General Description
The MAX8845Z/MAX8845Y/MAX8845X/MAX8845W are
intelligent, stand-alone constant-current, constant-volt-
age (CCCV), thermally regulated linear chargers
designed for charging a single-cell lithium-ion (Li+) bat-
tery. The MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
integrate a current-sense circuit, MOSFET pass element,
thermal-regulation circuitry, and eliminate the external
reverse-blocking Schottky diode to create the simplest
and smallest charging solutions for handheld equipment.
The ICs control the charging sequence from the pre-
qualification state through constant current fast-charge,
top-off charge, and full-charge indication. Proprietary
thermal-regulation circuitry limits the die temperature
during fast-charging or when the ICs are exposed to
high ambient temperatures, allowing maximum charg-
ing current without damaging the ICs.
The MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
achieve high flexibility by providing adjustable fast-
charge currents (SETI) and an adjustable top-off cur-
rent threshold (MIN) through external resistors. The
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W feature
a booting assistant circuit that distinguishes input
sources and battery connection and provides an
enable signal (ABO—MAX8845Z and ABO—
MAX8845Y/MAX8845X/MAX8845W) for system booting.
The MAX8845Z/MAX8845Y/MAX8845X/MAX8845W also
integrate an overvoltage-protected output (SAFEOUT) for
low voltage-rated USB or charger inputs in system, and a
battery-pack detection circuit (DETBAT) that disables the
charger when the battery pack is absent. Other features
include an active-low control input (EN), an active-low
input power source detection output (POK), and a fully
charged top-off threshold detection output (CHG).
The MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
accept an input supply range from 4.25V (4.4V for
MAX8845W only) to 28V, but disable charging if the
supply voltage exceeds +7.5V (+8.0V for MAX8845X
only) to protect against unqualified or faulty AC
adapters. The ICs operate over the extended tempera-
ture range (-40°C to +85°C) and are available in a com-
pact 12-pin, thermally enhanced thin QFN, 3mm x 3mm
package (0.8mm max height).
Applications
Cellular and Cordless Phones
Smart Phones and PDAs
Digital Still Cameras
MP3 Players
USB Appliances
Charging Cradles and Docks
Bluetooth®Equipment
Features
oCCCV, Thermally Regulated Linear 1-Cell Li+
Battery Charger
oNo External MOSFET, Reverse Blocking Diode, or
Current-Sense Resistor
oProgrammable Fast-Charge Currents (1ARMS max)
oProgrammable Top-Off Current Threshold (MIN)
oInput Overvoltage Protected 4.7V Output
(MAX8845Z/MAX8845Y/MAX8845W) or 4.85V
(MAX8845X) (SAFEOUT)
oProprietary Die Temperature Regulation Control
(+115°C)
o4.25V (4.4V for MAX8845W only) to 28V Input
Voltage Range with Input Overvoltage Protection
Above +7.5V (+8.0V for MAX8845X only)
oLow-Dropout Voltage (300mV at 500mA)
oInput Power-Source Detection Output (POK),
Charge Status Output (CHG), Charge-Enable Input
(EN)
oOutput for Autobooting (ABO—MAX8845Z,
ABO—MAX8845Y/MAX8845X/MAX8845W)
oTiny, 3mm x 3mm 12-Pin Thin QFN Package,
0.8mm Height (max)
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
________________________________________________________________
Maxim Integrated Products
1
19-4340; Rev 1; 9/09
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.
EVALUATION KIT
AVAILABLE
Ordering Information
PART PIN-PACKAGE TOP
MARK
ABO
ACTIVE
STATE
MAX8845ZETC+ 12 Thin QFN-EP* ABL Active high
MAX8845YETC+ 12 Thin QFN-EP* ABM Active low
MAX8845XETC+ 12 Thin QFN-EP* ABQ Active low
MAX8845WETC+ 12 Thin QFN-EP* ABR Active low
Note: All devices are specified over the -40°C to +85°C oper-
ating temperature range.
+
Denotes a lead(Pb)-free/RoHS-compliant package.
*
EP = Exposed pad.
Bluetooth is a registered trademark of Bluetooth SIG.
Typical Operating Circuit and Pin Configurations appear at
end of data sheet.
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN = 5V, VBATT = 4V, RPOK = 1MΩto BATT, EN = unconnected, RSETI = 2.8kΩto GND, VDETBAT = 0, CBATT = 2.2µF, TA= -40°C to
+85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
IN to GND ...............................................................-0.3V to +30V
ABI, BATT, EN, POK, ABO, ABO, CHG, DETBAT, SETI, MIN,
SAFEOUT to GND ................................................-0.3V to +6V
IN to BATT Continuous Current .........................................1ARMS
Continuous Power Dissipation (TA= +70°C)
12-Thin QFN (derate 14.7mW/°C above +70°C)
(multilayer PCB) ......................................................1176.5mW
BATT Short-Circuit Duration .......................................Continuous
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature......................................................+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER CONDITIONS MIN TYP MAX UNITS
Input Supply Voltage Range 0 28 V
4.25 7.00
Input Supply Operating Voltage Range MAX8845W only 4.40 7.00 V
VIN rising, 100mV hysteresis (typ) 7.0 7.5 8.0
Overvoltage Lockout Trip Threshold MAX8845X only 7.5 8.0 8.5 V
Constant current charging
IIN - IBATT, IBATT = 0 0.22 0.50
Constant current charging
IIN - IBATT, IBATT = 500mA 1
IC disabled, VEN = 5V 0.20 0.50
TA = +25°C 0.02
Input Current
VIN = 4V,
VBATT = 4.2V (4.35V for
MAX8845W only) TA = +85°C 0.03
mA
BATT, CHG, POK
Minimum BATT Bypass Capacitance 2.2 µF
VBATT Prequalification Threshold Voltage VBATT rising, 100mV hysteresis (typ) 2.3 2.5 2.7 V
4.175 4.200 4.225
IBATT = 0 TA = -40°C to +85°C 4.158 4.200 4.242
4.324 4.350 4.376
Battery Regulation Voltage
MAX8845W only 4.306 4.350 4.394
V
Regulator Dropout Voltage (VIN - VBATT)V
BATT = 4.1V, IBATT = 425mA 260 mV
VIN = 0 to 4V,
VBATT = 4.2V (4.35V for MAX8845W only) 510
BATT Input Current
IC disabled 3
µA
Current-Sense Amplifier Gain (IBATT to ISETI)I
BATT = 500mA 1016 µA/A
TA = 0°C to +85°C 460 500 540
VBATT = 3.5V,
RSETI = 2.8kΩTA = -40°C to +85°C 425 500 575
Fast-Charge Current
VBATT = 3.5V,
RSETI = 14kΩTA = 0°C to +85°C 85 100 115
mA
CHG Top-Off Threshold IBATT falling, battery is charged
RMIN = 1.75kΩ106 mA
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
_______________________________________________________________________________________ 3
PARAMETER CONDITIONS MIN TYP MAX UNITS
CHG Hysteresis IBATT rising after top-off is detected,
RMIN = 1.75kΩ38 mA
CHG Detection Delay IBATT falls below top-off threshold 4.0 6.2 10.7 ms
Prequalification Charge Current
Percentage of the fast-
charge current, VBATT
= 2.2V
TA = 0°C to +85°C 5 10 15 %
CHG, POK Output Low Threshold IPOK = 5mA , ICHG = 5mA 0.4 V
TA = +25°C 1
CHG, POK Output High Leakage Current VPOK = 5.5V,
V CHG = 5.5V TA = +85°C 0.01 µA
VIN rising 40
POK Threshold VIN - VBATT VIN falling 30 mV
DETBAT, SAFEOUT
DETBAT Logic-Input Low Threshold 0.4
DETBAT Logic-Input High Threshold 1.3 V
DETBAT Pullup Resistor DETBAT to VL = 3V 470 kΩ
Minimum SAFEOUT Bypass Capacitance 1 µF
ISAFEOUT = 30mA, VIN = 5V, TA = 0°C to
+85°C (MAX8845Z/MAX8845Y/MAX8845W) 4.5 4.7 4.9
SAFEOUT Regulated Output ISAFEOUT = 20mA, VIN = 5V, TA = 0°C to
+85°C (MAX8845X) 4.75 4.85 5.0
V
SAFEOUT Current Limit 100 mA
EN, ABI, ABO, ABO
EN, ABI Internal Pulldown Resistor 100 200 400 kΩ
EN Logic-Input Low Threshold 4.25V (4.4V for MAX8845W only) ≤ VIN ≤ 7V 0.4 V
EN Logic-Input High Threshold 4.25V (4.4V for MAX8845W only) ≤ VIN ≤ 7V 1.3 V
ABI Logic-Input Low Threshold VBATT = 4V, VIN = 0 0.4 V
ABI Logic-Input High Threshold VBATT = 4V, VIN = 0 1.3 V
ABO Output Low Threshold (MAX8845Y/
MAX8845X/MAX8845W) Open drain, IABO(SINK) = 1mA 0.4 V
ABO Output High Threshold (MAX8845Y/
MAX8845X/MAX8845W) Open drain, 100kΩ pullup to BATT VBATT -
0.4V V
ABO Output Low Threshold
(MAX8845Z) IABO(SINK) = 1mA 0.4 V
ABO Output High Threshold (MAX8845Z) IABO(SOURCE) = 1mA VBATT -
0.4V V
THERMAL
Die Temperature Regulation Threshold 115 °C
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 5V, VBATT = 4V, RPOK = 1MΩto BATT, EN = unconnected, RSETI = 2.8kΩto GND, VDETBAT = 0, CBATT = 2.2µF, TA= -40°C to
+85°C, unless otherwise noted. Typical values are at TA= +25°C.) (Note 1)
Note 1: Specifications are 100% production tested at TA= +25°C. Limits over the operating temperature range are guaranteed by
design and characterization.
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
4 _______________________________________________________________________________________
Typical Operating Characteristics
(VIN = 5V, VBATT = 4V, RPOK = RCHG = 200kΩto 5V, EN = unconnected, RSETI = 2.8kΩto GND, RMIN = 1.74kΩto GND, RDETBAT =
4.7kΩto GND, CBATT = 2.2µF, TA= +25°C, unless otherwise noted.)
0
0.3
0.2
0.1
0.5
0.4
0.9
0.8
0.7
0.6
1.0
0 4 8 12 16 20 24 28
SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX8845Z/Y/X/W toc01
INPUT VOLTAGE (V)
SUPPLY CURRENT (mA)
VEN = 0,
IBATT = 0
VIN RISING
0
0.2
0.1
0.4
0.3
0.5
0.6
010155 202530
DISABLED MODE SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX8845Z/Y/X/W toc02
INPUT VOLTAGE (V)
SUPPLY CURRENT (µA)
VEN = 5V
0
200
100
400
300
600
500
700
900
800
1000
0 1.0 1.5 2.00.5 2.5 3.0 3.5 4.0 4.5
CHARGE CURRENT
vs. BATTERY VOLTAGE
MAX8845Z/Y/X/W toc03
BATTERY VOLTAGE (V)
CHARGE CURRENT (mA)
0
200
100
400
300
500
600
012164 8 20 24 28
CHARGE CURRENT
vs. INPUT VOLTAGE
MAX8845Z/Y/X/W toc04
INPUT VOLTAGE (V)
CHARGE CURRENT (mA)
0
300
200
100
400
500
600
700
800
900
1000
0 200100 300 400 500 600
CHARGE CURRENT
vs. INPUT VOLTAGE HEADROOM
MAX8845Z/Y/X/W toc05
VIN - VBATT (mV)
CHARGE CURRENT (mA)
VBATT = 4V,
VIN RISING
0
1.5
1.0
0.5
2.5
2.0
4.5
4.0
3.5
3.0
5.0
0 4 8 1216202428
SAFEOUT OUTPUT VOLTAGE
vs. INPUT VOLTAGE
MAX8845Z/Y/X/W toc06
INPUT VOLTAGE (V)
SAFEOUT VOLTAGE (V)
ISAFEOUT = 1mA
0
1.5
1.0
0.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
04020 60 80 100
SAFEOUT OUTPUT VOLTAGE
vs. LOAD CURRENT
MAX8845Z/Y/X/W toc07
LOAD CURRENT (mA)
SAFEOUT VOLTAGE (V)
40µs/div
STARTUP INTO PRECHARGE
IBATT
VIN
100mA/div
5V/div
5V/div
5V/div
MAX8845Z/Y/X/W toc08
VEN
VPOK
0
0
0
0
40µs/div
SHUTDOWN
(FAST-CHARGE TO SHUTDOWN)
IBATT
VIN
500mA/div
5V/div
5V/div
5V/div
MAX8845Z/Y/X/W toc09
VEN
VPOK
0
0
0
0
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
_______________________________________________________________________________________ 5
Typical Operating Characteristics (continued)
(VIN = 5V, VBATT = 4V, RPOK = RCHG = 200kΩto 5V, EN = unconnected, RSETI = 2.8kΩto GND, RMIN = 1.74kΩto GND, RDETBAT =
4.7kΩto GND, CBATT = 2.2µF, TA= +25°C, unless otherwise noted.)
-1.0
-0.4
-0.6
-0.8
-0.2
0
0.2
0.4
0.6
0.8
1.0
-40 10-15 35 60 85
BATTERY REGULATION ACCURACY
vs. AMBIENT TEMPERATURE
MAX8845Z/Y/X/W toc10
AMBIENT TEMPERATURE (°C)
BATTERY REGULATION ACCURACY (%)
IBATT = 0
FAST-CHARGE CURRENT
vs. RSETI
MAX8845Z/Y/X/W toc11
RSETI (kΩ)
FAST-CHARGE CURRENT (mA)
100010010
10
100
1000
1
1 10,000
TOP-OFF CURRENT THRESHOLD
vs. 1/RMIN (kΩ)
MAX8845Z/Y/X/W toc12
1/RMIN (kΩ)
TOP-OFF CURRENT THRESHOLD (mA)
100
150
200
250
300
350
400
450
500
550
600
50
0.4 0.6 0.8 2.01.0
0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9
1.2 1.4 1.6 1.8
TOP-OFF CURRENT RISING
TOP-OFF CURRENT FALLING
0
200
100
400
300
600
500
700
-40 0 20-20 40 60 80 100
CHARGE CURRENT
vs. AMBIENT TEMPERATURE
MAX8845Z/Y/X/W toc13
AMBIENT TEMPERATURE (°C)
CHARGE CURRENT (mA)
VBATT = 4V
VBATT = 3.2V
RSETI = 2.8kΩ
4µs/div
AUTOBOOT ENABLED BY ABI SIGNAL
(MAX8845Z)
VABI
VIN
5V/div
5V/div
5V/div
5V/div
MAX8845Z/Y/X/W toc14
VBATT
VABO
0
0
0
0
20µs/div
AUTOBOOT ENABLED BY INPUT VOLTAGE
(MAX8845Z)
VABI
VIN
5V/div
5V/div
5V/div
5V/div
MAX8845Z/Y/X/W toc15
VBATT
VABO
0
0
0
0
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
6 _______________________________________________________________________________________
Pin Description
PIN
MAX8845Z
MAX8845Y/
MAX8845X/
MAX8845W
NAME FUNCTION
1 1 SETI
Charge-Current Program and Fast-Charge Current Monitor. Output current from SETI is
1016µA per ampere of battery charging current. Set the charging current by connecting
a resistor (RSETI in Figure 3) from SETI to GND. IFAST-CHARGE = 1400V/RSETI. To
configure the MAX8845Z/MAX8845Y/MAX8845X/MAX8845W as a USB charger, see
Figure 5.
2 2 DETBAT
Battery Pack ID Resistor Detection Input. If DETBAT is pulled low through a pulldown
resistor less than 51kΩ the charger is enabled. If DETBAT is left unconnected, the
charger is disabled.
3 3 ABI Autobooting External Input. See the Autobooting Assistant section and Table 1 for
autobooting conditions. ABI is pulled to GND through an internal 200kΩ resistor.
44EN Active-Low, Logic-Level Enable Input. Drive EN high to disable charger. Drive EN low or
leave unconnected for normal operation. EN has an internal 200kΩ pulldown resistor.
5 5 GND Ground. Connect GND and the exposed pad to a large copper ground plane for
maximum power dissipation. Connect GND to the exposed pad directly under the IC.
66POK
Active-Low, Input Voltage Status Indicator. POK is an open-drain output that asserts low
when 2.35V < VIN < 7V (7.5V for MAX8845X only) and (VIN - VBATT) > 40mV. If VIN >
+7.5V (+8.0V for MAX8845X only) or VBATT > VIN the IC is shut down and POK becomes
high impedance. Connect a pullup resistor to the microprocessor’s I/O voltage when
interfacing with a microprocessor logic input.
7 — ABO Active-High, Autobooting Logic Output. See the Autobooting Assistant section and Table
1 for autobooting conditions.
—7ABO Active-Low, Open-Drain Logic Output. See the Autobooting Assistant section and Table
1 for autobooting conditions.
8 8 BATT Li+ Battery Connection. Bypass BATT to GND with a 2.2µF ceramic capacitor.
99MIN
Top - O ff C ur r ent Thr eshol d P r og r am m ab l e Inp ut. IM IN
( m A) fal l i ng = 148V /RM IN
( kΩ ) + 22
( m A) .
10 10 CHG
Active-Low, Charging Indicator. CHG is an open-drain output that is pulled low once
charging begins. CHG is high impedance when the battery current drops below MIN, or
when the IC is disabled. Connect a pullup resistor to the microprocessor’s I/O voltage
when interfacing with a microprocessor logic input.
11 11 IN Input Supply Voltage. Bypass IN to GND with a 1µF or larger ceramic capacitor to
improve line noise and input transient rejection.
12 12 SAFEOUT
4.7V (MAX8845Z/MAX8845Y/MAX8845W) or 4.85V (MAX8845X) Regulated LDO Output
with Input Overvoltage Protection. Bypass SAFEOUT to GND with a 1µF or larger
ceramic capacitor. SAFEOUT can be used to supply low voltage-rated USB systems.
—— EP
Exposed Pad. Connect the exposed pad to a large ground plane for maximum power
dissipation. Connect GND to the exposed pad directly under the IC.
Detailed Description
The MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
chargers use voltage, current, and thermal-control
loops to charge a single Li+ cell and protect the battery
(Figure 1). When a Li+ battery with a cell voltage below
2.5V is inserted, the MAX8845Z/MAX8845Y/MAX8845X/
MAX8845W chargers enter a prequalification stage
where it precharges that cell with 10% of the user-pro-
grammed fast-charge current (Figure 2). The CHG indi-
cator is driven low to indicate entry into the prequalifi-
cation state. When the battery voltage exceeds 2.5V,
the charger 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 charging current is
reduced. If the battery current drops to less than the
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
_______________________________________________________________________________________ 7
OUTPUT DRIVER,
CURRENT SENSE,
AND LOGIC TEMPERATURE
SENSOR
VL
REGULATOR
REF
REFOK
V
IN
OVLO
VL
UVLO
V
REF
V
REF
LOGIC
BATT
DETBAT
ABI
ABO (MAX8845Z ONLY)
ABO (MAX8845Y/MAX8845X/MAX8845W)
EN
POK
IN
BATT
IN
BATT
POK
200kΩ
GND EP
+115°C
4.2V Li+
(4.35V FOR
MAX8845W ONLY)
V
I/O
200kΩ
CHG
MAX8845Z
MAX8845Y
MAX8845X
MAX8845W
V
L
V
REF
I
MINREF
DETBAT
LINEAR
REGULATOR
WITH OVP
SETI
MIN
SAFEOUT
Figure 1. MAX8845Z/MAX8845Y/MAX8845X/MAX8845W Functional Diagram
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
top-off current threshold set by RMIN, the charger
enters top-off mode and the CHG indicator 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 (MAX8845Z/MAX8845Y/MAX8845W) or
4.85V (MAX8845X) and can be used to supply low volt-
age- rated USB systems. The SAFEOUT linear regulator
turns on when VIN ≥4.25V regardless of EN and is dis-
abled when VIN is greater than the overvoltage thresh-
old (7.5V typ) (8.0V typ for MAX8845X only).
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 less than 51kΩ. If DETBAT is left uncon-
nected or the pulldown resistor is 51kΩor greater the
battery charger is disabled. If DETBAT is not used con-
nect DETBAT to GND for normal operation.
POK
Output
The open-drain POK output asserts low when 2.35V ≤
VIN ≤7V (7.5V for MAX8845X only) and (VIN - VBATT) ≥
40mV (typ VIN rising). POK is high impedance during
shutdown. When interfacing with a microprocessor
logic input, a pullup resistor to the microprocessor’s I/O
voltage may be required.
Autobooting Assistant
The MAX8845Z/MAX8845Y/MAX8845X/MAX8845W con-
tain autobooting assistant circuits that generate an
enable signal for system booting (ABO—MAX8845Z,
ABO—MAX8845Y/MAX8845X/MAX8845W). For the
MAX8845Z, the booting assistant functions as an internal
OR gate (Figure 1). The first input is dependant on the
input voltage (VIN) and DETBAT while the second input
is an external signal applied to ABI. The first input (POK)
is driven high once DETBAT is pulled low through a
resistor less than 51kΩ, 2.35V ≤VIN ≤7V (7.5V for only
MAX8845X), and (VIN - VBATT) ≥40mV (typ VIN rising).
The second input signal (ABI) is driven by an external
source (Table 1). ABI enables an autoboot signal when
a battery is connected at BATT and is independent of
POK. If POK is pulled low, the booting assistant always
drives ABO high regardless of ABI. ABI is pulled to GND
through an internal 200kΩresistor. If ABI is supplied
from an outside exposed pin, a RC filter (Figure 4) is
required for ESD protection and noise filtering. If ABI is
supplied by a system’s internal GPIO, or logic, the RC
filter is not required. For the MAX8845Y/MAX8845X/
MAX8845W, the output ABO is only dependent on the
state of ABI (Table 1).
CHG
Charge Indicator Output
CHG is an open-drain output that indicates charge sta-
tus. Table 2 describes the state of CHG during different
stages of operation. CHG is suitable for driving a charge
indication LED. If the MAX8845Z/MAX8845Y/MAX8845X/
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
8 _______________________________________________________________________________________
V
BATT
< 2.5V
PRECHARGE
10% OF IFAST-CHARGE
CHG = LOW
FAST-CHARGE
CONSTANT-CURRENT CHARGE
100% OF I
FAST-CHARGE
CHG = LOW
TOP-OFF
4.2 VOLTAGE REGULATION
CHG = HIGH-Z
(MAX8845Z/MAX8845Y/MAX8845X)
4.35 VOLTAGE REGULATION (MAX8845W)
(V
IN
- V
BATT
) < 30mV
V
BATT
< 2.4V
V
BATT
≥ 2.5V
V
IN
< OVP, AND
(V
IN
- V
BATT
) ≥ 40mV, AND
IC ENABLED
SHUTDOWN
CHARGER = DISABLED
CHG = HIGH-Z
V
IN
> OVP, OR
(V
IN
- V
BATT
) < 30mV, OR
IC DISABLED
ASYNCHRONOUS
FROM ANYWHERE
V
IN
> OVP, OR
(V
IN
- V
BATT
) < 30mV, OR
THERMAL SHUTDOWN, OR
IC DISABLED
I
BATT
> 295V/R
MIN
(kΩ) - 24mA
I
BATT
≤ I
MIN
FOR 6.2ms (typ) OR LONGER
CHARGING CURRENT REDUCTION
CHARGING CURRENT IS REDUCED
AS NECESSARY
DIE TEMPERATURE > +115°C
ANY CHARGING STATE
RETURN TO
CHARGING STATE
DIE TEMPERATURE ≤ +115°C
Figure 2. Charge-State Diagram
MAX8845W are used in conjunction with a microproces-
sor, a pullup resistor to the logic I/O voltage allows CHG
to indicate charge status to the microprocessor instead
of driving an LED.
Thermal Regulation
The thermal-regulation loop limits the MAX8845Z/
MAX8845Y/MAX8845X/MAX8845W die temperature to
+115°C by reducing the charge current as necessary.
This feature not only protects the IC from overheating,
but also allows a higher charge current without risking
damage to the system.
Charger Enable Input
The MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
contain active-low logic input (EN) used to enable the
chargers. Drive EN low, leave unconnected, or connect
to GND to enable the charge-control circuitry. Drive EN
high to disable the charger-control circuitry. EN has an
internal 200kΩpulldown resistor.
Soft-Start
The soft-start algorithm activates when entering fast-
charge mode. When the prequalification state is com-
plete (VBATT exceeds +2.5V), the charging current
ramps up in 250µs to the full charging current. This
reduces the inrush current demand on the input supply.
Applications Information
Fast Charge-Current Setting
The maximum charging current is programmed by an
external resistor connected from SETI to GND (RSETI).
Use the following equation to determine the fast-charge
current (IFAST_CHARGE):
where IFAST_CHARGE is in amps and RSETI is in ohms.
RSETI must always be 1.4kΩor higher due to the con-
tinuous charging current limit of 1ARMS.
Top-Off Current Threshold Setting
The top-off current threshold is programmed by an
external resistor connected from MIN to GND (RMIN).
Use the following equation to determine the top-off cur-
rent (IMIN):
IMIN (falling) = 148V/RMIN (kΩ) + 22mA
IMIN (rising) = 295V/RMIN (kΩ) - 24mA
where IMIN is in mA and RMIN is in kΩ. Use RMIN ≤
2.2kΩ.
IV
R
FAST CHARGE SETI
_=1400
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
_______________________________________________________________________________________ 9
ABI BATT POK CHARGER STATE ABO
(MAX8845Z)
ABO
(MAX8845Y/
MAX8845X/MAX8845W)
Low Present High-Z Shutdown Low High-Z
High Present High-Z Shutdown High Low
Low Not present Low CC/CV mode High High-Z
Low Present Low Fast-charge/top-off High High-Z
High Present Low Fast-charge/top-off High Low
Table 1. Autobooting Output States
EN VIN VBATT IBATT CHG STATE
High X X 0 High-Z Disabled
> 7.5V X
Low X> V
IN - 30mV 0 High-Z Shutdown
Low 4.25V (4.4V for MAX8845W only) ≤ VIN ≤ 7.5V < 2.4V 10% of IFAST-CHARGE* Low Precharge
Low 4.25V (4.4V for MAX8845W only) ≤ VIN ≤ 7.5V ≥ 2.5V 100% of IFAST-CHARGE* Low Fast-charge
Low 4.25V (4.4V for MAX8845W only) ≤ VIN ≤ 7.5V 4.2V (4.35V for
MAX8845W only) < IMIN High-Z Top-off
Table 2. CHG States
X = Don’t care.
*
IFAST-CHARGE is reduced as necessary to prevent the die temperature from exceeding +115°C.
Note: Present indicates that VBATT
≥
2V and Not Present indicates that the battery is not connected.
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
Capacitor Selection
Connect a ceramic capacitor from BATT to GND for
proper stability. Use a 2.2µF ceramic capacitor for most
applications. Connect a 1µF ceramic capacitor from IN
to GND. A larger input capacitor can be used for high
charging current to reduce input voltage ripple.
Connect a 1µF ceramic capacitor from SAFEOUT to
GND. A larger bypass capacitor for SAFEOUT can be
used for optimum noise immunity. Ceramic capacitors
with X5R or X7R dielectric are highly recommended
due to their small size, low ESR, and small temperature
coefficients.
Thermal Considerations
The MAX8845Z/MAX8845Y/MAX8845X/MAX8845W are
available in thermally enhanced Thin QFN packages
with exposed pads. Connect the exposed pad to a
large copper ground plane to provide a thermal contact
between the device and the circuit board for increased
power dissipation. The exposed pad transfers heat
away from the device, allowing the IC to charge the
battery with maximum current, while minimizing the
increase in die temperature.
DC Input Sources
The MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
operate from well-regulated DC sources. The full charg-
ing input voltage range is 4.25V (4.4V for MAX8845W
only) to 7.5V (8V for MAX8845X only). The device can
withstand up to 28V on the input without damage to the
IC. If VIN is greater than 7.5V (8V for MAX8845X only),
the internal overvoltage-protection circuitry disables
charging until the input falls below 7.5V (8V for
MAX8845X only). An appropriate power supply must
provide at least 4.25V at the desired peak charging
current and stay below 7V when unloaded.
Typical Application Circuits
AC Adapter Application
Figure 3 shows the MAX8845Z as a Li+ battery charger
with an AC adapter. The MAX8845Z detects the presence
of an input supply and DETBET, resulting in POK pulled
low. Once POK is pulled low, the autobooting assistant
drives ABO high (MAX8845Z) and enables the power
supplies of the system to boot up. The MAX8845Z begins
charging the battery when EN is low or unconnected. By
monitoring CHG, the system can detect the top-off thresh-
old and terminate the charge through EN. The
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W also pro-
vide an overvoltage-protected SAFEOUT to the system.
Factory System Interface Connector Application
Figure 4 shows the MAX8845Z as an autoboot assistor
with the factory system interface connector. The
MAX8845Z detects the ABI input even though there is no
input voltage available and generates an ABO signal to
turn on power supplies to boot up the system. The con-
figuration in Figure 4 is used for system development,
testing, and calibrations in production or design stage.
USB-Powered Li-Ion Charger
The universal serial bus (USB) provides a high-speed
serial communication port as well as power for the
remote device. The MAX8845Z/MAX8845Y/MAX8845X/
MAX8845W can be configured to charge batteries at the
highest current possible from the host port. Figure 5
shows the MAX8845Z as a USB battery charger. To
make the circuit compatible with either 100mA or
500mA USB ports, the circuit initializes at 100mA charg-
ing current. The microprocessor then enumerates the
host to determine its current capability. If the host port is
capable, the charging current is increased to 450mA to
avoid exceeding the 500mA USB specification through
GPIO control. The MAX8845Z/MAX8845Y/MAX8845X/
MAX8845W also provide an overvoltage-protected
SAFEOUT to the system.
Recommended PCB Layout and Routing
Place all bypass capacitors for IN, BATT, and
SAFEOUT as close as possible to the device. Connect
the battery to BATT as close as possible to the device
to provide accurate battery voltage sensing. Provide a
large copper ground plane to allow the exposed pad to
sink heat away from the device. Make all high-current
traces short and wide to minimize voltage drops. A
sample layout is available in the MAX8845Z Evaluation
Kit to speed designs.
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
10 ______________________________________________________________________________________
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
______________________________________________________________________________________ 11
VBUS
GPIO
GPIO
GPIO
POWER
SUPPLY
ON
SYSTEM
4.2V Li+
POK
V
I/O
CHG
AC ADAPTER
R
SETI
2.8k
Ω
CBATT
2.2µF
C
SAFEOUT
1µF
R
CHG
1MΩ
R
POK
1MΩ
EN
EP
GND
MIN
R
MIN
1.75kΩ
BATT
DETBAT
SAFEOUT
IN
ABI
ABO
SETI
MAX8845Z
CIN
1µF
GND
Figure 3. AC Adapter Application
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
12 ______________________________________________________________________________________
VBUS
GPIO
GPIO
GPIO
POWER
SUPPLY
ON
SYSTEM
POK
V
I/O
CHG
INTERFACE
CONNECTOR
R
SETI
2.8k
Ω
CBATT
2.2µF
C
SAFEOUT
1µF
R
CHG
1MΩ
R
POK
1MΩ
EN
EP
GND
MIN
R
MIN
1.75kΩ
BATT
SAFEOUT
IN
ABI
ABO
SETI
MAX8845Z
CIN
1µF
GND
4.2V
CABI
1µF
R
ABI
10k
ΩDETBAT
IF THE POWER SUPPLY
IS ACTIVE-LOW ENABLED,
USE THE MAX8845Y.
Figure 4. Factory System Interface Connector Application
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
______________________________________________________________________________________ 13
VBUS
GPIO
GPIO
GPIO
GPIO
POWER
SUPPLY
ON
SYSTEM
4.2V Li+
POK
V
I/O
CHG
MINI-USB
CONNECTOR
R
SETIA
15.4k
Ω
R
SETI
3.42k
Ω
CBATT
2.2µF
C
SAFEOUT
1µF
R
CHG
1MΩ
R
POK
1MΩ
EN
EP
GND
MIN
R
MIN
3.09kΩ
BATT
DETBAT
SAFEOUT
IN
ABI
ABO
SETI
MAX8845Z
CIN
1µF
GND
Figure 5. Mini USB Battery Charger
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
14 ______________________________________________________________________________________
V
IN
V
SAFEOUT
POK
OVP OVP
TIME
V
CHG
V
EN
V
SAFEOUT
= 4.7V
(4.85V FOR
MAX8845X ONLY)
V
POK
Figure 6. Timing Diagram
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
IN BATT
(MAX8845Z, ABO)
(MAX8845Y/MAX8845X/MAX8845W, ABO)
DETBAT
SAFEOUT
POK
CHG
EP
C
BATT
2.2µF
SYSTEM
SUPPLY
GND
MIN
R
MIN
1.75kΩ
ABI
EN
ON
OFF
SETI
V
SAFEOUT
1µF
4.25V (4.4V FOR
MAX8845W ONLY) TO 28V
CIN
1µF
R
SET
2.80kΩ
4.2V (4.35V FOR MAX8845W ONLY)
Li+
MAX8845Z
MAX8845Y
MAX8845X
MAX8845W
Typical Operating Circuit
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
______________________________________________________________________________________ 15
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
16 ______________________________________________________________________________________
CHG
123
987
12
11
10
4
5
6
SAFEOUT
IN
MIN
BATT
ABO
DETBAT
ABI
EN
GND
POK
SETI
MAX8845Z
TOP VIEW
*EXPOSED PAD
+
CHG
123
987
12
11
10
4
5
6
SAFEOUT
IN
MIN
BATT
ABO
DETBAT
ABI
EN
GND
POK
SETI
MAX8845Y
MAX8845X
MAX8845W
TOP VIEW
*EXPOSED PAD
+
Pin Configurations
Chip Information
PROCESS: BiCMOS
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
______________________________________________________________________________________ 17
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
THIN QFN.EPS
0.10 C0.08 C
0.10 M C A B
D
D/2
E/2
E
A1
A2
A
E2
E2/2
L
k
e
(ND - 1) X e
(NE - 1) X e
D2
D2/2
b
L
e
L
C
L
e
C
L
L
C
L
C
MARKING
AAAA
PACKAGE OUTLINE,
12L THIN QFN, 3X3X0.75mm
21-0136 custom eng 1
2
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
12 Thin QFN-EP
(3mm x 3mm) T1233-4 —
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
18 ______________________________________________________________________________________
EXPOSED PAD VARIATIONS
CODES
PKG.
T1233-1
MIN.
0.95
NOM.
1.10
D2
NOM.
1.10
MAX.
1.25
MIN.
0.95
MAX.
1.25
E2
12
N
k
A2
0.25
NE
A1
ND
0
0.20 REF
--
3
0.02
3
0.05
L
e
E
0.45
2.90
b
D
A
0.20
2.90
0.70
0.50 BSC.
0.55
3.00
0.65
3.10
0.25
3.00
0.75
0.30
3.10
0.80
PKG
REF. MIN.
12L 3x3
NOM. MAX.
0.35 x 45∞
PIN ID JEDEC
WEED-1
T1233-3 1.10 1.25 0.95 1.10 0.35 x 45∞1.25 WEED-1
0.95
WEED-11.25
1.100.95 0.35 x 45∞
1.25
1.10
0.95
T1233-4
NOTES:
1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.
2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.
3. N IS THE TOTAL NUMBER OF TERMINALS.
4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO
JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED
WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR
MARKED FEATURE.
5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.20 mm AND 0.25 mm
FROM TERMINAL TIP.
6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.
7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.
8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.
9. DRAWING CONFORMS TO JEDEC MO220 REVISION C.
10. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY.
11. NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY.
12. WARPAGE NOT TO EXCEED 0.10mm.
PACKAGE OUTLINE,
12L THIN QFN, 3X3X0.75mm
21-0136 custom
eng
2
2
°
°
°
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
MAX8845Z/MAX8845Y/MAX8845X/MAX8845W
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________
19
© 2009 Maxim Integrated Products Maxim is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 3/09 Initial release —
1 9/09 Corrected the
POK
Output section description and added MAX8845X and
MAX8845W to data sheet 1–19