19-2550; Rev 3; 2/10
Single USB Switch with Autoreset and
Fault Blanking in Tiny TDFN
General Description
The MAX1946 single current-limited switch with auto-
reset supplies a guaranteed 500mA load in accordance
with USB specifications. The MAX1946 operates from a
2.7V to 5.5V input supply and consumes only 40µA of
quiescent current when operating and only 3µA in shut-
down. Selectable active-high/active-low control logic
and shutdown control provide additional flexibility. An
autoreset feature latches the switch off in the event of a
short circuit, saving system power. The switch reacti-
vates upon removal of the shorted condition.
The MAX1946 provides several safety features to pro-
tect the USB port. Built-in thermal-overload protection
turns off the switch when the die temperature exceeds
+160°C. Accurate internal current-limiting circuitry pro-
tects the input supply against both overload and short-
circuit conditions. An open-drain fault signal, (FAULT),
notifies the microprocessor (µP) when a thermal over-
load, current-limit, undervoltage lockout (UVLO), or
short-circuit fault occurs. A 20ms fault-blanking feature
enables the circuit to ignore momentary faults, such as
those caused when hot-swapping a capacitive load,
preventing false alarms to the host system. The fault-
blanking feature prevents fault signals from being
issued when the device powers up the load.
The MAX1946 is available in a space-saving 8-pin
(3mm x 3mm) TDFN package and operates over the
extended (-40°C to +85°C) temperature range.
Features
o
Single USB Switch in 3mm x 3mm Package
o
Autoreset Feature Saves System Power
o
Guaranteed 500mA Load Current
o
Built-In 20ms Fault-Blanking Circuitry
o
Active-High or Active-Low Control Logic
o
Fully Compliant to USB Specifications
o
2.7V to 5.5V Input Voltage Range
o
Fault-Indicator Output
o
Thermal-Overload Protection
MAX1946
Ordering Information
PART
MAX1946ETA+
TEMP RANGE
-40°C to +85°C
PIN-
PACKAGE
8 TDFN-EP*
TOP MARK
ACQ
Applications
USB Ports and USB Hubs
Notebook and Desktop Computers
PDAs and Palmtop Computers
Digital Cameras
Docking Stations
+Denotes
a lead(Pb)-free/RoHS-compliant package.
*EP
= Exposed paddle.
Pin Configuration
TOP VIEW
+
FAULT
1
GND
2
OUT
3
OUT
4
8
SEL
INPUT
2.7V TO 5.5V
Typical Operating Circuit
IN
IN
FAULT
MAX1946
7
ON
6
IN
5
IN
ACTIVE HIGH
ACTIVE LOW
SELECTABLE
ON
SEL
GND
MAX1946
OUT
OUT
TDFN
________________________________________________________________
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.
Single USB Switch with Autoreset and
Fault Blanking in Tiny TDFN
MAX1946
ABSOLUTE MAXIMUM RATINGS
IN, ON, OUT, SEL to GND........................................-0.3V to +6V
FAULT
to GND .............................................-0.3V to (V
IN
+ 0.3V)
IN to OUT..................................................................-0.3V to +6V
OUT Continuous Switch Current (internally limited)..............1.3A
FAULT
DC Current ..............................................................10mA
Continuous Power Dissipation (T
A
= +70°C)
Exposed Pad Must be Soldered to PC Board
8-Pin TDFN (derate 23.8mW/°C above +70°C) .........1905mW
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
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
= 5V, C
IN
= 0.1µF, C
OUT
= 1µF,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Note1)
PARAMETER
Supply Voltage Range
Switch On-Resistance
Standby Supply Current
Quiescent Supply Current
OUT Off-Leakage Current
Undervoltage Lockout Threshold
Continuous Load Current
Continuous Current Limit
Short-Circuit Current Limit
Short-Circuit Detect Threshold
Continuous Current-Limit
Blanking Timeout Period
Short-Circuit Blanking Timeout
Period
Turn-On Delay
Output Rise Time
Turn-Off Delay
Output Fall Time
Thermal-Shutdown Threshold
t
ON
t
RISE
t
OFF
t
FALL
I
LIM
I
SC
V
IN_
- V
OUT
= 0.5V
V
OUT
= 0 (I
OUT
pulsing)
(Note 2)
From continuous current-limit condition to
FAULT
asserted
From short-circuit current-limit condition to
FAULT
asserted
R
OUT
= 10Ω, time from ON to 10% of V
OUT
,
does not include rise time
R
OUT
= 10Ω, from 10% to 90% of V
OUT
R
OUT
= 10Ω, time from ON to 90% of V
OUT
,
does not include fall time
R
OUT
= 10Ω, from 90% to 10% of V
OUT
15
o
C hysteresis
10
7.5
0.25
I
IN
I
LKG
V
ULVO
SYMBOL
V
IN
V
IN
= 5, T
A
= +25°C
R
ON
V
IN
= 5V
V
IN
= 3.3V
Switch disabled
Switch enabled, I
OUT
= 0
Switch disabled, V
OUT
= 0, T
A
= +25°C
Switch disabled, V
OUT
= 0, T
A
= +85°C
Rising edge, 3% hysteresis
2.3
500
0.74
0.8
1.1
1.2
0.35
1
20
18
0.6
1.2
0.8
3
160
2
35
35.0
1.50
1.20
1.6
3
40
0.01
0.2
2.5
2.7
CONDITIONS
MIN
2.7
75
TYP
MAX
5.5
90
110
125
10
60
1
µA
µA
µA
V
mA
A
A
PK
A
RMS
V
ms
ms
ms
ms
ms
ms
°C
mΩ
UNITS
V
2
_______________________________________________________________________________________
Single USB Switch with Autoreset and
Fault Blanking in Tiny TDFN
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 5V, C
IN
= 0.1µF, C
OUT
= 1µF,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.) (Note1)
PARAMETER
ON, SEL Input High Level
ON, SEL Input Low Level
ON, SEL Input Leakage Current
FAULT
Output Low Voltage
FAULT
Output High Leakage
Current
OUT Output Current Autoreset
Mode
OUT Autoreset Threshold
OUT Autoreset Blanking Time
V
OL
SYMBOL
V
IH
V
IL
CONDITIONS
V
IN
= 2.7V to 4V
V
IN
= 4V to 5.5V
V
IN
= 2.7V to 4V
V
IN
= 4V to 5.5V
V
ON
, V
SEL
= 0 or V
IN
, T
A
= +25°C
I
SINK
= 1mA, V
IN
= 2.7V
V
IN
= V
FAULT
= 5.5V
In latched off state, V
OUT
= 0
In latched off state, V
OUT
rising
In latched off state, V
OUT
> 0.5V
10
0.4
10
1
25
0.5
20
45
0.6
35
-1
MIN
1.6
2
0.6
0.8
+1
0.5
TYP
MAX
UNITS
V
V
µA
V
µA
mA
V
ms
MAX1946
ELECTRICAL CHARACTERISTICS
(V
IN
= 5V, C
IN
= 0.1µF, C
OUT
= 1µF,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note1)
PARAMETER
Supply Voltage Range
Switch On-Resistance
Standby Supply Current
Quiescent Supply Current
OUT Off-Leakage Current
Undervoltage Lockout Threshold
Continuous Load Current
Continuous Current Limit
Short-Circuit Current Limit
Continuous Current-Limit
Blanking Timeout Period
Short-Circuit Blanking Timeout
Period
Turn-On Delay
t
ON
I
LIM
I
SC
V
IN_
- V
OUT
= 0.5V
V
OUT
= 0 (I
OUT
pulsing)
From continuous current-limit condition to
FAULT
asserted
From short-circuit current-limit condition to
FAULT
asserted
R
OUT
= 10Ω. Time from ON to 10% of V
OUT
.
Does not include rise time.
I
IN
I
LKG
V
ULVO
SYMBOL
V
IN
V
IN
= 5, T
A
= +25°C
R
ON
V
IN
= 5V
V
IN
= 3.3V
Switch disabled
Switch enabled, I
OUT
= 0
Switch disabled, V
OUT
= 0, T
A
= -40°C to +25°C
Rising edge, 3% hysteresis
2.3
500
0.6
0.8
10
7.5
0.25
1.3
1.6
35
35.0
1.50
CONDITIONS
MIN
2.7
TYP
MAX
5.5
90
110
125
10
60
1
2.7
µA
µA
µA
V
mA
A
A
PK
ms
ms
ms
mΩ
UNITS
V
_______________________________________________________________________________________
3
Single USB Switch with Autoreset and
Fault Blanking in Tiny TDFN
MAX1946
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 5V, C
IN
= 0.1µF, C
OUT
= 1µF,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note1)
PARAMETER
Turn-Off Delay
ON, SEL Input High Level
ON, SEL Input Low Level
ON, SEL Input Leakage Current
FAULT
Output Low Voltage
OUT Output Current Autoreset
Mode
OUT Autoreset Threshold
OUT Autoreset Blanking Time
V
OL
SYMBOL
t
OFF
V
IH
V
IL
CONDITIONS
R
OUT
= 10Ω, time from ON to 90% of V
OUT
,
does not include fall time
V
IN
= 2.7V to 4V
V
IN
= 4V to 5.5V
V
IN
= 2.7V to 4V
V
IN
= 4V to 5.5V
V
ON
, V
SEL
= 0 or V
IN
I
SINK
= 1mA, V
IN
= 2.7V
In latched off state, V
OUT
= 0
In latched off state, V
OUT
rising
In latched off state, V
OUT
> 0.5V
10
0.4
10
-1
1.6
2
0.6
0.8
+1
0.5
45
0.6
35
MIN
TYP
MAX
2
UNITS
ms
V
V
V
V
µA
V
mA
V
ms
Note 1:
All parts are 100% tested at T
A
= +25°C. Limits over the operating temperature range are guaranteed by design.
Note 2:
Short-circuit detect threshold is the output voltage at which the device transitions from short-circuit current limit to continuous
current limit.
Typical Operating Characteristics
(Circuit of Figure 2, V
IN
= 5V, C
IN
= 0.1µF, C
OUT
= 1µF, ON = SEL, T
A
= +25°C, unless otherwise noted.)
QUIESCENT SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1946 toc01
QUIESCENT SUPPLY CURRENT
vs. TEMPERATURE
V
SEL
= V
ON
= GND
QUIESCENT SUPPLY CURRENT (µA)
42
V
IN
= 5.5V
39
V
IN
= 5V
MAX1946 toc02
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
SHUTDOWN SUPPLY CURRENT (µA)
3.3
3.2
3.1
3.0
2.9
2.8
2.7
2.6
-40
-15
10
35
60
85
ON = GND, V
SEL
= 5V
MAX1946 toc03
50
QUIESCENT SUPPLY CURRENT (µA)
V
SEL
= V
ON
= GND
45
3.4
40
30
20
36
10
33
V
IN
= 2.7V
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5
INPUT VOLTAGE (V)
30
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
4
_______________________________________________________________________________________
Single USB Switch with Autoreset and
Fault Blanking in Tiny TDFN
Typical Operating Characteristics (continued)
(Circuit of Figure 2, V
IN
= 5V, C
IN
= 0.1µF, C
OUT
= 1µF, ON = SEL, T
A
= +25°C, unless otherwise noted.)
SWITCH OFF-LEAKAGE
vs. TEMPERATURE
ON = OUT = GND, V
SEL
= 5V
SWITCH OFF-LEAKAGE (nA)
100
MAX1946 toc04
MAX1946
NORMALIZED ON-RESISTANCE
vs. TEMPERATURE
MAX1946 toc05
CONTINUOUS CURRENT-LIMIT
THRESHOLD vs. TEMPERATURE
CONTINUOUS CURRENT THRESHOLD (mA)
MAX1946 toc06
1000
1.3
1.2
NORMALIZED R
ON
1.1
1.0
0.9
0.8
0.7
1090
1080
1070
1060
1050
V
IN
= 2.7V
1040
1030
V
IN
= 5.5V
V
IN
= 5.0V
10
1
0.1
0.01
-40
-15
10
35
60
85
TEMPERATURE (°C)
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
TURN-ON TIME
vs. TEMPERATURE (t
ON
+ t
RISE
)
MAX1946 toc07
TURN-OFF TIME vs. TEMPERATURE
(t
OFF
+ t
FALL
)
R
OUT
= 10Ω
3.5
TURN-OFF TIME (ms)
3.2
2.9
2.6
2.3
2.0
V
IN
= 5V
V
IN
= 5.5V
MAX1946 toc08
FAULT-BLANKING TIME
vs. TEMPERATURE
20.8
FAULT-BLANKING TIME (ms)
20.6
20.4
20.2
20.0
19.8
19.6
19.4
19.2
V
IN
= 5.5V
V
IN
= 5V
V
IN
= 2.7V
MAX1946 toc09
4.0
3.5
TURN-ON TIME (ms)
3.0
R
OUT
= 10Ω
3.8
21.0
V
IN
= 2.7V
2.5
2.0
1.5
1.0
-40
-15
10
35
60
85
TEMPERATURE (°C)
V
IN
= 5V
V
IN
= 5.5V
V
IN
= 2.7V
19.0
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
FAULT OUTPUT LOW VOLTAGE
vs. TEMPERATURE
MAX1946 toc10
AUTORESET CURRENT
vs. TEMPERATURE
MAX1946 toc11
AUTORESET CURRENT
vs. INPUT VOLTAGE
MAX1946 toc12
345
FAULT OUTPUT LOW VOLTAGE (mV)
325
305
285
265
245
225
205
185
165
145
-40
I
SINK
= 1mA
40
35
AUTORESET CURRENT (mA)
30
25
20
15
10
5
V
IN
= 2.7V
V
IN
= 5V
V
IN
= 5.5V
35
31
AUTORESET CURRENT (mA)
27
23
19
15
11
7
T
A
= +85°C
T
A
= -40°C
V
IN
= 2.7V
T
A
= +25°C
V
IN
= 5V
V
IN
= 5.5V
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
3.5 3.7 3.9 4.1 4.3 4.5 4.7 4.9 5.1 5.3 5.5
INPUT VOLTAGE (V)
_______________________________________________________________________________________
5
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