General Description: Power Converter 52kHz WT2575M WT2575 se

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General Description: Power Converter 52kHz WT2575M WT2575 se

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Step-down Voltage Regulator
General Description: Power Converter 52kHz
WT2575M
WT2575 series regulators monolithic integrated circuits that provide active functions step-down (buck) switching regulator, capable driving load with excellent line load regulation. These devices available fixed output voltages 3.3V, output version. Requiring minimum number external components, these regulators simple include internal frequency compensation fixed-frequency oscillator. WT2575 series offers high-efficiency replacement popular three-terminal linear regulators. substantially reduces size heat sink, some cases heat sink required. standard series inductors optimized with WT2575 available from several different manufacturers. This feature greatly simplifies design switch-mode power supplies. Other features include guaranteed tolerance output voltage within specified input voltages output load conditions, ±10% oscillator frequency. External shutdown included, featuring (typical) standby current. output switch includes cycle-by-cycle current limiting, well thermal shutdown full protection under fault conditions.
Features:
3.3V, adjustable output versions Adjustable version output voltage range, 1.23V over line load conditions Guaranteed output current Wide input voltage range Requires only external components 52kHz fixed frequency internal oscillator TTLshutdown capability, powerstandby mode High efficiency Uses readily available standard inductors Thermal shutdownand current limit protection
Applications:
Simple high-efficiency step-down (buck) regulator Efficient pre-regulator linear regulators On-card switching regulators Positive negative converter (Buck-Boost)
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WT2575M
Ordering Information
Part Number WT2575M33 WT2575M50 WT2575M12 WT2575M Voltage 3.3V 5.0V 12.0V Package SOP-8 SOP-8 SOP-8 SOP-8
Packing Type
2,500Units Tape Reel 2,500Units Tape Reel 2,500Units Tape Reel 2,500Units Tape Reel
Connection Diagrams
Surface Mount Package (Top View)
SOP-
2575M
Vout ON/OFF =Year =Weekly
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WT2575M
Typical Application
Unregulated Input +VIN Feedback
WT2575M
Output
100H
Regulated Output Load COUT 680F
100F
1N5822
Noise APPLICATIONS
Unregulated Input +VIN
WT2575M
Feedback Output 1N5822 COUT 220F 0.47H COUT 220F Regulated Output Load
100F
+VIN -This positive input supply switching regulator. suitable input bypass capacitor must present this minimize voltage transients supply switching currents needed regulator. Ground -Circuit ground. Output -Internal switch, voltage this switches between (+VIN VSAT) approximately -0.5V. minimize coupling sensitive circuitry, board copper area connected this should kept minimum. FeedBack -Senses regulated output voltage complete feedback loop. -Allows switching regulator circuit shut down using logic level signals. Pulling this below threshold voltage approximately 1.5V turns regulator wired ground left open, shutdown feature needed, either case regulator will condition.
Functions:
Block Diagram
Unregulated Input
Internal Regulator
ON/OFF
ON/OFF
Feedback
1.0K
Fixed Gain Error
Comparator
Switch Driver Output
VOUT
1.23V Band-Gap Reference
52kHz Oscillator
Reset
Thermal Shutdown
Current Limit
3.3V 1.7K 3.1K Version Open,
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WT2575M
Absolute Maximum Ratings (Note1)
Parameter Maximum Supply Voltage Input voltage Output Voltage Ground (Steady state) Power Dissipation Storage Temperature Range Susceptibility (Human Body Model) Maximum Junction Temperature Rating 0.3+ Internally limited 65150 Unit
Operating Ratings
Temperature Range Supply Voltage 40125
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WT2575M
Electrical Characteristics Specifications with standard type face 25°C
Symbol WT2575M VOUT Parameter Conditions (Note2) (Note Units
System Parameters (Note Test Circuit Figure Output Voltage Efficiency 0.5A ILOAD 12V, ILOAD 0.5A ILOAD 12V, ILOAD 3.234 -3.3 3.366
WT2575M VOUT
System Parameters (Note Test Circuit Figure Output Voltage Efficiency 4.800 -5.0 5.20
WT2575M VOUT
System Parameters (Note Test Circuit Figure 0.5A ILOAD 15V, ILOAD 11.52 -12.0 12.48
Feedback Voltage Efficiency
WT2575M VOUT
System Parameters (Note Test Circuit Figure Feedback Voltage Efficiency 0.5A ILOAD VOUT 12V, ILOAD VOUT 1.193 -1.230 1.267
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WT2575M
Output Voltage Versions Electrical Characteristics (Conditions
Symbol Parameter Conditions (Note2) (Note Units
Device Parameters VSAT ISTBY Feedback Bias Current Oscillator Frequency VSAT Saturation Voltage Duty Cycle(ON) Current Limit Output Leakage Current Quiescent Current Standby Quiescent Current Adjustable Version Only, VOUT= (Note IOUT=2A(Note (Note (Notes Output (Note 6,7) Output -1V(Note (Note (OFF) -6.9
CONTROL VOUT Logic Input Level VOUT Nominal Output Voltage ON/OFF 5V(OFF) Input Current ON/OFF 0V(ON) -1.4 -1.0
Note Absolute Maximum Ratings indicates limits beyond which damage device occur. Operating Ratings indicate conditions which device intended functional, specific performance guaranteed. guaranteed specifications best conditions, Electrical Characteristics. Note limits guaranteed room temperature (standard type face) temperature extremes (bold type face). room temperature limits 100% production tested. limits temperature extremes guaranteed correlation using standard Statistical Quality Control (SQC) methods. Note External components such catch diode, inductor, input output capacitors, voltage programming resistors affect switching regulator system performance. Note Output sourcing current. diode, inductor capacitor connected output pin. Note Feedback removed from output connected Note Feedback removed from output connected +12V 3.3V, version,
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WT2575M
force output transistor switch OFF. Note Note oscillator frequency reduces approximately event output short overload which causes regulated output voltage drop approximately from nominal output voltage. self-protection feature lowers average power dissipation minimum duty cycle from down approximately
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WT2575M
Typical Performance Characteristics
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WT2575M
TEST CIRCUIT LAYOUT GUIDELINES
Careful layout important with switching regulator. Rapidly switching currents associated with wiring inductance generate voltage transients which cause problems. minimize inductance ground loops, lengths leads indicated heavy lines Figure below should kept short possible. Singlepoint grounding indicated Figure ground plane construction should used best results. When using Adjustable version, place programming resistors close possible WT2575M, keep sensitive feedback wiring short.
Figure.1a Fixed Output Voltage Versions
Feedback +VIN
WT2575M FIXED OUTPUT
Output 100F MBR360 COUT 680F VOUT
Unregulated Input
100F
ON/OFF
100F, 75V, Aluminum Electrolytic COUT 680F, 25V, Aluminum Electrolytic Schottky, MBR360 100H, Electronic Corp. TC-101M-3.0A-6826 0.1% 6.12k, 0.1%
Feedback +VIN
WT2575M-ADJ
Output
100H MBR360 COUT 680F
VOUT=5.0V
Unregulated Input
100F
VOUT VREF
VOUT
where VREF 1.23V, between
Figure.1b Adjustable Output Voltage Versions
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WT2575M
INPUT CAPACITOR aluminum tantalum bypass capacitor needed between input ground pin. must located near regulator using short leads. This capacitor prevents large voltage transients from appearing input, provides instantaneous current needed each time switch turns Selecting input capacitor requires consulting manufacturers data sheet maximum allowable ripple current. maximum ambient temperature 40°C, general guideline would select capacitor with ripple current rating approximately load current. ambient temperatures 70°C, current rating load current would good choice conservative design. capacitor voltage rating must least 1.25 times greater than maximum input voltage, often much higher voltage capacitor needed satisfy current requirements. OUTPUT CAPACITOR COUT output capacitor required filter output provide regulator loop stability. impedance Electrolytic solid tantalum capacitors designed switching regulator applications must used. When selecting output capacitor, important capacitor parameters are; Equivalent Series resistance (ESR), ripples current rating, voltage rating, capacitance value. output capacitor, value most important parameter. output capacitor requires value that upper lower limit. output ripple voltage, value needed. This value determined maximum allow able output ripple voltage, typically output voltage. selected capacitor's extremely low, there possibility unstable feedback loop, resulting oscillation output. CATCH DIODE -Buck regulators require diode provide return path inductor current when switch turns off. This must fast diode must located close WT2575 using short leads short printed circuit traces. Because their very fast switching speed forward voltage drop, Schottky diodes provide best performance, especially output voltage applications lower). Ultra fast recovery, High-Efficiency rectifiers also good choice, some types with abrupt turnoff characteristic cause instability problems. INDUCTOR SELECTION -All switching regulators have basic modes operation; continuous discontinuous. difference between types relates inductor current, whether flowing continuously, drops zero period time normal switching cycle. Each mode distinctively different operating characteristics, which affect regulators performance requirements. Most switcher designs will operate discontinuous mode when load current low. WT2575 Simple Switcher family) used both continuous discontinuous modes operation. There formula general applications:
(Note unit voltage unit current
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WT2575M
SOP-8 PACKAGE OUTLINE DIMENSIONS(Unit:
4.915 0.085 3.874 0.064 0.381 0.127
1.395 0.125 5.995 0.205
INDENT
0.215 0.035
0.065 0.035
3.925 0.064
0.840 0.430
1.041 0.178 0.420 0.009 1.270 0.250 3.555 0.225
1.550 0.178
1.391 0.127
0.176 0.074
ORDERING NUMBER
WT2575
Circuit Type Output Voltage 3.3V 5.0V
Package SOP-8
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General Description: Power Converter 52kHz WT2575M WT2575 se

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