HPM10_16 Datasheet, PDF (14/18 Pages) ON Semiconductor – Power Management IC for Hearing Aids

HPM10
load on the VDDP wired supply. This current modulation is
superimposed on the existing current that is used to charge
the battery. State transitions will cause short current
transient steps that need to be ignored by the Primary
Charger data detector. To support the HPM10 usage in a
wireless recharging device, an alternate interface has been
provided. It is composed of pad “CCIF” that is a digital
output duplicating the raw UART signal (i.e. not the
differential encoded data).
The CCIF pin can be configured in the OTP to provide a
static signal that can be used by the system to provide
information on the battery charge as follow:
CCIF Pin State
HI
LO
HI−Z
Corresponding Information
Charge Complete
Fault
Neither
In OTP Burn mode (ATST_EN=HIGH), the CCIF pin is
used as an external reset input active LOW. This reset is
necessary during the OTP READ procedure and it is to
ensure that digital is in a known good state and the OTP
contents have been loaded before doing the read. The CCIF
VBAT
pin, when in input mode, does not have a pull−up or
pull−down resistor so it should not be left floating.
Primary Charger to HPM10 (Receive): The Primary
Charger can use voltage modulation of VDDP to transmit
data to the HPM10. HPM10 uses edge detection and AC
coupling to extract the data easily without a precise
amplitude requirement. This helps relax the requirements on
the drive signal and the loading of the VDDP line by the
Charge Control block. For robust pulse detection, the
rise/fall time of the 200 mV modulation should be less than
100 ms.
Battery Monitoring
HPM10 employs two methods of battery monitoring:
1. In Cradle Mode, the high−precision 10 bit ADC
continuously measures voltage and current to the
battery.
2. In Hearing Aid Mode, the system uses
instantaneous voltage to analog comparators to
perform simple detection of battery chemistry.
Refer to the Hearing Aid Mode section on page 19
for more information.
Figure 5 illustrates how the battery monitoring is done in
a hearing aid system using HPM10.
Veol
Vsafety
Hearing Aid mode
Transition
period
Time
Deep Sleep
Mode
Figure 5. Battery Monitoring for Battery End of Life (EOL)
The hearing aid DSP will have to determine its Veol
threshold, and detect when the VBAT reaches this level.
From this point, the hearing aid DSP will have to manage its
battery EOL procedure (playing a beep users hear, managing
datalogging, etc.) before its toggles the DS_EN pin.
If the DS_EN pin hasn’t been toggled by the hearing aid
DSP and if the hearing aid DSP keeps on drawing power
from the battery, HPM10 will preserve the rechargeable
battery from over−discharging by forcing Deep Sleep Mode
when VBAT reaches Vsafety. In this mode, the VHA supply
is stopped (SAFE_MODE status bit = 0). Vsafety is 2.8 V for
Li−Ion and 1.0 V for AgZn.
Battery Charging Control
While in Cradle Mode, HPM10 controls the charging of
the attached battery. The charging cycle is different for each
battery type, with the charging phase transition points for
each chemistry (voltage, current temperature and time)
stored in OTP and available to the micro−controller in
Cradle mode.
The chemistries that are supported by HPM10 are
Silver−Zinc (AgZn) and Lithium−Ion (Li−ion). While
Zinc−Air (ZnAir) and Nickel−Metal Hydride (Ni−MH)
batteries are detected, they are not charged.
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