HPM10
www.onsemi.com
10
Cradle Charging
• When the hearing aid is inserted to the cradle, it will
charge. While charging, the hearing aid will turn off.
• When the hearing aid is taken out from the cradle, it
will turn on.
Power On/Off
• When the battery is removed, the hearing aid will shut
down
• When the battery is inserted, the hearing aid will turn
on
Battery
• When the battery goes EOL, the hearing aid will
automatically turn off (HPM10 in Deep Sleep Mode)
through two possible mechanisms:
♦ HPM10 goes into Deep Sleep Mode to protect the
battery from over discharge
♦ DSP detects low battery voltage and puts HPM10 in
Deep Sleep Mode through the DS_EN pin
In all modes, when the device is removed from the cradle,
it will either immediately turn on or wait until the pushbutton
is pushed. This means that for the first and second use cases
(Hearing Aid with a Pushbutton and Sealed Battery Door
and Hearing Aid with a Pushbutton and Unsealed Battery
Door), the hearing aid manufacturer will be able to configure
HPM10 to directly switch on or wait for the pushbutton.
In case the hearing aid doesn’t have a pushbutton, once the
battery is fully charged and the hearing aid remains on the
cradle, HPM10 includes a system that compensates the
current drawn by its components detecting the cradle mode
exit. In this case, the hearing aid can be left on the charger
for an extended amount of time without any drain or extra
charge on the battery.
Wakeup on SWIN Pushbutton: In a hearing aid that
contains pushbuttons, HPM10 will wake up the entire
system (VHA active) from Deep Sleep Mode when SWIN
is closed to VBAT for 20 ms minimum.
Wakeup also requires a battery voltage appropriate for a
healthy battery.
• For ZnAir or AgZn: VBAT > 1.1 V and VBAT < 2.2 V
• For Li−Ion: VBAT > 3.0 V
Wakeup on Battery Insertion: Waking up HPM10 on
battery insertion requires an external capacitor from VBAT
to SWIN. The SWIN pull down is a large 2 MW resistor. The
time constant needs to be >200 ms (Cswin = 0.1 mF,
R = 2 Meg).
C
BAT
1uF
C
SWIN
100nF
100n
VBAT
SWIN
HPM10
2MW
Figure 2. External Connection Required for a Proper Wakeup at Battery Insertion
This RC network effectively provide a high pulse of long
enough duration for the wakeup block on HPM10 to latch
ON and enable the DSP. Since the HPM10 latch on delay is
about 20 ms, a pulse of about 200 ms provides a large margin
to ensure that HPM10 reliably turns on.
During Hearing Aid Mode, if the battery discharges to its
end−of−life then the DSP or HPM10 can trigger the Deep
Sleep. Once in Deep Sleep the only way to wake up (in case
there is no button) is to place in the charger.
Wakeup on Removal from Cradle: Waking up HPM10
when the hearing aid is removed from the charger requires
OTP bit “no_button’ to be set high. In this case, VHA will
be turned on.
If the OTP bit “no_button’ is set low, HPM10 will go in
Deep Sleep Mode, and VHA will not be activated.
Shutdown Warning: When the hearing aid is placed in the
Cradle, the output pad WARN signals the DSP that the
power will soon shutdown. This signal is a level−shifted
copy of the analog signal ‘CH_CONN’ (see Figure 3).
The time duration between the moment the WARN signal
is raised to logic “1”, and VHA being switched off, will
allow the hearing aid DSP to get ready for shut down. This
period of time will typically allow the hearing aid DSP to
manage datalogging or mute the audio without glitches. This
time period can be configured in the OTP with a resolution
of 0.5 seconds, with a min value of 0.5 seconds and a max
value of 127.5 seconds.
