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19-3128; Rev 0; 6/04
Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset
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 (45A) and standby current (3A) 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. 55m 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
Features
MAX1558/MAX1558H
Ordering Information
PART MAX1558ETB TEMP RANGE -40C to +85C -40C to +85C PINPACKAGE 10 TDFN (3mm x 3mm) 10 TDFN (3mm x 3mm) TOP MARK AAR AAS
Applications
USB Ports and Hubs Notebook Computers and Desktops PDAs and Palmtop Computers Docking Stations
INA
MAX1558HETB
Typical Operating Circuit
ONA ONB OUTA
ONA ONB USB PORT A
Pin Configuration
TOP VIEW
INPUT 2.7V TO 5.5V
INB
MAX1558
INA 1 ONA (ONA) 2 ISET 3 ONB (ONB) 4 INB 5 10 OUTA 9 FLTA FLTA OUTB USB PORT B
MAX1558 (MAX1558H)
8 GND 7 FLTB 6 OUTB
FLTB ISET GND
TDFN 3mm x 3mm
________________________________________________________________ Maxim Integrated Products
1
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Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset MAX1558/MAX1558H
ABSOLUTE MAXIMUM RATINGS
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 +1.6ARMS FLT_ Sink Current................................................................20mA Continuous Power Dissipation (TA = +70C) 10-Pin TDFN 3mm x 3mm (derate 24.4mW/C above +70C) .............................1952mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+160C Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10s) .................................+300C
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 1.5ARMS to prevent permanent device damage. When the MAX1558/MAX1558H are disabled, the switch turns off and reverse current is internally blocked.
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
(VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB = 5V (MAX1558H), RISET = 26k to GND, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 3)
PARAMETER Supply Voltage Range VIN_ = 5V, TA = +25C Switch On-Resistance Standby Supply Current Quiescent Supply Current OUT_ Off-Leakage Current Reverse Leakage Current Undervoltage-Lockout Threshold Continuous Load Current Current-Limit Threshold VUVLO RON VIN_ = 3.3V, TA = +25C VIN_ = 4.4V, TA = 0C to +85C Both switches disabled Both switches enabled Switches disabled VOUTA = VOUTB = 0V VOUTA = VOUTB = 5V 3 45 0.03 0.03 0.03 2.3 1.2 RISET = 26k RISET = 39k RISET = 60k Peak Short-Circuit Current Limit ISHORT VOUT_ = 0V (IOUT_ pulsing) VOUT_ = 0V (IOUT_ pulsing) (Note 4) From ILIMIT condition to 50% of V FLT_ tON ROUT_ = 10, COUT_ = 1F, does not include rise time (from ON asserted to VOUT_ = 10% VIN_) 8 0.5 RISET = 26k RISET = 39k RISET = 60k RISET = 26k RISET = 39k RISET = 60k 1.20 0.80 0.50 1.45 1.4 0.925 0.6 2.0 1.40 0.90 0.55 0.37 0.23 1 20 1.4 40 4.0 V ms ms ARMS 1.60 1.05 0.70 2.60 A(PEAK) A 2.5 2.7 SYMBOL CONDITIONS MIN 2.75 55 64 105 6 75 10 A A A A V A TYP MAX 5.50 75 m UNITS V
VIN_ = 0V, VOUTA = VOUTB = 5V, both switches disabled Rising edge, 3% hysteresis RISET = 26k VIN_ - VOUT_ = 0.5V
RMS Short-Circuit Current Limit Short-Circuit Continuous CurrentLimit Transition Threshold Fault-Blanking Timeout Period Turn-On Delay
ISHORT
2
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Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset
ELECTRICAL CHARACTERISTICS (continued)
(VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB = 5V (MAX1558H), RISET = 26k to GND, TA = 0C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 3)
PARAMETER Output Rise Time SYMBOL tRISE CONDITIONS COUT_ = 1F, ROUT_ = 10, (from 10% to 90% of VOUT_) ROUT_ = 10, COUT_ = 1F, does not include rise time (from ON deasserted to VOUT_ = 90% VIN_) COUT_ = 1F, ROUT_ = 10 (from 90% to 10% of VOUT_) 10C hysteresis VIH VIL VIN_ = 2.7V to 4.0V VIN_ = 4.0V to 5.5V VIN_ = 2.7V to 4.0V VIN_ = 4.0V to 5.5V VON_ = 0V or VIN_ ISINK = 1mA VIN_ = V FLT_ = 5.5V In latched-off state, VOUT_ = 0V In latched-off state, rising In latched-off state, VOUT_ > 1V 10 0.4 8 25 0.5 20 -1 1.6 2.0 0.6 0.8 +1 0.4 1 50 0.6 40 MIN TYP 4 MAX UNITS ms
MAX1558/MAX1558H
Turn-Off Delay from ON
tOFF
100
1000
s
Output Fall Time Thermal-Shutdown Threshold ONA/ONB Logic Input High Voltage ONA/ONB Logic Input Low Voltage Logic Input Current FLT_ Output Low Voltage FLT_ Output High Leakage Current Autorestart Current Autorestart Threshold Autorestart Delay
tFALL
3 +160
ms C V V A V A mA V ms
ELECTRICAL CHARACTERISTICS
(VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB = 5V (MAX1558H), RISET = 26k to GND, TA = -40C to +85C, unless otherwise noted.)
PARAMETER Supply Voltage Range Switch On-Resistance Standby Supply Current Quiescent Supply Current OUT_ Off-Leakage Current Undervoltage-Lockout Threshold Continuous Load Current Current-Limit Threshold VUVLO RON VIN_ = 5V, TA = +25C VIN_ = 4.4V, TA = 0C to +85C Both switches disabled Both switches enabled Switches disabled, VOUTA = VOUTB = 0V Rising edge, 3% hysteresis RISET = 26k RISET = 26k VIN_ - VOUT_ = 0.5V VOUT_ = 0V (IOUT_ pulsing) RISET = 39k RISET = 60k Peak Short-Circuit Current Limit Fault-Blanking Timeout Period ISHORT RISET = 26k 2.3 1.2 1.20 0.80 0.50 1.45 8 1.60 1.05 0.70 2.60 40 A(PEAK) ms A SYMBOL CONDITIONS MIN 2.7 TYP MAX 5.5 75 105 6 75 10 2.7 UNITS V m A A A V A
From ILIMIT condition to 50% of V FLT_
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Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset MAX1558/MAX1558H
ELECTRICAL CHARACTERISTICS (continued)
(VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB = 5V (MAX1558H), RISET = 26k to GND, TA = -40C to +85C, unless otherwise noted.)
PARAMETER Turn-On Delay SYMBOL tON CONDITIONS ROUT_ = 10, COUT_ = 1F, does not include rise time (from ON asserted to VOUT_ = 10% VIN_) ROUT_ = 10, COUT_ = 1F, does not include rise time (from ON deasserted to VOUT_ = 90% VIN_) VIN_ = 2.7V to 4.0V VIN_ = 4.0V to 5.5V VIN_ = 2.7V to 4.0V VIN_ = 4.0V to 5.5V VON_ = 0V or VIN_ ISINK = 1mA VIN_ = V FLT_ = 5.5V In latched-off state, VOUT_ = 0V In latched-off state, rising In latched-off state, VOUT_ > 1V 10 0.4 8 -1 1.6 2.0 0.6 0.8 +1 0.4 1 50 0.6 40 MIN 0.5 TYP MAX 4.0 UNITS ms
Turn-Off Delay from ON ONA/ONB Logic Input High Voltage ONA/ONB Logic Input Low Voltage Logic Input Current FLT_ Output Low Voltage FLT_ Output High Leakage Current Autorestart Current Autorestart Threshold Autorestart Delay
tOFF
1000
s
VIH VIL
V V A V A mA V ms
Note 3: Specifications from 0C to -40C 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 OutputCurrent Fault Protection section.
Typical Operating Characteristics
(VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB= 5V (MAX1558H), RISET = 26k to GND. Typical values are at TA = +25C, unless otherwise noted.)
QUIESCENT SUPPLY CURRENT vs. SUPPLY VOLTAGE
MAX1558/58H toc01 MAX1558/58H toc02
CURRENT-LIMIT PROGRAM vs. RISET
1.6 1.5 1.4 1.3 CURRENT LIMIT (A) 1.2 1.1 1.0 0.9 0.8 0.7 0.6 0.5 24 28 32 36 40 44 48 52 56 60 RISET (k) 0 0 60 50 QUIESCENT CURRENT (A) 40 30 20 10
QUIESCENT CURRENT vs. TEMPERATURE
VIN_ = 5.5V QUIESCENT CURRENT (A) 45
MAX1558/58H toc03
50
40 VIN_ = 4.5V 35
VIN_ = 5V
30 1 2 3 4 5 6 -40 -15 10 35 60 85 SUPPLY VOLTAGE (V) TEMPERATURE (C)
4
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Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset
Typical Operating Characteristics (continued)
(VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB= 5V (MAX1558H), RISET = 26k to GND. Typical values are at TA = +25C, unless otherwise noted.)
SWITCH OFF-LEAKAGE CURRENT vs. TEMPERATURE
OFF REVERSE-BLOCKING LEAKAGE CURRRENT (nA)
MAX1558/58H toc05
MAX1558/MAX1558H
SHUTDOWN CURRENT vs. TEMPERATURE
MAX1558/58H toc04
OFF REVERSE-BLOCKING LEAKAGE CURRENT vs. OUTPUT VOLTAGE
MAX1558/58H toc06
4.0 3.5 SHUTDOWN CURRENT (A) 3.0 2.5 2.0 1.5 1.0 0.5 0 -40 -15 10 35 60 ON_ = VIN_ (MAX1558) ON_ = GND (MAX1558H)
1000 SWITCH OFF-LEAKAGE CURRENT (nA) ON_ = IN_ (MAX1558) ON_ = GND (MAX1558H)
100
100
10
10
1
1
0.1
0.01 85 -40 -15 10 35 60 85 TEMPERATURE (C) TEMPERATURE (C)
0.1 0 1 2 3 4 5 6 OUTPUT VOLTAGE (V)
NORMALIZED ON-RESISTANCE vs. TEMPERATURE
MAX1558/58H toc07
CONTINUOUS CURRENT-LIMIT THRESHOLD vs. TEMPERATURE
CONTINUOUS CURRENT-LIMIT THRESHOLD (A)
MAX1558/58H toc08
TURN-ON TIME vs. TEMPERATURE (tON + tRISE)
MAX1558/58H toc09
1.50
1.45 1.44 1.43 1.42 1.41 1.40 1.39 1.38 1.37 1.36 1.35
8
NORMALIZED RON ()
TURN-ON TIME (ms)
1.25
7
VIN_ = 4.5V
6
1.00
5
VIN_ = 5V
VIN_ = 5.5V
0.75
4
0.50 -40 -15 10 35 60 85 TEMPERATURE (C)
3 -40 -15 10 35 60 85 -40 -15 10 35 60 85 TEMPERATURE (C) TEMPERATURE (C)
TURN-OFF TIME vs. TEMPERATURE (tOFF + tFALL)
MAX1558/58H toc10
FAULT-BLANKING TIME vs. TEMPERATURE
MAX1558/58H toc11
FAULT OUTPUT LOW VOLTAGE vs. TEMPERATURE
MAX1558/58H toc12
4.00 3.75 TURN-OFF TIME (ms) 3.50 3.25 3.00 2.75 2.50 2.25 2.00 -40 -15 10 35 60 VIN_ = 4.5V VIN_ = 5V VIN_ = 5.5V
25
275 FAULT OUTPUT LOW VOLTAGE (mV) 250 225 200 175 150 125 100 VIN_ = 5.5V VIN_ = 4.5V VIN_ = 5V
FAULT-BLANKING TIME (ms)
24 VIN_ = 4.5V 23
22 VIN_ = 5V 21 VIN_ = 5.5V
20 85 -40 -25 -10 5 20 35 50 65 80 TEMPERATURE (C) TEMPERATURE (C)
-40
-15
10
35
60
85
TEMPERATURE (C)
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Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset MAX1558/MAX1558H
Typical Operating Characteristics (continued)
(VINA = VINB = 5V, V ONA = V ONB = 0V (MAX1558), VONA = VONB= 5V (MAX1558H), RISET = 26k to GND. Typical values are at TA = +25C, unless otherwise noted.)
AUTORESET CURRENT vs. TEMPERATURE
38 AUTORESET CURRENT (mA) 36 34 32 30 28 26 24 22 20 -40 -15 10 35 60 85 TEMPERATURE (C) 20 3.0 3.5 4.0 4.5 VIN (V) 5.0 5.5 6.0 VIN_ = 4.5V VIN_ = 5V VIN_ = 5.5V
MAX1558/58H toc13
AUTORESET CURRENT vs. INPUT VOLTAGE
MAX1558/58H toc14 MAX1558/58H toc16
40
40
AUTORESET CURRENT (mA)
35
TA = -40C
30 TA = +85C 25 TA = +25C
OVERLOAD RESPONSE INTO 2.5
MAX1558/58H toc15
SHORT-CIRCUIT RESPONSE INTO 0
5V 5V/div VIN SWITCH ON SHORT APPLIED VOUT AUTORESTART FLTA_ 5V/div 0 5A/div 0 SHORT REMOVED 5V/div 0
VIN
OUT_ 0 FLT_ IOUT_ 5V/div 0 1A/div 0 IOUT_
5V/div 0
20ms/div
20ms/div
SWITCH TURN-ON TIME
MAX1558/58H toc17
SWITCH TURN-OFF TIME
MAX1558/58H toc18
ON_ ON_ 2V/div
2V/div 0
0 OUT_ 2V/div 0 OUT_ 2V/div 0 2.0ms/div
1.0ms/div
6
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Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset
Pin Description
PIN 1 2 3 4 5 6 7 8 9 10 -- NAME INA ONA *(ONA) ISET ONB *(ONB) INB OUTB FLTB GND FLTA OUTA PAD FUNCTION Power Input for OUTA. Connect INA and INB together and bypass with a 0.1F capacitor to ground. Load conditions may require additional bulk capacitance to prevent the input from being pulled down. 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. Current-Limit Adjust for Both Channels. Connect a resistor between 26k to 60k from ISET to ground to program the current limit. See Setting the Current Limit in the Applications Information section. 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. Power Input for OUTB. Connect INB and INA together and bypass with a 0.1F capacitor to ground. Load conditions may require additional bulk capacitance to prevent the input from being pulled down. Power Output for Switch B. Connect a 1F capacitor from OUTB to ground. The load condition may require additional bulk capacitance. 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. Ground 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. Power Output for Switch A. Connect a 1F capacitor from OUTA to ground. The load condition may require additional bulk capacitance. Exposed Pad, Internally Connected to GND. Connect exposed pad to a large copper trace for maximum power dissipation.
MAX1558/MAX1558H
*( ) are for the MAX1558H only.
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.
0.1F INA INPUT 2.7V TO 5.5V 100k INB ONA ONB OUTA 1F* ONA ONB USB PORT A
MAX1558
FLTA OUTB 100k FLTB ISET GND 1F* USB PORT B
*USB APPLICATIONS MAY REQUIRE ADDITIONAL BULK CAPACITANCE
Figure 1. Typical Application Circuit _______________________________________________________________________________________ 7
Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset MAX1558/MAX1558H
INA
FLTA INA
ONA ONA
CHARGE PUMP
ILIMA BIAS THERMAL SHUTDOWN UVLO OUTA
30mA
REF
FAULT LOGIC
GND
30mA OSC 25kHz ONB ONB CHARGE PUMP ILIMB TIMER 20ms OUTB
INB
INB 0.6V PROGRAM ILIMA PROGRAM ILIMB FLTB
MAX1558
ISET
Figure 2. Functional Diagram
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Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset
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 VIN_ is less than 2.5V.
Autoreset Mode
If an output fault is detected for more than the 20ms blanking time, the output latches off and the FLT_ output 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.
MAX1558/MAX1558H
Output-Current Fault Protection
The current limit for both switch outputs is programmed by a resistor between 26k and 60k connected from ISET to ground. See the Current-Limit Program Level vs. RISET 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.
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 +160C, the switch turns off and the FLT_ output goes low immediately; fault blanking does not occur during thermal limit. When the junction cools by 10C, 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 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.
Fault Indicators
The MAX1558/MAX1558H provide an open-drain fault output (FLT_) for each switch. For most applications, connect FLT_ to IN_ through a 100k 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 +160C 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_ outputs. Glitches that cause the input supply to drop below 2.5V may cause the undervoltage lockout to trigger, turning the outputs off and asserting the FLT signals.
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Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset MAX1558/MAX1558H
Applications Information
Setting the Current Limit
A resistor from ISET to ground programs the currentlimit value for both outputs. Use a resistor between 26k and 86k to set the current limit according to the formula: ILIM(TYPICAL) = 36400 / RISET (Amps) Do not use RISET values below 26k because the maximum current rating of the device may be exceeded. RISET values larger than 60k 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 ILIM(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.
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.
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 0.1F 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.
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 = (IOUT_)2 RON For the maximum operating current (IOUT_ = 1.2A) and the maximum on-resistance of the switch (125m), the power dissipation is: P = (1.2A)2 x 0.125 = 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 (ILIM) x (VIN_ - VOUT_)
Output Capacitor
Place a 1F 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 500F or smaller capacitor does not trigger a fault output. In addition to bulk capacitance, small-value (0.1F or greater) ceramic capacitors improve the output's resilience to electrostatic discharge (ESD).
10
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Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset
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 10C, 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
Chip Information
TRANSISTOR COUNT: 2932 PROCESS: BiCMOS
MAX1558/MAX1558H
______________________________________________________________________________________
11
Dual, 3mm x 3mm, 1.2A/Programmable-Current USB Switches with Autoreset MAX1558/MAX1558H
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.)
6, 8, &10L, DFN THIN.EPS
C L C L
D N
PIN 1 INDEX AREA
E DETAIL A
E2
A
L e e
L
PACKAGE OUTLINE, 6,8,10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm
-DRAWING NOT TO SCALE-
21-0137
G
1
2
COMMON DIMENSIONS SYMBOL A D E A1 L k A2 MIN. 0.70 2.90 2.90 0.00 0.20 MAX. 0.80 3.10 3.10 0.05 0.40
0.25 MIN. 0.20 REF.
PACKAGE VARIATIONS PKG. CODE T633-1 T633-2 T833-1 T833-2 T833-3 T1033-1 T1433-1 T1433-2 N 6 6 8 8 8 10 14 14 D2 1.500.10 1.500.10 1.500.10 1.500.10 1.500.10 1.500.10 1.700.10 1.700.10 E2 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 2.300.10 e 0.95 BSC 0.95 BSC 0.65 BSC 0.65 BSC 0.65 BSC 0.50 BSC 0.40 BSC 0.40 BSC JEDEC SPEC MO229 / WEEA MO229 / WEEA MO229 / WEEC MO229 / WEEC MO229 / WEEC MO229 / WEED-3 ------b 0.400.05 0.400.05 0.300.05 0.300.05 0.300.05 0.250.05 0.200.05 0.200.05 [(N/2)-1] x e 1.90 REF 1.90 REF 1.95 REF 1.95 REF 1.95 REF 2.00 REF 2.40 REF 2.40 REF
DOWNBONDS ALLOWED
NO NO NO NO YES NO YES NO
PACKAGE OUTLINE, 6,8,10 & 14L, TDFN, EXPOSED PAD, 3x3x0.80 mm
-DRAWING NOT TO SCALE-
21-0137
G
2
2
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 (c) 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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