XR75100 XR75100 40V Synchronous Step Down COT Controller 40V Synchronous Step Down COT Controller July 2014 Rev. 1A GENERAL DESCRIPTION The XR75100 is a synchronous step-down controller EEVVAALLUUAATTIIOONN BBOOAARRDD MMAANNUUAALL for point-of load supplies up to 20A. A wide 5.5V to 40V input voltage range allows for single supply operation from industry standard 12V, 18V, and 24V DC and AC rails. With a proprietary emulated current mode Constant On-Time (COT) control scheme, the XR75100 provides extremely fast line and load transient response using ceramic output capacitors. It requires no loop compensation hence simplifying circuit implementation and reducing overall component count. The control loop also provides exceptional load and line regulation and maintains constant operating frequency. A selectable power saving mode allows the user to operate in discontinuous FEATURES mode (DCM) at light current loads thereby 20A Capable Step Down Controller significantly increasing the converter efficiency. Wide 5.5V to 40V Input Voltage Range A host of protection features, including over-current, Integrated high Current 2A/3A Drivers over-temperature, short-circuit and UVLO, help achieve safe operation under abnormal operating 0.6V to 30V Adjustable Output Voltage conditions. Proprietary Constant On-Time Control The XR75100 is available in RoHS compliant, No Loop Compensation Required green/halogen free space-saving 16-pin 3x3 QFN Ceramic Output Cap. Stable operation package. Programmable 200ns-2s On-Time Constant 100kHz-800kHz Frequency Selectable CCM or CCM/DCM Operation DZ MMSZ4685T1G RZ 10k 2-3 --> DCM/CCM C16 0.22uF R5 60.4k 3 3 J1 2 2 24VIN 1 R6 71.5k VIN+ 1 VIN 1-2 --> CCM C1 C2 C3 C4 C5 T3 EN/MODE RLIM 1k 10uF 10uF T4 VIN- RON 19.1k MT, SiR426DP SS CBST 0.1uF 40V, 12.5mOhm CSS RBST 0 Ohm T5 T6 47nF PGOOD 9 4 L1 IHLP-5050FD-5 SS GH 3.3VOUT 10A 1.5uH, 2.5mOhm, 27A VOUT+ VCC 10 3 PGOOD SW R4 10k U1 11 2 XR75100 FB NC FB C6 C7 C8 C9 C10 C11 C12 C13 C14 C15 T1 12 1 RSNB 47uF 47uF 47uF AGND GL T2 17 RFF MB, SiR642DP EXPAD 40 Ohm VOUT- 40V, 3mOhm AGND CSNB T7 T8 CFF R1 1nF 9.09k CIN 0.1uF FB FB R3 R2 VCC VIN CVCC 4.7uF 2k VCC Fig. 1: XR75100 Evaluation Board Schematics Exar Corporation www.exar.com 48720 Kato Road, Fremont CA 94538, USA Tel. +1 510 668-7000 Fax. +1 510 668-7001 13 8 AGND TON 14 7 VIN EN 15 6 VCC ILIM 16 5 PGND BSTXR75100 XR75100 40V Synchronous Step Down COT Controller 40V Synchronous Step Down COT Controller PIN ASSIGNMENT PGND VCC VIN AGND 16 15 14 13 GL 1 12 AGND NC 2 11 FB EXPOSED PAD SW 3 10 PGOOD GH 4 9 SS 5 6 7 8 BST ILIM EN TON Fig. 2: XR75100 Pin Assignment PIN DESCRIPTION Name Pin Number Description 1 Driver output for Low-side N-channel synchronous MOSFET. GL 2 Internally not connected. Leave this pin floating. NC Lower supply rail for high-side gate driver GH. Connect this pin to the junction between the two 3 SW external N-channel MOSFETs. 4 GH Driver output for high-side N-channel switching MOSFET. 5 BST High-side driver supply pin. Connect a 0.1uF bootstrap capacitor between BST and SW. 6 Over-current protection programming. Connect with a resistor to the Drain of the low-side MOSFET. ILIM Precision enable pin. Pulling this pin above 1.9V will turn the IC on and it will operate in Forced 7 EN/MODE CCM. If the voltage is raised above 3.0V then the IC will operate in DCM or CCM depending on load. 8 TON Constant on-time programming pin. Connect with a resistor to AGND. Soft-Start pin. Connect an external capacitor between SS and AGND to program the soft-start rate SS 9 based on the 10uA internal source current. 10 Power-good output. This open-drain output is pulled low when V is outside the regulation. PGOOD OUT Feedback input to feedback comparator. Connect with a set of resistors to VOUT and GND in order 11 FB to program V . OUT 12, 13 AGND Analog ground. Control circuitry of the IC is referenced to this pin. 14 VIN IC supply input. Provides power to internal LDO. 15 The output of LDO. For operation using a 5V rail, VCC should be shorted to VIN. VCC PGND 16 Ground for low side driver Exposed Pad Thermal pad for heat dissipation. Connect to AGND with a short trace. ORDERING INFORMATION Refer to XR75100s datasheet and/or www.exar.com for exact and up to date ordering information. 2014 Exar Corporation 2/7 Rev. 1A