HPM10_16 Datasheet, PDF (13/18 Pages) ON Semiconductor – Power Management IC for Hearing Aids

HPM10
Interfaces to Host DSP
In Hearing Aid Mode, the SWOUT pin provides a level
shifted version of the SWIN pin. The SWOUT pin would
typically be connected to the host DSP’s GPIO pin so that the
button on the hearing aid connected to SWIN can also be
used for other functions such as memory select or volume
control.
The DS_EN input pin is provided for the DSP to trigger
Deep Sleep Mode:
• It is active in Hearing Aid Mode only, it is ignored in
Cradle Mode
• It is protected from glitches with a 100 msec de−glitch
circuit
• The host DSP will need to hold the pin high for greater
than 100 usec to put HPM10 into Deep Sleep Mode
• It has a 100 kOhm pull down
• During power−up it will be held low as it will be
connected to the host DSP’s GPIO pin with the
following assumptions:
♦ The GPIO is by default in input mode during power
up
♦ The resistance used for pull−up is greater than 250
KOhm
♦ After boot−up, the host DSP configures the GPIO
pin as an output in a low state
• If the GPIO pull−up resistance is less than 250 kOhm, it
is necessary to add an external resistor to VSS such that
the ratio of pull−up to pull−down resistance is more
than 2.5
DIV3 (Step Down Charge Pump)
In Hearing Aid Mode, the DIV3 step−down charge pump
(CP) is used when Li−Ion batteries are used. The DIV3 CP
uses 2 external capacitors plus 1 decoupling capacitor to
divide the VBAT by a factor of 3. The output impedance of
the charge pump is fixed, and the VHA will track variation
in VBAT.
If VBAT is insufficient to power DIV3 CP, the DIV3 CP
will be shut off. Based on the Li_Ion discharge curve, the
battery is nearly discharged when VBAT<3.1V, and so a
threshold around 3.1 V would be acceptable for the DSP to
use as a turn off threshold. This is equivalent to 3.1/3=1.03 V
on VHA. The HPM10 turn off threshold is much lower
(typically 2.8 V) as a fail−safe in case the DSP is unable to
turn off HPM10.
The DIV3 CP can only be activated when in Hearing Aid
Mode.
The input clock to DIV3 CP comes initially from the
hearing aid oscillator, which also is only active in HA mode.
After the DIV3 starts up and the DSP turns on, if there is
detected a clock signal on the EXT_CLK pad, it will be used
as the master clock in Hearing Aid Mode. When using the
EXT_CLK, the range of frequency can be as much as
−2%/+95% due to the limited division steps.
AgZn Regulator
In Hearing Aid Mode, the AgZn regulator can be used to
limit voltage below 1.5 V when the voltage is above 1.5 V
(first discharge plateau). This regulator will be used in case
the hearing aid DSP input voltage range is limited to 1.5 V.
Disabling this regulator is done by tying the
AGZN_REG_EN pin to ground.
Note that if Zinc−Air or AgZn battery are used and
VBAT < 1.5 V, the AgZn regulator will not be used and the
VBAT will be shorted to the VHA. If VBAT > 1.45 V, the
AgZn regulator is enabled. Hysteresis has been added to all
these thresholds.
If Li−Ion battery is installed, the AgZn Regulator is
disabled and the DIV3 is enabled.
Slave I²C
In Cradle Mode or during debug: HPM10 has a slave I²C
port to allow an external host device to access all the HPM10
internal registers when in Cradle Mode. It is also used for
OTP burning, standalone test, and debug. When in Hearing
Aid Mode, the I²C is off.
Charger Communication Interface (CCIF)
This is a bi−directional interface that will communicate
the status of the charging process in Cradle Mode to the
hearing aid charger and allow user interaction with HPM10.
Normally, once the hearing aid is assembled and the battery
attached, this interface is the only means to monitor the
battery health. The CCIF will communicate with the hearing
aid charger using a superset of the ‘Qi’ (inductive power
standard) based communications protocol using an UART
type encoding. This protocol has been developed for
wireless charging systems. Although this version of HPM10
is only supporting wired charging, this protocol will be used
to facilitate an easier migration to a wireless charging mode.
The data rate is fixed to 2 kHz.
Some of the information sent in this mode is:
• Battery voltage
• Current levels
• Ambient temperature
• Accumulated charge
• Charge mode phase
• Battery chemistry type
• Fault conditions
This communication supports data transfer between the
HPM10 and the Primary Charger. This physical link is the
VDDP power connection. Bidirectional communication
(half−duplex) is supported. The communication from the
HPM10 to Primary is using “load modulation”, where the
VDDP is loaded with a low valued resistor to represent a “0”.
The communication from Primary to HPM10 uses VDDP
voltage modulation.
HPM10 to Primary Charger (Transmit): The CCIF
digital signal (UART type) is converted into a modulated
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