Named HL7139, it is designed to work from USB PD PSS (power supply, programmable power supply) sources.

Power switches with a switch can be compact and highly efficient, but achieve this high efficiency only at certain precise ratios of input to output voltage. Outside of these ratios, they are far less efficient than inductive converters.

To keep its converter working efficiently – up to 97.6% efficiency when switching to 2: 1 (halves the input voltage) – Halo uses the PPS AC voltage capability of certain USB PD power sources, telling PPS the source delivers twice the desired voltage to the battery terminals. The IC also has a 1: 1 mode where it connects its input directly to the output.

“AC and DC adapter voltage and current [from USB PSS] are programmable in 25mV and 50mA steps via PD communication, “Halo sales engineer Dennis Ha told Electronics Weekly. The application processor can control voltage and current depending on the state of charge of the battery. HL7139 provides loading information for Vin, Iin, Vbat and Ibat [to the host processor] via its 12-bit ADC. Therefore, the input voltage is constantly monitored to be 1x or 2x the battery voltage of the application processor. “

The point of adding a 2: 1 converter between the PSS power supply and the battery is that it doubles the available current, which potentially reduces charging time. Because a 2: 1 switch is not always appropriate, the host processor must make a 2: 1 or 1: 1 decision based on the power supply current and battery characteristics.

The penalty for adding this potential for faster charging, in addition to the cost of components, is additional board space, which will be about 5.2 x 7.2 mm, including IC and all necessary capacitors, according to data sheet HL7139 – package is 2.65 x 2.61 mm 36 bump WLCSP. PCBs may also need to deal with heat dissipation (see later).

Detail for charger with switchable capacitor Halo HL7139

Integrated front MOSFET series with control circuit (QRB on the chart on the left) processes the surge protection at the input and regulates the temperature (via an external thermistor), the input current, the battery current and the detailed battery voltage. These values ​​are programmable.

Since the QRB is on the matrix and regulates the battery voltage (by pre-adjusting the converter 2: 1 or 1: 1), the device will dissipate different amounts of heat if there is no fine input voltage control – if the input source is non-PPS , for example.

Although it is most flexible when working with a host processor through its I2C interface, IC also has standalone modes.

In all cases, the work is from voltages between 3V and 11.7V, corresponding to the specifications of PPS “5V Prog (3.3 – 5.9V) and” 9V Prog “(3.3 – 11.0V) – not the upper limits of 15V Prog or 20V Prog.

The data sheet HL7139 is not publicly available and the section does not yet have a web page. HL7138 will be a similar part, the differences of which have not yet been revealed.


Switched capacitor battery charger for USB PD PPS

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