当前位置：文档库 › UC3525AQTR中文资料

UC3525AQTR中文资料

UC2525A/27A UC3525A/27A

Regulating Pulse Width Modulators

FEATURES

?8to 35V Operation

?5.1V Reference Trimmed to ±1%?100Hz to 500kHz Oscillator Range ?Separate Oscillator Sync Terminal ?Adjustable Deadtime Control ?Internal Soft-Start ?Pulse-by-Pulse Shutdown ?Input Undervoltage Lockout with Hysteresis

?Latching PWM to Prevent Multiple Pulses

?Dual Source/Sink Output

Drivers

BLOCK DIAGRAM

DESCRIPTION

The UC1525A/1527A series of pulse width modulator integrated circuits are de-signed to offer improved performance and lowered external parts count when used in designing all types of switching power supplies.The on-chip +5.1V ref-erence is trimmed to ±1%and the input common-mode range of the error ampli-fier includes the reference voltage,eliminating external resistors.A sync input to the oscillator allows multiple units to be slaved or a single unit to be synchro-nized to an external system clock.A single resistor between the C T and the dis-charge terminals provides a wide range of dead-time adjustment.These devices also feature built-in soft-start circuitry with only an external timing ca-pacitor required.A shutdown terminal controls both the soft-start circuitry and the output stages,providing instantaneous turn off through the PWM latch with pulsed shutdown,as well as soft-start recycle with longer shutdown commands.These functions are also controlled by an undervoltage lockout which keeps the outputs off and the soft-start capacitor discharged for sub-normal input volt-ages.This lockout circuitry includes approximately 500mV of hysteresis for jit-ter-free operation.Another feature of these PWM circuits is a latch following the comparator.Once a PWM pulse has been terminated for any reason,the out-puts will remain off for the duration of the period.The latch is reset with each clock pulse.The output stages are totem-pole designs capable of sourcing or sinking in excess of 200mA.The UC1525A output stage features NOR logic,giving a LOW output for an OFF state.The UC1527A utilizes OR logic which results in a HIGH output level when OFF .

ABSOLUTE MAXIMUM RATINGS(Note1)

Supply Voltage,(+V IN) (40)

Collector Supply Voltage(V C) (40)

Logic Inputs............................–0.3V to+5.5V Analog Inputs............................–0.3V to+V IN Output Current,Source or Sink...................500mA Reference Output Current........................50mA Oscillator Charging Current........................5mA Power Dissipation at T A=+25°C(Note2)..........1000mW Power Dissipation at T C=+25°C(Note2).........2000mW Operating Junction Temperature..........–55°C to+150°C Storage Temperature Range.............–65°C to+150°C Lead Temperature(Soldering,10seconds).........+300°C Note1:Values beyond which damage may occur.

Note2:Consult packaging Section of Databook for thermal limitations and considerations of package.RECOMMENDED OPERATING CONDITIONS (Note3)

Input Voltage(+V IN).......................+8V to+35V Collector Supply Voltage(V C)...............+4.5V to+35V Sink/Source Load Current(steady state)........0to100mA Sink/Source Load Current(peak)..............0to400mA Reference Load Current......................0to20mA Oscillator Frequency Range..............100Hz to400kHz Oscillator Timing Resistor..................2k?to150k?Oscillator Timing Capacitor................001μF to.01μF Dead Time Resistor Range....................0to500?Operating Ambient Temperature Range

UC1525A,UC1527A..................–55°C to+125°C UC2525A,UC2527A...................–25°C to+85°C UC3525A,UC3527A.....................0°C to+70°C Note3:Range over which the device is functional and parame-ter limits are guaranteed.

CONNECTION DIAGRAMS

ELECTRICAL CHARACTERISTICS:+V IN =20V,and over operating temperature,unless otherwise specified,T A =T J .

PARAMETER

TEST CONDITIONS

UC1525A/UC2525A UC1527A/UC2527A UC3525A UC3527A UNITS

MIN

TYP

MAX

MIN

TYP

MAX

Reference Section Output Voltage T J =25°C 5.05

5.10 5.15 5.00

5.10 5.20V Line Regulation V IN =8to 35V 10201020mV Load Regulation

I L =0to 20mA 20502050mV

Temperature Stability (Note 5)Over Operating Range 20

5020

50Total Output Variation (Note 5)Line,Load,and Temperature 5.00

5.20 4.95

5.25V Shorter Circuit Current V REF =0,T J =25°C 8010080100mA Output Noise Voltage (Note 5)10Hz 10kHz,T =25C J ≤°4020040200μVrms Long Term Stability (Note 5)T J =125°C

mV Oscillator Section (Note 6)Initial Accuracy (Notes 5&6)T J =25°C ±2±6±2±6%Voltage Stability (Notes 5&6)V IN =8to 35V ±0.3±1±1±2%Temperature Stability (Note 5)Over Operating Range ±3

±6±3

±6%Minimum Frequency R T =200k ?,C T =0.1μF 120

120

Hz Maximum Frequency R T =2k ?,C T =470pF 400400kHz Current Mirror

I RT =2mA

1.7

2.0 2.2

1.7

2.0 2.2

mA Clock Amplitude (Notes 5&6) 3.0 3.5 3.0 3.5V Clock Width (Notes 5&6)T J =25°C 0.30.5 1.00.30.5 1.0μs Sync Threshold 1.2

2.0 2.8 1.2

2.0 2.8V Sync Input Current

Sync Voltage =3.5V 1.0

2.5 1.0

2.5mA

Error Amplifier Section (V CM =5.1V)Input Offset Voltage 0.55210mV Input Bias Current 1

101

10μA Input Offset Current 1

μA DC Open Loop Gain R L ≥10M ?60756075dB Gain-Bandwidth Product

(Note 5)

A V =0dB,T J =25°C 1212MHz DC Transconductance (Notes 5&7)T J =25°C,30k ?≤R L ≤1M ?

1.1

1.5 1.1

1.5mS Output Low Level 0.20.5

0.20.5

V Output High Level 3.8 5.6 3.8 5.6V Common Mode Rejection V CM =1.5to 5.2V 60756075dB Supply Voltage Rejection

V IN =8to 35V

Note 5:These parameters,although ensured over the recommended operating conditions,are not 100%tested in production.Note 6:Tested at f OSC =40kHz (R T =3.6k W ,C T =0.01m F,R D =0W).Approximate oscillator frequency is defined by:

f C R T T D =

0.73R ()

Note 7:DC transconductance (g M )relates to DC open-loop voltage gain (A V )according to the following equation:A V =g M R L

where R L is the resistance from pin 9to ground .The minimum g M specification is used to calculate minimum A V when the error amplifier output is loaded.

ELECTRICAL CHARACTERISTICS:+V IN=20V,and over operating temperature,unless otherwise specified,T A=T J.

PARAMETER TEST CONDITIONS UC1525A/UC2525A

UC1527A/UC2527A

UC3525A

UC3527A

UNITS MIN TYP MAX MIN TYP MAX

PWM Comparator

Minimum Duty-Cycle00% Maximum Duty-Cycle(Note6)45494549% Input Threshold(Note6)Zero Duty-Cycle0.70.90.70.9V

Maximum Duty-Cycle 3.3 3.6 3.3 3.6V Input Bias Current(Note5).05 1.0.05 1.0μA Shutdown Section

Soft Start Current V SD=0V,V SS=0V255080255080μA Soft Start Low Level V SD=2.5V0.40.70.40.7V Shutdown Threshold To outputs,V SS=5.1V,T J=25°C0.60.8 1.00.60.8 1.0V Shutdown Input Current V SD=2.5V0.4 1.00.4 1.0mA Shutdown Delay(Note5)V SD=2.5V,T J=25°C0.20.50.20.5μs Output Drivers(Each Output)(V C=20V)

Output Low Level I SINK=20mA0.20.40.20.4V

I SINK=100mA 1.0 2.0 1.0 2.0V

Output High Level I SOURCE=20mA18191819V

I SOURCE=100mA17181718V

Under-Voltage Lockout V COMP and V SS=High678678V V C OFF Current(Note7)V C=35V200200μA Rise Time(Note5)C L=1nF,T J=25°C100600100600ns Fall Time(Note5)C L=1nF,T J=25°C5030050300ns Total Standby Current

Supply Current V IN=35V14201420mA

Note5:These parameters,although ensured over the recommended operating conditions,are not100%tested in production. Note6:Tested at f OSC=40kHz(R T=3.6k W,C T=0.01m F,R D=0W)

Note7:Collector off-state quiescent current measured at pin13with outputs low for UC1525A and high for UC1527A.

UC3525A/27A

PRINCIPLES OF OPERATION AND TYPICAL

CHARACTERISTICS

grounded.The V C terminal is switched to ground by the totem-pole source transistors on alternate oscillator

cycles.drive is controlled by R1-R3.Rapid turn-off times for the power devices are achieved with speed-up capacitors C1and

C2.

rapid charging of power FET Input capacitance while minimizing external

components.

Automatic reset occurs during dead time,when both ends of the primary winding are switched to ground.

PRINCIPLES OF OPERATION AND TYPICAL CHARAC-TERISTIC SHUTDOWN OPTIONS

(See Block Diagram)

Since both the compensation and soft-start terminals (Pins9and8)have current source pull-ups,either can readily accept a pull-down signal which only has to sink a maximum of100μA to turn off the outputs.This is subject to the added requirement of discharging whatever exter-nal capacitance may be attached to these pins.

An alternate approach is the use of the shutdown circuitry of Pin10which has been improved to enhance the avail-able shutdown options.Activating this circuit by applying a positive signal on Pin10performs two functions;the PWM latch is immediately set providing the fastest turn-off signal to the outputs;and a150μA-current sink begins to discharge the external soft-start capacitor.If the shutdown command is short,the PWM signal is termi-nated without significant discharge of the soft-start ca-pacitor,thus,allowing,for example,a convenient implementation of pulse-by-pulse current limiting.Holding Pin10high for a longer duration,however,will ultimately discharge this external capacitor,recycling slow turn-on upon release.

Pin10should not be left floating as noise pickup could conceivably interrupt normal operation.All transitions of the voltage on pin10should be within the time frame of one clock cycle and not repeated at a frequency higher than10clock

cycles.

T T

.D T

D T

REVISION HISTORY

REVISION DATE CHANGE

SLUS191B6/28/05Updated pin10description in the Principles of Operation and Typical

Characteristics Shutdown Options Section.

IMPORTANT NOTICE

Texas Instruments Incorporated and its subsidiaries (TI) reserve the right to make corrections, modifications, enhancements, improvements, and other changes to its products and services at any time and to discontinue any product or service without notice. Customers should obtain the latest relevant information before placing orders and should verify that such information is current and complete. All products are sold subject to TI’s terms and conditions of sale supplied at the time of order acknowledgment.

TI warrants performance of its hardware products to the specifications applicable at the time of sale in accordance with TI’s standard warranty. T esting and other quality control techniques are used to the extent TI deems necessary to support this warranty. Except where mandated by government requirements, testing of all parameters of each product is not necessarily performed.

TI assumes no liability for applications assistance or customer product design. Customers are responsible for their products and applications using TI components. T o minimize the risks associated with customer products and applications, customers should provide adequate design and operating safeguards.

TI does not warrant or represent that any license, either express or implied, is granted under any TI patent right, copyright, mask work right, or other TI intellectual property right relating to any combination, machine, or process in which TI products or services are used. Information published by TI regarding third-party products or services does not constitute a license from TI to use such products or services or a warranty or endorsement thereof. Use of such information may require a license from a third party under the patents or other intellectual property of the third party, or a license from TI under the patents or other intellectual property of TI.

Reproduction of information in TI data books or data sheets is permissible only if reproduction is without alteration and is accompanied by all associated warranties, conditions, limitations, and notices. Reproduction of this information with alteration is an unfair and deceptive business practice. TI is not responsible or liable for such altered documentation.

Resale of TI products or services with statements different from or beyond the parameters stated by TI for that product or service voids all express and any implied warranties for the associated TI product or service and is an unfair and deceptive business practice. TI is not responsible or liable for any such statements. Following are URLs where you can obtain information on other Texas Instruments products and application solutions:

Products Applications

Amplifiers https://www.wendangku.net/doc/0211630918.html, Audio https://www.wendangku.net/doc/0211630918.html,/audio

Data Converters https://www.wendangku.net/doc/0211630918.html, Automotive https://www.wendangku.net/doc/0211630918.html,/automotive

DSP https://www.wendangku.net/doc/0211630918.html, Broadband https://www.wendangku.net/doc/0211630918.html,/broadband

Interface https://www.wendangku.net/doc/0211630918.html, Digital Control https://www.wendangku.net/doc/0211630918.html,/digitalcontrol

Logic https://www.wendangku.net/doc/0211630918.html, Military https://www.wendangku.net/doc/0211630918.html,/military

Power Mgmt https://www.wendangku.net/doc/0211630918.html, Optical Networking https://www.wendangku.net/doc/0211630918.html,/opticalnetwork Microcontrollers https://www.wendangku.net/doc/0211630918.html, Security https://www.wendangku.net/doc/0211630918.html,/security

Telephony https://www.wendangku.net/doc/0211630918.html,/telephony

Video & Imaging https://www.wendangku.net/doc/0211630918.html,/video

Wireless https://www.wendangku.net/doc/0211630918.html,/wireless

Mailing Address:Texas Instruments

Post Office Box 655303 Dallas, Texas 75265