19-4405; Rev 0; 12/08
MAX8845Z Evaluation Kit
General Description
The MAX8845Z evaluation kit (EV kit) is a fully assem-
bled and tested PCB for evaluating the MAX8845Z/
MAX8845Y 28V linear Li+ battery chargers.
The MAX8845Z EV kit features an overvoltage-protect-
ed LDO output (SAFEOUT) for low-voltage-rated USB
or charger inputs in the system, and a battery pack
detection circuit (DETBAT) that disables the IC when
the battery pack is absent. The IC disables charging if
the input sources exceed 7.5V to protect against
unqualified or faulty AC adapters. The MAX8845Z EV kit
also features an adjustable fast-charge current set by
an external resistor (R1) and an adjustable top-off cur-
rent threshold set by an external resistor (R2).
Other features include an active-low control input (EN)
and an active-low input power source detection output
(POK). The IC also contains a booting assistant circuit
that distinguishes input sources and battery connec-
tion, and provides an output signal (MAX8845Z = ABO,
MAX8845Y =
ABO)
for system booting.
To evaluate the MAX8845Y version, order the
MAX8845YETC+ along with the MAX8845ZEVKIT+ and
see the
Evaluating the MAX8845Y
section.
Features
o
CCCV, Thermally Regulated Linear Single-Cell Li+
Battery Charger
o
No External MOSFET, Reverse-Blocking Diode, or
Current-Sense Resistor
o
Programmable Fast-Charge Currents (1A
RMS
max)
o
Programmable Top-Off Current Threshold
o
Input Overvoltage-Protected 4.7V Output
(SAFEOUT) from DC
o
Proprietary Die Temperature Regulation Control
(+115°C)
o
4.25V to 28V Input-Voltage Range with Input
Overvoltage Protection Above +7.5V
o
Low-Dropout Voltage (300mV at 500mA)
o
Input Power-Source Detection Output (POK),
Charge Status Output (CHG), and Charge-Enable
Input (EN)
o
Output for Autobooting (MAX8845Z = ABO,
MAX8845Y =
ABO)
o
Lead(Pb)-Free and RoHS Compliant
Evaluates: MAX8845Z/MAX8845Y
Ordering Information
PART
MAX8845ZEVKIT+
TYPE
EV Kit
+Denotes
lead(Pb)-free and RoHS compliant.
Component List
DESIGNATION
C1
QTY
1
DESCRIPTION
1µF ±10%, 35V X5R ceramic
capacitor (0603)
Taiyo Yuden GMK107BJ105KA
2.2µF ±10%, 10V X5R ceramic
capacitor (0603)
Taiyo Yuden LMK107BJ225KA
Murata GRM188R61A225KE34
0.1µF ±10%, 16V X7R ceramic
capacitor (0402)
TDK C1005X7R1C683K
DESIGNATION
C4
C5
D1, D2
QTY
1
0
2
DESCRIPTION
1µF ±10%, 10V X5R ceramic
capacitor (0402)
Murata GRM155R61A105K
Not installed, capacitor
Red LEDs
Panasonic LNJ208R8ARA
2-pin headers, 0.1in center
Sullins PEC36SAAN
Digi-Key S1012E-36-ND
2.80kΩ ±1% resistor (0402)
C2
1
JU1–JU4
R1
4
1
C3
1
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX8845Z Evaluation Kit
Evaluates: MAX8845Z/MAX8845Y
Component List (continued)
DESIGNATION
R2
R3, R4
R5
R6, R7
R8
QTY
1
2
1
0
1
DESCRIPTION
1.74kΩ ±1% resistor (0402)
200Ω ±5% resistors (0402)
4.7kΩ ±5% resistor (0402)
Not installed, resistors—PCB short
(0402)
200kΩ ±5% resistor (0402)
—
1
U1
1
DESIGNATION
QTY
DESCRIPTION
28V linear Li+ battery charger
(12 Thin QFN-EP*)
Maxim MAX8845ZETC+
(Top Mark: ABL)
PCB: MAX8845Z Evaluation Kit+
*EP
= Exposed pad.
Component Suppliers
SUPPLIER
Digi-Key Corp.
Murata Electronics North America, Inc.
Panasonic Corp.
Sullins Electronics Corp.
Taiyo Yuden
TDK Corp.
PHONE
800-344-4539
770-436-1300
800-344-2112
760-744-0125
800-348-2496
847-803-6100
WEBSITE
www.digikey.com
www.murata-northamerica.com
www.panasonic.com
www.sullinselectronics.com
www.t-yuden.com
www.component.tdk.com
Note:
Indicate that you are using the MAX8845Z when contacting these component suppliers.
Quick Start
Recommended Equipment
•
•
•
•
•
4V to 28V adjustable power supply (PS1) capable of 1A
One 5V power supply (PS2) capable of 100mA
Three digital multimeters (DMM1, DMM2, DMM3)
One 10A ammeter
One single-cell lithium-ion (Li+) battery (not fully
charged)
4) Verify that a shunt is installed on JU2 (DETBAT).
5) Verify that JU3 and JU4 are open and shunts are
not installed.
6) Connect the positive lead of the power supply (PS1)
to the EV kit pad labeled IN. Connect the negative
lead of the power supply to the EV kit pad labeled
GND.
7) Connect the positive lead of the power supply (PS2)
to the EV kit pad labeled VI/O. Connect the negative
lead of the power supply to the EV kit pad labeled
GND.
8) Observe correct Li+ cell polarity. Connect the sin-
gle-cell Li+ battery and 10A ammeter, as shown in
Figure 1. The positive lead of the ammeter must
connect to BATT+ and the negative lead to the pos-
itive terminal of the Li+ battery.
9) Connect a digital multimeter (DMM1) across the Li+
battery. Connect the positive lead of DMM1 to the
positive terminal of the Li+ battery. Connect the
negative lead of DMM1 to the negative terminal of
the Li+ battery and note the battery voltage. If
V
BATT
< 2.5V, the charger starts in precharge
mode. If V
BATT
≥
2.5V, the charger starts up in fast-
charge mode.
Procedure
The MAX8845Z EV kit is a fully assembled and tested
surface-mount board. Follow the steps below and
Figure 1 to set up and verify the MAX8845Z and board
operation:
1) Preset the power supply (PS1) to 5V. Turn off the
power supply.
Do not turn on the power supply
until all connections are completed.
2) Preset the power supply (PS2) to 5V. Turn off the
power supply.
Do not turn on the power supply
until all connections are completed.
3) Verify that a shunt is installed on JU1 (EN) to set the
EV kit in disable mode.
2
_______________________________________________________________________________________
MAX8845Z Evaluation Kit
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.
Evaluates: MAX8845Z/MAX8845Y
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
_______________________________________________________________________________________
3
MAX8845Z Evaluation Kit
Evaluates: MAX8845Z/MAX8845Y
POWER
SUPPLY (PS1) -
+ +5V
- DMM3 +
SAFEOUT
GND
CHG
IN
D1 IS ON WHEN BATTERY CHARGING.
D1
MIN
BATT+
10A
AMMETER
+
MAX8845Z
EVALUATION KIT+
BATT-
Li+
DMM1
-
SETI
DETBAT
SHUNT INSTALLED = BATTERY PRESENT.
SHUNT NOT INSTALLED = BATTERY ABSENT.
SHUNT INSTALLED = ABI CONNECTED TO VI/O.
SHUNT NOT INSTALLED = ABI UNCONNECTED.
ABI
JU2
JU4
JU3
(ABO)
ABO
POK
EN
D2
+ DMM2 -
POWER
- SUPPLY (PS2) +
+5V
D2 IS ON WHEN POWER
SUPPLY IS VALID.
SHUNT INSTALLED = IC DISABLED.
SHUNT NOT INSTALLED = IC ENABLED.
VI/O
JU1
SHUNT INSTALLED = ABO - MAX8845Y ONLY.
SHUNT NOT INSTALLED = ABO - MAX8845Z ONLY.
( ) = MAX8845Y ONLY.
Figure 1. Test Procedure Setup for MAX8845Z EV Kit
Table 1. Jumper Settings (JU1–JU4)
JUMPER
JU1
JU2
DEFAULT
SETTINGS
Installed
Installed
FUNCTION
JU1 connects
EN
(active-low enable input) to VI/O (system supply). Install a shunt on JU1 to disable
the IC.
EN
has an internal pulldown resistor to GND. Remove the shunt from JU1 to enable the IC.
JU2 connects DETBAT (battery pack ID resistor detection input) to GND through R5. Install a shunt
on JU2 to simulate battery present. Remove the shunt on JU2 to simulate battery absent.
Remove the shunt on JU3 to evaluate the MAX8845Z with an active-high autobooting logic output
(ABO). Install a shunt on JU3 to connect
ABO
to the VI/O supply through R8 in order to achieve a
logic-high output on the drain of the internal open-drain MOSFET (MAX8845Y only).
JU4 connects ABI (autobooting input) to VI/O (system supply). Install a shunt on JU4 to connect ABI
to VI/O. Remove the shunt on JU4 to leave ABI unconnected and when ABI is driven by an external
source.
JU3
Not installed
JU4
Not installed
4
_______________________________________________________________________________________
MAX8845Z Evaluation Kit
is an external signal applied to ABI. The first input (POK)
is driven high once DETBAT is pulled low through a
resistor < 51kΩ, 2.35V
≤
V
IN
≤
7V, and (V
IN
- V
BATT
)
≥
40mV (typ V
IN
rising).
The second input signal (ABI) is driven by an external
source (see Table 2). ABI enables an autoboot signal
when a battery is connected at BATT and is indepen-
dent of
POK.
If
POK
is pulled low, the booting assistant
always drives ABO high (MAX8845Z), regardless of ABI.
ABI is pulled to GND through an internal 200kΩ resistor.
If ABI is supplied from an outside exposed pin, an RC
filter (R1/C3 in Figure 2) is required for ESD protection
and noise filtering. If ABI is supplied by a system’s inter-
nal GPIO, or logic, the RC filter is not required.
For the MAX8845Y, the output
ABO
is only dependent
on the state of ABI (Table 2).
ampere of charging current. The output voltage at SETI
is proportional to the charging current:
I
×
R
SETI
V
SETI
=
CHARGE
1016
The voltage at SETI is nominally 1.4V at the selected
fast-charge current, and falls with charging current as
the cell becomes fully charged or as the thermal-
regulation circuitry activates.
Evaluates: MAX8845Z/MAX8845Y
Top-Off Current Threshold Setting
The top-off current threshold is programmed by an
external resistor connected from MIN to GND (R2 in
Figure 2). Use the following equation to determine the
top-off current (I
MIN
):
I
MIN
=
140V
R
MIN
Charger Enable Input
The MAX8845Z EV kit contains an active-low logic input
(EN) used to enable the IC. Drive
EN
low, leave JU1
unconnected, or connect
EN
to GND to enable the
charge-control circuitry. Drive
EN
high to disable the
charge-control circuitry.
EN
has an internal 200kΩ pull-
down resistor.
where I
MIN
is in amperes and R
MIN
is in ohms.
Thermal Regulation
The thermal-regulation loop limits the MAX8845Z/
MAX8845Y die temperature to +115°C by reducing the
charge current, as necessary. This feature not only pro-
tects the IC from overheating, but also allows a higher
charge current without risking damage to the IC.
Fast-Charge Current Setting
The maximum charging current is programmed by an
external resistor connected from SETI to GND (R1 in
Figure 2). Use the following equation to determine the
fast-charge current (I
FAST_CHARGE
):
I
FAST_ CHARGE
=
1400V
R
SETI
Evaluating the MAX8845Y
To evaluate the MAX8845Y version, order the
MAX8845YETC+ along with the MAX8845ZEVKIT+.
Remove U1 and replace with the MAX8845YETC+ (Top
Mark: ABM) and install a shunt on JU3. The MAX8845Y
features an active-low autobooting logic output (ABO)
and requires an external power supply (VI/O on the
MAX8845Z EV kit) to achieve logic-high.
To evaluate the MAX8845Y and board operation, see
Figures 1 and 3 and follow the procedure on the next
page. The MAX8845Y procedure is similar to the
MAX8845Z procedure with a few minor differences.
where I
FAST_CHARGE
is in amperes and R
SETI
is in
ohms. R
SETI
must always be 1.40kΩ or higher due to
the continuous charging current limit of 1A. The voltage
at SETI can be used to monitor the fast-charge current
level. The output current from SETI is 1016µA per
Table 2. Autobooting Output States
ABI
Low
High
Low
Low
High
BATT
Present
Present
Not present
Present
Present
POK
High impedance
High impedance
Low
Low
Low
CHARGER STATE
Shutdown
Shutdown
Fast charge/top off
Fast charge/top off
Fast charge/top off
ABO (MAX8845Z)
Low
High
High
High
High
ABO
(MAX8845Y)
High impedance
Low
High impedance
High impedance
Low
Note:
Present indicates that V
BATT
≥
2V and not present indicates that battery is not connected.
_______________________________________________________________________________________
5
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