Evaluates: MAX8845Z/MAX8845Y
MAX8845Z Evaluation Kit
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10) Connect a digital multimeter (DMM2) from ABO
(MAX8845Z only) to GND.
11) Connect a digital multimeter (DMM3) from SAFEOUT
to GND.
12) Turn on PS1 and then turn on PS2.
13) Remove the shunt on JU1 to set the EV kit in enable
mode.
14) Verify that D2 is emitting light, indicating that POK is
low and input power is valid.
15) Verify that the voltage read by DMM3 is approxi-
mately 4.7V.
16) If the charger is in fast-charge mode, verify that the
ammeter reads approximately 500mA. If the charg-
er is in precharge mode, verify that the ammeter
reads approximately 50mA.
17) Verify that D1 is emitting light, indicating that CHG
is low and the battery charger is on.
Note: If the battery is fully charged, D1 will not emit
light.
18) Verify that the voltage read by DMM2 is approxi-
mately the same voltage read by DMM1.
19) When the battery is fully charged, DMM1 reads 4.2V.
20) Remove the shunt on JU2 and verify that D1 and D2
are not emitting light.
21) Install a shunt on JU2.
22) Turn off the input power supply (PS1).
23) Verify that D2 is not emitting light and the voltage
read by DMM2 is 0V.
24) Install a shunt on JU4.
25) Verify that the voltage read at DMM2 is approxi-
mately the same voltage read by DMM1.
26) Turn on PS1 and increase to 8V.
27) Verify that D1 and D2 are not emitting light and the
voltage read by DMM3 is 0V.
When evaluation of the MAX8845Z EV kit is completed,
use the following steps to power down the EV kit:
1) Install a shunt on JU1.
2) Turn off both power supplies.
3) Remove the battery.
4) Disconnect all test leads from the EV kit.
Detailed Description of Hardware
The MAX8845Z/MAX8845Y chargers use voltage, cur-
rent, and thermal-control loops to charge a single Li+
cell and protect the battery. When a Li+ battery with a
cell voltage below 2.5V is inserted, the MAX8845Z/
MAX8845Y chargers enter a prequalification stage
where it precharges that cell with 10% of the user-pro-
grammed fast-charge current. The CHG indicator is dri-
ven low to indicate entry into the prequalification state.
When the battery voltage exceeds 2.5V, the IC soft-
starts as it enters the fast-charge stage. The fast-
charge current level is programmed through a resistor
from SETI to GND. As the battery voltage approaches
4.2V, the battery current is reduced. If the battery cur-
rent drops to less than the top-off current threshold set
by R
MIN
, the IC enters top-off mode and the CHG indi-
cator goes high impedance, signaling that the battery
is fully charged.
Overvoltage-Protected Output (SAFEOUT)
SAFEOUT is a linear regulator that provides an output
voltage of 4.7V and can be used to supply low-voltage-
rated charging systems. The SAFEOUT linear regulator
turns on when V
IN
≥ 4.25V regardless of EN and is dis-
abled when V
IN
is greater than the overvoltage thresh-
old (7.5V typ).
Battery Pack Detection Input (DETBAT)
DETBAT is a battery pack ID resistor detector that
enables the battery charger if pulled low through a
resistor that is < 51kΩ. By installing a header on JU2,
DETBAT is pulled to ground through R5 (4.7kΩ). If
DETBAT is left unconnected, or the pulldown resistor
is 51kΩ or greater, the battery charger is disabled. If
DETBAT is not used, connect DETBAT to GND for nor-
mal operation.
POK
Output
The open-drain POK output asserts low when 2.35V ≤
V
IN
≤ 7V, (V
IN
- V
BATT
) ≥ 40mV (typ V
IN
rising), and
DETBET is pulled low through a resistor that is < 51kΩ.
POK is high impedance during shutdown. When inter-
facing with a microprocessor logic input, a pullup resis-
tor to the microprocessor’s I/O voltage may be required.
Autobooting Assistant
The MAX8845Z/MAX8845Y contain an autobooting
assistant circuit that generates an enable signal for sys-
tem booting (MAX8845Z = ABO, MAX8845Y = ABO).
For the MAX8845Z, the booting assistant functions as an
internal OR gate (refer to the MAX8845Z/MAX8845Y IC
data sheet). The first input is dependent on the input
supply voltage V
IN
and DETBAT, while the second input
