Page 36 - EngineerIT April 2022

ELECTRONICS

source. The charger will then ensure the
battery is charged to the battery’s voltage,
current and temperature specifications.
Finally, the micro-controller block
(MCU) organises the communication
between the other ICs. The MCU
communicates with the CC pin detection
IC to determine the power capability
of the power source. Then, the MCU
compares the power source’s capability
with the charger and battery’s power
needs to determine how much current
and voltage the power source should
provide. The MCU communicates the
final power settings back to the CC pin
Figure 4. USB PD design block diagram detection IC to configure the power
source correctly. Once the correct current
PPS allows for countless voltage and current combinations along a USB cable. Designers and voltage are confirmed, the MCU will
who want to use the PPS capability must find a way for a power source and an in-line device configure and enable the charger.
to agree how much power the source should provide. USB PD requires more elements
than legacy USB or standard Type-C
USB-C PD design blocks designs provide. More ICs lead to higher
It is no small task for charging to begin under a discrete USB PD system. A power source, costs and larger solution sizes. It also
such as a wall adapter, connects to the in-line device, such as a phone or power drill, requires a complex firmware design to
through a USB cable. Both devices typically need multiple ICs to implement the back-and- manage the communication between
forth communication to get the power source ready to provide the in-line device power the different elements and meet all the
(Figure 4). USB PD 3.0 standard requirements. The
The CC pin detection IC identifies the cable orientation and source current capability by firmware design alone can create longer
measuring the voltage of the CC pins. This IC also requests the power source’s voltage and development cycles unless a designer
current capabilities and communicates back to the power source when the in-line device has an intimate knowledge of USB
selects a voltage and current. specifications.
The BC1.2 detection IC supports legacy USB adapters. Although newer devices are more
widely adopting USB Type-C, many applications still use older USB specifications. BC1.2- Standalone PD controller
compatible ports have D+/D- pins instead of CC pins to communicate a power source’s Stand-alone PD controllers can help
power capabilities. The BC1.2 detection IC reads the D+/D- pins to configure charging for simplify USB PD designs by having the CC
applications still using legacy USB standards. pin detection, BC1.2 detection and MCU
The charger IC safely and effectively charges the battery on the in-line device. The integrated into one IC. The four-IC design
power source will provide a constant voltage to the in-line device, the charger’s input now becomes just two, which saves board
space and costs.
The most powerful element integrated
into the standalone PD controller is the
embedded MCU, which integrates all
the USB PD 3.0 standard communication
protocol and timing requirements. The
designer no longer needs to spend
development time coming up to speed on
these specifications.
One example of a stand-alone PD
controller is the MAX77958 (Figure 5).
Two unique features of the MAX77958
are the non-volatile memory and the
I C master port that directly controls a
2
companion charger. Both features help
eliminate the need for an external MCU
Figure 5. USB Type-C v1.3 and PD 3.0-compliant stand-alone PD controller and custom firmware development.

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