MAXIM MAX1940 User Manual

General Description

The MAX1940 triple current-limited switch with auto­reset supplies a guaranteed 500mA load per channel in
accordance with USB specifications. The MAX1940
operates from a 4V to 5.5V input supply and consumes
only 60µA of quiescent current when operating and only
3µA in standby. Selectable active-high/active-low con­trol logic and independent shutdown controls for each
channel provide additional flexibility. An autoreset fea­ture latches the switch off in the event of a short circuit,
saving system power. The switch reactivates upon
removal of the shorted condition.

The MAX1940 provides several safety features to pro­tect the USB port. Built-in thermal-overload protection
turns off the switch when the die temperature exceeds
+160°C. Accurate internal current-limiting circuitry pro­tects the input supply against both overload and short­circuit conditions. Independent open-drain fault signals
(FAULTA, FAULTB, and FAULTC) notify the micro-
processor when a thermal-overload, 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
also prevents fault signals from being issued when the
device powers up the load.

The MAX1940 is available in a space-saving 16-pin
QSOP package and operates over the extended (-40°C
to +85°C) temperature range.

Applications

Features

o Triple USB Switch in Tiny 16-Pin QSOP Package

o Autoreset Feature Saves System Power

o Guaranteed 500mA Load Current per Channel

o Built-In 20ms Fault-Blanking Circuitry

o Active-High/Active-Low Control Logic

o Fully Compliant to USB Specifications

o 4V to 5.5V Input Voltage Range

o Independent Shutdown Control

o Independent Fault Indicator Outputs

o Thermal-Overload Protection

o 3µA Standby Current

MAX1940

Triple USB Switch with Autoreset and

Fault Blanking

________________________________________________________________

Maxim Integrated Products

1

Typical Operating Circuit

Ordering Information

19-2497; Rev 1; 2/10

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.

Pin Configuration

USB Ports

USB Hubs

Notebook Computers

Desktop Computers

PDAs and Palmtop
Computers

Docking Stations

PART TEMP RANGE PIN-PACKAGE

MAX1940EEE -40°C to +85°C 16 QSOP

TOP VIEW

ONA

1

IN1

2

IN2

3

4

IN3

ONB

5

IN4

6

IN5

7

ONC

8

16

FAULTA

15

OUTA

14

GND

MAX1940

QSOP

13

12

11

10

9

OUTB

FAULTB

SEL

OUTC

FAULTC

INPUT

4V TO 5.5V

ACTIVE-HIGH/ACTIVE-LOW

SELECTABLE

MAX1940

IN1

IN2

IN3

IN4

IN5

ONA

ONB

ONC

SEL

FAULTA

FAULTB

FAULTC

OUTA

OUTB

OUTC

GND

USB
PORT A

USB
PORT B

USB
PORT C

MAX1940

Triple USB Switch with Autoreset and
Fault Blanking

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_, ON_, OUT_, SEL, FAULT_, to GND...................-0.3V to +6V

IN1, IN2 to OUTA......................................................-0.3V to +6V

IN2, IN3 to OUTB......................................................-0.3V to +6V

IN4, IN5 to OUTC .....................................................-0.3V to +6V

OUT_ Continuous Switch Current

(per channel, internally limited).........................................1.4A

FAULT_ DC 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

ELECTRICAL CHARACTERISTICS

(V

IN_

= 5V, C

IN_

= 0.1µF, C

OUT_

= 1µF, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

Supply Voltage Range V

Switch On-Resistance R

Standby Supply Current All switches disabled 3 10 µA

OUT_ Off-Leakage Current I

Undervoltage Lockout Threshold V

Continuous Load Current 500 mA

Continuous Current Limit I

Short-Circuit Current Limit I

Short-Circuit Detect Threshold (Note 1) 1 V

Continuous Current-Limit
Blanking Timeout Period

Short-Circuit Blanking Timeout
Period

Turn-On Delay t

Output Rise Time t

Turn-Off Delay t

Output Fall Time t

Thermal-Shutdown Threshold 15°C hysteresis 160 °C

ON_, SEL Input High Level V

ON_, SEL Input Low Level V

ON_, SEL Input Leakage Current V

PARAMETER SYM B O L CONDITIONS MIN TYP MAX UNITS

IN_

ON

IN_

LKG

ULVO

LIM

SC

TA = 0°C to +85°C, each switch 85 135 mΩ

One switch enabled, I

Two switches enabled, I

All switches enabled, I

All switches disabled, V
T

= 0°C to +85°C

A

= 0 47 75

OUT_

= 0 55 90Quiescent Supply Current I

OUT_

= 0 63 100

OUT_

= 0,

OUT_

Rising edge, 3% hysteresis 3.0 3.4 3.8 V

V

IN_

V

OUT_

- V

= 0.5V 0.7 0.9 1.2 A

OUT_

= 0 (I

OUT_

pulsing)

From continuous current-limit condition to
FAULT_ asserted

From short-circuit current-limit condition to
FAULT_ asserted

R

= 10Ω, does not include rise time

ON

RISE

OFF

FALL

IH

IL

OUT_

(from ON_ to 10% of V

R

= 10Ω, from 10% to 90% of V

OUT_

R

= 10Ω, does not include fall time

OUT_

(from ON_ to 90% of V

R

= 10Ω, from 90% to 10% of V

OUT_

V

= 4V to 5.5V 2 V

IN_

V

= 4V to 5.5V 0.8 V

IN_

= 0 or V

ON_

IN_

OUT_

OUT_

)

OUT_

)

OUT_

4.0 5.5 V

0.02 10 µA

0.9 1.2 1.6 A

0.35 A

10 20 35 ms

7.5 18 35.0 ms

0.5 1.2 4.0 ms

2.5 ms

0.8 3 ms

2.5 ms

-1 +1 µA

µA

PK

RMS

MAX1940

Triple USB Switch with Autoreset and

Fault Blanking

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(V

IN_

= 5V, C

IN_

= 0.1µF, C

OUT_

= 1µF, TA= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

ELECTRICAL CHARACTERISTICS

(V

IN_

= 5V, C

IN_

= 0.1µF, C

OUT_

= 1µF, TA= -40°C to +85°C, unless otherwise noted.) (Note 2)

Note 1: Short-circuit detect threshold is the output voltage at which the device transitions from short-circuit current limit to

continuous current limit.

Note 2: Specifications to -40°C are guaranteed by design, not production tested.

FAULT_ Output Low Voltage V
FAULT_ Output High Leakage

Current

OUT_ Autoreset Current In latched off state, V

PARAMETER SYM B O L CONDITIONS MIN TYP MAX UNITS

I

OL

SINK

V

IN_

= 1mA, V

= V

FAULT_

= 4V 0.4 V

IN_

= 5.5V 1 µA

= 0 102545mA

OUT_

OUT_ Autoreset Threshold In latched off state, OUT_ rising 0.4 0.5 0.6 V

OUT_ Autoreset Blanking Time In latched off state, V

> 0.5V 10 20 35 ms

OUT_

Supply Voltage Range V

Switch On-Resistance R

Standby Supply Current All switches disabled 10 µA

OUT_ Off-Leakage Current I

Undervoltage Lockout Threshold V

Continuous Load Current 500 mA

Continuous Current Limit I

Short-Circuit Current Limit I

Continuous Current-Limit
Blanking Timeout Period

Short-Circuit Blanking Timeout
Period

Turn-On Delay t

Turn-Off Delay t

ON_, SEL Input High Level V

ON_, SEL Input Low Level V

ON_, SEL Input Leakage Current V

FAULT_ Output Low Voltage V

FAULT_ Output High Leakage

Current

OUT_ Autoreset Current In latched off state, V

OUT_ Autoreset Threshold In latched off state, OUT_ rising 0.4 0.6 V

OUT_ Autoreset Blanking Time In latched off state, V

PARAMETER SYM B O L CONDITIONS MIN MAX UNITS

IN_

ON

IN_

LKG

ULVO

LIM

SC

Each switch 135 mΩ

One switch enabled, I

Two switches enabled, I

All switches enabled, I

All switches disabled, V

= 0 75

OUT_

= 0 90Quiescent Supply Current I

OUT_

= 0 100

OUT_

= 0 10 µA

OUT_

Rising edge, 3% hysteresis 3.0 3.8 V

V

IN_

V

OUT_

- V

= 0.5V 0.7 1.2 A

OUT_

= 0 (I

pulsing) 0.9 1.6 A

OUT_

From continuous current-limit condition to
FAULT_ asserted

From short-circuit current-limit condition to
FAULT_ asserted

R

= 10Ω, does not include rise time

ON

OFF

IH

IL

OL

OUT_

(from ON_ to 10% of V

R

= 10Ω, does not include fall time

OUT_

(from ON_ to 90% of V

V

= 4V to 5.5V 2 V

IN_

V

= 4V to 5.5V 0.8 V

IN_

= 0 or V

ON_

I

SINK

V

IN_

= 1mA, V

= V

IN_

= 4V 0.4 V

IN_

= 5.5V 1 µA

FAULT_

)

OUT_

)

OUT_

= 0 10 50 mA

OUT_

> 0.5V 10 35 ms

OUT_

4.0 5.5 V

10 35 ms

7.5 35.0 ms

0.5 4.0 ms

3ms

-1 +1 µA

µA

PK

MAX1940

Triple USB Switch with Autoreset and
Fault Blanking

4 _______________________________________________________________________________________

Typical Operating Characteristics

(Circuit of Figure 2, V

IN_

= 5V, C

IN_

= 0.1µF, C

OUT_

= 1µF, ON_ = SEL, TA= +25°C, unless otherwise noted.)

QUIESCENT SUPPLY CURRENT

vs. INPUT VOLTAGE

MAX1940 toc01

INPUT VOLTAGE (V)

QUIESCENT SUPPLY CURRENT (µA)

5.04.54.03.53.02.52.01.51.00.5

10

20

30

40

50

60

70

0

05.5

ALL SWITCHES ACTIVE

QUIESCENT SUPPLY CURRENT

vs. TEMPERATURE

MAX1940 toc02

TEMPERATURE (°C)

QUIESCENT SUPPLY CURRENT (µA)

603510-15

61

62

63

64

65

66

67

68

69

70

60

-40 85

ALL SWITCHES ACTIVE

V

IN_

= 5.5V

V

IN_

= 5V

V

IN_

= 4.5V

SHUTDOWN SUPPLY CURRENT

vs. TEMPERATURE

MAX1940 toc03

TEMPERATURE (°C)

SHUTDOWN SUPPLY CURRENT (µA)

603510-15

2.6

2.7

2.8

2.9

3.0

2.5

-40 85

ON_ = GND, V

SEL

= 5V

SWITCH OFF-LEAKAGE (ONE SWITCH)

vs. TEMPERATURE

MAX1940 toc04

TEMPERATURE (°C)

SWITCH OFF-LEAKAGE (nA)

603510-15

0.1

1

10

100

1000

0.01

-40 85

ON_ = OUT_, V

SEL

= 5V

CONTINUOUS CURRENT-LIMIT THRESHOLD

vs. TEMPERATURE

MAX1940 toc06

TEMPERATURE (°C)

CONTINUOUS CURRENT-LIMIT THRESHOLD (mA)

603510-15

904

908

912

916

920

900

-40 85

V

IN_

= 5.0V

V

IN_

= 5.5V

V

IN_

= 4.5V

FAULT-BLANKING TIME

vs. TEMPERATURE

MAX1940 toc09

TEMPERATURE (°C)

FAULT-BLANKING TIME (ms)

603510-15

19.5

20.0

20.5

21.0

21.5

22.0

19.0

-40 85

V

IN_

= 5.5V

V

IN_

= 5V

V

IN_

= 4.5V

NORMALIZED ON-RESISTANCE

1.3

vs. TEMPERATURE

TURN-ON TIME (tON + t

RISE

)

vs. TEMPERATURE

3.5
R

= 10Ω

OUT_

3.4

V

= 5V

IN_

3.3

3.2

TURN-ON TIME (ms)

3.1

3.0

-40 85

V

= 4.5V

IN_

V

IN_

TEMPERATURE (°C)

MAX1940 toc07

= 5.5V

603510-15

1.2

1.1

1.0

0.9

NORMALIZED ON-RESISTANCE

0.8

0.7

-40 85
TEMPERATURE (°C)

TURN-OFF TIME (t

OFF

+ t

vs. TEMPERATURE

3.3
R

= 10Ω

OUT_

3.2

3.1

3.0

2.9

TURN-OFF TIME (ms)

2.8

2.7

2.6

-40 85

V

V

IN_

= 5V

IN_

TEMPERATURE (°C)

= 5.5V

V

603510-15

FALL

IN_

603510-15

MAX1940 toc05

)

MAX1940 toc08

= 4.5V