WEITRON 2A Step-down Voltage Regulator WT2595M Power Converter 150kHz P b Lead(Pb)-Free General Description: 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 Voltage Package Packing Type WT2595M33 3.3V SOP-8 2,500Units / Tape & Reel WT2595M50 5.0V SOP-8 2,500Units / Tape & Reel WT2595M12 12.0V SOP-8 2,500Units / Tape & Reel ADJ SOP-8 2,500Units / Tape & Reel Part Number WT2595M Connection Diagrams Surface Mount Package (Top View) SOP- 8 GND GND GND GND 8 7 6 5 Name Description VIN Operating voltage input WT YWW 2595M 50 Out Switching output Gnd Ground 1 2 3 4 FB Vin Vout ON/OFF FB Y WW WEITRON Pin Descriptions http://www.weitron.com.tw ON/OFF Output voltage feedback control ON/OFF Shutdown =Year =Weekly 2/9 28-Sep-06 WT2595M Typical Application Circuit FB 12V 3 DC Input Vin 1 WT2595M -33 4 Cin Capacitor 8 SD 2 L1 Out 3.3V/2A 33uH Output Load Inductor 7 6 5 Gnd D1 Schottky Diode Co Capacitor 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. WEITRON http://www.weitron.com.tw 3/9 28-Sep-06 WT2595M Block Diagram SD VIN 200mV Current Source bias 1.235V Reference 2.5V Regulator 220mV Start up + Comp _ _ Comp + _ FB Amp _ + Comp + Pre-driver 2A Switch Output 150kHz OSC. Thermal Limit Gnd Absolute Maximum Ratings Symbol Parameter Rating Unit +45 V VCC Supply Voltage VSD ON/OFF Pin input voltage -0.3 to +25 V VFB Feedback Pin voltage -0.3 to +25 V VOUT Output voltage to Ground -1 V PD TST Power dissipation Internally limited Storage temperature -65 to +150 o TOP Operating temperature -40 to +125 VOP Operating voltage +4.5 to +25 WEITRON http://www.weitron.com.tw 4/9 W o 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 Parameter Feedback bias current FOSC oscillator frequency Fscp Oscillator frequency short circuit protect VSAT saturation voltage DC ICL IL Max. Duty Cycle(ON) Min. Duty cycle(OFF) current limit Output = 0 Output = 1 Output leakage current Conditions VFB=1.3V (Adjustable version only) 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 Quiescent Current VFB=12 force driver off ISTBY Standby Quiescent Current ON/OFF pin=5V VIN=24V VIH IH IL Ts ON/OFF pin logic input threshold voltage Low (regulator ON) High (regulator OFF) ON/OFF pin logic VLOGIC=2.5V (OFF) input current ON/OFF pin input current VLOGIC=0.5V (ON) Over temperature shutdown threshold WEITRON http://www.weitron.com.tw Typ. -10 127 IQ VIL Min. 150 110 -50 -100 173 173 30 1.25 70 1.4 1.5 100 2.4 2.8 3.3 3.6 -200 -5 5 70 2.0 Unit nA Khz Khz V % 0 A uA mA 10 150 200 mA uA 0.6 1.3 -0.01 -0.1 Tj increasing 175 Tj decreasing 150 5/9 Max. -1 V uA °C 28-Sep-06 WT2595M Electrical Characteristics (Continued) WT2595M-ADJ WT2595M-3.3V WT2595M-5V WT2595M-12V Symbol Parameter Conditions Typ. Limit Unit VFB Output Feedback 5V < VIN < 40V 0.2A < ILOAD < 2A VOUT programmed for 3V 1.235 1.193/1.18 1.267/1.28 V VMIN VMAX Efficiency VIN = 12V, I LOAD=2A 75 Output voltage 5.5V < VIN < 40V 0.2A < ILOAD < 2A 3.3 Efficiency VIN = 12V, I LOAD=2A 75 Output voltage 8V < VIN < 40V 0.2A < ILOAD < 2A 5 Efficiency VIN = 12V, I LOAD=2A 80 Output voltage 15V < VIN < 40V 0.2A < ILOAD < 2A 12 Efficiency VIN = 15V, I LOAD = 2A 90 VOUT VOUT VOUT % 3.168/3.135 3.432/3.465 V VMIN VMAX % 4.8/4.75 5.2/5.25 V VMIN VMAX % 11.52/11.4 12.48/12.6 V VMIN VMAX % Specifications with boldface type are for full operating temperature range, the other type are for TJ=25ºC. WEITRON http://www.weitron.com.tw 6/9 28-Sep-06 WT2595M Typical Performance Characteristics Normalized Output Voltage VIN =20V, I LOAD=2A Normalized at TJ=25oC 5.05 EFFICIENCY (%) OUTPUT VOLTAGE CHANGE 5.10 Efficiency 5.00 4.95 90 -50 -25 0 25 50 75 100 80 70 125 5V 85 75 4.90 2A Load 95 3.3V 8 10 Switch Saturation Voltage Output voltage Vo(V) SATURATIO N VOLTAGE (V) 1.4 1 1.2 6.0 4.0 2.0 3 4 3 0.0 5 0 1 SWITCH CURRENT(A) 20.0 130.0 CURRENT (uA) 200.0 Switch ON 10.0 Switch OFF 5.0 3 100.0 80.0 1 2 -25 0 JUNCTION http://www.weitron.com.tw 25 50 75 5 6 7 VON/OFF=5V 1 : -40 oC 2 : 25 oC 3 : 125 oC 3 40.0 0.0 -50 4 Shutdown Quiescent Current 25.0 15.0 2 Output current Io (A) Operating Quiescent Current SUPPLY CURRENT (mA) 40 2 2.0 WEITRON 35 8.0 1.5 1.3 30 25 Switch Current Limit 1 : -40 oC 2 : 25 oC 3 : 125 oC 1.6 20 JUNCTION TEMPERATURE(oC) JUNCTION TEMPERATURE(oC) 1.7 15 100 125 0.0 TEMPERATURE(oC) 10 20 30 40 SUPPLY VOLOTAGE (V) 7/9 28-Sep-06 WT2595M Typical Performance Characteristics ON/OFF Threshold Voltage Minimum Operating Supply Voltage 5.0 THRESHOLD VOLTAGE (V) SUPPLY VOLTAGE (V) 5.0 4.0 3.0 2.0 1.0 0.0 VOUT=1.23V ILOAD=120mA 0 25 50 1.0 25 50 75 100 125 ON/OFF Pin Current (Sinking) Switch Frequency 200 125°C FREQUENCY (kHz) VIN=40V -40°C TJ 30.0 150 100 50 0.0 1.4 5 10 15 20 22 23 24 -50 -25 25 0 25 50 75 100 ON/OFF PIN VOLTAGE (V) JUNCTION TEMPERATURE ( C) Feedback Pin Bias Current Thermal protection 10 40.0 8 30.0 20.0 Adjustable Version Only 10.0 6 4 2 0 -50 -25 0 25 50 75 100 125 50 75 100 125 150 175 200 JUNCTION TEMPERATURE(o C) JUNCTION TEMPERATURE( oC) http://www.weitron.com.tw 125 o 50.0 WEITRON 0 JUNCTION TEMPERATURE ( oC) 60.0 0.0 -50 -25 JUNCTION TEMPERATURE (oC) Output voltage Vo(V) CURRENT (uA) BIAS CURRENT (nA) 2.0 75 100 125 90.0 0.0 3.0 0.0 -50 -25 150.0 120.0 4.0 8/9 28-Sep-06 WT2595M SOP-8 PACKAGE OUTLINE DIMENSIONS(Unit: mm) H E Symbol L VIEW "A" D 0.015x45 7 (4X) C A A2 7 (4X) B VIEW "A" A1 e 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 1.45 0.41 0.20 1.50 0.51 0.25 4.80 3.80 4.85 3.91 5.05 4.00 5.79 0.38 1.27 5.99 0.71 6.20 1.27 - 0.10 8° 0° y ORDERING NUMBER WT2595 M XX Circuit Type Output Voltage 33 : 3.3V 50 : 5.0V 12 : 12V - : ADJ Package SOP-8 WEITRON http://www.weitron.com.tw 9/9 28-Aug-06