19-2912; Rev 1; 2/07
Dual-Input, USB/AC Adapter, 1-Cell
Li+ Charger with OVP and Thermal Regulation
General Description
The MAX1874 charges a single-cell Li+ battery from
both USB and AC adapter sources. It also includes bat-
tery-to-input power switchover, so the system can be
powered directly from the power source rather than
from the battery.
In its simplest application, the MAX1874 needs no
external MOSFET or diodes, and accepts input volt-
ages up to 6.5V; however, DC input overvoltage protec-
tion up to 18V can be added with a single SOT PFET.
On-chip thermal limiting simplifies printed circuit board
(PCB) layout and allows optimum charging rate without
the thermal limits imposed by worst-case battery and
input voltage. When the MAX1874 thermal limit is
reached, the charger does not shut down but simply
reduces charging current.
Ambient or battery temperature can be monitored with
an external thermistor. When the temperature is out of
range, charging pauses.
Other features include a
CHG
output to indicate when
battery current tapers below a predetermined level. DC
power-OK (DCOK), USB power-OK (UOK), and power-
on (PON) outputs indicate when valid power is present.
These outputs drive logic or power-selection MOSFETs
to disconnect the charging sources from the load and
to protect the MAX1874 from overvoltage.
The MAX1874 contains no logic for communication with
the USB host. It must receive instructions from a local
microcontroller. The MAX1874 is available in a 16-pin
5mm
✕
5mm thin QFN package and operates over the
-40°C to +85°C temperature range.
♦
Charge from USB or AC Adapter
♦
Automatic Switchover to AC Adapter
♦
Thermal Limiting Simplifies Board Design
♦
Small, High-Power 16-Pin Thin QFN Package
♦
Input Protection Up to 18V
♦
Soft-Start
♦
Automatic Battery-to-Input Load Switch
KIT
ATION
EVALU
BLE
AVAILA
Features
MAX1874
Ordering Information
PART
MAX1874ETE
TEMP RANGE
-40°C to +85°C
PIN-
PACKAGE
16 Thin QFN
5mm x 5mm
PKG
CODE
T1655-2
Typical Operating Circuit
DC INPUT
DC
MAX1874
DCOK
DCLV
UOK
PON
BATT
Li+
CELL
Applications
USB INPUT
USB
CHG
USEL
500mA
100mA
PDAs
Wireless Appliances
Cell Phones
Digital Cameras
Pin Configuration
DCOK
TO REF
DCI
REGULATOR
EN
REF
BATT
PON
14
TOP VIEW
16
DCLV
DC
CHG
USEL
1
2
3
4
5
EN
15
13
UOK
THRM
12
11
USB
BYP
PGND
REF
MAX1874
10
9
BYP
PGND
GND
NTC
THERMISTOR
6
GND
7
DCI
8
THRM
THIN QFN
5mm x 5mm
Functional Diagram appears at the end of the data sheet.
1
________________________________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Dual-Input, USB/AC Adapter, 1-Cell
Li+ Charger with OVP and Thermal Regulation
MAX1874
ABSOLUTE MAXIMUM RATINGS
DC,
DCOK
to GND .................................................-0.3V to +20V
DCLV, BYP, USB,
UOK,
DCI, REF, USEL, THRM,
EN, BATT,
CHG,
PON to GND .............................-0.3V to +7V
PGND to GND .......................................................-0.3V to +0.3V
Continuous Current (DCLV) ..................................................1.1A
Continuous Current (USB) ....................................................0.6A
Continuous Power Dissipation (T
A
= +70°C)
16-Pin 5mm
✕
5mm Thin QFN
(derate 21.3mW/°C above +70°C) ...................................1.7W
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Maximum Junction Temperature .....................................+150°C
Lead Temperature (soldering, 10s) .................................+300°C
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
USB
= V
DC
= V
DCLV
= V
EN
= V
USEL
= 5V, V
BATT
= 4.2V, V
THRM
= V
REF
/ 2, Circuit of Figure 2,
T
A
= 0°C to +85°C,
unless otherwise
noted. Typical values are at T
A
= +25°C.)
PARAMETER
INPUT VOLTAGE RANGES AND INPUT CURRENT
Maximum DC Input Voltage with
Overvoltage Protection
Maximum DC Input Voltage Without
Overvoltage Protection
Maximum Input Voltage for Charging
DC Supply Current
DCLV Operating Voltage Range
DCLV Shutdown Supply Current
USB Input Voltage Range
V
EN
= 0V
USB Supply Current
DCI Input Current
BYP Output Resistance
THRM Input Bias Current
BATTERY VOLTAGE
BATT Regulation Voltage
BATT Prequal Voltage Threshold
Prequal Threshold Hysteresis
USB Charging Headroom
DC Charging Headroom
REF Voltage (Buffered Output)
I
USB
= 100mA
I
USB
= 500mA
I
DCIN
= 800mA
I
REF
= 0 to 500µA, 4V < V
DC
or V
USB
< 6.5V;
does not affect BATT regulation accuracy
2.94
BATT rising
4.1685
2.8
4.20
3
70
100
200
250
3
3.06
4.2315
3.2
V
V
mV
mV
mV
V
(Note 1)
V
EN
= 5V, V
DC
= 0V
V
EN
= 5V, V
DC
= 5V
V
EN
= 0V
4.35
500
2
160
1
5
1
100
V
EN
= 0V
V
EN
= 5V
4.35
300
Q2 input MOSFET must be in place; charging
occurs only below 6.2V, Figures 3, 4, and 5
DC = DCLV, Q2 input MOSFET not on circuit,
Figure 2
6.0
6.2
2
4
18
6.5
6.5
4
6
6.00
500
6.50
750
3
300
100
V
V
V
mA
V
µA
V
µA
mA
µA
nA
Ω
nA
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
Dual-Input, USB/AC Adapter, 1-Cell
Li+ Charger with OVP and Thermal Regulation
ELECTRICAL CHARACTERISTICS (continued)
(V
USB
= V
DC
= V
DCLV
= V
EN
= V
USEL
= 5V, V
BATT
= 4.2V, V
THRM
= V
REF
/ 2, Circuit of Figure 2,
T
A
= 0°C to +85°C,
unless otherwise
noted. Typical values are at T
A
= +25°C.)
PARAMETER
BATTERY CHARGING AND PRECHARGE CURRENT
DCI Voltage Range
DCI Voltage to BATT Current
USB Charging Current
Soft-Start Current-Ramp Time
Prequal Charging Current
BATT Input Current
BATT Shutdown Current
THRM COLD Trip Level
THRM HOT Trip Level
THRM Disable Threshold
Internal Die Thermal Limit
LOGIC INPUT/OUTPUTS AND GATE DRIVERS
PON High Output Resistance
PON Low Output Resistance
DCOK
Low Output Resistance
DCOK
Off-Leakage Current
UOK
Output Resistance
UOK
Off-Leakage Current
CHG
Threshold to Indicate Battery Full,
Battery Current Falling (Note 3)
CHG
Logic-Low Output
CHG
Leakage Current
EN, USEL Logic-Input High Level
EN, USEL Logic-Input Low Level
EN, USEL Input Bias Current
PON pulled up to active input (DCLV or USB),
V
DCLV
or V
USB
= 5V
PON resistance to GND, V
DCLV
= V
USB
= 0
DCOK
pulled low
V
DCOK
= 12V, V
DC
= 0V
UOK
resistance to GND, V
DC
= 0
V
UOK
= 6.5V
DC input (% of charge current set at DCI)
USB input, USEL = 5V (% of USB charging current)
USB input with USEL = 0
Sinking 10mA sink
V
CHG
= 6.5V
1.6
0.4
1
8
20
12.5
25
Voltage
mode
0.4
1
V
µA
V
V
µA
25
1
19
30
%
25
120
25
1
Ω
kΩ
Ω
µA
Ω
µA
V
DCI
= V
REF
V
DCI
= V
REF
/ 2
USEL = high
USEL = low
Measured from 10% to 90%
V
BATT
= 2.5V
No DC or USB power, V
BATT
= 4.2V
EN = GND, USB- and/or DC-powered
(Note 2)
(Note 2)
0.72
0.28
50
35
0.1 x V
REF
950
490
1000
520
455
82
7
55
5
1
0.74
0.29
100
+105
70
7.5
2
0.76
0.30
150
V
REF
1050
550
495
95
V
mA
mA
ms
mA
µA
µA
V
REF
V
REF
mV
°C
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1874
THERMISTOR MONITOR AND DIE-TEMPERATURE REGULATION
_______________________________________________________________________________________
3
Dual-Input, USB/AC Adapter, 1-Cell
Li+ Charger with OVP and Thermal Regulation
MAX1874
ELECTRICAL CHARACTERISTICS (continued)
(V
USB
= V
DC
= V
DCLV
= V
EN
= V
USEL
= 5V, V
BATT
= 4.2V, V
THRM
= V
REF
/ 2, Circuit of Figure 2,
T
A
= 0°C to +85°C,
unless otherwise
noted. Typical values are at T
A
= +25°C.)
PARAMETER
TIMING
DC Rising to
DCOK
Falling
USB Rising to
UOK
Falling
DC Falling to
DCOK
Going
Open-Drain Propagation Delay
USB Falling to
UOK
Going
Open-Drain Propagation Delay
DC Rising to PON Rising (90%)
USB Rising to PON Rising (90%)
DC Falling to PON Going
Open-Drain Propagation Delay
USB Falling to PON Going
Open-Drain Propagation Delay
USB = open, DC rising to 5V
DC = open, USB rising to 5V
USB = open, 1kΩ pullup
DC = open, 10kΩ pullup
USB = open, DC step to 5V, BATT = 3.6V,
100kΩ pulldown
DC = open, V
USB
step to 5V, V
BATT
= 3.6V,
100kΩ pulldown
USB = open, 100kΩ pulldown
DC = open, 100kΩ pulldown
20
20
2
2
20
20
2
2
ms
ms
µs
µs
ms
ms
µs
µs
CONDITIONS
MIN
TYP
MAX
UNITS
ELECTRICAL CHARACTERISTICS
(V
USB
= V
DC
= V
DCLV
= V
EN
= V
USEL
= 5V, V
BATT
= 4.2V, V
THRM
= V
REF
/ 2, Circuit of Figure 2,
T
A
= -40°C to +85°C,
unless otherwise
noted. Typical values are at T
A
= +25°C.) (Note 4)
PARAMETER
INPUT VOLTAGE RANGES AND INPUT CURRENT
Maximum DC Input Voltage with
Overvoltage Protection
Maximum DC Input Voltage Without
Overvoltage Protection
Maximum Input Voltage for Charging
DC Supply Current
DCLV Operating Voltage Range
DCLV Shutdown Supply Current
USB Input Voltage Range
V
EN
= 0V
USB Supply Current
DCI Input Current
THRM Input Bias Current
V
EN
= 5V, V
DC
= 0V
V
EN
= 5V, V
DC
= 5V
V
EN
= 0V
4.35
V
EN
= 0V
V
EN
= 5V
4.35
Q2 input MOSFET must be in place; charging
occurs only below 6.2V, Figures 3, 4, and 5
DC = DCLV, Q2 input MOSFET not on circuit,
Figure 3
6.0
18
6.5
6.5
4
6
6.00
500
6.50
750
3
300
100
100
V
V
V
mA
V
µA
V
µA
mA
µA
nA
nA
CONDITIONS
MIN
TYP
MAX
UNITS
4
_______________________________________________________________________________________
Dual-Input, USB/AC Adapter, 1-Cell
Li+ Charger with OVP and Thermal Regulation
ELECTRICAL CHARACTERISTICS (continued)
(V
USB
= V
DC
= V
DCLV
= V
EN
= V
USEL
= 5V, V
BATT
= 4.2V, V
THRM
= V
REF
/ 2, Circuit of Figure 2,
T
A
= -40°C to +85°C,
unless otherwise
noted. Typical values are at T
A
= +25°C.) (Note 4)
PARAMETER
BATTERY VOLTAGE
BATT Regulation Voltage
BATT Prequal Voltage Threshold
REF Voltage (Buffered Output)
BATT rising
I
REF
= 0 to 500µA, 4V < V
DC
or V
USB
< 6.5V;
does not affect BATT regulation accuracy
4.1685
2.8
2.94
4.2315
3.2
3.06
V
V
V
CONDITIONS
MIN
TYP
MAX
UNITS
MAX1874
BATTERY CHARGING AND PRECHARGE CURRENT
DCI Voltage Range
DCI Voltage to BATT Current
USB Charging Current
Prequal Charging Current
BATT Input Current
BATT Shutdown Current
THRM COLD Trip Level
THRM HOT Trip Level
THRM Disable Threshold
LOGIC INPUT/OUTPUTS AND GATE DRIVERS
DCOK
Off-Leakage Current
UOK
Off-Leakage Current
CHG
Threshold to Indicate Battery Full,
Battery Current Falling (Note 3)
CHG
Logic-Low Output
CHG
Leakage Current
EN, USEL Logic-Input High Level
EN, USEL Logic-Input Low Level
EN, USEL Input Bias Current
V
DCOK
= 12V, V
DC
= 0V
V
UOK
= 6.5V
DC input (% of charge current set at DCI)
USB input, USEL = 5V
(% of USB charging current)
Sinking 10mA sink
V
CHG
= 6.5V
1.6
0.4
1
8
20
1
1
20
30
0.4
1
%
V
µA
V
V
µA
µA
µA
V
DCI
= V
REF
V
DCI
= V
REF
/ 2
USEL = high
USEL = low
V
BATT
= 2.5V
No DC or USB power, V
BATT
= 4.2V
EN = GND, USB and/or DC powered
(Note 2)
(Note 2)
0.72
0.28
50
40
0.1 x V
REF
930
490
V
REF
1070
565
495
95
70
7.5
2
0.76
0.30
150
V
mA
mA
mA
µA
µA
V
REF
V
REF
mV
THERMISTOR MONITOR AND DIE-TEMPERATURE REGULATION
Note 1:
BYP internally connects to the active power input (DCLV or USB). DCLV takes priority if both inputs are powered.
Note 2:
These limits guarantee +5°C accuracy with 5% accuracy of thermistor beta (3450 nominal) with 2°C of hysteresis.
Note 3:
The
CHG
output does not go high unless charge current is below the indicated threshold (as set by DCI) and the charger is in
voltage-mode operation. In 100mA USB mode,
CHG
goes high when the charger transitions from current to voltage mode.
Note 4:
Specifications to -40°C are guaranteed by design, not production tested.
_______________________________________________________________________________________
5
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