DATASHEET ISL85403 FN8631 Rev.4.00 2.5A Regulator with Integrated High-side MOSFET for Synchronous Buck or Sep 28, 2020 Boost Buck Converter The ISL85403 is a 40V, 2.5A synchronous buck or boost buck Features controller with an integrated high-side MOSFET and low-side Buck mode: input voltage range 3V to 40V (See Input driver. In Buck mode, the ISL85403 supports a wide input Voltage for more details) range of 3V to 40V. In Boost-Buck mode, the input range can be extended down to 2.5V and output regulation can be Boost mode expands operating input voltage lower than maintained when V drops below V , enabling sensitive IN OUT 2.5V (See Input Voltage for more details) electronics to remain on in low input voltage conditions. Selectable Forced PWM mode or PFM mode The ISL85403 has a flexible selection of Forced PWM mode 300A IC quiescent current (PFM, no load) 180A input and PFM mode. In PFM mode, the quiescent input current is as quiescent current (PFM, no load, V tied to AUXVCC) OUT low as 180A (AUXVCC connected to V ). The load boundary OUT Less than 5A (MAX) shutdown input current (IC disabled) between PFM and PWM can be programmed to cover wide applications. Operational topologies - Synchronous buck The low-side driver can either be used to drive an external -Non-synchronous buck low-side MOSFET for a synchronous buck or left unused for a standard non-synchronous buck. The low-side driver can also - Two-stage boost buck be used to drive a boost converter as a preregulator followed - Non-inverting single inductor buck boost by a buck controlled by the same IC, which greatly expands the Programmable frequency from 200kHz to 2.2MHz and operating input voltage range down to 2.5V or lower (See frequency synchronization capability Figure 5). 1% tight voltage regulation accuracy ISL85403 offers robust current protection. It uses peak current mode control with cycle-by-cycle current limiting. It is Reliable overcurrent protection implemented with frequency foldback under current limit - Temperature compensated current sense condition also, the hiccup overcurrent mode ensures reliable - Cycle-by-cycle current limiting with frequency foldback operations under harsh short conditions. - Hiccup mode for worst case short condition The ISL85403 has comprehensive protections against various 20 Ld 4x4 QFN package faults including overvoltage and over-temperature protections. Pb-free (RoHS compliant) Related Literature Applications For a full list of related documents, visit our website: General purpose ISL85403 device page 24V bus power Battery power Point-of-load Embedded processor and I/O supplies 100 95 6V V PGOOD IN EN VIN V IN 90 MODE 12V V IN 85 SYNC BOOT AUXVCC 80 36V V ISL85403 IN 75 VCC V OUT ISL85403 24V V PHASE IN 70 ILIMIT LGATE 65 SS 60 PGND EXT BOOST 55 FB FS 50 SGND COMP 0.1m 1m 10m 100m 1.0 2.5 LOAD CURRENT (A) FIGURE 1. TYPICAL APPLICATION FIGURE 2. EFFICIENCY, SYNCHRONOUS BUCK, PFM MODE, V 5V, T = +25C OUT A FN8631 Rev.4.00 Page 1 of 24 Sep 28, 2020 EFFICIENCY (%)ISL85403 Table of Contents Typical Application Schematics 3 Block Diagram 4 Ordering Information 5 Pin Configuration 5 Functional Pin Descriptions . 5 Absolute Maximum Ratings . 7 Thermal Information . 7 Recommended Operating Conditions 7 Electrical Specifications . 7 Typical Performance Curves . 10 Functional Description 14 Initialization 14 Soft-Start . 14 PWM Control . 14 PFM Mode Operation . 14 Synchronous and Non-Synchronous Buck . 14 AUXVCC Switchover 15 Input Voltage . 15 Output Voltage 15 Output Current 15 2-Stage Boost Buck Converter Operation 16 Oscillator and Synchronization . 17 PGOOD 18 Fault Protection 18 Overcurrent Protection . 18 Overvoltage Protection . 18 Thermal Protection 18 Component Selections 18 Output Capacitors - Buck . 18 Input Capacitors - Buck . 19 Output Inductor - Buck . 19 Low-Side Power MOSFET . 19 Output Voltage Feedback Resistor Divider . 19 Boost Inductor (2-Stage Boost Buck) . 19 Boost Output Capacitor (2-Stage Boost Buck) 19 Loop Compensation Design - Buck 20 PWM Comparator Gain Fm . 20 Current Sampling Transfer Function He(S) . 20 Power Stage Transfer Functions . 20 Loop Compensation Design for 2-Stage Boost Buck and Single-Stage Buck Boost . 22 Layout Suggestions . 22 Revision History 23 Package Outline Drawing 24 FN8631 Rev.4.00 Page 2 of 24 Sep 28, 2020