LM5041
Cascaded PWM Controller
General Description
The LM5041PWM controller contains all of the features necessary to implement either current-fed or voltage-fed push-pull or bridge power converters.These “Cascaded”topologies are well suited for multiple output and higher power applications.The LM5041’s four control outputs in-clude:the buck stage controls (HD and LD)and the push-pull control outputs (PUSH and PULL).Push-pull outputs are driven at 50%nominal duty cycle at one half of the switching frequency of the buck stage and can be configured for either a guaranteed overlap time (for current-fed applications)or a guaranteed both-off time (for voltage-fed applications).Push-pull stage MOSFETs can be driven directly from the internal gate drivers while the buck stage requires an exter-nal driver such as the LM5102.The LM5041includes a high-voltage start-up regulator that operates over a wide input range of 15V to 100V.The PWM controller is designed for high-speed capability including an oscillator frequency range up to 1MHz and total propagation delays of less than 100ns.Additional features include:line Under-Voltage Lock-out (UVLO),soft-start,an error amplifier,precision voltage reference,and thermal shutdown.
Features
n Internal Start-up Bias Regulator
n Programmable Line Under-Voltage Lockout (UVLO)with Adjustable Hysteresis n Current Mode Control
n Internal Error Amplifier with Reference n Dual Mode Over-Current Protection n Leading Edge Blanking
n Programmable Push-Pull Overlap or Dead Time n Internal 1.5A Push-Pull Gate Drivers n Programmable Soft-start
n Programmable Oscillator with Sync Capability n Precision Reference n Thermal Shutdown
Applications
n Telecommunication Power Converters n Industrial Power Converters n Multi-Output Power Converters n
+42V Automotive Systems
Packages
n TSSOP-16
n LLP-16(5x5mm)Thermally Enhanced清徐县教育局
Typical Application Circuit
20074901
Simplified Cascaded Push-Pull Power Converter
August 2003
LM5041Cascaded PWM Controller
©2003National Semiconductor Corporation DS200749www.national
Connection Diagram
20074902
16-Lead TSSOP,LLP
Ordering Information
Order Number Package Type NSC Package Drawing Supplied As
LM5041MTC TSSOP-16MTC-1692Units per anti-static tube LM5041MTCX TSSOP-16MTC-162500Units on Tape and Reel LM5041SD LLP-16SDA-16A Available Soon LM5041SDX
LLP-16
SDA-16A
Available Soon
Pin Description
PIN NAME DESCRIPTION
APPLICATION INFORMATION
1V IN Source Input Voltage Input to start-up regulator.Input range 15V to 100V.2
FB
Feedback Signal
Inverting input for the internal error amplifier.The non-inverting input is connected to a 0.75V reference.
3COMP Output of the Internal Error Amplifier There is an internal 5k Ωresistor pull-up on this pin.The error amplifier provides an active sink.
4
REF
Precision 5volt reference output
Maximum output current:10mA.Locally decouple with a 0.1µF capacitor.Reference stays low until the line UV and the V CC UV are satisfied.
5HD Main Buck PWM control output
Buck switch PWM control output.The maximum duty cycle clamp for this output corresponds to an off time of typically 240ns per cycle.The LM5101or LM5102Buck stage gate driver can be used to level shift and drive the Buck switch.
6LD Sync Switch control output
Sync Switch control output.Inversion of HD output.The LM5101or LM5102lower drive can be used to drive the synchronous rectifier switch.
7
V CC
Output from the internal high voltage start-up regulator.Regulated to 9volts.If an auxiliary winding raises the voltage on this pin above the regulation setpoint,the internal start-up
regulator will shutdown,reducing the IC power dissipation.8PUSH
Output of the push-pull drivers
Output of the push-pull gate driver.Output capability of 1.5A peak .
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LM5041 Pin Description(Continued)
PIN NAME DESCRIPTION APPLICATION INFORMATIONdx4
9PULL Output of the push-pull drivers Output of the push-pull gate driver.Output capability
of1.5A peak.
10PGND Power ground Connect directly to analog ground.
11AGND Analog ground Connect directly to power ground.
12CS Current sense input Current sense input to the PWM comparator(CM
control).There is a50ns leading edge blanking on
this pin.Using separate dedicated comparators,if
CS exceeds0.5V the outputs will go into cycle by
cycle current limit.If CS exceeds0.6V the outputs
will be disabled and a soft-start commenced.
13SS Soft-start control An external capacitor and an internal10uA current
source,set the soft-start ramp.The controller will
enter a low power state if the SS pin is below the
shutdown threshold of0.45V
14TIME Push-Pull overlap and dead time control An external resistor sets the overlap time or dead
time for the push-pull outputs.A resistor connected
between TIME and GND produces overlap.A
resistor connected between TIME and REF produces
dead time.
15RT/SYNC Oscillator timing resistor pin and sync An external resistor sets the oscillator frequency.
This pin will also accept an external oscillator.
16UVLO Line Under-Voltage Shutdown An external divider from the power converter source
sets the shutdown levels.Threshold of operation
equals2.5V.Hysteresis is set by a switched internal
current source(20µA).
3
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Block Diagram
Simplified Block Diagram
20074903
L M 5041
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Absolute Maximum Ratings(Note1) If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications.
V IN to GND100V
V CC to GND16V
勒夫数>永和大桥All Other Inputs to GND-0.3to7V
Junction Temperature150˚C
Storage Temperature Range -65˚C to+150˚C
ESD Rating2kV
Lead temperature(Note2)
Wave4seconds260˚C
Infrared10seconds240˚C
Vapor Phase75seconds219˚C
Operating Ratings(Note1)
V IN15to90V
Junction Temperature-40˚C to+105˚C
Electrical Characteristics
Specifications with standard typeface are for T J=25˚C,and those with boldface type apply over full Operating Junction Temperature range.V IN=48V,V CC=10V,RT=26.7kΩ,R SET=20kΩ)unless otherwise stated(Note3)
Symbol Parameter Conditions Min Typ Max Units Startup Regulator
V CC Reg V CC Regulation open circuit8.799.3V V CC Current Limit(Note4)1525mA I-V IN Startup
Regulator
Leakage(external Vcc
Supply)
V IN=100V145500µA
Shutdown Current(Iin)UVLO=0V,V CC=open350450µA V CC Supply
V CC Under-voltage Lockout Voltage (positive going V cc)V CC Reg
-400mV
V CC Reg-
275mV
V
V CC Under-voltage
Hysteresis
罗尔定理1.7
2.1 2.6V
Supply Current(I CC)C L=034mA Error Amplifier
GBW Gain Bandwidth3MHz DC Gain80dB
Input Voltage V FB=COMP0.7350.750.765V
COMP Sink Capability V FB=1.5V,COMP=1V48mA Reference Supply
V REF Ref Voltage I REF=0mA 4.855 5.15V Ref Voltage
Regulation
Ref Current Limit1520mA Current Limit
ILIM Delay to Output CS Step from0to0.6V
Time to Onset of OUT
Transition(90%)
C L=0
40ns
Cycle by Cycle
Threshold Voltage
0.450.50.55V
Cycle Skip Threshold Voltage Resets SS capacitor;
auto restart
0.550.60.65V
Leading Edge
Blanking Time
50ns
CS Sink Current (clocked)CS=0.3V25mA
LM5041
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