Diodes Incorporated’s Battery Charging Detector Affords Both Host and Client CircuitryNovember 27, 2019 by Gary Elinoff
Diodes Incorporated claims that the dual-role detector chip enables designers adding USB Type-C interfaces to lower costs and BoM size.
Diodes Incorporated has recently released a battery charging detector IC that addresses the limitations of devices that require either host circuitry or client circuitry.
The PI3USB9201 battery charging detector IC supports both the host and client modes of the USB Type-C interface.
The PI3USB9201 battery charging detector. Image from Diodes Incorporated
To support the bidirectional and reversible flexibility of this new interface, the new chip reports the detection results to the host through a 1MHz I2C interface. A selectable slave address serves to prevent bus conflicts.
The PI3USB9201 can detect charges for a number of SDP, CDP, and DCP-type chargers, including Apple 1A, 2A, 2.4A, and BC1.2.
Details of Host and Client Modes
The unit can be programmed to operate in host mode or client mode through the I2C bus. For both the host and client modes, the results of the detection are reported to the controller—also through the I2C bus.
In host mode, the IC communicates the device's identity as either a standard downstream port (SDP), charging downstream port (CDP), or dedicated charging port (DCP). In accordance with BC 1.2, it does so through the USB D+ and D- pins.
Application diagram of PI3USB9201. Image from Diodes Incorporated
In client mode, the PI3USB9201 conversely monitors the hosts D+ and D- pins to determine the host’s SDP, CDP, or DCP status.
The PI3USB9201 features differential pass-through USB switches, supporting USB switch pass-through in host mode. This permits system wakeup to be initiated through either the mouse or the keyboard.
Power Efficiency for Consumer Electronics
The new battery charging IC is designed for use in battery-powered smartphones, tablets, laptops, and drones. For this reason, it was specifically designed to operate from a supply-voltage range of 2.7V to 5.5V.
And because saving power is a prime concern in mobile devices, the IC draws 200µA in active mode and less than 1µA current in shutdown mode.
The -3dB bandwidth of the USB channel is 2.0GHz. The chip enable time is 500µs maximum.
In host mode, SDP and CDP support data communications. In either of those instances, the USB channel (D+ to USB+ and D- to USB-) is on.
DCP, on the other hand, only supports power, but not data communication over the USB port, so the USB data path is off.
Block diagram for the PI3USB9201. Image from Diodes Incorporated
The I2C Interface
SDA: I2C data
SCL: I2C clock
INTB: Interrupt. Prompts reading of I2C data
ADDR: Selection of up to four unique slave addresses.
ENB: The chip’s system activation
USB Interface and Connector Interface
USB+: D+ signal switch path
USB-: D- signal switch path
D+: In SDP and CDP modes, communicates to the USB-C Connector’s USB+ pin
D-: In SDP and CDP modes, communicates to the USB-C Connector’s USB - pin
INT mask to INTB timing diagram. Image from Diodes Incorporated
The D+ and D- data lines will be shorted to each other with a maximum series impedance of 200Ω.
Environmental and Physical Considerations
The PI3USB9201 is lead-free and is fully RoHS compliant. It is also a halogen- and antimony-free "green" device. The battery charging detector operates over a temperature range of -40°C to +85°C. It is available in a twelve contact 2mm x 2mm QFN package.
What's your experience with host circuitry or client circuitry? Let us know in the comments below.