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). SM8312 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 ( T op View ) 5 SD 4 FB 3 Gnd 2 Output 1 V IN Metal Tab GND Pin Descriptions Name Description VIN Output Gnd FB Operating voltage input Switching output Ground Output voltage feedback control ON/OFF Shutdown TO263-5L V IN OUT FB SD 1 2 3 4 8 7 6 5 GND GND GND GND SD SOP-8 1 V1.0 May 17 ,2007 SAMHOP Microelectronics Corp. 150KHz, 2A PWM Buck Switching Regulator Ordering Information SM8312 SM8312 XX X X Output version -ADJ : Adjustable -33 : 3.3V -50 : 5.0V -12 : 12V Package S: SOP 8 T:TO263-5L Packing Blank : Tube A : Taping Block Diagram SD VIN 200mV Current Source bias 1.235V Reference 2.5V Regulator Start up 220mV + Comp _ Comp + + FB _ Comp + _ Amp Pre-driver 150kHz OSC. Thermal Limit 2 _ 3A Switch Output Gnd V1.0 May 17 ,2007 SAMHOP Microelectronics Corp. 150KHz, 2A PWM Buck Switching Regulator Absolute Maximum Ratings Symbol Parameter Rating SM8312 Unit VCC VSD VFB VOUT PD TST TOP VOP Supply Voltage ON/OFF Pin input voltage Feedback Pin voltage Output voltage to Ground Power dissipation Storage temperature Operating temperature Operating voltage +45 -0.3 to +25 -0.3 to +25 -1 Internally limited -65 to +150 -40 to +125 +4.5 to +25 V V V V W o o 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 Parameter Conditions Min. Typ. Max. Unit IB FOSC Fscp VSAT DC ICL Feedback bias current oscillator frequency Oscillator frequency short circuit protect saturation voltage Max. Duty Cycle(ON) Min. Duty cycle(OFF) current limit Output = 0V Output leakage Output= -1V current Quiescent Current Standby Quiescent Current ON/OFF pin logic input threshold voltage VFB=1.3V (Adjustable version only) 127 110 -10 150 30 1.25 100 0 2.4 2.8 -50 -100 173 173 nA Khz Khz V % of When current limit occurred and VFB