MAX8845W [MAXIM]
28V Linear Li Battery Chargers with Battery Detection and Overvoltage Protected Output;
| 型号： | MAX8845W |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 28V Linear Li Battery Chargers with Battery Detection and Overvoltage Protected Output 电池 |
| 文件： | 总19页 (文件大小：495K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4340; Rev 1; 9/09
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
ZY/MAX845W
General Description
Features
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.
o CCCV, Thermally Regulated Linear 1-Cell Li+
Battery Charger
o No External MOSFET, Reverse Blocking Diode, or
Current-Sense Resistor
o Programmable Fast-Charge Currents (1A
max)
RMS
o Programmable Top-Off Current Threshold (MIN)
o Input Overvoltage Protected 4.7V Output
(MAX8845Z/MAX8845Y/MAX8845W) or 4.85V
(MAX8845X) (SAFEOUT)
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.
o Proprietary Die Temperature Regulation Control
(+115°C)
o 4.25V (4.4V for MAX8845W only) to 28V Input
Voltage Range with Input Overvoltage Protection
Above +7.5V (+8.0V for MAX8845X only)
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.
o Low-Dropout Voltage (300mV at 500mA)
o Input Power-Source Detection Output (POK),
Charge Status Output (CHG), Charge-Enable Input
(EN)
o Output for Autobooting (ABO—MAX8845Z,
ABO—MAX8845Y/MAX8845X/MAX8845W)
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).
o Tiny, 3mm x 3mm 12-Pin Thin QFN Package,
0.8mm Height (max)
Ordering Information
ABO
TOP
MARK
PART
PIN-PACKAGE
ACTIVE
STATE
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).
MAX8845ZETC+ 12 Thin QFN-EP*
MAX8845YETC+ 12 Thin QFN-EP*
MAX8845XETC+ 12 Thin QFN-EP*
MAX8845WETC+ 12 Thin QFN-EP*
ABL
ABM
ABQ
ABR
Active high
Active low
Active low
Active low
Note: All devices are specified over the -40°C to +85°C oper-
ating temperature range.
Applications
Cellular and Cordless Phones
Smart Phones and PDAs
Digital Still Cameras
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
MP3 Players
USB Appliances
Typical Operating Circuit and Pin Configurations appear at
end of data sheet.
Charging Cradles and Docks
Bluetooth® Equipment
Bluetooth is a registered trademark of Bluetooth SIG.
________________________________________________________________ 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.
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
ABSOLUTE MAXIMUM RATINGS
IN to GND...............................................................-0.3V to +30V
ABI, BATT, EN, POK, ABO, ABO, CHG, DETBAT, SETI, MIN,
SAFEOUT to GND ................................................-0.3V to +6V
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
IN to BATT Continuous Current.........................................1A
RMS
Continuous Power Dissipation (T = +70°C)
A
12-Thin QFN (derate 14.7mW/°C above +70°C)
(multilayer PCB) ......................................................1176.5mW
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.
ELECTRICAL CHARACTERISTICS
(V = 5V, V
= 4V, R
= 1MΩ to BATT, EN = unconnected, R
= 2.8kΩ to GND, V
= 0, C
= 2.2µF, T = -40°C to
BATT A
IN
BATT
POK
SETI
DETBAT
+85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
CONDITIONS
MIN
TYP
MAX
28
UNITS
Input Supply Voltage Range
0
V
4.25
4.40
7.0
7.00
7.00
8.0
Input Supply Operating Voltage Range
Overvoltage Lockout Trip Threshold
V
V
MAX8845W only
rising, 100mV hysteresis (typ)
V
7.5
8.0
IN
MAX8845X only
7.5
8.5
Constant current charging
0.22
1
0.50
I
- I
, I
= 0
IN BATT BATT
Constant current charging
- I = 500mA
I
I
IN BATT, BATT
Input Current
mA
IC disabled, V = 5V
0.20
0.02
0.50
EN
V
V
= 4V,
IN
T
T
= +25°C
= +85°C
A
= 4.2V (4.35V for
BATT
0.03
A
MAX8845W only)
BATT, CHG, POK
Minimum BATT Bypass Capacitance
2.2
µF
V
V
Prequalification Threshold Voltage
V
rising, 100mV hysteresis (typ)
BATT
2.3
2.5
2.7
BATT
4.175
4.158
4.324
4.306
4.200
4.200
4.350
4.350
260
4.225
4.242
4.376
4.394
I
= 0
T = -40°C to +85°C
A
BATT
Battery Regulation Voltage
V
MAX8845W only
Regulator Dropout Voltage (V - V
IN
)
V
= 4.1V, I = 425mA
BATT
mV
µA
BATT
BATT
V
V
= 0 to 4V,
IN
5
10
= 4.2V (4.35V for MAX8845W only)
BATT
BATT Input Current
ZY/MAX845W
IC disabled
3
Current-Sense Amplifier Gain (I
Fast-Charge Current
to I
)
I = 500mA
BATT
1016
500
500
µA/A
BATT
SETI
T
T
= 0°C to +85°C
460
425
540
575
A
V
= 3.5V,
BATT
R
= 2.8kΩ
SETI
= -40°C to +85°C
A
mA
mA
V
= 3.5V,
BATT
T
A
= 0°C to +85°C
85
100
106
115
R
= 14kΩ
SETI
I
falling, battery is charged
BATT
CHG Top-Off Threshold
R
= 1.75kΩ
MIN
2
_______________________________________________________________________________________
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
ZY/MAX845W
ELECTRICAL CHARACTERISTICS (continued)
(V = 5V, V
= 4V, R
= 1MΩ to BATT, EN = unconnected, R
= 2.8kΩ to GND, V
= 0, C
= 2.2µF, T = -40°C to
BATT A
IN
BATT
POK
SETI
DETBAT
+85°C, unless otherwise noted. Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
mA
I
R
rising after top-off is detected,
BATT
CHG Hysteresis
38
= 1.75kΩ
MIN
CHG Detection Delay
I
falls below top-off threshold
4.0
5
6.2
10.7
15
ms
BATT
Percentage of the fast-
charge current, V
= 2.2V
Prequalification Charge Current
T
A
= 0°C to +85°C
10
%
BATT
CHG, POK Output Low Threshold
I
= 5mA , I
= 5mA
CHG
0.4
1
V
POK
T
T
= +25°C
= +85°C
A
V
V
= 5.5V,
POK
CHG
CHG, POK Output High Leakage Current
µA
= 5.5V
BATT
0.01
40
A
V
V
rising
falling
IN
IN
POK Threshold
V
- V
mV
V
IN
30
DETBAT, SAFEOUT
DETBAT Logic-Input Low Threshold
DETBAT Logic-Input High Threshold
DETBAT Pullup Resistor
0.4
1.3
DETBAT to V = 3V
470
1
kΩ
L
Minimum SAFEOUT Bypass Capacitance
µF
I
= 30mA, V = 5V, T = 0°C to
IN A
SAFEOUT
4.5
4.7
4.9
5.0
+85°C (MAX8845Z/MAX8845Y/MAX8845W)
SAFEOUT Regulated Output
V
I
= 20mA, V = 5V, T = 0°C to
SAFEOUT
IN
A
4.75
4.85
100
+85°C (MAX8845X)
SAFEOUT Current Limit
mA
EN, ABI, ABO, ABO
EN, ABI Internal Pulldown Resistor
EN Logic-Input Low Threshold
EN Logic-Input High Threshold
ABI Logic-Input Low Threshold
ABI Logic-Input High Threshold
100
1.3
1.3
200
400
0.4
kΩ
V
4.25V (4.4V for MAX8845W only) ≤ V ≤ 7V
IN
4.25V (4.4V for MAX8845W only) ≤ V ≤ 7V
V
IN
V
V
= 4V, V = 0
0.4
0.4
V
BATT
BATT
IN
= 4V, V = 0
V
IN
ABO Output Low Threshold (MAX8845Y/
MAX8845X/MAX8845W)
Open drain, I
= 1mA
V
V
V
V
ABO(SINK)
ABO Output High Threshold (MAX8845Y/
MAX8845X/MAX8845W)
V
V
-
-
BATT
0.4V
Open drain, 100kΩ pullup to BATT
ABO Output Low Threshold
(MAX8845Z)
I
= 1mA
0.4
ABO(SINK)
BATT
0.4V
ABO Output High Threshold (MAX8845Z)
I
= 1mA
ABO(SOURCE)
THERMAL
Die Temperature Regulation Threshold
115
°C
Note 1: Specifications are 100% production tested at T = +25°C. Limits over the operating temperature range are guaranteed by
A
design and characterization.
_______________________________________________________________________________________
3
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
Typical Operating Characteristics
(V = 5V, V
4.7kΩ to GND, C
= 4V, R
= R
= 200kΩ to 5V, EN = unconnected, R
= 2.8kΩ to GND, R
= 1.74kΩ to GND, R
DETBAT
=
IN
BATT
POK
CHG
SETI
MIN
= 2.2µF, T = +25°C, unless otherwise noted.)
BATT
A
SUPPLY CURRENT
vs. INPUT VOLTAGE
DISABLED MODE SUPPLY CURRENT
vs. INPUT VOLTAGE
CHARGE CURRENT
vs. BATTERY VOLTAGE
1000
900
800
700
600
500
400
300
200
100
0
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0.6
0.5
0.4
0.3
0.2
0.1
0
V
= 0,
= 0
RISING
EN
V
= 5V
EN
I
BATT
V
IN
0
4
8
12
16
20
24
28
0
5
10
15
20
25
30
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
BATTERY VOLTAGE (V)
INPUT VOLTAGE (V)
INPUT VOLTAGE (V)
CHARGE CURRENT
vs. INPUT VOLTAGE
CHARGE CURRENT
vs. INPUT VOLTAGE HEADROOM
SAFEOUT OUTPUT VOLTAGE
vs. INPUT VOLTAGE
1000
900
800
700
600
500
400
300
200
100
0
600
500
400
300
200
100
0
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
I
= 1mA
V
V
= 4V,
RISING
SAFEOUT
BATT
IN
0
4
8
12
16
20
24
28
0
100
200
300
- V
400
(mV)
500
600
0
4
8
12
16
20
24
28
INPUT VOLTAGE (V)
V
INPUT VOLTAGE (V)
IN
BATT
SAFEOUT OUTPUT VOLTAGE
vs. LOAD CURRENT
SHUTDOWN
(FAST-CHARGE TO SHUTDOWN)
STARTUP INTO PRECHARGE
MAX8845Z/Y/X/W toc08
MAX8845Z/Y/X/W toc09
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
500mA/div
0
I
BATT
100mA/div
0
I
BATT
5V/div
5V/div
V
V
IN
IN
ZY/MAX845W
0
0
5V/div
0
V
5V/div
0
V
EN
EN
5V/div
0
5V/div
0
V
V
POK
POK
0
20
40
60
80
100
40µs/div
40µs/div
LOAD CURRENT (mA)
4
_______________________________________________________________________________________
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
ZY/MAX845W
Typical Operating Characteristics (continued)
(V = 5V, V
4.7kΩ to GND, C
= 4V, R
BATT
= R
= 200kΩ to 5V, EN = unconnected, R
= 2.8kΩ to GND, R
= 1.74kΩ to GND, R
=
DETBAT
IN
BATT
POK
CHG
SETI
MIN
= 2.2µF, T = +25°C, unless otherwise noted.)
A
BATTERY REGULATION ACCURACY
vs. AMBIENT TEMPERATURE
FAST-CHARGE CURRENT
TOP-OFF CURRENT THRESHOLD
vs. 1/R (kΩ)
vs. R
SETI
MIN
1.0
0.8
1000
100
10
600
550
500
450
400
350
300
250
200
150
100
50
I
= 0
BATT
0.6
0.4
TOP-OFF CURRENT RISING
0.2
0
-0.2
-0.4
-0.6
-0.8
-1.0
TOP-OFF CURRENT FALLING
1
0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0
0.5 0.7 0.9 1.1 1.3 1.5 1.7 1.9
-40
-15
10
35
60
85
1
10
100
1000
10,000
AMBIENT TEMPERATURE (°C)
R
(kΩ)
SETI
1/R (kΩ)
MIN
AUTOBOOT ENABLED BY ABI SIGNAL
CHARGE CURRENT
vs. AMBIENT TEMPERATURE
(MAX8845Z)
MAX8845Z/Y/X/W toc14
700
600
500
400
300
200
100
0
V
= 4V
BATT
5V/div
0
V
ABI
5V/div
0
V
= 3.2V
BATT
V
IN
5V/div
0
V
BATT
5V/div
0
R
= 2.8kΩ
SETI
V
ABO
-40 -20
0
20
40
60
80 100
4µs/div
AMBIENT TEMPERATURE (°C)
AUTOBOOT ENABLED BY INPUT VOLTAGE
AUTOBOOT ENABLED BY ABI SIGNAL
(MAX8845Z)
(MAX8845Y/MAX8845X/MAX8845W)
MAX8845Z/Y/X/W toc15
MAX8845Z/Y/X/W toc16
5V/div
5V/div
V
0
V
0
ABI
ABI
5V/div
0
5V/div
0
V
V
IN
IN
5V/div
5V/div
V
0
V
BATT
BATT
0
5V/div
5V/div
0
V
0
ABO
V
ABO
20µs/div
4µs/div
_______________________________________________________________________________________
5
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
Pin Description
PIN
MAX8845Y/
MAX8845X/
MAX8845W
NAME
FUNCTION
MAX8845Z
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
1
2
1
2
SETI
a resistor (R
in Figure 3) from SETI to GND. I
= 1400V/R
. To
SETI
FAST-CHARGE
SETI
configure the MAX8845Z/MAX8845Y/MAX8845X/MAX8845W as a USB charger, see
Figure 5.
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.
DETBAT
Autobooting External Input. See the Autobooting Assistant section and Table 1 for
autobooting conditions. ABI is pulled to GND through an internal 200kΩ resistor.
3
4
5
3
4
5
ABI
EN
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.
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.
GND
Active-Low, Input Voltage Status Indicator. POK is an open-drain output that asserts low
when 2.35V < V < 7V (7.5V for MAX8845X only) and (V - V
) > 40mV. If V
>
IN
IN
BATT
IN
6
7
6
POK
+7.5V (+8.0V for MAX8845X only) or V
high impedance. Connect a pullup resistor to the microprocessor’s I/O voltage when
interfacing with a microprocessor logic input.
> V the IC is shut down and POK becomes
BATT IN
Active-High, Autobooting Logic Output. See the Autobooting Assistant section and Table
1 for autobooting conditions.
—
ABO
Active-Low, Open-Drain Logic Output. See the Autobooting Assistant section and Table
1 for autobooting conditions.
—
8
7
8
9
ABO
BATT
MIN
Li+ Battery Connection. Bypass BATT to GND with a 2.2µF ceramic capacitor.
Top-Off Current Threshold Programmable Input. I
(mA).
(mA) falling = 148V/R
(kΩ) + 22
MIN
MIN
9
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.
10
10
CHG
Input Supply Voltage. Bypass IN to GND with a 1µF or larger ceramic capacitor to
improve line noise and input transient rejection.
ZY/MAX845W
11
12
—
11
12
—
IN
SAFEOUT
EP
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.
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.
6
_______________________________________________________________________________________
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
ZY/MAX845W
LINEAR
REGULATOR
WITH OVP
SAFEOUT
4.2V Li+
(4.35V FOR
MAX8845W ONLY)
BATT
IN
+115°C
OUTPUT DRIVER,
CURRENT SENSE,
AND LOGIC
TEMPERATURE
SENSOR
DETBAT
SETI
V
REF
V
REF
V
I/O
I
MINREF
MIN
IN
CHG
POK
V
VL
REGULATOR
IN
OVLO
BATT
BATT
V
POK
L
VL
UVLO
REF
ABO (MAX8845Z ONLY)
ABI
LOGIC
DETBAT
V
REF
REFOK
ABO (MAX8845Y/MAX8845X/MAX8845W)
200kΩ
200kΩ
EN
MAX8845Z
MAX8845Y
MAX8845X
MAX8845W
EP
GND
Figure 1. MAX8845Z/MAX8845Y/MAX8845X/MAX8845W Functional Diagram
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
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-
_______________________________________________________________________________________
7
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
ASYNCHRONOUS
FROM ANYWHERE
> OVP, OR
SHUTDOWN
CHARGER = DISABLED
CHG = HIGH-Z
V
IN
(V - V
) < 30mV, OR
IN
BATT
(V - V
) < 30mV
IN
BATT
THERMAL SHUTDOWN, OR
IC DISABLED
V
BATT
< 2.5V
V
IN
> OVP, OR
(V - V
) < 30mV, OR
IN
BATT
IC DISABLED
V
< OVP, AND
IN
(V - V ) ≥ 40mV, AND
PRECHARGE
10% OF IFAST-CHARGE
CHG = LOW
IN
BATT
IC ENABLED
DIE TEMPERATURE > +115°C
CHARGING CURRENT REDUCTION
CHARGING CURRENT IS REDUCED
AS NECESSARY
ANY CHARGING STATE
V
BATT
< 2.4V
V
≥ 2.5V
BATT
DIE TEMPERATURE ≤ +115°C
TOP-OFF
4.2 VOLTAGE REGULATION
CHG = HIGH-Z
I
> 295V/R (kΩ) - 24mA
MIN
BATT
FAST-CHARGE
CONSTANT-CURRENT CHARGE
100% OF I
RETURN TO
CHARGING STATE
(MAX8845Z/MAX8845Y/MAX8845X)
4.35 VOLTAGE REGULATION (MAX8845W)
FAST-CHARGE
CHG = LOW
I
≤ I
BATT MIN
FOR 6.2ms (typ) OR LONGER
Figure 2. Charge-State Diagram
top-off current threshold set by R
, the charger
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
MIN
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
input voltage (V ) and DETBAT while the second input
IN
is an external signal applied to ABI. The first input (POK)
turns on when V ≥ 4.25V regardless of EN and is dis-
IN
is driven high once DETBAT is pulled low through a
abled when V is greater than the overvoltage thresh-
IN
resistor less than 51kΩ, 2.35V ≤ V ≤ 7V (7.5V for only
IN
old (7.5V typ) (8.0V typ for MAX8845X only).
MAX8845X), and (V - V
) ≥ 40mV (typ V rising).
IN
BATT
IN
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 200kΩ resistor. 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).
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 51kΩ or greater the
battery charger is disabled. If DETBAT is not used con-
nect DETBAT to GND for normal operation.
POK Output
ZY/MAX845W
The open-drain POK output asserts low when 2.35V ≤
V
≤ 7V (7.5V for MAX8845X only) and (V - V
) ≥
IN
IN
BATT
40mV (typ V rising). POK is high impedance during
IN
shutdown. When interfacing with a microprocessor
logic input, a pullup resistor to the microprocessor’s I/O
voltage may be required.
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/
8
_______________________________________________________________________________________
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
ZY/MAX845W
Table 1. Autobooting Output States
ABO
(MAX8845Y/
MAX8845X/MAX8845W)
ABO
(MAX8845Z)
ABI
BATT
POK
CHARGER STATE
Low
High
Low
Low
High
Present
Present
High-Z
High-Z
Low
Shutdown
Shutdown
Low
High
High
High
High
High-Z
Low
Not present
Present
CC/CV mode
High-Z
High-Z
Low
Low
Fast-charge/top-off
Fast-charge/top-off
Present
Low
Note: Present indicates that V
≥ 2V and Not Present indicates that the battery is not connected.
BATT
Table 2. CHG States
EN
V
IN
V
BATT
I
CHG
STATE
BATT
High
X
X
X
0
High-Z
Disabled
> 7.5V
X
Low
0
High-Z
Shutdown
> V - 30mV
IN
Low
Low
4.25V (4.4V for MAX8845W only) ≤ V ≤ 7.5V
< 2.4V
10% of I
*
FAST-CHARGE
Low
Low
Precharge
IN
4.25V (4.4V for MAX8845W only) ≤ V ≤ 7.5V
≥ 2.5V
100% of I
*
FAST-CHARGE
Fast-charge
IN
4.2V (4.35V for
MAX8845W only)
Low
4.25V (4.4V for MAX8845W only) ≤ V ≤ 7.5V
< I
High-Z
Top-off
IN
MIN
X = Don’t care.
*I
is reduced as necessary to prevent the die temperature from exceeding +115°C.
FAST-CHARGE
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.
Applications Information
Fast Charge-Current Setting
The maximum charging current is programmed by an
external resistor connected from SETI to GND (R
).
SETI
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.
Use the following equation to determine the fast-charge
current (I ):
FAST_CHARGE
1400V
I
=
FAST_CHARGE
R
SETI
where I
SETI
is in amps and R
is in ohms.
FAST_CHARGE
must always be 1.4kΩ or higher due to the con-
SETI
R
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 200kΩ pulldown resistor.
tinuous charging current limit of 1A
.
RMS
Top-Off Current Threshold Setting
The top-off current threshold is programmed by an
external resistor connected from MIN to GND (R
).
MIN
Use the following equation to determine the top-off cur-
rent (I
):
MIN
Soft-Start
The soft-start algorithm activates when entering fast-
charge mode. When the prequalification state is com-
I
(falling) = 148V/R
(rising) = 295V/R
(kΩ) + 22mA
(kΩ) - 24mA
is in kΩ. Use R
MIN
MIN
I
MIN
MIN
where I
2.2kΩ.
is in mA and R
≤
MIN
MIN
MIN
plete (V
exceeds +2.5V), the charging current
BATT
ramps up in 250µs to the full charging current. This
reduces the inrush current demand on the input supply.
_______________________________________________________________________________________
9
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
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.
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.
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.
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.
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.
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 V is greater than 7.5V (8V for MAX8845X only),
IN
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.
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.
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
ZY/MAX845W
10 ______________________________________________________________________________________
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
ZY/MAX845W
4.2V Li+
IN
BATT
C
1µF
IN
C
2.2µF
SYSTEM
BATT
AC ADAPTER
GND
MAX8845Z
DETBAT
ABI
SAFEOUT
VBUS
V
I/O
C
SAFEOUT
1µF
R
CHG
1MΩ
CHG
POK
GPIO
ABO
SETI
R
1MΩ
POK
GPIO
GPIO
R
SETI
2.8kΩ
EN
EP
MIN
GND
R
MIN
POWER
SUPPLY
1.75kΩ
ON
Figure 3. AC Adapter Application
______________________________________________________________________________________ 11
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
IN
BATT
C
1µF
IN
C
2.2µF
SYSTEM
BATT
4.2V
R
ABI
MAX8845Z
10kΩ
INTERFACE
CONNECTOR
DETBAT
ABI
C
1µF
ABI
GND
SAFEOUT
VBUS
V
I/O
C
SAFEOUT
1µF
R
CHG
1MΩ
CHG
POK
GPIO
ABO
SETI
R
1MΩ
POK
GPIO
GPIO
R
SETI
2.8kΩ
EN
EP
MIN
GND
R
MIN
POWER
SUPPLY
1.75kΩ
IF THE POWER SUPPLY
IS ACTIVE-LOW ENABLED,
USE THE MAX8845Y.
ON
Figure 4. Factory System Interface Connector Application
ZY/MAX845W
12 ______________________________________________________________________________________
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
ZY/MAX845W
4.2V Li+
IN
BATT
C
1µF
IN
C
2.2µF
SYSTEM
BATT
MINI-USB
CONNECTOR
GND
MAX8845Z
DETBAT
ABI
SAFEOUT
VBUS
V
I/O
C
SAFEOUT
1µF
R
CHG
1MΩ
CHG
POK
GPIO
ABO
SETI
R
1MΩ
POK
GPIO
GPIO
R
SETIA
R
SETI
15.4kΩ
3.42kΩ
EN
EP
MIN
GND
R
MIN
3.09kΩ
GPIO
POWER
SUPPLY
ON
Figure 5. Mini USB Battery Charger
______________________________________________________________________________________ 13
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
OVP
OVP
POK
V
IN
V
POK
V
EN
V
CHG
V
= 4.7V
SAFEOUT
(4.85V FOR
MAX8845X ONLY)
V
SAFEOUT
TIME
Figure 6. Timing Diagram
ZY/MAX845W
14 ______________________________________________________________________________________
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
ZY/MAX845W
Typical Operating Circuit
4.25V (4.4V FOR
MAX8845W ONLY) TO 28V
DETBAT
BATT
IN
C
IN
1µF
C
BATT
4.2V (4.35V FOR MAX8845W ONLY)
Li+
2.2µF
MAX8845Z
MAX8845Y
MAX8845X
MAX8845W
ABI
SYSTEM
SUPPLY
OFF
EN
ON
MIN
R
MIN
1.75kΩ
CHG
POK
SETI
(MAX8845Z, ABO)
R
SET
2.80kΩ
(MAX8845Y/MAX8845X/MAX8845W, ABO)
SAFEOUT
V
1µF
SAFEOUT
EP
GND
______________________________________________________________________________________ 15
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
Pin Configurations
TOP VIEW
TOP VIEW
9
8
7
9
8
7
CHG
CHG
10
11
12
10
11
12
6
5
4
POK
GND
EN
6
5
4
POK
GND
EN
MAX8845Y
MAX8845X
MAX8845W
MAX8845Z
IN
IN
SAFEOUT
SAFEOUT
*EXPOSED PAD
*EXPOSED PAD
+
+
1
2
3
1
2
3
Chip Information
PROCESS: BiCMOS
ZY/MAX845W
16 ______________________________________________________________________________________
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
ZY/MAX845W
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
12 Thin QFN-EP
(3mm x 3mm)
T1233-4
—
(NE - 1)
X e
MARKING
E
E/2
D2/2
(ND - 1)
e
X e
D/2
D
AAAA
C
D2
L
b
k
0.10 M
C A B
C
L
E2/2
L
E2
C
L
C
L
0.10
C
0.08
C
A
A2
A1
L
L
e
e
PACKAGE OUTLINE,
12L THIN QFN, 3X3X0.75mm
1
21-0136 custom eng
2
______________________________________________________________________________________ 17
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
Package Information (continued)
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
PKG
12L 3x3
EXPOSED PAD VARIATIONS
REF. MIN. NOM. MAX.
D2
E2
PKG.
PIN ID
JEDEC
CODES
A
b
0.70 0.75 0.80
0.20 0.25 0.30
2.90 3.00 3.10
MAX. MIN. NOM. MAX.
MIN. NOM.
T1233-1
T1233-3
T1233-4
1.10 1.25
0.95
0.95
0.95
1.10
1.10
1.10
°
0.95
0.95
0.95
1.25
1.25
1.25
0.35 x 45∞ WEED-1
D
°
1.10 1.25
1.10 1.25
0.35 x 45∞ WEED-1
E
e
2.90 3.00 3.10
0.50 BSC.
°
0.35 x 45∞ WEED-1
L
N
0.45 0.55 0.65
12
3
ND
NE
A1
A2
k
3
0
0.02 0.05
0.20 REF
-
-
0.25
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
2
21-0136 custom eng
2
ZY/MAX845W
18 ______________________________________________________________________________________
28V Linear Li+ Battery Chargers with Battery
Detection and Overvoltage Protected Output
ZY/MAX845W
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
3/09
Initial release
—
Corrected the POK Output section description and added MAX8845X and
MAX8845W to data sheet
1
9/09
1–19
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.
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