MAX14545 [MAXIM]
28V-Capable, ILIM VBUS Accessory Switch; 28V -能干， ILIM VBUS配件开关
| 型号： | MAX14545 |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 28V-Capable, ILIM VBUS Accessory Switch |
| 文件： | 总10页 (文件大小：1139K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-5037; Rev 0; 1/10
28V-Capable, I V
Accessory Switch
LIM BUS
General Description
Features
The MAX14544/MAX14545 are overcurrent detection
switches that can provide power to external accesso-
ries while preventing the host device from damage due
to faulty overload conditions. These analog switches
feature a 270mω (typ) on-resistance and operate from
a +2.3V to +5.5V input voltage range. The selectable
current limit of 200mA or 400mA makes them ideal for
load-switching applications.
S 200mA or 400mA Selectable Current Limit
S Output Capable of Withstanding +28V
S Reverse-Current Shutdown Protection
S +2.3V to +5.5V Input Operation Range
S Undervoltage Lockout
S Autoretry or Latchoff Option
S Thermal Shutdown Protection
The MAX14544 has an autoretry feature, whereas the
MAX14545 has a latchoff feature. When the switch is off,
OUT can withstand 28V maximum. When the switch is on
and a load is connected to the port, a blanking time of
10.5ms ensures that the transient voltage settles down.
After this blanking time, if the voltage across the switch is
greater than the FLAG assertion voltage, the switch turns
off and then a FLAG is issued to the microprocessor.
After the retry time, the device recloses for the duration
of the blanking time to check if the load current is lower
than the limit. The MAX14544 repeats this cycle if the
overload condition is present. During the cycle, FLAG
remains asserted. The MAX14544 remains on after the
overload condition is removed and FLAG deasserts. For
the MAX14545, after the blanking time, the switch turns
off and then a FLAG is issued to the microprocessor. The
switch can be turned on again by cycling the power or
the EN input.
S 0.1µA (typ) Shutdown Current
S 5µs Fast Current-Limit Detect
S 8-Pin TDFN (2mm x 2mm) Package
S -40NC to +85NC Operating Temperature Range
Ordering Information/
Selector Guide
PIN-
PACKAGE
TOP
RETRY/
PART
MARK LATCHOFF
MAX14544ETA+T
MAX14545ETA+T
8 TDFN-EP*
8 TDFN-EP*
ACY
ACZ
Autoretry
Latchoff
Note: All devices are specified over the -40°C to +85°C tem-
perature range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
T = Tape and reel.
*EP = Exposed pad.
The MAX14544/MAX14545 have additional safety fea-
tures that include thermal shutdown protection, reverse-
current blocking, and overvoltage protection.
Pin Configuration
The MAX14544/MAX14545 are offered in a space-sav-
ing, 8-pin, 2mm x 2mm TDFN package, and operate over
the -40NC to +85NC extended temperature range.
TOP VIEW
+
Applications
IN
IN
1
2
3
4
8
7
6
5
OUT
OUT
EN
Cell Phones
MP3 Players
PDAs
MAX14544
MAX14545
ISET
GND
Digital Cameras
eBook
*EP
FLAG
MID
TDFN
Typical Operating Circuit appears at end of data sheet.
*CONNECT EXPOSED PAD TO GND.
_______________________________________________________________ Maxim Integrated Products
1
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.
28V-Capable, I V
Accessory Switch
LIM BUS
ABSOLUTE MAXIMUM RATINGS
(Voltages referenced to GND.)
Junction-to-Case Thermal Resistance
OUT .......................................................................-0.3V to +30V
IN, FLAG, EN, ISET ..............................................-0.3V to +6.0V
B
(Note 1) .................................................................37NC/W
JC
Operating Temperature Range.......................... -40NC to +85NC
Storage Temperature Range............................ -65NC to +150NC
Junction Temperature ..................................... -40NC to +150NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
Continuous Power Dissipation (T = +70NC)
A
8-Pin TDFN (derate 11.9mW/NC above +70NC)...........953mW
Junction-to-Ambient Thermal Resistance
B
(Note 1) ..............................................................83.9NC/W
JA
Note 1: Package thermal resistances were obtained using the method described in JEDEC specifications. For detailed information
on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial.
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
(V = +2.3V to +5.5V, T = -40NC to +85NC, unless otherwise noted. Typical values are at V = +3.3V, T = +25NC.) (Note 2)
IN
A
IN
A
PARAMETER
SYMBOL
CONDITIONS
MIN
2.3
TYP
MAX
5.5
UNITS
Operating Voltage Range
Undervoltage Lockout
V
V
V
IN
V
V
falling
rising
1.8
2.2
UVLO
IN
Undervoltage Lockout Hysteresis
100
mV
IN Overvoltage Trip Level
IN Overvoltage Hysteresis
Quiescent Current
V
OVLO
V
V
5.5
6.0
V
%
FA
V
IN
1
I
Q
= V = 3.3V, I = 0A
OUT
225
380
28
EN
IN
OUT Voltage
V
Switch off
OUT
V
= V = 5V, V
= 5V after an overcur-
= 10V after an overcur-
EN
IN
OUT
OUT
0.2
1
rent fault
OUT Leakage Current
I
FA
OUTL
V
EN
= V = 5V, V
IN
3.5
rent fault
V
V
= 0V, V = 5V, V
= 0V, V = 0V
ISET
0.1
0.1
1.1
1.1
EN
IN
OUT
IN Shutdown Current
Switch On-Resistance
Current Limit
I
FA
mI
mA
V
SHDN
= 0V, V = 5V, V
= 10V, V
= 0V
EN
IN
OUT
ISET
I
I
= 100mA, V = 2.3V
370
270
250
500
600
450
300
600
OUT
OUT
IN
R
ON
= 100mA, V > 3.3V
IN
V
ISET
V
ISET
V
= 0V, V - V = 1V
OUT
200
400
IN
I
LIM
= V , V - V
= 1V
IN IN
OUT
= V - V , where overcurrent is
OUT
FA
IN
V
FA
0.30
0
0.45
155
0.60
350
FLAG Assertion Voltage
detected and FLAG asserted
V = V = 3.3V, V rising until reverse-
EN
current shutdown protection trips
Reverse-Current Detection
Threshold
IN
OUT
I
mA
DET
After a reverse overcurrent event, V
falls
OUT
Reverse-Current Detection
Hysteresis
below V until switch turns on, measure
100
200
300
mV
IN
V
- V
OUT
IN
2
28V-Capable, I V
Accessory Switch
LIM BUS
ELECTRICAL CHARACTERISTICS (continued)
(V = +2.3V to +5.5V, T = -40NC to +85NC, unless otherwise noted. Typical values are at V = +3.3V, T = +25NC.) (Note 2)
IN
A
IN
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
Input Logic-High Voltage
Input Logic-Low Voltage
Input Leakage
V
1.4
IH
V
0.4
+1
0.4
1
V
IL
IN
I
V
= V
= 0V or 5V
-1
FA
V
EN
ISET
Output Logic-Low Voltage
Output High Leakage Current
Thermal Shutdown
V
OL
I
= 1mA
SINK
FA
NC
NC
V
V
V
= 5V
FLAG
= 5V
150
15
IN
IN
Thermal Shutdown Hysteresis
= 5V
TIMING CHARACTERISTICS (Note 3)
Turn-On Time
Turn-Off Time
t
V
V
from low to high, V = 3.3V, R = 100I
0.3
ms
ms
ON
EN
IN
L
t
from high to low, V = 3.3V, R = 100I
1
5
OFF
EN
IN
L
V
EN
= V = 3.3V, output high and then short
IN
Current-Limit Reaction Time
t
circuit applied, C = 10FF ceramic,
Fs
LIM
IN
C UT = 1µF ceramic
O
Blanking Time
Autoretry Time
t
V
= V = 3.3V, Figures 1 and 2
4
10.5
30
ms
ms
BLANK
EN
IN
t
MAX14544, Figure 1
252
661.5
1890
RETRY
V
= 3.3V, I
= 250mA, C = 10FF
IN
= 1FF ceramic
IN
REVERSE
Reverse-Current Detection Time
Reverse-Current Recovery Time
t
5
Fs
DET
ceramic, C
OUT
V
OUT
V
= V + 500mV to
IN
t
0.1
ms
REC
= V - 500mV
OUT
IN
Note 2: All devices are production tested at T = +25NC. Specifications over temperature limits are guaranteed by design.
A
Note 3: All timing characteristics are measured using 20% and 80% levels.
3
28V-Capable, I V
Accessory Switch
LIM BUS
t
t
t
t
t
t
BLANK
BLANK
BLANK
RETRY
BLANK
RETRY
CURRENT LIMIT
LOAD CURRENT
ON
SWITCH
OFF
FLAG
ON
EN
OFF
Figure 1. MAX14544 Timing Diagram (Waveforms Not to Scale)
t
t
BLANK
BLANK
CURRENT LIMIT
LOAD CURRENT
ON
SWITCH
OFF
FLAG
ON
EN
OFF
Figure 2. MAX14545 Timing Diagram (Waveforms Not to Scale)
4
28V-Capable, I V
Accessory Switch
LIM BUS
Typical Operating Characteristics
(V = +3.3V, C = 10FF, C
= 1FF, T = +25NC, unless otherwise noted.)
A
IN
IN
OUT
QUIESCENT SUPPLY CURRENT
vs. SUPPLY VOLTAGE
QUIESCENT SUPPLY CURRENT
vs. TEMPERATURE
NORMALIZED CURRENT LIMIT
vs. SUPPLY VOLTAGE
450
450
400
350
300
250
200
150
100
50
1.05
1.04
1.03
1.02
1.01
1.00
0.99
0.98
0.97
0.96
0.95
V
= V
V
V
I
= V
EN IN
EN
IN
400
350
300
250
200
150
100
50
V
= 5V
IN
V
= 3.3V
IN
0
0
2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
-40
-15
10
35
60
85
2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
NORMALIZED CURRENT LIMIT
vs. TEMPERATURE
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
SHUTDOWN FORWARD CURRENT
vs. TEMPERATURE
1.05
1.04
1.03
1.02
1.01
1.00
0.99
0.98
0.97
0.96
0.95
900
800
700
600
500
400
300
200
100
0
900
800
700
600
500
400
300
200
100
0
= 5V
V
= 0V
OUT
OUT
V
= 5V
V = 5V
IN
IN
V
= 2.3V
60
V
IN
= 2.3V
60
IN
-40
-15
10
35
60
85
-40
-15
10
35
85
-40
-15
10
35
85
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
SHUTDOWN REVERSE CURRENT
vs. TEMPERATURE
NORMALIZED ON-RESISTANCE
vs. SUPPLY VOLTAGE
NORMALIZED ON-RESISTANCE
vs. TEMPERATURE
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
1000
950
900
850
800
750
700
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
V
V
= 2.3V
I
= 100mA
= 100mA
IN
OUT
OUT
= 5V
OUT
-40
-15
10
35
60
85
-40
-15
10
35
60
85
2.3 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
5
28V-Capable, I V
Accessory Switch
LIM BUS
Typical Operating Characteristics (continued)
(V = +3.3V, C = 10FF, C
= 1FF, T = +25NC, unless otherwise noted.)
IN
IN
OUT
A
SWITCH TURN-ON TIME
vs. TEMPERATURE
SWITCH TURN-OFF TIME
vs. TEMPERATURE
POWER-UP RESPONSE
MAX14544/5 toc12
95
94
93
92
91
90
89
88
87
86
85
1000
990
980
970
960
950
940
930
920
V
= 5V
IN
L
V
= 5V
IN
L
R = 100Ω
R = 100Ω
V
IN
5V/div
V
OUT
5V/div
I
OUT
50mA/div
-40
-15
10
35
60
85
200µs/div
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
FLAG RESPONSE
REVERSE OVERVOLTAGE PROTECTION
CURRENT LIMIT RESPONSE
MAX14544/5 toc14
MAX14544/5 toc13
MAX14544/5 toc15
V
= 5V
IN
ISET HIGH
V
= 0V
EN
R = 100Ω
L
ISET HIGH
10V
5V
I
OUT
I
OUT
200mA/div
V
OUT
200mA/div
2V/div
V
OUT
V
OUT
2V/div
5V/div
0V
V
IN
2V/div
3.3V
V
FLAG
V
FLAG
2V/div
5V/div
0V
100ms/div
10µs/div
20ms/div
CURRENT LIMIT RESPONSE
OVERCURRENT DURATION TIME
BLANKING TIME
MAX14544/5 toc16
MAX14544/5 toc17
MAX14544/5 toc18
ISET HIGH
MAX14544 ISET HIGH
MAX14544 ISET HIGH
I
I
I
OUT
OUT
OUT
200mA/div
200mA/div
200mA/div
V
V
OUT
OUT
2V/div
2V/div
V
OUT
2V/div
V
V
FLAG
FLAG
2V/div
2V/div
V
FLAG
2V/div
100ms/div
200ms/div
10ms/div
6
28V-Capable, I V
Accessory Switch
LIM BUS
Pin Description
PIN
NAME
FUNCTION
Input Voltage. Connect IN pins 1 and 2 together and bypass IN to GND with a 10FF ceramic capacitor as
close to the device as possible.
1, 2
IN
Current-Limit Setting. Drive ISET low to have a 200mA current limit. Drive ISET high to have a 400mA cur-
rent limit.
3
4
ISET
GND
Ground
Active-Low Fault Open-Drain Output. FLAG goes low when the forward output current is exceeded for
longer than the blanking time, the reverse current limit is exceeded, the OVP threshold on IN is reached,
or the part goes into thermal shutdown. FLAG is high impedance when EN is low or a fault is not present.
5
FLAG
6
EN
Active-High Switch-Enable Input. Drive EN high to turn on the device. Drive EN low to turn off the device.
Output Voltage. Connect OUT pins 7 and 8 together and bypass OUT to GND with a 1FF ceramic capaci-
tor as close to the device as possible.
7, 8
OUT
Exposed Pad. Connect EP to GND. For enhanced thermal dissipation, connect EP to a large copper
ground plane. Do not use EP as the sole ground connection.
—
EP
Functional Diagram
IN
OUT
CHARGE PUMP
REVERSE
CURRENT
FORWARD CURRENT
UVLO
CONTROL
MAX14544
MAX14545
OVLO
EN
ISET
FLAG
GND
7
28V-Capable, I V
Accessory Switch
LIM BUS
FLAG is an open-drain output and requires an external
pullup resistor. During shutdown (EN is low), the pull-
down on FLAG output is released to limit power dissipa-
tion. FLAG goes low when one of the following occurs:
Detailed Description
The MAX14544/MAX14545 are overcurrent detection
switches that prevent host devices from being damaged
due to faulty load conditions. The switch opens if current
exceeds the current limit for longer than the blanking
time or if a reverse-current condition is detected. The
switch also disconnects if V exceeds OVLO, V falls
1) The temperature exceeds the thermal shutdown tem-
perature, +150NC (typ).
2) The device is in current limit for more than the fault
blanking period.
IN
IN
below UVLO, thermal shutdown occurs, or EN is driven
low. Current limit can be set to either 200mA or 400mA.
When the switch is open, the output (OUT) can withstand
28V maximum.
3) The switch is in autoretry.
4) The reverse current limit is exceeded.
5) The input is over the OVLO.
When the switch is on and a load is connected to the
port, a blanking time of 10.5ms ensures that the inrush
current settles down. After this blanking time, if the volt-
age across the switch is greater than the FLAG asser-
tion voltage, the part is turned off and issues a FLAG
to the microprocessor. After the retry time elapses, the
MAX14544 switch is closed for the duration of the blank-
ing time to check if the load current is lower than the
limit. Cycle the power or EN input to turn the MAX14545
switch back on.
Autoretry (MAX14544)
When the FLAG assertion voltage is exceeded, the
t
timer begins counting (Figure 1). The timer resets
BLANK
if the condition disappears before t
has elapsed.
BLANK
A retry time delay (t ) is started immediately after
RETRY
t
has elapsed and during that time the switch is
BLANK
turned off and FLAG is asserted. At the end of t
,
RETRY
the device is turned on again. If the fault still exists, the
cycle is repeated. If the fault is removed, the device
stays on and FLAG deasserts.
Current-Limit Threshold
The autoretry feature saves system power in the case
of a continuous overcurrent or short-circuit condition.
The MAX14544/MAX14545 ISET logic input sets the
desired minimum current-limit threshold to 200mA or
400mA. Connect ISET low for a 200mA current limit and
high for a 400mA current limit. If 400mA is selected as
the current limit, the input supply current at shutdown
can be reduced by connecting ISET to EN. This is due
to the fact that the device consumes the lower supply
current in ISET = low mode than in ISET = high mode.
During t , when the switch is on, the supply current
BLANK
is at the current limit. During t
, when the switch
RETRY
is off, the current through the switch is zero. Instead
of observing the full load current, the device sees the
equivalent load current times duty cycle or:
I
= I
x t
/(t
+ t
)
SUPPLY
LOAD
BLANK BLANK
RETRY
With a typical t
661.5ms, the duty cycle is 1.6%, resulting in a 98.4%
power savings over the switch being on the entire time.
= 10.5ms and typical t
=
RETRY
Reverse-Current Protection
BLANK
The MAX14544/MAX14545 monitor the reverse current
(V
OUT
to V ) from exceeding the maximum I
value.
IN
DET
If the reverse-current detection threshold is exceeded,
the switch turns off and FLAG is asserted without waiting
Latchoff (MAX14545)
When the FLAG assertion voltage is exceeded, the
for t
to elapse. This feature prevents excessive
BLANK
t
timer begins counting. The device turns off after
BLANK
reverse currents from flowing through the device.
the blanking time. The timer resets if the condition is
removed before the end of the blanking time. Reset the
device by toggling EN (Figure 2).
FLAG Indicator
The MAX14544/MAX14545 feature a fault output (FLAG).
Whenever V - V > V , the MAX14544 asserts
IN
OUT
FA
Fault Blanking
The MAX14544/MAX14545 feature a 10.5ms (typ) fault
blanking. Fault blanking allows current-limit faults,
including momentary short-circuit faults that occur when
plugging a capacitive load, and also ensures that no
fault is issued during power-up. When a load transient
causes the device to enter current limit, an internal coun-
ter starts. If the load-transient fault persists beyond the
FLAG low after the blanking time and keeps it low until
the condition is removed. During this time, the switch
cycles on and off in the autoretry mode. When the condi-
tion is removed, FLAG deasserts and the switch turns
on (Figure 1). The MAX14545 asserts FLAG low after the
blanking time and turns the switch off when FLAG asser-
tion voltage is exceeded (Figure 2).
8
28V-Capable, I V
Accessory Switch
LIM BUS
fault-blanking timeout, FLAG asserts low. FLAG is not
asserted when load-transient fault is less than t
The fault blanking time only applies to forward current-
limit faults.
the MAX14544/MAX14545 from tripping erroneously. If
the load capacitance is too large, then current may not
have enough time to charge the capacitance and the
device assumes that there is faulty load condition. The
maximum capacitive load value that can be driven from
OUT is obtained by the following formula:
.
BLANK
A reverse current-limit fault, thermal fault, or OVP fault
causes FLAG to assert immediately and does not wait
for the blanking time.
I
× t
FWD_MIN BLANK_MIN
C
<
MAX
V
Thermal Shutdown
The MAX14544/MAX14545 have a thermal-shutdown
feature to protect the devices from overheating. The
device turns off and FLAG goes low immediately (no
fault blanking) when the junction temperature exceeds
+150NC. The MAX14544/MAX14545 turns back on when
the device temperature drops approximately 15NC.
IN
Layout and Thermal Dissipation
To optimize the switch response time to output short-
circuit conditions, it is very important to keep all traces
as short as possible to reduce the effect of undesirable
parasitic inductance. Place input and output capacitors
as close as possible to the device. IN and OUT must be
connected with short traces to the power bus.
OVLO and UVLO
The MAX14544/MAX14545 feature an overvoltage pro-
During normal operation, the power dissipation is small
and the package temperature change is minimal. If the
output is continuously shorted to ground at the maximum
supply voltage, the operation of the switches with the
autoretry option does not cause problems because the
total power dissipated during the short is scaled by the
duty cycle:
tection. When IN goes above V
switch turns off and FLAG goes low immediately with
no fault-blanking time. When IN drops below V
(1.8V min), the switch turns off but FLAG stays high. The
MAX14544/MAX14545 turns back on when IN is in the
operating range.
(6.0V max), the
OVLO
UVLO
Applications Information
V
×I
× t
IN_MAX OUT_MAX
BLANK
P
=
= 51.6mW
Input Capacitor
To limit the input-voltage drop during momentary output
short-circuit conditions, connect a capacitor from IN to
GND. A 10FF ceramic capacitor is adequate for most
applications; however, higher capacitor values further
reduce the voltage drop at the input and are recom-
mended for lower voltage applications.
MAX
t
+ t
BLANK
RETRY
where V
= 5.5V, I
= 600mA, t
=
IN_MAX
10.5ms, and t
OUT_MAX
BLANK
= 661.5ms.
RETRY
Attention must be given to the MAX14545 where the
latchoff condition can be manually reset by toggling EN
from high to low. If the latchoff time duration is not suf-
ficiently high, it is possible for the device to reach the
thermal-shutdown threshold and never be able to turn
the device on until it cools down.
Output Capacitor
Connect a 1FF ceramic capacitor from OUT to GND.
This capacitor helps prevent inductive parasitics from
pulling OUT negative during turn-off, thus preventing
9
Typical Operating Circuit
CURRENT
CHARGER
POWER
SOURCE
Li+ BATTERY CHARGER
VBUS
D+
MINI-B
USB
JACK
BATT
OR
D-
V
CC
IN
IN
OUT
OUT
GND
PERIPHERAL
DEVICE
MAX14544
MAX14545
10kI
CURRENT
V
FLAG
EN
CC
µC
NOTE: DRIVE ISET HIGH TO HAVE A 400mA CURRENT LIMIT.
DRIVE ISET LOW TO HAVE A 200mA CURRENT LIMIT.
ISET
GND
PACKAGE TYPE PACKAGE CODE DOCUMENT NO.
8 TDFN-EP
T822+2
21-0168
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