MAX34561T+ [MAXIM]
12V/5V Hot-Plug Switch; 12V / 5V热插拔开关
| 型号： | MAX34561T+ |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 12V/5V Hot-Plug Switch |
| 文件： | 总11页 (文件大小：1236K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-5621; Rev 0; 11/10
12V/5V Hot-Plug Switch
General Description
Features
S Completely Integrated Hot-Plug Functionality for
The MAX34561 is a dual, self-contained, hot-plug switch
intended to be used on +12V and +5V power rails to limit
through current and to control the power-up output-volt-
age ramp. The device contains two on-board n-channel
power MOSFETs that are actively closed-loop controlled
to ensure that an adjustable current limit is not exceed-
ed. The maximum allowable current through the device
is adjusted by external resistors connected between the
LOAD and ILIM pins.
+12V and +5V Power Rails
S Dual Version of the DS4560
S On-Board Power MOSFETs (68mI and 43mI)
S No High-Power R
SENSE
Resistors Needed
S Adjustable Current Limits
S Adjustable Output-Voltage Slew Rates
S Adjustable Power-Up Enable Timing
S Output Overvoltage Limiting
S On-Board Thermal Protection
S On-Board Charge Pump
The device can control the power-up output-voltage
ramp. Capacitors connected to the VRAMP pins set
the desired voltage-ramp rate. The output voltages
are unconditionally clamped to keep input overvoltage
stresses from harming the load. The device also contains
adjustable power-up timers. Capacitors connected to
the TIMER pins determine how long after power-on reset
(POR) the device should wait before starting to apply
power to the loads. The TIMER pins can be driven with
a digital logic output to create a device-enable function.
S User-Selectable Latchoff or Automatic Retry
Operation
Ordering Information
PART
TEMP RANGE
-40NC to +85NC
-40NC to +85NC
PIN-PACKAGE
24 TQFN-EP*
24 TQFN-EP*
The device contains an on-board temperature sensor
with hysteresis. If operating conditions cause the device
to exceed an internal thermal limit, the device either
unconditionally shuts down and latches off awaiting a
POR, or waits until the device has cooled by the hyster-
esis amount and then restarts.
MAX34561T+
MAX34561T+T
+Denotes a lead(Pb)-free/RoHS compliant package.
T = Tape and reel.
*EP = Exposed pad.
Applications
RAID/Hard Drives
Servers/Routers
M
PCI/PCI Express
InfiniBandTM/SM
Base Stations
PCI Express is a registered trademark of PCI-SIG Corp.
InfiniBand is a trademark and service mark of InfiniBand Trade
Association.
_______________________________________________________________ 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.
12V/5V Hot-Plug Switch
ABSOLUTE MAXIMUM RATINGS
Voltage Range on V
Voltage Range on V
Relative to GND............-0.3V to +6.5V
12V Drain Current
Continuous ............................................................................2A
Peak ......................................................................................4A
CC5
CC12
Relative to GND...........-0.3V to +18V
Voltage Range on ILIM5, VRAMP5,
TIMER5, ARD5 Relative to GND.........-0.3V to (V
+ 0.3V),
Continuous Power Dissipation (T = +70NC)
CC5
A
not to exceed +6.5V
TQFN (derate 20.8mW/NC above +70NC)...............1666.7mW
Operating Junction Temperature Range ......... -40NC to +135NC
Operating Temperature Range.......................... -40NC to +85NC
Storage Temperature Range .......................... -55NC to +135NC
Lead Temperature (soldering, 10s) ................................+300NC
Soldering Temperature (reflow) ......................................+260NC
Voltage Range on ILIM12, VRAMP12
Relative to GND ................................-0.3V to (V
+ 0.3V),
CC12
not to exceed +18V
Voltage Range on TIMER12, ARD12
Relative to GND .......................................-0.3V to +5V (V
)
REG
5V Drain Current
Continuous ............................................................................2A
Peak ......................................................................................4A
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.
RECOMMENDED OPERATING CONDITIONS
(T = -40NC to +135NC)
J
PARAMETER
SYMBOL
CONDITIONS
MIN
4.0
9
TYP
5.0
12
MAX
5.5
13.2
400
5
UNITS
V
V
Voltage
V
(Notes 1, 2)
(Notes 1, 2)
V
V
CC5
CC5
Voltage
Value
V
CC12
CC12
R
R
ILIM_
20
I
ILIM_
C
C
Value
Value
C
0.04
0.04
2.1
2.6
-0.3
FF
FF
VRAMP_
TIMER_
VRAMP_
C
5
TIMER_
TIMER5
V
+ 0.3
5.0
CC5
TIMER_ Turn-On Voltage
TIMER_ Turn-Off Voltage
V
ON
V
V
TIMER12
V
OFF
+1.5
ELECTRICAL CHARACTERISTICS
(V
CC5
= +5V, V = +12V, T = +25NC, unless otherwise noted.)
CC12 J
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
1.5
1.5
3.7
3.2
0.5
8
MAX
2
UNITS
mA
mA
V
V
V
Supply Current
I
(Note 3)
(Note 3)
CC5
CC5
Supply Current
I
2.25
3.95
CC12
CC12
5V UVLO: Rising
V
UR5
5V UVLO: Falling
V
2.7
6.5
V
UF5
UH5
5V UVLO: Hysteresis
12V UVLO: Rising
V
V
V
8.5
V
UR12
12V UVLO: Falling
12V UVLO: Hysteresis
5V On-Resistance
V
7
V
UF12
UH12
V
R
1
V
R
43
56
88
mI
mI
V
ON5
12V On-Resistance
5V Internal Voltage Reference
68
ON12
V
REF5
1.80
2.35
12V Internal Voltage Reference
V
V
REF12
2
12V/5V Hot-Plug Switch
ELECTRICAL CHARACTERISTICS (continued)
(V
CC5
= +5V, V = +12V, T = +25NC, unless otherwise noted.)
CC12 J
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
5V MOSFET Output Capacitance
C
(Note 4)
(Note 4)
400
pF
OUT
12V MOSFET Output
Capacitance
C
OUT
400
8
pF
ms
ms
5V and 12V Delay Time from
Enable to Beginning of
Conduction
t
C
C
= 1FF
POND
VRAMP_
5V and 12V Gate-Charging Time
t
= 1FF, C
= 1000FF
48
64
80
GCT
VRAMP_
LOAD_
from Conduction to 90% of V
OUT
Shutdown Junction Temperature
Thermal Hysteresis
T
(Note 4)
(Note 4)
120
135
40
150
NC
NC
FA
FA
V
SHDN
T
HYS
TIMER_ Charging Current
VRAMP_ Charging Current
5V Overvoltage Clamp
I
64
64
80
96
96
TIMER
I
80
VRAMP
V
5.5
13.2
6.0
15
6.5
16.5
OVC5
12V Overvoltage Clamp
V
V
OVC12
5V Power-On Short-Circuit
Current Limit
I
R
R
R
R
= 47I (Note 5)
0.6
0.6
1.0
1.0
2.5
1.8
1.5
1.5
3.7
2.6
A
A
A
A
SCL5
ILIM5
12V Power-On Short-Circuit
Current Limit
I
= 47I (Note 5)
SCL12
ILIM12
5V Operating Overload Current
Limit
I
= 47I (Notes 4, 6)
1.5
OVL5
ILIM5
12V Operating Overload Current
Limit
I
= 47I (Notes 4, 6)
1.00
OVL12
ILIM12
5V VRAMP5 Slew Rate
12V VRAMP12 Slew Rate
ARD5 Pullup Resistor
ARD12 Pullup Resistor
SR
C
C
= 1FF
0.16
0.13
0.19
0.15
0.23
0.18
V/ms
V/ms
kI
VRAMP
VRAMP5
SR
= 1FF
VRAMP
VRAMP12
R
PU5
100
R
kI
PU12
Note 1: All voltages are referenced to ground. Currents entering the device are specified positive, and currents exiting the device
are negative.
Note 2: This supply range guarantees that the LOAD_ voltage is not clamped by the overvoltage limit.
Note 3: Supply current specified with no load on the LOAD_ pin.
Note 4: Guaranteed by design; not production tested.
Note 5: I
Note 6: I
is the current limit when conduction begins.
is the current limit after the on-board MOSFET is fully on.
SCL_
OVL_
3
12V/5V Hot-Plug Switch
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
5V CURRENT LIMIT vs. ILIM RESISTANCE
12V CURRENT LIMIT vs. ILIM RESISTANCE
SUPPLY CURRENT vs. TEMPERATURE
2.6
2.4
2.2
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
2.5
2.0
1.5
1.0
0.5
0
1.8
1.6
1.4
I
I
OVL12
OVL5
12V OPERATION
5V OPERATION
1.2
1.0
0.8
0.6
0.4
0.2
0
I
SCL5
I
SCL12
0
50
100
150
0
50
100
150
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
R
ILIM
(Ω)
R
ILIM
(Ω)
CURRENT LIMIT vs. TEMPERATURE
CURRENT LIMIT vs. TEMPERATURE
OVERVOLTAGE CLAMP vs. TEMPERATURE
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
2.5
2.0
1.5
1.0
0.5
0
6.55
6.50
6.45
6.40
6.35
6.30
6.25
6.20
6.15
6.10
6.05
5V OPERATION
12V OPERATION
NO LOAD
5V OPERATION
NOTE: 6.5V = V ABSOLUTE
I
CC
OVL5
I
OVL12
MAXIMUM VALUE
20Ω LOAD
I
SCL12
I
SCL5
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
OVERVOLTAGE CLAMP vs. TEMPERATURE
ON-RESISTANCE vs. TEMPERATURE
16.2
16.0
15.8
15.6
15.4
15.2
15.0
14.8
70
12V OPERATION
60
50
40
30
20
10
0
12V OPERATION
NO LOAD
5V OPERATION
20Ω LOAD
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
-40 -20
0
20 40 60 80 100 120
TEMPERATURE (°C)
4
12V/5V Hot-Plug Switch
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
TYPICAL MAX34561 TURN-ON WAVEFORMS
TYPICAL MAX34561 TURN-ON WAVEFORMS
TURN-ON WAVEFORMS
V
= 5V, 20Ω RESISTIVE LOAD
V
= 12V, 20Ω RESISTIVE LOAD
V = 5V, 20Ω RESISTIVE LOAD
CC
CC
CC
MAX34561 toc09
MAX34561 toc10
MAX34561 toc11
V
V
V
CC5
CC5
CC12
LOAD5
TIMER5
LOAD12
2V/div
LOAD5
VRAMP12
VRAMP5
LOAD CURRENT
TIMER12
500mA/div
2ms/div
5ms/div
5ms/div
TURN-ON WAVEFORMS
TURN-ON WAVEFORMS
= 5V, 3300µF CAPACITIVE LOAD
TURN-ON WAVEFORMS
= 12V, 3300µF CAPACITIVE LOAD
MAX34561 toc14
V
= 12V, 20Ω RESISTIVE LOAD
V
V
CC
CC
CC
MAX34561 toc12
MAX34561 toc13
V
CC12
V
CC5
V
CC12
LOAD5
LOAD12
LOAD12
5V/div
5V/div
2V/div
LOAD CURRENT
LOAD CURRENT
LOAD CURRENT
500mA/div
500mA/div
500mA/div
5ms/div
5ms/div
10ms/div
THERMAL SHUTDOWN WITH AUTORETRY ENABLED
= 5V, 2Ω RESISTIVE LOAD
THERMAL SHUTDOWN WITH AUTORETRY ENABLED
= 12V, 2Ω RESISTIVE LOAD
V
CC
V
CC
MAX34561 toc15
MAX34561 toc16
V
CC12
V
CC5
LOAD12
5V/div
2V/div
LOAD5
LOAD CURRENT
LOAD CURRENT
500mA/div
500mA/div
1s/div
500ms/div
5
12V/5V Hot-Plug Switch
Pin Configuration
TOP VIEW
18
17
16
15
14
13
12
11
10
9
TIMER12 19
VRAMP12 20
ARD12 21
LOAD12
ILIM12
GND
MAX34561
ARD5 22
DNC
VRAMP5
TIMER5
ILIM5
LOAD5
23
24
8
EP
+
7
1
2
3
4
5
6
THIN QFN
(4mm × 4mm)
Pin Description
PIN
1, 2, 3
4–7
NAME
FUNCTION
5V Supply Input. Power-supply input and n-channel power MOSFET drain connection. If the 5V side
is not used, connect this pin to GND.
V
CC5
LOAD5
ILIM5
5V Load Output. n-channel power MOSFET source connection.
5V Supply Current-Limit Adjust. A resistor from this pin to LOAD5 determines the current limit for
the 5V pass connection. For better accuracy, dedicate one LOAD pin to connect to ILIM through
8
R
ILIM
. See the Applications Information section for more information.
9
DNC
GND
Do Not Connect. Do not connect any signal to this pin.
Ground Connection
10
12V Supply Current-Limit Adjust. A resistor from this pin to LOAD12 determines the current limit for
the 12V pass connection. For better accuracy, dedicate one LOAD pin to connect to ILIM through
11
ILIM12
R
. See the Applications Information section for more information.
ILIM
12–15
LOAD12
12V Load Output. n-channel power MOSFET source connection.
12V Supply Input. Power-supply input and n-channel power MOSFET drain connection. If the 12V
side is not used, connect this pin to GND.
16, 17, 18
V
CC12
12V Enable Delay Control. A capacitor connected to this pin determines the enable delay accord-
19
20
TIMER12
ing to the equation: Enable Delay = C
x (V
/I
).
TIMER12
REF12 TIMER
12V Voltage Ramp Control. A capacitor connected to this pin determines the voltage ramp of the
LOAD12 output during turn-on according to the equation: dV = 2 x (I /C ).
VRAMP12
LOAD12
VRAMP VRAMP12
12V Autoretry Disable. Connect this pin to GND to disable automatic retry functionality; the device
latches off during an overtemperature fault. Leave this pin open to enable automatic retry function.
21
ARD12
This pin contains a pullup (R ) to 5V. This pin is only sampled on device power-on. If the 12V
PU12
side is not used, connect this pin to GND.
6
12V/5V Hot-Plug Switch
Pin Description (continued)
PIN
NAME
FUNCTION
5V Autoretry Disable. Connect this pin to GND to disable automatic retry functionality; the device
latches off during an overtemperature fault. Leave this pin open to enable automatic retry function.
22
ARD5
This pin contains a pullup (R ) to V . This pin is only sampled on device power-on. If the 5V
PU5 CC5
side is not used, connect this pin to GND.
5V Voltage Ramp Control. A capacitor connected to this pin determines the voltage ramp of the
23
24
—
VRAMP5
TIMER5
EP
LOAD5 output during turn-on according to the equation: dV = 2.3332 x (I /C
).
LOAD5
VRAMP VRAMP5
5V Enable Delay Control. A capacitor connected to this pin determines the enable delay according
to the equation: Enable Delay = C x (V /I ).
TIMER5
REF5 TIMER
Exposed Pad. Connect to ground. The EP must be soldered to ground for proper thermal and elec-
trical operation.
When the output power is initially ramping up, the current
Detailed Description
limit is I
(I
). Once the corresponding MOSFET
SCL12 SCL5
The MAX34561 has hot-plug controls for both +12V and
+5V power rails. The circuitry for the +12V and +5V con-
trols are independent of each other and can be treated
as two separate hot-plug switches, even though the GND
pin is common between the two switches. The sections
that follow are written from the +12V circuit perspective,
but also apply for the +5V switch control.
is fully on, the current limit is I
(I
). The I
OVL12 OVL5 SCL12
(I ) current limit protects the source if there is a dead
SCL5
short on initial power-up.
The device acts as a fuse and automatically disables the
current flowing to the load when the temperature of the
power corresponding MOSFET has exceeded the shut-
down junction temperature, T
.
SHDN
The device begins to operate when the supply voltage
Enable/Timer
The voltage level of TIMER12 (TIMER5) is compared to
V
V
(or V
(or V
) exceeds its undervoltage lockout level,
). At this level, the corresponding enable
CC12
UR12
CC5
UR5
an internal source (see the Functional Diagram). When
circuit and TIMER12 (TIMER5) become active. Once the
device has been enabled, a gate voltage is applied to
the corresponding power MOSFET, allowing current to
the level on the pin exceeds V , the comparator out-
ON
puts a low level. This then turns on the voltage ramp
circuit, enabling the device’s output. TIMER12 (TIMER5)
can be configured into one of four different modes of
operation as listed in Table 1. TIMER12 (TIMER5) pin
was designed to work with most logic families. TIMER12
begin flowing from V
(V
) to LOAD12 (LOAD5).
CC12 CC5
The speed of the output-voltage ramp is controlled by
the capacitance placed at the VRAMP12 (VRAMP5) pin.
The load current is continuously monitored during the
(TIMER5) has at least 250mV of hysteresis between V
initial conduction (I
or I
) and after the cor-
SCL5
ON
SCL12
and V
. It is recommended that any logic gate used
responding MOSFET is fully on (I
or I
). If the
OVL5
OFF
OVL12
to drive TIMER12 (TIMER5) be tested to ensure proper
operation.
current exceeds the current limit that is set by the exter-
nal resistance at ILIM12 (ILIM5), the gate voltage of the
corresponding power MOSFET is decreased, reducing
the output current to the set current limit.
Table 1. TIMER_ Pin Modes
Current is limited by the device comparing the volt-
age difference between LOAD12 (LOAD5) and ILIM12
(ILIM5) to an internal reference voltage. If the output cur-
OPERATION MODE
TIMER PIN SETUP
No connection to TIMER12
(TIMER5)
Automatic Enable
rent exceeds the limit that is set by the R
(R
)
ILIM12 ILIM5
Capacitor C
connected
TIMER_
resistor, the gate voltage of the corresponding power
MOSFET is decreased, which reduces the output current
to the load.
Delayed Automatic Enable
Enable/Disable
to TIMER12 (TIMER5)
Open-collector device
Open-collector device and
Enable with Delay/Disable
C
_
TIMER
7
12V/5V Hot-Plug Switch
Functional Diagram
12V
UVLO
V
CC12
+5V
V
REG
R
ON12
LOAD12
ILIM12
LOAD
CHARGE
PUMP
R
ILIM12
CURRENT
LIMIT
V
CC12
R
R
I
VRAMP
+5V
V
REG
12V
THERMAL
LIMIT
VRAMP12
I
TIMER
OVERVOLTAGE
LIMIT
C
VRAMP12
GND
V
REF12
+5V
TIMER12
V
REG
EXTERNAL
DISABLE
C
TIMER12
R
PU12
5V
12V
ARD12
AUTORETRY
DISABLE
MAX34561
V
CC5
UVLO
R
ON5
LOAD5
ILIM5
LOAD
CHARGE
PUMP
R
ILIM5
CURRENT
LIMIT
V
CC5
R
R
I
VRAMP
V
CC5
5V
THERMAL
LIMIT
VRAMP5
I
TIMER
OVERVOLTAGE
LIMIT
C
C
VRAMP5
GND
V
REF5
V
CC5
TIMER5
EXTERNAL
DISABLE
R
TIMER5
PU5
5V
ARD5
AUTORETRY
DISABLE
8
12V/5V Hot-Plug Switch
Once the device has been enabled, there is a delay
(t ) until conduction begins from V (V ) to
internal current source, I
, begins to charge the
VRAMP
external capacitor, C , connected to VRAMP12
POND
CC12
CC5
VRAMP_
LOAD12 (LOAD5). This delay is the time required for
the charge pump to bring the gate voltage of the cor-
responding power MOSFET above its threshold level.
Once the gate is above the threshold level, conduction
begins and the output voltage begins ramping.
(VRAMP5). The amplifier controls the gate of the corre-
sponding power MOSFET so that the LOAD12 (LOAD5)
output voltage divided by two tracks the rising voltage
level of C
. The output voltage continues to ramp
VRAMP_
until it reaches either the input V
(V
) level
CC12
CC5
or the overvoltage clamp limits. The equation for the
output-voltage ramp function is:
Automatic-Enable Mode
When V
(V
) exceeds V
(V
), the gate
CC12
CC5
UR12
UR5
dV
/dt = 2 x (I
/C
) for +12V circuit
LOAD
VRAMP VRAMP12
holding the TIMER12 (TIMER5) node low is released. The
internal current source brings the node to a level greater
than V , enabling the device.
dV
/dt = 2.3332 x (I
/C
) for +5V circuit
LOAD
VRAMP VRAMP5
ON
Thermal Shutdown
The device enters a thermal shutdown state when
the temperature of the corresponding power MOSFET
Delayed Automatic-Enable Mode
(V ) exceeds V (V ), the gate
When V
CC12
CC5
UR12
UR5
holding the TIMER12 (TIMER5) node low is released. The
internal current source (I ) then begins charging
reaches or exceeds T
, approximately +135NC.
SHDN
TIMER
When T
is exceeded, the thermal-limiting cir-
SHDN
C
. When C
is charged to a level greater
TIMER_
TIMER_
cuitry disables the device using the enable circuitry.
Depending on the state of ARD12 (ARD5), the device
attempts to autoretry once the device has cooled, or it
latches off.
than V
(V
), the device turns on. The equation
REF12 REF5
for the delay time is:
t
= (C
x V )/I
REF12 TIMER
DELAY
TIMER12
t
= (C
x V )/I
REF5 TIMER
DELAY
TIMER5
Autoretry
If ARD12 (ARD5) is unconnected or connected high, the
device continually monitors the temperature once it has
entered thermal shutdown. If the junction temperature
Enable/Disable Mode
A logic gate or open-collector device can be connected
to TIMER12 (TIMER5) to enable or disable the device.
When TIMER12 (TIMER5) is held low, the device is dis-
abled. When an open-collector device is used to drive
TIMER12 (TIMER5), the device is enabled when the open
collector is in its high-impedance state by the internal
current source bringing the TIMER12 (TIMER5) node
high. TIMER12 (TIMER5) is also compatible with most
logic families if the output high voltage level of the gate
falls below approximately +95NC (T
- T ), the
HYS
SHDN
corresponding power MOSFET is re-enabled. See the
Thermal Shutdown with Autoretry Enabled typical operat-
ing curves for details.
Latchoff
If ARD12 (ARD5) is pulled low and the device has
entered thermal shutdown, it does not attempt to turn
back on. The only way to turn the device back on is to
cycle the power to the device. When power is reapplied
exceeds the V
current.
level, and the gate can sink the I
ON
TIMER
Enable with Delay/Disable Mode
An open-collector device is connected in parallel with
. When the pin is held low, the device is dis-
to V
less than T
(V
SHDN
), the junction temperature needs to be
for the device to be enabled.
CC12 CC5
C
TIMER_
abled. When the open-collector driver is high imped-
ance, the internal current source begins to charge
Overvoltage Limit
The overvoltage-limiting clamp monitors the VRAMP12
(VRAMP5) level compared to an internal voltage ref-
erence. When the voltage on VRAMP12 (VRAMP5)
C
as in the delayed mode.
TIMER_
Output-Voltage Ramp
exceeds V
/2 (or V
OVC12
/2.3332), the gate volt-
OVC5
The voltage ramp circuit uses an operational ampli-
fier to control the gate bias of the corresponding
n-channel power MOSFET. When the timer/enable
age of the corresponding n-channel power MOSFET is
reduced, limiting the voltage on LOAD12 (LOAD5) to
V
(V
) even as V
(V
) increases. If the
OVC12 OVC5
CC12 CC5
circuit is disabled, a FET is used to keep C
VRAMP_
device is in overvoltage for an extended period of time,
the device could overheat and enter thermal shutdown.
This is caused by the power created by the voltage
discharged, which forces the output voltage to GND.
Once the enable/timer circuit has been enabled, an
9
12V/5V Hot-Plug Switch
drop across the corresponding power MOSFET and the
load current. See the Thermal Shutdown with Autoretry
Enabled typical operating curves for details.
Unused Pins
If only one side (5V or 12V) of the device is being used,
it is required that the unused V , AR, CTIMER, and
CC
VRAMP pins be connected to GND. Leaving these input
pins unconnected can result in interference of the proper
operation of the active portion of the device.
Applications Information
Exposed Pad
The exposed pad is also a heatsink for the device. The
exposed pad should be connected to a large trace or
plane capable of dissipating heat from the device.
LOAD and ILIM Connections
Small parasitic resistances in the bond wires of the LOAD
pins and in the traces connected to the LOAD pins can
result in a voltage offset while current is flowing. Since
Decoupling Capacitors
It is of utmost importance to properly bypass the device's
supply pins. A decoupling capacitor absorbs the energy
stored in the supply and board parasitic inductance
when the FET is turned off, thereby reducing the magni-
the voltage drop across RILIM is used to set the I
and
SCL
I
I
limits, this induced offset can increase the value of
OVL
SCL
and I
from the specified values for any given
OVL
R . To greatly reduce this offset, it is recommended
ILIM
that one of the LOAD pins have a dedicated connection
to ILIM though R , and not be used to pass the LOAD
tude of overshoot at V . This can be accomplished by
CC
ILIM
using a high-quality (low ESR, low ESL) ceramic capaci-
current (Figure 1). This would leave three LOAD pins to
pass I , which should be sufficient. Because there
tor connected directly between the V
and GND pins.
CC
LOAD
Any series resistance with this bypass capacitor lowers
its effectiveness and is not recommended. A minimum
0.5µF ceramic capacitor is required. However, depend-
ing on the parasitic inductances present in the end appli-
cation, a larger capacitor could be necessary.
is only a small amount of current passed from this lone
LOAD pin to ILIM, there is a negligible voltage offset
applied to the internal comparator. This method is the
best way to attain an accurate current limit for I
.
LOAD
Package Information
For the latest package outline information and land patterns,
go to www.maxim-ic.com/packages. Note that a “+”, “#”, or
“-” in the package code indicates RoHS status only. Package
drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
MAX34561
LOAD
LOAD
LOAD
LOAD
TO APPLICATION
PACKAGE
TYPE
PACKAGE
CODE
OUTLINE
NO.
LAND
PATTERN NO.
R
ILIM
24 TQFN-EP
T2444+4
21-0139
90-0022
ILIM
Figure 1. LOAD and ILIM Connections
10
12V/5V Hot-Plug Switch
Revision History
REVISION REVISION
PAGES
DESCRIPTION
CHANGED
NUMBER
DATE
0
11/10
Initial release
—
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
11
©
2010 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
相关型号：
MAX3456EETE+
Line Transceiver, 1 Func, 1 Driver, 1 Rcvr, BICMOS, 3 X 3 MM, 0.80 MM HEIGHT, MO-220WEED-2, TQFN-16
MAXIM
MAX3456EETE+T
Line Transceiver, 1 Func, 1 Driver, 1 Rcvr, BICMOS, 3 X 3 MM, 0.80 MM HEIGHT, MO-220WEED-2, TQFN-16
MAXIM
MAX3456EETE-T
Line Transceiver, 1 Func, 1 Driver, 1 Rcvr, BICMOS, 3 X 3 MM, 0.80 MM HEIGHT, MO-220WEED-2, TQFN-16
MAXIM
MAX3456EEUD-T
Line Transceiver, 1 Func, 1 Driver, 1 Rcvr, BICMOS, PDSO14, 4.40 MM, MO-153AB-1, TSSOP-14
MAXIM
©2020 ICPDF网 联系我们和版权申明