19-2033; Rev 1; 2/10
Dual USB Switch with Fault Blanking
and Autoreset
General Description
The MAX1838 is a dual, current-limited USB switch with
auxiliary input supply. Each switch meets all IEC speci-
fications for USB ports and is guaranteed to supply
500mA from either of two input supplies. A control pin
selects the power source from either the main or auxil-
iary supply.
The MAX1838 has multiple protection features, includ-
ing independent thermal-shutdown on each channel to
limit junction temperature in case of a prolonged short
or overload condition. The device has accurate internal
current-limit and reverse-current protection to safe-
guard the input supply against overload. When pow-
ered from the auxiliary supply, the current limit on each
channel is set independently with an external resistor.
An autoreset feature latches the switch off if the output
is shorted, thereby saving system power. When the
short is removed, the switch automatically turns back
on. Independent fault signals (FAULTA and
FAULTB)
notify the microprocessor (µP) that the internal current
limit has been reached. A 20ms fault-blanking feature
prevents the MAX1838 from issuing false alarms to the
host during power-up or when hot-swapping into a
capacitive load.
The MAX1838 is available in a space-saving 16-pin
QSOP. For other USB current-limited switches, refer to
the MAX1693, MAX1694, MAX1812, and MAX1823.
o
Autoreset from Fault Condition
o
Guaranteed 500mA Load per Channel
o
Programmable Current Limits on Auxiliary Inputs
o
Reverse Current Protection
o
Thermal Overload Protection
o
Built-In 20ms Fault-Blanking
o
4V to 5.5V Range
o
Independent FAULT Indicator Outputs
Features
o
Dual USB Switch with Auxiliary Input
MAX1838
Ordering Information
PART
MAX1838EEE
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
16 QSOP
Applications
Desktops
Notebook Computers
USB Ports
Docking Stations
Typical Operating Circuit
Pin Configuration
TOP VIEW
GND 1
SEL 2
AUXA 3
INA 4
INB 5
AUXB 6
ON 7
GND 8
16 FAULTA
AUX
AUXA
AUXB
FAULTB
FAULTA
IN
15 ADJA
14 OUTA2
INA
INB
MAX1838
OUTB
10µF
OUTB
MAX1838
13 OUTA1
12 OUTB2
11 OUTB1
10 ADJB
9
FAULTB
OUTA
SEL
ON
GND
OUTA
ADJB
ADJA
QSOP
________________________________________________________________
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.
Dual USB Switch with Fault Blanking
and Autoreset
MAX1838
ABSOLUTE MAXIMUM RATINGS
IN_, AUX_,
ON,
OUT_, SEL,
FAULT_,
ADJ_ to GND .........................................................-0.3V to +6V
IN_, AUX_ to OUTA_; IN_, AUX_ to OUTB_.................-6V to +6V
AUX_ to IN_ .................................................................-6V to +6V
Maximum Continuous Switch Current
(per channel, internally limited).............................................1.2A
FAULT_
Current ..................................................................20mA
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)..........667mW
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__
= V
AUX__
= 5V,
ON
= SEL = GND, ADJ_ = open,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
=
+25°C.)
PARAMETER
Supply Voltage Range
Switch On-Resistance
AUX_ Standby Supply Current
IN_ Standby Supply Current
AUX_ Quiescent Supply Current
IN_ Quiescent Supply Current
OUT_ Off-Leakage Current
Reverse Leakage Current
Undervoltage Lockout Threshold
Continuous Load Current
V
IN
_ - V
OUT
_ = 0.5V, SEL = AUX_
Current-Limit Threshold
I
LIM
V
AUX
_ - V
OUT
_ = 0.5V, SEL = GND
R
ADJ
_ = 67kΩ
SEL = GND,
V
OUT
_ = 0V
(I
OUT
_ pulsing)
R
ADJ
_ = 67kΩ
0.09
0.6
1.2
0.35
10
7.5
20
18
35
35
1.8
A
RMS
A
PEAK
A
RMS
ms
ms
V
UVLO
SYMBOL
V
IN_
V
AUX_
R
ON
V
IN
_ = 5V, each switch
V
IN
_ = 4V, each switch
V
ON
= V
AUX
_
V
ON
= V
IN
_
V
ON
= 0V, I
OUT
_ = 0A
V
ON
= 0V, I
OUT
_ = 0A, SEL = AUX_
V
ON
= V
IN
_, V
OUTA
_ = V
OUTB
_ = 0V
V
OUT
= 5.5V, V
IN
_ = V
AUX
_ = 0V
V
IN
_ or V
AUX
_ rising edge, 3% hysteresis
3.0
500
0.6
0.6
0.09
0.9
0.9
0.225
0.3
1.2
1.2
0.36
0.48
A
PEAK
A
CONDITIONS
MIN
4.0
4.0
95
100
7
1
66
23
0.02
0.02
3.5
16
3
350
300
10
10
3.8
TYP
MAX
5.5
5.5
170
UNITS
V
mΩ
µA
µA
µA
µA
µA
µA
V
mA
Short-Circuit Current Limit
I
SHORT
SEL = AUX_, V
OUT
_ = 0V
Continuous Current-Limit
Blanking Timeout Period
Short-Circuit Blanking Timeout
Period
From continuous current-limit condition to
FAULT_
assertion
From short-circuit current-limit condition to
FAULT_
assertion
2
_______________________________________________________________________________________
Dual USB Switch with Fault Blanking
and Autoreset
ELECTRICAL CHARACTERISTICS (continued)
(V
IN__
= V
AUX__
= 5V,
ON
= SEL = GND, ADJ_ = open,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
=
+25°C.)
PARAMETER
Turn-On Delay
SYMBOL
CONDITIONS
R
OUT_
= 10Ω, does not include rise time
(from
ON
asserted to V
OUT
_ = 10% of
V
IN
_), C
OUT
_ = 1µF
R
OUT
_ = 10Ω, from 10% to 90% of V
OUT_
,
C
OUT
_ = 1µF
R
OUT
_ = 10Ω, does not include fall time
(from
ON
asserted to V
OUT_
= 90% of
V
IN
_), C
OUT
_ = 1µF
R
OUT
_ = 10Ω, from 90% to 10% of V
OUT
_,
C
OUT
_ = 1µF
10°C hysteresis
V
IN
_ = 4V to 5.5V
V
IN
_ = 4V to 5.5V
V
ON
= 0V or 5.5V
V
IN
_ = 4V, sinking 1mA
V
IN
_ = V
FAULT_
= 5.5V
In latched-off state, V
OUT
_ = 0V
In latched-off state, V
OUT
_ rising
In latched-off state, V
OUT
_ > 1V
Make-before-break (Note 1)
10
0.4
10
4.5
25
0.5
20
9
-1
2
0.8
1
0.4
1
50
0.6
35
18
MIN
0.5
TYP
2
MAX
4.0
UNITS
ms
MAX1838
Output Rise Time
4.5
ms
Turn-Off Delay from ON
0.8
3
ms
Output Fall Time
Thermal Shutdown Threshold
Logic Input High Voltage
Logic Input Low Voltage
Logic Input Current
FAULT_
Output Low Voltage
FAULT_
Output High Leakage
Current
Autoreset Current
Autoreset Threshold
Autoreset Blanking Time
AUX_ to IN_ or IN_ to AUX_
Select Delay
3
160
ms
°C
V
V
µA
V
µA
mA
V
ms
ms
ELECTRICAL CHARACTERISTICS
(V
IN__
= V
AUX__
= V
ON
= 5V, SEL = GND, ADJ_ = open,
T
A
= -40°C to +85°C,
unless otherwise noted. Circuit of Figure 1.) (Note 2)
PARAMETER
Supply Voltage Range
Switch On-Resistance
AUX_ Standby Supply Current
IN_ Standby Supply Current
AUX_ Quiescent Supply Current
IN_ Quiescent Supply Current
OUT_ Off-Leakage Current
Reverse Leakage Current
Undervoltage Lockout Threshold
Continuous Load Current
V
UVLO
SYMBOL
V
IN
_
V
AUX
_
R
ON
V
IN
_ = 5V, each switch
V
ON
= V
AUX
_
V
ON
= V
IN
_
V
ON
= 0V, I
OUT
_ = 0A
V
ON
= 0V, I
OUT
= 0A, SEL = AUX_
V
ON
= V
IN
_
,
V
OUTA
_ = V
OUTB
_ = 0V
V
OUT
_ = 5.5V, V
IN
_ = V
AUX
_ = 0V
V
IN
_ or V
AUX
_ rising edge, 3% hysteresis
3.0
500
CONDITIONS
MIN
4.0
4.0
MAX
5.5
5.5
170
16
3
350
300
10
10
3.8
UNITS
V
V
mΩ
µA
µA
µA
µA
µA
µA
V
mA
_______________________________________________________________________________________
3
Dual USB Switch with Fault Blanking
and Autoreset
MAX1838
ELECTRICAL CHARACTERISTICS (continued)
(V
IN__
= V
AUX__
= V
ON
= 5V, SEL = GND, ADJ_ = open,
T
A
= -40°C to +85°C,
unless otherwise noted. Circuit of Figure 1.) (Note 2)
PARAMETER
Current-Limit Threshold
SYMBOL
I
LIM
CONDITIONS
V
IN
_ – V
OUT
_ = 0.5V, SEL = AUX_
V
AUX
_ – V
OUT
_ = 0.5V, SEL = GND
SEL = GND, V
OUT
_ = 0V (I
OUT
_ pulsing)
SEL = AUX_, V
OUT
_ = 0V
Continuous Current-Limit
Blanking Timeout Period
Short-Circuit Blanking Timeout
Period
Turn-On Delay
From continuous current-limit condition to
FAULT_
assertion
From short-circuit current-limit condition to
FAULT_
assertion
R
OUT
_ = 10Ω, does not include rise time
(from
ON
asserted to V
OUT
_ = 10% of
V
IN
_), C
OUT
_ = 1µF
R
OUT
_ = 10Ω, does not include fall time
(from
ON
asserted to V
OUT
_ = 90% of
V
IN
_), C
OUT
_ = 1µF
V
IN
_ = 4V to 5.5V
V
IN
_ = 4V to 5.5V
V
ON
= 0V or 5.5V
V
IN
_ = 4V, sinking 1mA
V
IN
_ = V
FAULT_
= 5.5V
In latched-off state, V
OUT
_ = 0V
In latched-off state, V
OUT
_ rising
In latched-off state, V
OUT
_ > 1 V
Make-before-break (Note 1)
10
0.4
9
4.5
-1
2
0.8
1
0.4
1
55
0.6
40
18
MIN
0.6
0.6
0.6
0.6
9
7
MAX
1.2
1.2
1.8
1.8
40
40
ms
ms
UNITS
A
Short-Circuit Current Limit
I
SHORT
A
PEAK
0.5
4
ms
Turn-Off Delay from ON
3
ms
V
V
µA
V
µA
mA
V
ms
ms
Logic Input High Voltage
Logic Input Low Voltage
Logic Input Current
FAULT_
Output Low Voltage
FAULT_
Output High Leakage
Current
Autoreset Current
Autoreset Threshold
Autoreset Blanking Time
AUX_ to IN_ or IN_ to AUX_
Select Delay
Note 1:
SEL delay includes both make and break delay. The host system should wait for at least this interval before turning off the
appropriate input supply.
Note 2:
Specifications from 0°C to -40°C are guaranteed by design, not production tested.
4
_______________________________________________________________________________________
Dual USB Switch with Fault Blanking
and Autoreset
Typical Operating Characteristics
(Circuit of Figure 2, V
IN_
= 5V, T
A
= +25°C, unless otherwise noted.)
IN + AUX QUIESCENT CURRENT
vs. TEMPERATURE
MAX1838 toc02
MAX1838 toc03
MAX1838
AUX QUIESCENT CURRENT vs. V
AUX
V
IN
= 5V
V
IN
= 4.5V
SEL = GND
V
IN
= 0
V
IN
= 5.5V
MAX1838 toc01
IN QUIESCENT CURRENT vs. V
AUX
30
25
20
15
10
5
0
70
0
1
2
3
V
AUX
(V)
4
5
-40
V
IN
= 4.5V
SEL = AUX
V
IN
= 5V
V
IN
= 5.5V
100
70
AUX QUIESCENT CURRENT (µA)
60
50
40
30
20
10
0
0
1
2
3
V
AUX
(V)
4
5
IN QUIESCENT CURRENT (µA)
SEL = AUX = IN
QUIESCENT CURRENT (µA)
90
V
AUX
= 5.5V
80
V
AUX
= 5V
V
AUX
= 4.5V
-20
0
20
40
60
80
TEMPERATURE (°C)
IN + AUX QUIESCENT CURRENT
vs. TEMPERATURE
MAX1838 toc04
IN + AUX QUIESCENT SHUTDOWN CURRENT
vs. TEMPERATURE
9.5
SHUTDOWN CURRENT (µA)
9.0
8.5
8.0
7.5
7.0
6.5
6.0
80
-40
V
IN
= V
AUX
= 5.5V
1
-20
0
20
40
60
80
-40
V
IN
= V
AUX
= 4.5V
V
IN
= V
AUX
= 5.0V
MAX1838 toc05
SWITCH LEAKAGE CURRENT
vs. TEMPERATURE, FULL DATA
MAX1838 toc06
110
SEL = GND
QUIESCENT CURRENT (µA)
100
V
IN
= V
AUX
= 5.5V
90
V
IN
= V
AUX
= 5V
80
V
IN
= V
AUX
= 4.5V
70
-40
-20
0
20
40
60
TEMPERATURE (°C)
10.0
1000
SWITCH LEAKAGE CURRENT (nA)
100
IN = AUX = SEL = ON = GND
V
OUT_
= 5.5V
10
V
IN
= V
AUX
= V
ON
= V
SEL
= 5.5V
OUT_ = GND
-20
0
20
40
60
80
TEMPERATURE (°C)
TEMPERATURE (°C)
NORMALIZED SWITCH ON-RESISTANCE
vs. TEMPERATURE
MAX1838 toc07
CONTINUOUS CURRENT LIMIT THRESHOLD
vs. TEMPERATURE
MAX1838 toc08
TURN-ON DELAY vs. TEMPERATURE
SEL = GND
2.2
TURN-ON DELAY (ms)
MAX1838 toc09
1.2
1.1
I
OUT_
= 500mA
1.0
0.9
0.8
0.7
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
CONTINUOUS CURRENT LIMIT THRESHOLD (A)
1.3
NORMALIZED ON-RESISTANCE (Ω)
0.94
2.3
0.92
2.1
V
IN
= V
AUX
= 5.0V
V
IN
= V
AUX
= 4.5V
0.90
2.0
0.88
1.9
V
IN
= V
AUX
= 5.5V
0.86
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
1.8
-40
-20
0
20
40
60
80
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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