L5980

L5980 0.7A step-down switching regulator Features 0.7A DC output current 2.9V to 18V input voltage Output voltage adjustable from 0.6V 250kHz switching frequency, programmable up to 1MHz Internal soft-start and inhibit Low dropout operation: 100% duty cycle Voltage feed-forward Zero load current operation Over current and thermal protection VQFN3x3-8L package VFQFPN8 3x3 Description The L5980 is step down switching regulator with 1A current limited embedded power MOSFET, so it is able to deliver in excess of 0.7A DC current to the load depending on the application condition. The input voltage can range from 2.9V to 18V, while the output voltage can be set starting from 0.6V to VIN. Having a minimum input voltage of 2.9V, the device is suitable also for 3.3V bus. Requiring a minimum set of external components, the device includes an internal 250kHz switching frequency oscillator that can be externally adjusted up to 1MHz. The QFN package with exposed pad allows reducing the RthJA down to approximately 60°C/W. Applications Consumer: STB, DVD, DVD recorder, car audio, LCD TV and monitors Industrial: Chargers, car battery, PLD, PLA, FPGA Networking: XDSL, modems, DC-DC modules Computer: Optical storage, hard disk drive, printers, audio/graphic cards Figure 1. Application circuit October 2007 Rev 2 1/37 www.st.com 37 Contents L5980 Contents 1 Pin settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 1.2 Pin connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2 3 4 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Functional description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 4.1 4.2 4.3 4.4 4.5 4.6 Oscillator and synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Soft-start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Error amplifier and compensation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Over-current protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Inhibit function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Hysteretic thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 5 Application informations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.1 5.2 5.3 5.4 Input capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Inductor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Output capacitor selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5.4.1 5.4.2 Type III compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 Type II compensation network . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23 5.5 5.6 5.7 Thermal considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 6 7 8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33 Order codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36 2/37 Pin settings L5980 1 1.1 Pin settings Pin connection Figure 2. Pin connection (top view) 1.2 Pin description Table 1. N. 1 Pin description Type OUT Regulator output Master/Slave Synchronization. When it is left floating, a signal with a phase shift of half a period respect to the power turn on is present at the pin. When connected to an external signal at a frequency higher than the internal one, then the device is synchronized by the external signal, with zero phase shift. Connecting together the SYNC pin of two devices, the one with higher frequency works as master and the other one as slave; so the two powers turn on have a phase shift of half a period. A logical signal (active high) disable the device. With INH higher than 1.9V the device is OFF and with INH lower than 0.6V the device is ON. Error Amplifier output to be used for loop frequency compensation Feedback input. Connecting the output voltage directly to this pin the output voltage is regulated at 0.6V. To have higher regulated voltages an external resistor divider is required from Vout to FB pin. The switching frequency can be increased connecting an external resistor from FSW pin and ground. If this pin is left floating the device works at its free-running frequency of 250kHz. Ground Unregulated DC input voltage Description 2 SYNCH 3 4 5 INH COMP FB 6 7 8 FSW GND VCC 3/37 Maximum ratings L5980 2 Maximum ratings Table 2. Absolute maximum ratings Parameter Input voltage Output DC voltage Analog pin Inhibit pin Feedback voltage Power dissipation at TA < 60°C Junction temperature range Storage temperature range Value 20 -0.3 to VCC -0.3 to 4 -0.3 to VCC -0.3 to 1.5 1.5. -40 to 150 -55 to 150 W °C °C V Unit Symbol Vcc OUT FSW, COMP, SYNCH INH FB PTOT TJ Tstg 4/37 Electrical characteristics L5980 3 Electrical characteristics TJ=25°C, VCC=12V, unless otherwise specified. Table 3. Symbol Electrical characteristics Values Parameter Operating input voltage range Turn on VCC threshold Turn off VCC threshold Mosfet on resistance Maximum limiting current Test condition Min Typ Max 18 2.9 2.4 x 150 150 1.0 1.3 x 300 1.6 A mΩ V Unit VCC VCCON VCCOFF RDSON ILIM Oscillator (1) (1) (1) 2.9 (1) 225 FSW VFSW D FADJ Switching frequency FSW pin voltage Duty Cycle Adjustable switching frequency RFSW=33kΩ 0 (1) 250 250 1.262 275 kHz x V 100 % kHz x 1000 Dynamic characteristics VFB Feedback voltage 2.9V