Rainbow Electronics MAX1558H User Manual

General Description

The MAX1558/MAX1558H are dual, current-limited
switches with autoreset for USB applications. Autoreset
latches the switch off if it is shorted for more than 20ms,
saving system power. The shorted output is then tested
to determine when the short is removed to automatically
restart the channel. Each channel delivers up to 1.2A
and meets all IEC specifications for USB ports. Low
quiescent supply current (45µA) and standby current
(3µA) conserve battery power in portable applications.

The MAX1558/MAX1558H safety features ensure that the
USB port is protected. Built-in thermal-overload protection
limits power dissipation and junction temperature.
Accurate, programmable current-limiting circuitry pro­tects the input supply against both overload and short-cir­cuit conditions. 20ms fault blanking enables the circuit to
ignore transient faults, such as those caused when hot
swapping a capacitive load, preventing false alarms to
the host system. The MAX1558/MAX1558H also feature
reverse-current protection circuitry to block current flow
from the output to the input when the switches are off.

The MAX1558/MAX1558H are available in space-sav­ing 3mm x 3mm, 10-pin TDFN packages. The MAX1558
is enabled with an active-low signal, and the
MAX1558H is enabled with an active-high signal.

Applications

USB Ports and Hubs
Notebook Computers and Desktops
PDAs and Palmtop Computers
Docking Stations

Features

♦ 55mΩ Switch Resistance
♦ Tiny 10-Pin, 3mm x 3mm TDFN Package
♦ 14% Accurate Current Limit
♦ Autorestart when Fault is Removed
♦ Programmable Current Up to 1.2A
♦ Thermal-Overload Protection
♦ Built-In 20ms Fault Blanking
♦ Compliant to All USB Specifications
♦ 2.7V to 5.5V Supply Range
♦ Independent-Output Fault Indicators
♦ Block Reverse Current when Disabled
♦ 15kV ESD Protection (with Capacitor)
♦ UL Listing Pending

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

________________________________________________________________ Maxim Integrated Products 1

Ordering Information

19-3128; Rev 0; 6/04

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

PART

TEMP RANGE

PIN­PACKAGE

TOP

MARK

MAX1558ETB

10 TDFN

AAR

MAX1558HETB

10 TDFN

AAS

MAX1558

INPUT

2.7V TO 5.5V

INA
INB

ISET

FLTA

FLTB

ONA
ONB

ONA
ONB

OUTA

OUTB

GND

USB
PORT A

USB
PORT B

Typical Operating Circuit

2
3

9
8

TDFN

3mm x 3mm

TOP VIEW

4

5

7
6

1

MAX1558

(MAX1558H)

10

ISET

INA

INB

ONA (ONA)

ONB (ONB)

OUTA

GND

OUTB

FLTA

FLTB

Pin Configuration

-40°C to +85°C
(3mm x 3mm)

-40°C to +85°C
(3mm x 3mm)

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current
USB Switches with Autoreset

2 _______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

ELECTRICAL CHARACTERISTICS

(V

INA

= V

INB

= 5V, V

ONA

= V

ONB

= 0V (MAX1558), V

ONA

= V

ONB

= 5V (MAX1558H), R

ISET

= 26kΩ to GND, TA= 0°C to +85°C,

unless otherwise noted. Typical values are at T

A

= +25°C.) (Note 3)

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_, ISET, FLT_ to GND........................-0.3V to +6V

IN_ to OUT_ (when disabled) (Note 1)........................-6V to +6V

IN_ to OUT_ (when enabled) (Note 2)............-1.6A to +1.6A

RMS

FLT_ Sink Current................................................................20mA

Continuous Power Dissipation (T

A

= +70°C)
10-Pin TDFN 3mm x 3mm

(derate 24.4mW/°C above +70°C).............................1952mW

Operating Temperature Range ...........................-40°C to +85°C

Junction Temperature......................................................+160°C

Storage Temperature Range.............................-65°C to +150°C

Lead Temperature (soldering, 10s).................................+300°C

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Supply Voltage Range

V

V

IN_

= 5V, TA = +25°C5575

V

IN_

= 3.3V, TA = +25°C64Switch On-Resistance R

ON

V

IN_

= 4.4V, TA = 0°C to +85°C 105

mΩ

Standby Supply Current Both switches disabled 3 6 µA
Quiescent Supply Current Both switches enabled 45 75 µA

V

OUTA

= V

OUTB

= 0V

10

OUT_ Off-Leakage Current

V

OUTA

= V

OUTB

= 5V

µA

Reverse Leakage Current

V

IN_

= 0V, V

OUTA

= V

OUTB

= 5V, both

switches disabled

µA

V

UVLO

Rising edge, 3% hysteresis 2.3 2.5 2.7 V

Continuous Load Current R

ISET

= 26kΩ 1.2 A

R

ISET

= 26kΩ

1.4

R

ISET

= 39kΩ

Current-Limit Threshold

V

IN_

- V

OUT_

=

0.5V
R

ISET

= 60kΩ

0.6

A

R

ISET

= 26kΩ

2.0

R

ISET

= 39kΩ

Peak Short-Circuit Current Limit I

SHORT

V

OUT_

= 0V

(I

OUT_

pulsing)

R

ISET

= 60kΩ

A

(PEAK)

R

ISET

= 26kΩ

R

ISET

= 39kΩ

RMS Short-Circuit Current Limit I

SHORT

V

OUT_

= 0V

(I

OUT_

pulsing)

R

ISET

= 60kΩ

A

RMS

Short-Circuit Continuous Current­Limit Transition Threshold

(Note 4) 1 V

Fault-Blanking Timeout Period From I

LIMIT

condition to 50% of V

FLT_

82040ms

Turn-On Delay t

ON

R

OUT_

= 10Ω, C

OUT_

= 1µF, does not

include rise time (from ON asserted to
V

OUT_

= 10% V

IN_

)

0.5 1.4 4.0 ms

Note 1: Reverse current (current from OUT_ to IN_) is blocked when disabled.
Note 2: Forward current (current from IN_ to OUT_) is internally limited. Reverse current, from OUT_ to IN_, is not limited when the

device is enabled and must be kept below 1.5A

RMS

to prevent permanent device damage. When the MAX1558/MAX1558H

are disabled, the switch turns off and reverse current is internally blocked.

Undervoltage-Lockout Threshold

Switches disabled

2.75 5.50

0.03

0.03

0.03

1.20

0.80 0.925 1.05

0.50

1.45

1.40

0.90

0.55

0.37

0.23

1.60

0.70

2.60

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(V

INA

= V

INB

= 5V, V

ONA

= V

ONB

= 0V (MAX1558), V

ONA

= V

ONB

= 5V (MAX1558H), R

ISET

= 26kΩ to GND, TA= 0°C to +85°C,

unless otherwise noted. Typical values are at T

A

= +25°C.) (Note 3)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Output Rise Time t

RISE

C

OUT_

= 1µF, R

OUT_

= 10Ω, (from 10% to

90% of V

OUT_

)

4ms

Turn-Off Delay from ON t

OFF

R

OUT_

= 10Ω, C

OUT_

= 1µF, does not

include rise time (from ON deasserted to
V

OUT_

= 90% V

IN_

)

µs

Output Fall Time t

FALL

C

OUT_

= 1µF, R

OUT_

= 10Ω (from 90% to

10% of V

OUT_

)

3ms

Thermal-Shutdown Threshold 10°C hysteresis

°C

V

IN_

= 2.7V to 4.0V 1.6

ONA/ONB Logic Input High
Voltage

V

IH

V

IN_

4.0V to 5.5V 2.0

V

V

IN_

= 2.7V to 4.0V 0.6

ONA/ONB Logic Input Low
Voltage

V

IL

V

IN_

= 4.0V to 5.5V 0.8

V

Logic Input Current V

ON_

= 0V or V

IN_

-1 +1 µA

FLT_ Output Low Voltage I

SINK

= 1mA 0.4 V

FLT_ Output High Leakage
Current

V

IN_

= V

FLT_

= 5.5V 1 µA

Autorestart Current In latched-off state, V

OUT_

= 0V 10 25 50 mA
Autorestart Threshold In latched-off state, rising 0.4 0.5 0.6 V
Autorestart Delay In latched-off state, V

OUT_

> 1V 8 20 40 ms

ELECTRICAL CHARACTERISTICS

(V

INA

= V

INB

= 5V, V

ONA

= V

ONB

= 0V (MAX1558), V

ONA

= V

ONB

= 5V (MAX1558H), R

ISET

= 26kΩ to GND, TA= -40°C to +85°C,

unless otherwise noted.)

PARAMETER

CONDITIONS

UNITS

Supply Voltage Range 2.7 5.5 V

V

IN_

= 5V, TA = +25°C75

Switch On-Resistance R

ON

V

IN_

= 4.4V, TA = 0°C to +85°C 105

mΩ

Standby Supply Current Both switches disabled 6 µA
Quiescent Supply Current Both switches enabled 75 µA
OUT_ Off-Leakage Current Switches disabled, V

OUTA

= V

OUTB

= 0V 10 µA

Undervoltage-Lockout Threshold

V

UVLO

Rising edge, 3% hysteresis 2.3 2.7 V

Continuous Load Current R

ISET

= 26kΩ 1.2 A

R

ISET

= 26kΩ

R

ISET

= 39kΩ

Current-Limit Threshold

R

ISET

= 60kΩ

A

Peak Short-Circuit Current Limit I

SHORT

V

OUT_

= 0V

(I

OUT_

pulsing)

R

ISET

= 26kΩ

A

(PEAK)

Fault-Blanking Timeout Period From I

LIMIT

condition to 50% of V

FLT_

840ms

100 1000

+160

SYMBOL

MIN TYP MAX

V

IN_

- V

OUT_

= 0.5V

1.20 1.60

0.80 1.05

0.50 0.70

1.45 2.60

Typical Operating Characteristics

(V

INA

= V

INB

= 5V, V

ONA

= V

ONB

= 0V (MAX1558), V

ONA

= V

ONB

= 5V (MAX1558H), R

ISET

= 26kΩ to GND. Typical values are at TA=

+25°C, unless otherwise noted.)

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current
USB Switches with Autoreset

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(V

INA

= V

INB

= 5V, V

ONA

= V

ONB

= 0V (MAX1558), V

ONA

= V

ONB

= 5V (MAX1558H), R

ISET

= 26kΩ to GND, TA= -40°C to +85°C,

unless otherwise noted.)

PARAMETER

SYMBOL

CONDITIONS

MIN

TYP

MAX

UNITS

Turn-On Delay t

ON

R

OUT_

= 10Ω, C

OUT_

= 1µF, does not
include rise time (from ON asserted to
V

OUT_

= 10% V

IN_

)

0.5 4.0 ms

Turn-Off Delay from ON t

OFF

R

OUT_

= 10Ω, C

OUT_

= 1µF, does not
include rise time (from ON deasserted to
V

OUT_

= 90% V

IN_

)

µs

V

IN_

= 2.7V to 4.0V 1.6

ONA/ONB Logic Input High
Voltage

V

IH

V

IN_

= 4.0V to 5.5V 2.0

V

V

IN_

= 2.7V to 4.0V 0.6

ONA/ONB Logic Input Low
Voltage

V

IL

V

IN_

= 4.0V to 5.5V 0.8

V

Logic Input Current V

ON_

= 0V or V

IN_

-1 +1 µA

FLT_ Output Low Voltage I

SINK

= 1mA 0.4 V

FLT_ Output High Leakage
Current

V

IN_

= V

FLT_

= 5.5V 1 µA

Autorestart Current In latched-off state, V

OUT_

= 0V 10 50 mA
Autorestart Threshold In latched-off state, rising 0.4 0.6 V
Autorestart Delay In latched-off state, V

OUT_

> 1V 8 40 ms

Note 3: Specifications from 0°C to -40°C are guaranteed by design but not 100% tested.
Note 4: The output voltage at which the device transitions from short-circuit current limit to continuous current limit. See the

Output-

Current Fault Protection section.

CURRENT-LIMIT PROGRAM vs. R

ISET

MAX1558/58H toc01

R

ISET

(kΩ)

CURRENT LIMIT (A)

40 48 52 564428 3632

1.5

1.4

1.3

1.2

1.1

1.0

0.9

0.8

0.7

0.6

1.6

0.5
24 60

QUIESCENT SUPPLY CURRENT

vs. SUPPLY VOLTAGE

MAX1558/58H toc02

SUPPLY VOLTAGE (V)

QUIESCENT CURRENT (µA)

54321

10

20

30

40

50

60

0

06

QUIESCENT CURRENT vs. TEMPERATURE

MAX1558/58H toc03

TEMPERATURE (°C)

QUIESCENT CURRENT (µA)

603510-15

35

40

45

50

30

-40 85

V

IN_

= 5.5V

V

IN_

= 4.5V

V

IN_

= 5V

1000

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

_______________________________________________________________________________________ 5

SHUTDOWN CURRENT vs. TEMPERATURE

MAX1558/58H toc04

TEMPERATURE (°C)

SHUTDOWN CURRENT (µA)

6035-15 10

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0

-40 85

ON_ = V

IN_

(MAX1558)

ON_ = GND (MAX1558H)

SWITCH OFF-LEAKAGE CURRENT

vs. TEMPERATURE

MAX1558/58H toc05

TEMPERATURE (°C)

SWITCH OFF-LEAKAGE CURRENT (nA)

6035-15 10

0.01

0.1

1

10

100

1000

-40 85

ON_ = IN_ (MAX1558)
ON_ = GND
(MAX1558H)

OFF REVERSE-BLOCKING LEAKAGE

CURRENT vs. OUTPUT VOLTAGE

MAX1558/58H toc06

OUTPUT VOLTAGE (V)

OFF REVERSE-BLOCKING LEAKAGE CURRRENT (nA)

54321

0.1

1

10

100

06

NORMALIZED ON-RESISTANCE

vs. TEMPERATURE

MAX1558/58H toc07

TEMPERATURE (°C)

NORMALIZED R

ON

(Ω)

603510-15

0.75

1.00

1.25

1.50

0.50

-40 85

CONTINUOUS CURRENT-LIMIT THRESHOLD

vs. TEMPERATURE

MAX1558/58H toc08

TEMPERATURE (°C)

CONTINUOUS CURRENT-LIMIT THRESHOLD (A)

603510-15

1.40

1.42

1.41

1.39

1.38

1.37

1.36

1.44

1.43

1.45

1.35

-40 85

TURN-ON TIME

vs. TEMPERATURE (t

ON

+ t

RISE

)

MAX1558/58H toc09

TEMPERATURE (°C)

TURN-ON TIME (ms)

603510-15

5

6

7

8

3

4

-40 85

V

IN_

= 4.5V

V

IN_

= 5.5V

V

IN_

= 5V

TURN-OFF TIME

vs. TEMPERATURE (t

OFF

+ t

FALL

)

MAX1558/58H toc10

TEMPERATURE (°C)

TURN-OFF TIME (ms)

603510-15

2.75

3.00

3.25

3.50

3.75

4.00

2.00

2.25

2.50

-40 85

V

IN_

= 4.5V

V

IN_

= 5.5V

V

IN_

= 5V

MAX1558/58H toc11

TEMPERATURE (°C)

655035205-10-25

22

21

24

23

25

20

-40 80

V

IN_

= 4.5V

V

IN_

= 5.5V

V

IN_

= 5V

FAULT-BLANKING TIME (ms)

FAULT-BLANKING TIME

vs. TEMPERATURE

MAX1558/58H toc12

TEMPERATURE (°C)

603510-15

150

175

200

225

250

275

100

125

-40 85

V

IN_

= 4.5V

V

IN_

= 5.5V

V

IN_

= 5V

FAULT OUTPUT LOW VOLTAGE (mV)

FAULT OUTPUT LOW VOLTAGE

vs. TEMPERATURE

Typical Operating Characteristics (continued)

(V

INA

= V

INB

= 5V, V

ONA

= V

ONB

= 0V (MAX1558), V

ONA

= V

ONB

= 5V (MAX1558H), R

ISET

= 26kΩ to GND. Typical values are at TA=

+25°C, unless otherwise noted.)

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current
USB Switches with Autoreset

6 _______________________________________________________________________________________

MAX1558/58H toc13

TEMPERATURE (°C)

603510-15

30

32

34

36

38

40

20

26
24
22

28

-40 85

V

IN_

= 4.5V

V

IN_

= 5.5V

V

IN_

= 5V

AUTORESET CURRENT (mA)

AUTORESET CURRENT

vs. TEMPERATURE

AUTORESET CURRENT

vs. INPUT VOLTAGE

MAX1558/58H toc14

VIN (V)

AUTORESET CURRENT (mA)

5.55.04.54.03.5

25

30

35

40

20

3.0 6.0

TA = +85°C

TA = -40°C

TA = +25°C

OVERLOAD RESPONSE INTO 2.5Ω

MAX1558/58H toc15

20ms/div

I

OUT_

OUT_

V

IN

FLT_

5V

5V/div

5V/div

1A/div

0

0

0

SHORT-CIRCUIT RESPONSE INTO 0Ω

MAX1558/58H toc16

20ms/div

I

OUT_

V

IN

V

OUT

FLTA_

5V/div

5V/div

5V/div
5A/div

0

0

0

0

SHORT
APPLIED

SHORT
REMOVED

SWITCH ON

AUTORESTART

Typical Operating Characteristics (continued)

(V

INA

= V

INB

= 5V, V

ONA

= V

ONB

= 0V (MAX1558), V

ONA

= V

ONB

= 5V (MAX1558H), R

ISET

= 26kΩ to GND. Typical values are at TA=

+25°C, unless otherwise noted.)

SWITCH TURN-ON TIME

MAX1558/58H toc17

2.0ms/div

ON_

OUT_

2V/div

2V/div
0

0

SWITCH TURN-OFF TIME

MAX1558/58H toc18

1.0ms/div

ON_

OUT_

2V/div

2V/div
0

0

Detailed Description

The MAX1558/MAX1558H are dual current-limited
switches designed for USB applications. They have two
independent switches, each with its own enable control
input and autoreset function. Each switch has an error­flag output to notify the USB controller when current­limit, short-circuit, undervoltage-lockout, or thermal­shutdown conditions occur (Figure 2). The MAX1558/
MAX1558H operate from a 2.7V to 5.5V supply. Each
output can supply up to 1.2A. Current limit for both
channels is set with one external resistor.

The MAX1558/MAX1558H have independent thermal
shutdown for each switch in the event of a prolonged
overload. An autoreset function monitors the output and
automatically turns the switch on when the overload is
removed. Separate current limiting and thermal-shut­down circuits permit each switch to operate indepen­dently, improving system robustness.

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

_______________________________________________________________________________________ 7

PIN NAME FUNCTION

1 INA

Power Input for OUTA. Connect INA and INB together and bypass with a 0.1µF capacitor to ground.
Load conditions may require additional bulk capacitance to prevent the input from being pulled down.

2

ONA

*(ONA)

Control Input for Switch A. Can be driven higher than IN_ without damage. A logic low turns switch A on
for the MAX1558. A logic high turns switch A on for the MAX1558H.

3 ISET

Current-Limit Adjust for Both Channels. Connect a resistor between 26kΩ to 60kΩ from ISET to ground to
program the current limit. See Setting the Current Limit in the Applications Information section.

4

ONB

*(ONB)

Control Input for Switch B. Can be driven higher than IN_ without damage. A logic low turns switch B on
for the MAX1558. A logic high turns switch B on for the MAX1558H.

5 INB

Power Input for OUTB. Connect INB and INA together and bypass with a 0.1µF capacitor to ground.
Load conditions may require additional bulk capacitance to prevent the input from being pulled down.

6 OUTB

Power Output for Switch B. Connect a 1µF capacitor from OUTB to ground. The load condition may
require additional bulk capacitance.

7 FLTB

Fault Indicator Output for Switch B. This open-drain output goes low when switch B is in thermal
shutdown or UVLO or in a sustained (>20ms) current-limit or short-circuit condition.

8 GND

Ground

9 FLTA

Fault Indicator Output for Switch A. This open-drain output goes low when switch A is in thermal
shutdown or UVLO or in a sustained (>20ms) current-limit or short-circuit condition.

10 OUTA

Power Output for Switch A. Connect a 1µF capacitor from OUTA to ground. The load condition may
require additional bulk capacitance.

— PAD

Exposed Pad, Internally Connected to GND. Connect exposed pad to a large copper trace for maximum
power dissipation.

Pin Description

*( ) are for the MAX1558H only.

MAX1558

INPUT

2.7V TO 5.5V

INA
INB

ISET

FLTA

FLTB

ONA
ONB

ONA
ONB

OUTA

OUTB

GND

USB
PORT A

USB
PORT B

0.1µF

100kΩ

100kΩ

1µF*

1µF*

*USB APPLICATIONS MAY REQUIRE ADDITIONAL
BULK CAPACITANCE

Figure 1. Typical Application Circuit

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current
USB Switches with Autoreset

8 _______________________________________________________________________________________

MAX1558

CHARGE

PUMP

BIAS

UVLO

REF

OSC

25kHz

TIMER

20ms

THERMAL

SHUTDOWN

CHARGE

PUMP

ILIMB

ILIMA

30mA

INA

ONA

ONB

INB

ISET

ONA

ONB

FAULT
LOGIC

30mA

FLTB

INB

OUTB

GND

OUTA

FLTA

INA

0.6V
PROGRAM ILIMA
PROGRAM ILIMB

Figure 2. Functional Diagram

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

_______________________________________________________________________________________ 9

Undervoltage Lockout and

Input Voltage Requirements

The MAX1558/MAX1558H include a UVLO circuit to
prevent erroneous switch operation when the input volt­age is low during startup and brownout conditions.
Operation is inhibited when V

IN_

is less than 2.5V.

Output-Current Fault Protection

The current limit for both switch outputs is programmed
by a resistor between 26kΩ and 60kΩ connected from
ISET to ground. See the Current-Limit Program Level vs.
R

ISET

curve in the Typical Operating Characteristics and
Setting the Current Limit in the Applications Information
section. The MAX1558 reduces the gate drive to the
MOSFET switch when the programmed current-limit value
is reached. If the current-limit program value is reached,
the part reduces gate drive to regulate at the current limit.
If the current limit persists for 20ms (typ), the output turns
off and the fault flag is set until the fault is removed, as
detected by the autoreset circuit.

When the the output drops below 1V (typ), the current
limit is set 30% above the programmed level and
pulsed. This lowers the RMS current for a short-circuit
condition, which reduces system load current and
power dissipation. If a short circuit persists for 20ms,
the output turns off and the fault flag is set. The autore­set circuit automatically restarts the part if the fault is
removed.

Fault Blanking

The MAX1558/MAX1558H switches can reach current
limit in normal operation when powering up or driving
heavy capacitive loads. To differentiate these conditions
from short circuits or sustained overloads, the
MAX1558/MAX1558H have independent fault-blanking
circuits in each switch. When a load transient causes
the device to enter the current limit, an internal counter
monitors the duration of the fault. For load faults exceed­ing the 20ms fault-blanking time, the offending switch
turns off, the corresponding FLT_ signal asserts low,
and that channel enters autoreset mode (see the
Autoreset Mode section). Only current-limit and short­circuit faults are blanked. Thermal-overload faults and
input-voltage drops below the UVLO threshold immedi­ately cause the switch to turn off and FLT_ to assert low.

Fault blanking allows the MAX1558 to handle USB
loads that may not be fully compliant with USB specifi­cations. USB loads with additional bypass capacitance
and/or large startup currents can be successfully pow­ered even while protecting the upstream power source.
No fault is indicated if the switch is able to bring up the
load within the 20ms blanking period.

Autoreset Mode

If an output fault is detected for more than the 20ms
blanking time, the output latches off and the FLT_ out-
put goes low. The MAX1558/MAX1558H then source
30mA to the faulted output and monitor the output volt­age to determine when the overload is removed. If the
voltage on the output rises above 0.5V for more than
20ms, the fault resets and the output turns on. The
MAX1558 can also be reset from fault manually by tog­gling ON_ (ON_ for the MAX1558H) for that channel.

Reverse Current Blocking

The USB specification does not allow an output device
to source current back into the USB port. However, the
MAX1558/MAX1558H are designed to safely power
noncompliant devices. When disabled, each output is
switched to a high-impedance state, blocking reverse­current flow from the output back to the input. However,
during normal operation with the device enabled, the
MAX1558/MAX1558H are bidirectional switches.

Thermal Shutdown

The MAX1558/MAX1558H feature independent thermal
shutdown for each switch channel, allowing one switch
to deliver power even if the other switch has a fault con­dition. When the junction temperature exceeds +160°C,
the switch turns off and the FLT_ output goes low imme­diately; fault blanking does not occur during thermal
limit. When the junction cools by 10°C, the switch turns
on again. If the fault-overload condition continues, the
switch cycles on and off, resulting in a pulsed output,
saving battery power.

Fault Indicators

The MAX1558/MAX1558H provide an open-drain fault
output (FLT_) for each switch. For most applications, con­nect FLT_ to IN_ through a 100kΩ pullup resistor. FLT_
goes low when any of the following conditions occur:

• The input voltage is below the UVLO threshold.

• The switch junction temperature exceeds the +160°C
thermal-shutdown temperature limit.

• The switch is in current-limit or short-circuit limit mode
after the 20ms fault-blanking period is exceeded.

• The switch is in autoreset mode.

After the fault condition is removed, the FLT_ output
deasserts after a 20ms delay. Ensure that the
MAX1558/MAX1558H have adequate input bypass
capacitance to prevent glitches from triggering FLT_ out-
puts. Glitches that cause the input supply to drop below

2.5V may cause the undervoltage lockout to trigger, turn-

ing the outputs off and asserting the FLT signals.

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current
USB Switches with Autoreset

10 ______________________________________________________________________________________

Applications Information

Setting the Current Limit

A resistor from ISET to ground programs the current­limit value for both outputs. Use a resistor between
26kΩ and 86kΩ to set the current limit according to
the formula:

I

LIM(TYPICAL)

= 36400 / R

ISET

(Amps)

Do not use R

ISET

values below 26kΩ because the maxi­mum current rating of the device may be exceeded.
R

ISET

values larger than 60kΩ are not recommended

and do not provide a lower limit current than 500mA.
If the output drops below 1V (typ), the MAX1558 shifts

to a short-circuit current-limit threshold that is 30%
above the programmed level given by the I

LIM(TYPICAL)

formula. If the short-circuit threshold is exceeded, the
switch shuts off immediately (no 20ms delay) and
ramps the current back up in approximately 3ms. If the
short persists and the current ramps all the way up to
the short-circuit limit again, the switch again turns off. If
the short still persists, the output pulses this way for
20ms, at which time the switch turns off and autoreset
mode begins.

Input Capacitor

INA and INB provide the power for all control and
charge-pump circuitry and must be connected together
externally. Connect a capacitor from IN_ to ground to
limit the input-voltage drop during momentary output
short-circuit conditions. A 0.1µF ceramic capacitor is
required for local decoupling; higher capacitor values
further reduce the voltage drop at the input. When dri­ving inductive loads, a larger capacitance prevents
voltage spikes from exceeding the MAX1558/
MAX1558Hs’ absolute maximum ratings.

Output Capacitor

Place a 1µF or greater capacitor at each output for
noise immunity. When starting up into very large capac­itive loads, the switch may pulse the output current at
the short-circuit current-limit program level until the out­put voltage rises above 1V. Then, the capacitor contin­ues to charge at the full, continuous current-limit
program level. There is no limit to the output capacitor
size, but to prevent a startup fault assertion, the capaci­tor must charge up within the fault-blanking delay peri­od. Typically, starting up into a 500µF or smaller
capacitor does not trigger a fault output. In addition to
bulk capacitance, small-value (0.1µF or greater) ceram­ic capacitors improve the output’s resilience to electro­static discharge (ESD).

Driving Inductive Loads

A wide variety of devices (mice, keyboards, cameras,
and printers) can load the USB port. These devices com­monly connect to the port with cables, which can add an
inductive component to the load. This inductance caus­es the output voltage at the USB port to ring during a
load step. The MAX1558/MAX1558H are capable of dri­ving inductive loads, but avoid exceeding the devices’
absolute maximum ratings. Usually the load inductance
is relatively small, and the MAX1558/MAX1558Hs’
input includes a substantial bulk capacitance from an
upstream regulator as well as local bypass capacitors,
limiting overshoot. If severe ringing occurs due to large
load inductance, clamp the MAX1558/MAX1558Hs’ out­put below +6V and above -0.3V.

Turn-On and Turn-Off Behavior

In the absence of faults, the MAX1558/MAX1558Hs’
internal switches turn on and off slowly under the control
of the ON_ inputs. Transition times for both edges are
approximately 4ms. The slow charge-pump switch drive
minimizes load transients on the upstream power source.
Under thermal fault and UVLO, the power device turns
off rapidly (100ns) to protect the power device.

Layout and Thermal Dissipation

To optimize the switch response time to output short­circuit conditions, keep all traces as short as possible
to reduce the effect of undesirable parasitic induc­tance. Place input and output capacitors no more than
5mm from device leads. All IN_ and OUT_ pins must be
connected with short traces to the power bus. Wide
power-bus planes provide superior heat dissipation
through the switch IN_ and OUT_ pins. While the
switches are on, power dissipation is small and the
package temperature change is minimal. Calculate the
power dissipation for this condition as follows:

P = (I

OUT

_)2R

ON

For the maximum operating current (I

OUT

_ = 1.2A) and
the maximum on-resistance of the switch (125mΩ), the
power dissipation is:

P = (1.2A)

2

x 0.125Ω = 180mW per switch

The worst-case power dissipation occurs when the
switch is in current limit and the output is greater than
1V. The instantaneous power dissipated in each switch
is the voltage drop across the switch multiplied by the
current limit. The fault-blanking circuit turns the output
off if the fault persists for 20ms, while the autoreset cir­cuit can turn it back on after 20ms in the off state. Thus,
the average worst-case power is approximately 50% of
the instantaneous value.

P = 0.5 x (I

LIM

) x (V

IN_

- V

OUT_

)

For a 5V input and 1V output, the maximum possible
power dissipation per switch is:

P = 0.5 x (1.5A) x (5V - 1V) = 3W

Since the package power dissipation is limited to
1952mW, the MAX1558/MAX1558H die temperature
exceeds the thermal-shutdown threshold and the
switch turns off. After the die temperature cools by
10°C, the switch turns on again. If the fault-overload
condition continues, the switch cycles on and off with a
duty cycle and period that is a function of the ambient
temperature and PC board layout.

A short across the output for more than 20ms places
the part in autoreset mode. With V

IN_

= 5V and an
autoreset test current of 30mA, the power dissipation
for a short-circuited output is given by:

P = (30mA) x 5V = 0.15W

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current

USB Switches with Autoreset

______________________________________________________________________________________ 11

Chip Information

TRANSISTOR COUNT: 2932
PROCESS: BiCMOS

MAX1558/MAX1558H

Dual, 3mm x 3mm, 1.2A/Programmable-Current
USB Switches with Autoreset

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.

12 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600

© 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

Package Information

(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages

.)

D

N

PIN 1

INDEX

AREA

NUMBER OF LEADS SHOWN ARE FOR REFERENCE ONLY

COMMON DIMENSIONS

MIN. MAX.

SYMBOL

A 0.70 0.80

D 2.90 3.10

E 2.90 3.10

A1 0.00 0.05

L

A2 0.20 REF.

0.20

0.40

0.25 MIN.k

E

A

DETAIL A

L

E2

C

L

e

C

L

L

e

PACKAGE OUTLINE, 6, 8, 10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm

21-0137

6, 8, &10L, DFN THIN.EPS

1

F

2

PACKAGE VARIATIONS

PKG. CODE

T833-1

T1033-1

N D2 E2 e

2.30±0.101.50±0.106T633-1 0.95 BSC MO229 / WEEA

2.30±0.108

1.50±0.10

1.50±0.10

2.30±0.1010

1.70±0.10 2.30±0.1014T1433-1

1.70±0.10

0.65 BSC

0.50 BSC

0.40 BSC

0.40 BSC

JEDEC SPEC

MO229 / WEEC

MO229 / WEED-3

- - - - 0.20±0.03 2.40 REFT1433-2 14 2.30±0.10

b

0.40±0.05

[(N/2)-1] x e

1.90 REF

1.95 REF0.30±0.05

2.00 REF0.25±0.05

2.40 REF0.20±0.03- - - -

PACKAGE OUTLINE, 6, 8, 10 & 14L,
TDFN, EXPOSED PAD, 3x3x0.80 mm

21-0137

2

F

2