Features
- Buck mode: input voltage range 3V to 40V
- Boost mode expands operating input voltage lower than 2.5V
- Selectable Forced PWM mode or PFM mode
- 300µA IC quiescent current (PFM, no load); 180µA input quiescent current (PFM, no load, VOUT tied to AUXVCC)
- Less than 5µA (MAX) shutdown input current (IC disabled)
- Operational topologies
- Synchronous buck
- Non-synchronous buck
- Two-stage boost buck
- Non-inverting single inductor buck boost
- Programmable frequency from 200kHz to 2.2MHz and frequency synchronization capability
- ±1% tight voltage regulation accuracy
- Reliable overcurrent protection
- Temperature compensated current sense
- Cycle-by-cycle current limiting with frequency foldback
- Hiccup mode for worst case short condition
- 20 Ld 4x4 QFN package
- Pb-free (RoHS compliant)
Description
The ISL85403 is a 40V, 2. 5A synchronous buck or boost-buck controller with an integrated high-side MOSFET and low-side driver. In Buck mode, the ISL85403 supports a wide input range of 3V to 40V. In Boost-Buck mode, the input range can be extended down to 2. 5V and output regulation can be maintained when VIN drops below VOUT, enabling sensitive electronics to remain on in low input voltage conditions. The ISL85403 has a flexible selection of Forced PWM mode and PFM mode. In PFM mode, the quiescent input current is as low as 180µA (AUXVCC connected to VOUT). The load boundary between PFM and PWM can be programmed to cover wide applications. The low-side driver can either be used to drive an external low-side MOSFET for a synchronous buck or left unused for a standard non-synchronous buck. The low-side driver can also be used to drive a boost converter as a preregulator followed by a buck controlled by the same IC, which greatly expands the operating input voltage range down to 2. 5V or lower. ISL85403 offers robust current protection. It uses peak current mode control with cycle-by-cycle current limiting. It is implemented with frequency foldback under current limit condition; also, the hiccup overcurrent mode ensures reliable operations under harsh short conditions. The ISL85403 has comprehensive protections against various faults including overvoltage and over-temperature protection.
Parameters
| Attributes | Value |
|---|---|
| Topology [Rail 1] | Buck or Boost |
| Outputs (#) | 1 |
| Input Voltage (Min) [Rail 1] (V) | 3 |
| Input Voltage (Max) [Rail 1] (V) | 40 - 40 |
| Output Voltage (Min) [Rail 1] (V) | 0.8 |
| Output Voltage (Max) [Rail 1] (V) | 36 |
| Output Current (Max) [Rail 1] (A) | 2.5 |
| Switching Frequency Range (Typical) (kHz) | 200 - 2200 |
| Control Type | Current Mode |
| Peak Efficiency (%) | 96 |
| IQ [Rail 1] (µA) | 300 |
| SYNCH Capability | Yes |
| Qualification Level | Standard |
| Temp. Range (°C) | -40 to +105°C |
| Simulation Model Available | iSim |
Package Options
| Pkg. Type | Pkg. Dimensions (mm) | Lead Count (#) | Pitch (mm) |
|---|---|---|---|
| QFN | 4.0 x 4.0 x 0.90 | 20 | 0.5 |
Application Block Diagrams
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 | Insulin Pump Insulin pumps provide automatic, precise insulin delivery with CGM integration for better glucose control. |
 | Industrial Programmable Logic Controller (PLC) Flexible embedded programmable logic controller (PLC) designed to integrate any type of interface for end-application needs. |
 | Low Power Backup with Supercapacitor This system uses a supercapacitor to offer reliable power management, as an alternative to batteries. |
 | Smart HVAC Master Actuator Smart HVAC master actuator with AI-driven set points, multi-sensor data, and fail-safe redundancy. |
 | Power System for Smart Power Meter with 4G Module Smart power meter system ensures always-on operation with efficient energy use. |
 | Cloud Gateway Module Cloud gateway module enables secure data transfer, robust communication, and flexible power compatibility. |
 | Smart Grid Fault Indicator Unit Low-power smart grid fault indicator with high-performance MCUs and efficient monitoring. |
Additional Applications
- General purpose
- 24V bus power
- Battery power
- Point of load
- Embedded processor and I/O supplies
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Synchronous Buck Demo Board with 7V to 40V Input Range, 5V 2.5A Output
The ISL85403DEMO1Z demonstration board allows for quick evaluation of the ISL85403 synchronous buck or boost-buck controller in the synchronous buck configuration. It is also used to demonstrate the compact size solution for the wide input voltage range point-of-load (POL) DC/DC converter using... Read More
Buck-Boost EVB with 8V to 40V Input Range, 12V 1A Output
The ISL85403EVAL2Z board allows for quick evaluation of the ISL85403 synchronous buck or boost-buck controller in the non-inverting buck-boost configuration. It is a cost effective solution for the low-power, wide input voltage range point-of-load (POL) application where both stepping up and... Read More
Buck-Boost Last Gasp Power Supply for Energy Meter Reference Design
In this reference design, a supercapacitor is used as a backup power supply. The board allows for quick evaluation of the ISL85403 buck/boost controller in the two-stage boost buck configuration and the ISL9001A low dropout linear regulator. It is a cost-effective design for low-power, wide... Read More
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Support Communities
-
ISL85403 in boost mode only
I need ISL85403 to work only in boost mode. Vin as low as possible, Vout = 16V. I'm guessing highest range for Vin would be close to 16V, since there's no buck operation. I came across the boost-buck circuit, which is "Figure 10. ISL85403EVAL3Z Schematic", taken in this ...
Jan 24, 2022 -
ISL85403 buck-boost configuration, help calculating resistor/inductor values for Vout 5V
... the proper Vout values and it will do the math for me, in here - Idk. Looking at the Figure 10 in "Tips for Using the ISL85403 in Boost-Buck Mode" on p.10 R3 140K from Vout to Fb pin sets the Vout voltage, changing duty cycle of Q1 MOSFET ...
Aug 18, 2021 -
Boost/Buck suggestion
Hi, I am looking for a solution for two different situations, but if possible using the same converter for both (in order to decrease BOM): A) Input 8V - 18V, Output adjustable (by trimmer resistor) 14V-22V @ 800mA. B) Input 8V - 18V, Output fixed at 24V @ 1A. Would the ISL85403 be ...
Sep 17, 2024
Support Communities
