HPM10_16 Datasheet, PDF (15/18 Pages) ON Semiconductor – Power Management IC for Hearing Aids

HPM10
As shown in Figure 6, a charger state machine operates in
five phases to manage the charging process:
• Start−up (SU):
♦ Battery type detection
♦ OTP boot and CRC checking
• Initialization (INIT):
♦ Li−ion pre−charge (trickle)
♦ Li−ion advanced charging algorithms
♦ Over−discharge recovery for AgZn.
• Phase 1 (PH1):
♦ Li−Ion: Maintain a constant current and monitor the
voltage.
♦ AgZn: Lower plateau (Ag₂O) and transition zone
charging region
♦ Exit if the voltage set point has been reached or
time−out has occurred.
• Phase 2 (PH2):
♦ Li−Ion: Maintain a constant voltage and monitor the
current.
♦ AgZn: Upper plateau (AgO) charging region
♦ Exit if the current set point has been reached or
time−out has occurred.
• Completion (CMPLT): Battery charging process is
stopped. Any faults that occurred are stored and
communicated to the external charger.
If ZnAir or Ni−MH is detected, then the state machine
moves to completion phase.
The control loop for controlling the current and voltage
for the charging process consists of monitoring both current
and voltage with the ADC and controlling the current
supplied with a 10−bit current DAC.
ENTER
Start−up
Li−ion
Li−ion
CC
AgZn
AgZn
Zone0
fault
ZnAir
Li−ion
CC
AgZn
Zone1
Li−ion
CV
AgZn
Zone2
ZnAir
Completion
fault
fault
fault
CH_CONN=0
EXIT
SU
INIT
PH1
PH2
CMPLT
Figure 6. Charging Algorithm Diagram Flow
Clocking
HPM10 has two clock sources:
• In Cradle Mode, the CM_CLK clock is coming from an
internal RC oscillator. This clock controls the charging
process (timing and state machine), since an accurate
time reference is required during this state. This clock
is used only in Cradle Mode.
• In Hearing Aid Mode, the HA_CLK is either selected
from either an internal RC oscillator or a divided down
version of an external clock signal, EXT_CLK. The
external clock selection is automatic. If a clock is
detected on EXT_CLK it will override the internal
oscillator. The motivation for this selection is to have a
single clock in the combined system, to avoid pollution
on the supplies that will feed into the audio path. When
the external clock is used, it must be divided down so
the resultant frequency is in the same frequency range
as the internal clock (i.e. 64 kHz −2/+95%. The division
ratios that are possible are divided by 2, 4, 8, 16, 32, 64,
128 and 256 (3 bits). The hearing aid manufacturer is
responsible for setting the appropriate ratio using the
CLKDIV[2:0] pins in order to use an external clock
pin. This can be done from the DSP or can be
connected on the printed circuit board. This clock is
used only in Hearing Aid Mode, and in OTP burn mode
(ATST_EN=VDDIO).
There is no clock active during the Deep Sleep Mode.
Supply Management
There are several forms of supply management on
HPM10:
• Battery Charge Control: This block provides either a
constant current or constant voltage to the attached
battery. Both the current and voltage levels are
programmable when in their respective phases.
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