SM8312 SAMHOP Microelectronics Corp. 150KHz, 2A PWM Buck Switching Regulator General Description The SM8312 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 SM8312 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 package and a 5-lead TO-263(U). Features - 3.3V, 5V, 12V and adjustable output versions - Adjustable version output voltage range, 1.23V to 37V +4% max over line and load condition - Available in TO220-5L and TO263-5L 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 - 150KHz 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 Pin Assignments ( Top View ) Pin Descriptions 5 SD 4 FB 3 Gnd 2 Output 1 V IN Name VIN Output Metal Tab GND Gnd TO263-5L V IN 1 8 GND OUT 2 7 GND FB 3 6 GND SD 4 5 GND Description Operating voltage input Switching output Ground FB Output voltage feedback control SD ON/OFF Shutdown SOP-8 1 V1.0 May 17 ,2007 SM8312 SAMHOP Microelectronics Corp. 150KHz, 2A PWM Buck Switching Regulator Ordering Information SM8312 XX X X Package Output version -ADJ : Adjustable -33 : 3.3V -50 : 5.0V -12 : 12V Packing Blank : Tube A : Taping S: SOP 8 T:TO263-5L Block Diagram SD VIN 200mV Current Source bias 1.235V Reference 2.5V Regulator 220mV Start up + Comp _ _ Comp + FB _ Amp _ + Comp + Pre-driver 3A Switch Output 150kHz OSC. 2 Thermal Limit Gnd V1.0 May 17 ,2007 SM8312 SAMHOP Microelectronics Corp. 150KHz, 2A PWM Buck Switching Regulator 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 W -65 to +150 o o TOP Operating temperature -40 to +125 VOP Operating voltage +4.5 to +25 C C V Electrical Characteristics (All Output Voltage Versions) Unless otherwise specified, VIN=12V for 3.3V, 5V, adjustable version and VIN=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 Max. Duty Cycle(ON) Conditions VFB=1.3V (Adjustable version only) of When current limit occurred and VFB <0.55V IOUT=2A no outside circuit VFB=0V force driver on VFB=0V force driver on current limit IL Output = 0V Output leakage Output= -1V current IQ Quiescent Current ISTBY Standby Quiescent Current VIH IH IL Ts ON/OFF pin logic input threshold voltage Max. -50 -100 173 173 30 1.25 70 1.4 1.5 100 2.8 nA Khz Khz V % 0 2.4 Unit 3.3 3.6 A -200 uA -5 -30 mA VFB=12 force driver off 5 10 mA ON/OFF pin=5V VIN=24V 70 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 150 110 ICL VIL Typ. -10 127 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 Min. Duty cycle(OFF) Min. 2.0 200 uA 0.6 1.3 -0.01 -0.1 Tj increasing 175 Tj decreasing 150 3 150 V uA -1 o C V1.0 May 17 ,2007 SM8312 SAMHOP Microelectronics Corp. 150KHz, 2A PWM Buck Switching Regulator Electrical Characteristics (Continued) SM8312-ADJ SM8312-3.3V SM8312-5V SM8312-12V 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 η Efficiency VIN = 12V, ILOAD=2A 75 VOUT Output voltage 5.5V < VIN < 40V 0.2A < ILOAD < 2A 3.3 η Efficiency VIN = 12V, ILOAD=2A 75 VOUT Output voltage 8V < VIN < 40V 0.2A < ILOAD < 2A 5 η Efficiency VIN = 12V, ILOAD=2A 80 VOUT Output voltage 15V < VIN < 40V 0.2A < ILOAD < 2A 12 η Efficiency VIN = 15V, ILOAD = 2A 90 % 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. 4 V1.0 May 17 ,2007 SM8312 SAMHOP Microelectronics Corp. 150KHz, 2A PWM Buck Switching Regulator Typical Performance Characteristics Typical Performance Characteristics Normalized Output Voltage Efficiency V IN =20V, I LOAD=2A Normalized at T J=25oC 100 5.05 EFFICIENCY (%) OUTPUT VOLTAGE CHANGE 5.10 5.00 2A Load 95 90 5V 85 80 4.95 3.3V 75 4.90 -50 -25 0 25 50 75 100 70 125 8 10 35 40 Switch Current Limit 6.5 1.7 1 : -40 oC 2 : 25 oC 3 : 125 oC 1.6 SWITCH CURRENT LIMIT (A) SATURATION VOLTAGE (V) 30 25 JUNCTION TEMPERATURE( C) Switch Saturation Voltage 1.5 1.4 1 1.3 V IN=12V, VOUT =5V 6.0 5.5 5.0 2 3 4.5 2.0 4 3 5 -50 -25 SWITCH CURRENT(A) 20.0 160.0 CURRENT (uA) 200.0 Switch ON 10.0 Switch OFF 5.0 25 50 75 100 125 Shutdown Quiescent Current 25.0 15.0 0 JUNCTION TEMPERATURE(oC) Operating Quiescent Current SUPPLY CURRENT (mA) 20 o JUNCTION TEMPERATURE( oC) 1.2 15 120.0 80.0 1 2 VON/OFF =5V 1 : -40 oC 2 : 25 oC 3 : 125 oC 3 40.0 0.0 -50 -25 0 25 50 75 100 125 0.0 JUNCTION TEMPERATURE( oC) 10 20 30 40 SUPPLY VOLOTAGE (V) 5 V1.0 May 17 ,2007 SM8312 SAMHOP Microelectronics Corp. 150KHz, 2A PWM Buck Switching Regulator ■ Typical Performance Characteristics (Continued) ON /OFF Threshold Voltage 5.0 5.0 4.0 4.0 THRESHOLD VOLTAGE (V) SUPPLY VOLTAGE (V) Minimum Operating Supply Voltage 3.0 2.0 1.0 V OUT =1.23V I LOAD =120mA 3.0 2.0 1.0 0.0 0.0 -50 -25 0 25 50 -50 -25 75 100 125 VIN =40V -40o C≤ T j ≤ 125 o C 90.0 60.0 34.0 17.0 30.0 0.0 1.4 5 10 15 20 22 23 24 -50 -25 25 25 50 75 40.0 8 Output voltage Vo(V) 10 30.0 Adjustable Version Only 10.0 6 4 2 TSC OFF 0 0 25 50 75 125 Thermal protection 50.0 -50 -25 100 JUNCTION TEMPERATURE ( C) Feedback Pin Bias Current 20.0 0 o ON/OFF PIN VOLTAGE (V) 0.0 125 51.0 FREQUENCY (kHz) CURRENT (uA) 75 100 68.0 150.0 BIAS CURRENT (nA) 50 Switch Frequency ON/OFF Pin Current (Sinking ) 0.0 25 JUNCTION TEMPERATURE ( oC) JUNCTION TEMPERATURE ( oC) 120.0 0 100 125 50 75 100 125 150 TSD ON 175 200 JUNCTION TEMPERATURE ( o C) JUNCTION TEMPERATURE ( oC) 6 V1.0 May 17 ,2007 SM8312 SAMHOP Microelectronics Corp. 150KHz, 2A PWM Buck Switching Regulator Typical Application Circuit （A） Fixed Type Circuit FB 12V 4 DC Input SM8312 1 Vin 5 Output Output Load Inductor 3 SD Cin Capacitor 2 3.3V/2A L1 Gnd D1 Schottky Diode Co Capacitor (B) Adjustable Type Circuit R2 R1 FB 12V 4 DC Input Vin SM8312 1 5 Cin 680uF Vout = VFB x (1+ R1/R2 ) 2 L1 Output 3.3V/2A Output Load 68uF 3 Gnd D1 1N5824 Co 1000 uF VFB=1.23V 7 V1.0 May 17 ,2007 SM8312 SAMHOP Microelectronics Corp. 150KHz, 2A PWM Buck Switching Regulator all approximate and there are many factors that can affect these temperatures. Higher ambient temperatures require more heat sinking. The TO-263 surface mount package tab is designed to be soldered to the copper on a printed circuit board. The copper and the board are the heat sink for this package and the other heat producing components, such as the catch diode and inductor. The PC board copper area that the package is soldered to should be at least 0.8 in2, and ideally should have 2 or more square inches of 2 oz. Additional copper area improves the thermal characteristics, but with copper areas greater than approximately 6 in2, only small improvements in heat dissipation are realized. If further thermal improvements are needed, double sided, multilayer PC board with large copper areas and/or airflow are recommended. 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. Output 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 Function Description (Continued) Ground Circuit ground. The SM8312 (TO-263 package) junction temperature rise above ambient temperature with a 2A load for various input and output voltages. This data was taken with the circuit operating as a buck switching regulator with all components mounted on a PC board to simulate the junction temperature under actual operating conditions. This curve can be used for a quick check for the approximate junction temperature for various conditions, but be aware that there are many factors that can affect the junction temperature. When load currents higher than 2A are used, double sided or multilayer PC boards with large copper areas and/or airflow might be needed, especially for high ambient temperatures and high output voltages. 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 can be wired to the ground pin or it can be left open, in either case the regulator will be in the ON condition. For the best thermal performance, wide copper traces and generous amounts of printed circuit board copper should be used in the board layout. (Once exception to this is the output (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. Thermal Considerations The SM8312 is available in two packages, a 8-pin SOP 8 and a 5-pin surface mount TO-263. The SOP 8 package needs a heat sink under most conditions. The size of the heat sink depends on the input voltage, the output voltage, the load current and the ambient temperature. The SM8312 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 SM8312 operating as a buck switching regulator in an ambient temperature of 25oC (still air). These temperature rise numbers are Package thermal resistance and junction temperature rise numbers are all approximate, and there are many factors that will affect these numbers. 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, 8 V1.0 May 17 ,2007 SAMHOP Microelectronics Corp. SM8312 150KHz, 2A PWM Buck Switching Regulator to the PC board and the heat can vary as the input voltage changes. For the inductor, depending on the physical 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. single or double-sided, multilayer board and the amount of solder on the board. 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 Marking Information (2) SOP-8L (1) TO263-5L ( Top view ) Output Type : 8313F-ADJ: ADJ 8313F-33: 3.3V 8313F-50: 5.0V 8313F-12: 12V SM 8313FXX YY WW ~ Logo ID code Xth week : 01~52 Year: "03" = 2003 "04" = 2004 ~ 9 V1.0 May 17 ,2007 SM8312 SAMHOP Microelectronics Corp. 150KHz, 2A PWM Buck Switching Regulator Package Information (1) Package Type: SOP-8L E H C e B A L A1 A2 D θ° y Symbol Dimensions In Millimeters Dimensions In Inches Min. Nom. Max. Min. Nom. Max. A 1.40 1.60 1.75 0.055 0.063 0.069 A1 0.10 - 0.25 0.040 - 0.100 A2 1.30 1.45 1.50 0.051 0.057 0.059 B 0.33 0.41 0.51 0.013 0.016 0.020 C 0.19 0.20 0.25 0.0075 0.008 0.010 D 4.80 4.85 5.05 0.189 0.191 0.199 E 3.80 3.91 4.00 0.150 0.154 0.157 e - 1.27 - - 0.050 - H 5.79 5.99 6.20 0.228 0.236 0.244 L 0.38 0.71 1.27 0.015 0.028 0.050 y - - 0.10 - - 0.004 θ 0° - 8° 0° - 8° Package Information (Continued) 10 V1.0 May 17 ,2007 SM8312 SAMHOP Microelectronics Corp. 150KHz, 2A PWM Buck Switching Regulator (2) Package Type: TO263-5L A C2 L D L1 E F e Symbol C B Dimensions In Millimeters Dimensions In Inches Min. Max. Min. Max. A 4.064 4.826 0.160 0.190 B 0.508 0.991 0.020 0.039 C 0.381 0.737 0.015 0.029 C2 1.143 1.651 0.045 0.065 D 8.382 9.652 0.330 0.380 E 9.652 10.668 0.380 0.420 e 1.702 BSC 0.067 BSC F 6.223 - 0.245 - L 14.605 15.875 0.575 0.625 L1 - 1.676 - 0.066 11 V1.0 May 17 ,2007