.ti.com SNVS766E - JUNE 2009 - REVISED MAY 2013 Electrical Characteristics(1) (continued) Symbol Parameter Conditions LM2524D Typ Tested Limit (2) 1 0.5 LM3524D Design Limit (3) Design Limit (3) Units Typ Tested Limit (2) 1 0.5 VMin 1.5 VMax SHUT DOWN SECTION VSD High Input Voltage V(Pin 2) - V(Pin 1) 150 mV 1.5 ISD High Input Current I(pin 10) 1 1 mA OUTPUT SECTION (EACH OUTPUT) VCES Collector Emitter Voltage Breakdown IC 100 A ICES Collector Leakage Current VCE = 60V VCE = 55V 55 0.1 Saturation Voltage VMin AMax 50 VCE = 40V VCESAT 40 0.1 50 IE = 20 mA 0.2 0.5 0.2 0.7 IE = 200 mA 1.5 2.2 1.5 2.5 17 18 17 VMax VEO Emitter Output Voltage IE = 50 mA 18 tR Rise Time VIN = 20V, IE = -250 A RC = 2k 200 200 VMin ns tF Fall Time RC = 2k 100 100 ns SUPPLY CHARACTERISTICS SECTION VIN T IIN (6) (7) Input Voltage Range Thermal Shutdown Temp. Stand By Current After Turn-on (6) 8 8 VMin 40 40 VMax 160 VIN = 40V (7) 5 160 10 5 C 10 mA For operation at elevated temperatures, devices in the NFG package must be derated based on a thermal resistance of 86C/W, junction to ambient. Devices in the D package must be derated at 125C/W, junction to ambient. Pins 1, 4, 7, 8, 11, and 14 are grounded; Pin 2 = 2V. All other inputs and outputs open. Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D Submit Documentation Feedback 5 LM2524D, LM3524D SNVS766E - JUNE 2009 - REVISED MAY 2013 www.ti.com Typical Performance Characteristics 6 Switching Transistor Peak Output Current vs Temperature Maximum Average Power Dissipation (NFG, D Packages) Figure 2. Figure 3. Maximum & Minimum Duty Cycle Threshold Voltage Output Transistor Saturation Voltage Figure 4. Figure 5. Output Transistor Emitter Voltage Reference Transistor Peak Output Current Figure 6. Figure 7. Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D LM2524D, LM3524D www.ti.com SNVS766E - JUNE 2009 - REVISED MAY 2013 Typical Performance Characteristics (continued) Standby Current vs Voltage Standby Current vs Temperature Figure 8. Figure 9. Current Limit Sense Voltage Figure 10. Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D Submit Documentation Feedback 7 LM2524D, LM3524D SNVS766E - JUNE 2009 - REVISED MAY 2013 www.ti.com TEST CIRCUIT 8 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D LM2524D, LM3524D www.ti.com SNVS766E - JUNE 2009 - REVISED MAY 2013 Functional Description Internal Voltage Regulator The LM3524D has an on-chip 5V, 50 mA, short circuit protected voltage regulator. This voltage regulator provides a supply for all internal circuitry of the device and can be used as an external reference. For input voltages of less than 8V the 5V output should be shorted to pin 15, VIN, which disables the 5V regulator. With these pins shorted the input voltage must be limited to a maximum of 6V. If input voltages of 6V-8V are to be used, a pre-regulator, as shown in Figure 11, must be added. *Minimum CO of 10 F required for stability. Figure 11. Oscillator The LM3524D provides a stable on-board oscillator. Its frequency is set by an external resistor, RT and capacitor, CT. A graph of RT, CT vs oscillator frequency is shown is Figure 12. The oscillator's output provides the signals for triggering an internal flip-flop, which directs the PWM information to the outputs, and a blanking pulse to turn off both outputs during transitions to ensure that cross conduction does not occur. The width of the blanking pulse, or dead time, is controlled by the value of CT, as shown in Figure 13. The recommended values of RT are 1.8 k to 100 k, and for CT, 0.001 F to 0.1 F. If two or more LM3524D's must be synchronized together, the easiest method is to interconnect all pin 3 terminals, tie all pin 7's (together) to a single CT, and leave all pin 6's open except one which is connected to a single RT. This method works well unless the LM3524D's are more than 6 apart. A second synchronization method is appropriate for any circuit layout. One LM3524D, designated as master, must have its RTCT set for the correct period. The other slave LM3524D(s) should each have an RTCT set for a 10% longer period. All pin 3's must then be interconnected to allow the master to properly reset the slave units. The oscillator may be synchronized to an external clock source by setting the internal free-running oscillator frequency 10% slower than the external clock and driving pin 3 with a pulse train (approx. 3V) from the clock. Pulse width should be greater than 50 ns to insure full synchronization. Figure 12. Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D Submit Documentation Feedback 9 LM2524D, LM3524D SNVS766E - JUNE 2009 - REVISED MAY 2013 www.ti.com Figure 13. Error Amplifier The error amplifier is a differential input, transconductance amplifier. Its gain, nominally 86 dB, is set by either feedback or output loading. This output loading can be done with either purely resistive or a combination of resistive and reactive components. A graph of the amplifier's gain vs output load resistance is shown in Figure 14. Figure 14. The output of the amplifier, or input to the pulse width modulator, can be overridden easily as its output impedance is very high (ZO 5 M). For this reason a DC voltage can be applied to pin 9 which will override the error amplifier and force a particular duty cycle to the outputs. An example of this could be a non-regulating motor speed control where a variable voltage was applied to pin 9 to control motor speed. A graph of the output duty cycle vs the voltage on pin 9 is shown in Figure 15. The duty cycle is calculated as the percentage ratio of each output's ON-time to the oscillator period. Paralleling the outputs doubles the observed duty cycle. 10 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D LM2524D, LM3524D www.ti.com SNVS766E - JUNE 2009 - REVISED MAY 2013 Figure 15. The amplifier's inputs have a common-mode input range of 1.5V-5.5V. The on board regulator is useful for biasing the inputs to within this range. Current Limiting The function of the current limit amplifier is to override the error amplifier's output and take control of the pulse width. The output duty cycle drops to about 25% when a current limit sense voltage of 200 mV is applied between the +CL and -CLsense terminals. Increasing the sense voltage approximately 5% results in a 0% output duty cycle. Care should be taken to ensure the -0.7V to +1.0V input common-mode range is not exceeded. In most applications, the current limit sense voltage is produced by a current through a sense resistor. The accuracy of this measurement is limited by the accuracy of the sense resistor, and by a small offset current, typically 100 A, flowing from +CL to -CL. Output Stages The outputs of the LM3524D are NPN transistors, capable of a maximum current of 200 mA. These transistors are driven 180 out of phase and have non-committed open collectors and emitters as shown in Figure 16. Figure 16. Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D Submit Documentation Feedback 11 LM2524D, LM3524D SNVS766E - JUNE 2009 - REVISED MAY 2013 www.ti.com Typical Applications Figure 17. Positive Regulator, Step-Up Basic Configuration (IIN(MAX) = 80 mA) (1) Figure 18. Positive Regulator, Step-Up Boosted Current Configuration 12 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D LM2524D, LM3524D www.ti.com SNVS766E - JUNE 2009 - REVISED MAY 2013 Figure 19. Positive Regulator, Step-Down Basic Configuration (IIN(MAX) = 80 mA) (2) Figure 20. Positive Regulator, Step-Down Boosted Current Configuration Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D Submit Documentation Feedback 13 LM2524D, LM3524D SNVS766E - JUNE 2009 - REVISED MAY 2013 www.ti.com Figure 21. Boosted Current Polarity Inverter (3) Basic Switching Regulator Theory and Applications The basic circuit of a step-down switching regulator circuit is shown in Figure 22, along with a practical circuit design using the LM3524D in Figure 25. Figure 22. Basic Step-Down Switching Regulator The circuit works as follows: Q1 is used as a switch, which has ON and OFF times controlled by the pulse width modulator. When Q1 is ON, power is drawn from VIN and supplied to the load through L1; VA is at approximately VIN, D1 is reverse biased, and Co is charging. When Q1 turns OFF the inductor L1 will force VA negative to keep the current flowing in it, D1 will start conducting and the load current will flow through D1 and L1. The voltage at VAis smoothed by the L1, Co filter giving a clean DC output. The current flowing through L1 is equal to the nominal DC load current plus some IL which is due to the changing voltage across it. A good rule of thumb is to set ILP-P 40% x Io. 14 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D LM2524D, LM3524D www.ti.com SNVS766E - JUNE 2009 - REVISED MAY 2013 Figure 23. Relation of Switch Timing to Inductor Current in Step-Down Regulator (4) Neglecting VSAT, VD, and settling IL+ = IL-; (5) where T = Total Period The above shows the relation between VIN, Vo and duty cycle. (6) as Q1 only conducts during tON. (7) The efficiency, , of the circuit is: (8) MAX will be further decreased due to switching losses in Q1. For this reason Q1 should be selected to have the maximum possible fT, which implies very fast rise and fall times. Calculating Inductor L1 (9) Since IL+ = IL- = 0.4Io Solving the above for L1 Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D Submit Documentation Feedback 15 LM2524D, LM3524D SNVS766E - JUNE 2009 - REVISED MAY 2013 www.ti.com (10) where: L1 is in Henrys f is switching frequency in Hz Also, see LM1578 data sheet for graphical methods of inductor selection. Calculating Output Filter Capacitor Co Figure 23 shows L1's current with respect to Q1's tON and tOFF times (VA is at the collector of Q1). This curent must flow to the load and Co. Co's current will then be the difference between IL, and Io. Ico = IL - Io (11) From Figure 23 it can be seen that current will be flowing into Co for the second half of tON through the first half of tOFF, or a time, tON/2 + tOFF/2. The current flowing for this time is IL/4. The resulting Vc or Vo is described by: (12) For best regulation, the inductor's current cannot be allowed to fall to zero. Some minimum load current Io, and thus inductor current, is required as shown below: (13) Figure 24. Inductor Current Slope in Step-Down Regulator A complete step-down switching regulator schematic, using the LM3524D, is illustrated in Figure 25. Transistors Q1 and Q2 have been added to boost the output to 1A. The 5V regulator of the LM3524D has been divided in half to bias the error amplifier's non-inverting input to within its common-mode range. Since each output transistor is on for half the period, actually 45%, they have been paralleled to allow longer possible duty cycle, up to 90%. This makes a lower possible input voltage. The output voltage is set by: (14) where VNI is the voltage at the error amplifier's non-inverting input. 16 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D LM2524D, LM3524D www.ti.com SNVS766E - JUNE 2009 - REVISED MAY 2013 Resistor R3 sets the current limit to: (15) Figure 26 and Figure 27 show a PC board layout and stuffing diagram for the 5V, 1A regulator of Figure 25. The regulator's performance is listed in Table 1. *Mounted to Staver Heatsink No. V5-1. Q1 = BD344 Q2 = 2N5023 L1 = >40 turns No. 22 wire on Ferroxcube No. K300502 Torroid core. Figure 25. 5V, 1 Amp Step-Down Switching Regulator Table 1. Parameter Conditions Typical Characteristics Output Voltage VIN = 10V, Io = 1A 5V Switching Frequency VIN = 10V, Io = 1A 20 kHz Short Circuit Current Limit VIN = 10V 1.3A Load Regulation VIN = 10V Io = 0.2 - 1A 3 mV Line Regulation VIN = 10 - 20V, Io = 1A 6 mV Efficiency VIN = 10V, Io = 1A 80% Output Ripple VIN = 10V, Io = 1A 10 mVp-p Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D Submit Documentation Feedback 17 LM2524D, LM3524D SNVS766E - JUNE 2009 - REVISED MAY 2013 www.ti.com Figure 26. 5V, 1 Amp Switching Regulator, Foil Side Figure 27. Stuffing Diagram, Component Side The Step-Up Switching Regulator Figure 28 shows the basic circuit for a step-up switching regulator. In this circuit Q1 is used as a switch to alternately apply VIN across inductor L1. During the time, tON, Q1 is ON and energy is drawn from VIN and stored in L1; D1 is reverse biased and Io is supplied from the charge stored in Co. When Q1 opens, tOFF, voltage V1 will rise positively to the point where D1 turns ON. The output current is now supplied through L1, D1 to the load and any charge lost from Co during tON is replenished. Here also, as in the step-down regulator, the current through L1 has a DC component plus some IL. IL is again selected to be approximately 40% of IL. Figure 29 shows the inductor's current in relation to Q1's ON and OFF times. 18 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D LM2524D, LM3524D www.ti.com SNVS766E - JUNE 2009 - REVISED MAY 2013 Figure 28. Basic Step-Up Switching Regulator Figure 29. Relation of Switch Timing to Inductor Current in Step-Up Regulator (16) Since IL+ = IL-, VINtON = VotOFF - VINtOFF, and neglecting VSAT and VD1 (17) The above equation shows the relationship between VIN, Vo and duty cycle. In calculating input current IIN(DC), which equals the inductor's DC current, assume first 100% efficiency: (18) for = 100%, POUT = PIN (19) This equation shows that the input, or inductor, current is larger than the output current by the factor (1 + tON/tOFF). Since this factor is the same as the relation between Vo and VIN, IIN(DC) can also be expressed as: (20) Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D Submit Documentation Feedback 19 LM2524D, LM3524D SNVS766E - JUNE 2009 - REVISED MAY 2013 www.ti.com So far it is assumed = 100%, where the actual efficiency or MAX will be somewhat less due to the saturation voltage of Q1 and forward on voltage of D1. The internal power loss due to these voltages is the average IL current flowing, or IIN, through either VSAT or VD1. For VSAT = VD1 = 1V this power loss becomes IIN(DC) (1V). MAX is then: (21) (22) This equation assumes only DC losses, however MAX is further decreased because of the switching time of Q1 and D1. In calculating the output capacitor Co it can be seen that Co supplies Io during tON. The voltage change on Co during this time will be some Vc = Vo or the output ripple of the regulator. Calculation of Co is: (23) where: Co is in farads, f is the switching frequency, Vo is the p-p output ripple Calculation of inductor L1 is as follows: (24) VIN is applied across L1 (25) where: L1 is in henrys, f is the switching frequency in Hz To apply the above theory, a complete step-up switching regulator is shown in Figure 30. Since VIN is 5V, VREF is tied to VIN. The input voltage is divided by 2 to bias the error amplifier's inverting input. The output voltage is: (26) The network D1, C1 forms a slow start circuit. 20 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D LM2524D, LM3524D www.ti.com SNVS766E - JUNE 2009 - REVISED MAY 2013 This holds the output of the error amplifier initially low thus reducing the duty-cycle to a minimum. Without the slow start circuit the inductor may saturate at turn-on because it has to supply high peak currents to charge the output capacitor from 0V. It should also be noted that this circuit has no supply rejection. By adding a reference voltage at the non-inverting input to the error amplifier, see Figure 31, the input voltage variations are rejected. The LM3524D can also be used in inductorless switching regulators. Figure 32 shows a polarity inverter which if connected to Figure 30 provides a -15V unregulated output. L1 = > 25 turns No. 24 wire on Ferroxcube No. K300502 Toroid core. Figure 30. 15V, 0.5A Step-Up Switching Regulator Figure 31. Replacing R3/R4 Divider in Figure 30 with Reference Circuit Improves Line Regulation Figure 32. Polarity Inverter Provides Auxiliary -15V Unregulated Output from Circuit of Figure 30 Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D Submit Documentation Feedback 21 LM2524D, LM3524D SNVS766E - JUNE 2009 - REVISED MAY 2013 www.ti.com REVISION HISTORY Changes from Revision D (May 2013) to Revision E * 22 Page Changed layout of National Data Sheet to TI format .......................................................................................................... 21 Submit Documentation Feedback Copyright (c) 2009-2013, Texas Instruments Incorporated Product Folder Links: LM2524D LM3524D PACKAGE OPTION ADDENDUM www.ti.com 14-May-2018 PACKAGING INFORMATION Orderable Device Status (1) Package Type Package Pins Package Drawing Qty Eco Plan Lead/Ball Finish MSL Peak Temp (2) (6) (3) Op Temp (C) Device Marking (4/5) LM2524DN/NOPB ACTIVE PDIP NFG 16 25 Pb-Free (RoHS) CU SN Level-1-NA-UNLIM -40 to 125 LM2524DN LM3524DM/NOPB ACTIVE SOIC D 16 48 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM 0 to 125 LM3524DM LM3524DMX/NOPB ACTIVE SOIC D 16 2500 Green (RoHS & no Sb/Br) CU SN Level-1-260C-UNLIM 0 to 125 LM3524DM LM3524DN/NOPB ACTIVE PDIP NFG 16 25 Green (RoHS & no Sb/Br) CU SN Level-1-NA-UNLIM 0 to 125 LM3524DN (1) The marketing status values are defined as follows: ACTIVE: Product device recommended for new designs. LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect. NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design. PREVIEW: Device has been announced but is not in production. Samples may or may not be available. OBSOLETE: TI has discontinued the production of the device. (2) RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may reference these types of products as "Pb-Free". RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption. Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of <=1000ppm threshold. Antimony trioxide based flame retardants must also meet the <=1000ppm threshold requirement. (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature. (4) There may be additional marking, which relates to the logo, the lot trace code information, or the environmental category on the device. (5) Multiple Device Markings will be inside parentheses. Only one Device Marking contained in parentheses and separated by a "~" will appear on a device. If a line is indented then it is a continuation of the previous line and the two combined represent the entire Device Marking for that device. (6) Lead/Ball Finish - Orderable Devices may have multiple material finish options. Finish options are separated by a vertical ruled line. Lead/Ball Finish values may wrap to two lines if the finish value exceeds the maximum column width. Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the accuracy of such information. Efforts are underway to better integrate information from third parties. TI has taken and Addendum-Page 1 Samples PACKAGE OPTION ADDENDUM www.ti.com 14-May-2018 continues to take reasonable steps to provide representative and accurate information but may not have conducted destructive testing or chemical analysis on incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited information may not be available for release. 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Addendum-Page 2 PACKAGE MATERIALS INFORMATION www.ti.com 18-Aug-2014 TAPE AND REEL INFORMATION *All dimensions are nominal Device LM3524DMX/NOPB Package Package Pins Type Drawing SOIC D 16 SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) 2500 330.0 16.4 Pack Materials-Page 1 6.5 B0 (mm) K0 (mm) P1 (mm) 10.3 2.3 8.0 W Pin1 (mm) Quadrant 16.0 Q1 PACKAGE MATERIALS INFORMATION www.ti.com 18-Aug-2014 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM3524DMX/NOPB SOIC D 16 2500 367.0 367.0 35.0 Pack Materials-Page 2 MECHANICAL DATA NFG0016E N0016E N16E (Rev G) www.ti.com IMPORTANT NOTICE Texas Instruments Incorporated (TI) reserves the right to make corrections, enhancements, improvements and other changes to its semiconductor products and services per JESD46, latest issue, and to discontinue any product or service per JESD48, latest issue. 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