This product training presentation of the ISL9237 and ISL9238 buck-boost battery charger solutions will give you a brief overview of the device feature set and performances. These products can operate in buck, buck-boost, and boost mode to maintain an accurate output voltage and support USB On-The-Go (OTG) with 5V reverse buck mode from the ISL9237, and full range 5V to 20V OTG from ISL9238.


ISL9237 USB-CTM Buck-Boost Battery Charger

Welcome to the product training presentation of the ISL9237 buck-boost battery charger. This presentation will give you a brief overview of the device feature set and performances.

Emerging USB-C Replaces Existing USB Technology

The year 2015 opened up a new era of power management as high-profile devices began to adopt USB-C ports. A true all-in-one port, it is capable of delivering bidirectional data and power at the same time. USB-C charging requires a fundamental change to the existing power delivery architecture and presents a new challenge to system designers. With a default 5V voltage, the USB-C port is capable of negotiating with the plugged-in device to raise the port voltage to 12V, 20V, or another mutually agreed on voltage, at a mutually agreed current level. The maximum power a USB-C port can deliver is 20V at 5A current, which is 100W of power.

Introducing the ISL9237 USB-C Buck-Boost Battery Charger

The ISL9237 is the industry’s first USB-C buck-boost charger. It provides two-way power delivery while using a single-chip technology that reduces BOM costs and improves efficiency. It can operate in buck, buck-boost, and boost mode to maintain an accurate output voltage and supports USB On-The-Go (OTG) with a 5V reverse buck mode.

Furthermore, it achieves acoustic noise-free operation, superior light load efficiency and fast dynamic response thanks to Intersil’s patented R3 modulation.

ISL9237 USB-C Buck-Boost Battery Charger Typical Application

The ISL9237 has an input voltage range of 3.2V to 23.4V with an output of 2.4V to 13.824V for 1 to 3-cell batteries. Automatic sensing allows the device to enter trickle charging mode when the battery is depleted, and battery learn mode calibrates the battery fuel gauge. Programmable features using the SMBus or I2C interface provide the user with flexibility in their design.

Buck-Boost Charger Solutions

Traditional non-inverting buck-boost circuits use two controllers to achieve a wide output voltage. The converters may be in series or in parallel with a switch to select the active controller. These solutions require two controllers and inductors, cannot operate in the reverse direction, and in the case of the series configuration, are less efficient. Intersil’s latest single chip solution for USB-C addresses all the power requirements while using a single inductor and controller, while also providing additional features.

ISL9237 Buck-Boost Charger with USB On-The-Go (OTG) Function

The ISL9237 consists of four switching FETs and an inductor, as well as a battery connecting FET (BFET). The four switching FETs are grouped into a forward-buck leg and a forward-boost leg. By operating either leg, this topology can operate in forward buck mode or forward boost mode for charging the battery. It can also operate in reverse buck mode to deliver power out of the USB port for charging an external electronic device.

Autonomous Operational Mode Decisions

The device monitors the input and output voltage to determine the correct mode of operation, and switches between each mode to maintain a stable output voltage.

Intersil Solution Eliminates Acoustic Noise

Thanks to the R3 modulator, the ISL9237 delivers the smallest energy transfer per cycle, resulting in no acoustic noise. Competitor parts use larger bursts to transfer energy, resulting in an audible hum.

Inrush Current Control

Another feature of the device is an optional ability to control inrush current. The ASGATE pin of the ISL9237 will drive a FET to control the current for a minimal startup current.

2-Level Adapter Current Limit

The ISL9237 also provides a two-level adapter current limit with fully programmable magnitudes and durations to take advantage of the adapter’s surge current capability.

EVB Efficiency, L = 2.2µH, Fs = 1MHz

Taking a look at the efficiency, the ISL9237 impresses with up to 97% peak efficiency and over 90% efficiency in the majority of cases.

ISL9237 Applications

One of the leading applications for the ISL9237 is the power bank. These devices are a newly emerging product with a two-cell battery that are charged with USB-C and can then be used as a battery pack for other devices either through USB-C or traditional USB-A/B.

There are numerous additional applications for the ISL9237 as more and more products embrace USB-C ports. The ISL9237 is already in many reference designs and used by many customers in production.

Supporting Material

Supporting material for the ISL9237 includes a datasheet, the ISL9237EVAL2Z evaluation board and user’s guide, a white paper, and video. The datasheet includes all relevant information to use the device.


In summary, the ISL9237 is the industry’s first USB-C buck-boost battery charger, capable of delivering buck, buck-boost, and boost for 1 to 3-cell batteries as well as 5V reverse buck-mode for USB On-The-Go. It also provides numerous hardware and programmable features, all at very high efficiencies.