General Description
The MAX1823 is a dual, current-limited switch with
autoreset specifically made for USB applications. The
autoreset feature latches the switch off if the output is
shorted, saving system power. The switch reactivates
when the short circuit is removed. Each channel is guar-
anteed to supply 720mA and meet USB specifications.
Low quiescent supply current (50µA) and standby current
(3µA) conserve battery power in portable applications.
The MAX1823 has multiple safety features to ensure
that the USB port is protected. Built-in thermal-overload
protection limits power dissipation and junction temper-
ature. Accurate internal current-limiting circuitry pro-
tects the input supply against both overload and
short-circuit conditions. Independent fault signals
(FAULTA and FAULTB) notify the microprocessor (µP)
when a thermal-overload, current-limit, undervoltage-
lockout (UVLO), or short-circuit fault occurs. A 20ms
fault-blanking feature ignores momentary faults, such
as those caused when hot swapping a capacitive load,
preventing false alarms to the host system. The
MAX1823A/MAX1823B also block reverse current (cur-
rent from OUT_ to IN_) while in shutdown.
The MAX1823 is available in a space-saving 10-pin
µMAX package. The MAX1823/MAX1823A are enabled
with an active-low signal, and the MAX1823B/MAX1823H
are enabled with an active-high signal. For a single ver-
sion of this device, refer to the MAX1946 data sheet. For
a triple version, refer to the MAX1940 data sheet.
Applications
USB Ports and Hubs
Notebook and Desktop Computers
PDAs and Palmtop Computers
Docking Stations
Features
♦Dual USB Switch in Tiny 10-Pin µMAX Package
♦Autoreset Feature Saves Power
♦Guaranteed 720mA Load per Channel
♦Built-In 20ms Fault Blanking
♦Compliant to USB Specification
♦Blocks Reverse Current in Shutdown
(MAX1823A/MAX1823B)
♦4V to 5.5V Input Voltage Range
♦Independent Shutdown Control
(MAX1823/MAX1823A—Active Low)
(MAX1823B/MAX1823H—Active High)
♦Independent FAULT Indicator Outputs
♦Thermal-Overload Protection
♦50µA Quiescent Current (Both Switches On)
♦3µA Standby Current
♦UL Recognized
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and Autoreset
________________________________________________________________ Maxim Integrated Products 1
Ordering Information
Typical Operating Circuit
19-1903; Rev 3; 10/03
PART TEMP RANGE PIN-PACKAGE
MAX1823EUB -40°C to +85°C 10 µMAX
MAX1823AEUB -40°C to +85°C 10 µMAX
MAX1823BEUB -40°C to +85°C 10 µMAX
MAX1823HEUB -40°C to +85°C 10 µMAX
Pin Configuration
ONBONB
ONAONA
GND
MAX1823
MAX1823A
FAULTB
FAULTA
IN
INA
INB
USB
PORT A
OUTA
USB
PORT B
OUTB
INPUT
4V TO 5.5V
1
2
3
4
5
10
9
8
7
6
OUTA
GND
OUTBINB
IN
INA MAX1823
MAX1823A
MAX1823B
MAX1823H
µMAX
TOP VIEW
*(ONA) ONA
*(ONB) ONB
*( ) ARE FOR MAX1823B/MAX1823H.
FAULTB
FAULTA
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.
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and Autoreset
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, INA, INB, ONA, ONB, ONA, ONB
OUTA, OUTB to GND ...........................................-0.3V to +6V
FAULTA, FAULTB to GND..........................-0.3V to (VIN_ + 0.3V)
MAX1823/MAX1823H, INA, IN to OUTA;
INB, IN to OUTB ...................................................-0.3V to +6V
MAX1823A/MAX1823B, INA, IN to OUTA;
INB, IN to OUTB (when disabled, Note 3)...............-6V to +6V
INA, IN to OUTA; INB, IN to OUTB
(when enabled, Note 4)..............................-1.5A to +1.5ARMS
FAULTA, FAULTB Current .................................................20mA
Continuous Power Dissipation (TA= +70°C)
10-Pin µMAX (derate 5.6mW/°C above +70°C) ...........444mW
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
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage Range 4.0 5.5 V
TA = +25°C, each switch,
MAX1823/MAX1823H 75 105
TA = +25°C, each switch,
MAX1823A/MAX1823B 90 120
TA = 0°C to +85°C, each switch,
MAX1823/MAX1823H 135
Switch On-Resistance RON
TA = 0°C to +85°C, each switch,
MAX1823A/MAX1823B 165
mΩ
Standby Supply Current ON_ = IN_ (MAX1823/MAX1823A), ON_ =
GND (MAX1823B/MAX1823H) 310µA
IOUTA = IOUTB = 0A, one channel on 40 80
Quiescent Supply Current
IOUTA = IOUTB = 0A, both channels on 50 100
µA
ON_ = IN _ ( MAX 1823/M AX1823A), ON _ = GND
(M AX1823B/M AX1823H), VOUTA = VOUTB = 0V,
TA = +25oC
0.02 1.00
OUT_ Off-Leakage Current
ON_ = IN_ (MAX1823/MAX1823A), ON_ =
GND (MAX1823B/MAX1823H),
VOUTA = VOUTB = 0V, TA = 0oC to +85oC
0.02 10.00
µA
Undervoltage-Lockout Threshold VUVLO Rising edge, 3% hysteresis 3.0 3.4 3.8 V
Continuous Load Current 720 mA
Continuous Current Limit ILIM VIN - VOUT_ = 0.5V 0.72 0.90 1.20 A
VOUT_ = 0V (IOUT pulsing) 0.8 1.2 1.6 APEAK
Short-Circuit Current Limit ISHORT VOUT_ = 0V (IOUT pulsing) 0.35 ARMS
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VIN = VINA = VINB = 5V, ONA = ONB = GND (MAX1823/MAX1823A), ONA = ONB = IN (MAX1823B/MAX1823H),
TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and Autoreset
_______________________________________________________________________________________ 3
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Short-Circuit Detect Threshold (Note 1) 1 V
Continuous Current-Limit
Blanking Timeout Period
From continuous current-limit condition to
FAULT_ assertion 10 20 35 ms
Short-Circuit Blanking Timeout
Period
From short-circuit current-limit condition to
FAULT_ assertion 7.5 18 35.0 ms
MAX1823/MAX1823H 0.5 1.2 4.0
Turn-On Delay tON
ROUT_ = 10kΩ,
does not include
rise time MAX1823A/MAX1823B 0.3 0.8 3.0
ms
Output Rise Time tRISE ROUT_ = 10Ω, from 10% to 90% of VOUT_ 2.5 ms
ROUT_ = 10Ω, does not include fall time (from
ON_ (MAX1823) or ON_ (MAX1823H)
deasserted to VOUT = 90% of VIN_)
0.8 3.0
Turn-Off Delay from ON tOFF ROUT_ = 10Ω, does not include fall time (from
ON_ (MAX1823A) or ON_ (MAX1823B)
deasserted to VOUT = 90% of VIN_)
0.1 3.0
ms
ROUT_ = 10Ω, from 90% to 10% of VOUT_
(MAX1823/MAX1823H) 2.5
Output Fall Time tFALL ROUT_ = 10Ω, from 90% to 10% of VOUT_
(MAX1823A/MAX1823B) 2.8
ms
Thermal-Shutdown Threshold 15oC hysteresis +160 oC
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 ON_ = GND or IN_ (MAX1823/MAX1823A),
ON_ = GND or IN_ (MAX1823B/MAX1823H) -1 +1 µA
FAULT_ Output Low Voltage ISINK = 1mA, VIN_ = 4V 0.4 V
FAULT_ Output High Leakage
Current VIN_ = V FAULT_ = 5.5V 1 µA
Autoreset OUT_ Current In latched-off state, VOUT_ = 0V 10 30 45 mA
Autoreset Threshold In latched-off state, rising 0.4 0.5 0.6 V
Autoreset Blanking Time In latched-off state, VOUT_ > 0.5V 10 20 35 ms
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = VINA = VINB = 5V, ONA = ONB = GND (MAX1823/MAX1823A), ONA = ONB = IN (MAX1823B/MAX1823H),
TA = 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and Autoreset
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 1, VIN = VIN_ = VON_ = 5V (MAX1823B/MAX1823H); VIN = VIN_ = 5V, ON_ = GND (MAX1823/MAX1823A), TA = -40°C
to +85°C, unless otherwise noted.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Supply Voltage Range 4.0 5.5 V
Each switch, MAX1823/MAX1823H 135
Switch On-Resistance RON Each switch, MAX1823A/MAX1823B 165 mΩ
Standby Supply Current ON_ = IN_ (MAX1823/MAX1823A),
ON_ = GND (MAX1823B/MAX1823H) 10 µA
IOUTA = IOUTB = 0A, one channel on 80
Quiescent Supply Current
IOUTA = IOUTB = 0A, both channels on 100
µA
OUT_ Off-Leakage Current
ON_ = IN_ (MAX1823/MAX1823A),
ON_ = GND (MAX1823B/MAX1823H),
VOUTA = VOUTB = 0V
10 µA
Undervoltage-Lockout Threshold VUVLO Rising edge, 3% hysteresis 3.0 3.8 V
Continuous Load Current 720 mA
Continuous Current Limit ILIM VIN_ - VOUT_ = 0.5V 0.72 1.20 A
Current Limit into Short Circuit ISHORT VOUT_ = 0V (IOUT pulsing) 0.8 1.6 APEAK
Continuous Current-Limit
Blanking Timeout Period
From continuous current-limit condition to
FAULT_ assertion 10 35 ms
Short-Circuit Blanking Timeout
Period
From short-circuit current-limit condition to
FAULT_ assertion 7.5 35.0 ms
MAX1823/MAX1823H 0.5 4.0
Turn-On Delay tON
ROUT_ = 10kΩ,
does not include
rise time MAX1823A/MAX1823B 0.3 3.0
ms
Turn-Off Delay from ON tOFF
ROUT_ = 10Ω, does not include fall time
(from ON_ (MAX1823/MAX1823A) or ON_
(MAX1823B/MAX1823H) deasserted to
VOUT_ = 90% VIN_)
3ms
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and Autoreset
_______________________________________________________________________________________ 5
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 1, VIN = VIN_ = VON_ = 5V (MAX1823B/MAX1823H); VIN = VIN_ = 5V, ON_ = GND (MAX1823/MAX1823A), TA = -40°C
to +85°C, unless otherwise noted.) (Note 2)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
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 VIN_ -1 +1 µA
FAULT_ Output Low Voltage ISINK = 1mA, VIN_ = 4V 0.4 V
FAULT_ Output High Leakage
Current VIN_ = V FAULT_ = 5.5V 1 µA
Autoreset OUT_Current In latched-off state, VOUT_ = 0V 10 50 mA
Autoreset Threshold In latched-off state, rising 0.4 0.6 V
Autoreset Blanking Time In latched-off state, VOUT_ > 0.5V 10 35 ms
Note 1: 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.
Note 3: Reverse current (current from OUT_ to IN_) is blocked when disabled.
Note 4: 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 MAX1823A/MAX1823B
are disabled, the switch turns off and reverse current is internally blocked.
Typical Operating Characteristics
(Circuit of Figure 1, VIN = VINA = VINB = 5V, ON_=GND (MAX1823/MAX1823A), ON_ = IN_ (MAX1823B/MAX1823H), TA= +25°C,
unless otherwise noted.)
0
18
12
6
24
30
36
42
48
54
60
021 3456
QUIESCENT CURRENT
vs. INPUT VOLTAGE
MAX1823 toc01
INPUT VOLTAGE (V)
QUIESCENT CURRENT (µA)
45
47
51
49
53
55
-40 10-15 35 60 85
QUIESCENT CURRENT
vs. TEMPERATURE
MAX1823 toc02
TEMPERATURE (°C)
QUIESCENT CURRENT (µA)
VIN_
=
5.5V
VIN_
=
4.5V
VIN_
=
5V
2.5
2.7
3.1
2.9
3.3
3.5
-40 10-15 35 60 85
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX1823 toc03
TEMPERATURE (°C)
SHUTDOWN SUPPLY CURRENT (µA)
ON_ = IN_ (MAX1823/MAX1823A)
ON_ = GND (MAX1823B/MAX1823H)
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and Autoreset
6 _______________________________________________________________________________________
940
930
920
910
900
-40 10-15 35 60 85
MAX1823 toc06
TEMPERATURE (°C)
CONTINUOUS CURRENT LIMIT (mA)
CONTINUOUS CURRENT-LIMIT
THRESHOLD vs. TEMPERATURE
VIN_
=
5.5V
VIN_
=
4.5V
VIN_
=
5V
0.01
0.1
10
1
100
1000
-40 10-15 35 60 85
SWITCH OFF-LEAKAGE
vs. TEMPERATURE
MAX1823 toc04
TEMPERATURE (°C)
SWITCH OFF-LEAKAGE (nA)
1.50
1.25
1.00
0.75
0.50
-40 10-15 35 60 85
NORMALIZED RON vs. TEMPERATURE
MAX 1823 toc05
TEMPERATURE (°C)
NORMALIZED RON
3.0
3.2
3.6
3.4
3.8
4.0
-40 10-15 35 60 85
TURN-ON TIME
vs. TEMPERATURE (tON + tRISE)
MAX1823 toc07
TEMPERATURE (°C)
TURN-ON TIME (ms)
VIN_
=
5.5V
VIN_
=
4.5V
VIN_
=
5V
2.5
2.7
3.1
2.9
3.3
3.5
-40 10-15 35 60 85
TURN-OFF TIME
vs. TEMPERATURE (tOFF + tFALL)
MAX1823 toc08
TEMPERATURE (°C)
TURN-OFF TIME (ms)
VIN_
=
5.5V
VIN_
=
4.5V
VIN_
=
5V
21.0
21.2
21.6
21.4
21.8
22.0
-40 10-15 35 60 85
FAULT-BLANKING TIME
vs. TEMPERATURE
MAX1823 toc09
TEMPERATURE (°C)
FAULT-BLANKING TIME (ms)
VIN_
=
5.5V
VIN_
=
4.5V
VIN_
=
5V
0.100
0.150
0.125
0.200
0.175
0.225
0.250
-40 10-15 35 60 85
FAULT_ OUTPUT LOW VOLTAGE
vs. TEMPERATURE
MAX1823 toc10
TEMPERATURE (°C)
FAULT_ OUTPUT LOW VOLTAGE (V)
VIN_
=
5.5V
VIN_
=
4.5V
VIN_
=
5V
IFAULT_ = 1mA
15
20
30
25
35
40
-40 10-15 35 60 85
AUTORESET CURRENT vs. TEMPERATURE
(MAX1823/MAX1823H)
MAX1823 toc11
TEMPERATURE (°C)
AUTORESET CURRENT (mA)
VIN_
=
5.5V
VIN_
=
4.5V
VIN_
=
5V
28
30
32
34
36
-40 10-15 35 60 85
AUTORESET CURRENT vs. TEMPERATURE
(MAX1823A/MAX1823B)
MAX1823 toc12
TEMPERATURE (°C)
AUTORESET CURRENT (mA)
VIN_
=
5.5V
VIN_
=
4.5V
VIN_
=
5V
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = VINA = VINB = 5V, ON_=GND (MAX1823/MAX1823A), ON_ = IN_ (MAX1823B/MAX1823H), TA= +25°C,
unless otherwise noted.)
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and Autoreset
_______________________________________________________________________________________ 7
0
10
30
20
40
50
MAX1823 toc13
INPUT VOLTAGE (V)
AUTORESET CURRENT (mA)
3.6 5.24.4 6.0
AUTORESET CURRENT vs. INPUT VOLTAGE
(MAX1823/MAX1823H)
TA = +25°C
TA = -40°C
TA = +85°C
25
27
29
33
35
31
37
39
MAX1823 toc14
INPUT VOLTAGE (V)
AUTORESET CURRENT (mA)
3.6 5.24.4 6.0
AUTORESET CURRENT vs. INPUT VOLTAGE
(MAX1823A/MAX1823B)
TA = +25°C
TA = +85°C
TA = -40°C
10ms/div
OVERLOAD RESPONSE INTO 2.5Ω
(MAX1823/MAX1823H)
A: VIN_, 5V/div
B: VOUTA, 5V/div
C: VFAULTA, 5V/div
D: IOUTA, 1A/div
A
B
D
C
MAX1823 toc15
5V
0
0
0
10ms/div
OVERLOAD RESPONSE INTO 2.5Ω
(MAX1823A/MAX1823B ONLY)
A: VIN_, 5V/div
B: VOUTA, 5V/div
C: VFAULTA, 5V/div
D: IOUTA, 1A/div
A
B
D
C
MAX1823 toc16
5V
0
0
0
500µs/div
OVERLOAD RESPONSE INTO 2.5Ω
(EXPANDED TIME SCALE)
A: VIN_, 5V/div
B: VOUTA, 5V/div
A
B
D
C
MAX1823 toc17
5V
0
0
0
C: VFAULTA, 5V/div
D: IOUTA, 1A/div
10ms/div
SHORT-CIRCUIT RESPONSE INTO 0Ω
(MAX1823/MAX1823H)
A
B
D
C
MAX1823 toc18
5V
0
0
0
C: VFAULTA, 5V/div
D: IOUTA, 1A/div
A: VIN_, 5V/div
B: VOUTA, 5V/div
10ms/div
SHORT-CIRCUIT RESPONSE INTO 0Ω
(MAX1823A/MAX1823B)
A
B
D
C
MAX1823 toc19
5V
0
0
0
C: VFAULTA, 5V/div
D: IOUTA, 2A/div
A: VIN_, 5V/div
B: VOUTA, 5V/div
500µs/div
SHORT-CIRCUIT RESPONSE INTO 0Ω
(EXPANDED TIME SCALE)
A: VIN_, 5V/div
B: VOUTA, 5V/div
A
B
D
C
MAX1823 toc20
5V
0
5V
0
C: VFAULTA, 5V/div
D: IOUTA, 2A/div
1ms/div
SWITCH TURN-ON TIME
(MAX1823/MAX1823A)
A: VONA, 5V/div
B: VOUTA, 2V/div
A
B
MAX1823 toc21
0
0
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = VINA = VINB = 5V, ON_=GND (MAX1823/MAX1823A), ON_ = IN_ (MAX1823B/MAX1823H), TA= +25°C,
unless otherwise noted.)
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and Autoreset
8 _______________________________________________________________________________________
Pin Description
PIN NAME FUNCTION
1ONA
*(ONA)
C ontr ol Inp ut for S w i tch A. C an b e d r i ven hi g her than IN_ w i thout d am ag e. A l og i c l ow tur ns sw i tch A on for
the M AX 1823/M AX 1823A, and a l og i c hi g h tur ns sw i tch A on for the M AX 1823B/M AX 1823H .
2, 3, 4 INA, IN,
INB
Power Input. Connect all IN_ pins 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.
5ONB
*(ONB)
Control Input for Switch B. Can be driven higher than IN_ without damage. A logic low turns switch B
on for the M AX 1823/M AX 1823A, and a logic high turns switch B on for the M AX 1823B/M AX 1823H .
6FAULTB 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.
7 OUTB Power Output for Switch B. Connect a 1µF capacitor from OUTB to ground. Load condition may
require additional bulk capacitance.
8 GND Ground
9 OUTA Power Output for Switch A. Connect a 1µF capacitor from OUTA to ground. Load condition may
require additional bulk capacitance.
10 FAULTA 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.
1ms/div
SWITCH TURN-OFF TIME
(tOFF + tFALL)
A: VONA, 5V/div
B: VOUTA, 2V/div
A
B
MAX1823 toc22
0
0
500µs/div
STARTUP TIME
(TYPICAL USB APPLICATION)
A: VONA, 5V/div
B: VFAULTA, 5V/div
A
B
MAX1823 toc23
0
5V
C
D
0
0
C: VOUTA, 2V/div
D : IOUTA, 0.5A/div
Typical Operating Characteristics (continued)
(Circuit of Figure 1, VIN = VINA = VINB = 5V, ON_=GND (MAX1823/MAX1823A), ON_ = IN_ (MAX1823B/MAX1823H), TA= +25°C,
unless otherwise noted.)
*() are for the MAX1823B/MAX1823H only.
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and Autoreset
_______________________________________________________________________________________ 9
Detailed Description
The MAX1823 is a dual, current-limited switch designed
for USB applications. It has two independent switches,
each with its own enable control input and autoreset
function. Each switch has an error-flag output to notify
the USB controller when the current-limit, short-circuit,
undervoltage-lockout, or thermal-shutdown threshold is
reached (Figure 2).
The MAX1823 operates from a 4V to 5.5V input voltage
range and guarantees a minimum 720mA output current.
A built-in 0.9A current limit limits the current in the event
of a heavy-overload condition. The MAX1823 has inde-
pendent thermal shutdown for each switch in the event
of a prolonged overload or short-circuit condition. The
autoreset function monitors the overload and automati-
cally turns the switch on when the overload is removed.
Use of low-RON NMOS switches enables the MAX1823
to provide two switches in the ultra-small 10-pin µMAX
package. An internal micropower charge pump gener-
ates the high-side supply needed for driving the gates
of these high-side switches. Separate current-limiting
and thermal-shutdown circuits permit each switch to
operate independently, improving system robustness.
Undervoltage-Lockout and
Input-Voltage Requirements
The MAX1823 includes a UVLO circuit to prevent erro-
neous switch operation when the input voltage goes
low during startup and brownout conditions. Operation
is inhibited when VIN_ is less than 3.4V.
Output Fault Protection
The MAX1823 senses the switch output voltage and
selects continuous current limiting when VOUT is greater
than 1V or short-circuit current limiting when VOUT is less
than 1V. When VOUT is greater than 1V, the device oper-
ates in a continuous current-limit mode that sets the out-
put current limit to 0.9A. When VOUT is less than 1V, the
device operates in short-circuit current-limit mode,
sourcing 0.35ARMS current pulses to the load.
Autoreset Mode
If an output fault is detected for more than the 20ms
blanking time, the output latches off, the FAULT_ output
goes low, and a 25mA current is forced at the output. If
the voltage on the output exceeds 0.5V for 20ms, the fault
resets, the 25mA current source shuts down, and the out-
put turns on. The device monitors the output voltage so
that a short-circuit condition can be detected. Active
loads are not expected to have measurable currents
when the supply is below 0.5V. The MAX1823/MAX1823A
can also be reset from fault manually by toggling ON_
(ON_ for the MAX1823B/MAX1823H) for that channel.
Thermal Shutdown
The MAX1823 features 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 FAULT_ output goes low imme-
diately; fault blanking does not occur during thermal
limit. When the junction cools by 15°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.
Reverse Current Blocking
The USB specification does not allow an output device
to source current back into the USB port. However, the
MAX1823A/MAX1823B are designed to safely power
noncompliant devices. When disabled, each output is
switched to a high-impedance state, blocking reverse
current flow from the output back to the input. However,
during normal operation with the device enabled, the
MAX1823A/MAX1823B are bidirectional switches.
Fault Indicators
The MAX1823 provides an open-drain fault output
(FAULT_) for each switch. For most applications, connect
FAULT_ to IN_ through a 100kΩpullup resistor. FAULT_
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 fault-blanking period is exceeded.
•The switch is in autoreset mode.
ONBONB
ONAONA
GND
MAX1823
FAULTB
FAULTA
IN
INA
INB
USB
PORT A
OUTA
USB
PORT B
OUTB
INPUT
4V TO 5.5V 0.1µF
100kΩ
100kΩ
1µF*
* USB APPLICATIONS MAY REQUIRE
ADDITIONAL BULK CAPACITANCE.
1µF*
Figure 1. Typical Application Circuit
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and Autoreset
10 ______________________________________________________________________________________
After the fault condition is removed, the FAULT_ output
deasserts after a 20ms delay. Ensure that the MAX1823
has adequate input bypass capacitance to prevent
glitches from triggering FAULT_ outputs. Input glitches
greater than 0.2V/µs may cause erroneous FAULT_
indications.
Behavior During Current Limit
and Fault Blanking
The MAX1823 limits switch current in three ways. When
ON_ is deasserted (high for MAX1823/MAX1823A, low
for MAX1823B/MAX1823H), the switch is off and leak-
age dominates the residual output current. When ON_
is asserted (low for MAX1823/MAX1823A, high for
MAX1823B/MAX1823H), the switch supplies a continu-
ous output current of at least 720mA. When the output
current exceeds the 0.9A threshold, the MAX1823 lim-
its the current depending on the output voltage. For
VOUT_ greater than 1V (current-limit mode), the
MAX1823 regulates the output current to 0.9A. For
VOUT_ less than 1V (short-circuit mode), the MAX1823
pulses the switch, decreasing the current to 0.35ARMS
(Table 1). Note that a thermal overload may result from
either of these high-current conditions.
The MAX1823 switches may enter current limit in nor-
mal operation when powering up or driving heavy
capacitive loads. To differentiate these conditions from
short circuits or sustained overloads that may damage
the device, the MAX1823 has an independent fault-
blanking circuit in each switch. When a load transient
causes the device to enter current limit, an internal
counter starts to monitor the duration of the fault. For
load faults exceeding 20ms fault-blanking time, the
switch turns off, the FAULT_ signal asserts low, and the
device enters autoreset mode (see the Autoreset Mode
section). Only current-limit and short-circuit faults are
blanked. Thermal-overload faults and input voltage
drops below the UVLO threshold immediately cause
the switch to turn off and FAULT_ to assert low.
ONA
MAX1823/MAX1823A
MAX1823B/MAX1823H
CHARGE
PUMP
ONB
CHARGE
PUMP
*(ONA)
*(ONB)
*( ) ARE FOR THE MAX1823B/MAX1823H.
OSC
25kHz
BIAS
UVLO
REF GND
0.1µF
4V TO 5.5V
IN_
TIMER
20ms
THERMAL
SHUTDOWN
FAULT
LOGIC
ILIM
25mA
25mA
1µF
OUTA
FAULTB
FAULTA
ILIM 1µF
OUTB
INA
INA
INB
INB
Figure 2. Functional Diagram
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and Autoreset
______________________________________________________________________________________ 11
Table 1. MAX1823 Current Limiting and Fault Behavior
Fault blanking allows the MAX1823 to handle USB loads
that may not be fully compliant with the USB specifica-
tions. USB loads with additional bypass capacitance
and/or large startup currents can be successfully pow-
ered 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.
Applications Information
Input Power Source
IN, INA, and INB provide the power for all control and
charge-pump circuitry. All three IN_ pins must be con-
nected together externally. The input-voltage slew rate
should be less than 0.2V/µs to prevent erroneous
FAULT_ indications. This condition should not occur
under normal USB applications.
Input Capacitor
Connect a capacitor from IN_ to ground to limit the input
voltage drop during momentary output short-circuit con-
ditions. A 0.1µF ceramic capacitor is required for local
decoupling; higher capacitor values further reduce the
voltage drop at the input (see the Typical Application
Circuit (Figure 1)). When driving inductive loads, a larg-
er capacitance prevents voltage spikes from exceeding
the MAX1823’s 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 pulses the output current at 0.35ARMS
until the output voltage rises above 1V, then the capacitor
continues to charge at the full 0.9A current limit. There is
no limit to the output capacitor size, but to prevent a start-
up fault assertion, the capacitor must charge up within
the fault-blanking delay period. Typically, starting up into
a 330µF or smaller capacitor does not trigger a fault out-
put. 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 com-
monly 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 MAX1823 is capable of driving inductive loads,
but avoids exceeding the device’s absolute maximum rat-
ings. Usually the load inductance is relatively small, and
the MAX1823’s input includes a substantial bulk capaci-
tance from an upstream regulator as well as local bypass
capacitors, limiting overshoot. If severe ringing occurs
due to large load inductance, clamp the MAX1823’s out-
put below 6V and above -0.3V.
CONDITION MAX1823 BEHAVIOR
Output short circuit
(VOUT < 1V)
•An output short circuit ramps the current to ISHORT in 2ms to 3ms, the switch shuts off, the
blanking timer turns on, FAULT_ stays high, and the output current pulses at 0.35ARMS.
•Removing the short circuit before the 15ms short-circuit blanking timeout period allows the
next ramped current pulse to soft-start the output. The FAULT_ flag stays high.
•A short circuit exceeding 15ms to 20ms forces FAULT_ low at 20ms, enables autoreset
mode, and sources 25mA at the output.
•An output voltage above 0.5V for 20ms resets the switch, turns on the output, and forces
FAULT_ high.
Output overload current
(VOUT > 1V)
•An output overload regulates the current at ILIM (0.9A), and FAULT_ stays high until the
overload is removed, a thermal fault occurs, or the 20ms continuous current-limit timeout
period is reached.
•An overcurrent condition still present at 20ms forces FAULT_ low, enables autoreset, and
sources 25mA at the output.
•An output voltage above 0.5V for 20ms resets the switch, turns on the output, and forces
FAULT_ high.
Thermal fault
(TJ > +160°C)
•A junction temperature of +160°C immediately forces FAULT_ low (the blanking timer does
not apply to thermal faults) and turns off the switch. The junction cooling 15°C removes the
thermal fault condition, enables autoreset mode, and sources 25mA at the output. FAULT_
remains low while a thermal fault condition is present.
•An output voltage above 0.5V for 20ms resets the switch, turns on the output, and forces
FAULT_ high.
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and Autoreset
12 ______________________________________________________________________________________
Turn-On and Turn-Off Behavior
In the absence of faults, the MAX1823’s internal switches
turn on and off slowly under the control of the ON_
inputs. Transition times for both edges are provided in
the Electrical Characteristics table. 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 short-
circuit conditions, keep all traces as short as possible
to reduce the effect of undesirable parasitic induc-
tance. 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_)2RON
For the normal operating current (IOUT_ = 0.5A), and
the maximum on-resistance of the switch (135mΩ), the
power dissipation is:
P = (0.5A)2x 0.135Ω= 34mW per switch
The worst-case power dissipation occurs when the
switch is in current limit and the output is greater than
1V. In this case, the power dissipated in each switch is
the voltage drop across the switch multiplied by the
current limit:
P = (ILIM) (VIN - VOUT)
For a 5V input and 1V output, the maximum power dis-
sipation per switch is:
P = (1.2A) ( 5V - 1V) = 4.8W
Since the package power dissipation is only 444mW,
the MAX1823 die temperature exceeds the thermal-
shutdown threshold, and the switch output shuts down
until the junction temperature cools by 15°C. The duty
cycle and period are strong functions of the ambient
temperature and the PC board layout.
A short circuit at the output causes the power dissipated
across the switch and the junction temperature to
increase. If the fault condition persists, the thermal-
overload-protection circuitry activates, and the output
shuts down until the junction temperature decreases by
15°C (see the Thermal Shutdown section).
Since the output short-circuit current is 25mA (typ), and
with VIN_ = 5V, calculate the power dissipation for a
short-circuited output as follows:
P = (0.025A)(5) = 0.125W
Chip Information
TRANSISTOR COUNT: 3227
PROCESS: BiCMOS
MAX1823/MAX1823A/MAX1823B/MAX1823H
Dual USB Switch with Fault
Blanking and 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.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 13
© 2003 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
10LUMAX.EPS
PACKAGE OUTLINE, 10L uMAX/uSOP
1
1
21-0061 I
REV.DOCUMENT CONTROL NO.APPROVAL
PROPRIETARY INFORMATION
TITLE:
TOP VIEW
FRONT VIEW
1
0.498 REF
0.0196 REF
S
6∞
SIDE VIEW
α
BOTTOM VIEW
0∞ 0∞ 6∞
0.037 REF
0.0078
MAX
0.006
0.043
0.118
0.120
0.199
0.0275
0.118
0.0106
0.120
0.0197 BSC
INCHES
1
10
L1
0.0035
0.007
e
c
b
0.187
0.0157
0.114
H
L
E2
DIM
0.116
0.114
0.116
0.002
D2
E1
A1
D1
MIN
-A
0.940 REF
0.500 BSC
0.090
0.177
4.75
2.89
0.40
0.200
0.270
5.05
0.70
3.00
MILLIMETERS
0.05
2.89
2.95
2.95
-
MIN
3.00
3.05
0.15
3.05
MAX
1.10
10
0.6±0.1
0.6±0.1
ÿ 0.50±0.1
H
4X S
e
D2
D1
b
A2 A
E2
E1 L
L1
c
α
GAGE PLANE
A2 0.030 0.037 0.75 0.95
A1
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.)
