L5981 STMicroelectronics

L5981 1 A step-down switching regulator Features 1 A DC output current 2.9 V to 18 V input voltage Output voltage adjustable from 0.6 V 250 kHz switching frequency, programmable VFQFPN8 3 mm x 3 mm up to 1 MHz Internal soft-start and inhibit Description Low dropout operation: 100 % duty cycle Voltage feed-forward The L5981 is step-down switching regulator with 1.5 A (min.) current limited embedded power Zero load current operation MOSFET, so it is able to deliver in excess of 1 A Overcurrent and thermal protection DC current to the load depending on the VFQFPN8 3 mm x 3 mm package application condition. The input voltage can range from 2.9 V to 18 V, Applications while the output voltage can be set starting from 0.6 V to V . Having a minimum input voltage of IN Consumer: STB, DVD, DVD recorder, car 2.9 V, the device is suitable also for 3.3 V bus. audio, LCD TV and monitors Requiring a minimum set of external components, Industrial: chargers, PLD, PLA, FPGA the device includes an internal 250 kHz switching Networking: XDSL, modems, DC-DC modules frequency oscillator that can be externally adjusted up to 1 MHz. Computer: optical storage, hard disk drive, printers, audio/graphic cards The VFQFPN8 package with exposed pad allows LED driving reducing the R down to approximately thJA 60 C/W. Figure 1. Application circuit June 2009 Doc ID 13004 Rev 6 1/37 www.st.com 37 Contents L5981 Contents 1 Pin settings 3 1.1 Pin connection 3 1.2 Pin description 3 2 Maximum ratings 4 2.1 Absolute maximum ratings . 4 2.2 Thermal data . 4 3 Electrical characteristics . 5 4 Functional description . 7 4.1 Oscillator and synchronization 8 4.2 Soft-start 10 4.3 Error amplifier and compensation 11 4.4 Over-current protection 12 4.5 Inhibit function . 13 4.6 Hysteretic thermal shutdown 13 5 Application information . 14 5.1 Input capacitor selection 14 5.2 Inductor selection . 15 5.3 Output capacitor selection 16 5.4 Compensation network 17 5.4.1 Type III compensation network . 18 5.4.2 Type II compensation network 22 5.5 Thermal considerations 26 5.6 Layout considerations 27 5.7 Application circuit . 29 6 Package mechanical data 35 7 Order codes . 38 8 Revision history . 39 2/37 Doc ID 13004 Rev 6