MAXIM MAX1838 User Manual

General Description

The MAX1838 is a dual, current-limited USB switch with
auxiliary input supply. Each switch meets all IEC speci­fications 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 auxil­iary supply.

The MAX1838 has multiple protection features, includ­ing 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 safe­guard the input supply against overload. When pow­ered 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.

Applications

Desktops

Notebook Computers

USB Ports

Docking Stations

Features

o Dual USB Switch with Auxiliary Input

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

MAX1838

Dual USB Switch with Fault Blanking

and Autoreset

________________________________________________________________

Maxim Integrated Products

1

Pin Configuration

Ordering Information

19-2033; Rev 1; 2/10

Typical Operating Circuit

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.

PART TEMP RANGE PIN-PACKAGE

MAX1838EEE -40°C to +85°C 16 QSOP

TOP VIEW

1

GND FAULTA

SEL

2

AUXA

3

4

INA

INB

5

AUXB

6

ON

7

GND

8

16

15

ADJA

14

OUTA2

MAX1838

QSOP

13

12

11

10

9

OUTA1

OUTB2

OUTB1

ADJB

FAULTB

AUX

IN

AUXA
AUXB

INA
INB

SEL

ON

GND

MAX1838

FAULTB

FAULTA

OUTB

OUTA

ADJB

ADJA

OUTB

10µF

OUTA

MAX1838

Dual USB Switch with Fault Blanking
and Autoreset

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

IN__

= V

AUX__

= 5V, ON = SEL = GND, ADJ_ = open, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA=

+25°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.

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

Supply Voltage Range

Switch On-Resistance R

AUX_ Standby Supply Current V ON = V

IN_ Standby Supply Current V ON = VIN_13µA

AUX_ Quiescent Supply Current V ON = 0V, I

IN_ Quiescent Supply Current V ON = 0V, I

OUT_ Off-Leakage Current V ON = VIN_, V

Reverse Leakage Current V

Undervoltage Lockout Threshold V

Continuous Load Current 500 mA

Current-Limit Threshold I

Short-Circuit Current Limit I

Continuous Current-Limit
Blanking Timeout Period

Short-Circuit Blanking Timeout
Period

PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS

V

IN_

V

AUX_

ON

UVLO

LIM

SHORT

VIN_ = 5V, each switch 95 170

VIN_ = 4V, each switch 100

AUX

= 5.5V, VIN_ = V

OUT

VIN_ or V

VIN_ - V

V

R

SEL = GND,
V
(I

SEL = AUX_, V

From continuous current-limit condition to
FAULT_ assertion

From short-circuit current-limit condition to
FAULT_ assertion

AUX

OUT

_ - V

AUX

ADJ

OUT

OUT

OUT

_ = 67kΩ 0.09 0.225 0.36

_ = 0V
_ pulsing)

4.0 5.5

4.0 5.5

_ 7 16 µA

_ = 0A 66 350 µA

OUT

_ = 0A, SEL = AUX_ 23 300 µA

OUT

_ = V

OUTA

_ rising edge, 3% hysteresis 3.0 3.5 3.8 V

_ = 0.5V, SEL = AUX_ 0.6 0.9 1.2

_ = 0.5V, SEL = GND 0.6 0.9 1.2

_ = 0V

OUT

_ = 0V 0.02 10 µA

OUTB

_ = 0V 0.02 10 µA

AUX

0.3 0.48 A

R

_ = 67kΩ

ADJ

0.6 1.2 1.8 A

10 20 35 ms

7.5 18 35 ms

0.09 A

0.35 A

V

mΩ

A

PEAK

RMS

PEAK

RMS

MAX1838

Dual USB Switch with Fault Blanking

and Autoreset

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(V

IN__

= V

AUX__

= 5V, ON = SEL = GND, ADJ_ = open, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA=

+25°C.)

ELECTRICAL CHARACTERISTICS

(V

IN__

= V

AUX__

= VON= 5V, SEL = GND, ADJ_ = open, TA= -40°C to +85°C, unless otherwise noted. Circuit of Figure 1.) (Note 2)

Turn-On Delay

Output Rise Time

Turn-Off Delay from ON

Output Fall Time

Thermal Shutdown Threshold 10°C hysteresis 160 °C

Logic Input High Voltage VIN_ = 4V to 5.5V 2 V

Logic Input Low Voltage VIN_ = 4V to 5.5V 0.8 V

Logic Input Current V ON = 0V or 5.5V -1 1 µA

FAULT_ Output Low Voltage VIN_ = 4V, sinking 1mA 0.4 V
FAULT_ Output High Leakage

Current

Autoreset Current In latched-off state, V

Autoreset Threshold In latched-off state, V

Autoreset Blanking Time In latched-off state, V

AUX_ to IN_ or IN_ to AUX_
Select Delay

PARAMETER SYM BOL CONDITIONS MIN TYP MAX UNITS

= 10Ω, does not include rise time

R

OUT_

(from ON asserted to V
V

R
C

R

IN

OUT

OUT

OUT

_), C

_ = 1µF

OUT

_ = 10Ω, from 10% to 90% of V
_ = 1µF

_ = 10Ω, does not include fall time

(from ON asserted to V
V

R
C

V

IN

OUT

OUT

IN

_), C

_ = V

_ = 1µF

OUT

_ = 10Ω, from 90% to 10% of V
_ = 1µF

FAULT_

OUT

OUT_

= 5.5V 1 µA

_ = 0V 10 25 50 mA

OUT

_ rising 0.4 0.5 0.6 V

OUT

_ > 1V 10 20 35 ms

OUT

_ = 10% of

OUT_

= 90% of

OUT

0.5 2 4.0 ms

,

4.5 ms

0.8 3 ms

_,

3ms

Make-before-break (Note 1) 4.5 9 18 ms

Supply Voltage Range

Switch On-Resistance R

AUX_ Standby Supply Current V

IN_ Standby Supply Current V

AUX_ Quiescent Supply Current V

IN_ Quiescent Supply Current V

OUT_ Off-Leakage Current V

Reverse Leakage Current V

Undervoltage Lockout Threshold V

Continuous Load Current 500 mA

PARAMETER SYM BO L CONDITIONS MIN MAX UNITS

VIN_ 4.0 5.5 V

_ 4.0 5.5 V

V

AUX

VIN_ = 5V, each switch 170 mΩ

ON

UVLOVIN

= V

ON

= VIN_3µA

ON

= 0V, I

ON

= 0V, I

ON

= VIN_, V

ON

OUT

_ or V

_16µA

AUX

= 0A 350 µA

OUT_

= 0A, SEL = AUX_ 300 µA

OUT

_ = V

OUTA

_ = 5.5V, VIN_ = V

_ rising edge, 3% hysteresis 3.0 3.8 V

AUX

_ = 0V 10 µA

OUTB

_ = 0V 10 µA

AUX

MAX1838

Dual USB Switch with Fault Blanking
and Autoreset

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(V

IN__

= V

AUX__

= VON= 5V, SEL = GND, ADJ_ = open, TA= -40°C to +85°C, unless otherwise noted. Circuit of Figure 1.) (Note 2)

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.

Current-Limit Threshold I

Short-Circuit Current Limit I

Continuous Current-Limit
Blanking Timeout Period

Short-Circuit Blanking Timeout
Period

Turn-On Delay

Turn-Off Delay from ON

Logic Input High Voltage VIN_ = 4V to 5.5V 2 V

Logic Input Low Voltage VIN_ = 4V to 5.5V 0.8 V

Logic Input Current V ON = 0V or 5.5V -1 1 µA

FAULT_ Output Low Voltage VIN_ = 4V, sinking 1mA 0.4 V
FAULT_ Output High Leakage

Current

Autoreset Current In latched-off state, V

Autoreset Threshold In latched-off state, V

Autoreset Blanking Time In latched-off state, V

AUX_ to IN_ or IN_ to AUX_
Select Delay

PARAMETER SYM BO L CONDITIONS MIN MAX UNITS

LIM

SHORT

VIN_ – V

V

AUX

SEL = GND, V

SEL = AUX_, V

From continuous current-limit condition to
FAULT_ assertion

From short-circuit current-limit condition to
FAULT_ assertion

R

OUT

(from ON asserted to V

_), C

V

IN

R

OUT

(from ON asserted to V
V

_), C

IN

V

_ = V

IN

Make-before-break (Note 1) 4.5 18 ms

_ = 0.5V, SEL = AUX_ 0.6 1.2

OUT

_ – V

_ = 0.5V, SEL = GND 0.6 1.2

OUT

_ = 0V (I

OUT

_ = 0V 0.6 1.8

OUT

_ = 10Ω, does not include rise time

_ = 1µF

OUT

_ = 10Ω, does not include fall time

_ = 1µF

OUT

= 5.5V 1 µA

FAULT_

OUT

OUT

OUT

_ pulsing) 0.6 1.8

OUT

940ms

740ms

_ = 10% of

OUT

_ = 90% of

OUT

_ = 0V 10 55 mA

_ rising 0.4 0.6 V

_ > 1 V 9 40 ms

0.5 4 ms

A

A

PEAK

3ms