19-4137; Rev 0; 5/08
Overvoltage Protector with
Active Current Limit
General Description
The MAX4978–MAX4981 overvoltage-protection devices
protect low-voltage systems against voltage faults up to
+28V and feature a low 85mΩ R
ON
FET, an active cur-
rent limiter, and lithium-ion battery overcharge protec-
tion (MAX4980/MAX4981). These devices are used to
protect the charger input port on a portable device.
The overvoltage protector feature protects against volt-
ages up to 28V with two different trip thresholds: 5.7V
(MAX4978/MAX4980/MAX4981) and 6.8V (MAX4979).
There is an undervoltage protector with two different trip
thresholds: 4.4V (MAX4978) and 2.63V (MAX4979/
MAX4980/MAX4981).
The overcurrent limiter and battery voltage monitor fea-
tures provide a second layer of protection for a lithium-
ion battery charger. The overcurrent limiter is available
in two different thresholds: 0.9A (MAX4978/MAX4979/
MAX4980) and 1.95A (MAX4981). Once current reach-
es the threshold, it is held for a 20ms blanking time. If
the current is still at the limit after the blanking time, the
FET is turned off, and the device restarts the cycle after
160ms. The battery voltage monitor measures the volt-
age of a lithium-ion battery and disables the FET if the
battery voltage reaches 4.4V (MAX4980/MAX4981).
The MAX4978–MAX4981 are available in a small 8-pin
TDFN (2mm x 3mm) package and are specified over
the extended -40°C to +85°C temperature range.
Features
♦
Input Voltage Protection Up to +28V
♦
Integrated nFET Switch, 85mΩ (typ)
♦
Preset Overvoltage Protection Trip Level
5.7V (typ) (MAX4978/MAX4980/MAX4981)
6.8V (typ) (MAX4979)
♦
Low-Current Undervoltage Lockout Mode
♦
Overcurrent Protection
♦
Internal 160ms (typ) Startup Delay
♦
Thermal-Shutdown Protection
♦
Battery Overcharge Protection
(MAX4980/MAX4981)
♦
Startup Debounce Time Indicator
(MAX4978/MAX4979)
♦
Small, 8-Pin (2mm x 3mm) TDFN Package
MAX4978–MAX4981
Pin Configuration
TOP VIEW
OUT
8
I.C.
7
I.C.
6
GND
5
Applications
Cell Phones
MP3 Players
Digital Still Cameras
PDAs and Palmtop
Devices
MAX4978
MAX4979
MAX4980
MAX4981
*EP
1
2
3
4
EN
IN SDT(BAT) I.C.
TDFN-EP
Typical Application Circuit appears at end of data sheet.
(BAT) IS FOR MAX4980/MAX4981 ONLY.
*EP = EXPOSED PAD. CONNECT EP TO GND.
Ordering Information/Selector Guide
PART
MAX4978ETA+
MAX4979ETA+**
MAX4980ETA+
MAX4981ETA+
PIN-PACKAGE
8 TDFN-EP*
8 TDFN-EP*
8 TDFN-EP*
8 TDFN-EP*
CURRENT
LIMIT (mA)
900
900
900
1950
BATTERY
MONITOR
No
No
Yes
Yes
UVLO
(V)
4.4
2.63
2.63
2.63
OVLO
(V)
5.7
6.8
5.7
5.7
TOP
MARK
AAK
AAL
AAM
AAN
PKG
CODE
T823-1
T823-1
T823-1
T823-1
Note:
All devices specified over the -40°C to +85°C operating temperature range.
+Denotes
a lead-free package.
*EP
= Exposed pad.
**Future
product—contact factory for availability.
________________________________________________________________
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.
Overvoltage Protector with
Active Current Limit
MAX4978–MAX4981
ABSOLUTE MAXIMUM RATINGS
(Voltages referenced to GND.)
IN,
SDT
................................................................. -0.3V to +30V
OUT ........................................................................... -0.3V to IN
EN,
BAT .................................................................. -0.3V to +6V
SDT
Continuous Current ................................................. ±50mA
Continuous Power Dissipation (T
A
= +70°C)
8-Pin 2mm x 3mm TDFN (derate 16.7mW/°C
above +70°C) ........................................................... 1333mW
Junction-to-Case Thermal Resistance (θ
JC
) (Note 1)
8-Pin 2mm x 3mm TDFN ......................................... 10.8°C/W
Junction-to-Ambient Thermal Resistance (θ
JA
) (Note 1)
8-Pin 2mm x 3mm TDFN ............................................ 60°C/W
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
Note 1:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a 4-layer
board. For detailed information on package thermal considerations, refer to
www.maxim-ic.com/thermal-tutorial.
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
IN
= 5.0V, V
EN
= 0V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
Input Voltage Range
Input Supply Current
UVLO Supply Current
Shutdown Supply Current
SYMBOL
V
IN
I
IN
I
UVLO
I
SHDN
I
OUT
< I
LIM_MIN
V
IN
= 2.3V
V
EN
= 5V
MAX4978
IN Undervoltage Lockout
V
UVLO
MAX4979/MAX4980/
MAX4981
V
IN
falling
V
IN
rising
V
IN
falling
V
IN
rising
4.2
4.3
2.5
2.56
2.63
1
MAX4978/MAX4980/
MAX4981
IN Overvoltage Lockout
V
OVLO
MAX4979
IN Overvoltage Lockout Hysteresis
BAT Overvoltage Trip Level
BAT Overvoltage Hysteresis
BAT Input Leakage Current
Switch On-Resistance
I
LKGB
R
ON
V
BOTL
MAX4980/MAX4981, V
BAT
rising
MAX4980/MAX4981
MAX4980/MAX4981, V
BAT
= 4.2V
I
OUT
= 100mA
MAX4978, MAX4979,
MAX4980
Overcurrent Protection Threshold
I
LIM
MAX4981
Thermal Shutdown
T
SHDN
T
A
rising
T
A
=+25°C
T
A
= 0°C to +85°C
T
A
= -40°C to +0°C
T
A
=+25°C
T
A
= -40°C to +85°C
850
800
780
1850
1750
1950
1950
160
85
900
4.3
V
IN
falling
V
IN
rising
V
IN
falling
V
IN
rising
5.5
5.6
6.5
6.65
6.80
1
4.4
1
1
160
950
1000
1000
2050
2150
°C
mA
4.5
6.95
%
V
%
µA
mΩ
5.7
5.8
V
2.70
%
4.4
4.5
V
CONDITIONS
MIN
2.3
130
35
15
TYP
MAX
28
190
60
23
UNITS
V
µA
µA
µA
IN Undervoltage Lockout
Hysteresis
2
_______________________________________________________________________________________
Overvoltage Protector with
Active Current Limit
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 5.0V, V
EN
= 0V, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.) (Note 2)
PARAMETER
Thermal-Shutdown Hysteresis
EN
Input High Voltage
EN
Input Low Voltage
EN
Input Leakage Current
SDT
Output Low Voltage
SDT
Leakage Current
DYNAMIC (Note 3)
IN Debounce Time
Switch Turn-On Time
Switch Turn-Off Time
Current-Limit Blanking Time
Current-Limit Reaction Time
Overcurrent Autoretry Time
t
DEB
t
ON
t
OFF
t
BLANK
t
REAC
t
RETRY
V
UVLO
< V
IN
< V
OVLO
to charge-pump
enable, Figure 1
Time from V
OUT
= 10% of V
IN
to V
OUT
= 90%
of V
IN
, R
L
= 10Ω, C
L
= 10µF
V
IN
< V
UVLO
or V
IN
> V
OVLO
to internal
switch off, R
L
= 1kΩ
Short circuit applied, Figure 1
Short circuit applied
Figure 1
120
15
120
160
1.5
5
20
5
160
200
15
25
200
ms
ms
µs
ms
µs
ms
V
IH
V
IL
I
LKGE
V
OL
I
LKGS
V
EN
= 5.5V or 0V
MAX4978/MAX4979, I
SINK
= 20mA
MAX4978/MAX4979, V
SDT
= 28V,
SDT
deasserted
-1
1.5
0.6
+1
1
1
SYMBOL
CONDITIONS
MIN
TYP
10
MAX
UNITS
°C
V
V
µA
V
µA
MAX4978–MAX4981
Note 2:
All devices are 100% production tested at T
A
= +25°C. Specifications over -40°C to +85°C are guaranteed by design.
Note 3:
All timing is measured using 10% and 90% levels, unless otherwise noted.
_______________________________________________________________________________________
3
Overvoltage Protector with
Active Current Limit
MAX4978–MAX4981
Timing Diagram
t
DEB
OVLO
IN
UVLO
OUT
t
DEB
t
BLANK
t
RETRY
t
BLANK
t
RETRY
t
BLANK
CURRENT LIMIT
LOAD CURRENT
SDT
Figure 1. Timing Diagram
4
_______________________________________________________________________________________
Overvoltage Protector with
Active Current Limit
Typical Operating Characteristics
(V
IN
= 5.0V,
EN
= GND, T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
140
120
100
I
IN
(μA)
80
60
40
20
0
2
7
12
17
V
IN
(V)
22
27
MAX4978
MAX4980/MAX4981
MAX4978-81 toc01
MAX4978–MAX4981
NORMALIZED ON-RESISTANCE
vs. TEMPERATURE
MAX4978-81 toc02
NORMALIZED UVLO THRESHOLD
vs. TEMPERATURE
MAX4978-81 toc03
160
1.3
1.2
1.1
1.0
0.9
0.8
0.7
-40
-15
10
35
60
1.010
NORMALIZED UVLO THRESHOLD
NORMALIZED ON-RESISTANCE
1.005
1.000
0.995
0.990
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
NORMALIZED OVLO THRESHOLD
vs. TEMPERATURE
MAX4978-81 toc04
BATTERY OVERVOLTAGE THRESHOLD
vs. TEMPERATURE
BATTERY OVERVOLTAGE THRESHOLD
MMAX4978-81 toc05
NORMALIZED CURRENT LIMIT
vs. TEMPERATURE
MMAX4978-81 toc06
1.010
NORMALIZED OVLO THRESHOLD
4.50
1.10
1.005
NORMALIZED CURRENT LIMIT
4.45
1.05
1.000
4.40
1.00
0.995
4.35
0.95
0.990
-40
-15
10
35
60
85
TEMPERATURE (°C)
NORMALIZED STARTUP DELAY/AUTORETRY/BLANKING TIME
4.30
-40
-15
10
35
60
85
TEMPERATURE (°C)
0.90
-40
-15
10
35
60
85
TEMPERATURE (°C)
NORMALIZED STARTUP DELAY/AUTORETRY/
BLANKING TIME vs. TEMPERATURE
MAX4978-81 toc07
POWER-UP RESPONSE
MAX4978-81 toc08
OVERVOLTAGE FAULT RESPONSE
MAX4978-81 toc09
1.008
1.006
1.004
1.002
1.000
R
L
= 1kΩ
V
IN
5V/div
V
OUT
5V/div
2V/div
V
OUT
V
IN
0.998
0.996
5V/div
0.994
0.992
-40
-15
10
35
60
85
40ms/div
TEMPERATURE (°C)
4μs/div
V
SDT
2V/div
_______________________________________________________________________________________
5
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