General Description
The MAX4943–MAX4946/MAX4949 family of overvolt-
age-protection devices feature a low 80mΩ(typ) RON
internal FET and protect low-voltage systems against
voltage faults up to +28V. These devices also drive an
optional external pFET to protect down to -28V when
connected to a load with reverse current protection.
When the input voltage exceeds the overvoltage thresh-
old, the internal FET is turned off to prevent damage to
the protected components.
All switches feature a minimum 1.2A current-limit pro-
tection. During a short-circuit occurrence, the
MAX4944B and MAX4945B place the switch in a
latchoff state where the switch turns off and remains off.
For the autoretry devices, the switch turns off and con-
tinuously checks after a 15ms (typ) retry time.
The overvoltage thresholds (OVLO) are preset to 7.4V,
6.35V, 5.8V, 4.56V, or 8.9V. The undervoltage-lockout
(UVLO) thresholds are preset to 2.45V and 4.15V.
When the input voltage drops below the undervoltage-
lockout (UVLO) threshold, the devices enter a low-
current standby mode. (See the
Ordering Information/
Selector Guide
for more details on UVLO/OVLO).
All devices are offered in a small, 8-pin µDFN (2mm x
2mm) package and are specified for operation over the
-40°C to +85°C temperature range.
Applications
Features
♦Input Voltage Protection Up to +28V
♦Integrated nFET Switch
♦Preset Overvoltage Protection Trip Level
7.40V (MAX4943)
6.35V (MAX4944_)
5.80V (MAX4945_)
4.56V (MAX4946)
8.90V (MAX4949)
♦Low-Current Undervoltage-Lockout Mode
♦Short-Circuit Protection (Latchoff/Autoretry)
♦Internal 15ms (typ) Startup Delay and Retry Times
♦Input Voltage Power-Good Logic Output
♦Thermal-Shutdown Protection
♦Small, 8-Pin (2mm x 2mm) µDFN Package
MAX4943–MAX4946/MAX4944L/MAX4945A/MAX4945L/MAX4949
Overvoltage-Protection Controllers with
Internal FET
________________________________________________________________
Maxim Integrated Products
1
19-0552; Rev 3; 6/08
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.
Ordering Information/Selector Guide
PART
PIN-PACKAGE TOP MARK PKG CODE
UVLO (V) OVLO (V)
OVERCURRENT MODE
MAX4943ELA+T* 8 µDFN ABA L822-1 4.15 7.40 Retry
MAX4944ELA+T 8 µDFN ABB L822-1 4.15 6.35 Retry
MAX4944BELA+T* 8 µDFN ABC L822-1 4.15 6.35 Latchoff
MAX4944LELA+T 8 µDFN ABD L822-1 2.45 6.35 Retry
MAX4945ELA+T** 8 µDFN ABE L822-1 4.15 5.80 Retry
MAX4945AELA+T**
8 µDFN ADW L822-1 4.15 5.80 Retry
MAX4945BELA+T* 8 µDFN ABF L822-1 4.15 5.80 Latchoff
MAX4945LELA+T 8 µDFN ABG L822-1 2.45 5.80 Retry
MAX4946ELA+T 8 µDFN ABH L822-1 2.45 4.56 Retry
MAX4949ELA+T 8 µDFN ADT L822-1 2.45 8.90 Latchoff
Note: All devices are specified over the -40°C to +85°C operating temperature range.
+
Denotes a lead-free/RoHS-compliant package.
T
= Tape-and-reel package.
*
Future product—contact factory for availability.
**
The OVLO is 6.10V (max) for the MAX4945ELA+T and .6.0V (max) for the MAX4945AELA+T.
TOP VIEW
1
2
8
7
3
4
6
5
OUT
GND
ACOK
OUT
OUT
IN
GP
IN MAX4943–
MAX4946/
MAX4944L/
MAX4945A/
MAX4945L/
MAX4949
+
µDFN
2mm × 2mm
Pin Configuration
Cell Phones
Digital Still Cameras
PDAs and Palmtop Devices
MP3 Players
MAX4943–MAX4946/MAX4944L/MAX4945A/MAX4945L/MAX4949
Overvoltage-Protection Controllers with
Internal FET
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
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 ............................................................................-0.3V to +30V
OUT ...............................................................-0.3V to (IN + 0.3V)
GP...........................................................................-0.3V to +12V
IN to GP ..................................................................-0.3V to +22V
ACOK .......................................................................-0.3V to +6V
Continuous Power Dissipation (TA= +70°C)
8-Pin µDFN (derate 4.8mW/°C above +70°C) ..............381mW
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
ELECTRICAL CHARACTERISTICS
(VIN = +5V (MAX4943/MAX4944_/MAX4945_/MAX4949), VIN = +3V (MAX4946), TA= -40°C to +85°C, unless otherwise noted.
Typical values are at TA= +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
Input Voltage Range VIN 2.2
28.0
V
VIN = 3V (MAX4946) 50 150
Input Supply Current IIN VIN = 5V, all remaining parts 50 150 µA
UVLO Supply Current IUVLO VIN = 2.2V 30 µA
MAX4943/MAX4944/
MAX4944B/MAX4945/
MAX4945A/ MAX4945B
3.90 4.15 4.40
IN Undervoltage Lockout VUVLO (VIN falling)
MAX4944L/MAX4945L/
MAX4946/MAX4949
2.30 2.45 2.60
V
IN Undervoltage-Lockout
Hysteresis 1%
MAX4943
7.00
7.4
7.80
MAX4944_
6.00 6.35 6.70
MAX4945/MAX4945B/L 5.50 5.80 6.10
MAX4945A
5.50 5.80 6.00
MAX4946
4.30 4.56 4.82
Overvoltage Trip Level VOVLO (VIN rising)
MAX4949
8.20 8.90 9.60
V
IN Overvoltage Hysteresis 1%
VIN = 3V (MAX4946), IOUT = 1A 80 200
Switch On-Resistance RON VIN = 5V, all remaining parts, IOUT = 1A 80 200 mΩ
TA = +25°C 1.2 1.7 4.0
MAX4943–MAX4946
TA = TMIN to TMAX 1.2 1.7 4.0
TA = +25°C 2.0 3.5 5.0
Overcurrent Protection Threshold
ILIM
MAX4949 TA = TMIN to TMAX 2.0 3.0 5.0
A
GP Clamp Voltage IGPD (VIN - VGP), VIN = 28V 13 16 19 V
GP Pulldown Resistor RGPD 50 kΩ
MAX4943–MAX4946/MAX4944L/MAX4945A/MAX4945L/MAX4949
Overvoltage-Protection Controllers with
Internal FET
_______________________________________________________________________________________ 3
PARAMETER
SYMBOL
CONDITIONS
MIN TYP MAX UNITS
ACOK Output-Low Voltage VOL ISINK = 1mA 0.4 V
ACOK High-Leakage Current V ACOK = 5.5V 1 µA
Thermal Shutdown
+175
°C
Thermal-Shutdown Hysteresis 40 °C
Load Capacitor 300 µF
TIMING CHARACTERISTICS (Figure 2)
Debounce Time tINDBC Time from VUVLO < VIN < VOVLO to charge-
pump enable 15 ms
Switch Turn-On Time tON
VUVLO < VIN < VOVLO, RLOAD = 100Ω,
CLOAD = 300µF, VOUT = from 10% of VOUT
to 80% of VOUT
6ms
ACOK Assertion Time t ACOK VUVLO < VIN < VOVLO, to ACOK low 30 ms
VIN < VUVLO or VIN > VOVLO, to internal
switch off 220µs
Switch Turn-Off Time tOFF
Overcurrent fault to internal switch turn-off 10 µs
Autoretry Time tRETRY From overcurrent fault to internal switch
turn-on 15 ms
ELECTRICAL CHARACTERISTICS (continued)
(VIN = +5V (MAX4943/MAX4944_/MAX4945_/MAX4949), VIN = +3V (MAX4946), TA= -40°C to +85°C, unless otherwise noted.
Typical values are at TA= +25°C.) (Note 1)
Note 1: All specifications are 100% production tested at TA= +25°C, unless otherwise noted. Specifications are over -40°C to +85°C
and are guaranteed by design.
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
0
90
60
30
120
150
180
210
240
270
300
2106141822
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX4943 toc01
SUPPLY VOLTAGE (V)
SUPPLY CURRENT (nA)
26
MAX4944
0
60
40
20
80
100
120
140
RON
vs. TEMPERATURE
MAX4943 toc02
TEMPERATURE (°C)
RON (mΩ)
-40 10-15 356085
0.990
0.996
0.994
0.992
0.998
1.000
1.002
1.004
1.006
1.008
1.010
-40 10-15 35 60 85
NORMALIZED UVLO THRESHOLD
vs. TEMPERATURE
MAX4943 toc03
TEMPERATURE (°C)
NORMALIZED UVLO THRESHOLD
MAX4943–MAX4946/MAX4944L/MAX4945A/MAX4945L/MAX4949
Overvoltage-Protection Controllers with
Internal FET
4 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
0.990
0.996
0.994
0.992
0.998
1.000
1.002
1.004
1.006
1.008
1.010
-40 10-15 35 60 85
NORMALIZED OVLO THRESHOLD
vs. TEMPERATURE
MAX4943 toc04
TEMPERATURE (°C)
NORMALIZED OVLO THRESHOLD
ACOK ASSERTION TIME
vs. TEMPERATURE
MAX4943 toc05
TEMPERATURE (°C)
ACOK ASSERTION TIME (ms)
603510-15
32
34
36
38
40
30
-40 85
15
19
17
21
23
25
-40 10-15 35 60 85
DEBOUNCE TIME
vs. TEMPERATURE
MAX4943 toc06
TEMPERATURE (°C)
DEBOUNCE TIME (ms)
10ms/div
POWER-UP RESPONSE
ADAPTER
5V/div
MAX4943 toc07
VIN
5V/div
VOUT
5V/div
VACOK
5V/div
IOUT
2A/div
4μs/div
UNDERVOLTAGE FAULT RESPONSE
ADAPTER
2V/div
MAX4943 toc08
VIN
2V/div
VOUT
5V/div
VACOK
5V/div
IOUT
1A/div
5V
3V
5V
3V
0
0
0
1μs/div
SHORT-CIRCUIT FAULT RESPONSE
ADAPTER
2V/div
MAX4943 toc09
VIN
5V/div
VOUT
5V/div
VACOK
5V/div
IOUT
10A/div
CIN = 1000μF
10μs/div
OVERCURRENT DURATION TIME
(DURING AUTORETRY)
MAX4943 toc10
VOUT
1V/div
IOUT
1A/div
RLOAD = 1Ω
COUT = 0.1μF
Detailed Description
The MAX4943–MAX4946/MAX4949 overvoltage-protec-
tion devices feature a low RON internal FET and protect
low-voltage systems against voltage faults up to +28V. If
the input voltage exceeds the overvoltage threshold, the
internal MOSFET is turned off to prevent damage to the
protected components. These devices also drive an
optional external pFET to protect down to -28V. If the
adapter voltage drops below ground, the pFET turns off
to prevent damage to the protected components due to
negative voltage exposure. The internal charge pump’s
15ms (typ) debounce time prevents false turn-on of the
internal switch during startup. An open-drain, active-low
logic output is available to signal that a successful
power-up has occurred.
MAX4943–MAX4946/MAX4944L/MAX4945A/MAX4945L/MAX4949
Overvoltage-Protection Controllers with
Internal FET
_______________________________________________________________________________________ 5
Pin Description
PIN NAME FUNCTION
1, 2 IN
Voltage Input. IN powers the charge pump required to turn on the internal switch. When the correct
adapter is plugged in, a 15ms (typ) debouncer prevents false turn-on of the internal switch. Bypass
IN to GND with a 1µF ceramic capacitor as close as possible to the device to enable ±15kV (HBM)
ESD protection on IN.
3 GP pFET Gate-Drive Output. GP pulls the external pFET gate down when the input is above ground.
4ACOK
Active-Low Open-Drain Adapter-Voltage Indicator Output. ACOK is driven low after the adapter
voltage is stable between VUVLO and VOVLO for 30ms (typ). Connect a pullup resistor from ACOK to
the logic I/O voltage of the host system.
5 GND Ground
6, 7, 8 OUT Output Voltage. Output of internal switch. Short all pins together for proper operation.
GP
OUT
VOVLO
15ms (typ)
DEBOUNCE
TIMER AND
RETRY TIME
30ms (typ)
TIMER
OSCILLATOR
CHARGE
PUMP
OVERCURRENT
OR
THERMAL
FAULTS
IN
GND
CHARGE-PUMP
ENABLED
VUVLO
ACOK
MAX4943–MAX4946/MAX4944L/
MAX4945L/MAX4949
+
-
+
-
RESET
RESET
Figure 1. Functional Diagram
MAX4943–MAX4946/MAX4944L/MAX4945A/MAX4945L/MAX4949
Device Operation
The MAX4943–MAX4946/MAX4949 have an internal
oscillator and charge pump that control the turn-on
of the internal switch. The internal oscillator controls
the timers that enable the turn-on of the charge pump
and controls the state of the open-drain ACOK
output. If VIN < VUVLO or if VIN >VOVLO, the internal
oscillator remains off, thus disabling the charge pump.
If VUVLO < VIN < VOVLO, the internal charge pump is
enabled. The charge-pump startup, after a 15ms (typ)
internal delay, turns on the internal switch (see Figure 2).
ACOK is held high during startup until the ACOK 30ms
(typ) blanking period expires. At this point, the device is
in its on state.
At any time, if VIN drops below VUVLO or rises above
VOVLO, ACOK is pulled high and the charge pump
is disabled.
Internal Switch
The MAX4943–MAX4946/MAX4949 incorporate an
internal nFET with a 80mΩ(typ) RON. The switch is
internally driven by a charge pump that generates a 5V
voltage above the input voltage. The internal switch is
equipped with 1.2A (min) current-limit protection that
turns off the switch within 10µs (typ) during an overcur-
rent fault condition.
Autoretry
The MAX4943–MAX4946 have an overcurrent autoretry
function that turns on the switch again after a 15ms (typ)
retry time (see Figure 3). If the faulty load condition is still
present after the blanking time, the switch turns off again
and the cycle is repeated. The fast turn-off time and
15ms retry time result in a very low duty cycle to keep
power consumption low. If the faulty load condition is not
present, the switch remains on.
Latch
The MAX4944B/MAX4945B/MAX4949 do not have the
autoretry function, and the switch latches off after an
overcurrent fault. The switch remains off until the over-
current fault has been removed. The switch turns back
on when the adapter voltage goes below VUVLO and
then returns to the valid operating range.
Overvoltage-Protection Controllers with
Internal FET
6 _______________________________________________________________________________________
OVLO
UVLO
tINDBC
tON
IN
OUT
ACOK
tINDBC
tOFF
tINDBC
80% VIN
tACOK
tOFF
tACOK
10% VIN
Figure 2. Timing Diagram
GP GATE Drive
When the input voltage goes above ground, GP pulls
low and turns on the pFET. An internal clamp protects
the pFET by ensuring that the GP to IN voltage does not
exceed 19V (max) when the input (IN) rises to +28V.
Undervoltage Lockout (UVLO)
The MAX4944L/MAX4945L/MAX4946/MAX4949 have a
2.45V (typ) undervoltage-lockout threshold (VUVLO),
while the remaining devices have a 4.15V (typ) VUVLO
threshold. When VIN is less than VUVLO, ACOK is high
impedance.
Overvoltage-Lockout Thresholds (OVLO)
The MAX4943 has a 7.4V (typ) overvoltage threshold
(VOVLO), the MAX4944_ has a 6.35V (typ) VOVLO
threshold, the MAX4945_ has a 5.80V (typ) VOVLO
threshold, the MAX4946 has a 4.56V (typ) VOVLO
threshold, and the MAX4949 has a 8.90V (typ) VOVLO
threshold. When VIN is greater than OVLO, ACOK is
high impedance.
ACOK
ACOK is an active-low, open-drain output that asserts
low when VUVLO < VIN < VOVLO for the 30ms (typ) peri-
od. Connect a pullup resistor from ACOK to the logic
I/O voltage of the host system. During a short-circuit
fault, ACOK may deassert due to VIN not being in the
valid operating voltage range.
Thermal-Shutdown Protection
The MAX4943–MAX4946/MAX4949 feature thermal-shut-
down circuitry. The internal switch turns off when the junc-
tion temperature exceeds +175°C (typ) and immediately
goes into a fault mode. The device exits thermal shut-
down after the junction temperature cools by 40°C (typ).
Applications Information
IN Bypass Capacitor
For most applications, bypass IN to GND with a 1µF
ceramic capacitor as close as possible to the device to
enable ±15kV (HBM) ESD protection on the pin. If
±15kV is not required, there is no capacitor required at
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 nec-
essary to prevent exceeding the +30V absolute maxi-
mum rating on IN.
Reverse Polarity Protection
The optional external pFET can provide reverse polarity
protection down to -28V (for a 30V pFET), if the protect-
MAX4943–MAX4946/MAX4944L/MAX4945A/MAX4945L/MAX4949
Overvoltage-Protection Controllers with
Internal FET
_______________________________________________________________________________________ 7
SWITCH ON
SWITCH OFF
CURRENT
THROUGH
SWITCH ILIM
tOFF
tRETRY
SWITCH ON
Figure 3. Autoretry Timing Diagram
CHARGE-CURRENT-
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Cs
100pF
RC
1MΩ
RD
1.5kΩ
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
Figure 4. Human Body ESD Test Model
IP 100%
90%
36.8%
tRL TIME
tDL
CURRENT WAVEFORM
PEAK-TO-PEAK RINGING
(NOT DRAWN TO SCALE)
Ir
10%
0
0
AMPERES
Figure 5. Human Body Current Waveform
MAX4943–MAX4946/MAX4944L/MAX4945A/MAX4945L/MAX4949
ed device does not allow current to flow into OUT. The
pFET is turned off when the voltage between GP and IN
is less than the pFET gate threshold voltage.
ESD Test Conditions
ESD performance depends on a number of conditions.
The MAX4943–MAX4946/MAX4949 are specified for
±15kV (HBM) typical ESD resistance on IN when IN is
bypassed to ground with a 1µF ceramic capacitor.
Human Body Model
Figure 4 shows the Human Body Model and Figure 5
shows the current waveform it generates when dis-
charged into a low impedance. This model consists of a
100pF capacitor charged to the ESD voltage of interest,
which is then discharged into the device through a
1.5kΩresistor.
IEC 61000-4-2
The IEC 61000-4-2 standard covers ESD testing and
performance of finished equipment. It does not specifi-
cally refer to integrated circuits. The MAX4943–
MAX4946/MAX4949 are specified for ±15kV Air-Gap
Discharge and ±8kV Contact Discharge IEC 61000-4-2
on the IN pin when IN is bypassed to ground with a 1µF
ceramic capacitor.
The major difference between tests done using the
Human Body Model and IEC 61000-4-2 is a higher peak
current in IEC 61000-4-2, due to lower series resistance.
Hence, the ESD withstand voltage measured to IEC
61000-4-2 generally is lower than that measured using the
Human Body Model. Figure 6 shows the IEC 61000-4-2
model. The Contact Discharge method connects the
probe to the device before the probe is charged. The
Air-Gap Discharge test involves approaching the device
with a charged probe.
Chip Information
PROCESS: BiCMOS
Overvoltage-Protection Controllers with
Internal FET
8 _______________________________________________________________________________________
CHARGE-CURRENT-
LIMIT RESISTOR
DISCHARGE
RESISTANCE
STORAGE
CAPACITOR
Cs
150pF
RC
50MΩ TO 100MΩ
RD
330Ω
HIGH-
VOLTAGE
DC
SOURCE
DEVICE
UNDER
TEST
Figure 6. IEC 61000-4-2 ESD Test Model
5V AC
ADAPTER
15ms (typ)
DEBOUNCE
CHARGE
PUMP
GP IN
OUT
ACOK
CHARGER
DC-DC
CONVERTER
VI/0
GND
TO μC
30ms (typ)
TIMER
MAX4943–MAX4946/MAX4944L/
MAX4945L/MAX4949
1μF
Typical Operating Circuit
MAX4943–MAX4946/MAX4944L/MAX4945A/MAX4945L/MAX4949
Overvoltage-Protection Controllers with
Internal FET
_______________________________________________________________________________________ 9
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
8 µDFN L822-1 21-0164
Package Information
For the latest package outline information and land patterns, go to www.maxim-ic.com/packages.
MAX4943–MAX4946/MAX4944L/MAX4945A/MAX4945L/MAX4949
Overvoltage-Protection Controllers with
Internal FET
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
© 2008 Maxim Integrated Products is a registered trademark of Maxim Integrated Products, Inc.
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
27/07— 1, 2, 3
36/08
Added MAX4945A to the Ordering Information/Selector Guide and Electrical
Characterstics tables 1, 2
