STEVAL-ISA052V1 STMicroelectronics

PM6675S High efficiency step-down controller with embedded 2 A LDO regulator Features Switching section 4.5 V to 28 V input voltage range 0.6 V, 1 % voltage reference Selectable 1.5 V fixed output voltage Adjustable 0.6 V to 3.3 V output voltage 1.237 V 1 % reference voltage available VFQFPN-24 4x4 Very fast load transient response using constant on-time control loop No R current sensing using low side SENSE Description MOSFETs R DS(ON) The PM6675S device consists of a single high Negative current limit efficiency step-down controller and an Latched OVP and UVP independent Low Drop-Out (LDO) linear Soft-start internally fixed at 3 ms regulator. Selectable pulse skipping at light load The Constant On-Time (COT) architecture Selectable No-Audible (33 kHz) pulse skip assures fast transient response supporting both mode electrolytic and ceramic output capacitors. An Ceramic output capacitors supported embedded integrator control loop compensates Output voltage ripple compensation the DC voltage error due to the output ripple. Output soft-end A selectable low-consumption mode allows the LDO regulator section highest efficiency over a wide range of load Adjustable 0.6 V to 3.3 V output voltage conditions. The low-noise mode sets the minimum Selectable 1 Apk or 2 Apk current limit switching frequency to 33 kHz for audio-sensitive applications. Dedicated power-good signal Ceramic output capacitors supported The LDO linear regulator can sink and source up Output soft-end to 2 Apk. Two fixed current limits (1 A-2 A) can be chosen. Applications An active soft-end is independently performed on both the switching and the linear regulators Notebook computers outputs when disabled. Graphic cards Embedded computers Table 1. Device summary Order codes Package Packaging PM6675S Tube VFQFPN-24 4x4 (exposed pad) PM6675STR Tape and reel February 2008 Rev 1 1/53 www.st.com Contents PM6675S Contents 1 Typical application circuit 4 2 Pin settings 5 2.1 Connections 5 2.2 Pin description 6 3 Electrical data 7 3.1 Maximum rating . 7 3.2 Thermal data . 8 3.3 Recommended operating conditions . 8 4 Electrical characteristics . 9 5 Typical operating characteristics . 13 6 Block diagram . 18 7 Device description . 19 7.1 Switching section - constant on-time PWM controller . 20 7.1.1 Constant-On-Time architecture . 22 7.1.2 Output ripple compensation and loop stability 23 7.1.3 Pulse-skip and no-audible pulse-skip modes . 27 7.1.4 Mode-of-operation selection . 29 7.1.5 Current sensing and current limit 30 7.1.6 POR, UVLO and Soft Start 31 7.1.7 Switching section power good signal . 32 7.1.8 Switching section output discharge 32 7.1.9 Gate drivers 33 7.1.10 Reference voltage and bandgap 33 7.1.11 Switching section OV and UV protections . 33 7.1.12 Device thermal protection . 34 2/53