Datasheet

ManualsBrandsTEXAS INSTRUMENTS ManualsPMICsPMIC - DC/DC voltage regulator Converter, Boost, Converter/amplifier PDIP 8

LM2578A, LM3578A

www.ti.com

SNVS767E –AUGUST 2000–REVISED APRIL 2013

LM2578A/LM3578A Switching Regulator

Check for Samples: LM2578A, LM3578A

FEATURES

DESCRIPTION

The LM2578A is a switching regulator which can

• Inverting and Non-Inverting Feedback Inputs

easily be set up for such DC-to-DC voltage

• 1.0V Reference at Inputs

conversion circuits as the buck, boost, and inverting

• Operates from Supply Voltages of 2V to 40V

configurations. The LM2578A features a unique

comparator input stage which not only has separate

• Output Current up to 750 mA, Saturation Less

pins for both the inverting and non-inverting inputs,

than 0.9V

but also provides an internal 1.0V reference to each

• Current Limit and Thermal Shut Down

input, thereby simplifying circuit design and p.c. board

• Duty Cycle up to 90%

layout. The output can switch up to 750 mA and has

output pins for its collector and emitter to promote

design flexibility. An external current limit terminal

APPLICATIONS

may be referenced to either the ground or the V

• Switching Regulators in Buck, Boost,

terminal, depending upon the application. In addition,

Inverting, and Single-Ended Transformer

the LM2578A has an on board oscillator, which sets

Configurations

the switching frequency with a single external

capacitor from <1 Hz to 100 kHz (typical).

• Motor Speed Control

• Lamp Flasher

The LM2578A is an improved version of the LM2578,

offering higher maximum ratings for the total supply

voltage and output transistor emitter and collector

voltages.

Connection Diagram

Figure 1. PDIP/SOIC Package

See Package Number D0008A or P0008E

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.

2All 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.

Summary of content (30 pages)

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LM2578A, LM3578A www.ti.com SNVS767E – AUGUST 2000 – REVISED APRIL 2013 LM2578A/LM3578A Switching Regulator Check for Samples: LM2578A, LM3578A FEATURES DESCRIPTION • • • • The LM2578A is a switching regulator which can easily be set up for such DC-to-DC voltage conversion circuits as the buck, boost, and inverting configurations. The LM2578A features a unique comparator input stage which not only has separate pins for both the inverting and non-inverting inputs, but also provides an internal 1.
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LM2578A, LM3578A SNVS767E – AUGUST 2000 – REVISED APRIL 2013 www.ti.com Functional Diagram 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) Total Supply Voltage 50V −0.
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LM2578A, LM3578A www.ti.com SNVS767E – AUGUST 2000 – REVISED APRIL 2013 Electrical Characteristics These specifications apply for 2V ≤ VIN ≤ 40V (2.2V ≤ VIN ≤ 40V for TJ ≤ −25°C), timing capacitor CT = 3900 pF, and 25% ≤ duty cycle ≤ 75%, unless otherwise specified. Values in standard typeface are for TJ = 25°C; values in boldface type apply for operation over the specified operating junction temperature range.
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LM2578A, LM3578A SNVS767E – AUGUST 2000 – REVISED APRIL 2013 www.ti.com Electrical Characteristics (continued) These specifications apply for 2V ≤ VIN ≤ 40V (2.2V ≤ VIN ≤ 40V for TJ ≤ −25°C), timing capacitor CT = 3900 pF, and 25% ≤ duty cycle ≤ 75%, unless otherwise specified. Values in standard typeface are for TJ = 25°C; values in boldface type apply for operation over the specified operating junction temperature range.
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LM2578A, LM3578A www.ti.com SNVS767E – AUGUST 2000 – REVISED APRIL 2013 Typical Performance Characteristics Oscillator Frequency Change with Temperature Oscillator Voltage Swing Figure 2. Figure 3. Input Reference Voltage Drift with Temperature Collector Saturation Voltage (Sinking Current, Emitter Grounded) Figure 4. Figure 5. Emitter Saturation Voltage (Sourcing Current, Collector at Vin) Ground Referred Current Limit Sense Voltage Figure 6. Figure 7.
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LM2578A, LM3578A SNVS767E – AUGUST 2000 – REVISED APRIL 2013 www.ti.com Typical Performance Characteristics (continued) 6 Current Limit Sense Voltage Drift with Temperature Current Limit Response Time for Various Over Drives Figure 8. Figure 9. Current Limit Sense Voltage vs Supply Voltage Supply Current Figure 10. Figure 11. Supply Current Collector Current with Emitter Output Below Ground Figure 12. Figure 13.
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LM2578A, LM3578A www.ti.com SNVS767E – AUGUST 2000 – REVISED APRIL 2013 TEST CIRCUIT* Parameter tests can be made using the test circuit shown. Select the desired Vin, collector voltage and duty cycle with adjustable power supplies. A digital volt meter with an input resistance greater than 100 MΩ should be used to measure the following: Input Reference Voltage to Ground; S1 in either position.
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LM2578A, LM3578A SNVS767E – AUGUST 2000 – REVISED APRIL 2013 www.ti.com Input Level Shift Accuracy: This specification determines the output voltage tolerance of a regulator whose output control depends on drawing equal currents from the inverting and non-inverting inputs (see the Inverting Regulator of Figure 34, and the RS-232 Line Driver Power Supply of Figure 36).
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LM2578A, LM3578A www.ti.com SNVS767E – AUGUST 2000 – REVISED APRIL 2013 Figure 14. Value of Timing Capacitor vs Oscillator Frequency OUTPUT TRANSISTOR The output transistor is capable of delivering up to 750 mA with a saturation voltage of less than 0.9V. (see Collector Saturation Voltage and Emitter Saturation Voltage curves). The emitter must not be pulled more than 1V below ground (this limit is 0.6V for TJ ≥ 100°C).
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LM2578A, LM3578A SNVS767E – AUGUST 2000 – REVISED APRIL 2013 www.ti.com Figure 16. Current Limit, Vin Referred CURRENT LIMIT TRANSIENT SUPPRESSION When noise spikes and switching transients interfere with proper current limit operation, R1 and C1 act together as a low pass filter to control the current limit circuitry's response time.
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LM2578A, LM3578A www.ti.com SNVS767E – AUGUST 2000 – REVISED APRIL 2013 Figure 19. Current Limit Sense Voltage Multiplication, Ground Referred Figure 20. Current Limit Sense Voltage Multiplication, Vin Referred UNDER-VOLTAGE LOCKOUT Under-voltage lockout is accomplished with few external components. When Vin becomes lower than the zener breakdown voltage, the output transistor is turned off.
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LM2578A, LM3578A SNVS767E – AUGUST 2000 – REVISED APRIL 2013 www.ti.com Figure 22. Maximum Duty Cycle Limiting DUTY CYCLE ADJUSTMENT When manual or mechanical selection of the output transistor's duty cycle is needed, the cirucit shown below may be used. The output will turn on with the beginning of each oscillator cycle and turn off when the current sunk by R2 and R3 from the non-inverting terminal becomes greater than the current sunk from the inverting terminal.
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LM2578A, LM3578A www.ti.com SNVS767E – AUGUST 2000 – REVISED APRIL 2013 EMITTER OUTPUT When the LM2578A output transistor is in the OFF state, if the Emitter output swings below the ground pin voltage, the output transistor will turn ON because its base is clamped near ground. The Collector Current with Emitter Output Below Ground curve shows the amount of Collector current drawn in this mode, vs temperature and Emitter voltage.
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LM2578A, LM3578A SNVS767E – AUGUST 2000 – REVISED APRIL 2013 www.ti.com BUCK REGULATOR The buck configuration is used to step an input voltage down to a lower level. Transistor Q1 in Figure 27 chops the input DC voltage into a squarewave. This squarewave is then converted back into a DC voltage of lower magnitude by the low pass filter consisting of L1 and C1.
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LM2578A, LM3578A www.ti.com SNVS767E – AUGUST 2000 – REVISED APRIL 2013 Vin = 15V R3 = 0.15Ω Vo = 5V C1 = 1820 pF Vripple = 10 mV C2 = 220 μF Io = 350 mA C3 = 20 pF fosc = 50 kHz L1 = 470 μH R1 = 40 kΩ D1 = 1N5818 R2 = 10 kΩ Figure 28. Buck or Step-Down Regulator Figure 29.
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LM2578A, LM3578A SNVS767E – AUGUST 2000 – REVISED APRIL 2013 www.ti.com Step 1: Calculate the maximum DC current through the inductor, IL(max). The necessary equations are indicated at the top of the chart and show that IL(max) = Io(max) for the buck configuration. Thus, IL(max) = 350 mA. Step 2: Calculate the inductor Volts-sec product, E-Top, according to the equations given from the chart. For the Buck: E-Top = (Vin − Vo) (Vo/Vin) (1000/fosc) =(15 − 5) (5/15) (1000/50) = 66V-μs.
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LM2578A, LM3578A www.ti.com SNVS767E – AUGUST 2000 – REVISED APRIL 2013 Component values are selected as outlined for the buck regulator with a discontinuity factor of 10%, with the addition of R4 and R5: R4 = 10VBE1Bf/Ip R5 = (Vin − V − VBE1 − Vsat) Bf/(IL(max, DC) + IR4) where: VBE1 is the VBE of transistor Q1. Vsat is the saturation voltage of the LM2578A output transistor. V is the current limit sense voltage. Bf is the forced current gain of transistor Q1 (Bf = 30 for Figure 30).
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LM2578A, LM3578A SNVS767E – AUGUST 2000 – REVISED APRIL 2013 www.ti.com Vin = 5V R4 = 200 kΩ Vo = 15V C1 = 1820 pF Vripple = 10 mV C2 = 470 μF Io = 140 mA C3 = 20 pF fosc = 50 kHz C4 = 0.0022 μF R1 = 140 kΩ L1 = 330 μH R2 = 10 kΩ D1 = 1N5818 R3 = 0.15Ω Figure 32. Boost or Step-Up Regulator R1 = (Vo − 1) R2 where R2 = 10 kΩ. R3 = V/(IL(max, DC) + 0.5 ΔIL) where: ΔIL = 2(ILOAD(min))(Vo/Vin) ΔIL is 200 mA in this example.
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LM2578A, LM3578A www.ti.com SNVS767E – AUGUST 2000 – REVISED APRIL 2013 R1 = (|Vo| +1) R2 where R2 = 10 kΩ. R3 = V/(IL(max, DC) + 0.5 ΔIL). R4 = 10VBE1Bf/(IL (max, DC) + 0.5 ΔIL) where: V, VBE1, Vsat, and Bf are defined in the Buck Converter with Boosted Output Current section. ΔIL = 2(ILOAD(min))(Vin +|Vo|)/VIN R5 is defined in the Buck Converter with Boosted Output Current section. R6 serves the same purpose as R4 in the Boost Regulator circuit and is typically 220 kΩ.
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LM2578A, LM3578A SNVS767E – AUGUST 2000 – REVISED APRIL 2013 www.ti.com where: Vd is the forward voltage drop of the diodes. Vsat is the saturation voltage of the LM2578A output transistor. Vsat1 is the saturation voltage of transistor Q1. L1 ≥ (Vin − Vsat − Vsat1) (ton/Ip) (1) where: RS-232 LINE DRIVER POWER SUPPLY The power supply, shown in Figure 36, operates from an input voltage as low as 4.2V (5V nominal), and delivers an output of ±12V at ±40 mA with better than 70% efficiency.
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LM2578A, LM3578A www.ti.com SNVS767E – AUGUST 2000 – REVISED APRIL 2013 9V ≤ Vin ≤ 15V R5 = 270 Vo = 12V C1 = 1820 pF Io = 100 mA C2 = 220 μF Vripple = 50 mV C3 = 20 pF fosc = 50 kHz C4 = 0.0022 μF R1 = 110k L1 = 220 μH R2 = 10k D1, D2 = 1N5819 R3 = 0.15 Q1 = D44 R4 = 220k Figure 35. Buck-Boost Regulator Vin = 5V R4 = 0.15Ω Vo ±12V C1 = 820 pF Io = ±40 mA C2 = 10 pF fosc = 80 kHz C3 = 220 μF R1 = 10 kΩ D1, D2, D3 = 1N5819 R2 = 240 kΩ T1 = PE-64287 R3 = 240 kΩ Figure 36.
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LM2578A, LM3578A SNVS767E – AUGUST 2000 – REVISED APRIL 2013 www.ti.com A minimum value for an ideal output capacitor C3, could be calculated as C = Io × t/ΔV where Io is the load current, t is the transistor on time (typically 0.4/fosc), and ΔV is the peak-to-peak output voltage ripple. A larger output capacitor than this theoretical value should be used since electrolytics have poor high frequency performance. Experience has shown that a value from 5 to 10 times the calculated value should be used.
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LM2578A, LM3578A www.ti.com SNVS767E – AUGUST 2000 – REVISED APRIL 2013 REVISION HISTORY Changes from Revision D (April 2013) to Revision E • Page Changed layout of National Data Sheet to TI format ..........................................................................................................
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PACKAGE OPTION ADDENDUM www.ti.
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PACKAGE OPTION ADDENDUM www.ti.com 1-Nov-2013 Green (RoHS & no Sb/Br): TI defines "Green" to mean Pb-Free (RoHS compatible), and free of Bromine (Br) and Antimony (Sb) based flame retardants (Br or Sb do not exceed 0.1% by weight in homogeneous material) (3) MSL, Peak Temp. - The Moisture Sensitivity Level rating according to the JEDEC industry standard classifications, and peak solder temperature.
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PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 TAPE AND REEL INFORMATION *All dimensions are nominal Device Package Package Pins Type Drawing SPQ Reel Reel A0 Diameter Width (mm) (mm) W1 (mm) B0 (mm) K0 (mm) P1 (mm) W Pin1 (mm) Quadrant LM2578AMX/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM3578AMX SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.0 Q1 LM3578AMX/NOPB SOIC D 8 2500 330.0 12.4 6.5 5.4 2.0 8.0 12.
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PACKAGE MATERIALS INFORMATION www.ti.com 23-Sep-2013 *All dimensions are nominal Device Package Type Package Drawing Pins SPQ Length (mm) Width (mm) Height (mm) LM2578AMX/NOPB SOIC D 8 2500 367.0 367.0 35.0 LM3578AMX SOIC D 8 2500 367.0 367.0 35.0 LM3578AMX/NOPB SOIC D 8 2500 367.0 367.0 35.
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