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| WEITRON 2A Step-down Voltage Regulator P b Lead(Pb)-Free Power Converter 150kHz General Description: WT2595M The WT2595M is a monolithic integrated circuit that provide all the active functions for a step-down switching regulator, capable of driving a 2A load without additional transistor component. Requiring a minimum number of external component, the board space can be saved easily. The external shutdown function can be controlled by TTL logic level and then come into standby mode. The internal compensation makes feedback control have good line and load regulation without external design. Regarding protected function, thermal shutdown is to prevent over temperature operating from damage, and current limit is against over current operating of the output switch. The WT2595M operates at a switching frequency of 150Khz thus allowing smaller sized filter components than what would be needed with lower frequency switching regulators. Other features include a guaranteed +4% tolerance on output voltage under specified input voltage and output load conditions, and +15% on the oscillator frequency. The output version included fixed 3.3V, 5V, 12V, and an adjustable type. The packages are available in a standard 8-lead SOP8. Features: * 3.3V, 5V, 12V and adjustable output versions * Adjustable version output voltage range, 1.23V to 37V +4% max over line and load condiction * SOP-8 packages * Voltage mode non-synchronous PWM control * Thermal-shutdown and current-limit protection * ON/OFF shutdown control input * Input voltage range up to 40V * Output load current: 2A * 150 kHz fixed frequency internal oscillator * Low power standby mode * Built-in switching transistor on chip Applications: * Simple High-efficiency step-down(buck) regulator * Efficient preregulator for linear regulators * On-card switching regulators * Positive to negative converter * Battery Charger WEITRON hpp://www.weitron.com.tw 1/9 28-Sep-06 WT2595M Ordering Information Part Number WT2595M33 WT2595M50 WT2595M12 WT2595M Voltage 3.3V 5.0V 12.0V ADJ 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- 8 GND GND GND GND Pin Descriptions Name VIN Out Gnd FB Description Operating voltage input Switching output Ground Output voltage feedback control ON/OFF Shutdown 8765 WT YWW 2595M 50 1234 Vin Vout Y WW ON/OFF FB =Year =Weekly ON/OFF http://www.weitron.com.tw WEITRON 2/9 28-Sep-06 WT2595M Typical Application Circuit FB DC Input Vin 1 12V WT2595M -33 4 8 SD 76 5 3 2 Out L1 33uH 3.3V/2A Output Load Inductor Capacitor Cin Gnd Schottky Diode D1 Capacitor Co Function Description Pin Functions +VIN This is the positive input supply for the IC switching regulator. A suitable input bypass capacitor must be present at this pin to minimize voltage transients and to supply the switching currents needed by the regulator. Out Internal switch and power output. The voltage at this pin switches between (+VIN - VSAT) and approximately - 0.5V, with a duty cycle of approximately VOUT / VIN. The PC board copper area connected to this pin should be kept a minimum in order to reduce the coupling sensitivity to the circuitry Ground Circuit ground. Feedback Complete the feedback loop by sensing the regulated output voltage ON /OFF Allows the switching regulator circuit to be shutdown using logic level signals thus dropping the total input supply current to approximately 100uA. Pulling this pin below a threshold voltage of approximately 1.3V turns the regulator on, and pulling this pin above 1.3V (up to a maximum of 25V) shuts the regulator down. If this shutdown feature is not needed, the ON /OFF pin must be wired to the ground pin, in either case the regulator will be in the ON condition. Thermal Considerations The SOP-8 package needs a heat sink under most condictions . The size of the heatsink depends on the input voltage, the output voltage, the load current and the ambient temperature. The WT2595M junction temperature rises above ambient temperature for a 2A load and different input and output voltages. The data for these curves was taken with the WT2595M operating as a buck switching regulator in an ambient temperature of 25oC (still air). These temperature increments are all approximate and are affected by many factors. Some of these factors include board size, shape ,thickness ,position ,location, and even board temperature. Other factors are trace width, total printed circuit copper area, copper thickness , single or double-sided, multi-layer board and amount of solder on the board. Higher ambient temperatures require more heat sinking. For the best thermal performance ,wide copper traces and generous amounts of printed circuit board copper should be used in the board layout. (One exception is the out(switch) pin, which should not have large areas of copper.) Large areas of copper provide the best transfer of heat(lower thermal resistance) to the surrounding air, and moving air lowers the thermal resistance even further. The effectiveness of the PC board to dissipate heat also depends on the size, quantity and spacing of other components on the board , as well as whether the surrounding air is still or moving. Furthermore, some of these components such as the catch diode will add heat to the PC board and heat can vary as the input voltage changes. For the inductor, depending on the phical size, type of core material and the DC resistance, it could either act as a heat sink taking heat away from the board, or it could add heat to the board. http://www.weitron.com.tw WEITRON 3/9 28-Sep-06 WT2595M Block Diagram SD VIN 200mV Current Source bias 1.235V Reference 2.5V Regulator Start up 220mV + Comp _ Comp + + FB _ Comp + Absolute Maximum Ratings Symbol VCC VSD VFB VOUT PD TST TOP VOP Parameter Rating +45 -0.3 to +25 -0.3 to +25 -1 Internally limited -65 to +150 -40 to +125 +4.5 to +25 Unit V V V V W o o Supply Voltage ON/OFF Pin input voltage Feedback Pin voltage Output voltage to Ground Power dissipation Storage temperature Operating temperature Operating voltage http://www.weitron.com.tw WEITRON _ Amp Pre-driver 150kHz OSC. Thermal Limit 4/9 _ 2A Switch Output Gnd C C V 28-Sep-06 WT2595M Electrical Characteristics Unless otherwise specified, VIN=12V for 3.3V, 5V, adjustable version and V IN=24V for the 12V version. ILOAD = 0.2A Symbol IB FOSC Fscp VSAT DC ICL IL IQ ISTBY VIL VIH IH IL Ts Parameter Feedback bias current oscillator frequency Oscillator frequency short circuit protect saturation voltage Max. Duty Cycle(ON) Min. Duty cycle(OFF) current limit Output = 0 Output = 1 Output leakage current Conditions VFB=1.3V (Adjustable version only) Min. Typ. -10 Max. -50 -100 173 173 70 1.4 1.5 Unit nA Khz Khz V % 127 of When current limit occurred and VFB <0.55V IOUT=1.5A no outside circuit VFB=0V force driver on VFB=0V force driver on VFB=12V force driver off peak current no outside circuit VFB=0 force driver on no outside circuit VFB=12 force driver off VIN=24V VFB=12 force driver off ON/OFF pin=5V VIN=24V Low (regulator ON) High (regulator OFF) 2.0 110 150 30 1.25 100 0 2.4 2.8 3.3 3.6 -200 A uA mA mA uA -5 5 70 10 150 200 0.6 1.3 -0.01 -0.1 175 150 -1 Quiescent Current Standby Quiescent Current ON/OFF pin logic input threshold voltage V ON/OFF pin logic VLOGIC=2.5V (OFF) input current ON/OFF pin input current VLOGIC=0.5V (ON) Over temperature shutdown threshold Tj increasing Tj decreasing uA C http://www.weitron.com.tw WEITRON 5/9 28-Sep-06 WT2595M Electrical Characteristics (Continued) Symbol VFB Parameter Output Feedback Efficiency Conditions 5V < VIN < 40V 0.2A < ILOAD < 2A VOUT programmed for 3V VIN = 12V, I LOAD=2A 5.5V < VIN < 40V 0.2A < ILOAD < 2A VIN = 12V, I LOAD=2A 8V < VIN < 40V 0.2A < ILOAD < 2A VIN = 12V, I LOAD=2A 15V < VIN < 40V 0.2A < ILOAD < 2A VIN = 15V, I LOAD = 2A Typ. 1.235 75 3.3 75 5 80 12 90 Limit 1.193/1.18 1.267/1.28 Unit V VMIN VMAX % WT2595M-ADJ WT2595M-3.3V VOUT Output voltage Efficiency 3.168/3.135 3.432/3.465 V VMIN VMAX % V VMIN VMAX % V VMIN VMAX % WT2595M-5V VOUT Output voltage Efficiency 4.8/4.75 5.2/5.25 WT2595M-12V VOUT Output voltage Efficiency 11.52/11.4 12.48/12.6 Specifications with boldface type are for full operating temperature range, the other type are for TJ=25C. http://www.weitron.com.tw WEITRON 6/9 28-Sep-06 WT2595M Typical Performance Characteristics Normalized Output Voltage 5.10 OUTPUT VOLTAGE CHANGE VIN =20V, I LOAD=2A Normalized at TJ=25oC Efficiency EFFICIENCY (%) 5.05 95 90 85 80 75 2A Load 5.00 5V 4.95 3.3V 4.90 -50 -25 0 25 50 75 100 125 70 8 10 15 20 25 30 35 40 JUNCTION TEMPERATURE(oC) JUNCTION TEMPERATURE(oC) Switch Saturation Voltage 1.7 SATURATIO N VOLTAGE (V) Switch Current Limit 8.0 Output voltage Vo(V) 1.6 1.5 1.4 1 : -40 oC 2 : 25 oC 3 : 125 oC 6.0 4.0 1 1.3 1.2 3 2.0 3 4 5 2 2.0 0.0 0 1 2 3 4 5 6 7 Output current Io (A) SWITCH CURRENT(A) Operating Quiescent Current 25.0 SUPPLY CURRENT (mA) Shutdown Quiescent Current 200.0 130.0 CURRENT (uA) 20.0 15.0 10.0 5.0 0.0 -50 -25 0 25 50 75 100 125 JUNCTION TEMPERATURE(oC) Switch ON Switch OFF 100.0 80.0 40.0 0.0 1 2 3 VON/OFF=5V 1 : -40 oC 2 : 25 oC 3 : 125 oC 20 30 40 10 SUPPLY VOLOTAGE (V) http://www.weitron.com.tw WEITRON 7/9 28-Sep-06 WT2595M Typical Performance Characteristics Minimum Operating Supply Voltage 5.0 THRESHOLD VOLTAGE (V) ON/OFF Threshold Voltage 5.0 4.0 3.0 2.0 1.0 0.0 SUPPLY VOLTAGE (V) 4.0 3.0 2.0 1.0 0.0 VOUT=1.23V ILOAD=120mA -50 -25 0 25 50 75 100 125 -50 -25 0 25 50 75 100 125 JUNCTION TEMPERATURE (oC) JUNCTION TEMPERATURE ( oC) ON/OFF Pin Current (Sinking) 150.0 FREQUENCY (kHz) Switch Frequency 200 120.0 CURRENT (uA) VIN=40V -40C TJ 125C 150 100 90.0 60.0 30.0 0.0 50 0.0 1.4 5 10 15 20 22 23 24 25 -50 -25 0 25 50 75 100 o 125 ON/OFF PIN VOLTAGE (V) JUNCTION TEMPERATURE ( C) Feedback Pin Bias Current 50.0 BIAS CURRENT (nA) Output voltage Vo(V) Thermal protection 10 8 6 4 2 0 50 75 100 125 150 175 200 40.0 30.0 20.0 10.0 0.0 -50 -25 0 25 50 75 100 125 Adjustable Version Only JUNCTION TEMPERATURE( oC) JUNCTION TEMPERATURE(o C) http://www.weitron.com.tw WEITRON 8/9 28-Sep-06 WT2595M SOP-8 PACKAGE OUTLINE DIMENSIONS(Unit: mm) Symbol E H L VIEW "A" D 7 (4X) 0.015x45 7 (4X) A A1 A2 B C D E e H L y Dimensions In Millimeters Min. Nom. Max. 1.60 1.75 1.40 0.10 0.25 1.30 0.33 0.19 4.80 3.80 5.79 0.38 0 1.45 0.41 0.20 4.85 3.91 1.27 5.99 0.71 - 1.50 0.51 0.25 5.05 4.00 6.20 1.27 0.10 8 A2 A C y ORDERING NUMBER A1 e B VIEW "A" WT2595 M XX Circuit Type Package SOP-8 Output Voltage 33 : 3.3V 50 : 5.0V 12 : 12V - : ADJ http://www.weitron.com.tw WEITRON 9/9 28-Aug-06 |
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