PM6644TR STMicroelectronics

PM6644 350 mA adjustable step-down regulator Datasheet production data Features 4.5 V to 25 V input voltage range Output voltage V : fixed 3.47 V or adjustable OUT 0.9 V to 8 V 350 mA valley current limit DFN10 Constant-on-time control Programmable switching frequency switching regulator can be programmed to Pulse skipping mode (skip mode) at light loads regulate a fixed value of 3.47 V or it can deliver an Independent EN signals adjustable voltage, depending on the FB pin set- Latched OVP and UVP up. Applications Networking power supply Portable applications Microcontroller supply Industrial supply Description The PM6644 is a 350 mA valley current limit step- down regulator capable of delivering an adjustable output voltage in the range between 0.9 V and 8 V. A fixed value of output voltage is also available (3.47 V), saving the external resistor divider. It is housed in a small DFN10 3x3 package. The switching regulator is based on COT (constant-on-time) architecture, that assures fast load transient response the embedded voltage feed-forward provides nearly constant switching frequency operation. The pulse skipping technique increases efficiency at very light load. The switching frequency can be adjusted from 200 kHz to 600 kHz through a simple resistor. The Table 1. Device summary Part number Package Packing PM6644 DFN10 Tube PM6644TR DFN10 Tape and reel June 2012 Doc ID 023203 Rev 1 1/35 This is information on a product in full production. www.st.com 35Contents PM6644 Contents 1 Simplified application schematic . 6 1.1 Pin description 7 1.2 Absolute maximum ratings . 8 1.3 Thermal data . 8 1.4 Recommended operating conditions . 8 1.5 Electrical characteristics . 9 1.6 Typical operating characteristics . 10 2 Device description . 14 2.1 Switching regulator 14 2.1.1 Output voltage set-up . 14 2.1.2 Constant-on-time control (COT) . 14 2.1.3 PWM control . 16 2.1.4 Skip mode management 17 2.1.5 Current sensing and current limit 18 2.1.6 Soft-start and soft-end 19 2.1.7 Monitoring . 19 2.1.8 Overvoltage protection 19 2.1.9 Undervoltage protection . 19 2.1.10 VCC undervoltage . 19 2.1.11 VCC and BYP power management 20 2.1.12 3.3 V linear regulator section (REF3) 20 2.1.13 General fault management: thermal protection . 20 3 Application information . 21 3.1 External component selection . 21 3.1.1 Inductor selection 21 3.1.2 Input capacitor selection 22 3.1.3 Output capacitor selection . 22 3.1.4 Maximum RMS output current 23 4 Typical application configuration V = 8 V 25 OUT 4.1 Test set configuration 25 2/35 Doc ID 023203 Rev 1