MB39A135 1ch DC/DC Converter IC with PFM/PWM Synchronous Rectification Description MB39A135 is 1ch step-down DC/DC converter IC of the current mode N-ch/N-ch synchronous rectification method. It contains the enhanced protection features, and supports the ceramic capacitor. MB39A135 realizes rapid response, high efficiency, and low ripple voltage, and its high-frequency operation enables the miniaturization of inductor and I/O capacitors. Features High efficiency For frequency setting by external resistor : 100 kHz to 1 MHz Error Amp threshold voltage : 0.7 V 1.0 % Minimum output voltage value : 0.7 V Wide range of power-supply voltage : 4.5 V to 25 V PFM/PWM auto switching mode and fixed PWM mode selectable With built-in over voltage protection function With built-in under voltage protection function With built-in over current protection function With built-in over-temperature protection function With built-in soft start/stop circuit without load dependence With built-in synchronous rectification type output steps for N-ch MOS FET Standby current : 0 A (Typ) Small package : TSSOP-16 Applications Digital TV Photocopiers Surveillance cameras Set-top boxes (STB) DVD players, DVD recorders Projectors IP phones Vending machines Consoles and other non-portable devices Cypress Semiconductor Corporation 198 Champion Court San Jose, CA 95134-1709 408-943-2600 Document Number: 002-08410 Rev. *C Revised June 9, 2017 MB39A135 Contents Description ............................................................................. 1 13.6 Setting Method of Over Current Detection Value .. 24 Features .................................................................................. 1 13.7 Selection of Smoothing Inductor ........................... 25 Applications ........................................................................... 1 13.8 Selection of SWFET .............................................. 26 1. Pin Assignment ................................................................ 3 13.9 Selection of Fly-back Diode ................................... 28 2. Pin Descriptions ............................................................... 3 13.10 Selection of Output Capacitor ............................. 29 3. Block Diagram .................................................................. 4 13.11 Selection of Input Capacitor ................................ 30 4. Absolute Maximum Ratings ............................................ 5 13.12 Selection of Boot Strap Diode ............................. 31 5. Recommended Operating Conditions ............................ 6 13.13 Selection of Boot Strap Capacitor ....................... 31 6. Electrical Characteristics ................................................. 7 13.14 Design of Phase Compensation Circuit ............... 31 7. Typical Characteristics .................................................. 10 13.15 1pole-1zero Phase Compensation Circuit ........... 32 8. Function Description ...................................................... 12 13.16 VB pin Capacitor ................................................. 33 8.1 Current Mode .......................................................... 12 13.17 VB Regulator ....................................................... 33 9. Protection Function Table ............................................. 16 13.18 Power Dissipation and the Thermal Design ........ 34 10. I/O Pin Equivalent Circuit Diagram ............................. 17 13.19 Board Layout ....................................................... 35 11. Example Application Circuit ........................................ 19 14. Reference Data ............................................................. 36 12. Parts List ....................................................................... 20 15. Usage Precaution ......................................................... 38 13. Application Note ........................................................... 21 16. Ordering Information .................................................... 38 13.1 Setting Method for PFM/PWM and Fixed 17. RoHS Compliance Information .................................... 38 PWM Modes.............................................................. 21 18. Package Dimensions .................................................... 39 13.2 Cautions at PFM/PWM Mode ................................ 21 19. Major Changes .............................................................. 40 13.3 Setting Method of Output Voltage ......................... 21 Document History ................................................................ 41 13.4 Oscillation Frequency Setting Method ................... 22 Sales, Solutions, and Legal Information ...........................42 13.5 Setting Method of Soft-start time ........................... 23 Document Number: 002-08410 Rev. *C Page 2 of 42