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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 85m RON FET, an active current limiter, and lithium-ion battery overcharge protection (MAX4980/MAX4981). These devices are used to protect the charger input port on a portable device. The overvoltage protector feature protects against voltages 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 features provide a second layer of protection for a lithiumion battery charger. The overcurrent limiter is available in two different thresholds: 0.9A (MAX4978/MAX4979/ MAX4980) and 1.95A (MAX4981). Once current reaches 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 voltage 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 -40C to +85C temperature range.
Features
Input Voltage Protection Up to +28V Integrated nFET Switch, 85m (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 -40C to +85C 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 (TA = +70C) 8-Pin 2mm x 3mm TDFN (derate 16.7mW/C above +70C) ........................................................... 1333mW Junction-to-Case Thermal Resistance (JC) (Note 1) 8-Pin 2mm x 3mm TDFN ......................................... 10.8C/W Junction-to-Ambient Thermal Resistance (JA) (Note 1) 8-Pin 2mm x 3mm TDFN ............................................ 60C/W Operating Temperature Range ......................... -40C to +85C Junction Temperature .................................................... +150C Storage Temperature Range ........................... -65C to +150C Lead Temperature (soldering, 10s) ................................+300C
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
(VIN = 5.0V, VEN = 0V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 2)
PARAMETER Input Voltage Range Input Supply Current UVLO Supply Current Shutdown Supply Current SYMBOL VIN IIN IUVLO ISHDN IOUT < ILIM_MIN VIN = 2.3V V EN = 5V MAX4978 IN Undervoltage Lockout VUVLO MAX4979/MAX4980/ MAX4981 VIN falling VIN rising VIN falling VIN rising 4.2 4.3 2.5 2.56 2.63 1 MAX4978/MAX4980/ MAX4981 IN Overvoltage Lockout VOVLO MAX4979 IN Overvoltage Lockout Hysteresis BAT Overvoltage Trip Level BAT Overvoltage Hysteresis BAT Input Leakage Current Switch On-Resistance ILKGB RON VBOTL MAX4980/MAX4981, VBAT rising MAX4980/MAX4981 MAX4980/MAX4981, VBAT = 4.2V IOUT = 100mA MAX4978, MAX4979, MAX4980 Overcurrent Protection Threshold ILIM MAX4981 Thermal Shutdown TSHDN TA rising TA=+25C TA= 0C to +85C TA= -40C to +0C TA=+25C TA= -40C to +85C 850 800 780 1850 1750 1950 1950 160 85 900 4.3 VIN falling VIN rising VIN falling VIN 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 % A m 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 A A A
IN Undervoltage Lockout Hysteresis
2
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Overvoltage Protector with Active Current Limit
ELECTRICAL CHARACTERISTICS (continued)
(VIN = 5.0V, VEN = 0V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (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 tDEB tON tOFF tBLANK tREAC tRETRY VUVLO < VIN < VOVLO to charge-pump enable, Figure 1 Time from VOUT = 10% of VIN to VOUT = 90% of VIN, RL = 10, CL = 10F VIN < VUVLO or VIN > VOVLO to internal switch off, RL = 1k 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 s ms s ms VIH VIL ILKGE VOL ILKGS V EN = 5.5V or 0V MAX4978/MAX4979, ISINK = 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 A V A
MAX4978-MAX4981
Note 2: All devices are 100% production tested at TA = +25C. Specifications over -40C to +85C are guaranteed by design. Note 3: All timing is measured using 10% and 90% levels, unless otherwise noted.
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3
Overvoltage Protector with Active Current Limit MAX4978-MAX4981
Timing Diagram
tDEB OVLO IN UVLO OUT
tDEB
tBLANK
tRETRY
tBLANK
tRETRY
tBLANK
CURRENT LIMIT LOAD CURRENT
SDT
Figure 1. Timing Diagram
4
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Overvoltage Protector with Active Current Limit
Typical Operating Characteristics
(VIN = 5.0V, EN = GND, TA = +25C, unless otherwise noted.)
SUPPLY CURRENT vs. SUPPLY VOLTAGE
140 120 100 IIN (A) 80 60 40 20 0 2 7 12 17 VIN (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
RL = 1k VIN 5V/div VOUT 5V/div 2V/div VOUT VIN
0.998 0.996 5V/div 0.994 0.992 -40 -15 10 35 60 85 40ms/div TEMPERATURE (C) 4s/div VSDT 2V/div
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5
Overvoltage Protector with Active Current Limit MAX4978-MAX4981
Typical Operating Characteristics (continued)
(VIN = 5.0V, EN = GND, TA = +25C, unless otherwise noted.)
UNDERVOLTAGE FAULT RESPONSE
MAX4978-81 toc10
BATTERY OVERVOLTAGE FAULT RESPONSE
MAX4978-81 toc11
SHORT-CIRCUIT RESPONSE
MAX4978-81toc12
RL = 1k 2V/div 2V/div VIN VBAT 5V/div
VIN VOUT
VSDT VOUT 2V/div 2V/div 1A/div VOUT 5V/div IOUT
4s/div
2s/div
100ms/div
Pin Description
PIN MAX4978/ MAX4979 MAX4980/ MAX4981 NAME FUNCTION Supply Voltage Input. IN powers the charge pump required to turn on the internal FET. When the correct adapter is plugged in, a 160ms debounce timer prevents a false turn-on of the internal FET. Bypass IN to GND with a 1F ceramic capacitor as close to the device as possible to enable 15kV (HBM) ESD protection. Startup Debounce Time Indicator. SDT is an active-low open-drain output that asserts low during the debounce/autoretry time. Battery Monitor Input. Connect BAT to Li-ion battery terminal. Bypass BAT to GND with a 1F ceramic capacitor as close to the device as possible to enable 15kV (HBM) ESD protection. Internally Connected. Connect I.C. to GND. Active-Low Enable Input. Drive EN low for normal operation. Drive EN high to disable the device. Ground Output Voltage. Output of internal FET. Exposed Pad. Internally connected to GND. Connect EP to a large ground plane to maximize thermal performance. Do not use EP as the sole GND connection.
1
1
IN
2 -- 3, 6, 7 4 5 8 --
-- 2 3, 6, 7 4 5 8 --
SDT BAT I.C. EN GND OUT EP
6
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Overvoltage Protector with Active Current Limit
MAX4978/MAX4979 Functional Diagram
MAX4978-MAX4981
IN nFET
OUT
BANDGAP REFERENCE OVLO + + UVLO CONTROL LOGIC
CHARGE PUMP
EN
MAX4978 MAX4979
SDT GND
MAX4980/MAX4981 Functional Diagram
IN nFET
OUT
BANDGAP REFERENCE OVLO + + UVLO CONTROL LOGIC
CHARGE PUMP
EN
BAT
_______________________________________________________________________________________
+
-
MAX4980 MAX4981
GND
7
Overvoltage Protector with Active Current Limit MAX4978-MAX4981
Detailed Description
The MAX4978-MAX4981 family of devices is a combination of an overvoltage protector, overcurrent limiter, and lithium-ion battery overcharge protector (MAX4980/ MAX4981). These devices feature a low 85m (typ) RON FET and are used to protect the charger input port on a portable device. If the input voltage exceeds the overvoltage threshold (OVLO) or falls below the undervoltage threshold (UVLO), the FET is turned off to prevent damage to the protected components. The internal charge pump's 160ms debounce time prevents false turn-on of the internal FET during startup. SDT is an active-low open-drain output that asserts low during the debounce time after a valid voltage is applied to the input (MAX4978/MAX4979). The MAX4978-MAX4981 feature an overcurrent limiter as a second layer of protection for a lithium-ion battery charger that limits current to a 900mA (MAX4978/ MAX4979/MAX4980) or 1950mA (MAX4981) threshold for a 20ms blanking time. At the end of the blanking time, if current is still at the threshold, the FET is turned off and the device restarts the cycle after 160ms. The battery voltage monitor measures the voltage of a lithium-ion battery and disables the FET if the battery voltage exceeds 4.4V (MAX4980/MAX4981).
Battery Overcharge Protector (MAX4980/MAX4981)
The MAX4980/MAX4981 feature a battery overcharge protection input (BAT) that triggers a voltage fault, turning off the FET, when VBAT exceeds 4.4V.
Startup Debounce Time Indicator (SDT) (MAX4978/MAX4979)
SDT is an open-drain output that asserts low during the startup debounce time and during the autoretry time. SDT returns to high impedance once the charge pump turns on. This feature is useful for discharging the AC adapter capacitance during the startup debounce time (Figures 1, 2).
Thermal Shutdown Protection
The MAX4978-MAX4981 have a thermal-shutdown feature to protect the devices from overheating. The device immediately turns off when the junction temperature exceeds +160C (typ). These devices exit thermal shutdown after the junction temperature cools by 10C (typ).
EN Input
EN is an active-low enable input. Drive EN low for normal operation. Drive EN high to disable the device.
Autoretry
When the current-limit threshold is reached, the tBLANK timer begins counting. The timer resets if the overcurrent condition disappears before tBLANK has elapsed. A retry time delay, tRETRY, is started immediately after tBLANK has elapsed and during that time, the FET is off. At the end of tRETRY, the FET is turned on again. If the fault still exists, the cycle is repeated. If the fault has been removed, the FET stays on.
Applications Information
IN Bypass Capacitor
For most applications, bypass IN to GND with a 1F ceramic capacitor as close to the device as possible to enable 15kV (HBM) ESD protection on IN. If the power source has significant inductance due to long lead length, take care to prevent overshoots due to the LC tank circuit and provide protection if necessary to prevent exceeding the 30V absolute maximum rating on IN.
Undervoltage Lockout (UVLO)
The MAX4978 has a 4.4V UVLO threshold, while the MAX4979/MAX4980/MAX4981 have a 2.63V UVLO threshold. When an undervoltage lockout condition occurs with high load current, the voltage at the input to the UVLO comparator may recover due to internal parasitic resistance causing the device to restart.
BAT Bypass Capacitor
For most applications, bypass BAT to GND with a 1F ceramic capacitor as close to the device as possible to enable 15kV (HBM) ESD protection on BAT. If high ESD protection is not necessary, no capacitor is required on BAT.
ESD Test Conditions
ESD performance depends on a number of conditions. The MAX4978-MAX4981 are specified for 15kV (HBM) typical ESD resistance on IN and BAT when IN and BAT are bypassed to ground with a 1F low ESR ceramic capacitor. Contact Maxim for a reliability report that documents test setup, methodology, and results.
Overvoltage Lockout (OVLO)
The MAX4979 has a 6.8V OVLO threshold, while the MAX4978/MAX4980/MAX4981 have a 5.7V OVLO threshold.
8
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Overvoltage Protector with Active Current Limit MAX4978-MAX4981
LONG WIRE RESISTANCE AC-DC CONVERTER 5V AC ADAPTER CHARGE PUMP C0NTROL ~0.5 1F CHARGER IN nFET OUT PHONE LOADS
BANDGAP REFERENCE OVLO 1k + + UVLO CONTROL LOGIC
EN
MAX4978/ MAX4979
SDT GND
Figure 2. Typical Application Circuit with SDT
RC 1M CHARGE CURRENTLIMIT RESISTOR HIGHVOLTAGE DC SOURCE
RD 1.5k DISCHARGE RESISTANCE DEVICE UNDER TEST
IP 100% 90% AMPERES
Ir
PEAK-TO-PEAK RINGING (NOT DRAWN TO SCALE)
Cs 100pF
STORAGE CAPACITOR
36.8% 10% 0 0 tRL TIME tDL CURRENT WAVEFORM
Figure 3. Human Body ESD Test Model
Figure 4. Human Body Current Waveform
Human Body Model
Figure 3 shows the Human Body Model, and Figure 4 shows the current waveform it generates when discharged into a low impedance. This model consists of a 100pF capacitor charged to the ESD voltage of interest that is then discharged into the device through a 1.5k resistor. PROCESS: BiCMOS
Chip Information
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9
Overvoltage Protector with Active Current Limit MAX4978-MAX4981
Typical Application Circuit
CHARGER 5V AC ADAPTER IN 1F nFET OUT PHONE LOADS
BANDGAP REFERENCE OVLO + + UVLO CONTROL LOGIC
CHARGE PUMP
C0NTROL
EN
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages. PACKAGE TYPE 8 TDFN-EP PACKAGE CODE T823-1 DOCUMENT NO. 21-0174
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.
10 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
+
BAT
-
MAX4980 MAX4981
GND

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