L6730B STMicroelectronics

L6730 L6730B Adjustable step-down controller with synchronous rectification Features Input voltage range from 1.8 V to 14 V Supply voltage range from 4.5 V to 14 V Adjustable output voltage down to 0.6 V with 0.8% accuracy over line voltage and temperature (0C~125C) Fixed frequency voltage mode control t lower than 100 ns HTSSOP20 ON 0% to 100% duty cycle Selectable 0.6 V or 1.2 V internal voltage Applications reference High performance / high density DC-DC External input voltage reference modules Soft-start and inhibit Low voltage distributed DC-DC High current embedded drivers niPOL converters Predictive anti-cross conduction control DDR memory supply Selectable uvlo threshold (5 V or 12 V BUS) DDR memory bus termination supply Programmable high-side and low-side R DS(on) sense overcurrent protection Switching frequency programmable from 100 kHz to 1 MHz Master/slave synchronization with 180 phase shift Pre-bias start up capability (L6730) Table 1. Device summary Selectable source/sink or source only Order codes Package Packing capability after soft-start (L6730) Selectable constant current or hiccup mode L6730 HTSSOP20 Tube overcurrent protection after soft-start (L6730B) L6730TR HTSSOP20 Tape and reel Power Good output with programmable delay L6730B HTSSOP20 Tube Overvoltage protection with selectable L6730BTR HTSSOP20 Tape and reel latched/not-latched mode Thermal shut-down Package: HTSSOP20 December 2009 Doc ID 11938 Rev 3 1/52 www.st.com 52Contents L6730 - L6730B Contents 1 Summary description 4 1.1 Functional description 5 1.2 Application circuit 6 2 Electrical data 7 2.1 Maximum rating . 7 2.2 Thermal data . 7 3 Pin connections and functions 8 4 Electrical characteristics 11 5 Device description . 14 5.1 Oscillator . 14 5.2 Internal LDO . 15 5.3 Bypassing the LDO to avoid the voltage drop with low Vcc . 15 5.4 Internal and external references 16 5.5 Error amplifier 17 5.6 Soft-start 17 5.7 Driver section 20 5.8 Monitoring and protection . 21 5.9 Adjustable masking time . 27 5.10 Multifunction pin (S/O/U L6730) (CC/O/U L6730B) . 27 5.11 Synchronization 28 5.12 Thermal shutdown 29 5.13 Minimum ON-time TON(MIN) 29 5.14 Bootstrap anti-discharging system 30 5.14.1 Fan power supply failure 31 5.14.2 No-sink at zero current operation 31 6 Application details . 33 6.1 Inductor design . 33 2/52 Doc ID 11938 Rev 3